Hydrogen pickup in nuclear reactor components

Nuclear reactors operate in high temperature, high pressure water with reactor internals constructed from stainless steel (reactor pressure vessel), nickel alloys (heat exchangers/steam boilers) and, of particular interest, zirconium alloys (nuclear fuel cladding and other reactor core components). The high pressure water is both corrosive and contains dissolved hydrogen gas to suppress radiolysis. Unfortunately, a fraction of hydrogen may become absorbed in the metallic alloys where it has an adverse effect on alloy properties (i.e. causing embrittlement). In order to understand the process of hydrogen pick-up knowledge of the kinetics and the mechanism of hydrogen uptake is needed. Currently, hydrogen measurements can only be performed ex-situ after corrosion in an autoclave. The aim of this research is to develop a method for measuring hydrogen uptake continuously directly within the high temperature, high pressure environment.

A convenient electrochemical method that is able to measure hydrogen permeation and diffusion in metals is the “Devanathan Cell” however this operates at ambient conditions. The experimental challenge is extend the maximum temperature of operation of this cell from ~95°C to ~300°C. There are a number of approaches available that would achieve this including the use of molten salt electrolytes, ionic liquids and hydrogen fuel cells. Success in the work would enable measurements in systematically controlled environmental conditions that will resolve questions regarding the exact mechanism of hydrogen uptake under these conditions.

The project is funded by Electricité de France (EdF) under the Mechanistic Understanding of Zirconium Corrosion (MUZIC) consortium. There will be extensive opportunities to collaborate with other consortium members in UK, USA, France and Sweden, including at the EdF research facility in Les Renardières, which is south of Paris.