Information Notice 1998-25, Loss of Inventory from Safety-Related Closed-Loop Cooling Water Systems
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001 July 8,1998 NRC INFORMATION NOTICE 98-25: LOSS OF INVENTORY FROM SAFETY-RELATED,
CLOSED-LOOP COOLING WATER SYSTEMS
Addressees
All holders of operating licenses for nuclear power reactors, except those licensees who have
permanently ceased operations and have certified that fuel has been permanently removed
from the reactor vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to potential inoperability of safety-related, closed-loop cooling water systems due to
loss of inventory from excessive leakage combined with the absence of a reliable and timely
annunciation and/or makeup system. 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 are not NRC requirements; therefore, no specific action or written response Is required.
Description of Circumstances
Palisades
On January 1, 1998, Palisades Nuclear Plant was operating at 100 percent power when a leak
from the safety-related, dosed-loop component cooling water (CCW) system at the 'A'
radioactive waste evaporator distillate cooler Increased from about 100 ml/min to about
757 I/min (200 gpm,) which was more than the makeup capacity to the CCW system. The leak
emptied the CCW surge tank and resulted in a reduction in the normal CCW discharge header
pressure from about 929 kPa (135 psia) to 777 kPa (113 psia). The licensee identified the
source of the leak and isolated the applicable components within about 15 minutes. The
licensee did not observe any abnormal component temperatures and did not Identify any effect
on the primary coolant pump seals. After Isolating the leak, the operators refilled and vented
the CCW system and returned It to service.
Calvert Cliffs I
In September 1993, at Calvert Cliffs Nuclear Power Plant, Unit 1, a 91 Vmin (24 gpm) leak
occurred In the safety-related, closed-loop service water system. The flow path for the makeup
system from the demineralized water and condensate systems Is not seismically qualified and
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IN 98-25 July 8, 1998 the transfer pumps are not powered from a Class 1 E source. Therefore, the service water
system could have been rendered Inoperable in less than an hour in the event of a loss of
offsite power or a seismic event based on the available volume in the surge tank.
Perry 1 On July 2, 1993, during a performance test at Perry Nuclear Power Plant, Unit 1, the licensee
determined that inadequate procedural direction for setting motor-operated valve limit switches
and mechanical stops resulted In a leak rate of 946 Vmin (250 gpm) through the Isolation valve
between the non-safety-related and the safety-related portions of the emergency closed cooling
water (ECCW) system. This leakage would have exceeded the seven-day, design basis
Inventory of the ECCW surge tank. In addition, under specific conditions (i.e., loss-of-offsite
power concurrent with the single failure of the Division 2 diesel generator), both ECCW trains
could have failed.
San Onofre 2
In March 1988, at the San Onofre Nuclear Generating Station, Unit 2, the licensee determined
that the safety-related, dosed-loop CCW system may have operated outside Its design basis for
leakage before a 1984 design modification. In 1983, the licensee realized that the original basis
(CCW leakage of .537 Vmin [.142 gpm]) for having only a non-safety-related and a non- seismically qualified makeup system could not be maintained. The licensee concluded that on
the basis of the magnitude of the potential leakage, the ability to mitigate the consequences of
postulated accidents could have been impaired.
Discussion
At most boiling-water and pressurized-water reactor plants, a safety-related, closed-loop
cooling water system is provided to supply cooling water to safety-related components, including components that may carry radioactive or potentially radioactive fluids. This
closed-loop cooling water system provides a monitored, intermediate barrier between the
radioactive or potentially radioactive fluid and the environment. The closed-loop cooling water
system usually transfers Its heat to the ultimate heat sink through a safety-related open-loop
cooling water system. In most cases, the safety-related, dosed-loop cooling water systems are
required to operate during normal, shutdown, and accident conditions.
Many of these closed-loop cooling water systems also have portions that are not safety related
and not designed to seismic Category I requirements. A failure In these non-safety-related
portions of the system during normal operation or as a result of a seismic event can lead to
excessive loss of Inventory from the safety-related portion of the system. Therefore, In addition
to postulated leaks in the safety-related portions of the system, postulated leaks or breaks In
the non-safety-related portions also have the potential to result In an excessive loss of inventory
from the safety-related portions of the system.
An excessive loss of inventory from the dosed-loop system, without makeup, could prevent it
from performing its safety function and may result In the plant being outside Its design basis.
Components that could be adversely affected are plant dependent and could include the reactor
- IN
98-25
July 8, 1998
Page 3 6f 4 coolant pumps and seals, emergency core cooling system pumps, containment coolers, containment spray pumps, emergency diesel generators, safety-related room coolers, residual
heat removal heat exchangers, suppression pool coolers, and other safety-related equipment.
The events previously discussed underscore the possibility that an excessive leakage from the
safety-related, cdosed-loop cooling water system could render it Inoperable under one of the
following conditions:
1.
Non-safety-related annunciation for low Inventory failing to alert the operators.
2.
Inadequate bases for low Inventory alarm setpoint resulting In insufficient time for
operator action.
3.
Non-safety-related or non-seismically qualified makeup supply and inadequate
bases for Its startup setpoint with no procedures available for providing makeup
from a seismic category I source.
4.
Non-conservative assumptions about the leakage resulting in actual leakage that
exceeds the makeup capacity.
5.
