Prompt-fission γ-ray spectral characteristics from Pu-239(nth,f)

In this paper we present new results for prompt fission γ-ray spectral characteristics from the thermal neutron induced fission of 239Pu. The measured spectra were unfolded using the detectors’ response functions simulated with Geant4. We obtained in average per fission a γ-ray multiplicity M ̄γ = (7.13 ± 0.12), a mean photon energy ε ̄γ = (0.85 ± 0.02) MeV, and an average total energy released in fission Eγ,tot = (6.10 ± 0.11) MeV. Our results are in good agreement with historical data measured in the 1970’s by Verbinski et al. and results from calcualtions in the framework of Monte-Carlo Hauser Feshbach models. Our measured average total energy is slightly smaller than the one deduced previously and present in evaluated data. From this we conclude that the 239Pu(nth, f) reaction may be ruled out as possible source of γ heating under-estimation, when compared to benchmark calculations based on existing nuclear data.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard