A least-squares fit of thermal data for fissile nuclei

Divadeenam, M.; Stehn, J. R.

doi:10.1016/0306-4549(84)90002-1

Cited by 24 publications

(10 citation statements)

References 72 publications

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“…235 U PFNS mean fission neutron energy <E>=2.03(2) MeV was used in Ref. [8]. This value is discrepant with the latest recommendation of <E>= 2.00(1) MeV for thermal-neutron induced fission of 235 U [11][12][13] based on a non-model least-square fit of thermal-neutron induced fission data.…”

Section: Introductionmentioning

confidence: 41%

“…Lemmel already pointed out in 1975 an existing discrepancy between results of the fit using microscopic data only (2200 m/s), and the overall result that employs both microscopic and Maxwellian data, especially for the 235 U thermal constants [6]. Lemmel evaluations have been followed by efforts by Divadeenam and Stehn [8,9] and Axton [10]. a e-mail: Roberto.CapoteNoy@iaea.org…”

Section: Introductionmentioning

confidence: 99%

“…They assumed Maxwellian prompt fission neutron spectra (PFNS) in their analysis of reactor spectra (see Table 26, p.386 of Ref. [8]); a similar approach was used in previous analysis by Lemmel [6,7]. 235 U PFNS mean fission neutron energy <E>=2.03(2) MeV was used in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…In a comprehensive paper published in 1984 Divadeenam and Stehn used both Maxwellian and 2200 m/s data to derive a new set of TNC constants [8]. They assumed Maxwellian prompt fission neutron spectra (PFNS) in their analysis of reactor spectra (see Table 26, p.386 of Ref.…”

Section: Introductionmentioning

confidence: 99%

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New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

et al. 2017

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Abstract. An IAEA project to update the Neutron Standards is near completion. Traditionally, the Thermal Neutron Constants (TNC) evaluated data by Axton for thermal-neutron scattering, capture and fission on four fissile nuclei and the total nu-bar of 252 Cf(sf) are used as input in the combined least-square fit with neutron cross section standards. The evaluation by Axton (1986) was based on a least-square fit of both thermal-spectrum averaged cross sections (Maxwellian data) and microscopic cross sections at 2200 m/s. There is a second Axton evaluation based exclusively on measured microscopic cross sections at 2200 m/s (excluding Maxwellian data). Both evaluations disagree within quoted uncertainties for fission and capture cross sections and total multiplicities of uranium isotopes. There are two factors, which may lead to such difference: Westcott g-factors with estimated 0.2% uncertainties used in the Axton's fit, and deviation of the thermal spectra from Maxwellian shape. To exclude or mitigate the impact of these factors, a new combined GMA fit of standards was undertaken with Axton's TNC evaluation based on 2200 m/s data used as a prior. New microscopic data at the thermal point, available since 1986, were added to the combined fit. Additionally, an independent evaluation of TNC was undertaken using CONRAD code. Both GMA and CONRAD results are consistent within quoted uncertainties. New evaluation shows a small increase of fission and capture thermal cross sections, and a corresponding decrease in evaluated thermal nubar for uranium isotopes and 239 Pu.

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Section: Introductionmentioning

confidence: 41%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

et al. 2017

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“…There are also many cases where the original value is corrected with a newer reference value by Axton (e.g., half-life adopted in sample mass determination, average fission neutron energy for fission neutron detector efficiency calibration). Such values corrected or derived from the literature values are often taken by Axton from Sjöstrand and Story [10], Lemmel [3] and Divadeenam [11] as noted by Axton in Appendix 4 of Ref. [7].…”

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confidence: 99%

Experiments in the EXFOR library for evaluation of thermal neutron constants

et al. 2017

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Abstract. E.J. Axton's experimental database adopted in evaluation of thermal neutron constants by himself and also by a recent project to update the IAEA Neutron Standard was checked against the experimental literature and EXFOR library. We discovered that many data are found neither in the EXFOR library nor in the articles quoted by Axton due to various reasons. This paper summarizes the status of the experimental data cited by Axton in the experimental literature as well as in the EXFOR library.Cross sections for thermal (2200 m/s) neutrons are fundamental neutron-induced reaction data, which have been evaluated at the IAEA since the pioneering works by Westcott [1], Hanna [2] and Lemmel [3,4]. In a typical evaluation of the thermal neutron constants (TNC) within the current IAEA Neutron Standards [5], 25 constants (elastic, fission and capture cross sections, absorption and fission g-factors, and total fission neutron multiplicities of 233 U, 235 U, 239 Pu and 241 Pu at the thermal energy as well as 252 Cf spontaneous total fission neutron multiplicity) measured both in differential (monoenergetic) and integral (broad spectrum) experiments are included in a simultaneous generalized least-squares analysis by the GMA code [5]. Recent TNC evaluations for update of the IAEA Neutron Standard are based on the comprehensive work by Axton [6][7][8]. However, Axton's experimental database (Table 1 of [8]) contains many data not available in the EXFOR library [9]. We have reviewed Axton's experimental database to identify the data missing in EXFOR and possible experimental corrections.The results are summarized in Table 1, where• "Quantity" gives the quantity given in the Axton's database, where (1) a, f, s, sm and γ stand for absorption, fission, scattering, scattering for rolled metal and capture; (2) 9, 0, 1, 2, 3, 4, 5, 52 for 239,240,241,242 Pu, 233,234,235 U and 252 Cf; (3) σ and η for 2200 m/s cross section and eta,ν for total fission neutron multiplicity,σ andη for Maxwellian spectrum averaged σ and η at T = 20 • C), g is the Westcott a

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Introduction

Sukhoruchkin¹,

Soroko²,

Gunsing³

et al. 2009

Neutron Resonance Parameters

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A least-squares fit of thermal data for fissile nuclei

Cited by 24 publications

References 72 publications

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

Experiments in the EXFOR library for evaluation of thermal neutron constants

Introduction

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A least-squares fit of thermal data for fissile nuclei

Cited by 24 publications

References 72 publications

New fit of thermal neutron constants (TNC) for233,235U,239,241Pu and252Cf(sf): Microscopic vs. maxwellian data

New fit of thermal neutron constants (TNC) for233,235U,239,241Pu and252Cf(sf): Microscopic vs. maxwellian data

Experiments in the EXFOR library for evaluation of thermal neutron constants

Introduction

Contact Info

Product

Resources

About

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data

New fit of thermal neutron constants (TNC) for^233,235U,^239,241Pu and²⁵²Cf(sf): Microscopic vs. maxwellian data