Improvement in the evaluation of gamma radiation from cylindrical bodies with spatially inhomogeneous source activity distribution

Abstract Radioactivity and radioactive materials are constant companions of our life. Therefore, their studies and utilization are an important part of the development of human society. One of lines of work with radioactivity of various media concerns their gamma ray spectrometry which covers the issues of mineral exploration, ecological monitoring, medicine, security, agriculture, anti-terrorist protection, assessment of the consequences of man-made and natural disasters, etc. The tasks of spectroscopy include the description, survey, and analysis of gamma fields produced by natural environment or artificial objects. To solve these tasks effectively, mathematical modeling based on the fundamental physical laws of radioactivity and modern achievements of mathematics and informatics is used. In particular, in this research, we consider the gamma radiation from the cylindrical body and develop the procedure for assessing the gamma flux intensity when the source activity is inhomogeneously distributed over the body volume. The procedure is a semi-analytic approach and is based on the representation of the source activity function as a linear combination of step functions. Physically it means the approximation of inhomogeneous body by a layered medium. The procedure also allows one to get an analytical expression for the gamma flux intensity which is observed at the axes of symmetry of the cylindrical body. It is performed the comparison of approximate and exact values of intensity for exponential source activity function when analytical integration is possible. We also discuss the procedure application to the case when the source activity function is nonmonotonic and restrictions of procedure use appear.