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A previous study on the problems of scaling and extrapolation of experimental results indicated the necessity to overcome some uncertainty in the achievable code accuracy when applied to full size reactor systems. The empirical approach in simulating interfacial relationships within systems behaviour codes in combination with the liberty of nodalisation requires a careful assessment of the overall validity of the code verification concept. Several new test facilities are presently under construction to study fluid-dynamic effects of interest for the behaviour of PWRs under small break LOCA conditions in a larger dimension and with somewhat modified scaling considerations. The test results expected from these new facilities may be useful to assess the overall validity of the analytical simulation concept of the applied computer codes. Test facilities of interest within the European Community are the item - LOBI Test Facility (vol. scaling 1/700) at JRC- Ispra item - SPES Test Facility (vol. scaling 1/425) in Italy item - BETHSY Facility (vol. scaling 1/100) in Francepar and outside Europe the item - ROSA IV Facility (vol. scaling 1/50) in Japan.par Main objective of the study was the elaboration of a guideline for the particular requirements of meaningful counterpart testing with the final aim to qualify the overall validity of code simulation concepts and the expected predictive accuracy of code applications for full size prototype PWRs. Based on an overall assessment of the available code validation literature the need for a commonly applicable Analytical Simulation Model'' (ASM) has been identified. Main elements of the ASM are the availability of a transient two-phase flow code, of a suitable nodalisation strategy for the involved test rigs and the prototype plant and the proper choice of empirical correlations which must systematically cover the entire range of scaling. A suitable nodalisation strategy might either consist of an applicable standard nodalisation for all involved test rigs and the prototype plant or at least a standardized nodalisation of the components. Nodalisation strategies must be problem-oriented and will in general be different for different codes. Natural circulation flow experiments are proposed to serve as test goal for the first series of counterpart tests (CPT) to be performed within the three European test facilities mentioned above. Common operating and boundary conditions should be specified in close connection to those applied for the execution of the LOBI-test A2-77A. As second objective for a CPT activity a small break loss of coolant experiments has been proposed, for which a 5% break size should be specified. This value may be large enough to produce a pronounced fluiddynamic transient sufficiently large to overcome possible distortions caused by scaling effects of the smaller test rigs. The third envisaged objective is a loss of feedwater (LOFW) experiment which addresses recovery procedures (e.g. feed and bleed) of full-size power reactors for an incident with a relatively high probability of occurrence. Such a CPT activity could be oriented on the specification of the test BT-OO of the LOBI-B test matrix. Corresponding tests are also planned within the BETHSY and SPES experimental matrix. The counterpart testing activity will require close international cooperation and technical coordination of the test specification.

Additional information

Bibliographic Reference: EUR 6540 EN (1988) MF, 113 PP., ECU 8, BLOW-UP COPY, ECU 15, AVAILABILITY: EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
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