Shutdown / emergency cooling system for a 2400 MW{sub TH} supercritical CO{sub 2}-cooled direct-cycle GFR

The Gas-cooled Fast Reactor (GFR) is one of the concepts under investigation for possible future deployment as part of the Generation-IV program. The reference GFR design is a high-temperature (850 deg. C core outlet) helium-cooled design. A 2400 MW{sub th} direct supercritical CO{sub 2} (S-CO{sub 2})-cooled plant is under investigation at MIT supported by a DOE NERI grant which would serve as a lower-temperature alternative to the reference GFR. This design offers the same high thermodynamic efficiency ({approx}48%) as the helium-cooled design, but at a much lower core outlet temperature of 650 deg C, thus circumventing the materials problems involved in operating at very high temperatures. The plant utilizes a Brayton recompression cycle at a maximum pressure of 20 MPa, which is very simple and compact with a single shaft and no inter-coolers. The work presented in this paper deals primarily with evaluation of a Shutdown/Emergency Cooling System (SCS/ECS) for the MIT design. This system consists of 4 x 50% capable hybrid active/passive loops utilizing blowers to remove decay heat during shutdown or to provide emergency cooling in the event of a Loss of Coolant Accident (LOCA). Natural circulation is evaluated at various post- LOCA backup pressures. Two routes aremore » identified by which coolant may bypass the core during post-LOCA decay heat removal; one is via duct breaks in the case of rupture of both hot and cold legs, and the other is through PCS loops once turbomachinery has stopped. Although the SCS/ECS performs well in natural circulation without accounting for core bypass, alternate coolant paths are shown to be significant enough to warrant implementation of a highly reliable active cooling systems for this design in future work. (authors)« less