Application of laboratory beta radiometry for quantitative indication of radionuclide concentration in plant samples

Abstract

The aim is to improve the beta-radiometric method of quantitative indication of the content of 90Sr and 137Cs in the counters of plant samples.
 Material and methods. In the Chernobyl exclusion zone (ChEZ) in 2017, 2019, leaves of silver birch, black poplar, common reed, sedge were selected, which were dried, crushed, and used as calculating samples for beta radiometry and spectrometry. For measurements, a combined KRK-1 radiometer and a SEB 01-150 spectrometer beta-radiation energy were used.
 Results. Currently, in plant samples from the ChEZ, the following are widespread: natural 40K, the concentration of which is usually less than 1 % in relation to the concentration of technogenic radionuclides 90Sr+90Y and 137Cs, therefore, when measuring 90Sr and 137Cs, beta radiation of 40K can be ignored. The measurements were carried out without a spectral filter and using a thin molybdenum filter. Without filter – show the count rate of 90Sr+90Y and 137Cs radiation. The filter transmits 2–3.5 % of the low-energy beta radiation of 90Sr and 137Cs and more than 95 % of the high-energy 90Y. The ratio of the count rate of 90Y pulses with and without filter is 2.14. The 90Sr concentration in the samples was determined from the results of measurements of 90Y, and 137Cs – through the fraction of the counting rate, which remains after deducting 90Sr+90Y. Comparison of the concentration of radionuclides measured by the method of beta-radiometry and spectrometry showed no significant difference between the results obtained by the two methods.
 Conclusions. The beta radiometry method for 90Sr and 137Cs provides for measuring the counting rate of beta radiation from counting samples without a spectral filter and using a thin molybdenum filter. Based on the research results, a procedure for calculating the concentration of 90Sr and 137Cs in counting samples of plant leaves was developed