Scaling effects in intermediate break LOCA scenario

Abstract

Scaling studies in the field of nuclear thermal hydraulics were conducted to analyze and extrapolate phenomenology from Integral Test Facilities (ITFs) to operating full size Nuclear Power Plants. The objective of this paper is to show the impact of the scale on the relevant Figures of Merit (FOM) during accidental sequences in an Intermediate Break Loss-of-Coolant Accident (IBLOCA) with four different Power-to-volume scaling (PtV) rationales at scales from 0.2 to 100 times the scale of the ROSA Large Scale Test Facility (LSTF) ITF a scaled down design according to the PtV scaling methodology from a Westinghouse (w)-type 4 loops Pressurized Water Reactor as a reference plant. For this purpose, a Power-to-Volume Scaling Tool (PVST) developed and validated by the Advanced Nuclear Technologies “Universitat Politècnica de Catalunya” (ANT-UPC) team is used to generate RELAP5 input decks at different scales and different scaling rationales. The experiment selected for the analysis is Test 2 of the LSTF/NEA/ROSA-2 project, for which the ANT-UPC team has a previously qualified nodalization serving as a base nodalization. The effects of scale in Test 2 are analyzed by plotting the different key performance variables of the most important phenomena as a function of the scale. In general, no significant differences were observed for most of the FOM for all the phenomenology, however some small scaling effects were observed regarding the conservation of the Froude number. The scaling analysis of the core uncovery phenomena is presented in this article since this is considered the most relevant phenomena to nuclear safety of this test.