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Text optional: Institutsname Prof. Dr. Hans Mustermann www.fzd.de Mitglied der Leibniz-Gemeinschaft Partitioning & Transmutation Combined with Molten Salt.

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Presentation on theme: "Text optional: Institutsname Prof. Dr. Hans Mustermann www.fzd.de Mitglied der Leibniz-Gemeinschaft Partitioning & Transmutation Combined with Molten Salt."— Presentation transcript:

1 Text optional: Institutsname Prof. Dr. Hans Mustermann Mitglied der Leibniz-Gemeinschaft Partitioning & Transmutation Combined with Molten Salt Fast Reactor B. Merk Department Reactor Safety at Institute of Resource Ecology Helmholtz-Zentrum Dresden-Rossendorf EVOL Winter Scholl, Orsay 2013

2 Seite 2/25

3 Text optional: Institutsname Prof. Dr. Hans Mustermann Mitglied der Leibniz-Gemeinschaft Partitioning & Transmutation

4 Seite 4/25 Chances of P&T (Dreams)  transmutation goals are to eliminate 99.9% of the TRU and up to 95% of the long-lived fission fragments 99-Tc and 129-I  massive reduction radio toxicity  no final disposal required  solution of all waste problems  500-year final disposal  TRUs could disappear from the world  Volume reduction of the waste to 5%

5 Seite 5/25 The General Idea The major contribution to the long term activity and RTI is created by Pu and the minor actinides (Am & Cm) and their decay chains The long term activity and radio toxicity can be reduced significantly when it is possible to separate these elements from the waste and to transmute them

6 Seite 6/25 The Potential of P&T More Realistic  Volume reduction to ~30% mostly due to separation of Uranium  Over all activity in final disposal after years with P&T ~activity after without P&T  reduced hazard potential  observation time is fixed by law  Elimination of the risk of misuse of Pu from final disposal on the long term  Possibility for improved conditioning after partitioning  no early release of mobile fission products  reduced heat production after 70 to 100 years due to separation of Am  Elimination of decay chain products from actinides  P&T is a matter of inter-generational fairness

7 Seite 7/25 Requirements for Efficient P&T  efficient separation/reprocessing technology  acceptable solution for the fuel production  fast neutron spectrum for efficient transmutation Pu-242Am-243 radiative capture and fission XS

8 Seite 8/25 Requirements for Efficient P&T  efficient reprocessing technology  acceptable solution for the fuel production  fast neutron spectrum for efficient transmutation

9 Seite 9/25 Risks of P&T  fast reactor technology is required  multi recycling of minor actinides is needed  radiation risk and technological challenges in solid fuel production  fuel behavior of material with high Pu and minor actinide loading  challenges of fertile free solid fuel – production and reactor operation  safety of fast system cores with high minor actinide load  success depends on very efficient lanthanide ↔ actinide separation  short term proliferation risk due to Pu separation

10 Seite 10/25 Comments on Current Status of P&T  A major part is already demonstrated  Pu separation and MOX use is industrial technology for LWR  the already performed Pu recycling reduces the required final disposal site dimension by ~30%  Am separation and fuel production has been demonstrated on lab scale  transmutation of Am has been demonstrated in PHENIX  currently 1970ies technology is foreseen for transmutation (e. g. sodium cooled fast reactors)   special systems for transmutation could offer better performance (e. g. molten salt reactor)  current proliferation risk can and has to be controlled by safeguarding (IAEA)

11 Seite 11/25 The Fuel Cycle for P&T

12 Seite 12/25 Desired Characteristic for Efficient Transmutation  a high TRU content is required for efficient transmutation  no breeding is desired to avoid the built up of new TRU isotopes  long cycle time is required for efficient transmutation  long cycle time requires a small reactivity loss over cycle as design target for the core or a core design with high excess reactivity  small reactivity loss over cycle requires breeding of new fissile material, thus fertile material is essential  high excess reactivity has negative safety consequences, therefore a strong control system is needed  a high burnup is required for an efficient transmutation  very high Pu content tends to degrade the Pu – remember CAPRA  short out of core period and long in core residence time of the TRU fuel is required

13 Text optional: Institutsname Prof. Dr. Hans Mustermann Mitglied der Leibniz-Gemeinschaft Molten Salt Reactor in the View of Transmutation

