Published 2008 | Version v1
Miscellaneous Open

The Procedure for Determination of Special Margin Factors to Account for a Bow of the VVER-1000 Fuel Assemblies

  • 1. Russian Research Center 'Kurchatov Institute', 1., Kurchatov sq., 123182 Moscow (Russian Federation)

Description

Starting from 1980's, the problem of bow of the VVER-1000 reactor FAs and the effect of that on the operational safety is being discussed. At the initial period of time, the extension of time for dropping control rods of the control and protection system associated with this bow posed the highest threat. Later on, new more rigid structures were developed for FAs that eliminated the problems of control rods. However, bow of the VVER-1000 reactor FAs is observed up to now. The scale of this bow reduced significantly but it still effects safety. Even a minor bow available may lead to the noticeable increase of power of individual fuel pins associated with the local variation of the coolant amount. This effect must be taken into account on designing fuel loadings to eliminate the exceeding of set limitations. The introduction of additional special margins is the standard method for taking this effect into account. The present paper describes the conservative technique for the assessment of additional margins for bow of FAs of state-of-the-art designs. This technique is employed in the VVER-1000 reactor designing. The chosen conservatism degree is discussed as well as the method for its assurance and acceptable ways for its slackening. The example of the margin evaluation for the up-to-date fuel loading is given. (authors)

Availability note (English)

Available from INIS in electronic form

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Additional details

Publishing Information

Imprint Pagination
12 p.
Report number
INIS-CH--09-IYNC-2008-183

Conference

Title
International Youth Nuclear Congress 2008
Acronym
IYNC 2008
Dates
21-26 Sep 2008
Place
Interlaken (Switzerland)

INIS

Optional Information

Notes
7 refs.