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Information Notice No. 89-08: Pump Damage Caused by Low-Flow Operation
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 January 26, 1989 Information Notice No. 89-08: PUMP DAMAGE CAUSED BY LOW-FLOW OPERATION Addressees: All holders of operating licenses or construction permits for nuclear power reactors. Purpose: This information notice is being provided to alert addressees to potential problems that may result from operation of centrifugal pumps at flows that can cause severe pump component damage. 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: Two events which resulted in pump damage are described below. Operations for extended periods at low-flow conditions apparently created hydraulic instability, resulting in pump damage from cavitation, pressure pulsation, and/or vibration. These events occurred at the Haddam Neck Plant and Susquehanna Steam Electric Station, Unit 1 (Susquehanna 1). The pump damage at the Haddam Neck plant was attributed to pressure pulsation and pump vibration, while at Susquehanna 1 it was the result of cavitation. Haddam Neck Plant Event: On February 4, 1988, an electric-driven fire pump was declared inoperable during a routine surveillance test when a high-amperage condition was noted. The normal indication of 200 amps initially increased to between 340 and 360 amps. The indication further increased to 1000 amps during a subsequent manual restart. The cause of the high amperage was attributed to physical damage to the stuffing box brass bushing in the upper shaft area. On the basis of the licensee's evaluation and its discussions with the manufacturer, the licensee concluded that prolonged operation of the pump at low flow may have caused the problem. Operation of the pump at or near the shut-off head had occurred during the containment integrated leak rate test. During the test, the fire pump operated in a low-flow mode, providing cooling water to the air compressors. 8901190418 .. IN 89-08 January 26, 1989 Page 2 of 3 Susquehanna 1 Event: While the plant was operating at full power on May 22, 1986, an over-current alarm for an emergency service water (ESW) pump was received in the control room. The pump was declared inoperable, placing the plant in a limiting condition for operation. Subsequent disassembly of the pump revealed that the bottom portion of the pump suction bell had separated from the pump body and fallen into the pump pit. In addition, the pump's impeller vanes were eroded through. Similar, but less severe, damage was found on the three other ESW pumps. A subsequent inspection of the residual heat removal service water (RHRSW) pumps found similar damage. The licensee determined that the damage to the ESW and RHRSW pumps was caused by recirculation cavitation, caused by operation of the pumps at flows significantly below their design flow rates. The ESW pumps are normally operated at 60 percent or less of their design flow of approximately 6,000 gallons per minute (gpm) per pump. When the loop sup- plying cooling water to the diesels is run with two operating pumps, each pump delivers approximately 3500 to 3900 gpm. The other loop, that does not serve the diesels is normally run with only one pump providing approximately 1000 to 1500 gpm. Operation at these conditions is believed by the pump vendor to cause recirculation cavitation. In addition, the RHRSW pumps are believed to have been operated at less than 50 percent of design flow most of the time. The licensee indicated that the cavitation damage can be avoided by operating the pumps at higher flows; specifically, operation at 75 to 100 percent of design flow is desirable. Discussion: These events illustrate that pump damage, caused by operating pumps at flows significantly below their design flow rates, has resulted, with slow deteri- oration of pump internals occurring over a long period. During the early phases of degradation, the pumps were still functional and remained operable. The pumps had to be disassembled before damage to the pump internals could be seen. Therefore, the routine pump surveillance tests, provided in the plant inservice test programs, may not be capable of detecting early component de- gradation. In addition, while operating the pumps in their normal, specified system operating ranges, plant personnel were not aware of a problem until actual failure of a pump occurred. It is most likely that pump degradation caused by low-flow operation will go undetected until total failure of the pump occurs, preventing the associated system from performing its safety function. . IN 89-08 January 26, 1989 Page 3 of 3 No specific action or written response is required by this information notice. If you have any questions about this matter, please contact the technical contact listed below or the Regional Administrator of the appropriate regional office. Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical Contact: Chuck Hsu, AEOD (301) 492-4443 Attachment: List of Recently Issued NRC Information Notices .. Attachment IN 89-08 January 26, 1989 Page 1 of 1 LIST OF RECENTLY ISSUED NRC INFORMATION NOTICES _____________________________________________________________________________ Information Date of Notice No._____Subject_______________________Issuance_______Issued to________ 89-07 Failures of Small-Diameter 1/25/89 All holders of OLs Tubing in Control Air, Fuel or CPs for nuclear Oil, and Lube Oil Systems power reactors. Which Render Emergency Diesel Generators Inoperable 89-06 Bent Anchor Bolts in 1/24/89 All holders of OLs Boiling Water Reactor or CPs for BWRs Torus Supports with Mark I steel torus shells. 89-05 Use of Deadly Force by 1/19/89 All holders of OLs Guards Protecting Nuclear for nuclear power Power Reactors Against reactors. Radiological Sabotage 89-04 Potential Problems from 1/17/89 All holders of OLs the Use of Space Heaters or CPs for nuclear power reactors and test and research reactors. 89-03 Potential Electrical 1/11/89 All fuel cycle and Equipment Problems major nuclear materials licensees. 89-02 Criminal Prosecution of 1/9/89 All holders of a Licensee's Former President U.S. NRC specific for Intentional Safety license. Violations 88-23, Potential for Gas Binding 1/5/89 All holders of OLs Supp. 1 of High-Pressure Safety or CPs for PWRs. Injection Pumps During a Loss-of-Coolant Accident 89-01 Valve Body Erosion 1/4/89 All holders of OLs or CPs for nuclear power reactors. 88-46, Licensee Report of Defective 12/30/88 All holders of OLs Supp. 2 Refurbished Circuit Breakers or CPs for nuclear power reactors. _____________________________________________________________________________ OL = Operating License CP = Construction Permit ..
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