Abstract
Underexposed badge film contains a minor quantity of silver which corresponds to the low radiation dose even after completion of the photographic densitometry ; however, it cannot be detected with a photographic densitometer. We intended to clarify the minor silver content based on radioactivation analysis with thermal neutrons at KUR (Kyoto University Research Reactor). The natural silver consists of two stable nuclides, i.e., ^107Ag and ^109Ag. These can be activated with irradiation of thermal neutrons to two radionuclides,i.e., ^108Ag and ^110Ag. In this paper, through the activation analysis of an underexposed badge film, methods of measurements are shown regarding both ^108Ag produced by the ^107Ag by the ^109Ag (n,γ). After underexposed badge films were irradiated with thermal neutrons, some gamma-rays emitted from the radionuclides in the activated films were measured with a high pure Ge detector or a NaI (T1) scintillation detector. The following results were obtained : (1) several elements such as silver, iodine, gold, antimony, manganese and copper were detected by activation analyses of films exposed to low level ^60Co gamma-rays, (2) the exposure vs ^108Ag or ^110Ag activity curve was linear in the lower dose range of ^60Co gamma-rays. These data indicate that low level radiation doses, which is indeterminable by ordinary photographic densitometry, can be estimated by activation analysis of silver atoms in badge films.
