technologyComment of gold mine operation and refining (SE): OPEN PIT MINING: The ore is mined in four steps: drilling, blasting, loading and hauling. In the case of a surface mine, a pattern of holes is drilled in the pit and filled with explosives. The explosives are detonated in order to break up the ground so large shovels or front-end loaders can load it into haul trucks. ORE AND WASTE HAULAGE: The haul trucks transport the ore to various areas for processing. The grade and type of ore determine the processing method used. Higher-grade ores are taken to a mill. Lower grade ores are taken to leach pads. Some ores may be stockpiled for later processing. HEAP LEACHING: The ore is crushed or placed directly on lined leach pads where a dilute cyanide solution is applied to the surface of the heap. The solution percolates down through the ore, where it leaches the gold and flows to a central collection location. The solution is recovered in this closed system. The pregnant leach solution is fed to electrowinning cells and undergoes the same steps as described below from Electro-winning. ORE PROCESSING: Milling: The ore is fed into a series of grinding mills where steel balls grind the ore to a fine slurry or powder. Oxidization and leaching: Some types of ore require further processing before gold is recovered. In this case, the slurry is pressure-oxidized in an autoclave before going to the leaching tanks or a dry powder is fed through a roaster in which it is oxidized using heat before being sent to the leaching tanks as a slurry. The slurry is thickened and runs through a series of leaching tanks. The gold in the slurry adheres to carbon in the tanks. Stripping: The carbon is then moved into a stripping vessel where the gold is removed from the carbon by pumping a hot caustic solution through the carbon. The carbon is later recycled. Electro-winning: The gold-bearing solution is pumped through electro-winning cells or through a zinc precipitation circuit where the gold is recovered from the solution. Smelting: The gold is then melted in a furnace at about 1’064°C and poured into moulds, creating doré bars. Doré bars are unrefined gold bullion bars containing between 60% and 95% gold. References: Newmont (2004) How gold is mined. Newmont. Retrieved from http://www.newmont.com/en/gold/howmined/index.asp technologyComment of primary lead production from concentrate (GLO): There are two basic pyrometallurgical processes available for the production of lead from lead or mixed lead-zinc-sulphide concentrates: sinter oxidation / blast furnace reduction route or Direct Smelting Reduction Processes. Both processes are followed by a refining step to produce the final product with the required purity, and may also be used for concentrates mixed with secondary raw materials. SINTER OXIDATION / BLAST FURNACE REDUCTION: The sinter oxidation / blast furnace reduction involves two steps: 1) A sintering oxidative roast to remove sulphur with production of PbO; and 2) Blast furnace reduction of the sinter product. The objective of sintering lead concentrates is to remove as much sulphur as possible from the galena and the accompanying iron, zinc, and copper sulphides, while producing lump agglomerate with appropriate properties for subsequent reduction in the blast furnace (a type of a shaft furnace). As raw material feed, lead concentrates are blended with recycled sinter fines, secondary material and other process materials and pelletised in rotating drums. Pellets are fed onto sinter machine and ignited. The burning pellets are conveyed over a series of wind-boxes through which air is blown. Sulphur is oxidised to sulphur dioxide and the reaction generates enough heat to fuse and agglomerate the pellets. Sinter is charged to the blast furnace with metallurgical coke. Air and/or oxygen enriched air is injected and reacts with the coke to produce carbon monoxide. This generates sufficient heat to melt the charge. The gangue content of the furnace charge combines with the added fluxes or reagents to form a slag. For smelting bulk lead-zinc-concentrates and secondary material, frequently the Imperial Smelting Furnace is used. Here, hot sinter and pre-heated coke as well as hot briquettes are charged. Hot air is injected. The reduction of the metal oxides not only produces lead and slag but also zinc, which is volatile at the furnace operating temperature and passes out of the ISF with the furnace off-gases. The gases also contain some cadmium and lead. The furnace gases pass through a splash condenser in which a shower of molten lead quenches them and the metals are absorbed into the liquid lead, the zinc is refined by distillation. DIRECT SMELTING REDUCTION: The Direct Smelting Reduction Process does not carry out the sintering stage separately. Lead sulphide concentrates and secondary materials are charged directly to a furnace and are then melted and oxidised. Sulphur dioxide is formed and is collected, cleaned and converted to sulphuric acid. Carbon (coke or gas) and fluxing agents are added to the molten charge and lead oxide is reduced to lead, a slag is formed. Some zinc and cadmium are “fumed” off in the furnace, their oxides are captured in the abatement plant and recovered. Several processes are used for direct smelting of lead concentrates and some secondary material to produce crude lead and slag. Bath smelting processes are used: the ISA Smelt/Ausmelt furnaces (sometimes in combination with blast furnaces), Kaldo (TBRC) and QSL integrated processes are used in EU and Worldwide. The Kivcet integrated process is also used and is a flash smelting process. The ISA Smelt/Ausmelt furnaces and the QSL take moist, pelletised feed and the Kaldo and Kivcet use dried feed. REFINING: Lead bullion may contain varying amounts of copper, silver, bismuth, antimony, arsenic and tin. Lead recovered from secondary sources may contain similar impurities, but generally antimony and calcium dominate. There are two methods of refining crude lead: electrolytic refining and pyrometallurgical refining. Electrolytic refining uses anodes of de-copperised lead bullion and starter cathodes of pure lead. This is a high-cost process and is used infrequently. A pyrometallurgical refinery consists of a series of kettles, which are indirectly heated by oil or gas. Over a series of separation processes impurities and metal values are separated from the lead bouillon. Overall waste: The production of metals is related to the generation of several by-products, residues and wastes, which are also listed in the European Waste Catalogue (Council Decision 94/3/EEC). The ISF or direct smelting furnaces also are significant sources of solid slag. This slag has been subjected to high temperatures and generally contains low levels of leachable metals, consequently it may be used in construction. Solid residues also arise as the result of the treatment of liquid effluents. The main waste stream is gypsum waste (CaSO4) and metal hydroxides that are produced at the wastewater neutralisation plant. These wastes are considered to be a cross-media effect of these treatment techniques but many are recycled to pyrometallurgical process to recover the metals. Dust or sludge from the treatment of gases are used as raw materials for the production of other metals such as Ge, Ga, In and As, etc or can be returned to the smelter or into the leach circuit for the recovery of lead and zinc. Hg/Se residues arise at the pre-treatment of mercury or selenium streams from the gas cleaning stage. This solid waste stream amounts to approximately 40 - 120 t/y in a typical plant. Hg and Se can be recovered from these residues depending on the market for these metals. Overall emissions: The main emissions to air from zinc and lead production are sulphur dioxide, other sulphur compounds and acid mists; nitrogen oxides and other nitrogen compounds, metals and their compounds; dust; VOC and dioxins. Other pollutants are considered to be of negligible importance for the industry, partly because they are not present in the production process and partly because they are immediately neutralised (e.g. chlorine) or occur in very low concentrations. Emissions are to a large extent bound to dust (except cadmium, arsenic and mercury that can be present in the vapour phase). Metals and their compounds and materials in suspension are the main pollutants emitted to water. The metals concerned are Zn, Cd, Pb, Hg, Se, Cu, Ni, As, Co and Cr. Other significant substances are fluorides, chlorides and sulphates. Wastewater from the gas cleaning of the smelter and fluid-bed roasting stages are the most important sources. References: Sutherland C. A., Milner E. F., Kerby R. C., Teindl H. and Melin A. (1997) Lead. In: Ullmann's encyclopedia of industrial chemistry (ed. Anonymous). 5th edition on CD-ROM Edition. Wiley & Sons, London. IPPC (2001) Integrated Pollution Prevention and Control (IPPC); Reference Document on Best Available Techniques in the Non Ferrous Metals Industries. European Commission. Retrieved from http://www.jrc.es/pub/english.cgi/ 0/733169 technologyComment of primary zinc production from concentrate (RoW): The technological representativeness of this dataset is considered to be high as smelting methods for zinc are consistent in all regions. Refined zinc produced pyro-metallurgically represents less than 5% of global zinc production and less than 2% of this dataset. Electrometallurgical Smelting The main unit processes for electrometallurgical zinc smelting are roasting, leaching, purification, electrolysis, and melting. In both electrometallurgical and pyro-metallurgical zinc production routes, the first step is to remove the sulfur from the concentrate. Roasting or sintering achieves this. The concentrate is heated in a furnace with operating temperature above 900 °C (exothermic, autogenous process) to convert the zinc sulfide to calcine (zinc oxide). Simultaneously, sulfur reacts with oxygen to produce sulfur dioxide, which is subsequently converted to sulfuric acid in acid plants, usually located with zinc-smelting facilities. During the leaching process, the calcine is dissolved in dilute sulfuric acid solution (re-circulated back from the electrolysis cells) to produce aqueous zinc sulfate solution. The iron impurities dissolve as well and are precipitated out as jarosite or goethite in the presence of calcine and possibly ammonia. Jarosite and goethite are usually disposed of in tailing ponds. Adding zinc dust to the zinc sulfate solution facilitates purification. The purification of leachate leads to precipitation of cadmium, copper, and cobalt as metals. In electrolysis, the purified solution is electrolyzed between lead alloy anodes and aluminum cathodes. The high-purity zinc deposited on aluminum cathodes is stripped off, dried, melted, and cast into SHG zinc ingots (99.99 % zinc). Pyro-metallurgical Smelting The pyro-metallurgical smelting process is based on the reduction of zinc and lead oxides into metal with carbon in an imperial smelting furnace. The sinter, along with pre-heated coke, is charged from the top of the furnace and injected from below with pre-heated air. This ensures that temperature in the center of the furnace remains in the range of 1000-1500 °C. The coke is converted to carbon monoxide, and zinc and lead oxides are reduced to metallic zinc and lead. The liquid lead bullion is collected at the bottom of the furnace along with other metal impurities (copper, silver, and gold). Zinc in vapor form is collected from the top of the furnace along with other gases. Zinc vapor is then condensed into liquid zinc. The lead and cadmium impurities in zinc bullion are removed through a distillation process. The imperial smelting process is an energy-intensive process and produces zinc of lower purity than the electrometallurgical process. technologyComment of treatment of electronics scrap, metals recovery in copper smelter (SE, RoW): Conversion of Copper in a Kaldo Converter and treatment in converter aisle. technologyComment of treatment of scrap lead acid battery, remelting (RoW): The referred operation uses a shaft furnace with post combustion, which is the usual technology for secondary smelters. technologyComment of treatment of scrap lead acid battery, remelting (RER): The referred operation uses a shaft furnace with post combustion, which is the usual technology for secondary smelters. Typically this technology produces 5000 t / a sulphuric acid (15% concentration), 25’000 t lead bullion (98% Pb), 1200 t / a slags (1% Pb) and 3000 t / a raw lead matte (10% Pb) to be shipped to primary smelters. Overall Pb yield is typically 98.8% at the plant level and 99.8% after reworking the matte. The operation treats junk batteries and plates but also lead cable sheathing, drosses and sludges, leaded glass and balancing weights. From this feed it manufactures mainly antimonial lead up to 10% Sb, calcium-aluminium lead alloys with or without tin and soft lead with low and high copper content. All these products are the result of a refining and alloying step to meet the compliance with the designations desired. The following by products are reused in the process: fine dust, slag, and sulfuric acid. References: Quirijnen L. (1999) How to implement efficient local lead-acid battery recycling. In: Journal of Power Sources, 78(1-2), pp. 267-269.
