Extension of Differential Operator Method to Inhomogeneous Problems with Internal and External Neutron Sources

Sakamoto²

2019

A method for Monte Carlo sensitivity analyses of -eigenvalue (prompt neutron time decay constant) in a subcritical system is developed using the first-order differential operator sampling (DOS) method. The first-order derivative of -eigenvalue with respect to nuclear data is calculated using the DOS method that includes the capability of calculating perturbed source effect. This paper is an extension of the author's previous work for development of the sensitivity analysis method for k eff -eigenvalue. Unlike the conventional Monte Carlo method for -eigenvalue calculation that uses the power iteration of fission sources, this paper introduces a recently developed "time source method". The "time source method" has a weakness for a void-containing subcritical system, which is overcome by assigning a virtual total cross section in the void region. The perturbed source effect, which is caused by the change of nuclear data in a subcritical system, can be calculated by two methods, the source perturbation iteration method and the superhistory method. The source perturbation iteration method is superior in terms of computation efficiency, but a huge computer memory is required. The superhistory method

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Section: Differential Operator Sampling Methodsmentioning

confidence: 99%

A Monte Carlo technique for sensitivity analysis of alpha-eigenvalue with the differential operator sampling method

Sakamoto²

2019

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“…A method implemented in the SERPENT code is based on the "collision-history based method" where all cross sections involved in the sensitivity calculations are artificially increased. Another method that this paper focuses on is the differential operator method (Rief, 1984;McKinney and Iverson, 1996;Densmore et al, 1997;Nagaya and Mori, 2005;Raskach, 3 2009; Raskach, 2010;Jinaphanh et al, 2016). The unique feature of the differential operator method is that the calculation of the adjoint flux can be circumvented and the first derivative of keff-eigenvalue with respect to nuclear data can be estimated directly.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the differential operator method is applicable to estimating responses of wide range of calculation characteristics: keff, reaction rates and their ratios both in the eigenvalue problem and in the problem of a subcritical system driven by an external neutron source (Raskach, 2010). On the other hand, the IFP method is applicable to computing keff derivatives and sensitivities only.…”

Section: Introductionmentioning

confidence: 99%

Eigenvalue sensitivity analysis capabilities with the differential operator method in the superhistory Monte Carlo method

2018

This paper applies the first-order differential operator method to the Monte Carlo keff-eigenvalue sensitivity analyses. The effect of the perturbed fission source distribution due to the change of a cross section on the sensitivity coefficients can be accurately estimated by introducing the source perturbation iteration method. However, a prohibitively huge memory is required for the source perturbation iteration method if a large number of sensitivity coefficients are calculated at the same time. For a reduction

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Monte Carlo perturbation methods using “virtual density” theory for calculating reactivity due to geometry change

Sakamoto

2018