Neutronic Analysis of the AP1000 Fuel Assembly with Accident Tolerant Cladding Materials

Abstract

An alternative material for fuel cladding was required to prevent oxidation caused by interacting with steam, leading to improvement in core integrity. This study analyzes reactor physics parameters of various cladding material candidates of Accident Tolerant Fuel (ATF) for Pressurized Water Reactor (PWR) such as SS-304 austenitic stainless steel, FeCrAl alloy, APMT alloy, and silicon carbide (SiC) ceramic. The neutronic parameters such as infinite multiplication factor (k-inf), neutron spectrum, and coefficient of reactivity due to fuel temperature (DTC), moderator temperature (MTC), and void (VCR) of each candidate material were then compared with ZIRLO as a standard cladding material of AP1000. k-inf calculated by SRAC2006 is also compared to Monte Carlo Code for various fuel assembly types. At the beginning of cycle (BOC), the 2.35% UO2 using SiC gives a higher kinf than ZIRLO at 937 pcm, while 4.45% UO2 with 88 IFBA & 9 PYREX at 796 pcm. FeCrAl, APMT, and SS-304 cladding gave a smaller k-inf compared to ZIRLO in the range of 11000-14000 pcm at 2.35% UO2 fuel assembly. The values of DTC, MTC, and VCR were still negative throughout the reactor operation which indicates that the inherent safety feature of alternative cladding was possible for this type of fuel assembly, especially for iron-based cladding material followed by an increase in fuel enrichment.