Evaluation of Delayed-Neutron Emission Probabilities

Mann, F.M.; Schreiber, M.; Schenter, R.E.; England, T.R.

doi:10.13182/nse84-a18508

Cited by 57 publications

(6 citation statements)

References 29 publications

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“…the ENDF/B versions) for nuclear applications up to present. The above free parameters a and b were from time to time redetermined (Mann et al, 1984;Mann, 1986;England et al, 1986) as more experimental data became available. These values are summarized in Table 2.…”

Section: Modelsmentioning

confidence: 99%

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Status of delayed-neutron precursor data: half-lives and neutron emission probabilities

Pfeiffer

Kratz

Möller

2002

Progress in Nuclear Energy

127

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We present in this paper a compilation of the present status of experimental delayed-neutron precursor data; i.e. β-decay half-lives (T 1/2 ) and neutron emission probabilities (P n ) in the fission-product region (27 ≤ Z ≤ 57). These data are compared to two model predictions of substantially different sophistication: (i) an update of the empirical Kratz-Herrmann formula (KHF), and (ii) a unified macroscopicmicroscopic model within the quasi-particle random-phase approximation (QRPA). Both models are also used to calculate so far unknown T 1/2 and P n values up to Z = 63. A number of possible refinements in the microscopic calculations are suggested to further improve the nuclear-physics foundation of these data for reactor and astrophysical applications.

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Section: Modelsmentioning

confidence: 99%

“…2.1 ±0.2 Kratz and Herrmann (1973) 51. 3.6 ±0.3 Mann (1984) 123.4 4.34 Mann (1986) 54.0 +31/-20 3.44 ±0.51 England (1986) 44.08 4.119…”

Section: Referencementioning

confidence: 99%

Status of delayed-neutron precursor data: half-lives and neutron emission probabilities

Pfeiffer

Kratz

Möller

2002

Progress in Nuclear Energy

127

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“…Earlier studies (see for example Refs. [14,15]) also presented an analysis of data in terms of the KHF, however, in the present work we will limit our comparisons to the results obtained by Pfeiffer et al, as they contained the most current and complete set of data in the fission fragment region known at the time. The work of Pfeiffer et al, now dates back more than 10 years and since then there have obviously been additional measurements of P n values to augment the available systematics.…”

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confidence: 99%

Improving systematic predictions ofβ-delayed neutron emission probabilities

et al. 2012

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“…23 The evaluation uses the methodology we described in Ref. 12; the updating is described in Ref. 24 (to be published).…”

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confidence: 99%

Background radiation from fission pulses

England¹,

Arthur²,

Brady³

et al. 1988

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Extensive source terms for beta, gamma, and neutrons following fission pulses are presented in various tabular and graphical forms. Neutron results from a wide range of fissioning nuclides (42) are examined and detailed information is provided for four fuels: 235 U, 238u, 232Th (an(j 239p u; t h e se bracket the range of the delayed spectra. Results at several cooling (decay) times are presented. For p-and y spectra, only 235 U and 239 Pu results are given; fissionproduct data are currently inadequate for other fuels. The data base consists of all known measured data for individual fission products extensively supplemented with nuclear model results. The process is evolutionary, and therefore, the current base is summarized in sufficient detail for users to judge its quality. Comparisons with recent delayed neutron experiments and total p~ and y decay energies are included. I. A. Yields The fission-product yields in use are a preliminary, unpublished version for ENDF/B-VI, 2 described in Ref. 3; mass chain yields are listed in Ref. 3 as well. All yield data are being updated and reevaluated prior to issue in Version VI of ENDF/B; the data in use are the most recent available and are current to about mid-1983. For this study, we did alter the 238 U fast-fission yields primarily in their distribution along the mass chains. The method of evaluation and the distribution models are described in Ref. 3. (Only the 238JJ proton pairing parameter was changed from values listed in that reference. The change was based on recent unpublished measurements made at Grenoble, France, and it resulted in a significant alteration in the calculation of delayed neutrons; however, it is less important to other aggregate quantities.) Most high-energy neutron yields are based on nuclear models and systematics, not on measurements. B. Halflives and Decay Branching Except for neutron branching (denoted as Pn), these data are taken from ENDF/B-V 2 and are listed in the summary document of Ref. 4. As noted in a later section, we now have sufficient tests to believe in their validity and the yield data can be assessed as generally very good. C. Beta/Gamma Spectra and Their Decay Energies Earlier testing of these ENDF/B-V data 2 demonstrated that measured nuclide spectra were usually deficient for many high-Q transitions. 5 ' 6 An earlier version of ENDF/B that relied more on nuclear model generated spectra showed better agreement with benchmark experiments than Version V. Other countries have also discovered the deficiency and the only reasonable recourse in the near future for individual nuclides is an augmentation of spectra using nuclear models. 7 As discussed later, this has already been accomplished for total P~ and y decay energies, but not spectra, by the Japanese,8.9 with excellent results. As related to this report, the total ]3~ and y energies recommended by the Japanese are used in place of those in ENDF/B-V. Here, however, our primary interest is in aggregate spectra. For this purpose, we use 18-and 19-group functions fitted to ou...

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Evaluation of Delayed-Neutron Emission Probabilities

Cited by 57 publications

References 29 publications

Status of delayed-neutron precursor data: half-lives and neutron emission probabilities

Status of delayed-neutron precursor data: half-lives and neutron emission probabilities

Improving systematic predictions ofβ-delayed neutron emission probabilities

Background radiation from fission pulses

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