Partitioning and Transmutation Current Developments – 2004 a Report from the Swedish Reference Group on P&T-Research
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Technical Report TR-04-15 Partitioning and transmutation Current developments – 2004 A report from the Swedish reference group on P&T-research Per-Eric Ahlström (editor), Svensk Kärnbränslehantering AB Sofie Andersson, Christian Ekberg, Jan-Olov Liljenzin, Mikael Nilsson, Gunnar Skarnemark Chalmers Tekniska Högskola Institutionen för material och ytkemi, Kärnkemi Jan Blomgren, Uppsala Universitet Institutionen för neutronforskning Marcus Eriksson, Waclaw Gudowski, Per Seltborg, Jan Wallenius Kungliga Tekniska Högskolan Institutionen för fysik, Kärn- och reaktorfysik Bal Raj Sehgal, Kungl Tekniska Högskolan Institutionen för energiteknik, Kärnkraftsäkerhet Svensk Kärnbränslehantering AB May 2004 Swedish Nuclear Fuel and Waste Management Co Box 5864 SE-102 40 Stockholm Sweden Tel 08-459 84 00 +46 8 459 84 00 Fax 08-661 57 19 +46 8 661 57 19 Partitioning and transmutation Current developments – 2004 A report from the Swedish reference group on P&T-research Per-Eric Ahlström (editor), Svensk Kärnbränslehantering AB Sofie Andersson, Christian Ekberg, Jan-Olov Liljenzin, Mikael Nilsson, Gunnar Skarnemark Chalmers Tekniska Högskola Institutionen för material och ytkemi, Kärnkemi Jan Blomgren, Uppsala Universitet Institutionen för neutronforskning Marcus Eriksson, Waclaw Gudowski, Per Seltborg, Jan Wallenius Kungliga Tekniska Högskolan Institutionen för fysik, Kärn- och reaktorfysik Bal Raj Sehgal, Kungl Tekniska Högskolan Institutionen för energiteknik, Kärnkraftsäkerhet May 2004 This report concerns a study which was conducted for SKB. The conclusions and viewpoints presented in the report are those of the authors and do not necessarily coincide with those of the client. A pdf version of this document can be downloaded from www.skb.se Preface This report has been written on behalf of the Swedish reference group for research on partitioning and transmutation. The reference group has been assembled by SKB and its members represent the research teams active in this field at Swedish universities. The group also has observers from the authorities SKI and SSI as well as from KASAM – see Appendix IV. The draft of the report has made been available for comments to the members and observers of the reference group. The authors are, however, responsible for the contents. Summary The research and development on methods for partitioning and transmutation (P&T) of long-lived radionuclides in spent nuclear fuel has attracted considerable interest during the last decade. The main objective of P&T is to eliminate or at least substantially reduce the amount of such long-lived radionuclides that has to go to a deep geological repository for final disposal. The radionuclides of main interest (concern) are those of the transuranium elements. These elements are formed in a nuclear reactor by one or more neutron captures in uranium atoms which then by subsequent radioactive decay are transformed to neptunium, plutonium, americium or curium. Even small amounts of elements heavier than curium are formed but these are of minor interest in this context. A few fission products (technetium-99, iodine-129) may also be of some interest for transmutation. The long-lived radionuclides can be transmuted to more short-lived or stable nuclides by the use of nuclear physics processes. In theory and on laboratory scale several such processes are possible. In practice so far only transmutation by irradiation with neutrons can be achieved in macroscopic scale. Neutrons can cause fission in the transuranium elements and this process will release a substantial amount of energy. Thus transmutation on large scale of the transuranium elements from spent nuclear fuel must be done in a device similar to a nuclear reactor. A prerequisite for transmutation by irradiation with neutrons is that the nuclides to be transmuted are separated (partitioned) from the other nuclides in the spent fuel. In particular the remaining uranium must be taken away unless you want to produce more plutonium and other transuranium elements. Separation of the various elements can at least in principle be achieved by mechanical and chemical processes. Currently there exist some large scale facilities for separation of uranium and plutonium from the spent fuel – reprocessing plants. These can, however, not separate the minor actinides – neptunium1, americium and curium – from the high level waste that goes to a repository. Plutonium constitutes about 90% of the transuranium elements in fuel from light water reactors. The objective of current research on partitioning is to find and develop processes suitable for separation of the heavier actinides (and possibly some long-lived fission products) on an industrial scale. The objective of current research on transmutation is to define, investigate and develop facilities that may be suitable for transmutation of the aforementioned long-lived radionuclides. The processes and facilities that could be implemented as results of such developments must meet very high standards of safety and radiation protection as well as have low environmental impact. They shall be economically viable and have good proliferation resistance. The large amount of energy released in the transmutation process should be 1 Note: Neptunium can be separated with uranium if a minor adjustment of the operating conditions is made in the industrial PUREX process. This possibility is not used today as it would give increased costs for purification of recovered uranium. 