PNNL

Abstract

Samarium-153 (153Sm) is one of the many isotopes of interest to the nuclear forensics community. This short-lived radionuclide decays to stable europium-153 via beta emission, with subsequent de-excitation via gamma emission and internal conversion. Historical measurements of 153Sm by gamma spectrometry and beta liquid scintillation counting have shown a low bias compared to beta proportional counting. In order to investigate this, 1 four national laboratories jointly conducted an experimental inter-comparison exercise on a certified 153Sm sample, created from neutron activation of samarium-152. Radiometric measurements were conducted using gamma spectrometry, liquid scintillation, gas proportional counting, and passivated implanted planar silicon detectors and compared across the four institutions against the certificate. The results from this experiment are presented together with a number of conclusions which suggest that the current published cumulative fission yield for 153Sm, as used by many laboratories, is approximately 15% high and is the likely cause of the previously observed historical bias.