Aus der amerikanischen Pestizidfabrik Union Carbide Corporation in Bhopal (Indien) entweicht aus einem lecken Tank Methylisocyanat. Die Folgen sind 3 400 Tote und ca. 200 000 Schwerverletzte.
Umweltbundesamt begrüßt Fortschritte im internationalen Chemikalienmanagement und mahnt weiter zur Wachsamkeit Am 03. Dezember 1984 ereignete sich in der indischen Stadt Bhopal in einem Betrieb der Union Carbide India Ltd ein folgenschwerer Chemieunfall. Wegen zahlreicher Mängel, Fehler und nicht funktionierender Sicherheitseinrichtungen, gelangte eine Gaswolke aus 20 bis 30 Tonnen des sehr giftigen Zwischenproduktes Methylisocyanat in die Atmosphäre. In der ersten Woche starben mindestens 2.500 Menschen und 500.000 wurden zum Teil schwer verletzt. Noch Jahre später waren bis zu 50.000 Menschen in Folge des Unfalls behindert und die Sterblichkeitsrate in der Bevölkerung erhöht. In Bhopal lebten zum Zeitpunkt des Unglücks etwa 700.000 Menschen, davon ca. 130.000 in unmittelbarer Nähe zum Betrieb. Das Unglück ist die bis heute schlimmste Chemiekatastrophe. „Der Preis für Industriekatastrophen wie in Bhopal ist so hoch, dass die Lehren daraus nicht in Vergessenheit geraten dürfen. Auch in Deutschland und Europa müssen wir immer wieder kritisch prüfen, ob wir genug für die Sicherheit unserer chemischen Anlagen tun”, sagte Jochen Flasbarth, Präsident des Umweltbundesamtes (UBA). Das Bhopal-Unglück löste weltweit Aktivitäten aus, chemische Betriebe sicherer zu machen. Bereits aufgrund früherer Störfälle, wie dem in der italienischen Stadt Seveso 1976, schuf Deutschland 1980 mit der Störfall-Verordnung und 1982 die EU in der Seveso-Richtlinie ein übergreifendes Anlagensicherheitsrecht. Die Störfall-Verordnung fordert ein stringentes Sicherheitskonzept, um Störfälle zu verhindern oder deren Auswirkungen zu begrenzen. Systematische sicherheitsanalytische Untersuchungen industrieller Produktionsverfahren und Anlagen sind heute Standard. Unterstützt werden diese Fortschritte durch Informationspflichten nach der europäischen Chemikalienverordnung REACH , wonach Chemikalienhersteller auch Zwischenprodukte bei der Europäischen Chemikalienagentur registrieren müssen. Methylisocyanat, das in Bhopal zur Katastrophe führte, ist ein Beispiel dafür. Unternehmen in Industriestaaten müssen auch Verantwortung für die Sicherheit ihrer Chemieanlagen in weniger entwickelten Ländern übernehmen. Sicherheitsstandards dürfen nicht geringer als in Europa oder Nordamerika sein. Dafür wurden von der Organisation für Ökonomische Zusammenarbeit und Entwicklung ( OECD ) und der Wirtschaftskommission für Europa der Vereinten Nationen ( UNECE ) Leitfäden erarbeitet. Diese fordern bei dortigen Investitionen gleiche Sicherheitsniveaus wie in Industriestaaten. Dies gilt auch für deutsche Unternehmen. Ob die Empfehlungen immer befolgt werden, ist bisher nicht geprüft. Die zunehmende Vernetzung der internationalen Chemikalienproduktion demonstriert, wie wichtig internationale Sicherheitsstandards in der Chemikalienproduktion sind. Geringere Standards dürfen kein Wettbewerbsvorteil sein. Internationale Übereinkommen zum Chemikalienmanagement nehmen dazu auch die Industriestaaten in die Pflicht: So dürfen nach dem Rotterdamer Übereinkommen (Prior Informed Consent Procedure = PIC) gefährliche Chemikalien nur mit Informationen zu ihren Wirkungen auf die menschliche Gesundheit und die Umwelt und nicht ohne vorherige Zustimmung durch das Empfängerland exportiert werden. Das Umweltbundesamt unterstützt durch Fachinformationen die Fortentwicklung dieses Übereinkommens. Das Umweltbundesamt ist der Meinung, dass die Sicherheit der Chemikalienproduktion noch weiter verbessert werden muss. Erkenntnisse aus der Katastrophe in Bhopal sollten noch mehr beachtet werden, indem man zum Beispiel:
technologyComment of chromium production (RoW): Metallic chromium is produced by aluminothermic process (75%) and electroylsis of dissolved ferrochromium (25%) technologyComment of chromium production (RER): Metallic chromium is produced by aluminothermic process (75%) and electroylsis of dissolved ferrochromium (25%) ALUMINOTHERMIC PROCESS The thermic process uses aluminium as a reducing agent for chromium hydroxide. The charge is weighed and loaded into a bin, which is taken to an enclosed room to mix the contents. The firing pot is prepared by ramming refractory sand mixed with water around a central former. After ramming the firing pot, the inner surface is coated with a weak binder solution and dried under a gas fired hood before being transferred to the firing station. The raw material mix is automatically fed at a controlled rate into the firing pot, where the exothermic reaction takes place. When the metal has solidified following the reaction, the firing pot is removed and transferred by crane to a cooling conveyor. On removal from the cooling conveyor (by crane), the firing pot is placed on a stripping bogie for transferral to a stripping booth. Inside the closed booth, the pot casing is hoisted off the solidified metal/slag. The slag is separated from the Chromium metal “button” and sent to a despatch storage area. Water is used to reduce button temperature to below 100 ºC. After cooling the metal button is transferred to other departments on site for cleaning, breaking, crushing and grinding to achieve the desired product size. ELECTROLYTIC PROCESS In the electrolytic process normally high carbon ferrochrome is used as the feed material which is then converted into chromium alum by dissolution with sulphuric acid at temperatures at about 200 ºC. After several process steps using crystallisation filtration ageing, a second filtration and a clarifying operation the alum becomes the electrolyte for a diaphragm cell. Chromium is plated onto stainless steel cathodes until it attains a thickness of ca. 3 mm. The process is very sensitive. The additional de-gassing (heating at 420 °C) stage is necessary because the carbon content of the electrolytic chromium is sometimes too high for further industrial applications. The cooled chromium metal is fragmented with a breaker prior to crushing and drumming. The generated slag can be reused as refractory lining or sold as abrasive or refractory material. Overall emissions and waste: Emissions to air consist of dust and fume emissions from smelting, hard metal and carbide production; other emissions to air are ammonia (NH3), acid fume (HCl), hydrogen fluoride (HF), VOC’s and heavy metals. Emissions to water are overflow water from wet scrubbing systems, wastewater from slag and metal granulation, and blow down from cooling water cycles. Solid waste is composed of dust, fume and sludge, and slag. References: 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 manganese production (RER): The metal is won by electrolysis (25%) and electrothermic processes (75%). ELECTROLYSIS OF AQUEOUS MANGANESE SALTS The production of manganese metal by the electrolysis of aqueous manganese salts requires at first a milling of the manganese ore. Milling increases the active surface and ensures sufficient reactivity in both the reduction and the subsequent leaching steps. After milling the manganese ore is fed to a rotary kiln where the reduction and calcination takes place. This process is carried out at about 850 - 1000 ºC in a reducing atmosphere. As a reducing agent, several carbon sources can be used e.g. anthracite, coal, charcoal and hydrocarbon oil or natural gas. The cal-cined ore needs to be cooled below 100 ºC to avoid a further re-oxidation. The subsequent leaching process is carried out with recycled electrolyte, mainly sulphuric acid. After leaching and filtration the iron content is removed from the solution by oxidative precipitation and the nickel and cobalt are removed by sulphide precipitation. The purified electrolyte is then treated with SO2 in order to ensure plating of γ-Mn during electrolysis. Electrolysis is carried out in diaphragm cells. The cathode is normally made of stainless steel or titanium. For the anode lead-calcium or lead-silver alloy can be used. After an appropriate reaction time the cathodes are removed from the electrolysis bath. The manganese that is deposited on the cathode starter-sheet is stripped off mechanically and then washed and dried. The metal is crushed to produce metal flakes or powder or granulated, depending on the end use. ELECTROTHERMAL DECOMPOSITION OF MANGANESE ORES The electrothermal process is the second important process to produce manganese metal in an industrial scale. The electrothermal process takes place as a multistage process. In the first stage manganese ore is smelted with only a small amount of reductant in order to reduce mostly the iron oxide. This produces a low-grade ferro-manganese and a slag that is rich in Mn-oxide. The slag is then smelted in the second stage with silicon to produce silicomanganese. The molten silicomanganese can be treated with liquid slag from the fist stage to obtain relatively pure manganese metal. For the last step a ladle or shaking ladle can be used. The manganese metal produced by the electrothermal process contains up to 98% of Mn. Overall emissions and waste: Emissions to air consist of dust and fume emissions from smelting, hard metal and carbide production; Other emissions to air are ammonia (NH3), acid fume (HCl), hydrogen fluoride (HF), VOC and heavy metals. Effluents are composed of overflow water from wet scrubbing systems, wastewater from slag and metal granulation, and blow down from cooling water cycles. Waste includes dust, fume, sludge and slag. References: Wellbeloved D. B., Craven P. M. and Waudby J. W. (1997) Manganese and Manganese Alloys. 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 manganese production (RoW): The metal is won by electrolysis (assumption: 25%) and electrothermic processes (assumption: 75%). No detailed information available, mainly based on rough estimates. technologyComment of treatment of non-Fe-Co-metals, from used Li-ion battery, hydrometallurgical processing (GLO): The technique SX-EW is used mainly for oxide ores and supergene sulphide ores (i.e. ores not containing iron). It is assumed to be used for the treatment of the non-Fe-Co-metals fraction. The process includes a leaching stage followed by cementation or electro-winning. A general description of the process steps is given below. In the dump leaching step, copper is recovered from large quantities (millions of tonnes) of strip oxide ores with a very low grade. Dilute sulphuric acid is trickled through the material. Once the process starts it continues naturally if water and air are circulated through the heap. The time required is typically measured in years. Sulphur dioxide is emitted during such operations. Soluble copper is then recovered from drainage tunnels and ponds. Copper recovery rates vary from 30% to 70%. Cconsiderable amounts of sulphuric acid and leaching agents emit into water and air. No figures are currently available on the dimension of such emissions. After the solvent-solvent extraction, considerable amounts of leaching residues remain, which consist of undissolved minerals and the remainders of leaching chemicals. In the solution cleaning step occur precipitation of impurities and filtration or selective enrichment of copper by solvent extraction or ion exchange. The solvent extraction process comprises two steps: selective extraction of copper from an aqueous leach solution into an organic phase (extraction circuit) and the re-extraction or stripping of the copper into dilute sulphuric acid to give a solution suitable for electro winning (stripping circuit). In the separation step occurs precipitation of copper metal or copper compounds such as Cu2O, CuS, CuCl, CuI, CuCN, or CuSO4 • 5 H2O (crystallisation) Waste: Like in the pyrometallurgical step, considerable quantities of solid residuals are generated, which are mostly recycled within the process or sent to other specialists to recover any precious metals. Final residues generally comprise hydroxide filter cakes (iron hydroxide, 60% water, cat I industrial waste).
technologyComment of ethylene oxide production (RER): Ethylene is directly oxidized with air or oxygen in the presence of a catalyst to ethylene oxide (EO). About 40% of all European EO production is converted into glycols, globally the figure is about 70%. Usually, EO and MEG are produced together at integrated plants. Industrial production started in 1937 with a union Carbide process based on ethylene and air. In 1958 oxygen rather than air was instroduced by Shell Development Company, and today most processes are based on oxygen. Total European production was 3.4 million tons per year in 1997, while the US produced 5.2 million tons per year. Further production capacity of at least 1.2 million tons is reported from Saudi Arabia, Kuwait, Japan and South Korea giving a total of at least 9.8 million tons of ethylene oxide production worldwide. Ethylene oxide is a hydrocarbon compound made from ethylene and oxygen. Major manufacturers include Hoechst Celanese, Shell Chemical, and Union Carbide, among many others. EO is produced by passing a mixture of ethylene and oxygen over a solid silver-containing catalyst. Selectivity is improved by the addition of chlorine compounds such as chloroethane. Reaction conditions are temperatures of about 200 - 300 °C and a pressure of 10 – 30 bar. The main by-products are carbon dioxide and water, formed when ethylene is fully oxidised or some of the EO is further oxidised. Ethylene glycols are formed when the reactor gases are absorbed into chilled water. C2H4 + 1/2 O2 C2H4O (1) C2H4 O + H2O HO-C2H4-OH (2) C2H4 + 3 O2 2 CO2 + 2 H2O (3) (1) production of ethylene oxide (2) production of MEG from EO and water (3) production of carbon dioxide and water from oxidation of ethylene The carbon dioxide is removed from the scrubber by absorption with hot aqueous potassium carbonate, the resulting solution is steam stripped to remove the carbon dioxide, which is vented to air. The potassium carbonate is regenerated. The carbon dioxide can be reused for inerting, or is sold, or is vented to atmosphere. References: IPPC Chemicals, 2002. European Commission, Directorate General, Joint Research Center, “Reference Document on Best Available Techniques in the Large Volume Organic Chemical Industry”, February 2002. Wells, 1999. G. Margaret Wells, “Handbook of Petrochemicals and Processes”, 2nd edition, Ashgate, 1999
Start ohne Landebahn Von Jochen Ahlswede, BASE © BASE Klimakrise, Vermüllung der Meere, Giftstoffe in der Umwelt – unsere Zeit ist voll von Beispielen, wie der Erfindergeist der Menschheit Technologien mit negativen Folgewirkungen hervorgebracht hat. Dabei sind Technologien an sich weder „gut“ noch „schlecht“, entscheidend ist der gesellschaftliche Umgang mit ihnen. Dazu gehört insbesondere die Frage: Steigt man einfach in vielversprechend klingende Technologien ein und „hebt ab“, ohne zu wissen, wo man wieder landen kann? Oder plant man schon vor dem Start die Route, wägt genau ab und stellt sicher, dass es am Ziel auch eine Landebahn gibt? Es war gerade acht Jahre her, dass die zerstörerische Kraft der Atombombe auf die japanischen Städte Nagasaki und Hiroshima gelenkt worden ist und das Ausmaß dieser neuen Technologie offenbarte, als der damalige US-amerikanische Präsident Dwight D. Eisenhower 1953 in einer Vollversammlung der Vereinten Nationen seine Rede „Atoms for Peace – Atome für den Frieden“ hielt. Während insbesondere die Bevölkerung Europas noch die Nachwehen des Zweiten Weltkrieges spürte und sich bereits eine neue Teilung der Welt anbahnte, sollte eine Technologie der Zerstörung in eine Technologie des Wachstums und Wohlstands verwandelt werden. Diese nur allzu verständliche Hoffnung auf eine friedliche Nutzung der Atomkraft für Energieerzeugung, Transport, Landwirtschaft und Medizin war weithin spürbar und breitete sich rasch aus. Die gewünschte Entkoppelung von militärischer und ziviler Nutzung von Atomenergie gelang jedoch nicht, denn die Zahl der weltweit verfügbaren Atomwaffen stieg in exorbitante Höhen (über 64.000 im Jahr 1986), während der Bau von Atomkraftwerken weit hinter den ursprünglichen Plänen zurückblieb. Was jedenfalls in der Rückschau zu kurz kam, war eine systematische und ehrliche Vorausschau der Risiken und Lösbarkeit von Problemen dieser Technologie. Eine Landebahn, insbesondere für die hochgefährlichen Hinterlassenschaften, gibt es bis heute nicht. Die Vision in den fünfziger Jahren: Atomkraft zur Energieversorgung, für Transport, Landwirtschaft und Medizin. In fast allen Lebensbereichen sollte sie für Wachstum und Wohlstand sorgen. Skulptur auf einer Ausstellung des US-amerikanischen Unternehmens Union Carbide ca. 1955. Sie stellt die Halbwertszeit verschiedener Elemente dar. © © Three Lions/Getty Images Dabei gingen Gesellschaften durchaus sehr unterschiedlich mit der Atomtechnologie um. Es bildeten sich sehr spezifische „Energiekulturen“, also wechselseitige Verknüpfungen von Atomenergie mit gesellschaftlicher Ordnung, Werten und Kultur, heraus. Die Geschichte der Atomkraft in Deutschland zeigt in vielen Etappen, wie sich soziale, politische, und wirtschaftliche Gegebenheiten unterschiedlich auf nationale nukleare Energiekulturen auswirken. In Deutschland hat sich das Verhältnis zur Atomenergie demnach wechselvoll gestaltet: Die Ansätze einer militärischen Verwendung wurden schon Ende der 1950er eingestellt, dafür aber die zivile Nutzung von staatlicher Seite stark vorangetrieben. Heute stehen wir kurz vor der Beendigung der Atomenergie, was