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Information Notice No. 89-77: Debris in Containment Emergency Sumps and Incorrect Screen Configurations
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 November 21, 1989 Information Notice No. 89-77: DEBRIS IN CONTAINMENT EMERGENCY SUMPS AND INCORRECT SCREEN CONFIGURATIONS Addressees: All holders of operating licenses or construction permits for pressurized water reactors (PWRs). Purpose: This information notice is intended to alert addressees to potential problems resulting from inadequate housekeeping and insufficient surveillance of containment emergency recirculation sumps. It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice do not constitute NRC requirements; therefore, no specific action or written response is required. Description of Circumstances: During the recovery period after a loss-of-coolant accident, following injection of emergency coolant from the refueling water storage tank, water is collected within the containment emergency recirculation sump to be pumped back into the reactor coolant system. The emergency sump structures are designed to provide for a continuous flow of water to the recirculation pumps by preventing the entry of air or debris, thereby protecting the recirculation pumps from damage due to loss of net positive suction head or entrained solid material. To provide guidance for sump designs, the NRC staff issued Regulatory Guide 1.82, "Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident," dated June 1974, which was revised in November 1985. Regulatory Guide 1.82 emphasizes the need for inservice inspection of emergency core cooling sump components, including debris interceptors, vortex suppressors, and sump outlets. The staff also expressed the need for emergency sumps to be protected from debris in Standard Review Plan 6.2.2 and Generic Letter 85-22, "Potential for Loss of Post-LOCA Recirculation Capability Due to Insulation Debris Blockage." PWR standard technical specifications and the technical specifications of many plants require visual inspection of the containment emergency sump and verification that the suction inlets to the recirculation pumps are not restricted by debris. Sump components, including trash racks and screens, must also be inspected. The surveillance interval is typically 18 months. On June 16, 1988, following a recirculation flow verification test, loose parts and debris were found in the containment sump, the recirculation pumps, and the suction piping of Surry Units 1 and 2. Some of the items were large enough to 8911150013 . IN 89-77 November 21, 1989 Page 2 of 2 have caused pump damage or flow degradation. In addition, some of the sump screens were found to have gaps, which could have allowed additional loose material to enter the sump. One screen was found to be missing. Following investigation of the event by the licensee and the NRC staff, the licensee incorporated sump surveillance requirements similar to those of PWR standard technical specifications into their plant procedures. The NRC issued a notice of violation and proposed imposition of a $50,000 civil penalty. On July 8, 1989, the licensee for the Trojan facility discovered numerous items in the containment sump. The NRC was informed of this condition on July 12, 1989. On July 14, 1989, after containment had been closed out, an NRC inspector and the licensee found additional debris. On July 17, 1989, the top sump screen and portions of the inner screen were found to be missing. On July 19, 1989, the NRC identified additional missing and damaged inner sump screens. Debris had previously been found in the Trojan sump during a 1988 outage. In 1980, a residual heat removal pump was jammed by a welding rod between the impeller and the casing ring demonstrating the potential safety significance of loose debris in the containment emergency sump. The Trojan Technical Specifications contain periodic inspection requirements for the containment emergency sump and sump screens. The licensee's inspection procedures for the containment emergency sump did not have adequate inspection criteria. The NRC issued a notice of violation and proposed imposition of a $280,000 fine for a severity level II violation. As a result of the problems identified at the Trojan facility, the NRC resident inspector recently performed an inspection of the Diablo Canyon sump and sump screens, including a comparison of the design drawing to the actual arrangement of the sump screens. Debris was found in the Unit 1 and Unit 2 sumps, and the sump screen arrangement on the design drawing was found to be incorrect. The sump screens were not configured in accordance with the FSAR drawing. The Diablo Canyon Technical Specifications contain periodic inspection requirements for the containment emergency sump and sump screens. Initial findings indicate that plant procedures for sump inspection were not sufficient or detailed enough to assure adequate inspections. This information notice requires no specific action or written response. If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate NRR project manager. Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical Contact: Walton Jensen, NRR (301) 492-1190 Attachment: List of Recently Issued NRC Information Notices .
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