Application of triplex SiC cladding to korean PWRs

Abstract

This study investigated the applicability of Triplex SiC cladding to Korean PWRs and feasibility of extension of maximum fuel discharge burnup. Since the Triplex Silicon carbide (SiC) cladding has a number of desirable properties, it is an emerging option to replace the current zircaloy cladding. This study covered core design with Triplex SiC cladding rods, evaluation of its performance during steady-state operation, evaluation of its integrity under accident conditions, and suggestion of the optimized Triplex cladding rod design for Korean PWRs.

The core design with the Triplex SiC cladding resulted in longer EFPD, higher discharge burnup, and higher peak burnup due to smaller neutron absorption cross-section of SiC. Most core design parameters were comparable to ZIRLO cladding. These results revealed that the application of the Triplex SiC cladding may have not such big challenges in terms of nuclear core design with extended burnup.

The results of performance analysis showed that the Triplex SiC cladding rod has good performance during steady-state operation. This study found that the slow rate of gap closure can lead to the delay of PCMI and the reduction of mechanical stress on the cladding. However, the lower thermal conductivity of the Triplex cladding after irradiation leads to higher fuel temperature, higher fission gas release, higher RIP, and greater fuel swelling.

This study suggested various options of improved rod designs based on the results of evaluations performed to confirm the integrity of the Triplex SiC cladding rod under accident conditions such as RIA and LBLOCA. The suggested Triplex rod designs were re-examined for confirming their performance at steady-state operation and their integrity under accident conditions. As a result, Triplex SiC cladding rod design with the best performance was selected: the Triplex SiC cladding rod with 20 inch plenum length and 10% central void pellet. The steady-state performance and integrity...