Reaction Rate Calculation in Fast Reactor Blanket Using Multiband Sn Theory

A new method was applied to calculation of reaction rates in blanket of LMFBR using the multiband S n theory. This procedure leads to the use of direction dependent total micro cross sections, which advances the penetration of neutrons into the blanket. Test calculation with RZ model of a prototype fast reactor shows that reaction rates tend to rise with the penetration into blanket compared to the conventional multigroup calculation: the maximum difference was about 3% for 238 U capture, 4% for 235 U fission, 4% for 239 Pu fission, and less than 1% for 238 U fission. This tendency shows the same direction as the difference observed between the continuous energy Monte Carlo method and the conventional method.