COMPLETE DOCUMENT (1862 kb) - OECD Nuclear Energy Agency

As a part of MA nuclear data evaluation, the analysis of a 237 Np sample irradiated in JOYO
has been performed. Additional irradiation test of 237 Np, 241 Am, 243 Am and 244 Cm samples in JOYO was
started in August, 1994.
Measurements of keV-neutron capture cross-sections of RE nuclides ( 147 Sm, 148 Sm, 150 Sm,
140 Ce, 141 Pr, 153 Eu, 143 Nd, 145 Nd) have been performed to evaluate the accuracy of the nuclear data
libraries using the 3-MeV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the
Tokyo Institute of Technology [152].
2.3.6 Interaction between plutonium incineration and minor actinide production
2.3.6.1 Present day PWRs
If present day PWRs could be licensed to accept 100% MOX containing depleted U, the
balance of Pu consumption would be around 60 to 70 kg/TWhe during successive recyclings, but with
concomitant production of minor actinides arising from 8 to 20 kg/TWhe. However, for high burn-ups
in the range of 50 GWd/tHM, the number of plutonium recyclings in MOX assemblies with depleted
uranium support is liable to be limited to two or three due to the degradation of certain safety-related
coefficients, and particularly of the coolant void reactivity coefficient, which tends to become positive
locally when the plutonium content substantially exceeds 12%.
2.3.6.2 Other alternatives
Other alternatives have been investigated, based on the use of PWRs, but with design changes
intended to limit the Pu content of the MOX assemblies, and hence to restore the safety and reliability of
multi-recycling.
High moderation reactors (HMRs)
3.
High moderation reactors (HMRs) have a moderation ratio (moderator volume/fuel volume) of
Compared with a standard PWR (in which the ratio is 2), the enhanced moderation helps to
lower the Pu content of the MOX loaded with each recycle (one-third in the first recycle) and to improve
Pu consumption per TWhe.
Thus the consumption of Pu would increase from about 70 kg/TWhe in the first recycle to
nearly 110 kg/TWhe at equilibrium, but the production of minor actinides would rise from 10 kg/TWhe
to nearly 34 kg/TWhe.
The Pu content would be stabilised around 20%, which is relatively high, requiring further
physical feasibility studies for this type of reactor.
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