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

In this paper we present new results for prompt fission gamma-ray spectral characteristics from the thermal neutron induced fission of Pu-240*. The measured spectra were unfolded by using the detectors' response functions, simulated with GEANT4. We obtained in average per fission a gamma-ray multiplicity (M) over bar (gamma) = (7.35 +/- 0.12), a mean photon energy (epsilon) over bar (gamma) = (0.85 +/- 0.02) MeV, and an average total energy released in fission (E) over bar (gamma,tot) = (6.27 +/- 0.11) MeV. Our results are in good agreement with historical data measured in the 1970s by Verbinski et al. and results from recent calculations 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 Pu-239(n(th), f) reaction may be ruled out as possible source of gamma heating underestimation, when compared with benchmark calculations based on existing nuclear data.