nicht zuletzt auf jahrzehntelanges gesellschaftliches Engagement zurückgeht. Festzuhalten ist aber auch: Eine Landebahn, also die Lösung für die nukleare Entsorgung, ist auch in Deutschland noch weit entfernt. Erlebt die Geschichte der Atomkraft aktuell eine Renaissance oder wird ihr letztes Kapitel geschrieben? Die deutsche Perspektive scheint klar, der Ausstieg aus der Atomkraft ist beschlossen und der primäre Fokus liegt nun auf dem sicheren Umgang mit den Hinterlassenschaften – von der Stilllegung der letzten Atomkraftwerke bis zu der sicheren Endlagerung hochradioaktiver Abfälle . Deutschland ist im Begriff eine post-nukleare Energiekultur zu entwickeln, die die Zukunft in erneuerbaren Energieträgern sieht. Einen ähnlichen Weg gehen neben Deutschland auch andere Staaten, in Europa etwa Italien, Spanien, Belgien und die Schweiz. Ihnen gegenüber stehen andere Länder, die weiter Atomkraft betreiben und Reaktortechnologien weiter entwickeln möchten ( z. B. China, Russland, Indien & Frankreich). Global gesehen sind die Staaten, die keine Atomkraft nutzen, aber deutlich in der Überzahl: Die Hälfte der OECD -Staaten betreibt keine Atomkraftwerke, weltweit sind es 83 % aller Staaten. Ob eine signifikante Zahl derjenigen Staaten, die sich für einen Einstieg aktuell interessieren, in absehbarer Zeit eigene Atomkraftwerke zum Laufen bringen werden, darf vor dem Hintergrund der historischen Erfahrungen hinterfragt werden. Auch sehen wir hier komplexe Motivlagen, in denen nicht selten zivile und militärische Interessen miteinander verschränkt sind. Eine aktuell hoch umstrittene Position ist, dass Atomkraft als CO2-arme Energiequelle einen Beitrag zur Bekämpfung des Klimawandels leisten und damit als nachhaltige Energiegewinnung eingestuft werden könne. In diesem Kontext entfachte auch die neu aufgelegte Debatte um verschiedene Entsorgungsoptionen von Atommüll: Während die Überlegungen zur Lagerung in der Tiefsee oder zur Entsorgung im All schon vor langer Zeit verworfen wurden, werden angebliche Recyclingmethoden weiter diskutiert – obwohl die Forschung an einem „geschlossenen Brennstoffkreislauf“ auch 70 Jahre nach Einführung der Atomkraft zu keinem Erfolg geführt hat. Es ist vielleicht der Zeitpunkt gekommen, nüchtern zu reflektieren, dass bestimmte Landebahnen einfach nicht existieren, bevor man sich entscheidet, den Anschlussflug zu nehmen. Diesen Artikel finden Sie in der Broschüre zur Geschichte der Endlagerung Atomausstieg in Deutschland: Viele Aufgaben in der nuklearen Sicherheit bleiben Label: Broschüre Atomausstieg in Deutschland: Viele Aufgaben in der nuklearen Sicherheit bleiben Informationen zu dem Autor Jochen Ahlswede
Alternative reactor concepts A number of reactor concepts are being developed around the world as future alternatives to conventional nuclear power plants. A report commissioned by BASE analyses the development status, safety and regulatory framework of these concepts. Study on alternative reactor concepts BASE has commissioned a research project to analyse current developments in alternative reactor concepts that differ significantly from light water reactors. The term "so-called 'novel' reactor concepts" is used to denote them in this report. Various reactor concepts that are seen as future alternatives to conventional nuclear power plants are currently being developed around the world. They are often summarised under collective terms such as "4th generation reactors", "novel reactor concepts" or "advanced reactors". These alternative reactors are characterised by the fact that they can provide electricity much more cheaply than conventional nuclear power plants, are safer than conventional nuclear power plants, should be able to incubate new nuclear fuel, should be able to recycle radioactive waste, produce less waste, are less suitable for producing fissile material for nuclear weapons. But will the alternative reactor concepts live up to expectations? BASE has commissioned an expert report to investigate this question, and to analyse and evaluate the concepts regarding development status, safety and regulatory framework. You can view an interim report on the expert opinion here. Here you can find the summary of the study results . Historical development Research into a variety of different reactor concepts based on the use of different nuclear fuels, coolants, moderator materials and neutron spectra has been conducted since the 1940s and 1950s. Light water reactors, which include the pressurised and boiling water reactors operated in Germany, were the most successful in industrial terms. Around 90% of the global output of nuclear power plants is currently generated by light water reactors. Development of alternative reactor concepts As light water reactors also have shortcomings in terms of safety, fuel utilisation, efficiency and cost-effectiveness, interest in alternative concepts has been growing again for some time. These are often referred to as novel reactor types, but some of them are based on designs that have been under development for many decades and have not produced any commercially competitive construction lines to date. For this reason, the report commissioned by BASE refers to "so-called 'novel' reactor concepts". The Generation IV International Forum International efforts to develop alternative reactor concepts have been coordinated through the Generation IV International Forum (GIF) since 2001. The aim is to produce operational nuclear reactors of alternative technology lines with improved properties in the near future. Six different technology lines are being pursued: 1. Very High Temperature Reactor (VHTR) 2. Molten Salt Reactor (MSR) 3. Supercritical-water-cooled reactor (SCWR) 4. Gas-cooled fast reactor (GFR) 5. Sodium-cooled fast reactor (SFR) 6. Lead-cooled fast reactor (LFR) Other concepts are currently being developed outside the GIF's area of work, for example 7. Accelerator-driven subcritical reactor (Accelerator-driven Systems, ADS) Alternative technology lines 1) Very High Temperature Reactor (VHTR) While most conventional reactors (including the light water reactors operated in Germany) heat the water used as a cooling medium to temperatures of approx. 300°C, other reactor types operate at significantly higher temperatures. The high-temperature reactor is designed to reach temperatures of 750°C to over 1000°C. Such high temperatures allow for significantly higher efficiencies than other reactor types, i.e. a better yield when converting heat into electricity. Furthermore, the heat can alternatively be utilised for certain industrial processes such as the production of hydrogen. Very High Temperature Reactor © BASE How does the high-temperature reactor work? High-temperature reactor concepts use helium gas as a coolant instead of water. This allows the reactor to operate at lower pressure, making it more controllable at extremely high temperatures compared to conventional light water reactors. Uranium oxide or carbide is predominantly used as fuel. The fuel comes in small pellets that are encased in a protective shell. The pellets, in turn, are embedded in spheres or prismatic blocks of graphite, which serves as a moderator. These spheres or blocks represent the fuel elements. Coolant flows around them and absorbs the heat generated during the nuclear reaction. This heat can be used, for example, to heat water and drive a steam turbine. Advantages and disadvantages of high-temperature reactors? In addition to an increased efficiency and the generation of process heat at high temperatures, high-temperature reactors offer further advantages over conventional reactors. The design of the fuel elements and the helium cooling offer improved safety features. This means that additional safety systems can be used, some of which are not available in water-cooled reactors. Due to its design, the high-temperature reactor has a relatively low output in relation to the total volume of the reactor core. A core meltdown can, therefore, be ruled out. If the plant is suitably designed, natural uranium , thorium, plutonium or mixed oxides can also be used as fuel in addition to enriched uranium . However, the technology also has major disadvantages. The high temperature and the helium coolant pose a challenge in terms of selecting suitable materials. Gas-cooled reactors also often exhibit problems such as uneven cooling, high abrasion and dust formation as well as an increased risk of fire in the event of water or air ingress. This can lead to the release of radioactive substances . Due to the high content of radioactive graphite, the final disposal of spent fuel elements is estimated to be significantly more cost-intensive compared to conventional fuel elements. Development status of high-temperature reactors Gas-cooled high-temperature reactors have been the subject of research since the 1960s. Prototype plants based on this concept (the pebble bed reactors in Jülich and Hamm-Uentrop) were also developed in Germany. At the end of the 1980s, both plants were shut down due to various technical problems, and the technology was gradually abandoned in Germany. Other high-temperature reactor projects have been and continue to be developed in the UK, the USA , Japan and France, among others. A project in South Africa, which was based on AVR Jülich technology, was paused indefinitely due to technical difficulties and a lack of funding in 2010. A high-temperature experimental reactor, the HTR-10, which is also based on the pebble bed design , has been in operation in the People's Republic of China since 2003. Two further high-temperature reactors of the HTR-PM type there reached criticality as demonstration plants in autumn 2021. A similar project in the USA was discontinued before a prototype reactor was even built, but research on the high-temperature reactor concept is ongoing there. A general trend towards moderately high operating temperatures of 700-850°C can be observed in current developments. To date, there is no high-temperature reactor for commercial power generation in operation. 