Observation of Gamma-emitting Nuclides with Intermediate Half Lives in Rain Water (October 1961 to December 1962)

Abstract

Rain water radioactivity in each rain fall was analyzed by gammaray spectrometric method for the gamma-emitting nuclides with intermediate half lives during the period from October 1961 through December 1962. The gamma-ray spectra observed were generally featured with three predominant photopeaks at around 0.14 MeV, 0.5 MeV and 0.75 MeV, which mostly attributed to (¹⁴¹Ce, ¹⁴⁴Ce), (¹⁰³Ru, ¹⁰⁶Ru-¹⁰⁶Rn) and (⁹⁵Zr+⁹⁵Nb) respectively in comparatively younger fallout. Analytical data were presented together with graphical explanations.
Decay rate of the 0.14 MeV peak observed in samples from March through July 1962 revealed that there was little influence of fallout due to the Pacific Test Series in the same period. A clear peak of ⁹⁵Zr+⁹⁵Nb in the cumulative deposition was shown in early summer with a maximum value of about 200 mμc/m², probably due to frequent rain falls in this period.
The data presented could be useful to estimate approximately the fallout deposition of gamma-emitters with intermediate half lives in other areas in this country with some assumptions.