Performances of DHRSs in the KALIMER and the Sodium-cooled DFR

The sodium-cooled demonstration fast reactor (DFR) with the reference plant of the KALIMER is under the design by KAERI. One of the most important designs of the DFR is the Decay Heat Removal System (DHRS) for the safe and reliable decay heat removal. The safety grade DHRS of the KALIMER which is operated by natural circulation flow consists of a DHX (Decay Heat eXchanger), an AHX (Air Heat eXchanger), and piping system connecting two heat exchangers. In general, the place of DHX plays an important role in the determination of the size of the AHX because the temperature difference of the hot pool and the cold pool is about 150 .deg. C in a fast reactor. So the size of the AHX based on the cold pool temperature has to be much larger than that based on the hot pool temperature to remove the same capacity of heat. The DHRS of KALIMER is similar to the way of cooling by the hot pool because of using the flooded sodium from the hot pool although the DHX is in the cold pool. However, the DHRS is not available in accidents of which the sodium level in cold pool is below the DHX due to the running of pumps or which the overflow from the hot pool to the cold pool is not formed as the sodium level of the hot pool is lower than the location of a reactor barrel path for the overflow. In this paper, the thermal hydraulic behaviors of the DHRS of KALIMER for two postulated events are compared with the behaviors of the new DHRS which is conceptually designed for the DFR. For the comparison of the long-term cooling capability of both systems, a LOHS (Loss Of Heat Sink) and a reactor vessel leak were analyzed using two types of DHRS's using the MARSLMR system analysis code