Experimental study on reactivity worth for absorber material in high conversion light water reactor using FCA-HCLWR core fueled with enriched uranium.

Experimental study on reactivity worth for absorber material in HCLWR core has been carried out in a series of experiments using the Fast Critical Assembly (FCA) in Japan Atomic Energy Research Institute (JAERI). The central reactivity worth as well as the simulated control rod worth of B4C with different 10B content and of Hf was measured in FCA-HCLWR core fueled with enriched uranium. Both reactivity worths of B4C increase with 10B content. These increasing trends do not saturate to 90% enriched B4C. The Hf has the smaller reactivity worth than the 20% B4C. The experimental values are compared with the calculated ones which obtained from JENDL-2 data and the SRAC system. The calculation predicts well the dependence of reactivity worth on 10B content and underestimates the reactivity worth ratios of the Hf to the 20% B4C.