2.) Molten Salt Reactor – (MSR) Fuel in nuclear reactors is usually used in solid form as so-called fuel rods. In molten salt reactors, however, the fuel is molten salt that is pumped through the reactor. Molten Salt Reactor © BASE How does the molten salt reactor work? The fuel is a mix of molten salts (fluorides and chlorides). The concentration of the fissile fuel can be adjusted very accurately via the selection of the salts and their mixing ratio. This allows the production of the exact concentration required to maintain a stable chain reaction. The temperatures in the molten salt are approx. 600-700°C. Controlled nuclear reactions that generate heat take place inside the reactor. This heat can be used to heat water vapour and power a turbine for electricity generation. What are the advantages and disadvantages of molten salt reactors? The safety concept of molten salt reactors is based on basic physico-chemical properties and requires less active safety technology than conventional light water reactors, for example. A central feature of the safety concept is to drain the molten salt into designated containers in the event of malfunctions, thus preventing any further chain reaction. In addition, molten salt reactors can integrate what is known as chemical treatment. The fission products and the composition of the fission products , the fuel and the salt mixture used can be optimised during operation in an additional system in the primary circuit (fuel processing system). In contrast to light water reactors, there is no increased pressure in the primary circuit of a molten salt reactor, which means that some accident scenarios can be ruled out. A major disadvantage of the molten salt reactor is the increased corrosion inside the pipe systems. The hot fuel-salt mix corrodes the metals in the reactor, thus limiting their service life. This problem is also the subject of current research and an important reason why, to date, molten salt reactors only exist as research or pilot plants. Some concepts for molten salt reactors advertise the fact that they can also recycle radioactive waste . The idea is that so-called transuranium elements, which are produced in the reactor during nuclear fission , as well as individual long-lived fission products can be specifically converted, i.e. transmuted. This has not yet been developed to the point where it is ready for use. According to the current state of research , however, it would not be possible to convert all of the radioactive waste . New fission products would also be generated. There would, thus, be no advantage in terms of the final storage strategy pursued in Germany. Depending on the specific design of the molten salt reactor concept, radioactive residues would be produced that differ from those of previous light water reactors. The entire disposal chain would have to be adapted, from the development of suitable conditioning processes and new containers to the requirements for interim and final storage of the radioactive residues. Development status of molten salt reactors Molten salt reactors were last operated in the USA in the 1950s and 1960s in the form of two experimental reactors. Research into the further development of this technology is currently underway in several countries. This research is at very different stages and includes concept studies as well as theoretical and experimental preliminary work. The development of an experimental reactor in China (TMSR-LF1) is the most advanced such concept. The commissioning of this reactor, which has been under construction since 2018, was approved by the Chinese authorities in summer 2022. 3.) Supercritical-water-cooled Reactor – (SCWR) The supercritical-water-cooled reactor is similar in structure to a boiling water reactor, but the pressure and temperature are such that the water does not boil; instead it reaches a supercritical state. The water circulates in a simple cooling circuit and is fed directly into the turbine. Supercritical-water-cooled Reactor © BASE How do supercritical-water-cooled reactors work? The supercritical-water-cooled reactor is a nuclear reactor that uses supercritical water as a working medium. The water is always in a supercritical state, i.e. it has a temperature of over 374°C and a pressure of at least 221 bar. No phase transitions take place above this point, known as the ‘critical point’ of water, which means that the water will no longer boil or condense. The structure of the reactor corresponds to that of a boiling water reactor . The water in the reactor core is heated in a simple cooling circuit, and then fed directly into the turbine. Unlike in a boiling water reactor , the water does not vaporise in supercritical state. The coolant has a higher density and can, thus, absorb the heat more efficiently and transport it away from the core. The core temperature is higher than that of boiling and pressurised water reactors, and the pressure is significantly higher than that of pressurised water reactors (usually a maximum of 160 bar). What are the advantages and disadvantages of a reactor cooled with supercritical water? The design of the reactor is simple and the efficiency is high (up to 45 % ). The special neutron spectrum of the supercritical light water reactor has fast neutrons as well as thermal neutrons. These cause long-lived radionuclides to be transmuted into shorter-lived ones, meaning that the spent nuclear fuel will radiate for less time. One disadvantage is that, similar to the boiling water reactor , the turbine gets radioactively contaminated through direct contact with the cooling water in the primary circuit. The pressure in the circuit ( approx. 250 bar) is very high, which is why the reactor pressure vessel and all other components of the primary circuit have to be thicker and more stable than in conventional light water reactors. Due to the high pressure, damage to the primary circuit also poses an increased risk . Development status of reactors cooled with supercritical water The operation of coal-fired power plants with supercritical water was first trialled in the 1950s and is now standard in new construction projects. Research into the transfer of the concept to nuclear technology has been intensified since the 1990s. However, materials used in modern coal-fired power plants do not have sufficient corrosion resistance for use in the nuclear sector. Further relevant research and development into cladding and structural materials and safety functions is needed. At present, the most advanced designs come from China, the EU , Japan, Canada, Korea, Russia and the US. On the whole, however, development is at an early stage. There are currently no plans for a prototype system. 