Assessment of the activity of remote gamma radiation sources

A computer-oriented method for rapid assessment of the activity of remote gamma radiation sources in situ (in the field without sampling) is proposed. For calibration of portable and on-board detection units, reference gamma radiation sources are sequentially located at two points: one close to the crystal body, and the second, with an activity of at least 50 kBq, at a distance of 2 m or more along the axis of the detector. The net areas of the total absorption photopics, the live time of the spectrum set, the distances to the sources and their activity are used to determine special calibration coefficients. The calibration coefficients, together with the zero-distance efficiency curve, are used to assess the activity of remote gamma radiation sources (if the distance to the source exceeds its size by an order of magnitude or more). When calculating, the approximate distance to the detector is indicated, the material and wall thickness of the container can be taken into account. An independent expert examination found that the uncertainty of the proposed measurement method does not exceed 30% (p=0,95), which is quite acceptable for in-situ studies.