High Resolution Fission Cross Section of Uranium-235 from 20 eV to 100 keV

Lemley, J.R.; Keyworth, G.A.; Diven, B.C.

doi:10.13182/nse71-a19974

Cited by 24 publications

(6 citation statements)

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“…• Refs. [29,32,36,37] used a nuclear explosive as the neutron source and therefore have unquantifiable uncertainties in both the flight path used and the neutron fluence. Table III summarizes these experiments.…”

Section: Higher Energy Regionmentioning

confidence: 99%

Fluctuations in the U235 ( n , f ) cross section

Bertsch¹,

Brown²,

Davis³

2018

Phys. Rev. C

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We examine the autocorrelation function of the 235 U(n,f) reaction with a view to quantify the presence of intermediate structure in the cross section. Fluctuations due to compound nucleus resonances on the eV energy scale are clearly visible up to ≈ 100 keV neutron energies. Structure on the one-keV energy scale is not present as a systematic feature of the correlation function, although it is present in the data covering the region around 20 keV.

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Section: Higher Energy Regionmentioning

confidence: 99%

Fluctuations in the U235 ( n , f ) cross section

Bertsch¹,

Brown²,

Davis³

2018

Phys. Rev. C

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“…Data for this figure were taken from Lemley's recent measurements. 11 Earlier German work by Baumung et al 12 examined the region from 60 to 120 eV. We recommend here that the additional 2 ysec corresponding to 56 to 66 eV be included because the plutonium cross section is higher than the 235 U cross section by about a factor of three and the fissions induced will be a significant part (M4%) of the total.…”

Section: Age Expansionmentioning

confidence: 97%

Space- And Time-Dependent Slowing Down in Heavy Media.

Weisbin¹,

Forster²,

Smith³

et al. 1972

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To evaluate the potential of the lead slowing-down-time spectrometer quantitatively as a nuclear safeguards assay device, the time-, space-, &nd energy-dependent neutron diffusion equation has been solved for heavy moderators, and a FORTRAN-iV program, SLAHM (Slowlng-Down Analysis in heavy Moderators), was written to perform the required Integrations.Using this new calculational tool, spectral and spatial distributions have been obtained at a variety of times following introduction of a 14-MeV point source of neutrons into several different-sized lead assemblies. One can apparently achieve a 235 U/ 239 Pu discrimination ratio >5 with only limited self-shielding (even for high enrichment fuels) by examining the energy regions from 2.8 to 3.8 and 56 to 100 eV or, for highly enriched ylutonium breeder fuel, 2.8 ':o 3.8 and 56 to 66 eV. Note that this technique requires a 2-m cube. Further, the neutron population for energies below the inelastic threshold based upon exponencial attenuation (e~B T) involving the neutron age (T cm 2 ) must be estimated very carefully. The "true" age has been shown to be sensitive to both cross-section variation and the "free ride" affoided by the (n,2n) interaction.

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“…To overcome these difficulties different datasets must be compared between them, but only after a careful energy re-calibration and a suited re-normalisation. In Fig 1 can be seen some results from EXFOR [5] and [7][8][9][10][11][12] for two energy ranges. In both panels can be perceived that an evident correlation exists, even though the scatter of the points due to not having a correct calibration.…”

Section: Evaluation Proceduresmentioning

confidence: 99%

“…At this point, we realised that number of resonance peaks were composed of two or even few peaks not being resolved in one or other data files. This ambiguity required the comparison with other experiments and so the Bowman data [7], and sometimes also the Lemley data [8], were used to cross-check the assignment of the peaks. Moreover, the data from an experiment performed at CERN-nTOF using a FIC detector has been used too, as it can be taken as an independent experiment.…”

Section: Data Reduction and Conditioningmentioning

confidence: 99%

High-resolution evaluation of the U5(n,f) cross section from 3 keV to 30 keV

et al. 2019

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235 U neutron-induced fission cross-section is commonly used as reference for determining other isotope fission cross-section. However, below 150 keV this cross section is only included as Standard at the thermal point and recently its integral value between 7.8 eV and 11 eV [1]. The resolved resonance region, spanning up to 2.25 keV, has been reevaluated with high resolution in the last ENDF/B-VIII release [2] and a SAMMY resonance analysis was done by L. Leal et al. [3] including the CERN-nTOF experimental work of Paradela el al. [4] up to 10 keV, taken into account the IAEA Reference file.In this work the 235 U(n,f) low-background and high-resolution experimental data obtained at the CERN-nTOF facility is combined with previous high-resolution experimental data, in order to produce a very fine grid dataset with normalisation to the IAEA Reference file. The extremelyhigh energy calibration required to reproduce the resonance sharp profiles is based on the nTOF DAQ system with a resolution below 0.1% with reference to the 8.78 eV resonance and to the sharp Al(n,g) capture dip at 5.904 keV. The comparison of the so-evaluated profile with the experimental data and with the evaluated ones will be discussed.

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High Resolution Fission Cross Section of Uranium-235 from 20 eV to 100 keV

Cited by 24 publications

References 0 publications

Fluctuations in the U235 ( n , f ) cross section

Fluctuations in the U235 ( n , f ) cross section

Space- And Time-Dependent Slowing Down in Heavy Media.

High-resolution evaluation of the U5(n,f) cross section from 3 keV to 30 keV

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