The specification of neutron flux and nuclear cross-sections in reactor calculations

Westcott, C. H.

doi:10.1016/0891-3919(55)90017-6

Cited by 31 publications

(23 citation statements)

References 12 publications

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“…Our thermal fission cross section value is in good agreement with Browne's one [1]. From our experimental data, we have also calculated the Westcott g f factor [7], defined as: Using T=293.6K and E 0 =E T =25.3meV, we have found: g f =0.939±0.019, which can be compared with the recommended value proposed by Mughabghab [8]: g f =0.954±0.033.…”

Section: Measurement With the 245-cm Samplesupporting

confidence: 73%

“…(1) and (2), N U and N B are the number of uranium and boron atoms, ϕ (En ) is the neutron flux, ε B and ε f are the detection geometry factors, σ f is the neutron induced fission cross section and σ B is the 10 B(n,α) 7 Li reaction cross From the above equations and using the JEFF3.1 cross sections for σ f and σ B , it is possible to extract the ε f / ε B ratio. Then, the 235 U(n,f) cross section can be deduced by applying the following equation:…”

Section: Measurement With the 235-u Samplementioning

confidence: 99%

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²⁴⁵CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION

et al. 2010

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A new cross section measurement for the 245 Cm(n,f) reaction in the thermal energy region has been performed at the GELINA neutron facility of the Institute for Reference Materials and Measurements (IRMM) in Geel, Belgium. The energy of the neutrons is determined applying the time of flight method using a flight path length of about 9 m. In the present work, the incident neutron energy covers 10 meV up to a few eV. A 98.48% enriched 245 Cm sample was mounted back-to-back with a 10 B sample in the centre of a vacuum chamber together with two surface barrier detectors positioned outside the neutron beam. One detector measured the 10 B(n,α) 7 Li reaction products for the neutron flux determination, while the second one registered the 245 Cm(n,f) fragments. In this way, the neutron flux can be determined simultaneously with the fission fragments. A control measurement has been performed replacing the 245 Cm sample with a 235 U sample in order to check that the well-known 235 U(n,f) cross section can be reproduced. Our measurement yielded a 245 Cm(nth,f) cross section of 2131±43±173 b and a Westcott factor gf=0.939±0.019.

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Section: Measurement With the 245-cm Samplesupporting

confidence: 73%

Section: Measurement With the 235-u Samplementioning

confidence: 99%

²⁴⁵CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION

et al. 2010

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“…The dashed curve is for an equilibrium incident-neutron spectrum with an effective neutron temperature T--310K and the solid curve shows the result of including the epithermal tail. Experiments show that this tail begins rather abruptly at an energy of about 5ksT (Westcott, 1955). For simplicity, we assume that it begins at 5kBT exactly.…”

Section: Compressi Onmentioning

confidence: 99%

“…The neutrons in a nuclear reactor are not in true thermodynamic equilibrium with the moderator. Nevertheless, the velocity distribution of the neutrons is found to be very nearly Maxwellian up to energies of about 5ksT (Westcott, 1955) and the effective neutron temperature in a heavy-water reactor is typically 10 to 30K higher than the temperature of the moderator (Johansson, Lampa & Sj6strand, 1961;Bigham, Chidley & Turner, 1961). Thus,f(2) is well represented by expression (28) for wavelengths 2 > 2T/51/2.…”

Section: Figure Of Meritmentioning

confidence: 99%

Bragg Reflection in Mosaic Crystals. II. Neutron Monochromator Properties

Sears¹

1997

Acta Cryst Sect A

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In the preceding article, the general solution of the Darwin equations has been obtained for a mosaic crystal slab for both the Laue case (transmission geometry) and the Bragg case (refection geometry). This now allows the calculation, for the first time, of the reflectivity of an absorbing crystal of finite thickness in situations where the Bragg planes make an arbitrary angle with the surface of the crystal. In this paper, these results are applied to a numerical calculation of the reflecting properties of a number of commonly used neutron monochromator crystals. The incident-neutron flux is taken to be Maxwellian with an epithermal tail and it is investigated how the various properties depend on the neutron wavelength, the crystal thickness, the mosaic spread and the angle that the Bragg planes make with the surface of the crystal. It is found, for example, that for asymmetrical reflections gains in flux of 25 to 50 % or more can easily be achieved for a wide range of wavelengths in crystals with the kinds of thickness and mosaic spread that are available in practice.

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“…Por isso, é necessário fazer algumas considerações sobre a forma das funções σ(E) e ϕ(E). Historicamente, as primeiras considerações (também conhecidas por convenções) sobre tais funções foram levantadas por Westcott em 1955(WESTCOTT, 1955, WESTCOTT et al, 1958 …”

Section: A Taxa De Reação Por Núcleounclassified

Implementação do método k0-INAA no laboratório de análise por ativação com nêutrons do IPEN utilizando o programa k0-IAEA. Aplicação à análise de amostras geológicas

Mariano¹

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The specification of neutron flux and nuclear cross-sections in reactor calculations

Cited by 31 publications

References 12 publications

²⁴⁵CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION

²⁴⁵CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION

Bragg Reflection in Mosaic Crystals. II. Neutron Monochromator Properties

Implementação do método k0-INAA no laboratório de análise por ativação com nêutrons do IPEN utilizando o programa k0-IAEA. Aplicação à análise de amostras geológicas

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The specification of neutron flux and nuclear cross-sections in reactor calculations

Cited by 31 publications

References 12 publications

245CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION

245CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION

Bragg Reflection in Mosaic Crystals. II. Neutron Monochromator Properties

Implementação do método k0-INAA no laboratório de análise por ativação com nêutrons do IPEN utilizando o programa k0-IAEA. Aplicação à análise de amostras geológicas

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²⁴⁵CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION

²⁴⁵CM FISSION CROSS SECTION MEASUREMENT IN THE THERMAL ENERGY REGION