会議発表論文 A New approach for determination of 90Sr using Thermal Ionization Mass Spectrometry with Daly ion counting system

Sarata Kumar, Sahoo  ,  Norbert, Kavasi  ,  Tatsuo, Aono  ,  Palacz, Zenon

pp.38 - 41 , 2017-03 , Ebenezer Printing House
ISBN:81 88513 78 4
内容記述
In case of Fukushima Daiichi Nuclear Power Plant accident in Japan released and dispersed a significant amount of radionuclides (~520 PBq) in the environment. Shortly after the accident, volatile nuclides e.g. 137Cs, 131I and 132Te were detected in the Northern Hemisphere and elevated dose rates were observed in most of Japan. Contamination of radiostrontium isotopes, as they have intermediate volatility, was was delayed. Measurement of radiostrontium is a time consuming process since it involves a complex sample preparation and analytical separation required to produce reliable dataMeasurement of 90Sr (t1/2 = 28.8 y) is carried out since it is one of the most common and hazardous fission product after a nuclear reactor accident. 90Sr has a long biological half-life (~18y) in human body. Due to its chemical similarity to calcium, accumulates in bones and irradiates bone marrow, causing high radio-toxicity. Therefore, to assess 90Sr is important in case of a nuclear disaster.The fission yield of stable 88Sr (˜3.5×10-2) isotope in thermal neutron fission is comparable with the radioactive 90Sr (˜5.8×10-2) isotope. Therefore, it is important to check if there is any variation of the stable strontium isotope ratio (88Sr/86Sr) in environmental samples after a nuclear accident.Thermal ionization mass spectrometry is the technique of choice because of its inherent high precision and accurate measurement of isotopic ratio. Typical abundance sensitivity for strontium isotope ratio measurement with conventional TIMS is about 10-7. By the use of special lense like WARP filter for TIMS, an upper limit of 1.0 x 10-10 was achieved. Recent developments in analytical techniques have resulted in use of TIMS as a substitute for β counting method of strontium. In our laboratory, a Phoenix X62 TIMS has been set up with nine Farday cup collectors as well as Daly ion counting system to measure minor isotopes e.g. 90Sr. The range of the tested 90Sr activity varied from 0.12 mBq to 660 mBq. Isotope ratios of 90Sr as well as stable Sr isotope ratios in a few contaminated soil samples with radiocaesium and some plants from Fukushima prefecture will be presented.

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