The CSNI/PWG-1 international task group on ECCS reliability

Conference · Fri Mar 01 04:00:00 EST 1996

OSTI ID:269676

Sandervag, O; Riekert, T; Serkiz, A; Hyvarinen, J

A steam line loss-of-coolant accident (LOCA) occurred when a safety relief valve inadvertently opened in the Barseback-2 nuclear power plant. The steam jet stripped fibrous insulation from adjacent pipework. Part of that insulation debris was transported to the wetwell pool and clogged the intake strainers for the drywell spray system after about one hour. Although the incident in itself was not very serious, it revealed a weakness in the defense-in-depth concept which under other circumstances could have led to failure of the emergency core cooling system (ECCS) to provide water to the core. Before the Barseback-2 LOCA, international regulators of nuclear power plants and the nuclear power plant industry had considered safety questions related to strainer clogging as resolved. Many European countries had followed the guidance for strainers in pressurized water reactors (PWRs) contained in United States Nuclear Regulatory Commission`s (USNRC) Regulatory Guide 1.82, Water Sources for Long Term Recirculation Cooling Following a Loss-of-Coolant Accident, 1974. However, data obtained from European experimental programs carried out in the late seventies to determine the performance of strainers indicated that this guide was not adequate. In addition, Swedish plant owners had used this guidance to judge performance of emergency core cooling systems (ECCS) in their plants. Analyses at that time had indicated that strainer clogging, if occurring at all, would at least not occur during the first ten hours after a LOCA. Since operation of the ECCS would be needed for a long time, backflushing capabilities and monitors of pressure drop across the strainers were installed in older Swedish BWR plants with small strainer areas. These actions were judged to be adequate compliance with the revised USNRC Regulatory Guide 1.82, Rev. 1, issued in 1985. Safety questions related to strainer clogging were considered to have been resolved until the incident happened in Barseback-2.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Office of Nuclear Regulatory Research; Brookhaven National Lab., Upton, NY (United States)
• OSTI ID: 269676
• Report Number(s): NUREG/CP--0149-Vol.3; CONF-9510156--Vol.3; ON: TI96007986
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
22 GENERAL STUDIES OF NUCLEAR REACTORS
BWR TYPE REACTORS
ECCS
FLOW BLOCKAGE
MECHANICAL FILTERS
RELIABILITY