Technical discussion on tritiated water treatment for Fukushima Daiichi Nuclear Power Station

Yamanishi, Toshihiko*; Kakiuchi, Hideki*; Tauchi, Hiroshi*; Yamamoto, Tokuhiro ; Yamamoto, Ichiro*

One of the essential subjects for the contaminated water at Fukushima Daiichi Nuclear Power Station is to serve technical data for handling the water, over a long period. All the radio nuclides other than tritium in the water can be treated by multi-nuclide removal equipment (advanced liquid processing system). However, it is not easy task to remove tritium. For this reason, a series of technical discussions has been carried out at a task force (Tritium Water Task Force) to handle the tritiated water after the treatment by the advanced liquid processing system. As of March 2016, 820,000 m of the contaminated water has been stored within tanks, and 620,000 m water has been treated by the multi-nuclide removal equipment. The concentration of tritium in the water is about 0.3 - 3.3 million Bq/litter. Various options for the treatment of the tritiated water; such as off shore release, geosphere injection, underground burial, and vapor or hydrogen release; have been discussed. The discussions have been carried out from viewpoint of technical and regulatory feasibility. Some pre-treatment methods, such as dilution and isotope separation, have also been discussed. A series of discussions on the isotope separation has been carried out with actual experimental tests. Some valuable results have been produced through the tests. This report presents a summary of the above-mentioned technical discussions on the tritiated water at Fukushima Daiichi Nuclear Power Station. Some recent conditions of the tritiated water will also be introduced.