Determination of self-absorption correction in the activity measurement of ²¹⁰Pb

Self-absorption correction factors for ²¹⁰Pb and ¹³⁷Cs were experimentally determined through an intercomparison study. Three different matrix samples provided for the intercomparison test were analyzed. The linear attenuation coefficients for three matrices were measured using point sources of ²¹⁰Pb and ¹³⁷Cs without a collimator, with all measurements performed using an N-type coaxial HPGe-detector. To account for the oblique transmission of γ-rays within the samples, effective thickness values were calculated and incorporated into the correction of γ-rays within the calculations. Additionally, a Monte-Carlo simulation was performed using the PHITS code to evaluate the contribution of scattered photons to the full-energy peak. Consequently, the density-dependent quantitative contributions of scattered γ-rays to the full-energy peak areas were determined.