Study on TRU transmutation by LMFBRs (II); Study on super long life core for TRU transmutation and influence of uncertainties of TRU cross sections

Yamaoka, Mitsuaki; not registered

TRU nuclides (Np, Am, and Cm) contained in the high level waste have extremely long-term radioactivity. They would be managed much more easily if transmuted in a short period. The present study deals with TRU transmutation by Fast Breeder Reactors (FBRs). The results are summarized below. (1)Study on a 300MWe Super Long Life Core for TRU Transmutation An FBR core loaded with TRU has a large potentiality of extending operation cycle length. Making use of the potentiality, a super long life FBR core loaded with TRU was studied aiming at continuous operation without refueling during plant life and efficient reduction of TRU nuclides. Core parameters were optimized with the electric power of 300MWe and analyses of nuclear and thermal characteristics were carried out. As a result, the burnup reactivity change of the optimized core for 34 years is very small (2.5% k/kk'). The power swing is also small, which resulted in satisfaction of the thermal design criteria. The amount of TRU transmuted during lifetime is about 5300Kg, which is equal to that 6 LWRs of 1000MWe produce during their lifetime. The Doppler coefficient (absolute value) is rather small because of TRU loading. Further study is needed on core kinetics from the view point of core safety and control. (2)Study on influence of uncertainties of TRU cross sections There are large uncertainties in TRU cross sections because of lack of experimental data. The influences of the uncertainties upon nuclear characteristics were evaluated for the super long life core and a large FBR core loaded with TRU of 5%. Sensitivity analysis on cross sections was carried out and uncertainties of nuclear characteristics were roughly evaluated. Based on the results, the TRU cross sections with large influences were identified.