An Analysis of Semiscale Mod–2C S–FS–1 Steam Line Break Test Using RELAP5/MOD2 (NUREG/IA–0052, AEEW–R2476)

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Publication Information

Date Published: March 1992

Prepared by:
J. M. Rogers

United Kingdom Atomic Energy Authority
Central Electricity Generating Board
Barnwood, Gloucester GL4 7RS
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)

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Availability Notice


An analysis has been performed of Semiscale Steam Line Break Test, to support the validation of RELAP5/MOD2.

Previous analyses of steam line breaks in the UK have made conservative assumptions about the lack of water carryover in the break discharge. This analysis utilises more sophisticated steam generator models attempting to follow the complex two phase phenomena that occur in this transient to obtain a more realistic assessment of its consequences.

Modelling, particularly of the phase separation process, is outlined. Problems with initial calculations are explained, and their solutions detailed. The main conclusion drawn is that although the calculations were acceptable overall, the carryover of water during the first seconds of the transient was too great. In addition the heat transfer degraded too quickly, resulting in a smaller than observed primary cooldown, which would in a real plant result in an underestimate of the potential reactivity insertion. These deficiencies lead to the recommendation that the implementation of interphase drag, and steam generator heat transfer warrant further study.

The work reported in this document was carried out for CEGB GDCD Barnwood under Contract Number N/F 5176

AEE Winfrith

March 1989

AEEW - R 2476

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