Thermalhydraulic calculations

Background documents developed during the EOF development process, justifications for application of the reference development method, relevant supporting studies, specific thermalhydraulic calculations, verification of EOF strategies and validation reports, training materials, etc. 

Subchannel analysis codes, ASFRE for single-phase flow and SABENA for two-phase flow, have been developed for the purpose of predicting fuel element temperature and thermalhydraulic characteristics in the FBR fuel assemblies. ASFRE has the detailed wire-spacer model called distributed flow resistance model, which calculates the effect of wire-spacer on thermalhydraulics. Also planer and porous blockage models are implemented for fuel assembly accident analysis. In this reporting period, three dimensional thermal conduction model was used for the evaluation of local blockage in a fuel assembly. In addition, the comparison of pressure losses in the assembly with the water experimental data has been performed. Regarding SABENA, based on the two-fluid model, no activity is reported. 

The iodine chemistry model INSPECT and the aerosols/chemistry code VICTORIA have been inserted recently. We expect that ESTER-VICTORIA, because it is tightly coupled to the thermalhydraulics, will be easier to run than the old stand-alone version and, in some laboratories at least, may become the standard version. At this stage once the necessary drivers have been developed and tested it should be possible to calculate an entire Phebus test, from bundle to containment and ESTER will be the only European code able to do so. The JRC may then insert models for chemical kinetics and for nucleation developed under SCA, and possibly a special-purpose model for the difficult zone just above the bundle in Phebus. 

The experimental results and a comparison with ATHLET calculations are shown in Fig. 6. From sensitivity studies it has been evaluated that the thermalhydraulic codes like ATHLET or CATHARE are calculating well the integral power transferred, but deviate substantially in the in-tube heat transfer by condensation processes. Therefore, special tests with a single tube only and an improved instrumentation were performed. In addition, special tests and measurements for 3D-temperature fields in the water pool have been performed, see the isothermes in Fig. 7 for one of the tests. 

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