Implementation of energy reduced 90Sr/90Y radiation fields, or: Propagation of beta radiation, a case study

Abstract

Reference beta-particle radiation fields are well described in the standard series ISO 6980 issued by the International Organization for Standardization (ISO). In its 2022/2023 edition, two new radiation fields are defined consisting of a radioactive 90Sr/90Y source and a 3 mm or 4 mm plastic absorber located 4 cm in front of the source — with the reference plane of the radiation field being located 20 cm from the source. In this work, the detailed method of how to implement and use these new radiation fields using a Beta Secondary Standard, BSS 2, is described. Furthermore, the influence of the position and thickness of the plastic absorber on the radiation field, i.e., on its spectral and angular distribution as well as on the dose rate, was investigated. It turned out that a change of position by one centimeter or a thickness change of a tenth of a millimeter result in significant changes of the dose rate (∼ 7 % to ∼ 10 %). Finally, the dependence of the angular and spectral distribution on the position and thickness of the absorber was investigated in detail.