United States Nuclear Regulatory Commission - Protecting People and the Environment

Analysis of LOBI Test BLO2 (Three Percent Cold Leg Break) with RELAP5 Code (NUREG/IA-0036)

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Publication Information

Date Published: March 1992

Prepared by:
A.H. Scriven

Central Electricity Generating Board
Technology Planning and Research Division
Central Electricity Research Laboratories
Kelvin Avenue
Leatherhead Surrey KT2275E
United Kingdom

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
under the International Thermal-Hydraulic Code Assessment
and Application Program (ICAP)

Published by:
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555

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Abstract

The test BL02 was a UK specified test conducted on the electrically heated 2 loop test system at Ispra, North Italy as part of the LOBI 'B' series of tests sponsored by the Joint European Research Commission.

The pretest calculations for this test were performed with the RELAP5 MOD1 code, and the post-test analysis was carried out using RELAP5 MOD2. Comparisons between the codes predictions and the test data are given, and for the case of the post-test MOD2 calculation, detailed studies of the codes performance in a number of areas are included.

Of particular note in this test is the stratified break offtake condition for part of the test, the sensitivity to accurate bypass modelling and the clearance of both loop seals early in the transient. The correct modelling of these inter-related effects is a good test for the code.

This test also benefits from a reliable and accurate break mass flow measurement system, installed since the International Standard Problem (ISP18) test, which enables better determination of the boundary conditions of the test.

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