Analysis of gamma-emitting radionuclides in soils around high energy accelerators

Abstract

Objective

To investigate the specific activities of gamma radionuclides in the soils around high energy accelerators, and to analyze the influence of rays emitted by nuclides with characteristic peaks at similar energy points on nuclide measurement results, in order to provide reference for the accurate identification of radionuclides.

Methods

GR5021 high-purity germanium gamma spectroscopy system was used to measure the specific activities of gamma-emitting radionuclides ²²⁶Ra, ²³²Th, ²³⁸U, ⁴⁰K and artificial radionuclides ⁵⁴Mn, ⁵²Mn, ⁷Be, ²²Na, ⁵⁹Fe, ⁹⁵Zr in six soil samples around three kinds of high energy accelerators, and the theoretical counts of the characteristic peak of 835.7 ​keV were compared with the measured counts of the characteristic peak of ⁵⁴Mn.

Results

The specific activity ranges of gamma-emitting radionuclides ²²⁶Ra, ²³²Th, ²³⁸U and ⁴⁰K in the soils around three kinds of high energy accelerators were 55.5–171, 34.9–99.9, 21.9–79.3 and 247–680 Bq/kg, respectively. The specific activities of artificial radionuclides ⁵²Mn, ⁷Be, ²²Na, ⁵⁹Fe and ⁹⁵Zr were basically lower than the minimum detection limit. A characteristic peak was found at the energy point of 835.7 ​keV in six soil samples, and the corresponding total absorption peak counts were from ²²⁸Ac of ²³²Th ​decay daughter.

Conclusions

The specific activities of gamma-emitting radionuclides were at the normal natural background levels. The specific activities of artificial radionuclides were basically lower than the minimum detection limits. For ²³²Th, when its specific activity is above 40 Bq/kg, characteristic peak of its decay daughter ²²⁸Ac could be misjudged as characteristic peak of ⁵⁴Mn.