Insufficient surge or makeup tank capacity to accommodate expected leakage
from the system for an extended period (7 days recommended by Standard
Review Plan Section 9.2.2, *Reactor Auxiliary Cooling Water Systems.")
Some of the actions taken by the above-mentioned licensees to address this issue are as
follows:
At Palisades, the licensee reported that the low-level alarm setpoint was changed. The
licensee also changed the makeup actuation setpoint to 41 percent. The licensee
revised Off-Normal Procedures to Include appropriate immediate actions. The licensee
also performed a root cause analysis to determine the cause of the leak and conducted
a programmatic review to prevent the system from leaking In the future.
At Calvert Cliffs, the licensee wrote procedures for a cross-connect path by way of
hoses from the safety-related saltwater system to the service water system for extreme
emergencies. In addition, precautionary limits have been incorporated into plant
procedures to ensure that engineering and maintenance personnel are informed before
leakage approaches the specified operability limit.
At Perry, the licensee readjusted the limit switches and mechanical stops for Isolation
valves. The licensee revised the applicable procedure to provide the requisite level of
direction for setting limittorque switches and adjusting mechanical stops.
At San Onofre, the licensee had already made a design modification In 1984 to add the
capability of supplying makeup water from a seismically qualified source.
>
B2IN 98-25
July 8, 1998 Related Generic Communications
NRC INFORMATION NOTICE 93-92: PLANT IMPROVEMENTS TO MITIGATE COMMON
DEPENDENCIES IN COMPONENT COOLING WATER SYSTEMS,' dated December 7, 1993.
This information notice requires no specific action or written response. If you have any
questions about the information In this notice, please contact one of the technical contacts listed
below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
,/5Jack W. Roe Acting Director
(7/
Division of Reactor Program Management
V/
Office of Nuclear Reactor Regulation
Technical contacts: Rick Khan, NRR
301-415-1152 e-mail: tmk@nrc.gov
William T. LeFave, NRR
301-415-3285 e-mail: wtl2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
x\\_Attachment
July 8, 1998 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
98-24
Stem Binding in Turbine
Governor Valves in Reactor
Core Isolation Cooling (RCIC)
and Auxiliary Feedwater (AFW)
Systems
7/08/98
All holders of operating licenses
for nuclear power reactors except
those who have permanently
ceased operation and have
certified that fuel has been
permanently removed from the
reactor vessel
98-23
98-22
Crosby Relief Valve Setpoint
Drift Problems Caused by
Corrosion of the Guide Ring
Deficiencies Identified
During NRC Design
Inspections
Potential Deficiency of
Electrical Cable/Connection
Systems
6/26/98
6/23/98
6/4/98
All holders of operating licenses
for pressurized water reactors
(PWRs), except those licensees
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel
All holders of operating licenses
for nuclear power reactors, except
those licensees who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the vessel
All holders of operating licenses
for nuclear power reactors, except
those licensees who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel.
98-21 OL = Operating License
CP = Construction Permit
June 8, 1998 Related Generic Communications
NRC INFORMATION NOTICE 93-92: PLANT IMPROVEMENTS TO MITIGATE COMMON
DEPENDENCIES IN COMPONENT COOLING WATER SYSTEMS," dated December 7, 1993.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts listed
below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
[Original signed by]
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Rick Khan, NRR
301-415-1152 e-mail: tmk@nrc.gov
William T. LeFave, NRR
301-415-3285 e-mail: wtl2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices ,47
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DATE
06/18/98
06/18/98
06/22/98
06/25/98
06/30/98
[OFFICIAL RECORD COPY]
IN 9 x
June xx, 1998 Related Generic Communications
NRC INFORMATION NOTICE 93-92: 'PLANT IMPROVEMENTS TO MITIGATE COMMON
DEPENDENCIES IN COMPONENT COOLING WATER SYSTEMS," dated December 7,1993.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts listed
below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Rick Khan, NRR
301-415-1152 e-mail: tmk@nrc.gov
William T. LeFave, NRR
301-415-3285 e-mail: wtl2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
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June xx, 1998
Page$ of J5
Related Generic Communications
NRC INFORMATION NOTICE 93-92: "PLANT IMPROVEMENTS TO MITIGATE COMMON
DEPENDENCIES IN COMPONENT COOLING WATER SYSTEMS," dated December 7, 1993.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts listed
below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Rick Khan, NRR
301-415-1152 e-mail: tmk@nrc.gov
William T. LeFave, NRR
301-415-3285 e-mail: wt2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: g:/tmk:in9805tx.tkl
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/ /98
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62-56
IN 98-xx
June xx, 1998 Related Generic Communications
1.
NRC INFORMATION NOTICE 93-92: "PLANT IMPROVEMENTS TO MITIGATE
COMMON DEPENDENCIES IN COMPONENT COOLING WATER SYSTEMS," dated
December 7, 1993.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts listed
below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W: Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Rick Khan, NRR
301-415-1152 e-mail: tmk@nrc.gov
William T. LeFave, NRR
301-415-3285 e-mail: wtl2@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: g:/tmk:/in9805tx.tkl
To receive a copy of this document, Indicate in the box C=Copy wlo attachmentlenclosure E=Copy with attachment/enclosure N = No copy
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DATE
_____98
44/_98
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/98 I /98
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