Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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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