Prompt-fission γ -ray spectral characteristics from Pu239(nth,f)

Abstract

In this paper we present new results for prompt fission γ-ray spectral characteristics from the thermal neutron induced fission of 240 Pu *. The measured spectra were unfolded by using the detectors' response functions, simulated with GEANT4. We obtained in average per fission a γ-ray multiplicityM γ = (7.35 ± 0.12), a mean photon energy¯ γ = (0.85 ± 0.02) MeV, and an average total energy released in fissionĒ γ,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 239 Pu(n th ,f) reaction may be ruled out as possible source of γ heating underestimation, when compared with benchmark calculations based on existing nuclear data.

Prompt fissionγ-ray characteristics from neutron-induced fission on 239Pu and the time-dependence of prompt-γray emission

“…4 the simulated detector response of our 51 mm × 51 mm LaBr 3 :Ce detectors is shown (black line) together with the integral raw spectrum (green line), the normalized background spectrum (blue dashed line) and the background-corrected total prompt fission γ-ray spectrum. The transition from the 1 st excited to the ground state in 27 Al is visible at E γ = 843 keV. In the lower part of Fig.…”

“…All numerical details may be found in Table 1 of Ref. [27]. Prompt fission γ-ray spectra from thermalneutron induced fission on 239 Pu (red line with error bars) compared with data from Verbinski et al [23] and Chyzh et al [24].…”

“…It requires the determination of the detector response to fast neutrons. In our case this will manifest in the detection of γ-rays following the inelastic scattering of prompt fission neutrons essentially on 79,81 Br and 139 Ce from the scintillation material, and on 27 Al from the detector encapsulation. In a first approach the Geant4 simulation was performed time-integrated.…”

Prompt fission gamma-ray emission spectral data for 239Pu(n,f) using fast directional neutrons from the LICORNE neutron source

“…The measured PFGS is extracted with the time window set to be [−3 ns, +3 ns]. This time window was chosen due to the convenience in comparison with another experiment [1], which measured the PFGS characteristics with thermal neutrons.…”

“…Recent results on PFG emission in thermal neutron induced fission of 239 Pu have been published in Ref [1]. Recent reactor experiments indicate heating effects from gamma-rays are underestimated up to 28% [2] when compared with the simulations based on the currently available experimental data.…”