Information Notice No. 87-51: Failure of Low Pressure Safety Injection Pump Due to Seal Problems
SSINS No.: 6835 IN 87-51 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 October 13, 1987 Information Notice No. 87-51: FAILURE OF LOW PRESSURE SAFETY INJECTION PUMP DUE TO SEAL PROBLEMS Addressees: All nuclear power reactor facilities holding an operating license or a con- struction permit. Purpose: This information notice is provided to alert addressees to potential failures of pumps as a result of problems with pump seals. Recipients are expected to review the information for applicability to their facilities and consider actions, if 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: On July 4, 1987, Palo Verde Unit 1 was at approximately 330 F with decay heat removal being provided by the Shutdown Cooling (SDC) system. The system uses either the low-pressure safety injection (LPSI) pumps or the containment spray (CS) pumps to circulate reactor coolant through a heat exchanger. With the "A" LPSI pump in service, the unit experienced a sudden electrical trip of the pump, accompanied by the presence of a small amount of smoke in the pump room. The unit was subsequently cooled down and an investigation into the pump failure initiated. The licensee found the "A" LPSI pump motor windings damaged and the pump shaft seized. Before the event, the licensee had observed that the pump shaft seal leakage was greater than normally expected. After the event, foreign material was observed in the motor lower bearing oil sight glass. The licensee solic- ited the support of several vendors in conducting the investigation. The pump is type 8x20 WDF, manufactured by Ingersoll Rand and supplied to the licensee by Combustion Engineering. The motor was manufactured by Westinghouse and the pump shaft seal was manufactured by the Durametalic Corporation of Kalamazoo, Michigan. There are no coolers for these seals at the three Palo Verde units. 8710070045 . IN 87-51 October 13, 1987 Page 2 of 3 Discussion: The licensee's investigation thus far has raised two concerns of a generic nature. Both concerns focus on the pump seal and, more specifically, on the EPT "O" rings and carbon seal faces used in the seal. The seal designation is a type PTO. The first concern is associated with the temperature to which the "O" rings and carbon seal faces are exposed. The SDC system is designed for 400�F and plant procedures allowed it to be placed in operation at temperatures up to 350�F. The environmental qualification data for the pump indicate that the "O" ring's qualified life at a temperature of 300�F is 99 days. "O" ring life apparently decreases rapidly at temperatures greater than 300�F and the carbon seal faces suffer accelerated wear at temperatures greater than 300�F. The implication is that prolonged operation of the SDC system at temperatures above 300�F could result in rapid failure of the seal. The second concern is associated with the application of a petroleum-based cleaning solvent or lubricant to the seal. A representative of the seal manufacturer visually inspected the "A" LPSI pump seal and observed that the "O" rings had expanded beyond their normal size, apparently as a result of the application of an inappropriate cleaning solvent or lubricant. This expansion may have caused the cracking of a carbon bushing component of the seal, which also was identified during the seal inspection. Although the manufacturer's drawing associated with the seal indicates that petroleum-based lubricants are not to be used on the "O" rings, it does not address the use of cleaning solvents. The licensee concluded that the failure of the seal on the "A" LPSI pump allowed water to spray up the pump shaft and enter the motor lower bearing, eventually leading to failure of the bearing. To preclude similar damage to the Unit 1 and 2 pump motors, the licensee installed water slingers on the shafts between the pumps and the motors. The licensee is also considering the installation of bearing isolators to shield the motor lower bearings from leakage. Because of the effects of temperature on pump seal life, the licensee established an administrative restriction that reactor coolant temperature must be reduced to 300�F or less before LPSI pumps are put in service. To prevent the misapplication of solvents or lubricants to the seals, the licensee modified the plant maintenance procedures to allow only the use of demineralized water. . IN 87-51 October 13, 1987 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 Regional Administrator of the appropriate regional office or this office. Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical Contacts: Stuart Richards, RV (415) 463-3853 Sam MacKay, NRR (301) 492-8394 Attachment: List of Recently Issued NRC Information Notices
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021