4.) Gas-cooled Fast Reactor – (GFR) Fast neutrons are used to split the nuclear fuel in gas-cooled fast reactors. These neutrons have a higher kinetic energy than the thermal neutrons used in light water reactors. Similar to high-temperature reactors, helium is used as a coolant. This facilitates particularly high outlet temperatures and increased efficiency compared to conventional light water reactors. Gas-cooled Fast Reactor © BASE How does a gas-cooled fast reactor work? The design of the reactor is similar to that of a classic pressurised water reactor (light water reactor). But instead of water, helium (other gases are also conceivable) is used as a coolant. Uranium, thorium, plutonium or compounds thereof are used as fuel. Unlike high-temperature reactors, which work with moderated thermal neutrons like conventional light water reactors, the fuel in fast reactors is split with fast neutrons. This means that the use of a moderator is not necessary. The high operating temperature of around 850°C yields high efficiencies or can be utilised as process heat for industrial processes. What are the advantages and disadvantages of gas-cooled fast reactors? The envisaged design of the reactor is relatively simple, and there is no need for a moderator at all. The use of unmoderated neutrons leads to transmutation, resulting in less long-lived nuclear waste. Moreover, helium as a coolant can be heated to very high temperatures and does not become radioactive itself. This is the drawback of fast gas-cooled reactors, as helium is not very thermally conductive, which results in increased requirements for cooling the reactor core during operation and immediately after shutdown. Due to the high temperatures, only particularly heat-resistant materials can be used. An additional stress arises from the high neutron flux. The unmoderated fast neutrons are more difficult to shield and can penetrate further into materials than moderated neutrons. This impairs the service life of these materials. Development status of gas-cooled fast reactors Work on the fast gas-cooled reactor concept has been ongoing in the US and Germany since the 1960s, and later also in the UK and Japan. Since the 2000s, research has primarily been driven by France. So far, however, no helium-cooled fast reactor has been built and operated. Extensive research and development are still required, particularly to find suitable fuels and cladding and structural materials for the high-temperature design . In addition, many questions regarding the necessary safety systems and the safety and reliability of operation in general remain unanswered. Generally speaking, development is still at the applied research stage, with no existing prototype designs. Commercial utilisation for power generation or industrial applications is not foreseeable. 5.) Sodium-cooled Fast Reactor – (SFR) In sodium-cooled fast reactors, the nuclear fuel is split using fast neutrons. The reactor core is located in a cooling pool (so-called pool design), which is filled with liquid sodium. A secondary sodium circuit absorbs the heat from the primary sodium pool and conducts it out of the reactor vessel for use in power generation. Sodium-cooled Fast Reactor © BASE How does the sodium-cooled fast reactor work? The reactor core containing the fuel is located in a pool-type container filled with liquid sodium. Sodium is used for its high thermal capacity and good conductivity. Sodium does not boil during operation, so there is no elevated pressure in the reactor vessel. A heat exchanger inside the reactor vessel transfers the heat from the main circuit sodium to a secondary circuit, which also contains liquid sodium. From this secondary circuit, the heat is transferred to a water-bearing tertiary circuit that drives a turbine to generate electricity. In contrast to many other reactor concepts, fast reactors use unmoderated fast neutrons. They can produce additional fissile material from non-fissile isotopes such as uranium -238 or thorium-232 during breeding reactions. Following reprocessing , the fissile material produced in this way can be used as nuclear fuel . Another promise is the reduction of long-lived nuclear waste through transmutation, provided the reactor and fuel production are designed accordingly. What are the advantages and disadvantages of sodium-cooled fast reactors? Thanks to its excellent heat capacity, sodium can completely absorb the decay heat of the fuel elements even without circulation. If, for example, the cooling system should fail due to a power failure, a core meltdown would be passively prevented. In the event of a leak, less coolant will escape as the primary and secondary circuits operate without pressure. This should result in advantages in terms of safety. However, specific accident risks such as sodium leaks and fires must be considered. In the event of a coolant leak, it is necessary to prevent the highly reactive sodium from coming into contact with water and oxygen. This requires additional safety barriers . The system is complex and comparatively expensive, not least because it requires three cooling circuits. Earlier decades saw the possibility of incubating additional fuel in reactors (breeder reaction) as an advantage in some cases. However, due to the quantity of uranium deposits worldwide, there were no major economic advantages to such an application. In addition, depending on the configuration, weapons-grade plutonium is incubated in the reactor. This increases the risk of proliferation of nuclear weapons-grade material. With regard to the transmutation of long-lived waste materials, it must be noted that no such application has yet been developed to operational maturity. According to the current state of research , it would not be possible to transmute all of the radioactive waste . In addition, new fission products would be produced. This would therefore not be an advantage for the final storage strategy pursued in Germany, for example. Development status of sodium-cooled fast reactors The sodium-cooled fast reactor was one of the first reactor concepts in the early days of civil nuclear energy utilisation. Sodium-cooled breeder reactors were and are in operation in several countries. One such experimental facility, the KNK -II, was operated at the German research centre in Karlsruhe from 1977 to 1991. The Kalkar nuclear power plant, which was based on the same technology, was never put into operation due to safety concerns. Three fast sodium-cooled reactors are currently in commercial operation in Russia and China, and others are under construction in both countries and in India. Research and development of reactor concepts for this technology line is ongoing in a large number of countries around the world. The "Generation IV International Forum" has given top priority to this development project. The plan is to press ahead with the development of an advanced fast sodium-cooled reactor with the option of transmuting particularly long-lived waste materials, and to move on to a trial phase in the 2020s. China, EURATOM , France, Japan, Korea, Russia and the USA are contributing to the research and development work. 6.) Lead-cooled Fast Reactor – (LFR) The lead-cooled fast reactor is based on nuclear fission using fast neutrons. Lead or a lead-bismuth alloy is used as the coolant. The primary circuit is designed to allow the liquid metal to circulate by natural convection. This means that there is no need for circulation pumps on the primary side. Electricity is generated by a turbine powered in the secondary circuit. Lead-cooled Fast Reactor © BASE How does the lead-cooled fast reactor work? The reactor has a pool design , which means that the reactor core is located in a pool-shaped container. The pool is filled with the coolant, which is either liquid lead or a lead-bismuth alloy. The metallic coolant does not boil during operation, meaning that normal pressure prevails in the reactor vessel. The heating and cooling processes in the various zones of the reactor vessel allow the coolant to circulate naturally without the need for pumps. A heat exchanger transfers the heat to a secondary circuit where a turbine is run to generate electricity. Depending on the design , the fast neutrons used in the reactor can incubate additional fuel (breeding reaction) or potentially cause a reduction in long-lived waste materials through transmutation. What are the advantages and disadvantages of lead-cooled fast reactors? Like other fast reactors, the lead-cooled fast reactor can be used to incubate additional fuel or to convert long-lived waste material into shorter-lived or stable material by means of transmutation. The reactor core can be designed in such a way that the amount of heat generated per volume is relatively low. The lead alloy can dissipate all of the heat via an automatically adjusted circulation system; no primary circuit pumps are needed. The primary circuit also operates completely without pressure. In addition, lead has very good shielding properties against the ionising radiation emitted by the fuel. One disadvantage of the system is that the lead-bismuth alloy must always be kept at temperatures above its melting point (min. 123 °C ). If not, it will solidify and the entire reactor will become unusable. The coolant must also be filtered at great expense. Lead and bismuth have very high densities, so the system requires stronger structures due to the enormous weight. Bismuth is also very rare and expensive. Development