Implementation of Neutron Trap Passive System in GFR 2400 Fast Reactor Design

The paper investigates the implementation of neutron trap passive safety system within a Gas-cooled Fast Reactor (GFR2400). This concept was identified by the Generation IV International Forum as prospective fast reactor design, however the technical feasibility of this concept is questionable. Difficulties may arise during unprotected transient overpower and unprotected loss of flow scenarios. Therefore, the implementation of the neutron trap passive system at the periphery of the core may mitigate the consequences of these scenarios. The assumed passive actuation mechanism of the neutron trap is Curie point latch with ALNICO material, which Curie point temperature is 800 degrees C. Two unprotected transient scenarios are investigated, where the first assumes rapid withdrawal of one control rod assembly during normal operation and the response of the neutron trap passive system is observed. The second assumes continuous shutdown of one primary circuit blower from the total three blowers that are incorporated in the GFR 2400 design. In this case also the response of the passive system is investigated. The changes in hot channel temperature distributions are described and visualized in the paper. The analysis shows that the neutron trap passive system may mitigate negative consequences of these scenarios and its implementation may enhance the safety of the GFR 2400 reactor.