CFD study of CNPP fuel assembly bottom nozzle with anti-debris filter

In a nuclear power reactor fuel integrity must be ensured for its safe and smooth operation by minimizing the fuel rod damages. One of the main recognized reasons of fuel failure is due to interaction of metallic debris with fuel rods. On average one damaged fuel rod is found per reactor per cycle. The debris present in coolant is entrapped in the spacer grid and produces debris fretting which ultimately damages the fuel rod cladding. Anti-debris filter (ADF) is being used at the bottom of perforated plate to decrease the damage ratio of fuel rods in CNPP (Chashma Nuclear Power Plant) fuel assemblies. CFD study is conducted to analyze the hydraulic characteristics of the ADF nozzle of CNPP fuel assembly. Computational domain consists of 1/8th geometry (bottom nozzle, perforated plate and ADF). K-ε turbulence model with scalable wall function is used. Under and over power conditions of the reactor coolant pump are also simulated. The comparison of the simple bottom nozzle and ADF nozzle indicates the localized effects of ADF. Secondary flow distribution is not altered to a greater extent by presence of ADF.