Gamma-neutron competition in the de-excitation mechanism of the fission fragments of 252Cf

et al. 2016

EPJ Web of Conferences

Abstract. In recent years JRC-IRMM has been investigating fission cross-sections of 240,242 Pu in the fast-neutron energy range relevant for innovative reactor systems and requested in the High Priority Request List (HPRL) of the OECD/Nuclear Energy Agency (NEA). In addition to that, prompt neutron multiplicities are being investigated for the major isotopes 235 U, 239 Pu in the neutron-resonance region using a newly developed scintillation detector array (SCINTIA) and an innovative modification of the Frisch-grid ionisation chamber for fission-fragment detection. These data are highly relevant for improved neutron data evaluation and requested by the OECD/Working Party on Evaluation Cooperation (WPEC). Thirdly, also prompt fission γ-ray emission is investigated using highly efficient lanthanide-halide detectors with superior timing resolution. Again, those data are requested in the HPRL for major actinides to solve open questions on an under-prediction of decay heat in nuclear reactors. The information on prompt fission neutron and γ-ray emission is crucial for benchmarking nuclear models to study the de-excitation process of neutron-rich fission fragments. Information on γ-ray emission probabilities is also useful in decommissioning exercises on damaged nuclear power plants like Fukushima Daiichi to which JRC-IRMM is contributing. The results on the 240,242 Pu fission cross section, 235 U prompt neutron multiplicity in the resonance region and correlations with fission fragments and prompt γ-ray emission for several isotopes will be presented and put into perspective.

Section: Resultsmentioning

confidence: 95%

Fission cross-sections, prompt fission neutron and γ-ray emission in request for nuclear applications

Hambsch

Salvador-Castiñeira

et al. 2016

EPJ Web of Conferences

“…Due to the correlation between TKE and fragment mass distributions this quantity must not be interpreted as the energy needed for a pair of fragments to emit one more neutron, as noted already in Ref. [18]. The discrepant data from Refs.…”

Section: Prompt Fission Neutrons From 252 Cf(sf)mentioning

confidence: 96%

Investigating Prompt Fission Neutron Emission from²³⁵U(n,f) in the Resolved Resonance Region

Göök

Hambsch

2016

EPJ Web of Conferences

Abstract. Investigations of prompt emission in fission is of importance in understanding the fission process in general and the sharing of excitation energy among the fission fragments in particular. Experimental activities at IRMM on prompt neutron emission from fission in response to OECD/NEA nuclear data requests is presented in this contribution. Main focus lies on currently on-going investigations of prompt neutron emission from the reaction 235 U(n,f) in the region of the resolved resonances. For this reaction strong fluctuations of fission fragment mass distributions and mean total kinetic energy have been observed [Nucl. Phys. A 491, 56 (1989)] as a function of incident neutron energy in the resonance region. In addition fluctuations of prompt neutron multiplicities were also observed [Phys. Rev. C 13, 195 (1976)]. The goal of the present study is to verify the current knowledge of prompt neutron multiplicity fluctuations and to study correlations with fission fragment properties.

“…[9], the average total γ -ray energy released in fission E γ,tot is depending linearly on the prompt fission neutron multiplicity ν n , which is based on the study published in Ref. [11]. There linear dependences were observed between incident neutron energy E n and both prompt fission neutron multiplicity ν n and the average total γ -ray energy E γ,tot .…”

Section: Systematics Of Pfgs Characteristicsmentioning

confidence: 96%

“…There linear dependences were observed between incident neutron energy E n and both prompt fission neutron multiplicity ν n and the average total γ -ray energy E γ,tot . From this it is obvious that E γ,tot has to be proportional to ν n , which "is explained in terms of the linear increase of the average spin of the fragments with their excitation energy" [11]. The latter cited work was then extended from the spontaneous fission of 252 Cf to other fissioning systems by including a dependence from both their mass and atomic numbers, A and Z, respectively [9].…”

Section: Systematics Of Pfgs Characteristicsmentioning

confidence: 99%

Prompt particle emission in fission – news on systematics and predictions for fission induced by fast neutrons

2017

EPJ Web Conf.

Abstract.As a consequence of recent experimental results, previously established systematics for prompt fission γ -ray spectra (PFGS) characteristics as function of both atomic and mass number of the compound system have been revised. Although based on purely empirical dependences, it allows estimating average gamma-ray multiplicity, mean and total photon energy in cases, where the target nuclei are either not available or not accessible experimentally. Based on this systematics, we show in this paper that PFGS characteristics may also be predicted for fission induced by fast neutrons. Our calculations were performed for the target nuclei 238 U, 235 U and 239 Pu in the neutron energy range from 0 to 20 MeV, and the results are compared to existing experimental and theoretical values.