Performance of safety system of passive safety small reactor for distributed energy supply system

This paper presents the function and performance of the safety systems and load following behavior of a Passive Safety Small Reactor for Distributed energy system (PSRD). The PSRD is an integrated-type PWR adopting natural circulation and self pressurization in the primary system, with the reactor thermal power between 100 and 300 MW, aimed at supplying electricity to small grids, district heating, etc. In design of the PSRD, high priority is placed on the enhancement of safety, as well as the improvement of economy, so that the reactor can be sited close to energy demand areas. The safety enhancement is ensured by drastic reduction of the possibility of loss-of-coolant accidents (LOCAs) by limiting the primary pipe penetration only for the safety valve line, and adoption of a fully passive safety system with a water-filled containment and so on. The key features of the system are described together with the analyses for load following by the RETRAN-02 and for transient of a LOCA by the RELAP5. The analysis results have shown that the reactor responds smoothly to a typical load change with help of a rather large negative moderator density reactivity coefficient. In the transient of a LOCA, the water-filled containment functions very well to terminate the break discharge with the result that the core is always flooded with the water, and to limit the maximum containment pressure below 1 MPa. To optimize the initial gas volume of containment, a simplified analysis tool has been developed and verified by comparison with the RELAP5 analysis. (author)