United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 90-39: Recent Problems with Service Water Systems

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555

                                June 1, 1990


Information Notice No. 90-39:  RECENT PROBLEMS WITH SERVICE WATER 
                                   SYSTEMS 


Addressees:

All holders of operating licenses or construction permits for nuclear power 
reactors.

Purpose:

This information notice is intended to alert addressees to potential 
problems resulting from the failure of service water systems to provide an 
adequate and reliable supply of cooling water to safety-related structures, 
systems, and components.  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:

On March 9, 1990, the licensee for the Clinton power plant reported problems 
with the distribution of flow in the essential service water system.  The 
staff of the Nuclear Regulatory Commission (NRC) described those problems in 
Information Notice 90-26, "Inadequate Flow of Essential Service Water to 
Room Coolers and Heat Exchangers for Engineered Safety-Feature Systems."  
Recently, service water system problems have been identified at seven other 
nuclear power plants.

On March 14, 1990, while both units were at full power, the licensee for the 
Surry power plant performed a quarterly test on one of three diesel-driven 
emergency service water pumps.  After the diesel engine failed to start, the 
licensee found that the dampers in the air supplies to all three engines 
were closed.  The engines started immediately when the dampers were opened.  

At the Peach Bottom power plant, the emergency service water system is 
shared by Units 2 and 3 and is supplied with water from the Susquehanna 
River.  On March 2, 1990, the NRC staff completed a safety system functional 
inspection of the emergency service water system.  The inspectors identified 
certain concerns related to the capability of the system to perform its 
intended function.  In response, the licensee completed tests and an 
analysis of the system and concluded that the system was operable with Unit 
3 at power while Unit 2 was in its scheduled mid-cycle outage with its 
emergency service water loads isolated.  On March 21, 1990, the licensee 
reported that emergency service water flows to 



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various Unit 2 components were inadequate for design basis conditions due to 
accumulations of silt and corrosion products in the emergency service water 
piping.  Corrective actions by the licensee included inspection and cleaning 
of piping and heat exchangers, throttling of the flow to the emergency 
diesel generators to allow more flow to other components, and isolation of 
the flow to redundant Unit 2 room coolers for emergency core cooling systems 
again to allow more flow to other components.  The licensee concluded that 
these actions assured the operability of the emergency service water system 
with both Units 2 and 3 in operation.  An enhanced surveillance and test 
program for the emergency service water system was implemented pending 
completion of replacement of emergency service water piping for Unit 2 
during the next refueling outage.

On March 23, 1990, while the River Bend power plant was in an outage, Region 
IV reported continuing service water problems at the plant.  Use of acidic 
well water when the system was first filled resulted in severe corrosion 
problems.  Water chemistry was corrected, and the acidic attack has stopped.  
However, microbiologically-induced corrosion has been present and is 
continuing.  From ultrasonic measurements, the licensee believes that the 
pitting rate is 24 mils per year.  The licensee plans to chemically clean 
the system or replace piping as necessary. 

During December, 1988, the licensee for the Haddam Neck power plant found 
that the flow of service water to all four of the containment air coolers 
was unacceptably low.  The low flow was caused by a uniform buildup of silt 
and corrosion products in the tubes of the coolers.  After the licensee 
cleaned the tubes, the flow increased by approximately 50 percent.  On March 
26, 1990, during the current refueling outage, the licensee found that 
service water flow to one of the two emergency diesel generators was less 
than the manufacturer's recommended value and that the heat removal rate for 
all of the containment air coolers was several percent less than the value 
assumed in the accident analysis for the plant.  The licensee intends to 
correct these problems before returning to power. 

In June, 1989, during a self-initiated assessment of the service water 
system, the licensee for the Farley power plant identified a potential 
design inadequacy concerning the flow of service water to safety-related 
loads during certain accident scenarios.  The licensee reported the 
potential inadequacy and implemented compensatory measures pending further 
evaluation.  On March 27, 1990, the licensee reported that their evaluation 
confirmed that during the accident scenarios, service water flow to some 
safety-related loads would not be adequate without operator action.  The 
licensee has revised procedures as necessary to alert operators to the need 
for action if such events were to occur.

The Perry power plant has three emergency diesel generators and three 
service water pumps for Unit 1.  The pumps take suction on the forebay which 
receives lake water through two traveling trash screens which are installed 
in parallel.  On April 3, 1990, Unit 1 was operating at full power when a 
gasket failed on the discharge strainer for emergency service water pump A.  
Water spraying from the strainer wetted several components including a 
control power transformer and the motors for traveling screen A and screen 
wash pump A.  Emergency service water pump A and the emergency diesel 
generator that it cools were 
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declared inoperable.  Further, screen wash pump B had been technically 
inoperable since November, 1989, pending delivery and installation of parts.  
However, emergency service water pump B was operating and screen B was 
clear.  

At the Fitzpatrick power plant, on April 11, 1990, while the unit was in a 
refueling outage, the licensee reported that silt had been found in check 
valves in emergency service water lines to the seal coolers for two pumps in 
the residual heat removal system.  The licensee concluded that the silt 
could have prevented the residual heat removal system from fulfilling its 
safety function.

Discussion:

On July 18, 1989, the NRC staff issued Generic Letter 89-13, "Service Water 
System Problems Affecting Safety-Related Equipment," to all holders of 
operating licenses and construction permits for nuclear power plants.  The 
letter addressed continuing problems with service water systems in meeting 
the requirements of General Design Criteria 44, 45, and 46 in Appendix A of 
10 CFR 50 and Section XI, "Test Control," in Appendix B of 10 CFR 50.  On 
April 4, 1990, the NRC staff issued Supplement 1 to the generic letter.  The 
supplement contains questions from the industry that were posed during 
workshops held in Philadelphia, Atlanta, Chicago, and Denver and the answers 
that were provided by representatives of the NRC.

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:  Roger W. Woodruff, NRR
                    (301) 492-1180


Attachment:  List of Recently Issued NRC Information Notices
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