Comparative study of pressurised water reactor fuel designs

Abstract

This bachelor's thesis investigates different pressurized water reactor fuel assembly designs by both literature-based comparison and reactor physics simulations performed using the Serpent code. Selected vendors are Westinghouse, Framatome, TVEL, Korean Nuclear Fuel, and Mitsubishi. The literature section discusses the development of these fuel designs and compares representative assembly parameters to highlight their main mechanical, geometric, and material differences. Comparison parameters such as lattice type, fuel rod count, pin pitch, pellet, and cladding dimensions are drawn from publicly available sources.

Simulations are simplified to two-dimensional infinite lattices, with nominal temperature and moderator density fixed at a common value. The models include fresh uranium dioxide, guide tubes filled with water, and no control rods inserted. To improve the fairness of the comparison, the fuel compositions are normalized using APR1400 as the reference case by equalizing both U-235 and U-238 atoms per assembly area. The main comparison parameters are the infinite multiplication factor and the assembly power peaking factor (APPF). The multiplication factor illustrates the reactivity reserves, indicating energy potential, while APPF presents the uniformity of the power distribution.

Simulation results for the unpoisoned case produced a similar multiplication factor for all designs, with k∞ values in descending order: APR1400, AP1000, and VVER1000. Assembly power peaking factor (APPF) values for the unpoisoned cases had more differences in descending order: APR1400, VVER1000, and AP1000. Introducing burnable absorbers decreased the multiplication factor while increasing the APPF value across all designs. APR1400 had the most visible decrease in k∞ value, changing the ranking to AP1000, VVER1000, and APR1400. Even though the ranking for APPF stayed the same, the most visible change occurred in the VVER1000 model.