Improved Plutonium and Americium Photon Branching Ratios from Microcalorimeter Gamma Spectroscopy

TL;DR

This paper uses high-resolution microcalorimeter gamma spectroscopy to significantly improve the accuracy of photon branching ratios for plutonium and americium isotopes, aiding nuclear material analysis.

Contribution

It introduces a method employing microcalorimeter sensors to reduce uncertainties in key gamma-ray branching ratios for nuclear materials.

Findings

Uncertainty reduced by over a factor of three for one branching ratio.

Uncertainty reduced by a factor of 2-3 for four other ratios.

High-resolution spectra enable more accurate nuclear material assessments.

Abstract

Photon branching ratios are critical input data for activities such as nuclear materials protection and accounting because they allow material compositions to be extracted from measurements of gamma-ray intensities. Uncertainties in these branching ratios are often a limiting source of uncertainty in composition determination. Here, we use high statistics, high resolution (~60-70eV full-width-at-half-maximum at 100 keV) gamma-ray spectra acquired using microcalorimeter sensors to substantially reduce the uncertainties for 11 plutonium (238Pu,239Pu,241Pu) and 241Am branching ratios important for material control and accountability and nuclear forensics in the energy range of 125 keV to 208 keV. We show a reduction in uncertainty of over a factor of three for one branching ratio and a factor of 2{3 for four branching ratios.