Prompt Fission γ–ray Spectra Characteristics - A First Summary

Oberstedt, S.; Billnert, R.; Gatera, Angélique; Geerts, W.; Halipre, P.; Hambsch, F. J.; Lebois, M.; Marini, P.; Vidali, M.; Wilson, J. N.

doi:10.1016/j.phpro.2015.04.011

Cited by 11 publications

(10 citation statements)

References 20 publications

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“…6, even for 252 Cf(sf), recent measurements [42, 43] disagree significantly with past results [41]. Note that the "experimental' data by Oberstedt [44] reported here corresponds to the result of a fit using a negative binomial distribution, and cannot be considered raw experimental data. The comparison of experimental data with model calculations of P (N γ ) is complicated by the use of a specific γ-ray detector energy threshold below which no γ rays are measured, as well as by the time coincidence window between the emitted γ rays and the fission trigger and have to be considered when comparing to model calculations.…”

Section: (B)contrasting

confidence: 63%

Correlated prompt fission data in transport simulations

et al. 2018

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Detailed information on the fission process can be inferred from the observation, modeling and theoretical understanding of prompt fission neutron and γ-ray observables. Beyond simple average quantities, the study of distributions and correlations in prompt data, e.g., multiplicity-dependent neutron and γ-ray spectra, angular distributions of the emitted particles, n-n, n-γ, and γ-γ correlations, can place stringent constraints on fission models and parameters that would otherwise be free to be tuned separately to represent individual fission observables. The FREYA and CGMF codes have been developed to follow the sequential emissions of prompt neutrons and γ rays from the initial excited fission fragments produced right after scission. Both codes implement Monte Carlo techniques to sample initial fission fragment configurations in mass, charge and kinetic energy and sample probabilities of neutron and γ emission at each stage of the decay. This approach naturally leads to using simple but powerful statistical techniques to infer distributions and correlations among many observables and model parameters. The comparison of model calculations with experimental data provides a rich arena for testing various nuclear physics models such as those related to the nuclear structure and level densities of neutron-rich nuclei, the γ-ray strength functions of dipole and quadrupole transitions, the mechanism for dividing the excitation energy between the two nascent fragments near scission, and the mechanisms behind the production of angular momentum in the fragments, etc. Beyond the obvious interest from a fundamental physics point of view, such studies are also important for addressing data needs in various nuclear applications. The inclusion of the FREYA and CGMF codes into the MCNP6.2 and MCNPX-PoliMi transport codes, for instance, provides a new and powerful tool to simulate correlated fission events in neutron transport calculations important in nonproliferation, safeguards, nuclear energy, and defense programs. This review provides an overview of the topic, starting from theoretical considerations of the fission process, with a focus on correlated signatures. It then explores the status of experimental correlated fission data and current efforts to address some of the known shortcomings. Numerical simulations employing the FREYA and CGMF codes are compared to experimental data for a wide range of correlated fission quantities. The inclusion of those codes into the MCNP6.2 and MCNPX-PoliMi transport codes is described and discussed in the context of relevant applications. The accuracy of the model predictions and their sensitivity to model assumptions and input parameters are discussed. Finally, a series of important experimental and theoretical questions that remain unanswered are presented, suggesting a renewed effort to address these shortcomings.

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Section: (B)contrasting

confidence: 63%

Correlated prompt fission data in transport simulations

et al. 2018

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“…The low-energy structure observed in the PFGS from 252 Cf(sf) is also visible in the spectra from thermal-neutron induced fission on 235 U and 241 Pu with the individual peaks showing different intensities [24]. This may be due to the different shape of the corresponding mass distributions.…”

Section: Methodsmentioning

confidence: 84%

“…Figure 14. Prompt fission γ-ray spectrum from the spontaneous fission from 252Cf [24] compared to the historical data of Verbinski et al [25] and recent FIFRELIN model calculations [27]. The dotted line represents the evaluated data ENDF/B-VII.1.…”

Section: Methodsmentioning

confidence: 99%

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

Hambsch

Salvador-Castiñeira

Oberstedt

et al. 2016

EPJ Web of Conferences

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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.

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“…The results have been published and only a slight increase in average PFG energy of 5.2% and 3.6% for 235 U(n th , f) and 241 Pu(n th , f), respectively [8] was found.…”

Section: Recent Achievementsmentioning

confidence: 96%

New prompt fission gamma-ray spectral data from ²³⁹Pu(n_th, f) in response to a high priority request from OECD Nuclear Energy Agency

et al. 2017

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Abstract. Benchmark reactor calculations have revealed an underestimation of γ -heat following fission of up to 28%. To improve the modelling of new nuclear reactors, the OECD/NEA initiated a nuclear data High Priority Request List (HPRL) entry for the major isotopes ( 235 U, 239 Pu). In response to that HPRL entry, we executed a dedicated measurement program on prompt fission γ -rays employing state-of-the-art lanthanum bromide (LaBr 3 ) detectors with superior timing and good energy resolution. Our new results from 252 Cf(sf), 235 U(n th ,f) and 241 Pu(n th ,f) provide prompt fission γ -ray spectra characteristics : average number of photons per fission, average total energy per fission and mean photon energy; all within 2% of uncertainty. We present preliminary results on 239 Pu(n th ,f), recently measured at the Budapest Neutron Centre and supported by the CHANDA Trans-national Access Activity, as well as discussing our different published results in comparison to the historical data and what it says about the discrepancy observed in the benchmark calculations.

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Prompt Fission γ–ray Spectra Characteristics - A First Summary

Cited by 11 publications

References 20 publications

Correlated prompt fission data in transport simulations

Correlated prompt fission data in transport simulations

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

New prompt fission gamma-ray spectral data from ²³⁹Pu(n_th, f) in response to a high priority request from OECD Nuclear Energy Agency

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Prompt Fission γ–ray Spectra Characteristics - A First Summary

Cited by 11 publications

References 20 publications

Correlated prompt fission data in transport simulations

Correlated prompt fission data in transport simulations

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

New prompt fission gamma-ray spectral data from 239Pu(nth, f) in response to a high priority request from OECD Nuclear Energy Agency

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Product

Resources

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New prompt fission gamma-ray spectral data from ²³⁹Pu(n_th, f) in response to a high priority request from OECD Nuclear Energy Agency