Procedures to define Pu isotopic ratios characterizing a contaminated area in Palomares (Spain)

Plutonium isotopic ratios have been calculated in soils contaminated by the Palomares accident which occurred in 1966 (Almería, Southeastem Spain). Contrasted techniques have been used to determine the radionuclide activities: 238 Pu and 238+240 Pu were analysed by α-spectrometry prior purification on anion-exchange resins, the ratio 239 Pu/ 240 Pu was estimated by α-spectra deconvolution and 241 Pu was directly measured by liquid scintillation counting and indirectly through quantification of in-grown 241 Am from aged plutonium discs. The mean activity ratios 238 Pu/ 239 Pu, 239 Pu/ 240 Pu, 241 Pu/ 239 Pu, backdated to 1966, were 0.027±0.002 (1σ), 4.5±0.2 (1σ) and 8.2±0.8 (1σ), respectively, characterizing the accident of Palomares as the source term of the measured plutonium.