On a Best-Estimate Approach to the Calculation of Dryout Probability During BWR Transients
NURETH-14 - 2011 September 25-30

Presented at:
2011 September 25-30
Toronto, Canada
Session Title:
O4-1 BEPU (Best Estimate code Plus Uncertainty) method, CSAU, Statistical Methods

Carl Adamsson (Westinghouse Electric Sweden AB)
Jean-Marie Le Corre (Westinghouse Electric Sweden AB)


A method is proposed whereby uncertainty of any dryout margin measure (figure of merit)

may be quantified when the only experimental information available for validation is whether

dryout has occurred or not. The method does not involve the heater temperature, except as a

discrete dryout indicator. This is an advantage when analysing anticipated operational

occurrences for which the acceptance criterion refers exclusively to the probability of dryout

occurrence. The derived uncertainty provides a direct relation between the simulated dryout

margin and the aforementioned probability. Furthermore, the method, which is based on

logistic regression, has been designed to be consistent with more common parametric methods

of uncertainty analysis that are likely to be used for other parts of a thermal hydraulic model.

One example is provided where the method is utilized to assess statistical properties, which

would have been difficult to quantify by other means.

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