ACTIVE AND PASSIVE SAFETY CONTROL PERFORMANCE IN SUBCRITICAL, ACCELERATOR-DRIVEN NUCLEAR REACTORS

摘要

Traditional safety performance requirements for nuclear reactors have been developed for critical reactors, whose kinetics characteristics differ significantly from subcritical, accelerator-driven nuclear reactors. In a critical nuclear reactor, relatively small amounts of reactivity (negative or positive) can produce large changes in the fission rate. In subcritical reactors, the self-multiplication (k) decreases as the subcriticality (1-k) increases, and the responsiveness to small reactivity changes decreases. This makes subcritical nuclear reactors less responsive to positive reactivity insertions than critical reactors. Also, larger negative reactivity insertions are needed in subcritical reactors to shut down the fission chain if the neutron source remains. This paper presents the results from a computational analysis of the safety performance of subcritical, accelerator-driven nuclear reactors. Coupled kinetics and thermal-hydraulics models are used to quantify the effectiveness of traditional protection and control system designs in subcritical reactors. The analyses also quantify the role of inherent, passive reactivity feedback mechanisms in subcritical reactors. Computational results are used to develop conclusions regarding the most favourable and effective means for reactor control and protection in subcritical, accelerator-driven nuclear reactors.