Was sind Dioxine und Furane? Dioxine und Furane sind die Kurzbezeichnungen für jeweils eine Gruppe von halogenierten, (häufig chlorierten (P C DD/F), aber auch fluorierten P F DD/F) und bromierten (P Br DD/F), tricyclischen aromatischen Verbindungen, bei denen zwei Benzolringe über eine Sauerstoffbrücke verbunden sind. An den Positionen 1 bis 9 können Halogenatome (z.B. Chlor) gebunden sein. Die nachfolgenden Ausführungen beziehen sich auf die Polychlorierten Dibenzo-p-Dioxine und –Furane. Die Gruppe der polychlorierten Dioxine besteht aus 75 verschiedenen Verbindungen (Kongenere), die sich in Anzahl und Anordnung der verschiedenen Chloratome im Molekül unterscheiden. Bei den polychlorierten Furanen sind 135 verschiedene Kongenere möglich. Die Dioxinanalytik konzentriert sich auf 17 Verbindungen, die in 2,3,7,8‑Stellung Chloratome tragen und deshalb als besonders toxisch eingestuft werden. Die giftigsten Kongenere sind das 2,3,7,8‑Tetrachlordibenzodioxin, das maßgeblich beim Unfall in Seveso (1976) freigesetzt wurde. Wie entstehen Dioxine und Furane? Dioxine und Furane wurden von der chemischen Industrie nie gezielt hergestellt und haben keinerlei praktische Verwendung. Sie sind Nebenprodukte, die ungewollt bei allen Verbrennungsprozessen in Anwesenheit von Chlor und organischen Kohlenstoff entstehen können. Dioxine und Furane entstehen in einem Temperaturbereich zwischen 300°C und 900°C. Was sind die Hauptquellen für die Dioxine in der Umwelt? Die Hauptquellen für den Eintrag von Dioxinen und Furanen in die Umwelt sind: Thermische Prozesse: Bildung im Rahmen der unvollständigen Verbrennung (Abfallverbrennung, Metallerzeugung, Metallrecycling, Hausbrand, Brände von PVC, Transformatoren (PCB), bromierte Flammschutzmittel). Industrielle Quellen Prozesse und Produkte der Halogenchemie, Chlorphenolchemie: Insektizide, Herbizide, PCB‑Herstellung, Verunreinigungen in chlororganischen Verbindungen, Zellstoff‑ und Papierindustrie, Textilreinigung, Flammschutzmittel. Sekundäre Quellen Abgelagerte oder abgeschiedene Dioxine aus Deponien, Klärschlämmen, Sickerwässern, Altölen, Komposten, Holzschutzmitteln in Innenräumen. Für den Eintrag in die Luft waren früher Metallgewinnung und die Abfall-Verbrennungsanlagen die wichtigsten Quellen. Dank anspruchsvoller Grenzwerte und Filtertechniken konnte der Dioxinausstoß aus den Abfall-Verbrennungsanlagen drastisch gesenkt werden. Natürliche Quellen Auch natürliche Prozesse, wie beispielsweise Wald- oder Steppenbrände, können zur Bildung von Dioxinen führen. Im Vergleich mit den anderen Quellen tragen natürliche Quellen nur in geringem Maß zur Dioxinbelastung der Umwelt bei. Was sind poychlorierte Biphenyle (PCB) bzw. dioxinähnliche PCB? Poychlorierte Biphenyle (PCB) sind chlorierte Kohlenwasserstoffe. Am Grundgerüst eines Biphenyls sind hier, je nach Verbindung, eine unterschiedliche Anzahl von Wasserstoffatomen durch Chloratome substituiert. Theoretisch gibt es 209 mögliche Verbindungen (Kongenere) , von denen 12 Kongenere als dioxinähnliche- PCB oder dl-PCB bezeichnet werden. Diese weisen eine den Dioxinen und Furanen ähnliche räumliche und elektronische Struktur auf. Man unterscheidet bei den dl-PCB „non-ortho Kongenere“ PCB 77, PCB 81, PCB126, PCB 169) und „mono-ortho Kongenere“ (PCB 105, PCB 114, PCB 118, PCB 123, PCB 156, PCB 157, PCB 167, PCB 189). Die giftigste dioxinähnliche Wirkung zeigt das 3,3',4, 4',5-Pentachlorobiphenyl (PCB 126). Polychlorierte Biphenyle sind in Deutschland seit 1989 verboten, und müssen als Sonderabfall in der Regel per Hochtemperaturverbrennung entsorgt werden. Polychlorierte Biphenyle (PCB) Wie entstehen poychlorierte Biphenyle (PCB)? PCB wurden bis in die 1980´er Jahre als bedeutende technische Chemikalie produziert und vor allem in Transformatoren, elektrischen Kondensatoren, in Hydraulikanlagen als Hydraulikflüssigkeit, sowie als Weichmacher in Lacken, Dichtungsmassen, Isoliermitteln und Kunststoffen verwendet. In diesen Gemischen sind unterschiedlich große Anteile dioxinähnlicher PCB enthalten. PCB entstehen auch als Nebenprodukt bei der Herstellung von Silikonkautschuk mit chlorhaltigen Vernetzern. Wie werden Dioxine, Furane und PCB vom menschlichen Organismus aufgenommen? Die umweltbedingte Belastung des Menschen mit Dioxinen, Furanen und dioxinähnlichen PCB erfolgt im Wesentlichen über die Nahrung, insbesondere über fetthaltige tierische Lebensmittel wie Fisch, Fleisch, Milch und Milchprodukte. Nur ein geringer Prozentsatz (<5%) wird über die Atemluft und das Wasser aufgenommen. Welche Auswirkungen haben Dioxine, Furane und dl-PCB auf die Gesundheit? Dioxine, Furane und dioxinähnliche PCB sind sehr langlebige Verbindungen. Sie reichern sich im Fettgewebe des Menschen an und werden je nach Kongener mit Halbwertszeiten zwischen einem Jahr und 13 Jahren nur sehr langsam abgebaut. Bei den toxischen Wirkungen der Dioxine, Furane und dioxinähnlichen PCB muss man akute Giftwirkungen, die nach Kontakt mit hohen Konzentrationen auftreten, und chronische Effekte, die durch niedrige Konzentrationen hervorgerufen werden können unterscheiden. Akute Wirkungen beim Menschen sind heutzutage nur nach Unfällen, Bränden oder bei beruflich belasteten Personen zu erwarten. Herausragendes Symptom verschiedener Vergiftungsunfälle in der chemischen Industrie bis etwa in die 1980iger Jahre war das Auftreten von Chlorakne. Weitere Symptome akuter Vergiftungen sind u. a. Erbrechen, Muskelschmerzen, Kopfschmerzen, Schlafstörungen sowie Magen-Darm-Beschwerden. Hinsichtlich chronischer Wirkungen ist vor allem die mögliche krebserzeugende Wirkung des 2,3,7,8-TCDD, des sogenannten „Seveso-Dioxin“, von Bedeutung. Beim Menschen sowie in Tierversuchen ließen sich außerdem Störungen des Immunsystems sowie neurotoxische, reproduktionstoxische und fruchtschädigende Wirkungen feststellen. Daneben weisen Studien auf Herz-Kreislauf-Erkrankungen, Leberstörungen sowie auf ein erhöhtes Diabetes-Risiko hin. Diese Effekte sind aber unter üblichen Umweltbedingungen von eher geringer Bedeutung. Insgesamt ist die Belastung des Menschen durch Dioxine, Furane und dioxinähnliche PCB seit geraumer Zeit rückläufig. Trotz dieser starken Rückläufigkeit nehmen nach einer aktuellen Auswertung des Bundesinstitutes für Risikobewertung nach wie vor immer noch große Teile der Bevölkerung mehr Dioxine, Furane und dioxinähnliche PCB zu sich als aus gesundheitlicher Sicht empfehlenswert wäre. Die tägliche Aufnahme von Dioxinen, Furanen und dioxinähnlichen PCB über Lebensmittel in Deutschland betrug laut Umweltbundesamt (2018) nach Analysenergebnissen aus den Jahren 2000 bis 2003 im Mittel ca. zwei pg WHO-PCDD/F-PCB-TEQ pro kg Körpergewicht und Tag. Die Europäische Lebensmittelsicherheitsbehörde (EFSA) hat im November 2018 eine neue tolerierbare wöchentliche Aufnahmemenge (TWI) für PCDD/F und dioxinähnliche PCBs abgeleitet. Diese umfassende Risikobewertung basiert auf aktuellen wissenschaftlichen Studien und Erkenntnissen. Dabei wurde der TWI-Wert von 14 pg WHO-PCDD/F-PCB-TEQ/kg Körpergewicht und Woche auf 2 pg WHO- PCDD/F-PCB-TEQ/kg Körpergewicht und Woche abgesenkt. Bei lebenslanger Aufnahme von Dioxinen und dioxinähnlichen PCBs bis zu einer Menge von 2 pg WHO- PCDD/F-PCB-TEQ/kg Körpergewicht und Woche bzw. umgerechnet 0,29 WHO- PCDD/F-PCB-TEQ/kg Körpergewicht und Tag ist somit mit keinen negativen Auswirkungen für die Menschen zu rechnen. Ein Großteil der erwachsenen Bevölkerung überschreitet somit die vorgegebene tolerierbare Tagesdosis bereits durch die normalerweise vorhandene Kontamination der Lebensmittel. Abweichende Ernährungsgewohnheiten können zu noch höheren Belastungen führen. Auch Kinder haben im Verhältnis zu ihrem Körpergewicht höhere Aufnahmen. Hieraus lässt sich folgern, dass die Belastung des Menschen mit Dioxinen, Furanen und dioxinähnlichen PCB nach wie vor zu hoch ist. Die Belastung der Menschen und der Umwelt muss daher noch weiter gesenkt werden. Frauenmilch ist ein Indikator für die Belastung des Menschen mit Dioxinen, Furanen und dioxinähnlichen PCB, da diese sehr fettreich ist, und sich daher sehr gut dazu eignet, die Rückstände im menschlichen