Investigation of the Uncertainty of Governing Equation Systems in Thermalhydraulic Calculation
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

Tomasz Skorek (Gesellschaft fuer Anlagen- und Reaktorsicheheit mbH)
Bernhard Krzykacz-Hausmann (Gesellschaft fuer Anlagen- und Reaktorsicheheit mbH)
Henrique Austregesilo (GRS)


Investigation of the effect of uncertainty of the governing equation system on the results of the

code ATHLET has been performed on the basis of an uncertainty and sensitivity analysis of the

ROSA/LSTF SB-PV-09 experiment. The analysis has been conducted for the 5 and 6 equation

systems in ATHLET. The results confirmed that for the selected test case the uncertainties

resulting from both momentum equation approximations are very similar. The analysis also

showed that some output variables are influenced by approximation of momentum equation, e.g.

water level in the core whereas other output variables like maximum clad temperature are not. In

some cases the uncertainty of closure relations contributes considerably more to uncertainty of

the results than the uncertainty of momentum equation approximation.

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