Information Notice 2008-11, Service Water System Degradation at Brunswicksteam Electric Plant Unit 1: Difference between revisions
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| issue date = 06/18/2008 | | issue date = 06/18/2008 | ||
| title = Service Water System Degradation at Brunswicksteam Electric Plant Unit 1 | | title = Service Water System Degradation at Brunswicksteam Electric Plant Unit 1 | ||
| author name = Case J | | author name = Case J | ||
| author affiliation = NRC/NRR/ADRA/DPR | | author affiliation = NRC/NRR/ADRA/DPR | ||
| addressee name = | | addressee name = | ||
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| page count = 5 | | page count = 5 | ||
}} | }} | ||
{{#Wiki_filter: | {{#Wiki_filter:UNITED STATES | ||
NUCLEAR REGULATORY COMMISSION | |||
OFFICE OF NUCLEAR REACTOR REGULATION | |||
WASHINGTON, DC 20555-0001 June 18, 2008 NRC INFORMATION NOTICE 2008-11: SERVICE WATER SYSTEM DEGRADATION AT | |||
BRUNSWICK STEAM ELECTRIC PLANT UNIT 1 | |||
==ADDRESSEES== | ==ADDRESSEES== | ||
All holders of operating licenses for nuclear power reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor | All holders of operating licenses for nuclear power reactors, except those who have | ||
permanently ceased operations and have certified that fuel has been permanently removed | |||
from the reactor vessel. | |||
==PURPOSE== | ==PURPOSE== | ||
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform addressees of recent service water problems experienced at the Brunswick Steam Electric Plant (Brunswick) Unit It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar | The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform | ||
addressees of recent service water problems experienced at the Brunswick Steam Electric Plant | |||
(Brunswick) Unit 1. 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 IN are not NRC requirements; therefore, no specific action or | |||
written response is required. | |||
==DESCRIPTION OF CIRCUMSTANCES== | ==DESCRIPTION OF CIRCUMSTANCES== | ||
The licensee at Brunswick Unit 1 recently encountered problems with the service water system, including failure of one of the supply valves to the residual heat removal (RHR) service water system, an RHR service water pump that was rendered inoperable by foreign material, and flow degradation to a safety-related room | The licensee at Brunswick Unit 1 recently encountered problems with the service water system, including failure of one of the supply valves to the residual heat removal (RHR) service water | ||
system, an RHR service water pump that was rendered inoperable by foreign material, and flow | |||
degradation to a safety-related room cooler. | |||
===RHR Service Water Supply Valve Failure=== | |||
On July 26, 2007, the 1B loop RHR service water supply motor-operated butterfly valve failed to | |||
open while operators were attempting to place the B loop RHR service water pumps in service. | |||
This caused the 1B and 1D RHR service water pumps to trip on low suction pressure. The | |||
failure of this 24-inch Fisher Series 7600 butterfly valve was due to the loss of two taper pins | |||
used to connect the valve stem to the valve disc. Taper pins are impact-driven into holes in the | |||
valve stem and disc and are intended to hold them together through an interference fit. The | |||
licensee determined that the most likely cause of the failure was that the taper pins had not | |||
been completely driven into the holes during valve refurbishment, which allowed the pins to | |||
become displaced during operation. | |||
The licensee had previously reviewed operating experience, including NRC IN 2005-23, Vibration-Induced Degradation of Butterfly Valves, dated August 1, 2005, which showed that | |||
vibration could cause these pins to come loose over time, and had determined that no action | |||
was necessary based on different operating conditions, periodic valve inspections, and valve | |||
assembly conducted in accordance with vendor recommendations. In light of the July 26, 2007, valve failure, licensee corrective actions included welding or staking any service water valve | |||
taper pin that was vulnerable to loss (i.e., becoming dislodged and carried downstream). In | |||
addition, the licensee revised their valve maintenance procedures to specify staking or welding | |||
taper pins on these valves during refurbishment. | |||
===RHR Service Water Pump Failure=== | |||
Following identification of the two missing taper pins from the loop B RHR service water supply | |||
valve, the licensee attempted to find and retrieve both pins, but could only locate one. The | |||
licensees operability evaluation concluded the system was operable based on their | |||
determination that the pin had passed through the RHR service water pumps to the 1B RHR | |||
heat exchanger, where it would remain in the heat exchangers service water inlet endbell. The | |||
licensee based this conclusion, in part, on bench testing they conducted which consisted of | |||
dropping a spare taper pin through a stationary pump impeller. | |||
On August 21, 2007, the 1D RHR service water pump seized during a start attempt. The | |||
licensees investigation identified that the pump failure was the result of the missing taper pin | |||
from the loop B RHR service water supply motor-operated valve becoming lodged between the | |||
pump casing and impeller. During their evaluation of the missing taper pin, the licensee had not | |||
contacted the vendor to assist in determining whether the taper pin would pass through an | |||
operating pump. During subsequent discussions, the vendor indicated that based on the | |||
pumps internal clearances, they could not predict if a taper pin would pass through. Licensee | |||
