Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
April 24, 1990
Information Notice No. 90-26: INADEQUATE FLOW OF ESSENTIAL SERVICE
WATER TO ROOM COOLERS AND HEAT EXCHANGERS
FOR ENGINEERED SAFETY-FEATURE 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 using the wrong flow and pressure drop relationship
in establishing adequate flow of essential service water to room coolers for
engineered safety-feature systems and from failing to establish or maintain
balanced flows in essential service water systems. 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 reactor at the Clinton Power Station was in cold
shutdown, and the licensee was taking action to implement the
recommendations contained in Generic Letter 89-13, "Service Water System
Problems Affecting Safety-Related Equipment." The licensee discovered that
the flow of essential service water being supplied to several room coolers
serving safety-related equipment was approximately half of the design flow.
The safety-related equipment included components in the high-pressure and
low-pressure core spray systems, the low-pressure injection system, the
residual heat removal system, the standby gas treatment system, the
combustible gas control system, and the nuclear protection system. After
discovering the problem, the licensee declared these systems to be
inoperable. The room coolers were supplied to the Clinton Power Station by
American Air Filter, a subsidiary of Snyder General Corporation.
Before initial operation of the Clinton Power Station, the licensee obtained
the relationship of the flow and pressure drop on the water side of the room
coolers from the supplier. Plant personnel adjusted valving to establish
the pressure drop across each room cooler which would provide the design
flow. Plant personnel did not actually measure the flow to each room
cooler.
9004180107
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IN 90-26
April 24, 1990
Page 2 of 3
On March 9, 1990, the licensee discovered that the relationship between flow
and pressure drop for the room coolers was wrong and that flows of essential
service water to the room coolers were too low. Subsequently, the licensee
also found that the flows of essential service water to several other
coolers and heat exchangers were too low.
To balance the flow of essential service water through the system, plant
personnel measured the flow using qualified instrumentation and adjusted
flows to the room coolers according to these measurements. In some
instances, the adjusted flows to specific components were somewhat less than
design flows. However, the licensee is performing analyses to determine
whether these flows are acceptable. Modifications to the updated final
safety analysis report will be submitted as necessary.
Discussion:
American Air Filter has supplied room coolers to approximately 50 nuclear
power plants including the Clinton Power Station. The room coolers consist
of bundles of folded tubes with supply and return headers at the ends of the
tubes. American Air Filter supplies the room coolers either with or without
pairs of cleanout plugs at the bends in the tubes. At design flow, room
coolers with cleanout plugs have a significantly greater pressure drop
across the tube bundle than room coolers without cleanout plugs.
On April 3, 1990, Illinois Power Company, licensee for the Clinton Power
Station, stated in a report submitted to NRC under 10 CFR 21.21 that
pressure drop data provided by American Air Filter for 22 of 23 room coolers
was incorrect. Twenty-two room coolers had cleanout plugs while the 23rd
room cooler did not. On April 5, 1990, Illinois Power Company submitted a
licensee event report which indicated that actual flows for the room coolers
with cleanout plugs ranged from 10 percent to 80 percent less than the
design flows.
The licensee event report also indicated that 7 of 25 cooling components
provided by vendors other than American Air Filter and connected to the
essential service water system had flows that were less than the design
flows. For these cooling components, actual flows ranged from 2 percent to
42 percent less than the design flows. The components include: two residual
heat removal (RHR) heat exchangers supplied by General Electric Company, two
RHR pump seal coolers supplied by Byron Jackson, a switchgear heat removal
condenser supplied by Carrier Corporation, a fuel pool cooling and cleanup
heat exchanger supplied by Yuba Heat Exchanger, and a standby gas treatment
system radiation monitor cooler supplied by Sentry Equipment Corporation.
Other components served by the essential service water system were receiving
excess flow. These flows ranged up to 213 percent more than design flows.
Failure to properly balance flows of essential service water during pre-
operational testing or failure to maintain balanced flows can lead to
degradation of safety-related equipment.
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IN 90-26
April 24, 1990
Page 3 of 3
This information notice requires no specific action or written response. If
you have 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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