Nuclear Data for235U,238U, and239Pu in the Unresolved Resonance Region

Vankov, Anatoli; Ukraintsev, V. F.; Yaneva, N.; Toshkov, S.; Mateeva, A.

doi:10.13182/nse87-a16372

Cited by 6 publications

(3 citation statements)

References 4 publications

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“…In our model the average total cross section has the standard Hauser-Feshbach form σ (E) = σ (E) and the resonance ladder (ε λ , ξ λn ) accounts effectively for the resonance parameter fluctuations in the average reaction cross section σc . The Doppler broadening of resonances is accounted for by statistical modelling [11]. The results obtained with this model are in good agreement with the calculations of NJOY [12], where the single level Breit-Wigner formalism of Wigner's R-matrix theory is applied.…”

Section: Numerical Procedures For Calculation Of Cross Sections and T...supporting

confidence: 76%

Cross section structure of²³²Th in the unresolved resonance region

Koyumdjieva¹,

Janeva²,

Luk'yanov³

2010

J. Phys. G: Nucl. Part. Phys.

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An analysis of the 232Th neutron total and neutron capture cross sections has been performed in the energy region between 4 keV and 140 keV. The experimental data are analysed in terms of average resonance parameters utilizing a new statistical method for modelling of the resonance cross section structure in the region of experimentally unresolved resonances. The method exploits the characteristic function of the R-matrix elements distribution in Wigner's theory of nuclear reactions. To improve the representation of the 232Th cross section, the neutron strength functions for s- and p-waves are fitted to the experimental data in order to reproduce their observable fluctuations in (4–140) keV. Our method offers analytical expressions even for nonlinear functionals (observables) of neutron cross section as a transmission ratio. These functionals are incorporated into the evaluation process as a simple benchmark test for verification of the 232Th resonance parameters.

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Section: Numerical Procedures For Calculation Of Cross Sections and T...supporting

confidence: 76%

Cross section structure of²³²Th in the unresolved resonance region

Koyumdjieva¹,

Janeva²,

Luk'yanov³

2010

J. Phys. G: Nucl. Part. Phys.

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“…This idea is applied in the code HARFOR for computing in the unresolved range the bothaveraged in energy group cross sections and the corresponding self-shielding coefficients for our functionals [15]. The results of HARFOR agree in general with these obtained by the codes GRUCON [16], NJOY [17] and by resonance sampling Monte Carlo method [8]. The version of our scheme for two neutron channels case was developed as well [18].…”

Section: Generalized Statistical Approachmentioning

confidence: 59%

“…At the same time the general consideration about this structure and accessible data for thick filter neutron transmission, where exp(−nσ) exp(−n σ ), (see fig. 1), prove the need to take into account the resonance effects in this region (up to ∼100 keV for heavy nuclei and ∼ MeV for medium ones) [6][7][8][9].…”

Section: Resonant Structurementioning

confidence: 99%

Resonance data for self-shielding problems

Janeva

Luk'yanov

Koyumdjieva

2007

Nd2007

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Abstract. The investigation of resonance self-shielding effects in macroscopic medium is important for the physics of nuclear reactors and shielding. The degree of consistency of evaluated resonance cross sections data and the requirements to the accurate presentation of self-shielding effects can be estimated by using the simplest benchmark data for resonance averaged functions of neutron transmission and self-indication cross section at arbitrary filter thickness n. We report the developed (for nonfissile nuclei) methods for description of cross sections and their functionals in the unresolved resonance range that aim to estimate properly the self-shielding effects and reveal the resonance structure in averaging intervals (groups).

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Characteristic functions in the statisticalR-matrix theory

Koyumdjieva

Luk'yanov

Janeva

1995

Z. Physik A - Hadrons and Nuclei

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Abstract. The characteristic functions of the statisticalWigner's R-matrix for the case of one-channel scattering in competition with multichannel radiative capture have been drown. Different approximations and their relevance in neutron physics applications are discussed. PACS: 25.40.NyThe R-matrix theory of nuclear resonance reactions is a widely used mathematical method for treating the problem of neutron cross section parametrization. This method makes possible the description of resonance cross sections in relatively large energy interval using R-matrix:where E.e and 7;.c are real and energy independent parameters associated with the set of the resonances considered and the summation is performed over it [1][2][3][4].The rank of the R-matrix is equal to the number of reaction channels, excluding the radiation channels, which are accounted for by the imaginary term F./in the denominator. The non-resonant part of the R-matrix is usually included in the phase of the potential scattering and is omitted here [1][2][3].The reaction cross section is defined by the scattering matrix of the same rank [1,2]:where ~oc are the phases of the potential scattering and p is the diagonal matrix of the penetrability factors. The total cross section o-, the reaction cross section o-c and the radiative capture cross section o-.y for a given system of resonances with a fixed total angular momentum J and parity 7r are defined aswhere g(J) is a spin statistical factor [1][2][3][4]. It is possible to determine a complete set of resonance parameters in the R-matrix (Eq. (1)) in the resolved resonance region and this is the aim of the multilevel analysis of the resonance cross sections. But for the higher energies the experimental resolution is not sufficient for the identification of individual resonance levels and here the cross section analysis permits the determination of only average over many levels parameters strength functions ?2,/D,7~/D (D is the average level spacing for a given system J~).At the same time, besides the data on average cross sections and @c), a lot of experimental information on average transmission -

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Nuclear Data for²³⁵U,²³⁸U, and²³⁹Pu in the Unresolved Resonance Region

Cited by 6 publications

References 4 publications

Cross section structure of²³²Th in the unresolved resonance region

Cross section structure of²³²Th in the unresolved resonance region

Resonance data for self-shielding problems

Characteristic functions in the statisticalR-matrix theory

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Nuclear Data for235U,238U, and239Pu in the Unresolved Resonance Region

Cited by 6 publications

References 4 publications

Cross section structure of232Th in the unresolved resonance region

Cross section structure of232Th in the unresolved resonance region

Resonance data for self-shielding problems

Characteristic functions in the statisticalR-matrix theory

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Product

Resources

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Nuclear Data for²³⁵U,²³⁸U, and²³⁹Pu in the Unresolved Resonance Region

Cross section structure of²³²Th in the unresolved resonance region

Cross section structure of²³²Th in the unresolved resonance region