Solid-Polymer-Electrolyte Tritiated Water Electrolyzer for Water Detritiation System

A solid-polymer-electrolyte (SPE) water electrolyzer for high-level tritiated water was designed for the Water Detritiation System (WDS). Polymeric materials were selected from a main viewpoint of radiation durability to keep their functions beyond ITER-WDS requirement (530kGy). Our selection was Pt + Ir applied Nafion^® N117 ion exchange membrane, VITON^® O-ring seal and polyimide insulator. A -ray irradiation test of the SPE cell demonstrated the durability of the cell against 530kGy. The electrolyzer is designed to handle around 9TBq/kg of high-level tritiated water. The detritiation of the polymeric materials is thus a critical problem for the maintenance or for the disposal of the electrolyzer. As for the Nafion membrane, most of tritiated water in the membrane was rapidly removed by such as vacuum dehydration. It was difficult, by contrast, to remove bound tritiated water in the membrane. An effective method to remove tritiated water in the bound water is to promote an isotope exchange.