Fettgewebe anzuzeigen. Langjährige Untersuchungsreihen haben gezeigt, dass sich der Erfolg der Maßnahmen zur Reduzierung der Umweltbelastung auch in der Frauenmilch widerspiegelt. Der durchschnittliche PCDD/F-Gehalt von Frauenmilch in Deutschland ist laut Bundesinstitut für Risikobewertung (BfR) im Zeitraum von 1986 bis 2009 von 35,7 auf 6,3 pg/g Milchfett gesunken. Daten zu dioxinähnlichen PCB liegen für den Zeitraum von 2001 bis 2009 vor, die ebenfalls sinkende Gehalte in Frauenmilch belegen. Im Jahr 2009 betrug der mittlere Gehalt für die Summe von PCDD/F und dioxinähnlichen PCB 13,8 pg WHO-TEQ/g Milchfett. Trotzdem sind Kinder gerade in der intensiven Entwicklungsphase im Mutterleib oder als Säuglinge immer noch zu hohen Belastungen ausgesetzt, weil die Schadstoffe über die Plazenta und die Muttermilch an die nächste Generation weitergegeben werden. Es wird jedoch keinesfalls vom Stillen abgeraten, da die bekannten positiven Auswirkungen des Stillens überwiegen. Welche Maßnahmen wurden ergriffen, um die Dioxinbelastung zu senken? Die Umweltbelastung, aber auch die Belastung von Lebensmitteln und des Menschen durch Dioxine sind in Deutschland seit Ende der 80er Jahre deutlich zurückgegangen. Grund dafür war eine Fülle technischer und rechtlicher Maßnahmen vor allem in der Chemikalienproduktion und Emissionsbeschränkungen bei Verbrennungsprozessen. Wie kann die Toxizität einer mit Dioxinen, Furanen und PCB belasteten Probe beurteilt werden? Für die Beurteilung der von Dioxinen, Furanen und dioxinähnlichen PCB verursachten Toxizität einer Probe werden nach Weltgesundheitsorganisation (WHO) 17 Kongenere der Dioxine und Furane und 12 Verbindungen aus der Gruppe der dioxinähnlichen PCB analytisch bestimmt. Dioxine, Furane und dioxinähnliche PCB treten meist als Gemische einzelner Kongenere in unterschiedlichen Mengen auf. Die Beurteilung der Toxizität dieser 29 Kongenere erfolgt mit Hilfe von Toxizitätsäquivalenten (TEQ-Werte). Das System der Toxizitätsäquivalente trägt der unterschiedlichen Giftigkeit der Einzelverbindungen Rechnung. Um die Toxizität dieser Gemische einzustufen, wurden den einzelnen Dioxinen, Furanen und dioxinähnlichen PCB von der Weltgesundheitsorganisation im Jahre 2005 festgesetzte Toxizitätsäquivalentfaktoren (TEF) zugeordnet, die diese Verbindungen gemäß ihrer Toxizität einstufen. In 2024 wurden diese TEF von der WHO aktualisiert. Die Toxizität des giftigsten bekannten Dioxins (2,3,7,8-TCDD) wird mit 1 bewertet. Die anderen Dioxine, Furane und dioxinähnlichen PCB sind im Verhältnis zu 2,3,7,8-TCDD weniger giftig und erhalten deshalb Werte kleiner 1. Die toxische Wirkung der Dioxine, Furane und dioxinähnlichen PCB wird dann über die Multiplikation der Gehalte der Einzelverbindungen mit dem zugehörigen Faktor (TEF) als sogenanntes Toxizitätsäquivalent ( TEQ ) errechnet und addiert. Die Summe der Toxizitätsäquivalente der Einzelverbindungen, die in einer Probe bestimmt worden sind, ergibt die Gesamttoxizität der Probe (TEQ-Wert). Nicht-dioxinähnliche PCB werden anhand von 6 Leitsubstanzen (PCB 28, PCB 52, PCB 101, PCB 138, PCB 153, PCB 180) beurteilt. Da der Anteil dieser Kongenere in der Umwelt häufig 20 % von der Summe aller PCB beträgt, wird für eine einheitliche Beurteilung der Gesamt-PCB die Summe der 6 Leitsubstanzen mit dem Faktor 5 multipliziert. Wie werden Dioxine, Furane und PCB in der Außenluft gemessen? Dioxine, Furane und polychlorierte Biphenyle kommen in der Außenluft sowohl gasförmig als auch gebunden an Staubpartikel vor. Die PCDD/PCDF- und PCB-Konzentrationen, die mit der Luft eingeatmet werden, werden in der Luftkonzentrationsmessung ( Außenluftkonzentration ) erfasst. Die schwereren Partikel (Staub), die nicht in der Luft schweben und schnell zu Boden sinken, sowie der Niederschlag (Regen, Schnee) werden in der Depositionsmessung erfasst. Wie werden Luftkonzentrationsmessungen durchgeführt? Die Probenahme und Spurenanalytik von Dioxinen, Furanen und polychlorierten Biphenylen in der Außenluft ist wegen der geringen Konzentrationen sehr aufwendig. Eine große Luftmenge (ca. 1000 m³) wird über ein Filtersystem aus Polyurethanschäumen und einem Partikelfilter gesaugt. Der Probenahmezeitraum beträgt in der Regel einen Monat. Die Schadstoffe werden auf den Filtermedien abgeschieden. Nach Ablauf der Probenahmezeit werden die im Probenahmekopf enthaltenen Filtermedien im Labor zu einer Probe vereinigt und auf Dioxine, Furane und PCB untersucht. Die analytische Bestimmung erfolgt per Gaschromatographie / hochauflösender Massenspektrometrie (GC/HRMS). Wie werden Depositionsmessungen durchgeführt? Gerätschaften zur Depositionsprobenahme Depositionsprobenahme Die Probenahme der atmosphärischen Deposition (Staub, Regen, Schnee) erfolgt nach VDI-Richtlinie 4320 Blatt 5 als Gesamtdeposition. Am Messort werden mehrere Sammelgläser (in der Regel 6 Gläser) für 30 Tage aufgestellt. Nach Ablauf der Probenahmezeit wird der Inhalt der Gläser im Labor auf Dioxine, Furane und polychlorierte Biphenyle untersucht. Die analytische Bestimmung erfolgt per Gaschromatographie mit Massenspektrometrie-Kopplung. Am Messort werden mehrere Sammelgläser (in der Regel 3-6 Gläser) für 30 Tage aufgestellt. Nach Ablauf der Probenahmezeit wird der Inhalt der Gläser im Labor auf Dioxine, Furane und PCB untersucht. Die analytische Bestimmung erfolgt per hochauflösender Gaschromatographie / Massenspektrometrie. Warum werden verschiedene Probenahmeverfahren eingesetzt? Die Luftkonzentrationswerte an Dioxinen, Furanen und PCB spiegeln die Belastung der Luft wieder, die über die Atmung aufgenommen wird. Die PCDD/PCDF-und PCB-Depositionen stellen ein Maß die Belastung von Nahrungs- und Futterpflanzen dar. Anhand der Depositionswerte kann auch abgeschätzt werden, ob langfristig Bodenbelastungen zu befürchten sind. Wie werden PCDD/PCDF- und PCB –Luftkonzentrationen und –Depositionen beurteilt? Luftkonzentration: Für die Beurteilung der Luftkonzentration von Dioxinen, Furanen und dioxinähnlichen PCB hat der Länderausschuss für Immissionsschutz (21.09.2004), jetzt Bund/Länder-Arbeitsgemeinschaft Immissionsschutz (LAI), einen Zielwert (Jahresmittelwert) für die langfristige Luftreinhalteplanung empfohlen. Dieser LAI-Zielwert beträgt 150 fg WHO (PCDD/PCDF + dl-PCB) -TEQ/m³ . Ein Beurteilungsmaßstab für den PCB- Gesamtgehalt in der Außenluft existiert derzeit nicht. Als Vergleichsmaßstab zur Bewertung der PCB (PCB-Gesamtgehalt (28+52+101+153+138+180) x 5) kann der Sanierungszielwert für Innenräume von 300 ng/m³ näherungsweise herangezogen werden. Deposition: Für die Beurteilung der Deposition von PCDD/F und dioxinähnlichen PCB hat die LAI einen Zielwert (Jahresmittelwert) für die langfristige Luftreinhalteplanung von 4 pg WHO (PCDD/PCDF + dl-PCB) -TEQ/(m²x d) festgelegt. Der Immissionswert der TA-Luft (2021), welcher im Rahmen der Genehmigung und Überwachung von Anlagen herangezogen werden kann und als Jahresmittelwert festgesetzt wurde, beträgt 9 pg WHO (PCDD/PCDF + dl-PCB) -TEQ/(m²x d). Warum werden Monats- und Jahresmittelwerte ermittelt? Für die Beurteilung von Messwerten wird immer der Jahresmittelwert zugrunde gelegt. Die Monatsmittelwerte von Immissionsmessungen können starken Schwankungen unterliegen. Neben den Schwankungen des monatlichen Eintrages in die Atmosphäre haben Temperatur, Windrichtung und Windgeschwindigkeit einen starken Einfluss auf die Luftkonzentration und Deposition. Bei organischen Komponenten wie den Dioxinen, Furanen und PCB ist ein jahreszeitlicher Temperaturgang zu beobachten. PCB-Luftkonzentrationen sind in den Sommermonaten deutlich höher als in den Wintermonaten. Bei Dioxinen und Furanen liegt ein entgegengesetzter Jahresgang vor. Zur Beurteilung der Schadstoffbelastung der Luft mit Dioxinen Furanen und polychlorierten Biphenylen werden daher Jahresmittelwerte gebildet, die die durchschnittliche Belastung widerspiegeln. Wie hoch ist die Dioxin, Furan und PCB- Konzentration in NRW, werden die Zielwerte des LAI erreicht? Die Jahresmittelwerte für die Summe aus PCDD/PCDF- und dl-PCB-Luftkonzentration lagen in NRW in den letzten Jahren zwischen 10 und 20 fg