Nuclear Technology / Volume 159 / Number 1 / July 2007 / Pages 39-58
Technical Paper / Thermal Hydraulics
In this study, a new concept in reactor cavity cooling systems (RCCSs) for high-temperature gas-cooled reactors (HTGRs) is proposed. The proposed RCCS consists of both water pools and active air-cooling systems, in order to overcome the disadvantages of the weak cooling capability of the air-cooled RCCS and the complex cavity structures of the water-cooled RCCS. The cooling capability of the RCCS during normal operation and under accident conditions was evaluated on the basis of a series of experiments that were performed in a scaled test facility. The reactor vessel of the test facility was a 1/10 linear scaled model of a 265-MW pebble bed modular reactor (PBMR), and the RCCS of the test facility was designed to limit the volumetric-averaged reactor vessel wall temperature below the maximum permissible wall temperature of the prototype reactor. The experiments were conducted by simulating the heat released from the reactor vessel wall to the RCCS. The power was reduced by 1/100 to preserve the heat flux, and the timescale was reduced by 1/10 to preserve the stored energy per volume. In the normal operation tests, detailed information on the temperature distribution and heat removal fraction of the upper pool and side pool was obtained. In the loss of all forced convection accident test, the passive afterheat removal capability of the RCCS was evaluated. These experimental results will be used to validate the reactor safety analysis codes and to evaluate the feasibility of the water pool-type RCCS.