[3F11-16] Improving Resilience of Nuclear Structure

[3F12] Development of Failure Mitigation Technologies for Improving Resilience of Nuclear Structures

(16) Effectiveness Evaluation Methodology of the Measures for Improving Resilience at Ultra-High Temperatures

*Yuichi Onoda¹, Kenichi Kurisaka¹, Hidemasa Yamano¹ (1. Japan Atomic Energy Agency)

Keywords:measures for improving resilience, ultra-high temperatures, loss of heat removal systems after reactor shutdown, accident sequences, core damage frequency

We invented an effectiveness evaluation method of the measures for improving resilience by quantifying the event tree focusing on the accident sequence that leads to an ultra-high temperature state due to loss of heat removal systems in a sodium-cooled fast reactor and by evaluating the reduction rate of core damage frequency before and after the introduction of measures for improving resilience. If the conditional success probability of measures for improving resilience is tentatively set to 0.81, the reduction rate of core damage frequency for all accident sequences leading to loss of heat removal systems becomes 19%. By taking measures to improve resilience, the core damage frequency can be reduced to the order of 1.0x10^-8 (1/reactor year).