A New Safety Principle for the SLOWPOKE Reactor

Abstract

Slowpoke-2 (LEU core) is a pool type nuclear reactor with a maximum thermal power of 20 kW. It uses a pelletized uranium oxide fuel (19.9% enrichment) and provides a useful high neutron flux in the order of 1012 n.cm-2s-1. The key safety features built into the reactor design are the strictly limited amount of excess reactivity and the negative reactivity feedback characteristics, which provides a demonstrably safe self-limiting power excursion response to large reactivity insertions. However, the limited amount of excess reactivity also limits the continuous prolong reactor operation at full power. With a 3.7 mk excess reactivity, the reactor can operate for about one day at the full power, 20 kW, before this excess activity is lost due to temperature effects and Xe poisoning.A new safety concept is proposed in this paper to extend the continuous operation time to months by increasing the excess reactivity from 4 mk to 6 mk. This new concept has been demonstrated using a Matlab/simulink model of Slowpoke-2.