Testing of the Quickest-Ultimate Algorithm to Solve the Dissolved Convection Equation During a Boron Dilution Test at the PKL Facility
NURETH-14 - 2011 September 25-30

Presented at:
2011 September 25-30
Toronto, Canada
Session Title:
B13-4 Development, Assessment and Applications of TRACE

Jordi Freixa (Paul Scherrer Institut)
Davide Bertolotto (Paul Scherrer Institut)
Annalisa Manera (Paul Scherrer Institut)


Rapid boron dilution transients have shown the need for accurate knowledge of the solute particle distribution in pressurized water reactors (PWR), since its concentration would affect the reactivity of the system. Particularly relevant are scenarios where a separation between high and low borated water takes place. For instance, low borated plugs can be formed in the loop seals of a PWR during small-break-loss-of-coolant-accidents (SBLOCA) where reflux-condensation conditions are kept for a long time. Since online boron concentration measurement is impractical in the primary system of PWR plants, the formation of such a plug would take place unnoticed by the operators. The thermal-hydraulic system code TRACE, developed by US-NRC, may be used to track the boron concentration along the system. However, in the TRACE code the dissolved solute convection equation is solved by employing a first-order upwind scheme. The use of such a scheme is known to introduce high numerical diffusion when a gradient of boron concentration flows through the system. In order to more accurately simulate rapid boron dilution transients by using TRACE, the high order explicit scheme QUICKEST together with the ULTIMATE limiter were implemented in the TRACE code. The model was tested in simple geometries and in the coupling between the TRACE code and a CFD code. A final step is presented in this paper where the new model is tested against an experiment on boron dilution carried out at the integral test facility PKL (AREVA), within the OECD/NEA PKL project.

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