status of lead-cooled fast reactors A research project on lead-cooled fast reactors was already underway in the USA in the 1940s, but was discontinued in 1950. In the Soviet Union, reactors of this type were developed to power submarines, and were used until 1996. The 1990s/2000s witnessed a renewed interest in exploring the concept. Research and development projects are underway in the USA, China, Russia, South Korea and the EU, among others. Problems that still remain unresolved include the minimisation of corrosion and erosion risks due to the liquid metal circulating in the primary circuit and the filtration of the coolant. How does the high-temperature reactor work? High-temperature reactor concepts use helium gas as a coolant instead of water. This allows the reactor to operate at lower pressure, making it more controllable at extremely high temperatures compared to conventional light water reactors. Uranium oxide or carbide is predominantly used as fuel. The fuel comes in small pellets that are encased in a protective shell. The pellets, in turn, are embedded in spheres or prismatic blocks of graphite, which serves as a moderator. These spheres or blocks represent the fuel elements. Coolant flows around them and absorbs the heat generated during the nuclear reaction. This heat can be used, for example, to heat water and drive a steam turbine. Advantages and disadvantages of high-temperature reactors? In addition to an increased efficiency and the generation of process heat at high temperatures, high-temperature reactors offer further advantages over conventional reactors. The design of the fuel elements and the helium cooling offer improved safety features. This means that additional safety systems can be used, some of which are not available in water-cooled reactors. Due to its design, the high-temperature reactor has a relatively low output in relation to the total volume of the reactor core. A core meltdown can, therefore, be ruled out. If the plant is suitably designed, natural uranium , thorium, plutonium or mixed oxides can also be used as fuel in addition to enriched uranium . However, the technology also has major disadvantages. The high temperature and the helium coolant pose a challenge in terms of selecting suitable materials. Gas-cooled reactors also often exhibit problems such as uneven cooling, high abrasion and dust formation as well as an increased risk of fire in the event of water or air ingress. This can lead to the release of radioactive substances . Due to the high content of radioactive graphite, the final disposal of spent fuel elements is estimated to be significantly more cost-intensive compared to conventional fuel elements. Development status of high-temperature reactors Gas-cooled high-temperature reactors have been the subject of research since the 1960s. Prototype plants based on this concept (the pebble bed reactors in Jülich and Hamm-Uentrop) were also developed in Germany. At the end of the 1980s, both plants were shut down due to various technical problems, and the technology was gradually abandoned in Germany. Other high-temperature reactor projects have been and continue to be developed in the UK, the USA , Japan and France, among others. A project in South Africa, which was based on AVR Jülich technology, was paused indefinitely due to technical difficulties and a lack of funding in 2010. A high-temperature experimental reactor, the HTR-10, which is also based on the pebble bed design , has been in operation in the People's Republic of China since 2003. Two further high-temperature reactors of the HTR-PM type there reached criticality as demonstration plants in autumn 2021. A similar project in the USA was discontinued before a prototype reactor was even built, but research on the high-temperature reactor concept is ongoing there. A general trend towards moderately high operating temperatures of 700-850°C can be observed in current developments. To date, there is no high-temperature reactor for commercial power generation in operation. How does the molten salt reactor work? The fuel is a mix of molten salts (fluorides and chlorides). The concentration of the fissile fuel can be adjusted very accurately via the selection of the salts and their mixing ratio. This allows the production of the exact concentration required to maintain a stable chain reaction. The temperatures in the molten salt are approx. 600-700°C. Controlled nuclear reactions that generate heat take place inside the reactor. This heat can be used to heat water vapour and power a turbine for electricity generation. What are the advantages and disadvantages of molten salt reactors? The safety concept of molten salt reactors is based on basic physico-chemical properties and requires less active safety technology than conventional light water reactors, for example. A central feature of the safety concept is to drain the molten salt into designated containers in the event of malfunctions, thus preventing any further chain reaction. In addition, molten salt reactors can integrate what is known as chemical treatment. The fission products and the composition of the fission products , the fuel and the salt mixture used can be optimised during operation in an additional system in the primary circuit (fuel processing system). In contrast to light water reactors, there is no increased pressure in the primary circuit of a molten salt reactor, which means that some accident scenarios can be ruled out. A major disadvantage of the molten salt reactor is the increased corrosion inside the pipe systems. The hot fuel-salt mix corrodes the metals in the reactor, thus limiting their service life. This problem is also the subject of current research and an important reason why, to date, molten salt reactors only exist as research or pilot plants. Some concepts for molten salt reactors advertise the fact that they can also recycle radioactive waste . The idea is that so-called transuranium elements, which are produced in the reactor during nuclear fission , as well as individual long-lived fission products can be specifically converted, i.e. transmuted. This has not yet been developed to the point where it is ready for use. According to the current state of research , however, it would not be possible to convert all of the radioactive waste . New fission products would also be generated. There would, thus, be no advantage in terms of the final storage strategy pursued in Germany. Depending on the specific design of the molten salt reactor concept, radioactive residues would be produced that differ from those of previous light water reactors. The entire disposal chain would have to be adapted, from the development of suitable conditioning processes and new containers to the requirements for interim and final storage of the radioactive residues. Development status of molten salt reactors Molten salt reactors were last operated in the USA in the 1950s and 1960s in the form of two experimental reactors. Research into the further development of this technology is currently underway in several countries. This research is at very different stages and includes concept studies as well as theoretical and experimental preliminary work. The development of an experimental reactor in China (TMSR-LF1) is the most advanced such concept. The commissioning of this reactor, which has been under construction since 2018, was approved by the Chinese authorities in summer 2022. How do supercritical-water-cooled reactors work? The supercritical-water-cooled reactor is a nuclear reactor that uses supercritical water as a working medium. The water is always in a supercritical state, i.e. it has a temperature of over 374°C and a pressure of at least 221 bar. No phase transitions take place above this point, known as the ‘critical point’ of water, which means that the water will no longer boil or condense. The structure of the reactor corresponds to that of a boiling water reactor . The water in the reactor core is heated in a simple cooling circuit, and then fed directly into the turbine. Unlike in a boiling water reactor , the water does not vaporise in supercritical state. The coolant has a higher density and can, thus, absorb the heat more efficiently and transport it away from the core. The core temperature is higher than that of boiling and pressurised water reactors, and the pressure is significantly higher than that of pressurised water reactors (usually a maximum of 160 bar). What are the advantages and disadvantages of a reactor cooled with supercritical water? The design of the reactor is simple and the efficiency is high (up to 45 % ). The special neutron spectrum of the supercritical light water reactor has fast neutrons as well as thermal neutrons. These cause long-lived radionuclides to be transmuted into shorter-lived ones, meaning that the spent nuclear fuel will radiate for less time. One disadvantage is that, similar to the boiling water reactor , the turbine gets radioactively contaminated through direct contact with the cooling water in the primary circuit. The pressure in the circuit ( approx. 