Radiochemical analysis for investigation of processing
and disposal of radioactive wastes

Research purpose and contents

For decommissioning of the Fukushima Daiichi Nuclear Power Station (hereafter, FDNPS), safe and appropriate disposal of wastes generating from FDNPS accident is significantly important issue. Radioactive wastes are generated in regular operation of nuclear power plants. However, the characteristics of the wastes generated from the accident shows complex properties because contamination process is different. Also various materials are contaminated and become radioactive wastes, for example, rubble, vegetation, and soil (these were contaminated at the accident) and the secondary wastes from contaminated water treatment operating after the accident. To dispose of them, it is necessary to clarify the nuclides contained and their amount, and determine the disposal method based on that information.
The objective of this study is to obtain the data by analysis of the real sample taken in FDNPS site and to accumulate them for understanding their characteristics.

Preparation of analysis

To obtain the analytical data of the contaminated water and wastes sampled from FDNPS, the series of processes includes sampling, transport, preparation, and analysis. That is, first, the sample of rubble, vegetation, soil and the secondary wastes from FDNPS site, and they are transported to the analysis facilities which can treat the radioactive materials. Second, in case of solid wastes, samples are dissolved into acidic liquid as preparation of analysis. However, there are some restrictions such as usable chemicals in each facility. So the suitable preparation method is required. We should develop and establish the preparation method.

Hot laboratories

Sample analysis

Radionuclides and their concentration in the samples are obtained by measuring γ-, β-, and α-rays using a Ge-semiconductor detector, Geiger–Muller detector, scintillation counter, and an Si–semiconductor detector. For accurate measurement, chemical separation is needed. One of the separation procedure is selective extraction of target nuclides from other elements using suitable adsorbent.
The obtained data of various waste samples have been stored to utilize for understanding the characteristics of complex waste and investigation of treating and disposal method.

Publishing of data

The obtained analytical results are published at the Decommissioning/Contaminated Water Measures Team/Secretariat Meeting. After that, the data is reported as papers and provided on the Internet website "FRAnDLi (Fukushima Daiichi Radwaste Analytical Data Library)". FRAnDLi is a database for the analytical data of the FDNPS wastes operation by JAEA for proceeding decommissioning activities and promoting academic research related to FDNPS accident.

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