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Transmutations of Actinides in Fusion-Fission Hybrids – a Model Nuclear Synergy ?

FUNFI'2011 Varenna 12-15.09.11. Transmutations of Actinides in Fusion-Fission Hybrids – a Model Nuclear Synergy ?. S tefan Taczanowski Faculty of Energy and Fuels AGH Univ ersity of Science & Technology Cracow 30 059, Poland e-mail: s taczanowski@ gmail . com. AGH UST Cracow

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Transmutations of Actinides in Fusion-Fission Hybrids – a Model Nuclear Synergy ?

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  1. FUNFI'2011 Varenna 12-15.09.11 Transmutations of Actinides in Fusion-Fission Hybrids – a Model Nuclear Synergy ? Stefan Taczanowski Faculty of Energyand Fuels AGH University of Science & Technology Cracow 30 059, Poland e-mail: staczanowski@gmail.com AGH UST Cracow Poland

  2. Presentation Overview Problems of Fusion Systems vs. Problems of Nuclear Energy (fission based) Analysis of selected properties of Fusion-Fission systems Results of calculations Conclusions AGH UST Cracow Poland

  3. Tritium Size of the Fusion device Material consumption Selected Problems of the Fusion Power 1. Energy Balance  Energy gain from Fusion: Plasma Q  Size of the Fusion device i.e. material inventory  capital cost 2. Material Problems  Radiation Damage  (DPA, Gas production, Plasma-wall interactions)  Tritium inventory  capital & maint. cost  maintenance cost  capital cost AGH UST Cracow Poland

  4. 10 m Tokamak (PPCS) PWR Mirror Sizes Tokamak vs. LWR and Mirror Tokamak size is giant, whereas a Mirror by size resembles rather an LWR But in social perception more important is that Fusion Systems threat with no”atomic bomb” type explosion AGH UST Cracow Poland

  5. Selected Problems of Nuclear Energy (fission based) One of the most important ones is: the Nuclear Waste i.e. Spent Nuclear Fuel In particular its recycling is difficult due to: 1) its increasing Minor Actinides (MAs) component, 2) adegradation of Pu - both with recycling due to the negative nuclear properties of MAs first of all of Transplutonics AGH UST Cracow Poland

  6. Selected Data ofActinideFissions ( delayed neutron fraction, n number of neutrons per fission, ηper absorption) Low values ofßfor transplutonics hinder use of them in significant quantities incritical systems

  7. Asking some questions Addressed to Fission Do we really need an exactly closed fuel cycle ? MAs recycling might be givenup ? Lack of uranium is not a threat in the near future But, to abandon recycling of great quantities of degraded Pu does not seem reasonable. For this purpose 14 MeV neutrons can be useful Addressed to Fusion Do we really need a fusion option – with 100% of fusion energy? Is not enough: fusion confined to be the driving-source ? (key role!) AGH UST Cracow Poland

  8. n/(j) Thus, the additional neutron and energy multiplicationis achieved in a saferway successive generations Properties of Fusion-driven Subcritical Systems The number of neutrons born per src.n. in a source-driven subcriticalsystem is notn= k/(1-k) [thus k=n/(n+1)] but: and thus the k-source is: ks>k ns>n for 14 MeV source  The point is that safety of the system depends on its remoteness from criticality 1 – k, not on 1 -ks Therefore a decrease in the plasma Q (energy gain by fusion) proves easier achievable Number of neutrons born from one 14 MeV neutron in successive generations vs. the generation number AGH UST Cracow Poland

  9. 30 Qp 20 10 0 k 1.0 0.0 0.2 0.4 0.6 0.8 The Plasma Q - k trade-off in Fusion-driven Systems at fixed gross power of system The burden of energy production is shifted from Fusion (plasma)-to-Fission (blanket) Earlier calculations have shown that in Mirror configuration about 5 fissions per source neutron can be achieved (> 1000 MeV/n) [IAEA TEC DOC-1626 (2009)] It signifies a reduction of needed energy gain from fusion by factor of several tens thus, the 14MeV neutron yield as well as the tritium demand At realistic values of k the requirements regarding plasma Qp can be significantly relaxed (to ~0.2) AGH UST Cracow Poland

