Methodology for evaluating radioactive levels of material to be released under newly introduced clearance system in Japan

The amendment of nuclear reactors regulation law was established and the clearance system was introduced in 2005 in Japan. It enables us to recycle or dispose some radioactive waste that is radioactively contaminated so slightly that it isn't necessarily to be treated as radioactive material. The clearance system in Japan is compatible with global standard. The set of clearance levels of radioactive nuclides for Japanese clearance system is identical to one described in IAEA's safety report, RS-G-1.7. In this context, the methodology that JAPC created will be able to meet global standard. This introduction was followed by the first clearance project in Japan, which is currently being conducted by The Japan Atomic Power Company (JAPC). JAPC is decommissioning one of its nuclear power plants, Tokai unit 1, and has already released some dismantled carbon steel objects generated through this decommissioning work into the environment under this new system. As one of main preparatory activities, JAPC created the methodology to judge whether its radioactivity is lower than specified criteria in the guideline for the clearance system. It includes identification of radioactive nuclides to be evaluated and the way to evaluate radioactive level of each identified nuclide in a carbon steel object to be released. This methodology was subject to safety review by Japanese regulatory agency and it was approved in September 2006. Since them JAPC have been doing radioactivity evaluation and clearance judgment in accordance with this approved methodology. Also JAPC installed tailor-made clearance measurement system that is well suited for this approved methodology. (author)