Determination of the gamma emission probabilities of ²³⁹Np

Northwest Institute of Nuclear Technology, Xi’an, China

^a e-mail: shangjianbo@nint.ac.cn

Published online: 13 September 2017

Abstract

²³⁹Np is an important nuclide as the decay daughter of ²³⁹U and it decays to ²³⁹Pu by emitting beta particles and gamma rays with a half life of 2.356 days. The data of the emission probabilities of its gamma-rays in the open references are consistent except for the main gamma-ray of 106.1 keV, the emission probability of which varies from 25.9% to 27.2%. To verify the emission probability of 106.1 keV gamma-ray of ²³⁹Np, a N-type coaxial HPGe detector was calibrated using ²⁴¹Am, ¹³³Ba, ⁶⁰Co, ¹⁵²Eu and ¹⁵⁵Eu reference gamma sources to get the accurate efficiency of the 106.1 keV gamma-ray. ²³⁹Np was purified from solution containing ²⁴³Am, where ²³⁹Np is the alpha decay daughter of ²⁴³Am. The specific activity of 239Np solution was determined by a 4πβ (PC)-γ coincidence counting device. There were 6 gamma sources prepared to measure with the HPGe detector, and the activity of ²³⁹Np in each gamma source was calculated with the weights of the solution contained in it. The emission probability of 106.1 keV of ²³⁹Np is measured to be (25.4 ± 0.3)%, which is consistent with 25.34%, the value evaluated in 2014.