Determination of the gamma emission probabilities of ²³⁹Np

Abstract

Abstract. 239 Np is an important nuclide as the decay daughter of 239 U and it decays to 239 Pu 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 239 Np, a N-type coaxial HPGe detector was calibrated using 241 Am, 133 Ba, 60 Co, 152 Eu and 155 Eu reference gamma sources to get the accurate efficiency of the 106.1 keV gamma-ray. 239 Np was purified from solution containing 243 Am, where 239 Np is the alpha decay daughter of 243 Am. 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 239 Np in each gamma source was calculated with the weights of the solution contained in it. The emission probability of 106.1 keV of 239 Np is measured to be (25.4 ± 0.3)%, which is consistent with 25.34%, the value evaluated in 2014.