Heterogeneity effects on the detector field of view in the radial direction in BWRs

Conference · Fri Nov 01 04:00:00 EST 1985 · Trans. Am. Nucl. Soc.; (United States)

OSTI ID:5741237

Antonopoulos-Domis, M; Skarpeta, K

Flow patterns in boiling water reactors (BWRs) may be identified from neutron noise signals excited by void fluctuations propagating along the fuel bundles surrounding the bypass region in which the neutron detectors are placed. The system's relaxation lengths, thus the detector's field-of-view, depend on the heterogeneity of the core. In all theoretical works, heterogeneity is accounted for with the Feinberg-Galanin method. In the present work, the authors use an explicitly heterogeneous one-dimensional model in the radial direction to investigate heterogeneity effects on the detector field-of-view and in particular on the total relaxation length, since it is the total width of the detector field-of-view that is important, due to attenuation (local) or multiplication (global). In the model, the core is composed of fuel plates of finite width h/sub f/ and of coolant channels of width h/sub m/. Despite its obvious drawbacks, the one neutron energy model used here enables the qualitative investigation of the effect of heterogeneity. The relevant equations for the Green's function G(x,x/sub 0/,jw) are solved numerically with second-order finite differences; G is very sensitive to deviations from criticality, which is ascertained via appropriate adjustment of the factor n, the number of neutrons produced per thermal neutron absorbed in the fuel.

• Research Organization: Aristotelian Univ., Greece
• OSTI ID: 5741237
• Report Number(s): CONF-851115-
• Conference Information: Journal Name: Trans. Am. Nucl. Soc.; (United States) Journal Volume: 50
• Country of Publication: United States
• Language: English

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