Fuel assembly with inert matrix fuel rods as reload options for Laguna Verde NPP

Abstract

Four different fuel assembly reload options were studied for Unit 1 at the Laguna Verde Nuclear Power Plant (LVNPP) in Mexico. The purpose was to design a fuel assembly as a mixture of UO 2 and weapons grade plutonium in an inert matrix. This assembly design has a 10 × 10 geometry array, containing 42 PuO 2–CeO 2 fuel rods, 34 UO 2 fuel rods and 16 UO 2–Gd 2O 3 fuel rods. This assembly design is equivalent to those not containing plutonium and already designed for LVNPP-1. The neutronic design and nuclear data bank generation of the two types of fuel assemblies, with and without plutonium, were performed with CASMO code. The steady state reactor core simulation was performed with SIMULATE code, part of the Core Management System (CMS). Fuel rod cladding material was considered the same for both the UO 2 and inert matrix fuel rod. The rod to rod pitch was kept the same in the fuel assembly design, but the pin diameter is smaller for the inert matrix fuel rod design. To determine the possible use of the proposed mixed fuel assembly for a BWR fuel reload, three possible reload schemes were considered. Four reload schemes proposed in this study. In the first case, the base reload pattern, 116 new UO 2 fuel assemblies are exchanged for the full core reload. The second pattern replaced 36 IM and 80 UO 2 fuel assemblies. The third case introduced 80 IM and 36 UO 2 new fuel assemblies. In the last reload scheme, 116 IM fuel assemblies were placed instead of UO 2 fuel assemblies.