Preliminary neutronic design study of RCCA and GRCA utilized in LEUC FCM loaded PWR

The TRISO based FCM fuel concept is an attractive option from accident tolerance viewpoint to be used in LWRs. Study of various Physics aspects of FCM loaded PWR is of great importance and interest. In the Present study, a new neutronic design of the rod cluster control assembly (RCCA) and grey rod cluster assembly (GRCA) in a modified 13 x 13 array low enriched Uranium Carbide (LEUC) FCM assembly are proposed. The new RCCA and GRCA assemblies are comprised of 8-rod lets, having increased rod diameter compared with standard PWR rod let. A three-dimensional model of 3 x 3 fuel assembly arrangement is used for the calculation of control assemblies integral and differential worth against standard operating conditions. New proposed RCCA design with Aic as absorber has the integral and differential worth very close to standard 24-rod let RCCA of 17 x 17 solid UO₂ fuel assembly. GRCA with Tungsten as primary absorber has the lower worth compared to reference GRCA of 24-rod let. Impact of partially loaded RCCA on axial and radial power distributions is also studied and compared with reference assembly. The power peaking factors for axial and radial distributions are found to be less than that of reference assembly. The proposed designs are expected to provide adequate shutdown margin and power-maneuvering capability when used in FCM based full core design. (Author)