Scaling effect in an intermediate break LOCA scenario

Abstract

Scaling studies in the field of nuclear thermalhydraulics have been carried out to analyze and extrapolate phenomenology from Integral Test Facilities (ITFs) to operating full size Nuclear Power Plants (NPP). The Power-to-Volume (PTV) scaling methodology is used in this paper to analyze the scaling distortions of this method. Small scaling distortions are expected to reveal an effect in the Figures of Merit (FOM) selected for the analyzed scenario.

The objective of this paper is to study the impact of the scale on relevant FOM during accidental sequences with 4 different scaling rationales at scales from 0.2 to 100. For this purpose, a Power-to-Volume Scaling Tool (PVST), developed and validated by the Advanced Nuclear Technologies at UPC, is used to generate RELAP5 input decks at any scale user defined. The RELAP5 input deck of the Large Scale Test Facility (LSTF) is used in this article. The LSTF is a scaled down ITF that was designed according to the PTV scaling methodology from a reference (w)-type 4 loops PWR. The effect of the scale and scaling rationales during Intermediate Break LOCA (IBLOCA) sequences are analyzed by means of RELAP5 simulations for Test 2 of LSTF/NEA/ROSA-2 project. Therefore, the analysis underlines the importance of the scaling distortions.

The conservation of the Froude number in the cold leg and scaling effects of heat losses are not significant to the phenomenology along the scales analyzed for the core dryout based on the studied FOMs. The Froude number in hot and cold legs have shown negligible effects in the overall phenomenology of the core dryout in a cold leg IBLOCA transient for all the analyzed range of scale and scaling rationales.