Plutonium contamination from accidental release or simply fallout: study of soils at Palomares (Spain)

The activity concentration of plutonium in an environmental sample does not usually constitute sufficient information to determine if it is due only t o fallout. Alpha and gamma spectrometry are used here conjointly in the stu dy of environmental soil samples to distinguish between samples showing plu tonium contamination due to fallout exclusively, and samples contaminated w ith plutonium from another source. The method was applied to soil samples c ollected in Palomares (Spain), where an accidental release of aerosols cont aminated with plutonium occurred. The two contributions (fallout and accide ntally released plutonium) were separated by means of the activity ratios b etween various radionuclides present in the samples analyzed. The fallout l evel was estimated from the Pu239+240/Cs-137 activity ratio. For samples sh owing contamination due to the accident, the Pu-238/Pu239+240 and Pu-239/Pu -240 activity ratios were also calculated to determine the grade of plutoni um of this contamination. (C) 2001 Elsevier Science Ltd. All rights reserve d.