Critical experiment and analyses for the conceptual design study of fast reactor equipped with Li-6 reactivity control systems LEM and LIM

The operator-free fast reactor concept RAPID-L has been designed. It introduced innovative reactivity control systems, LEM, LIM and LRM, instead of the control rods. The systems utilize 95 % enriched liquid ⁶Li as the neutron absorber. To evaluate the reactivity effects of those systems, a critical experiment was carried out in the FCA facility of JAERI since ⁶Li has not been used as a neutron absorbing material in conventional fast reactors. The FCA XXI-1 core was constructed to simulate the neutron spectrum of RAPID-L. The reactivity worth of the 95 % enriched ⁶Li sample and an axial distribution of it were measured and analyzed. The calculation with JENDL-3.2 overestimates the measured reactivity worth by ∼2 % in the core region and underestimates it by 3∼8 % in the blanket region. (author)