Fission studies by prompt gamma-ray spectrometry

Materna, T.; Letourneau, A.; Amouroux, C.; Marchix, A.; Litaize, O.; Sérot, O.; Regnier, David; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Söldner, T.; Simpson, G. S.; Leoni, S.; Urban, W.

doi:10.1051/epjconf/20159302020

Cited by 2 publications

(2 citation statements)

References 10 publications

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“…The incident neutron energy dependence of fission product yields was also measured at TUNL [144] for several important actinides using monoenergetic neutrons through (d, p) and (d, t) reactions. Other efforts such as the VERDI [145] and EXILL [146] experiments are also trying to provide new information on fission fragment yields and their dependence on excitation energy.…”

Section: Experimental Needs and Statusmentioning

confidence: 99%

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: Experimental Needs and Statusmentioning

confidence: 99%

Correlated prompt fission data in transport simulations

et al. 2018

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“…For instance the γ -ray intensities in 92 Kr and 142 Ba in thermal neutron induced fission of 235 U are fully consistent between measurements and calculations if the latest (2015) release of RIPL-3 is used at low excitation energy in FIFRELIN code. The evolution of γ -ray intensities in 92 Kr versus the complementary partner (Ba) is also compared with calculations but requires a deeper analysis [17,18].…”

Section: Discussionmentioning

confidence: 99%

Prompt particle emission in correlation with fission fragments

Litaize¹,

Sérot²,

Thulliez³

et al. 2017

EPJ Web Conf.

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Abstract. The de-excitation process of primary fission fragments can be simulated with the FIFRELIN Monte Carlo code leading to an estimation of prompt fission observables such as neutron/gamma multiplicities and spectra in correlation with fission fragments. De-excitation cascades are simulated using the notion of nuclear realization following Becvar terminology generalized to neutron/gamma coupled emission. A nuclear realization is a random set of nuclear levels (energy, spin, parity) in association with partial widths for neutron, gamma or electron emission. Experimental data related to electromagnetic transitions in the discrete level region are taken from RIPL-3 database. When nuclear level structure is completely unknown (in the continuum region), level density and strength function models are used. In between these regions, our partial knowledge of nuclear structure is completed by models up to a fixed maximum level density. In this way the whole available experimental information is accounted for. FIFRELIN is ruled by five free input parameters driving the excitation energy sharing, the rotational energy and the spin distribution of primary fission fragments. These five free parameters are determined to match a target observable such as the average total prompt neutron multiplicity (ν). Once this procedure is completed, the whole set of fission observables can be compared with experimental results. Obviously the number of observables obtained within this code is higher than what is available from measurements. This code can therefore provide useful insights into the compatibility between models and a whole set of fission observables. In the present work the influence of shell corrections is reported on level densities and prompt fission neutron spectra (PFNS). The impact of the input data such as primary fission fragment total kinetic energy (TKE) is also addressed. Average prompt neutron multiplicity as a function of TKE is also estimated for each mass split and compared to recent measurements. The presence of structures in the calculations (especially for light nuclei) is clearly related to the nuclear level scheme. Various situations occur and an overestimation (or underestimation) of the calculated number of emitted neutrons can be correlated to the light or heavy fragment of a pair and to a restricted energy range. In addition prompt fission gamma spectra (PFGS) are estimated for selected fragment mass ranges and compared to recent measurements. In this way the presence of specific gamma-ray transitions can be established.

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Fission studies by prompt gamma-ray spectrometry

Cited by 2 publications

References 10 publications

Correlated prompt fission data in transport simulations

Correlated prompt fission data in transport simulations

Prompt particle emission in correlation with fission fragments

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