Top-down scaling methodology from the LSTF facility to a three loop PWR plant applied to a SBLOCA event - The ROSA 1.2 test

Abstract

[EN] The scaling methodology describes quantitatively the possible differences in the behavior between a reduced size experimental facility and a full scale commercial plant for a determined transient. Then scaling is an essential tool in the design and operation processes of a reduced size facility in order to be able to simulate the behavior of large commercial plants. Since, in this way, it is possible to advance in the development of safety systems, prediction of situations likely to produce accidental sequences, etcetera. Therefore the scaling calculations should be carried out from the earlier stages of the experimental facility conceptual design, so that its experimental data results could be directly extrapolated to a commercial plant. Evidently, the scaling analysis has to be carried out for the experimental test plans, in order to check the capacity to transpose the experimental data of the reduced size facilities to the commercial plants. Consequently, the major objective of the scaling methodology is to evaluate quantitatively the applicability of small size test facility data to predict the behavior of full size commercial plants.

The top-down scaling step of the H2TS scaling methodology, between the LSTF experimental facility and a Pressurized Water Reactor of Siemens-KWU type for the ROSA 1.2 test, has been carried out along this document to evaluate the global system behavior. In order to achieve this main purpose, the general description of both facilities, the transient scenario, and the results of the scaling analysis for a small break loss of coolant accident (SBLOCA) in the hot leg are shown. The scaling analysis methodology used is the top-down global system analysis, from which, it is intended to establish thermal-hydraulic similarity between a scaled facility and a full scale industrial plant. With this aim, the accidental sequence of the ROSA 1.2 test has been divided into its five main time phases, analyzing separately each of them. In each phase the similarity groups (pi-monomials and pi-monomial groups) have been defined and applied. In such a way that only a reduced number pi-monomials are needed to develop the scaling methodology, in addition, many of these similarity groups appear in several phases.

The key aspect of this document is to show the applicability of the top-down scaling analysis methodology to a commercial plant of a different type to that of the reference NPP at which the experimental facility replicates, i.e., test carried out in a Westinghouse type experimental facility, scaling analysis applied to a Siemens-KWU type. In such a way that, it has been proved the possibility to use the measurements facility of different type of the reference plant for an accidental scenario, in particular, applicability of a SBLOCA test data from an experimental facility of type Westinghouse to a commercial plant of type Siemens-KWU.