Initially, this measurement technique and procedure have been developed to obtain experimental data for the demonstration of the neutronics calculation code. However, after the accident at the Fukushima Dai-ichi Nuclear Power Plant in 2011, it is recognized that the measurement of the isotopic composition of the used nuclear fuel is crucial to take countermeasures to the accident. We expect that measurement of the amounts of many varieties of isotopes is required for the decommissioning of the Fukushima Dai-ichi site.
To accumulate experience and recheck the measurement procedure, JAEA has already started the measurement campaign after the Fukushima accident. The first PIE sample was taken from the same fuel assembly used in the PIE campaign described in the earlier sections. In 2012, one fuel sample was taken from the ZN3 fuel assembly irradiated in Fukushima Dai-ni nuclear power plant unit 1 and the dissolution was conducted in 2013. It is expected that the measurement results will be obtained in F.Y. 2014.
JAEA will also assay the isotopic composition of spent nuclear fuel irradiated in PWR. It is planned to measure the isotopic compositions of nine samples taken from NO4F69 fuel assembly irradiated in Ohi Nuclear Power Station unit 4 of the Kansai Electric Power Co., Inc. (KEPCO). The nine PIE samples will be taken from three fuel rods including UO2 and UO2-Gd2O3 whose average burn-up values are estimated to be from 40 to 57 GWd/t approximately. This measurement campaign was started in 2013, and the first results are hoped to be seen in 2014.
The Japan Atomic Energy Agency had been active in the field of postirradiation examinations since the 1980s. Based on past experience and introducing the stateof-the-art technique, JAEA began a measurement program of fission products that are important for reactivity assessment. By this program, the quantitative analytical method based on isotopic dilution technology has been developed for fission products in spent fuels. JAEA will carry out the measurement program of isotopic composition of the used nuclear fuel for countermeasures to the accident at Fukushima Dai-ichi Nuclear Power Station. This program consists of the measurement of several samples not only from BWR but also PWR. The obtained results will be used for the evaluation of the burnup code system. Also, the experience of treating spent fuel and measuring its isotopic composition will strengthen the technical ability of JAEA for providing countermeasures for the Fukushima accident.
Acknowledgments The authors thank the following staff in charge of the measurement program in JAEA: K. Tonoike, M. Amaya, M. Umeda, T. Sonoda, K. Watanabe, N. Shinohara, M. Ito,T. Ueno, M. Magara, J. Inagawa, S. Miyata, S. Sampei, K. Kamohara, M. Sato, H. Usami,
K. Ohkubo, M. Totsuka, Y. Sakazume, and T. Kurosawa. The authors are deeply indebted to
T. Ichihara and T. Nakai of the Kansai Electric Power Co., Inc., and M. Kawasaki and I. Hyodo of Tokyo Electric Power Co., Inc., who allowed us to use their spent fuel assemblies and to use owned technical data. The authors also like express their appreciation to Y. Taniguchi, H. Nagano, T. Ito,
H. Kishita, Y. Kubo, and K. Kakiuchi of Nuclear Fuel Industries, Ltd., for their cooperation in using their spent fuel assemblies and technical data.