United States Nuclear Regulatory Commission - Protecting People and the Environment

Assessment Study of RELAP5/MOD2 Cycle 36.04 Based on the DOEL-4 Manual Loss of Load Test of November 23, 1985 (NUREG/IA-0043)

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Publication Information

Date Published: March 1992

Prepared by:
E.J. Stubbe, P. Deschutter

TRACTEBEL
Place du Trone, 1
B-1000 Brussels
Belgium

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 loss of external load transient test conducted on the Doel- 4 power plant has been analysed on the basis of a high quality data acquisition system.

A detailed numerical analysis of the transient by means of the best estimate code RELAP-5 MOD-2 is presented, covering the most important plant components and systems, and complemented by imposed boundary conditions, taken from the recordings, when necessary.

Comparison of recorded and calculated data show that

  • The RELAP-5 code is capable to simulate the basic plant behaviour which allows a deeper insight in the physical phenomena.
  • Some deficiencies affecting either the model or the code are observed, they could be attributed
    • to the absence of structural heat simulation of the steam generators
    • to acoustic phenomena which influence the steam generator level sensor
    • to excessive interphase drag in the steam generator at low void regimes.
  • Typical characteristic features of the plant can better be quantified such as
    • strong thermal coupling between feedwater flow and cold leg temperature for a preheater type steam generator
    • Delay between feedwater flow variations and level swell and shrink response.
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