WHO-TEQ/m³ und somit deutlich unter dem LAI-Zielwert. Die PCB-Gesamtkonzentration in der Außenluft von NRW liegt im langjährigen Mittel bei 0,5 – 1,5 ng PCB/m³. Die Jahresmittelwerte für die Summe von Dioxinen, Furanen und dl-PCB in der Deposition lagen in NRW in den letzten Jahren an Hintergrundmessstationen bei ca. 2 pg WHO-TEQ/(m² x d) und an den übrigen Messstellen im Umfeld von Wohnbebauung zwischen 4 und 8 pg WHO-TEQ/(m² x d). Die Messwerte liegen unterhalb des Immissionswertes der TA-Luft (2021), welcher im Rahmen der Genehmigung und Überwachung von Anlagen herangezogen wird und oberhalb des langfristigen Zielwertes des LAI für die Luftreinhalteplanung. . aktuelle Werte Wie gelangen Dioxine, Furane und polychlorierte Biphenyle in Böden? Der Eintrag von Dioxinen und PCB in Böden erfolgt hauptsächlich über Depositionen aus der Luft. Aber auch durch das Ausbringen von Klärschlamm können Dioxine und PCB in Böden eingebracht werden. Bei Überschwemmungsereignissen können schadstoffhaltige Sedimente auf Flächen im Bereich von Überschwemmungsgebieten verlagert werden, wodurch ebenfalls erhebliche PCB- und Dioxinmengen in die betroffenen Böden gelangen können. Da Dioxine und PCB in der Natur kaum abgebaut werden und diese Stoffe vor allem in humusreichen Böden gebunden werden, kann es zu einer langfristigen Anreicherung kommen, auch wenn nur geringe Einträge stattfinden. Wie hoch ist die Konzentration an Dioxinen, Furane und polychlorierte Biphenyle in Böden in NRW? Aufgrund des Eintrags aus der Luft sind Dioxine, Furane und PCB prinzipiell in allen Böden nachweisbar. In ländlichen Gebieten werden üblicherweise geringere Gehalte als in Ballungsräumen nachgewiesen. So liegen die Gehalte an Dioxinen und Furanen in Gärten in ländlichen Gebieten um 5 ng TEQ/kg Boden, in Gärten in der Umgebung von Ballungsräumen und in Verdichtungsgebieten im Bereich von 10 – 15 ng TEQ/kg Boden. Die PCB-Gehalte (Summe der 6 PCB) in Gärten liegen in ländlichen Gebieten um 7 µg/kg Boden, in der Umgebung von Ballungsräumen und in Verdichtungsgebieten um 20 µg/kg und im Ballungskern um 25 µg/kg. Erfahrungswerte für üblicherweise vorzufindende Konzentrationen an dl-PCB in Böden liegen noch nicht vor. Höhere Gehalte weisen Böden in den Überschwemmungsgebieten einiger Flüsse in NRW auf. So wurden beispielsweise in den Überschwemmungsgebieten von Rhein, Ruhr und Wupper PCDD/F-Gehalte von 40 – 65 ng TEQ/kg, PCB-Gehalte von 5 – 260 µg/kg und dl-PCB-Gehalte von 12 – 16 ng TEQ/kg nachgewiesen. Wie sind die Konzentration an Dioxinen, Furane und polychlorierte Biphenyle in Böden zu beurteilen? Die Gehalte von Schadstoffen in Böden sind in Abhängigkeit von der jeweiligen Nutzung unterschiedlich zu bewerten. So wird in der Bundes-Bodenschutz- und Altlastenverordnung beispielsweise für Böden unter Grünlandnutzung bei PCB ein Maßnahmenwert (Summe der 6 PCB) von 0,2 mg/kg genannt, für Dioxine und Furane ein Prüfwert von 15 ng WHO-TEQ/kg. Ist dieser Wert überschritten, müssen entsprechende Maßnahmen eingeleitet werden. Für Dioxine gibt es für den Wirkungspfad Boden-Pflanze hingegen keinen rechtsgültigen Beurteilungswert. Zum Schutz vor Belastungen, die den Menschen „direkt“ über den Boden – beispielsweise wenn spielende Kinder Bodenmaterial über den Mund aufnehmen oder einatmen – treffen können, sind abgestufte Maßnahmenwerte für Kinderspielflächen, Wohngebiete, Park- und Freizeitanlagen oder Industrie- und Gewerbeflächen abgeleitet worden. Für PCB (Summe der 6 PCB) sind für diese Nutzungskategorien hingegen „nur“ Prüfwerte festgelegt worden, bei deren Überschreitungen im Einzelfall weitere Untersuchungen und Prüfungen erfolgen müssen. Kinderspiel - flächen Wohn- gebiete Park-und Freizeit- anlagen Industrie-und Gewerbe- grundstücke Maßnahmenwert Dioxine/Furane [ng I-TEq/kg Boden] [1] 100 1.000 1.000 10.000 Prüfwert PCB 6 [2] (PCB 28,52,101,138,153,180) [µg/kg Boden] 0,4 0,8 2 40 Wie hoch ist die Konzentration an Dioxinen und PCB in Pflanzen und Furane? Dioxine und Furane finden sich in Spurenmengen überall in der Umwelt. Diese organischen Substanzen werden von Pflanzen in der Regel kaum über ihre Wurzeln aufgenommen, können sich aber u.a. in der wachshaltigen Oberschicht von Pflanzen anreichern, wenn sie über die Luft oder durch äußerliche Verschmutzungen mit belastetem Bodenmaterial auf die Pflanzenoberfläche gelangen. Der Mensch nimmt diese Giftstoffe mit dem Verzehr von Nahrungspflanzen in den Körper auf. Zahlreiche Untersuchungen haben ergeben, dass Grünkohl auf Grund seiner guten _______________________________________ [1] Summe der 2,3,7,8-TCDD-Toxizitätsäquivalente nach NATO/CCMS [1] Soweit PCB-Gesamtgehalte bestimmt werden, sind die ermittelten Messwerte durch den Faktor 5 zu dividieren. Anströmbarkeit, seiner großen Blattoberfläche und seiner ausgeprägten Wachsschicht als guter Sammler, insbesondere von Dioxinen und Furanen und anderen organischen Verbindungen geeignet ist. Das Landesamt für Natur, Umwelt und Verbraucherschutz betreibt in NRW 14 Messstellen im Rahmen des Wirkungsdauermessprogramms sowohl in Ballungsgebieten wie auch in ländlichen Regionen. Dort wird u.a. Grünkohl jährlich zwischen August und November nach Standardverfahren in Pflanzbehältern exponiert (Richtlinie VDI 3957 Blatt 4) und auf Schadstoffgehalte untersucht. Aus den ermittelten Werten der jeweils letzten 10 Jahre werden nach Richtlinie VDI 3857 Blatt 2 die sogenannten Orientierungswerte für den maximalen Hintergrundgehalt (OmH) berechnet. Messwerte, die den OmH abzüglich der Standardunsicherheit des Verfahrens überschreiten, werden als Hinweis auf eine vorliegende Immissionsbelastung durch die untersuchte Substanz gewertet (Richtlinie VDI 3857 Blatt 2). Aktuelle OmH können dem LANUV-Fachbericht 114 (LINK) entnommen werden. Für PCDD/F in pflanzlichen Lebensmitteln gibt es einen EU-Auslösewert von 0,30 ng TEQ/kg FM (Empfehlung der EU-Kommission vom 11.09.2014 zur Änderung des Anhangs der Empfehlung 2013/711/EU zur Reduzierung des Anteils von Dioxinen, Furanen und polychlorierten Biphenylen in Futtermitteln und Lebensmitteln). Dieser Auslösewert ist nicht toxikologisch abgeleitet. Er dient als Anregung zur Ursachenfindung von Quellen, mit dem Ziel, diese zu identifizieren und Maßnahmen zur Reduzierung oder Beseitigung der Quellen zu veranlassen. Auch für die dioxinähnlichen PCB (dl-PCB) ermittelt das LANUV jährlich neue Orientierungswerte für den maximalen Hintergrundgehalt (OmH) in Nahrungspflanzen; insbesondere Grünkohl (nach Richtlinie VDI 3857 Blatt 2). Messwerte, die den OmH abzüglich der Standardunsicherheit des Verfahrens überschreiten, werden als Hinweis auf eine vorliegende Immissionsbelastung durch die untersuchte Substanz gewertet (Richtlinie VDI 3857 Blatt 2). Aktuelle OmH können dem LANUV-Fachbericht 114 (LINK) entnommen werden Für dl-PCB in pflanzlichen Lebensmitteln gibt es zudem einen EU-Auslösewert von 0,10 ng TEQ/kg FM (Empfehlung der EU-Kommission vom 11.09.2014 zur Änderung des Anhangs der Empfehlung 2013/711/EU zur Reduzierung des Anteils von Dioxinen, Furanen und PCB in Futtermitteln und Lebensmitteln). Dieser Auslösewert ist nicht toxikologisch abgeleitet. Er dient als Anregung zur Ursachenfindung von Quellen, mit dem Ziel, diese zu identifizieren und Maßnahmen zur Reduzierung oder Beseitigung der Quellen zu veranlassen. Wie sind die Konzentrationen an Dioxinen und dl-PCB in Pflanzen und Furane zu beurteilen? Falls eine gesundheitliche Bewertung ermittelter Konzentrationen von Dioxinen, Furanen und dioxinähnlichen PCB in Nahrungspflanzen erforderlich wird, kann hierzu der sogenannte TWI der EFSA herangezogen werden. Die Europäische Behörde für Lebensmittelsicherheit (EFSA 2018) hat als gesundheitsbezogenes Bewertungskriterium für Dioxine, Furane und dioxinähnliche PCB (dl-PCB) einen TWI-Wert (Tolerable Weekly Intake) in Höhe von 2 pg WHO-TEQ pro kg Körpergewicht und Woche abgeleitet. Dieser TWI-Wert basiert im Wesentlichen auf Daten aus Humanstudien, gestützt durch Daten aus Tierversuchen. Als kritischer Effekt wird von der EFSA die Qualität der Spermien junger Männer nach prä- und postnataler Exposition angegeben.
