Resonance Interaction Effect between Hot Sample and Cold Core in Analysis of Doppler Effect Measurement

The resonance interaction effect between hot sample and adjacent cold core was evaluated in a small sample 238U Doppler effect measurement. For this analysis a collision probability code with an ultra-fine group structure PEACO-X was developed. The previously measured Doppler effect reactivity coefficients at FCA are systematically analyzed by using the PEACO-X code. The results were compared with the conventional calculation results using the SLAROM code. From these results, it was shown that this effect depends on the background cross section for 238U in a core, and also depends on the radius and density of the sample. When this resonance interaction effect is taken into account, the calculated Doppler reactivity worths becomes larger than those using the conventional method and the sample dependency of calculation disappeared. The reliability of Doppler effect calculation was significantly improved.