Spectral Fine-Structure Effects on Material and Doppler Reactivity Worths

Greenspan, E.; Karni, Y.

doi:10.13182/nse79-a20609

Cited by 9 publications

(3 citation statements)

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“…which is the balance equation for the particular case of infinite homogeneous and isotropic media with isotropic scattering in the centre-of-mass system [7].…”

Section: Neutron Balance Adjoint Equations For Heterogeneous Mediummentioning

confidence: 99%

Adjoint neutron spectrum calculation for heterogeneous cells

Cardoso¹,

Martinez²,

Silva³

1996

J. Phys. D: Appl. Phys.

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Forward spectrum weighting has been used to generate broad-group cross sections. However, for some applications of perturbation theory, the adjoint spectrum is needed. Recently an approximate method has been proposed for the adjoint spectrum in a lattice cell, based on an equivalence principle. The approximations made can be avoided if the neutron energy dependence is treated in detail, and the neutron transport through the regions of a lattice cell is adequately represented. In this paper the neutron balance adjoint equations are derived for a heterogeneous unit cell based on the collision probabilities method, and the adjoint spectrum is calculated from this system of equations for different intervals of energy. Forward and adjoint spectra comparisons are done for a unit cell having in its inner region. In the numerical applications of the neutron balance adjoint equations the most important resonances of were considered. The results show significant variations between the forward and adjoint spectra, leading to remarkable differences in the effective resonance integrals.

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“…which is the balance equation for the particular case of infinite homogeneous and isotropic media with isotropic scattering in the centre-of-mass system [7].…”

Section: Neutron Balance Adjoint Equations For Heterogeneous Mediummentioning

confidence: 99%

Adjoint neutron spectrum calculation for heterogeneous cells

Cardoso¹,

Martinez²,

Silva³

1996

J. Phys. D: Appl. Phys.

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“…In literature, there are a variety of terms that are used to classify the mechanisms through which nuclear data uncertainties propagate through reactor lattice calculations, such as explicit, implicit, direct and indirect, broad-structure, fine-structure, and others [2][3][4][5]. For the purposes of this paper there are four high-level mechanisms by which uncertainty in microscopic cross-section will be propagated to the solutions of lattice physics calculations ( ∞ and homogenized few-group properties).…”

Section: Introductionmentioning

confidence: 99%

“…Such effects are present in both continuous energy and multigroup solutions of the transport equation. The third and fourth mechanisms arise from the treatment of energy in the transport equation in discretized energy form and are elsewhere classified as spectral fine-structure effects [2][3][4], as they involve the perturbation of the neutron flux on a scale much smaller than energy group widths. One of the first available tools for uncertainty analysis with a rigorous treatment of sensitivities that include implicit effects was developed by Oak Ridge National Laboratory (ORNL) and implemented in the code TSUNAMI [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

The Dilution Dependency of Multigroup Uncertainties

Ball

McEwan

Novog

et al. 2014

Science and Technology of Nuclear Installations

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The propagation of nuclear data uncertainties through reactor physics calculation has received attention through the Organization for Economic Cooperation and Development—Nuclear Energy Agency’s Uncertainty Analysis in Modelling (UAM) benchmark. A common strategy for performing lattice physics uncertainty analysis involves starting with nuclear data and covariance matrix which is typically available at infinite dilution. To describe the uncertainty of all multigroup physics parameters—including those at finite dilution—additional calculations must be performed that relate uncertainties in an infinite dilution cross-section to those at the problem dilution. Two potential methods for propagating dilution-related uncertainties were studied in this work. The first assumed a correlation between continuous-energy and multigroup cross-sectional data and uncertainties, which is convenient for direct implementation in lattice physics codes. The second is based on a more rigorous approach involving the Monte Carlo sampling of resonance parameters in evaluated nuclear data using the TALYS software. When applied to a light water fuel cell, the two approaches show significant differences, indicating that the assumption of the first method did not capture the complexity of physics parameter data uncertainties. It was found that the covariance of problem-dilution multigroup parameters for selected neutron cross-sections can vary significantly from their infinite-dilution counterparts.

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Sensitivity Functions for Uncertainty Analysis

Greenspan¹

1982

Advances in Nuclear Science and Technology

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Spectral Fine-Structure Effects on Material and Doppler Reactivity Worths

Cited by 9 publications

References 0 publications

Adjoint neutron spectrum calculation for heterogeneous cells

Adjoint neutron spectrum calculation for heterogeneous cells

The Dilution Dependency of Multigroup Uncertainties

Sensitivity Functions for Uncertainty Analysis

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