Validation of severe accident codes against Phebus FP for plant application (PHEBEN2)

FISA-2003, 10-13 novembre 03, Luxembourg
K. Müller, S. Dickinson, C. de Pascale, N. Girault, L. Herranz, F. De Rosa, G. Henneges, J. Langhans, C. Housiadas, V. Wichers, J. Birchley, S. Paci, F. Martin- Fuertes, A. Sartmadjiev, I. Turcu, I. Ivanov, G. Horvath.

The main objectives focused on the source term aspects of the integral Phebus FP experiments are:

• Validation of integral codes for LWR severe accident analysis
• Application of detailed codes and use of the partners’ expertise to understand and quantify the physical and chemical phenomena underlying the Phebus results
• Validation of detailed codes and identification of necessary modeling improvements
• Development and application of assessment criteria for integral codes
• Identification of strengths and weaknesses of the codes for plant applications as well as definition of guidelines for optimum code use for the various applications.

The major results obtained from the analyses of the PHEBUS FP tests are:

• Integral codes predicted rather well both the hydrogen release from the bundle and the total release of high volatile fission products
• Remarkable progress was obtained in the prediction of the deposited aerosol mass in the circuit and in the containment. A new thermophoretic has been developed to estimate more accurately aerosol retention in the steam generator
• Containment analyses of both lumped-parameter and 3D nature resulted in a good consistency with thermal-hydraulic data. Aerosol behaviour estimated from lumped-parameter codes showed a satisfactory agreement with the experimental data
• Iodine chemistry codes highlighted the substantial role played by silver in the experimental scenario, as observed experimentally, however strong limitations exist in predicting the gaseous iodine evolution in the containment atmosphere

In addition, the modelling of safety-relevant phenomena has been discussed in detail and a set of assessment criteria are under development for integral code applications.
Sixteen partner organizations are involved in the project including the four new ones from the New Associated States. The project started on 1st March 2000 and will end on 30th August 2004. All the produced deliverables are available for each partner at the On-line Data Information Network (ODIN) via the address http://odin.jrc.nl/.