250 bar) is very high, which is why the reactor pressure vessel and all other components of the primary circuit have to be thicker and more stable than in conventional light water reactors. Due to the high pressure, damage to the primary circuit also poses an increased risk . Development status of reactors cooled with supercritical water The operation of coal-fired power plants with supercritical water was first trialled in the 1950s and is now standard in new construction projects. Research into the transfer of the concept to nuclear technology has been intensified since the 1990s. However, materials used in modern coal-fired power plants do not have sufficient corrosion resistance for use in the nuclear sector. Further relevant research and development into cladding and structural materials and safety functions is needed. At present, the most advanced designs come from China, the EU , Japan, Canada, Korea, Russia and the US. On the whole, however, development is at an early stage. There are currently no plans for a prototype system. How does a gas-cooled fast reactor work? The design of the reactor is similar to that of a classic pressurised water reactor (light water reactor). But instead of water, helium (other gases are also conceivable) is used as a coolant. Uranium, thorium, plutonium or compounds thereof are used as fuel. Unlike high-temperature reactors, which work with moderated thermal neutrons like conventional light water reactors, the fuel in fast reactors is split with fast neutrons. This means that the use of a moderator is not necessary. The high operating temperature of around 850°C yields high efficiencies or can be utilised as process heat for industrial processes. What are the advantages and disadvantages of gas-cooled fast reactors? The envisaged design of the reactor is relatively simple, and there is no need for a moderator at all. The use of unmoderated neutrons leads to transmutation, resulting in less long-lived nuclear waste. Moreover, helium as a coolant can be heated to very high temperatures and does not become radioactive itself. This is the drawback of fast gas-cooled reactors, as helium is not very thermally conductive, which results in increased requirements for cooling the reactor core during operation and immediately after shutdown. Due to the high temperatures, only particularly heat-resistant materials can be used. An additional stress arises from the high neutron flux. The unmoderated fast neutrons are more difficult to shield and can penetrate further into materials than moderated neutrons. This impairs the service life of these materials. Development status of gas-cooled fast reactors Work on the fast gas-cooled reactor concept has been ongoing in the US and Germany since the 1960s, and later also in the UK and Japan. Since the 2000s, research has primarily been driven by France. So far, however, no helium-cooled fast reactor has been built and operated. Extensive research and development are still required, particularly to find suitable fuels and cladding and structural materials for the high-temperature design . In addition, many questions regarding the necessary safety systems and the safety and reliability of operation in general remain unanswered. Generally speaking, development is still at the applied research stage, with no existing prototype designs. Commercial utilisation for power generation or industrial applications is not foreseeable. How does the sodium-cooled fast reactor work? The reactor core containing the fuel is located in a pool-type container filled with liquid sodium. Sodium is used for its high thermal capacity and good conductivity. Sodium does not boil during operation, so there is no elevated pressure in the reactor vessel. A heat exchanger inside the reactor vessel transfers the heat from the main circuit sodium to a secondary circuit, which also contains liquid sodium. From this secondary circuit, the heat is transferred to a water-bearing tertiary circuit that drives a turbine to generate electricity. In contrast to many other reactor concepts, fast reactors use unmoderated fast neutrons. They can produce additional fissile material from non-fissile isotopes such as uranium -238 or thorium-232 during breeding reactions. Following reprocessing , the fissile material produced in this way can be used as nuclear fuel . Another promise is the reduction of long-lived nuclear waste through transmutation, provided the reactor and fuel production are designed accordingly. What are the advantages and disadvantages of sodium-cooled fast reactors? Thanks to its excellent heat capacity, sodium can completely absorb the decay heat of the fuel elements even without circulation. If, for example, the cooling system should fail due to a power failure, a core meltdown would be passively prevented. In the event of a leak, less coolant will escape as the primary and secondary circuits operate without pressure. This should result in advantages in terms of safety. However, specific accident risks such as sodium leaks and fires must be considered. In the event of a coolant leak, it is necessary to prevent the highly reactive sodium from coming into contact with water and oxygen. This requires additional safety barriers . The system is complex and comparatively expensive, not least because it requires three cooling circuits. Earlier decades saw the possibility of incubating additional fuel in reactors (breeder reaction) as an advantage in some cases. However, due to the quantity of uranium deposits worldwide, there were no major economic advantages to such an application. In addition, depending on the configuration, weapons-grade plutonium is incubated in the reactor. This increases the risk of proliferation of nuclear weapons-grade material. With regard to the transmutation of long-lived waste materials, it must be noted that no such application has yet been developed to operational maturity. According to the current state of research , it would not be possible to transmute all of the radioactive waste . In addition, new fission products would be produced. This would therefore not be an advantage for the final storage strategy pursued in Germany, for example. Development status of sodium-cooled fast reactors The sodium-cooled fast reactor was one of the first reactor concepts in the early days of civil nuclear energy utilisation. Sodium-cooled breeder reactors were and are in operation in several countries. One such experimental facility, the KNK -II, was operated at the German research centre in Karlsruhe from 1977 to 1991. The Kalkar nuclear power plant, which was based on the same technology, was never put into operation due to safety concerns. Three fast sodium-cooled reactors are currently in commercial operation in Russia and China, and others are under construction in both countries and in India. Research and development of reactor concepts for this technology line is ongoing in a large number of countries around the world. The "Generation IV International Forum" has given top priority to this development project. The plan is to press ahead with the development of an advanced fast sodium-cooled reactor with the option of transmuting particularly long-lived waste materials, and to move on to a trial phase in the 2020s. China, EURATOM , France, Japan, Korea, Russia and the USA are contributing to the research and development work. How does the lead-cooled fast reactor work? The reactor has a pool design , which means that the reactor core is located in a pool-shaped container. The pool is filled with the coolant, which is either liquid lead or a lead-bismuth alloy. The metallic coolant does not boil during operation, meaning that normal pressure prevails in the reactor vessel. The heating and cooling processes in the various zones of the reactor vessel allow the coolant to circulate naturally without the need for pumps. A heat exchanger transfers the heat to a secondary circuit where a turbine is run to generate electricity. Depending on the design , the fast neutrons used in the reactor can incubate additional fuel (breeding reaction) or potentially cause a reduction in long-lived waste materials through transmutation. What are the advantages and disadvantages of lead-cooled fast reactors? Like other fast reactors, the lead-cooled fast reactor can be used to incubate additional fuel or to convert long-lived waste material into shorter-lived or stable material by means of