Investigation of the role of ionising radiation on corrosion and related phenomena that occur in light water reactors

Abstract

The corrosion of materials used within Light Water Reactors (LWRs) can lead to release, transport and deposition of generated corrosion products. The build-up of these corrosion products is termed CRUD. CRUD build-up causes operational issues within reactor primary circuits affecting reactor safety and efficiency. Understanding the effects of radiation on corrosion and its related phenomena is essential when considering new build plants and lifetime extension programs. This work is part of a larger project by Rolls Royce PLC that aims to model the chemistry of PWR systems and is tasked with providing insight and experimental data of corrosion and CRUD behaviour under radiation conditions. This work investigated the effects of radiation on the corrosion of nuclear material and how corrosion products interact with products from the radiolysis of LWR coolant. Direct examination of the corrosion process under exposure to radiation is logistically difficult. This work reports the successful design, development and implementation of a High Temperature and High Pressure (HTHP) facility that can be used in conjunction with either a ɣ-radiation source or an accelerator providing heavy ion radiation. This work enables studies of both water radiolysis and corrosion in simulated LWR conditions. As far as the participants of this project are aware, this equipment is the only one of its kind that allows for the multifunctionality it gives. Results of the design and commission processes are outlined and highlight key design decisions and the consequences of these. The oxidation of SS 316 under ɣ-irradiation conditions was undertaken which showed γ-irradiation exposure during oxidation has a measurable effect on oxide type and thickness. The interactions between corrosion and radiolysis products were investigated building on previous studies in this field; iron oxides were γ-irradiated in the presence of hydrogen peroxide. The results of this study show complex behaviour that is a result of both reactions at the oxide | solution interface and those in bulk aqueous phase. The impact of this work and its place in the larger project at Rolls Royce is discussed, giving recommendations on what should be considered when modelling these systems.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Fabio Scenini (Supervisor), Francis Livens (Supervisor) & Neil Burton (Supervisor)