Fission chambers for space effect reduction in the application of the area method

Janczyszyn, J.; Domańska, Grażyna; Stanisz, Przemysław

doi:10.1016/j.anucene.2018.01.025

Cited by 3 publications

(7 citation statements)

References 4 publications

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“…The presented results are a continuation of previously reported work [7]. In this earlier stage, we proposed to use fission chambers with the sensitive material composed of two nuclides, one fissionable and the other fissile.…”

Section: Introductionsupporting

confidence: 82%

“…The role of the detector material in the Sjöstrand method has already been mentioned by Talamo et al [9] and Janczyszyn et al [7]. In the present article, the authors propose a new method of designing the quasi-mono-isotopic detector set for a new subcritical reactor.…”

Section: Discussionmentioning

confidence: 71%

“…The sensitivity of the difference k kcode  k eff to changes in system reactivity was tested for some detectors containing mixtures of two isotopes, described by Janczyszyn et al [7]. Small variations of reactivity were modelled by changing the depth of CR insertion, while bigger reactivity changes were resulted from fuel enrichment variation simulation.…”

Section: Sensitivitymentioning

confidence: 99%

“…Because of the diffi culties found in applying the mixed fi ssile-fi ssionable sensitive detector material, presented earlier [7], we propose the idea of single isotope fi ssion chambers, or other types of neutron detectors, to be used for subcriticality determination in a given reactor system. Each detector material is optimized for the detector position in the reactor.…”

Section: Monoisotopic Chambersmentioning

confidence: 99%

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Fission chambers for space effect reduction in the application of the area method: A new approach

2020

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The possibility of preparing fission chambers for the experimental determination of subcriticality without time-consuming corrections has been presented. The reactor detectors set consists of monoisotopic chambers. Each chamber is intended for a specific position in the system. Individual weights, rated a priori for all detectors in their positions, allow for quick calculation of whole system subcriticality. The inconveniences related to the spatial effect are minimized. This is achieved by computational simulation of the area method results, for each detector position and all possible fissionable and fissile nuclides. Next, one nuclide is selected, specific for the given position, presenting the smallest difference from the MCNP KCODE precisely estimated kkcode. The case study is made using the model of VENUS-F core.

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Section: Introductionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 71%

Section: Sensitivitymentioning

confidence: 99%

Section: Monoisotopic Chambersmentioning

confidence: 99%

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Fission chambers for space effect reduction in the application of the area method: A new approach

2020

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“…Because of the difficulties observed in the application of mixtures of fissile and fissionable sensitive detector materials presented earlier [13], we proposed the idea of fission chambers, or other types of neutron detectors, with a single isotope, to be used for subcriticality determination [9]. For each detector, the material optimized for the given detector position in the reactor was selected from a set of nuclides.…”

Section: Mono Isotopic Chambersmentioning

confidence: 99%

Sensitivity of the area method with mono isotopic fission chambers to reactivity changes in subcritical nuclear reactors

2021

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High-level waste is an important safety issue in the development of nuclear power. A proposed solution is the transmutation of waste in fast reactors. The exclusion of the risk of supercriticality by using subcritical reactors is currently under development. Controlling the subcriticality level in such reactors presents difficulties. A problem is posed by the so-called space effect observed when using in reactors many neutron detectors in different locations of the core and reflector. Reactivity obtained from measurements, for example, by the Sjöstrand method, differs by nonnegligible values. Numerical corrections can partially improve this situation. The use of a monoisotopic fission chamber set, designed for a given reactor, when each chamber is intended for a specific position in the system, can improve the situation. A question arises about the sensitivity of the results to reactivity changes. This issue is analyzed by computer simulation for possible fissionable and fissile nuclides for the total range of control rod insertion, changes in reactor fuel enrichment, and fuel temperature. The tested sensitivity was satisfactory at most levels from several dozen to several hundred pcm. A case study was conducted using the VENUS-F core model.

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Simulation of the Measured Reactivity Distributions in the Subcritical MYRRHA Reactor

Janczyszyn,

Domańska,

Oettingen

2024

Energies

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The designed MYRRHA reactor, in its subcritical version, will be equipped with a set of detectors monitoring its condition by measuring the current value of negative reactivity, which is a crucial parameter for its safe operation. In subcritical systems, accurate and precise measurement of negative reactivity is disturbed by the so-called spatial effect, i.e., the response of detectors depends on their placement in the reactor core. This paper focuses on the Monte Carlo simulations of reactivity measurements using the area method for natU, 238U, 241Am, 239Pu, and 232Th detectors. The simulations were performed in six positions with increasing distance from the center of the core and at three axial levels. The obtained results allow for selecting optimum locations for detectors and detector nuclides in terms of the accuracy of reactivity measurement and illustrate the dependence of the reactivity on the distance. Additionally, the possibility of using 103Rh in self-powered neutron detectors was investigated. The influence of spatial effect in calculations using the area method was directly indicated in the MYRRHA reactor core for chosen isotopes and in-core positions. The results closest to true values were obtained for the second fuel assembly for 239Pu, and the third fuel assembly for natU, 238U, 232Th, and 241Am; thus, these nuclides and positions should be preferred when selecting detectors for MYRRHA.

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Fission chambers for space effect reduction in the application of the area method

Cited by 3 publications

References 4 publications

Fission chambers for space effect reduction in the application of the area method: A new approach

Fission chambers for space effect reduction in the application of the area method: A new approach

Sensitivity of the area method with mono isotopic fission chambers to reactivity changes in subcritical nuclear reactors

Simulation of the Measured Reactivity Distributions in the Subcritical MYRRHA Reactor

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