Sr-specific resin과 액체섬광분광법을 이용한 제주도내 환경시료중의 90Sr 분석

Abstract

A large amount of airborne radioactive species had been released following the Fukushima Daiichi nuclear reactor accident. They included such radionuclides as 134Cs, 137Cs, 131I and 90Sr. Among them, 134Cs, 137Cs and 131I were identified as having reached to Korea including Jeju Island around the end of March, 2011. It was not known, however, whether 90Sr had also reached to Korea or not, since 90Sr and its daughter 90Y are pure beta emitters and thus cannot be easily distinguished from other natural beta emitters. Conventional measurement of 90Sr in environmental samples involves a lengthy chemical process. We present an efficient method of measuring the 90Sr activity in environmental samples, which is based on using ion exchange columns loaded with a Sr-Spec resin (4',4''(5'')-di-t-butylcyclohexane-18-crown-6 from Eichrom Industries, Inc.) and beta ray spectroscopy. This process is much faster than the conventional method which is based on dissolving the sample with the fuming nitric acid and measuring the total beta activity after a series of tedious chemical processes of isolating Sr. In our procedure, Sr is directly separated from other hindrance elements with the Sr-Spec resin after a few chemically conditioning processes. After the column separation, the solution containing 90Sr is mixed with the scintillation cocktail Ultima Gold, and beta ray spectroscopy is conducted by liquid scintillation counting to measure the activity. Using this method, we measured the activity concentrations of strontium-90 in moss samples and in soil samples gathered from Jeju Island. The activity concentration of moss samples measured was in the range of 62.06±0.63 - 325.5±2.43 Bq/kg and the activity concentration of soil samples was in the range of 48.13±0.61 - 272.1±1.97 Bq/kg.