Feasibility in the light of decay heat is also confirmed to be practicable, as the
decay heat of the fresh fuel material is 32 W/kgHM, which is less than 10 % of that
of the minor actinide (MA)-only fuel. Also, the decay heat of the fresh fuel
subassembly is approximately 240 W. Taking advantage of some cooling scheme
such as air flow, this fuel can be fabricated as a fuel pin bundle [21].
Moreover, the results also shows the profitability of the uranium-free TRU
metallic fuel fast reactor itself, because a 1-year operation of this 300 MWe
TRU-burning fast reactor burns 260 kg TRU, corresponding to the amount produced by a 1.2 GWe-year operation of a conventional LWR.
For all these reasons, the TRU-burning fast reactor using uranium-free TRU
metallic fuel is considered to be feasible. Further study such as reduction of burn-up
reactivity swing and trade-off of various countermeasures considering economic
aspect helps improve and optimize the core design in the next phase.
15.5 Conclusions
A TRU transmutation system associated with the uranium-free metallic fuel fast
reactor is a practical way to burn TRU with sustainability, fewer R&D needs, and a
simple system, because it can be used as both a TRU burner and a power supply
plant. Employment of pyro-processing for recycling reduces the burden of R&D
requirements, and introduction of a conventional fuel fabrication method and pyroprocessing allows less complex facilities.
In this study, two main issues related to the uranium-free core were investigated
and discussed to clarify the feasibility of a TRU-burning fast reactor cycle using
such a core: Doppler coefficient for reactor safety, and burn-up reactivity swing for
acceptable reactor operating cycle length.
The results show that the uranium-free fast TRU fast reactor core is viable
because those issues can be solved by TRU-Zr alloy fuel, BeO neutron moderator,
and reduced core height. Thanks to the BeO pins that function not only as a neutron
moderator but also as a diluent material, the 35 %Zr alloy fuel can be fabricated
without Am vaporization because its melting point is maintained below 1,200
C,
the temperature that causes Am vaporization during injection casting fuel fabrication. Moreover, the decay heat of the fresh fuel is considered to be an acceptable
level for the fuel fabrication. Also, a 1-year operation of this 300 MWe core burns
the TRU that is produced by 1.2 GWe-year operation of a conventional LWR.
In conclusion, the prospect of a TRU-burning fast reactor cycle using uraniumfree metallic fuel was confirmed. Further study, not only to improve core performances but also to develop a recycling process associated with this uranium-free
system, which is currently under way, promotes realization of the system.
Open Access This chapter is distributed under the terms of the Creative Commons Attribution
Noncommercial License, which permits any noncommercial use, distribution, and reproduction in
any medium, provided the original author(s) and source are credited.
166
K. Ishii et al.
decay heat of the fresh fuel material is 32 W/kgHM, which is less than 10 % of that
of the minor actinide (MA)-only fuel. Also, the decay heat of the fresh fuel
subassembly is approximately 240 W. Taking advantage of some cooling scheme
such as air flow, this fuel can be fabricated as a fuel pin bundle [21].
Moreover, the results also shows the profitability of the uranium-free TRU
metallic fuel fast reactor itself, because a 1-year operation of this 300 MWe
TRU-burning fast reactor burns 260 kg TRU, corresponding to the amount produced by a 1.2 GWe-year operation of a conventional LWR.
For all these reasons, the TRU-burning fast reactor using uranium-free TRU
metallic fuel is considered to be feasible. Further study such as reduction of burn-up
reactivity swing and trade-off of various countermeasures considering economic
aspect helps improve and optimize the core design in the next phase.
15.5 Conclusions
A TRU transmutation system associated with the uranium-free metallic fuel fast
reactor is a practical way to burn TRU with sustainability, fewer R&D needs, and a
simple system, because it can be used as both a TRU burner and a power supply
plant. Employment of pyro-processing for recycling reduces the burden of R&D
requirements, and introduction of a conventional fuel fabrication method and pyroprocessing allows less complex facilities.
In this study, two main issues related to the uranium-free core were investigated
and discussed to clarify the feasibility of a TRU-burning fast reactor cycle using
such a core: Doppler coefficient for reactor safety, and burn-up reactivity swing for
acceptable reactor operating cycle length.
The results show that the uranium-free fast TRU fast reactor core is viable
because those issues can be solved by TRU-Zr alloy fuel, BeO neutron moderator,
and reduced core height. Thanks to the BeO pins that function not only as a neutron
moderator but also as a diluent material, the 35 %Zr alloy fuel can be fabricated
without Am vaporization because its melting point is maintained below 1,200
C,
the temperature that causes Am vaporization during injection casting fuel fabrication. Moreover, the decay heat of the fresh fuel is considered to be an acceptable
level for the fuel fabrication. Also, a 1-year operation of this 300 MWe core burns
the TRU that is produced by 1.2 GWe-year operation of a conventional LWR.
In conclusion, the prospect of a TRU-burning fast reactor cycle using uraniumfree metallic fuel was confirmed. Further study, not only to improve core performances but also to develop a recycling process associated with this uranium-free
system, which is currently under way, promotes realization of the system.
Open Access This chapter is distributed under the terms of the Creative Commons Attribution
Noncommercial License, which permits any noncommercial use, distribution, and reproduction in
any medium, provided the original author(s) and source are credited.
166
K. Ishii et al.