Conceptual Design Study of JSFR (3) - Reactor Cooling System

Japan Sodium-Cooled Fast Reactor (JSFR) is an advanced loop-type reactor generating the electricity of 1500 MWe. The two-loop reactor cooling system is adopted to enhance the plant economics. An intermediate heat exchanger (IHX) and a steam generator (SG) are installed per loop. The primary pump is integrated with an IHX into a single vessel to eliminate a middle-leg piping connecting a pump and an IHX. The sodium-water reaction accidents in the event of a SG tube failure are considerably reduced by adopting double-walled tubes. The material of SG tube is high Cr-based steel, which is resistant to high temperature and has high thermal conductivity, which leads to reduce the heat transfer area. The decay heat removal system (DHRS) consists of two primary reactor auxiliary cooling systems (PRACS) and a direct reactor auxiliary cooling system (DRACS). The heat exchanger of the PRACS is located in the integrated IHX with pump, and that of the DRACS is located in the reactor vessel. The DHRS is the cooling system utilizing natural circulation. The DHRS equipment can be operated under fully passive conditions without need for pumps and blowers to maintain the core cooling function after a reactor shutdown. The large temperature difference between the core inlet and outlet can ensure the core flow rate by buoyancy force. The natural circulation system increases reliability and reduces the construction cost. The target of JSFR is to be cost-competitive with light water reactors of similar size. (author)