Information Notice 1989-71, Diversion of the Residual Heat Removal Pump Seal Cooling Water Flow During Recirculation Operation Following a Loss-Of-Coolant Accident
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
October 19, 1989
NRC INFORMATION NOTICE NO. 89-71:
DIVERSION OF THE RESIDUAL HEAT REMOVAL
PUMP SEAL COOLING WATER FLOW DURING
RECIRCULATION OPERATION FOLLOWING A
LOSS-OF-COOLANT ACCIDENT
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
This information notice is intended to alert addressees to a potential problem
resulting from a design deficiency that may affect the operability of the
residual heat removal (RHR) pumps during recirculation operation following
a loss-of-coolant accident (LOCA). The problem, which can occur as a result
of a single failure can cause a diversion of the cooling water flow from the
RHR pump seal coolers, resulting in inadequate seal cooling and the potential
for ultimate failure of the RHR pumps.
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
During a probabilistic risk assessment (PRA) study of the emergency core
cooling system at Haddam Neck, the licensee discovered that a single failure
in response to a LOCA could disable both RHR pumps. The single failure would
cause the diversion of the cooling water flow from the RHR pump seal coolers
resulting in inadequate seal cooling and possible pump failure.
As indicated in Attachment 1, cooling water for the RHR pump seal coolers comes
from the cooling water Inlet lines to each RHR heat exchanger.
During normal
operation, the component cooling water system provides cooling to the RHR heat
exchangers and pump seal coolers.
However, during a LOCA condition, component
cooling water is isolated, and service water is used to provide cooling to the
RHR components. Because the RHR pump seal cooler water supply line is cross- connected to both the component cooling and service water systems, a failure
of one of the service water motor-operated valves to open following a LOCA
would result in only one branch of service water being available to provide
cooling to both RHR heat exchangers and the seal water coolers.
891013001,
-
low
IN 89-71 October 19, 1989 Under these conditions, the RHR seal water coolers would receive inadequate
flow, with the potential for ultimately causing the failure of both RHR pumps.
The licensee corrected this problem by installing check valves in the seal
water cooling piping (shown in Attachment 2) to preclude one branch of service
water from feeding two RHR heat exchangers.
Discussion of Safety Significance:
The design deficiency described above was identified in a plant that switches
cooling water systems during a LOCA.
However, the problem could occur in any
auxiliary cooling water system that provides sizably different cooling needs
for different redundant components such as RHR heat exchangers and seal coolers.
The important feature in the system is the interconnecting piping between the
auxiliary cooling water system branches and the piping to the individual components.
In the situation described in this notice, a single failure of a valve to open
would cause one branch of auxiliary cooling water to service multiple redundant
components, thereby reducing flow below design requirements. Licensees may wish
to review their auxiliary cooling water system designs for similar deficiencies.
Several other flow design problems that affect operation while in the recircu- lation mode following a LOCA have been previously identified in IN 87-63,
"Inadequate Net Positive Suction Head in Low Pressure Safety Systems," and
IN 88-74, "Potentially Inadequate Performance-of ECCS in PWRs During Recircu- lation Operation Following a LOCA." It is important to note that a flow balance
analysis would determine the impact of asymmetric flow balances caused by single
failures in these systems. A simple review of piping diagrams may be sufficient
to identify systems with potential flow problems, but hydraulic analyses are
necessary to confirm suspected problems.
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 NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: S. Israel, AEOD
(301) 492-4437
0. Prochnow, NRR
(301) 492-1166 Attachments:
1. Diagram of Haddam Neck's Original RHR Cooling Water System
2. Diagram of Haddam Neck's Modified RHR Cooling Water System
3. List of Recently Issued NRC Information Notices
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Attachment 2
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Attachment 3
October 19, 1989 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
89-70
89-69
89-68
89-67
89-66 Possible Indications of
10/11/89
Misrepresented Vendor
Products
Loss of Thermal Margin
9/29/89
Caused by Channel Box
Bow
Evaluation of Instrument
9/25/89
Setpoints During
Modifications
Loss of Residual Heat
9/13/89
Removal Caused by
Injection
Qualification Life of
9/11/89
Solenoid Valves
Licensee Report of
9/11/89
Defective Refurbished
Circuit Breakers
Potential for Stress
9/8/89
Corrosion Cracking in
Steam Generator Tube
Plugs Supplied by
Babcock and Wilcox
Electrical Bus Bar Failures
9/7/89 Possible Submergence of
9/5/89
Electrical Circuits Located
Above the Flood Level Because
of Water Intrusion and Lack
of Drainage
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for BWRS.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
88-46, Supp. 4
89-65
89-64
89-63 OL = Operating License
CP - Construction Permit
IN 89-71 October 19, 1989 Under these conditions, the RHR seal water coolers would receive inadequate
flow, with the potential for ultimately causing the failure of both RHR pumps.
The licensee corrected this problem by installing check valves in the seal
water cooling piping (shown in Attachment 2) to preclude one branch of service
water from feeding two RHR heat exchangers.
Discussion of Safety Significance:
The design deficiency described above was identified in a plant that switches
cooling water systems during a LOCA. However, the problem could occur in any
auxiliary cooling water system that provides sizably different cooling needs
for different redundant components such as RHR heat exchangers and seal coolers.
The important feature in the system is the interconnecting piping between the
auxiliary cooling water system branches and the piping to the individual components.
