United States Nuclear Regulatory Commission - Protecting People and the Environment

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
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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

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