SPECTROMETRIC DETERMINATION OF RADIATION INDICATORS OF Cs-137 AND Sr-90 AS PART OF THE QUALITY ASSESSMENT OF SURFACE FRESH WATER IF USED OF THE ENVIRONMENTAL CRITERIA
Keywords:Keywords: surface fresh water; ecological status criteria; indicators of radiation action of water; determination of 137Cs and 90Sr radionuclides; beta and gamma spectrometry
The analytical relations of rating water by pollution categories are presented. The case of water contamination with radioactive nuclides 137Cs and 90Sr was considered. The relations establish the functional relationships between the measured values of radionuclide specific activity and permissible radionuclide levels in the inland surface fresh waters. The parameters of measurement procedures (MP) and control procedures (CP) and metrological characteristics of the spectrometer were used as variables. The influence of MP and CP parameters and spectrometer characteristics on assigning water to the corresponding category was investigated.
The expected values of the specific activity of 137Cs and 90Sr were calculated. The case of SEB 01–70 and SEB 01–150 spectrometers was considered. The sensitivity of spectrometers to 137Cs was determined within the range of 0.817–2.310 Bq per sample. The minimum water quantity that can be used to analyze the radionuclide content was determined for each pollution category. The impossibility of determining the specific activity of 137Cs in waters of Categories 1 and 2 by using only these spectrometer models was substantiated. The activity of 137Cs and 90Sr in waters of Categories 1 and 2 can be determined by the combined use of beta and gamma spectrometers. To determine the activity of 90Sr in surface water with low radionuclide activity, it was proposed using the controlled cation exchange mode in the preparation of load. In this case, the saturation state of the absorber ionite is controlled by determining the concentration of Ca cations in the water that has passed through the absorber.
The obtained results are the basis for determining the technological parameters of spectrometric measurement of 137Cs and 90Sr activity. The algorithm for assessing the measured values of radionuclide activity and comparing them with the permissible levels can be used for other spectrometers. In such a situation, the assessment and determination of technological parameters is carried out using the data of the metrological certification of spectrometers. Depending on the purpose of study, in cases of low activity levels of 137Cs and 90Sr, it is also advisable to optimize the methods and choice of measuring means.