14 Seite 14/25 Advantages of MSFR  fertile free fuel is no problem due to online re-fuelling  no challenging solid fuel production with high Am load and its irradiation in the reactor is required  no multi-recycling due to online salt cleanup  excellent safety due to strong negative feedback effects  possibility for the elimination of last transmuter problem

15 Seite 15/25 Fertile Free Fuel  very step burnup curve of fertile free fuel caused by rapid burning of fissile material  U-238:  less absorption in U-238  lower BOL Pu content  fertile free:  no absorption in fertile  significantly less BOL Pu content  significantly lower HM content

16 Seite 16/25 Fertile Free Fuel  very step burnup curve of fertile free fuel caused by rapid burning of fissile material  high excess reactivity would be required in solid fuel reactors to reach acceptable cycle time  high excess reactivity requires a strong control system   strong initiator for transient over power accidents caused by malfunction of control system  high Pu content tends to degrade Pu quality  breeding of higher Pu and MA isotopes  unknown reprocessing strategies for different inert matrix fuel types Solutions:  fast power reactors – isobreeder core, breeding compensates burnup and allows long cycle times, weak control assemblies, and breeding of fresh Pu  online re-fuelling compensates reactivity loss continuously

17 Seite 17/25 Pellets with High Am Content  Dust free production process is required  reduced losses  reduced contamination  Swelling of the fuel pellets, which decreases the pellet-cladding gap  Helium release into the plenum and high He production  Degradation of the thermal conductivity of the pellets, due to the presence of fission products and additional porosity  unknown reprocessing strategies for different inert matrix fuel types Solution:  avoid solid fuel production completely

18 Seite 18/25 The Cm Problem  Cm is always produced by breeding processes  Current strategy, wait and see  let the Cm decay to Pu  Cm is one of the major carriers of radiotoxicity  Fuel production is fairly unknown  Cm is highly complicated to handle due to the neutron production cause by spontaneous fission Solution:  avoid solid fuel production completely  don’t separate  don’t take it out of the reactor

19 Seite 19/25 Multi-Recycling  only a share of the TRUs is burnt (10-30%) in a cycle  long cooling time for MOX fuel assemblies  unknown reprocessing of transmutation fuel  repeated separation of Pu  possible proliferation risk  production of new transmutation fuel assemblies  repeated irradiation in the reactor Solution:  avoid multi-recycling at all

20 Seite 20/25 Safety of Fast Transmutation Systems  insertion of TRUs degrades the inherent feedback effects of fast reactors  limited amount of TRUs in critical reactors Solutions:  low TRU and especially Am content in critical reactors  critical fast reactors with enhanced feedback effects

21 Seite 21/25 Optimization of Fast Reactor Safety  feedback effects are an inherent safety mechanism in all nuclear reactors  Insertion of fine distributed moderating material  enhances the negative Doppler effect  reduces the positive sodium void effect  reduces the positive coolant effect  insertion of transmutation materials damps the feedback effects  compensation of effects caused by insertion of transmutation materials (Americium)  improved transmutation efficiency due to higher possible loading

22 Seite 22/25 Safety of Fast Transmutation Systems  insertion of TRUs degrades the inherent feedback effects of fast reactors  limited amount of TRUs in critical reactors Solutions:  low TRU and especially Am content in critical reactors  critical fast reactors with enhanced feedback effects  use of accelerator driven systems  use of fluid fuelled reactor  coincidence of fuel and coolant  any temperature increase leads to reduction of fuel amount in the core   very strong temperature feedback, comparable to LWR

23 Seite 23/25 Last Transmuter Problem Problem in the view of a phase out:  EOL configuration of the last loading is left over  when fuel is replaced assembly by assembly, there is always a not burnt leftover of TRUs Possible solution:  twofold lifecycle  successive replacement of fissile material in a MSFR  TRUs are burnt and Uranium can be feed into  solution of the proliferation problem

24 Text optional: Institutsname Prof. Dr. Hans Mustermann Mitglied der Leibniz-Gemeinschaft Challenges

25 Seite 25/25 Challenges of MSFR  lack of maturity of the general concept  missing transmutation optimized design  experience is only available for thermal MSRE system  missing safety approach for system with liquid fuel  safety concept for reactor wit co-located ‚reprocessing‘ facility  material damage of the inner structures due to irradiation  highly reactive salt requires special materials – nickel based alloys  nickel based alloys are very sensitive to Helium embrittlement caused by irradiation with thermal neutrons


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