5 used in a proper way. In other words the processes and facilities must be acceptable to society. Research on P&T started already in the 1950ies when development of nuclear power gained momentum. In the subsequent years it was mainly tied to the development of the breeder reactor. As this development slowed down to a very low level in the early 1980ies the interest in P&T more or less disappeared. The renewed interest through the 1990ies has caused some expansion of the programmes in this field in particular on an international level. In Europe this is focused on the R&D-programmes of the European Union (EU). The EU so-called framework programmes (FWP) have established a strong link between the various national programmes within the union and also in some other European countries. Other large programmes are going on in Japan (OMEGA), USA and Russia. A review of the status of the efforts concerning P&T was published by SKB in 1998 /Enarsson 98/. This report summarises the work reported in the years 1998–2003 and tries to assess the prospects for future development of P&T as seen from a Swedish perspective. Systems for partitioning and transmutation During the last five years a number of system studies on P&T have been published. These studies give a good overview of the extensive work required for implementing P&T, of the relative large and complex system of facilities that are needed as well as of those problems that must be solved and the issues that must be addressed before such a system can be deployed. The first of these system studies was done by an expert group within OECD/NEA and was published in 1999 /NEA 99/. Important conclusions from this study were i.a. • The basic R&D for partitioning and transmutation requires long lead times and large investments in dedicated fast neutron devices, extensions of reprocessing plants and construction of remote controlled facilities for fuel fabrication. • Partitioning of long-lived radiotoxic elements from spent nuclear fuel can be made in extensions of existing reprocessing plants but requires a large amount of work to be developed from laboratory to industrial scale, • The transmutation with fast neutrons is more effective than in existing light water reactors. Transmutation of transuranium elements can best be achieved in fast reactors or in accelerator-driven systems with fast neutron spectrum. • Partitioning and transmutation will not eliminate the need for a deep geological repository for certain long-lived radioactive wastes from spent fuel. In the USA a certain interest arouse for transmutation using accelerator-driven systems in the early 1990ies. The centre of this interest was Los Alamos National Laboratory (LANL) that introduced the concept ATW – Accelerator-driven Transmutation of nuclear Waste. This gradually led to a broad study of ATW by the US Department of Energy at the request of US Congress. The study, published in the autumn of 1999 /DOE 99/, proposed a research programme for ATW that could be the start of a large scale concentration on such systems. Some parts of this work have started in particular those parts involving international co-operation. The programme as a whole has, however, not been accepted as a base for the US research on advanced fuel cycles or for future nuclear waste strategy. It was probably not intended as a complete 6 programme but more of an in depth evaluation of one of many possible scenarios for development of partitioning and transmutation. In 2003 USA announced the so-called Advanced Fuel Cycle Initiative (ACFI) /DOE 03/, which aims at a broad study of fuel cycles for future nuclear power reactors – also named Generation IV reactors. This initiative is planned to be pursued in three phases – phase 1 basic evaluation; phase 2 – proof of principles; phase 3 – proof of performance. The programme is broadly laid out and includes review of all current reactor concepts and systems (LWR, HTR, ADS, FR, aqueous based reprocessing and pyrochemical reprocessing, etc). Upon initiative from the research ministers in France, Italy and Spain a European technical working group – TWG – under chairmanship of Carlo Rubbia (Nobel laureate in physics and former Director General of CERN2) was formed in 1999. This working group proposed a plan for development of an accelerator-driven system (ADS) in Europe. The report from TWG was published in the spring of 2001 /TWG 01/. The ambition from the group was that the plan should form the base for continued EU- financed research work on ADS. In the plan the construction of a small experimental plant at 100 MW thermal power is proposed.