研究目的
The aim of the work is the evaluation of uncertainty in measurement of radionuclides MDA on the gamma radiation 137Cs, depending on the PS volume and irradiation geometry.
研究成果
The expanded MDA measurement uncertainties, registered by different volume PS were estimated. Gamma – radiation source 137Cs was used. Found that radionuclide 137Cs MDA, registered by researched PS, ranges from 3-4 kBq (h = 10 cm) up to 23-25 kBq (h = 50 cm). Extended uncertainty interval is ± 21-23 % for all measurement options considered. Found that the determining factor influencing on the uncertainty by type B in MDA measuring and the expanded MDA measurement uncertainty is the uncertainty by type B in sensitivity factor PS. It has been shown that with increasing distance from PS to IRS from 10 cm to 50 cm, 5 times the background count rate contribution to PS count rate increases. This effect leads to increase in sensitivity factor uncertainty and MDA uncertainty in 10 times. Increase in PS volume gives almost no gain in the MDA uncertainty measuring. It is because the sensitivity coefficient increases (of high count rate) together with background.
研究不足
The study is limited to the evaluation of uncertainty in measurement of radionuclides MDA on the gamma radiation 137Cs using large plastic scintillators. The influence of scintillators volume and irradiation geometry on the MDA evaluation was studied, but other factors may also affect the results.
