United States Nuclear Regulatory Commission - Protecting People and the Environment

Assessment Study of RELAP5/MOD2, CYCLE 36.04 Based on Spray Start-up Test for DOEL-4 (NUREG/IA-0020)

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Publication Information

Date Published: July 1989

Prepared by:
P. Moeyaert, E. Stubbe

TRACTEBEL
B-1040 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

This report presents an assessment study for the code RELAP-5 M0D-2 based on a pressurizer spray start-up test of the Doel-4 power plant.

Doel-4 is a three loop WESTINGHOUSE PWR plant ordered by the ESES utility with a nominal power rating of 1000 MWe and equipped with preheater type E steam generators.

A large series of commissionning tests are normally performed on new plants, of which the so called pressurizer spray and heater test (SU-PR-01) was performed on February 2nd 1985. TRACTEBEL, being the Architect-Engineer for this plant was closeiy involved with all start-up tests and was responsible for the :inal approval of the tests.

This particular start-up test has been selected as the first code assessment study for this plant, as it can be considered as a kind of separate effect test, principally involving the phenomena in one plant component i.e. the pressurizer. The pressurizer plays a vital role in determining the plant behaviour during operational transients and accidents. Hence a correct simulation of the pressurizer (including surge line, spray- and heater control) is essential in trying to simulate the plant behaviour under off- normal conditions. Although the pressurizer spray and heater systems do not strictly have a safety function, they have a large impact on the operational flexibility of the plant (i.e. plant pressure control). The code used for assessment is RELAP-5 MOD-2 CYCLE 36.04, which was installed on a CYBER 176 comouter.

This pressurizer spray test involves the following important features for code assessment:

  • Full scale
  • Pressurizer thermalhydrau!ics : which involves the thermal non equilibrium phenomena leading to condensation (by spray) and evaporation (by heaters).
  • Surgeline thermalhydraulics : form loss factors and counter current flow behaviour.
  • Structural heat from pressurizer shell and heaters.
  • Assymmetric loop behaviour when one or two reactor coolant pumps are tripped, leading to reversed loop flow.
  • Single phase pump behaviour (coastdown).

This code assessment work is performed by TRACTEBEL and is based on the plant recorded data for this test.

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