A methodology for estimation of ²⁴¹Pu in biological samples by low energy HPGe detector

The activity of ²⁴¹Pu in the biological samples (tissue, blood etc) is an important input for the assessment of internal dose received by the workers. The radiochemical separation of Pu isotopes and ²⁴¹Am in a sample followed by á/â counting is a widely used method for their determination. However, this method is time consuming and needs longer time in sample preparation and radiochemical analysis. In this work, we have standardized a methodology for the determination of ²⁴¹Pu in the biological sample by measuring its ã/x-rays with low energy HPGe detector. Decay scheme of ²⁴¹Pu is shown. ²³⁷U achieves secular equilibrium with its parent ²⁴¹Pu in 47 days, therefore ã-ray photons emitted by ²³⁷U are used for the estimation of ²⁴¹Pu activity. But both the daughters of ²⁴¹Pu viz ²³⁷U and ²⁴¹Am decay to same isotope ²³⁷Np and populate the same excited states of ²³⁷Np, hence most of the ã-ray energies of ²³⁷U and ²⁴¹Am are same. For the estimation of ²⁴¹Am and ²⁴¹Pu activity present in the sample 59.5 keV and 208 keV photons emitted by these radionuclides have been used in this study