Transient behaviour of 4.8 g/cc silicide fuel-(I) abnormal withdrawal of control rod during a start-up of JMTR

The Japan Materials Testing Reactor (JMTR) loaded the 4.8 g/cc silicide fuel for the core conversion from the high to the low enrichment (<20 wt%). In the experiment, the reactivity insertion of 0.35%Δk/k/s caused by the abnormal withdrawal of the control rod at the start-up of the JMTR was assumed. The value was about twice the EUREKA-2 computer code used for licensing. As a result, the test specimen (4.8 g/cc silicide fuel) had the peak cladding surface temperature of 137 ± 3°C. The test specimen did not fail by quench mechanism because the time to quench (tq) was 0.11 s and the temperature drop ΔT was 28°C. Usually the quench failure occurs at the rapid tq (<0.13 s) and the high ΔT (>94°C). The safety margin of the JMTR against the accident induced by the abnormal withdrawal of control rod was assured.

Keywords: transient behaviour, silicide fuel, abnormal withdrawal, control rods, JMTR, Japan Materials Testing Reactor, quench failure, temperature drop, time to quench, departure from nucleate boiling, DNB, EUREKA-2, nuclear reactors, nuclear energy, nuclear power