水中⁹⁰Sr放射能濃度の⁹⁰Yβ線測定による迅速簡便測定法

抄録

 A rapid and simple method to measure the concentration of ⁹⁰Sr in water by measuring β-rays from ⁹⁰Y was presented. Under the situation that ⁹⁰Sr/⁹⁰Y, ¹³⁴Cs and ¹³⁷Cs are the main radionuclides included in the water sample, only β-rays from ⁹⁰Y can transmit through 1.5-mm-thick polyethylene. From this fact, it is possible to measure β-rays from ⁹⁰Y using a β-ray detector, such as the GM-counter, set beneath the 1.5-mm-thick bottom of the water bottle containing the sample with ⁹⁰Sr/⁹⁰Y. The acrylic resin collimator having 0 cm, 1.00 cm, 1.50 cm or 3.00 cm diameter was made to detect β-rays at the fixed region of the GM-counter used. Contributions from bremsstrahlung produced by β-rays and γ-rays from radionuclides such as ¹³⁴Cs and ¹³⁷Cs/^137mBa are removed by subtracting the count rate measured with a 1.00 cm acrylic resin collimator without a hole as the background count rate. The developed method was studied using the bottle routinely used at the Fukushima Daiichi Nuclear Power Station. It was confirmed that the developed method can be applied to measure the ⁹⁰Sr concentration in water to the order of several Bq/cm³ if ¹³⁴Cs and ¹³⁷Cs concentrations are less than or equal to the ⁹⁰Sr/⁹⁰Y concentration.