Fukushima ten years later: The catastrophic accident and its consequences On 11 March 2011 a strong earthquake and, following this, a tsunami occurred in Fukushima/Japan. Significant damage was done to the Fukushima Daiichi nuclear power plant, which was impossible to manage with the available safety and security systems. The radioactive substances released as a result of this accident have contaminated air , soil and water in the area around Fukushima. So far, it has not been possible to evaluate health effects finally. The Events in Brief A strong seaquake followed by a tsunami caused major damage to the Fukushima Daiichi nuclear power plant in Japan. Both the external power supply and the emergency power supply failed in reactor units 1-4. Core meltdowns and hydrogen explosions occurred. Significant amounts of radioactive substances were released into the atmosphere, especially in the first days after the nuclear disaster. Initial measures after the accident served to stabilise and secure units 1-4, and to transfer them to a controlled state. Further measures were taken to reduce the amount of radioactively contaminated water. From the end of 2023 onwards, the water that is contaminated mainly with tritium is to be discharged into the sea in diluted form. Investigations into the exact condition of the reactors are ongoing. Preparations for the removal of the fuel in unit 2 have been underway since 2022. By the end of 2031, the fuel elements from the fuel pools are to be completely discharged. Ten years ago, news from Japan shocked the world: the natural disaster of a tsunami was followed by the nuclear disaster of Fukushima. BASE has published a technical report on the anniversary of the accident: 10 years after Fukushima. Thinking ahead about safety What caused the catastrophic accident? What were the consequences for Japan? And how did the events of 11 March 2011 change the world? The technical report provides detailed answers to these questions. The most important findings and information are summarised on this page. The accident sequence in Fukushima On the afternoon of 11 March 2011, an earthquake in the Pacific Ocean caused a tsunami that hit the east coast of Japan. This triggered a series of accidents at the Fukushima Daiichi nuclear power plant, with nuclear meltdowns in three reactor blocks. As a result, significant amounts of radionuclides were released into the environment. Apart from Chernobyl, the catastrophic accident in Fukushima is the only one to be classified as a level 7 accident , which is the highest level on the International Nuclear and Radiological Event Scale (INES). Epicentre of the submarine earthquake © BASE There are six reactor units at the Fukushima Daiichi nuclear power plant. At the time of the earthquake, units 1-3 of the plant were in operation, and unit 4 was undergoing overhaul. The events - from the earthquake to the hydrogen explosions in the reactor units - are described below: Earthquake and tsunami A magnitude 9 earthquake disabled the external power supply for the Fukushima Daiichi power plant site. As a result, the emergency diesel generators of the individual units started up. They ensured the supply of important safety systems, especially the residual heat removal system. The earthquake caused a tsunami that reached the nuclear power plant about three quarters of an hour later. The waves at the site of the power plant measured up to 15.5 metres – more than twice the height of the site design basis tsunami (5.7 metres). © picture alliance / dpa | Aflo / Mainichi Newspaper Water entered the buildings and caused the failure of the running emergency diesel generators, the associated electrical switchgear and the cooling water systems. The uninterruptible DC power supply was also affected. This meant that both the external power supply and the emergency power supply failed in units 1-4 - this is referred to as a station blackout. Large parts of the emergency power supply in units 5 and 6 also failed. One emergency diesel generator continued to function and was used alternately for units 5 and 6. Severe core damage in these units was thus avoided. Core cooling and meltdown Overview of the Fukushima Daiichi plant © BASE As a result of the station blackout, the residual heat removal systems were no longer supplied with power. Only a number of passive systems (pressure limit, emergency condenser in unit 1, turbine-powered feed pumps) continued to function for a while longer, at least to a certain extent. These systems, which operate without an external power supply, slowed down the course of the accident but were unable stop it. Without functioning feed-in systems pumping water into the reactor pressure vessels and without heat removal from the containment vessels, it was not possible to keep the plant in safe operation permanently. The water level in the reactor pressure vessels subsequently dropped and exposed the reactor cores. This caused the reactor cores in units 1-3 to overheat and finally melt down. Pressure increase and hydrogen explosions Due to the absence of heat removal from the containment vessel, the pressure inside the containments in units 1-3 increased. The emergency countermeasure provided for such cases is the so-called venting to relieve containment pressure. Several valves are used to release the pressure in the containment vessels to the atmosphere through an exhaust stack. In the event of an accident, this should significantly reduce the release of radioactivity into the atmosphere. During a nuclear meltdown, the fuel rod cladding material reacts with water at high temperatures, and produces hydrogen. In Units 1, 3 and 4, insufficient venting caused hydrogen explosions that severely damaged the reactor buildings. The explosion in unit 4 - where no meltdown occurred- apparently resulted from hydrogen arising in unit 3 and reaching unit 4 by backflow through shared ducts. The explosions hampered and delayed the implementation of emergency countermeasures such as pumping water into the reactor pressure vessels. View of the site of the destroyed Fukushima Daiichi nuclear power plant © (c) dpa The report presents a chronological sequence of events: Chronology of the accident sequence (PDF. barrier-free, in German) Causes of the nuclear disaster IAEA team inspects the damaged Fukushima Daiichi nuclear power plant © picture alliance / AP Photo IAEA-Team Why did the earthquake and successive tsunami have such catastrophic consequences for the Fukushima Daiichi nuclear power plant? Why were precautionary measures insufficient? In addition to technical weaknesses, human factors and shortcomings in safety culture played a major role in the in the accident and its subsequent management. Expert teams from Japan and abroad concluded that Fukushima was less a natural disaster than a "man-made" one. Technical weaknesses of the plant The original 1966 tsunami design had defined the maximum wave height at +3.122 metres above sea level . Until 2009, this design had been re-evaluated several times. Based on these re-evaluations, retrofitting measures were carried out to increase the maximum wave height to 5.7 metres at the time of the accident . Starting in 2009, the operator had carried out a series of voluntary analyses. These showed possible tsunami heights of up to 9.3 metres for units 1-4. With regard to locations near the northern and southern boundaries of the plant site, the analysis identified possible tsunami heights of up to 15 metres ( cf. the tsunami height of 13.1 metres observed at the plant site on 11 March 2011). Yet, no changes were made to the plant as a result of these analyses. IAEA investigations also showed that the emergency power supply had not been adequately designed to withstand flooding. Inadequate containment pressure relief or venting following the tsunami also played a decisive role in the sequence of events. In this process, several valves are used to release the pressure in the containment vessels to the atmosphere through an exhaust stack. According to the IAEA , timely and successful venting in time would have facilitated more effective emergency measures for core cooling and could have prevented the hydrogen explosions of the reactor buildings. The explosion in Unit 4 (which was not affected by a core meltdown) - caused by the entry of hydrogen from Unit 3 - also demonstrates the inadequate venting. Cross-section of the plant and height of the tsunami © BASE Human and cultural factors Human and cultural factors © BASE/Michael Meier Japanese and international teams of experts concluded that Fukushima could have been prevented with appropriate precautions. Human and cultural factors played a decisive role in the catastrophic accident . Why were there no adequate precautions? Why was the accident not prevented or at least mitigated by comprehensive risk management? The technical weaknesses of the nuclear facilities were largely known and avoidable. Furthermore, there was no comprehensive safety culture in the cooperation between operating companies, the Japanese supervisory authority and the government. It was believed that a severe accident was not possible, and that the Japanese nuclear system was sufficiently safe and efficient. In addition, the inquiries launched after the accident claimed that the Japanese national culture, which is very much group-oriented and authority-centred, was one of the reasons for the poorly developed safety culture. The failure to learn from other serious accidents, such as those at the Three Mile Island ( USA ) or Chernobyl (Ukraine) nuclear power plants, was also cited. After the catastrophic accident in Fukushima, government organisations and operators worldwide reviewed their understanding of the concept of safety culture. Topics such as the independence of oversight authorities, the monitoring of operators’ safety culture, as well as the reflection on and promotion of individual safety culture concepts at the respective oversight authorities were put on the agenda. A more detailed account of the impact and significance of human, organisational and cultural factors can be found in the technical report (in German) . Radioactivity in the environment This girl returned to her old gym in Fukushima for a photo project © Carlos Ayesta - Guillaume Bression / fukushima-nogozone.com A significant amount of radioactive material was released into the environment as a result of the accident. This was one of the reasons why the accident at Fukushima Daiichi was rated level 7 (‘major accident’) on the International Nuclear and Radiological Event Scale. Release of radioactivity The release of radioactivity into the atmosphere was mainly caused by: Unfiltered containment venting: In addition to the release of noble gases, which would also have occurred with filtered venting, this led to the release of mainly highly volatile fission products such as iodine and caesium. Containment leakage: In the course of the accident , the design pressure and temperature of the containments were (in part significantly) exceeded in units 1-3. Leakage probably occurred during this process. In addition to being released into the atmosphere, radioactive substances were also released into water – especially the water injected for emergency cooling. As there were no more closed cooling circuits, large quantities of contaminated water escaped through leaks in the containment vessels and accumulated in the buildings. In early April 2011, heavily contaminated water leaked into the sea. In addition, water - mainly groundwater - entered the buildings from the outside. Various measures, including the sealing of leaks on buildings, were taken to successfully reduce the inflow of groundwater into the buildings. These include: Commissioning of groundwater drainage wells and drainage wells. Sealing leakages on buildings and building ducts Construction of a waterproof structural groundwater barrier directly in front of the quay wall Freezing the soil around the reactor buildings of units 1-4 Sealing off a large part of the plant site and the harbour basin seabed In addition, a purification plant for the contaminated water is in operation. Water that is not fed back into the reactors for cooling after treatment is temporarily stored in various tanks on the plant site. A constant expansion of the storage capacities has been necessary so far. Parts of the treated water are to be discharged into the sea from the end of 2023 on. This involves, in particular, groundwater that has been diverted around the power plant site. The concentration of radioactive substances still present in these waters is far below the legal limits. Tanks with radioactively contaminated water on the site of the Fukushima Daiichi nuclear power plant © picture alliance / ASSOCIATED PRESS | Yasushi Kanno Consequences for humans and the environment 250 km ... from Fukushima - in Tokyo - the iodine-131 contamination of the drinking water temporarily exceeded the safe level for young children. Numerous food items such as vegetables, milk or herbs from the affected regions were banned for consumption. At the end of March/beginning of April, high concentrations of caesium-137 and iodine-131 in particular were detected in the sea near the nuclear power plant, but dropped to low levels by the end of April. Fishing had to be suspended in part, because the radioactivity in several types of fish caught in the Fukushima area was above the legal limits. 20,000 ... People have died or are still reported missing as a result of the quake and tsunami. The tsunami flooded more than 560 km² of the Japanese mainland, over 470,000 buildings were severely damaged or destroyed, about 4,000,000 households had no electricity, and 2,300,000 households had no drinking water. 