Radiation Shielding Design of PWR Steam Generator

Abstract

Radiation safety and protection has key importance for safe nuclear power. Therefore one of the fundamental principles of Nuclear power plant design is to ensure the radiation safety of the workers and equipment. Proper shielding is required for environment and plant protection. An efficient and economical shield design of reactor components is of primary concern. Due to intense neutron flux in core, the reactor primary coolant is activated and acts as a radiation source throughout the primary loop of the reactor. The aim of this project is to study the coolant activation and provide radiation shield to this radiation source. The Chashma Nuclear Power Plant CHASNUPP unit-1 (C-1) is selected for this study. A detailed 3D model of steam generator of C-1 is developed employing shield design computer code MCBEND. The MCBEND computer program is dedicated radiation shield design computer code and employs the Monte Carlo techniques to simulate the radiation transport. Many Isotopes are formed through the activation of primary coolant but only Nitrogen-16 (N-16) activity is considered due to its significant production and half-life. The first step is to calculate the amount of N-16 production using analytical and Monte Carlo methods and compare with the FSAR results of C-1. The MCBEND simulated value is found as 4.10 MBq/g which is comparable to FSAR result of 4.59 MBq/g. The next step is to model homogenized steam generator source using MCBEND computer code and validate the shield design simulations against the FSAR values. For 80 cm Portland concrete shield thickness, MCBEND computer code simulates the dose rate of 0.1142 mSv/hr in comparison to FSAR value that is, 0.1mSv/hr for 80 cm of concrete. Design improvements are suggested on the basis of the validated model. On the employment of Iron Portland concrete, the shield thickness decreases from 80 cm to 27 cm. Similarly by adding Tungsten content to normal Portland concrete, the shield thickness even decreased to 75 cm for 5% W and 70 cm for 10% W-content.