Different materials used in neutron reflectors

Abstract

This Bachelor’s thesis focuses on neutron reflectors applied in nuclear power production. This research aims to find the most suitable material for use in the heavy baffle reflector type commonly applied in light-water reactors. The materials chosen are heavy water, nuclear graphite, beryllium, beryllium oxide and stainless steel. The materials are compared in identical spherical reactor core conditions using the Serpent reactor physics code. The various thicknesses chosen for the research are 25 cm, 61 cm and 150 cm. Simulations are conducted at 600 K and 900 K, similar to those in light-water and high-temperature reactors.

As a result, beryllium oxide tends to have overall greater efficiency at various thicknesses and temperatures. At a maximum researched thickness of 150 cm and temperature of 600 K, the best reflector is heavy water, with slightly better results than beryllium oxide. At the same thickness and a temperature of 900 K, the best reflector is graphite, with an overall efficiency less than 1% higher than beryllium oxide. Noticeably lower albedo was noted for the stainless steel reflector. The total reflection was not reached at a thickness of 150 cm. Despite the identical reactor core conditions, major fluctuations in the effective multiplication factor were noted. The relative uncertainty of the Monte Carlo simulations was below 1.9%. The mesh results represent the temperature distribution in the core with a reflector thickness of 61 cm. The results of this research mainly aligned with other similar studies conducted in the same area of interest.