In the situation described in this notice, a single failure of a valve to open
would cause one branch of auxiliary cooling water to service multiple redundant
components, thereby reducing flow below design requirements.
Licensees may wish
to review their auxiliary cooling water system designs for similar deficiencies.
Several other flow design problems that affect operation while in the recircu- lation mode following a LOCA have been previously identified in IN 87-63,
"Inadequate Net Positive Suction Head in Low Pressure Safety Systems," and
IN 88-74, "Potentially Inadequate Performance of ECCS in PWRs During Recircu- lation Operation Following a LOCA."
It is important to note that a flow balance
analysis would determine the impact of asymmetric flow balances caused by single
failures in these systems. A simple review of piping diagrams may be sufficient
to identify systems with potential flow problems, but hydraulic analyses are
necessary to confirm suspected problems.
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 NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: S. Israel, AEOD
(301) 492-4437
D. Prochnow, NRR
(301) 492-1166 Attachments:
1. Diagram of Haddam Neck's Original RHR Cooling Water System
2. Diagram of Haddam Neck's Modified RHR Cooling Water System
3. List of Recently Issued NRC Information Notices
Document Name: DIVERSION OF SEAL FLOW
- SEE PREVIOUS CONCURRENCES
-
- C/OGCB:DOEA:NRR
E DCHBerlinger
10/
89
10/11/89
- OGCB:DOEA:NRR*ROAB:DSP:AEOD *C/SRXB:DEST:NRR
- D/ S :NRR
RPB:ARM
DProchnow
MWHodges
AThadani
TechEd
10/02/89
10/02/89
10/05/89
10/05/89
10/ /89
IN 89-XX
-
\\_J\\
October xx, 1989 Under these conditions, the RHR seal water coolers would receive inadequate
flow, ultimately causing the failure of both RHR pumps. The licensee corrected
this problem by installing check valves in the seal water cooling piping (shown
in Attachment 2) to preclude one branch of service water from feeding two RHR
heat exchangers.
Discussion of Safety Significance:
The design deficiency described above was identified in a plant that switches
cooling water systems during a LOCA. However, the problem could occur in any
auxiliary cooling water system that provides sizably different cooling needs
for different redundant components such as RHR heat exchangers and seal cool- ers. The important feature in the system is the interconnecting piping between
the auxiliary cooling water system branches and the piping to the individual
components.
In the event described in this notice, a single failure of a valve to open
caused one branch of auxiliary cooling water to service multiple redundant
components, thereby reducing flow below design requirements. Licensees may
wish to review their auxiliary cooling water system designs for similar defi- ciencies.
Several other flow design problems that affect recirculation opera- tion following a LOCA have been previously identified in IN 87-63 and IN 88-74.
It is important to note that a flow balance analysis must be performed to
determine the impact of asymmetric flow balances caused by single failures in
these systems.
It is also important to note that a simple review of piping
diagrams may be sufficient to Identify systems with potential flow problems, but hydraulic analyses are necessary to confirm suspected problems.
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 NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: S. Israel, AEOD
(301) 492-4437
D. Prochnow, NRR
(301) 492-1166 Attachments:
1. Diagram of Haddam Neck's Original RHR Cooling Water System
2. Diagram of Haddam Neck's Modified RHR Cooling Water System
3. List of Recently Issued NRC Information Notices
Document Name: DIVERSION OF SEAL FLOW
X 4
- SEE PREVIOUS CONCURRENCES
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D/DOEA:NRR
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10/ /89
10/i//89
- OGCB:DOEA:NRR*ROAB:DSP:AEOD *C/SRXB:DEST:NRR
- D/DST:NRR
RPB:ARM
DProchnow
MWHod es
AThadani
TechEd
10/02/89
10/02/89
10/05/89
10/05/89
10/3/89
IN 89-XX
October xx, 1989 The licensee corrected this problem by installing check valves in the seal
water cooling piping (shown in Attachment 2) to preclude one branch of service
water from feeding two RHR heat exchangers.
Discussion of Safety Significance:
The design deficiency described above
cooling water systems during a LOCA.
auxiliary cooling water system that pi
for different redundant components suw
ers. The important feature in the sy!
the auxiliary cooling water system bra
components.
was identified in a plant that switches
However, the problem could occur in any
rovides sizably different cooling needs
- h as RHR heat exchangers and seal cool- stem is the interconnecting piping between
inches and the piping to the individual
In the event described in this notice, a single failure of a valve to open
caused one branch of auxiliary cooling water to service multiple redundant
components, thereby reducing flow below design requirements. Licensees may
wish to review their auxiliary cooling water system designs for similar defi- ciencies.
Several other flow design problems that affect recirculation opera- tion following a LOCA have been previously identified in IN 87-63 and IN 88-74.
It is important to note that a flow balance analysis must be performed to
determine the impact of asymmetric flow balances caused by single failures in
these systems.
It is also important to note that a simple review of piping
diagrams may be sufficient to identify systems with potential flow problems, but hydraulic analyses are necessary to confirm suspected problems.
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 NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
S. Israel, AEOD
(301) 492-4437
D. Prochnow, NRR
(301) 492-1166 Attachments:
1. Diagram of Haddam Neck's Original RHR Cooling Water System
2. Diagram of Haddam Neck's Modified RHR Cooling Water System
3. List of Recently Issued NRC Information Notices
Document Name:
DIVERSION OF SEAL FLOW
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DProchnow
10/ Z/89 ROAB:DSPSAEOD
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10/ W89 D/DOEA:NRR
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10/
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