A comparative study of different methods of preparation of sources for alpha spectrometry of plutonium

A comparative study of different methods of preparation of sources for alpha spectrometry of plutonium is presented. Typical values of the percentage tail contribution per unit alpha activity ratio 238 Pu /( 239 Pu + 240 Pu ) , fwhm and peak to valley ratios are given for (1) drop deposited sources from aqueous medium without using a spreading agent, (2) drop deposited sources from aqueous medium by using tetraethylene glycol (TEG) as a spreading agent, (3) drop deposited sources from organic medium using TTA extraction and (4) electrodeposited sources. Results obtained on the determination of 238 Pu /( 239 Pu + 240 Pu ) alpha activity ratios in isotopic reference material SRM-947 and in a synthetic mixture of plutonium isotopes using an AuSi surface barrier detector for recording alpha spectra and geometric progression (GP) method for the evaluation of alpha spectra are presented. It is seen that preparation of drop deposited sources from TTA involves minimum effort and the quality of alpha spectra from these sources is comparable to those from the electrodeposited sources. Further, it is recommended that the uncertainty on 238Pu in SRM-947 can be considered as 0.8% (3σ) compared to 2% quoted by the National Bureau of Standards.