470,000 ... is the total number of evacuees in all prefectures, according to the Japanese government. The total number of persons evacuated due to the radiological situation in Fukushima Prefecture was approximately 110,000, and the total number of evacuees in Fukushima Prefecture was approximately 165,000. Of these, 37,000 still had not returned at the end of 2020. Radiation exposure in Germany and Europe Prevailing winds carried the released radionuclides, spreading them locally, regionally and globally, and successively dispersing them over land and sea. Which radioactive substance ended up where depended largely on the time of its release and the prevailing weather conditions at the time, i.e. wind and precipitation . For about a month after the Fukushima reactor accident , an increased concentration of iodine-131 and caesium-134/137 was measured in the air in Germany. However, the measured concentrations were low enough not to pose a health risk to people and the environment in Germany and Europe. By the end of May 2011, the measured values had returned to a pre- accident level . Measures for stabilisation and decommissioning Current aerial view of the Fukushima Daiichi plant (2020) © picture alliance / ASSOCIATED PRESS | Takehiko Suzuki Since the nuclear accident , the operator TEPCO has taken extensive measures to keep units 1-4 of the Fukushima Daiichi nuclear power plant in a controlled state and to minimise the release of radionuclides. At the same time, these measures serve to prepare for the decommissioning of the plant. According to current estimates, the entire decommissioning process will take 30 to 40 years. The measures taken to stabilise and decommission the nuclear power plant are described below: Steel enclosures The reactor buildings were badly damaged during the accident . The first step was to ensure the stability and functioning of the buildings throughout the entire decommissioning process. Enclosures were erected to prevent the release of radioactive substances into the environment. These enclosures also facilitate the installation of equipment to retrieve the fuel assemblies from the fuel pools and the nuclear material from the reactors. Reduction of contaminated water Radioactively contaminated water is a major problem. This mainly refers to water that was injected and subsequently contaminated during emergency cooling after the catastrophic accident . Since there were no more closed cooling circuits, large quantities of contaminated water accumulated in the buildings via leakages from the containment vessels. Through various measures, including sealing leaks on buildings, the inflow of groundwater into the buildings has since been significantly reduced (see "Release of radioactivity "). The operator TEPCO works to purify this contaminated water. Tritium , however, will remain. TEPCO plans to discharge the purified water into the sea in diluted form. Retrieval of the fuel elements Tepco plans to retrieve the destroyed reactor cores and the fuel elements from the fuel pools and to dispose of them. The fuel assemblies in the storage pools of Unit 4 were recovered between November 2013 and December 2014. Unloading for Unit 3 began in April 2019. Preparatory work, such as the removal of debris , is underway in Units 1 and 2. Investigations regarding the salvage of molten and subsequently solidified nuclear material from the reactors of units 1-3 are in progress. Two storage facilities for fuel elements are available on site: A central wet storage facility and a temporary dry storage facility. Retrieval of the nuclear material An overview of the condition of the inner areas of the reactor buildings is needed to retrieve the nuclear material from the reactors. Radiation levels in the buildings are high, and the condition and distribution of the nuclear material are unclear. Therefore, the retrieval will be carried out mainly by remotely-controlled robots. Initial trials using a newly developed robotic arm and gripping tools are to begin in unit 2. Remediation of the site Following several years of decontamination work in the vicinity of the Fukushima nuclear power plant, some of the evacuated areas were declared decontaminated. Important infrastructure facilities are also back in operation. To achieve this, roofs and gutters in the vicinity of the nuclear power plant were cleaned, soil surface layers were removed and organic material was collected. The large quantities of low- level radioactive waste were initially stored in many temporary storage facilities in the Fukushima region. Today, most of the waste is stored in a newly constructed interim storage facility, and the old storage sites have been re-cultivated. BASE’s technical report on the 10th anniversary of the catastrophic accident at Fukushima nuclear power plant provides a detailed discussion of topics such as decommissioning , remediation and waste management (only in german): Technical report for download © BASE / Michael Meier Earthquake and tsunami A magnitude 9 earthquake disabled the external power supply for the Fukushima Daiichi power plant site. As a result, the emergency diesel generators of the individual units started up. They ensured the supply of important safety systems, especially the residual heat removal system. The earthquake caused a tsunami that reached the nuclear power plant about three quarters of an hour later. The waves at the site of the power plant measured up to 15.5 metres – more than twice the height of the site design basis tsunami (5.7 metres). © picture alliance / dpa | Aflo / Mainichi Newspaper Water entered the buildings and caused the failure of the running emergency diesel generators, the associated electrical switchgear and the cooling water systems. The uninterruptible DC power supply was also affected. This meant that both the external power supply and the emergency power supply failed in units 1-4 - this is referred to as a station blackout. Large parts of the emergency power supply in units 5 and 6 also failed. One emergency diesel generator continued to function and was used alternately for units 5 and 6. Severe core damage in these units was thus avoided. Core cooling and meltdown Overview of the Fukushima Daiichi plant © BASE As a result of the station blackout, the residual heat removal systems were no longer supplied with power. Only a number of passive systems (pressure limit, emergency condenser in unit 1, turbine-powered feed pumps) continued to function for a while longer, at least to a certain extent. These systems, which operate without an external power supply, slowed down the course of the accident but were unable stop it. Without functioning feed-in systems pumping water into the reactor pressure vessels and without heat removal from the containment vessels, it was not possible to keep the plant in safe operation permanently. The water level in the reactor pressure vessels subsequently dropped and exposed the reactor cores. This caused the reactor cores in units 1-3 to overheat and finally melt down. Pressure increase and hydrogen explosions Due to the absence of heat removal from the containment vessel, the pressure inside the containments in units 1-3 increased. The emergency countermeasure provided for such cases is the so-called venting to relieve containment pressure. Several valves are used to release the pressure in the containment vessels to the atmosphere through an exhaust stack. In the event of an accident, this should significantly reduce the release of radioactivity into the atmosphere. During a nuclear meltdown, the fuel rod cladding material reacts with water at high temperatures, and produces hydrogen. In Units 1, 3 and 4, insufficient venting caused hydrogen explosions that severely damaged the reactor buildings. The explosion in unit 4 - where no meltdown occurred- apparently resulted from hydrogen arising in unit 3 and reaching unit 4 by backflow through shared ducts. The explosions hampered and delayed the implementation of emergency countermeasures such as pumping water into the reactor pressure vessels. View of the site of the destroyed Fukushima Daiichi nuclear power plant © (c) dpa Technical weaknesses of the plant The original 1966 tsunami design had defined the maximum wave height at +3.122 metres above sea level . Until 2009, this design had been re-evaluated several times. Based on these re-evaluations, retrofitting measures were carried out to increase the maximum wave height to 5.7 metres at the time of the accident . Starting in 2009, the operator had carried out a series of voluntary analyses. These showed possible tsunami heights of up to 9.3 metres for units 1-4. With regard to locations near the northern and southern boundaries of the plant site, the analysis identified possible tsunami heights of up to 15 metres ( cf. the tsunami height of 13.1 metres observed at the plant site on 11 March 2011). Yet, no changes were made to the plant as a result of these analyses. IAEA investigations also showed that the emergency power supply had not been adequately designed to withstand flooding. Inadequate containment pressure relief or venting following the tsunami also played a decisive role in the sequence of events. In this process, several valves are used to release the pressure in the containment vessels to the atmosphere through an exhaust stack. According to the IAEA , timely and successful venting in time would have facilitated more effective emergency measures for core cooling and could have prevented the hydrogen explosions of the reactor buildings. The explosion in Unit 4 (which was not affected by a core meltdown) - caused by the entry of hydrogen from Unit 3 - also demonstrates the inadequate venting. Cross-section of the plant and height of the tsunami © BASE Human and cultural factors Human and cultural factors © BASE/Michael Meier Japanese and international teams of experts concluded that Fukushima could have been prevented with appropriate precautions. Human and cultural factors played a decisive role in the catastrophic accident . Why were there no adequate precautions? Why was the accident not prevented or at least mitigated by comprehensive risk management? The technical weaknesses of the nuclear facilities were largely known and avoidable. Furthermore, there was no comprehensive safety culture in the cooperation between operating companies, the Japanese supervisory authority and the government. It was believed that a severe accident was not possible, and that the Japanese nuclear system was sufficiently safe and efficient. In addition, the inquiries launched after the accident claimed that the Japanese national culture, which is very much group-oriented and authority-centred, was one of the reasons for the poorly developed safety culture. The failure to learn from other serious accidents, such as those at the Three Mile Island ( USA ) or Chernobyl (Ukraine) nuclear power plants, was also cited. After the catastrophic accident in Fukushima, government organisations and operators worldwide reviewed their understanding of the concept of safety culture. Topics such as the independence of oversight authorities, the monitoring of operators’ safety culture, as well as the reflection on and promotion of individual safety culture concepts at the respective oversight authorities were put on the agenda. A more detailed account of the impact and significance of human, organisational and cultural factors can be found in the technical report (in German) . Release of radioactivity The release of radioactivity into the atmosphere was mainly caused by: Unfiltered containment venting: In addition to the release of noble gases, which would also have occurred with filtered venting, this led to the release of mainly highly volatile fission products such as iodine and caesium. Containment leakage: In the course of the accident , the design pressure and temperature of the containments were (in part significantly) exceeded in units 1-3. Leakage probably occurred during this process. In addition to being released into the atmosphere, radioactive substances were also released into water – especially the water injected for emergency cooling. As there were no more closed cooling circuits, large quantities of contaminated water escaped through leaks in the containment vessels and accumulated in the buildings. In early April 2011, heavily contaminated water leaked into the sea. In addition, water - mainly groundwater - entered the buildings from the outside. Various measures, including the sealing of leaks on buildings, were taken to successfully reduce the inflow of groundwater into the buildings. These include: Commissioning of groundwater drainage wells and drainage wells. Sealing leakages on buildings and building ducts Construction of a waterproof structural groundwater barrier directly in front of the quay wall Freezing the soil around the reactor buildings of units 1-4 Sealing off a large part of the plant site and the harbour basin seabed In addition, a purification plant for the contaminated water is in operation. Water that is not fed back into the reactors for cooling after treatment is temporarily stored in various tanks on the plant site. A constant expansion of the storage capacities has been necessary so far. Parts of the treated water are to be discharged into the sea from the end of 2023 on. This involves, in particular, groundwater that has been diverted around the power plant site. The concentration of radioactive substances still present in these waters is far below the legal limits. Tanks with radioactively contaminated water on the site of the Fukushima Daiichi nuclear power plant © picture alliance / ASSOCIATED PRESS | Yasushi Kanno Consequences for humans and the environment 250 km ... from Fukushima - in Tokyo - the iodine-131 contamination of the drinking water temporarily exceeded the safe level for young children. Numerous food items such as vegetables, milk or herbs from the affected regions were banned for consumption. At the end of March/beginning of April, high concentrations of caesium-137 and iodine-131 in particular were detected in the sea near the nuclear power plant, but dropped to low levels by the end of April. Fishing had to be suspended in part, because the radioactivity in several types of fish caught in the Fukushima area was above the legal limits. 