transmutation. The reactor core can be designed in such a way that the amount of heat generated per volume is relatively low. The lead alloy can dissipate all of the heat via an automatically adjusted circulation system; no primary circuit pumps are needed. The primary circuit also operates completely without pressure. In addition, lead has very good shielding properties against the ionising radiation emitted by the fuel. One disadvantage of the system is that the lead-bismuth alloy must always be kept at temperatures above its melting point (min. 123 °C ). If not, it will solidify and the entire reactor will become unusable. The coolant must also be filtered at great expense. Lead and bismuth have very high densities, so the system requires stronger structures due to the enormous weight. Bismuth is also very rare and expensive. Development status of lead-cooled fast reactors A research project on lead-cooled fast reactors was already underway in the USA in the 1940s, but was discontinued in 1950. In the Soviet Union, reactors of this type were developed to power submarines, and were used until 1996. The 1990s/2000s witnessed a renewed interest in exploring the concept. Research and development projects are underway in the USA, China, Russia, South Korea and the EU, among others. Problems that still remain unresolved include the minimisation of corrosion and erosion risks due to the liquid metal circulating in the primary circuit and the filtration of the coolant. Further information on transmutation Partitioning and transmutation
Das Projekt "Commercial process outline for crystalline silicon thin film solar cells and modules" wird vom Umweltbundesamt gefördert und von Fraunhofer-Institut für Solare Energiesysteme durchgeführt. General Information: Thin film technologies to fabricate solar cells offer a high potential for a breakthrough in production cost since they consume less materials and ease the introduction of mass production techniques, as compared to the currently dominating wafer-based silicon technology. One of the most promising of these thin film approaches is the crystalline silicon thin film cell. A consortium has been formed by partners from industry and from research organisations to investigate the potential of the new technology. The main goals are: - to define a cell concept appropriate to an industrial product - to show the feasibility of essential process steps - to perform a careful economic process evaluation In this project, only the high temperature approach for the silicon deposition will be discussed, and for economic reasons only chlorosilanes are discussed as silicon source. This limits the substrate materials to those that can withstand temperatures of higher than 1000 C, and which are chemically stable in contact with silicon at this high temperature. Furthermore, it has been decided to focus mainly on substrate materials based on silicon. This can be silicon itself, crystallised in form of sheets, or it can be a ceramic material based on silicon oxides, nitrides, or carbides. Expected achievements are the demonstration of: - an appropriate substrate and a low-cost fabrication technique - a fast and cost-effective deposition technique for silicon films - a cell technology which is compatible with mass fabrication - interconnection and encapsulation schemes for these new cells. An important feature of the research is the inclusion of a thorough economic evaluation. The Consortium is confident to be able to deliver data for an in-depth comparison of the new technology with other thin-film options, but also with the conventional thick silicon technique. It is the intention of this proposed work to direct research and development in the field of the crystalline silicon thin film solar cells towards the industrial perspectives. Prime Contractor: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., Institut für Solare Energiesysteme; Freiburg im Breisgau; Germany.
Das Projekt "Silicon kerf loss recycling (SIKELOR)" wird vom Umweltbundesamt gefördert und von Helmholtz-Zentrum Dresden-Roßendorf e.V., Institut für Sicherheitsforschung durchgeführt. Solar energy direct conversion to electricity is expanding rapidly to satisfy the demand for renewable energy. The most efficient commercial photovoltaic solar cells are based on silicon. While the reuse of feedstock is a severe concern of the photovoltaic industry, up to 50% of the valuable resource is lost into sawdust during wafering. Presently, the majority of silicon ingots are sliced in thin wafers by LAS (loose abrasive sawing) using slurry of abrasive silicon carbide particles. The silicon carbide is not separable from the silicon dust in an economical way. The newer FAS (fixed abrasive sawing) uses diamond particles fixed to the cutting wire. It is expected that FAS will replace LAS almost completely by 2020 for poly/mono-crystalline wafering. The intention of the proposed project is to recycle the FAS loss aiming at a sustainable solution. The main problem is the large surface to volume ratio of micron size silicon particles in the kerf loss, leading to formation of SiO2 having a detrimental effect on the crystallisation. The compaction process developed by GARBO meets the requirements of a reasonable crucible-loading factor. Overheating the silicon melt locally in combination with optimised electromagnetic stirring provides the means to remove SiO2. The technology developed by GARBO removes the organic binding agents, leaving about 200 ppm wt diamond particle contamination. If untreated, the carbon level is above the solubility limit. Formation of silicon carbide and precipitation during crystallisation is to be expected. The electromagnetic mixing, in combination with the effective means to separate electrically non-conducting silicon carbide and remaining SiO2 particles from the silicon melt by Leenov-Kolin forces and the control of the solidification front, is the proposed route to produce the solar grade multi-crystalline silicon blocks cast in commercial size in a unified process.
Das Projekt "High density power electronics for FC- and ICE-Hybrid Electric Vehicle Powertrains (HOPE)" wird vom Umweltbundesamt gefördert und von Siemens AG durchgeführt. Objective: The project HOPE is addressing power electronics. It is based on previous EU research projects like the recently finished FW5 HIMRATE (high-temperature power modules), FW5 PROCURE (high-temperature passive components), and MEDEA+ HOTCAR (high-temperature control electronics) and other EU and national research projects. The general objectives of HOPE are: Cost reduction; meet reliability requirements; reduction of volume and weight. This is a necessity to bring the FC- and ICE-hybrid vehicles to success. WP1 defines specifications common to OEM for FC- and ICE-hybrid vehicle drive systems; Identification of common key parameters (power, voltage, size) that allows consequent standardisation; developing a scalability matrix for power electronic building blocks PEBBs. The power ranges will be much higher than those of e.g. HIMRATE and will go beyond 100 kW electric power. WP2 works out one reference mission profile, which will be taken as the basis for the very extensive reliability tests planned. WP3 is investigating key technologies for PEBBs in every respect: materials, components (active Si- and SiC switches, passive devices, sensors), new solders and alternative joinings, cooling, and EMI shielding. In WP4 three PEBBs will be developed: HDPM (high density power module) which is based on double side liquid cooling of the power semiconductor devices; IML (power mechatronics module), which is based on a lead-frame technology; and SiC-PEBB inverter (silicon carbide semiconductor JFET devices instead of Si devices). WP5 develops a control unit for high-temperature control electronics for the SiC-PEBBs. Finally WP6 works on integrating the new technologies invented in HOPE into powertrain systems and carries out a benchmark tests. All the results achieved in HOPE will be discussed intensively with the proposed Integrated Project HYSIS where the integration work will take place. It is clear from the start that many innovations are necessary to meet the overall goal.
| Origin | Count |
|---|---|
| Bund | 110 |
| Type | Count |
|---|---|
| Ereignis | 1 |
| Förderprogramm | 103 |
| Text | 4 |
| unbekannt | 2 |
| License | Count |
|---|---|
| geschlossen | 3 |
| offen | 104 |
| unbekannt | 3 |
| Language | Count |
|---|---|
| Deutsch | 109 |
| Englisch | 15 |
| Resource type | Count |
|---|---|
| Archiv | 3 |
| Datei | 4 |
| Dokument | 4 |
| Keine | 34 |
| Webseite | 73 |
| Topic | Count |
|---|---|
| Boden | 57 |
| Lebewesen & Lebensräume | 43 |
| Luft | 53 |
| Mensch & Umwelt | 110 |
| Wasser | 31 |
| Weitere | 110 |