  10. AGH UST Cracow Poland Properties of Fusion-driven Subcritical Systems Advantages of 14 MeV neutrons Share of fissioning in absorption cross-section of fissible actinides for 14 MeV and 0.8 MeV neutrons Superiority of 14 MeV neutrons over the 0.8 MeV ones, not mentioning2 main natural nuclides 232Th and 238U, is particularly distinct for 241Am, 243Amand for 236U –abundant in the spent fuel.

  11. X-section:  fission & tritium breeding zones keff = 0.89 void X-section:  keff = 0.95 Key Question of Fusion-Hybrid Safety The great advantage Fusion Reactor improbability of super prompt criticality must not be lost in Fusion-Hybrid Model of itsMelt-down Collapse  AGH UST Cracow Poland The assembly after collapse remains subcritical

  12. 1.5-6 [MeV g] sum Fusion reactor sum 1.0-6 Power density per source neut. Fusion-Driven Incinerator Fuel zone 1 Fuel zone 2 Fuel zone 3 Refl./ shield FW 0.5-6 g + x,a g + x,a neut 0 70 80 90 100 110 120 [cm] neut R Distribution of Nuclear Heating Both Systems: Pure Fusion and Fusion-Driven Incinerator are of the same power Nuclear heating inFusion-driven System as compared with the one in Fusion Reactor is much more uniform AGH UST Cracow Poland

  13. E-7 FR FDI DPA [arb. units] H E-8 He Reaction Rates per src. neut. E-9 E-10 E-11 70 80 R 90 [cm] 100 Radiation damage vs. system radius Both systems: the Fusion-driven Incinerator (FDI) and pure Fusion Reactor (FR) have the same power Neutron induced radiation damage in the FDI as compared with the one in FR proves much less intense AGH UST Cracow Poland

  14. Destruction Destruction Nuclides Inventories [kg] Production Destruction (net) Incin. mean time [yr] (total) (by fission) 5 - 565 2.8 115.4 112.6 24.4 190 91.2 33.6 - 57.6 23.5 4.2 3185 10.4 766.1 755.7 613.2 65 1831 152.7 180.9 28.2 79.7 4.6 781 101.1 269.1 168.0 202.5 48.4 784 44.0 60.2 16.2 24.4 4.6 - 1723 36.8 414.3 377.4 58.2 10 354.9 4.2 - 350.7** 3.5 93-Np-237 5.6 1390 36.3 284.4 248.2 36.3 94-Pu-238 Total 10460 830.0 2 128.0 1 298.1 1 065.7 94-Pu-239 94-Pu-240 94-Pu-241 94-Pu-242 95-Am-241 95-Am-242m 95-Am-243 Performance of Puand MA Incineration [kg/yr]* * at the BOC **approximate 237Np and 243Am are most converted, to 238Pu and 244Cm respectively The conversion of 237Np "poisons" Pu (nonproliferation) 241Am is most converted to 242mAm and 242gAm Transmutation can be satisfactory when its product is fissile (eg.242mAm). Incineration of Pu (no U in the system) and of 241Am is quite satisfactory AGH UST Cracow Poland

  15. CONCLUSIONS The proposed fusion-driven transmutation concept provides a feasible wayof radical reductionin necessary plasma Q of the fusion reactor to levels achievable in much smaller systems. It has been demonstrated that also the radiation damage can be radically softenedin the Fusion-driven System. E.g. the DPA and Plasma-Wall can be reduced at least by one order of magnitude whereas the gas production by factor of several tens. Similarly – the tritium questions /breeding, inventory, reprocessing/ can be also effectively relaxedin the above option. Further optimising studies are needed, thus the research is continued. Summarising, thedevelopment ofFusion can be significantly facilitated by its alliance with Fission. AGH UST Cracow Poland

  16. Thank you for your attention

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