20,000 ... People have died or are still reported missing as a result of the quake and tsunami. The tsunami flooded more than 560 km² of the Japanese mainland, over 470,000 buildings were severely damaged or destroyed, about 4,000,000 households had no electricity, and 2,300,000 households had no drinking water. 470,000 ... is the total number of evacuees in all prefectures, according to the Japanese government. The total number of persons evacuated due to the radiological situation in Fukushima Prefecture was approximately 110,000, and the total number of evacuees in Fukushima Prefecture was approximately 165,000. Of these, 37,000 still had not returned at the end of 2020. Radiation exposure in Germany and Europe Prevailing winds carried the released radionuclides, spreading them locally, regionally and globally, and successively dispersing them over land and sea. Which radioactive substance ended up where depended largely on the time of its release and the prevailing weather conditions at the time, i.e. wind and precipitation . For about a month after the Fukushima reactor accident , an increased concentration of iodine-131 and caesium-134/137 was measured in the air in Germany. However, the measured concentrations were low enough not to pose a health risk to people and the environment in Germany and Europe. By the end of May 2011, the measured values had returned to a pre- accident level . Steel enclosures The reactor buildings were badly damaged during the accident . The first step was to ensure the stability and functioning of the buildings throughout the entire decommissioning process. Enclosures were erected to prevent the release of radioactive substances into the environment. These enclosures also facilitate the installation of equipment to retrieve the fuel assemblies from the fuel pools and the nuclear material from the reactors. Reduction of contaminated water Radioactively contaminated water is a major problem. This mainly refers to water that was injected and subsequently contaminated during emergency cooling after the catastrophic accident . Since there were no more closed cooling circuits, large quantities of contaminated water accumulated in the buildings via leakages from the containment vessels. Through various measures, including sealing leaks on buildings, the inflow of groundwater into the buildings has since been significantly reduced (see "Release of radioactivity "). The operator TEPCO works to purify this contaminated water. Tritium , however, will remain. TEPCO plans to discharge the purified water into the sea in diluted form. Retrieval of the fuel elements Tepco plans to retrieve the destroyed reactor cores and the fuel elements from the fuel pools and to dispose of them. The fuel assemblies in the storage pools of Unit 4 were recovered between November 2013 and December 2014. Unloading for Unit 3 began in April 2019. Preparatory work, such as the removal of debris , is underway in Units 1 and 2. Investigations regarding the salvage of molten and subsequently solidified nuclear material from the reactors of units 1-3 are in progress. Two storage facilities for fuel elements are available on site: A central wet storage facility and a temporary dry storage facility. Retrieval of the nuclear material An overview of the condition of the inner areas of the reactor buildings is needed to retrieve the nuclear material from the reactors. Radiation levels in the buildings are high, and the condition and distribution of the nuclear material are unclear. Therefore, the retrieval will be carried out mainly by remotely-controlled robots. Initial trials using a newly developed robotic arm and gripping tools are to begin in unit 2. Remediation of the site Following several years of decontamination work in the vicinity of the Fukushima nuclear power plant, some of the evacuated areas were declared decontaminated. Important infrastructure facilities are also back in operation. To achieve this, roofs and gutters in the vicinity of the nuclear power plant were cleaned, soil surface layers were removed and organic material was collected. The large quantities of low- level radioactive waste were initially stored in many temporary storage facilities in the Fukushima region. Today, most of the waste is stored in a newly constructed interim storage facility, and the old storage sites have been re-cultivated.
Das Projekt "Wärmeversorgung für die Stadt Schwandorf" wird vom Umweltbundesamt gefördert und von Stadt Schwandorf durchgeführt. Objective: To use the heat contained in the condenser cooling water of the power plant of the Bayernwerk AG at Schwandorf to cover the need for space heating in parts of the town. General Information: Condenser cooling water from the power plant of the Bayernwerk AG is used as the heat source for the heat pumps of the city heating system of Schwandorf. The water is diverted from the power plant's cooling water system before the entry into the cooling tower and is pumped to the heat pump station of the city heating system. After the water has been cooled down in the heat pump evaporators, it is discharged into the river Naab. The cooling of the condenser cooling water in the evaporators and the heat generated by the heat pumps and recovered from the waste heat of the heat pump gas motors yield a total heating power of 4.1 MW. The heating water of 60 deg.C to max. 75 deg.C is fed via heat exchangers into the heating installations of the users (public buildings). The heat pumps are capable of coping with outside temperature of above 4 deg.C. Below this temperature level, boilers are used to cover the missing heat generation capacity. In total 14 users are connected with the city heating network: 2 swimming pools, a hospital, 5 schools and 6 other large public buildings. The capacity of the system is 4.100 KW, producing annually 15.877 MWh at a cost of DM 773.759 p.a. (excluding the cost of capital) against DM 1,191,525 for a conventional system using fuel at DM 0.65/l, saving therefore DM 417.766 p.a. This saving represents a 14.2 year payback of the additional investment (DM 5.0930.617) compared to a conventional heating system. Achievements: The project was finished in 1985. From that time until the final report no changes were made. The final report was submitted in January 1989. The outcome achieved was not good because expected sales could not be achieved. The average annual sale was 10.000 MWh so a considerable loss was incurred. As the expected supply of 15.877 MWh could never be achieved, less district heating was supplied and it was only with this that energy could have been saved. The loss in the financial year 1990 amounted to DM 880.000. The previous year yielded similar results. Prime Contractor: Grosse Kreisstadt Schwandorf; Schwandorf; Germany.
Das Projekt "Gasmotorgetriebene Waermepumpe mit Waermeextraktion aus dem Boden fuer die Raumheizung" wird vom Umweltbundesamt gefördert und von Kreis Warendorf, Kreisdirektor durchgeführt. Objective: The aim of the project is to demonstrate the use of a gas compression heat pump with the soil as heat source in the heating range power above 1 000 kW. Energy savings of 50 per cent compared with a conventional boiler plant are envisaged. General Information: The heating plant of the district building in Warendorf consists of a combination of two gas heat pump units with three gas boilers to cover the peak load and produce hot water. The heat pumps are dimensioned for coverage of the transmission heat demand of 1 150 kW, two soil heat exchangers (6 800 m2, 2 100 m2) are used as heat source for the heat pumps, the heat exchangers consist of pe-tubings in parallel one besides the other in plane, they are installed in 2 depths of 0.8 and 1.8 beneath the soil surface. The building under consideration having 17.700 square m. of heated area, was designed to have a K value of 0.2 W/square m.K. and the load was calculated under 21 Deg. C inside and 12 Deg. C outside design temperatures. The infiltration coefficient was taken as 9,4 cubic m/h sq. m. of window surface, corresponding to an air charge of 1 time per hour. At present energy price levels the heat pump heating capacity was designed to be about 60 per cent of the total transmission heat demand. The construction of the plant implies the combination of both heat pumps connected to a common evaporator and condenser. Each screw compressor used, being slide valve regulated, is directly coupled to gas-Otto 6 cylinder drive engine rated at 13 kW output. The refrigerant R-12 is evaporated in a flooded type evaporator of 440 kW capacity, at 10 Deg. C evaporating temperature. The condenser is an ordinary bundle type condenser, rated as 680 kW, at 55 Deg. C condensing temperature. Heat is extracted from soil and rain water using a brine circuit operating at 2 to 5 Deg. C lower than corresponding soil temperature, and 5 Deg. C temperature differential across the evaporator. The maximum heat absorption coefficient amounts to 49 W/sq. m. of soil area. Heating water flows first through a low temperature circuit operating at 50.9 Deg. C, and consisting of the oil-coolers, condenser and gear coolers. A partial flow of the heating water is then passed through the high temperature circuit operating at 63.5 Deg. C, consisting of the motor jacket heat exchanger and waste gas heat exchangers. A buffer store integrated into the heat pump system stores the high temperature heat and supplies the impulses for switching on and off the heat pumps and the boiler. A special characteristic of this installation is that the mechanical room is located in the attic of the building and sound proofing is ascertained by a proper design. Saving of 51.5 per cent versus 55 per cent expected. Achievements: During the heating periods 1982/83 and 83/84 there were longer non-availability periods of the plant mainly due to damage of the soil heat exchangers, corrosion problems in motor heat exchangers, motors failures etc. ...
Das Projekt "Teilvorhaben 1: Konzeptentwicklung und Planung einer Pilotanlage für das Recycling von Tantal" wird vom Umweltbundesamt gefördert und von Fraunhofer-Institut für Silicatforschung (ISC), Projektgruppe für Wertstoffkreisläufe und Ressourcenstrategie (IWKS) durchgeführt. Das Übergangsmetall Tantal ist ein Element mit zahlreichen Anwendungsmöglichkeiten in der modernen Technik. Sein sehr hoher Schmelzpunkt von ca. 3000 °C und seine Korrosionsbeständigkeit machen es zu einem begehrten Werkstoff in der chemischen Industrie und der Medizintechnik. Das Hauptanwendungsgebiet liegt jedoch im Bereich Elektronik. Als namensgebender Bestandteil in Tantal-Kondensatoren ermöglicht das Übergangsmetall durch seine besonderen elektrischen Eigenschaften die Konstruktion von Bauteilen, die bei geringem Volumen eine sehr hohe elektrische Kapazität besitzen. Der Einsatz von Tantal-Kondensatoren erlaubt deshalb die Miniaturisierung von Elektrogeräten. Allerdings erfolgt die Förderung von Tantal zu erheblichen Teilen aus der politisch instabilen 'Große-Seen-Region' in Afrika und der Tantal-Abbau wird hier teilweise zur Finanzierung von kriegerischen Auseinandersetzungen genutzt. Deshalb wird dieses Tantal von der US-Börsenaufsichtsbehörde SEC als konfliktfördernd eingestuft. Um unbedenkliches Tantal verwenden zu können, muss entsprechend zertifiziertes - wie z.B. durch die OECD und die Conflict-Free Sourcing Initiative - erworben werden. Außerdem liegt die Recyclingquote von Tantal aus Altgeräten bei unter einem Prozent, da es auf dem herkömmlichen Kupferrecyclingweg verloren geht. Das Projekt IRETA, 'Entwicklung und Bewertung innovativer Recyclingwege zur Rückgewinnung von Tantal aus Elektronikabfällen', das mit rund 700.000 Euro im Rahmen der 'KMU-Innovationsoffensive Ressourcen- und Energieeffizienz' des BMBF gefördert wird, erforscht deshalb Recyclingwege, bei denen vollkommen neue Prozesswege im Zusammenhang mit Tantal zur Anwendung kommen. Dadurch soll eine Sekundärproduktion aufgebaut werden, die den Importbedarf von Tantal entsprechend senken wird. Dies bringt ökonomische Vorteile für die Industrie und trägt entscheidend zur Versorgungssicherheit Deutschlands bei. Der geplante Recyclingweg startet damit, dass die Tantal-Kondensatoren über eine optische Erkennungssoftware auf den Platinen von Elektroaltgeräten identifiziert und anschließend vollautomatisch demontiert werden. Anschließend folgt eine mechanische Aufbereitung der Kondensatoren zu einem Pulver. Mit drei verschiedenen innovativen Recyclingwegen, die auf chemischem Transport, funktionalisierten Nanopartikeln und elektrochemischer Abscheidung basieren, wird das Tantal aus diesem Pulver in Reinform wiedergewonnen. Eine vergleichende Bewertung der Recyclingwege unter ökonomischen und ökologischen Aspekten soll Aufschluss darüber geben, welcher dieser drei Prozesse für den Aufbau einer Pilotanlage infrage kommt.
Das Projekt "Kompression von Abdampf mithilfe eines gasmotorgetriebenen Schraubenverdichters in einer Brauerei" wird vom Umweltbundesamt gefördert und von MAN Technologie GmbH durchgeführt. Objective: To demonstrate that vapor compression by means of a gas engine driven screw compressor shows high reliability and considerably reduces the energy consumption of the brewing process. General Information: By means of an internal combustion engine driven vapor compression plant the energy consumption in a brewery can be considerably reduced. The energy saving is achieved by increasing the temperature of the waste vapor during compression and subsequent release of the heat back to the wort and by using the waste of the combustion engine in the brewery. The demonstrated vapor compression plant is installed in a brewery with an annual output of 1200000 hl of beer. The waste vapor (5.4 t/y, 1 bar, 100 deg. C) coming from the wort copper (normally exhausted to the air) is pumped by the screw compressor driven by a gas engine (187 kW) up to 1.3 bar and 110 deg. C. The hot vapor is condensated in the vapor thermostar by heating the wort (3.3 MW). The hot condensate leaving the vapor condenser is cooled down by an additional heat exchanger (462 kW). This heat is used together with the usable waste heat from the gas engine (450 kW) for hot water production needed in the brewery. With a primary energy input (natural gas) of 550 kW and the usable heat output of 4,212 kW a primary energy ratio of 7.65 is yielded. Achievements: The plant runs successfully and is distinguished by high reliability with minimum costs for operation and maintenance. Numerous measurements have shown that in the field less fouling of the vapor condenser occurs than had been assumed. The condenser is only cleaned once a week, without any appreciable increase in the condensate pressure being noted towards the end of the week. The screw compressor, which is subject to only slight fouling, has so far not needed any cleaning. The integration of the vapor compression system in the brewing process has had no influence on the process as a whole. Energy measurements of the system have yielded the high primary energy ratio (usable heat/gas energy input) of 6.95 (with respect to the gross calorific value of natural gas) and 7.65 (with respect to the net calorific value). The annual saving in energy is about 1 million cubic meters of natural gas. This means an energy saving of 89 per cent. Unfortunately the efficiency of the screw compressor is less than expected and therefore the brake horse power higher than calculated. Presumably the water injection, which keeps the vapor output temperature down, has a greater influence in reducing efficiency than had previously been assumed. The electromagnetic clutch is the chief cause of vibrations. With the help of suitable balancing experiments, however, vibration can be reduced to an acceptable level. Economic feasibility calculations show that vapor compression plants have good market prospects in breweries with more than 1,400 brews per year (at present gas prices). In designing a brewery, this number can be achieved by a proper layout of ...
Das Projekt "Use of the variance-covariance method in radiation protection" wird vom Umweltbundesamt gefördert und von Universität Würzburg, Biozentrum, Institut und Lehrstuhl für Humangenetik durchgeführt. General Information: Reductions of the dose limits in radiation protection and changes of the quality factor for densely ionizing radiations will require increased precision in area monitoring and in personal dosimetry. Tissue equivalent proportional counters are increasingly employed for this purpose. However, their routine use in radiation protection requires the variance-covariance method which is an extension of the pulse height determination in two ways: it is not restricted to radiation fields of extremely low dose rate and, unlike the variance methods, it is applicable in the time varying radiation fields that are frequently encountered in radiation protection practice. Achievements: Measurements in the field of a diagnostic X-ray tube have been performed with a 2 pulse generator. The beam was filtered with 1 mm of aluminium. The twin detector consists of 2 cylindrical proportional counters. The plastic detector walls have a thickness equivalent to 13 mm of tissue. The detector currents are integrated on capacitors. The voltage at the capacitors is digitized and the results stored on a computer. Calibration of the proportional counters was performed with an americium-241 alpha source. As a side product to this the Townsend coefficients for methane based tissue equivalent gas have been determined for a broad range of reduced field strengths. In further measurements variations of the dose averaged lineal energy, y d, during the 10 ms time interval of the high voltage pulse of the X-ray tube have been determined. In a theoretical analysis the inherent possibilities of the variance covariance method for suppression of noise and electric pickup have been examined. Several types of disturbances have been considered. Preliminary measurements have been performed in the photon and electron fields of a 20 MV linear accelerator. To cope with the high dose rate 2 improvements of the instrumentation are necessary. Increased sampling frequency will reduce the dose per sampling interval and smaller detectors will reduce the current delivered. In the experimental system, the signal processing has been improved by the implementation of faster and more accurate analogue to digital conversions (ADC) and the mechanical device for pressure stabilization in the gas flow system has been replaced by an electronic pressure control. In addition the gas flow is now adjusted by a mass flow control. Work is being done to transform a system designed for variance covariance measurements in pulsed therapeutic X-ray and electron fields into one appropriate for measurements in continuous cobalt-60 beam, regarded as an intermediate step before measuring in diagnostic X-rays. The proportional counters were found to be unsuitable for continuous beam measurements so it has been decided to apply new detectors. Ionization chambers and charge integration have been chosen to achieve a more satisfactory calibration. 2 Keithley 617 programmable electrometers together with a ...
Das Projekt "Gegendrucksteuerung von Hochoefen durch Einsatz einer Kopfggas-Druckentlastungsturbine" wird vom Umweltbundesamt gefördert und von Thyssen Stahl durchgeführt. Objective: To install and test a top gas pressure relief turbine to use the pressure drop in the blast furnace after waste gas cleaning to generate electrical power (13,480 kW) to achieve annual energy saving of 7,760 TOE at project level. Assuming average power plant efficiency, this should correspond to primary energy saving of +- 27,000 TOE/y. General Information: Top-gas pressure allows appreciably higher specific outputs for a given furnace volume. Longer gas residence time in the blast furnace leads top gas flow homogenisation and reduced coke consumption. While a low fraction of gas pressure (0.25 Bar max.) is required for the downstream gas cleaning system, residual pressure 2 Bar max. is lost through throttling, equivalent to +- 30 per cent of energy used for blast compression. In order to utilize the pressure drop in the top gas after waste gas cleaning it was decided to install a pressure recovery turbine which is located downstream of the scrubbers in the already existing gas purification facilities at Schwelgern. It was decided to install a double-flow, four stage axial type reaction turbine designed to generate 13.5 MWh from a gas throughput of 587,000 m3/h, admission temperature of 45 deg C and a differential pressure of 1.8 Bar. The cast steel turbine casing is 3,870 mm in length, 3,500 mm maximum height. The rotor is 6,055 mm long, of1,692 mm maximum diameter and weighs 75 Tons. The admission guide blades of the first stage are variable to attain a regular top-gas pressure. In addition, they ensure identical efficiency over a broad operating range. Coupled to the turbine is a 14 MWh self-excited asynchronous generator of 1,500 rpm output speed. When switching to the power network, the self-excitation mode precludes any voltage drop. By connecting capacitors to the generator terminals, cover for the no-load reactive power is guaranteed. Gas pressure within the network is 0.2 Bar. All operational sequences are predetermined, executed and monitored by a control and regulating system. Turbine start-up and shut-down is automatic with no appreciable effect on top gas pressure. Licences can be obtained from Zimmermann and Jansen. Achievements: To perform the test programme, 60 measuring points were logged. An electronic digital measuring point logging system was also put into operation in parallel with the conventional analogue one. Most of these measuring points were equipped with a buffer amplifier to prevent signal interference. The turbine output depends primarily on pressure drop, inlet temperature and mass flux i.e. on factors influenced by the operational mode of up and down stream facilities. In order to take account of these variables, the following influencing parameters were examined: - increasing inlet pressure; - reducing outlet pressure; - increasing gas inlet temperature; - reducing scrubber water temperature; - gas flow rate; - top gas composition. A total of three main trials and preliminary tests were conducted ...
Das Projekt "Supercapacitor development for automotive systems" wird vom Umweltbundesamt gefördert und von Bayer AG durchgeführt. General Information: Super capacitors have a much higher power density than a conventional battery and when used in combination with a battery and power management system they can be used to create a highly efficient and versatile power source. They have an important role in electric vehicle technology but they can also be used to great effect in conventional and hybrid vehicles for regenerative braking and for powering a wide range of subsystems. In automotive applications the main requirements placed upon the super capacitor are: - High power density - High discharge rate - Wide temperature range These requirements call for a very low impedance device. This can be achieved by the use of advanced materials and meticulous attention to all aspects of the design. The proposed development uses new conducting polymer technology in combination with thin layer techniques to create a super capacitor which is targeted at the immediate needs of the automotive industry. The main advantages of using super capacitor technology are as follows: - Improved electrical systems with the capability to deliver high peak powers. - A reduction in the battery size and overall weight of the system. - Extended battery life under adverse load conditions. - Improved efficiency and operating range of electric vehicles. - Improved fuel consumption of conventional and hybrid vehicles. - Improved electrical subsystems for automotive applications e.g. catalytic converters. With the development of more advanced forms of electric vehicle, super capacitors will certainly play an important part in meeting the aims and objectives of the Task Force 'Car of Tomorrow'. In addition the technology can be applied to many other industrial areas. The proposal addresses the following areas of the IMT (JOULE) work programme:2.4.A.2.3 .1 and 2.4.A.2.3 .3. Prime Contractor: ERA Technology Ltd.; Leatherhead - Surrey; United Kingdom.
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