corrective actions included replacing the rotating element for the 1D RHR service water pump. | |||
===Service Water Flow Decrease to RHR Room Cooler=== | |||
On August 2, 2007, operators identified that service water cooling flow through the 1B RHR | |||
room cooler had decreased from a normal value of 380 gallons per minute (1438 liters per | |||
minute) to 250 gallons per minute (946 liters per minute). Flow continued to decrease, and the | |||
cooler and the B RHR loop were declared inoperable on August 16, 2007. The licensee opened | |||
the cooler for inspection and found foreign material in the cooler inlet piping consisting of rubber | |||
lining material from a Fisher Model 9100 butterfly valve. Because there was only one valve of | |||
this type upstream of the affected cooler, the licensee concluded that all the material came from | |||
this valve and had been removed during cooler cleaning. The valve was tagged closed to | |||
prevent the release of additional material and an operability evaluation was completed. The | |||
licensees operability evaluation concluded that the service water system was operable but | |||
degraded, and that normal system monitoring would be effective at discovering any | |||
unrecovered foreign material. | |||
At Brunswick, there have been a number of failures of Fisher Model 9100 butterfly valve rubber | |||
liners dating back to 1985 and most recently at Unit 1 in 2004. The valve believed to be the | |||
source of the material had not been internally inspected, and the NRC inspectors questioned | |||
the licensees operability conclusion, given the possibility that the foreign material could have | |||
come from historical valve lining failures and that additional foreign material from these previous | |||
failures could remain in the system. On September 9, 2007, the licensee decided to shut down Unit 1 to inspect portions of the service water system. This decision was based on the failure of | |||
the 1D RHR service water pump and inoperability of the 1B RHR room cooler. The licensee | |||
inspected the valve believed to be the source of the foreign material and found that its rubber | |||
lining was intact. Additional foreign material, in the form of rubber valve lining, oyster shells, and two pieces of service water strainer tie rod with retaining nuts, was identified during these | |||
inspections. The licensee removed the foreign material and completed a subsequent operability | |||
determination to demonstrate that the service water system was operable prior to plant restart. | |||
An NRC special inspection team reviewed the circumstances surrounding these issues. The | |||
team identified that the service water system problems experienced at Brunswick occurred | |||
because the licensee did not take adequate corrective actions to remove foreign material from | |||
the system and did not perform an adequate loose parts analysis and operability evaluation | |||
once foreign material was identified. Additional information is available in NRC Special | |||
Inspection Report 05000324/2007-011 and 05000325/2007-011, dated November 16, 2007, and can be found on the NRCs public website in the Agencywide Documents Access and | |||
Management System (ADAMS), under Accession No. ML073200779. | |||
==BACKGROUND== | ==BACKGROUND== | ||
Related NRC Generic Communications NRC IN 2005-23, | |||
===Related NRC Generic Communications=== | |||
NRC IN 2005-23, Vibration-Induced Degradation of Butterfly Valves, dated August 1, 2005 (ADAMS Accession No. ML051740299). This IN was written to alert addressees to failure of | |||
Fisher butterfly valves in the component cooling water system at San Onofre Nuclear | |||
Generating Station. Two of the taper pins used to hold the stem to the disc came loose, preventing valve operation. Similar failures had been reported at Davis-Besse Nuclear Power | |||
Station and Turkey Point Nuclear Power Plant with valves manufactured by Flowserve and | |||
Henry Pratt Company, respectively. | |||
==DISCUSSION== | ==DISCUSSION== | ||
Licensees are required to have an operable service water system as specified in plant technical | Licensees are required to have an operable service water system as specified in plant technical | ||
specifications. The Brunswick Unit 1 service water problems were the result of the loss of two | |||
taper pins from a Fisher service water system butterfly valve, historical degradation of Fisher | |||
butterfly valve lining material, and failure to adequately assess the impact of foreign material in | |||
the system. | |||
==CONTACT== | ==CONTACT== | ||
This information notice requires no specific action or written | This information notice requires no specific action or written response. Please direct any | ||
questions about this matter to the technical contacts listed below or the appropriate Office of | |||
Nuclear Reactor Regulation project manager. | |||
/RA by MMaxin for/ | |||
Michael J. Case, Director | |||
Division of Policy and Rulemaking | |||
Office of Nuclear Reactor Regulation | |||
Technical Contacts: Gerald Wilson, RII Gregory Bowman, NRR/DIRS | |||
404-562-4613 301-415-2939 E-mail: gerald.wilson@nrc.gov E-mail: gregory.bowman@nrc.gov | |||
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, by going to the Electronic Reading Room and then to Document Collections. | |||
==CONTACT== | ==CONTACT== | ||
This information notice requires no specific action or written | This information notice requires no specific action or written response. Please direct any | ||
questions about this matter to the technical contacts listed below or the appropriate Office of | |||
Nuclear Reactor Regulation project manager. | |||
/RA by MMaxin for/ | |||
Michael J. Case, Director | |||
Division of Policy and Rulemaking | |||
Office of Nuclear Reactor Regulation | |||
Technical Contacts: Gerald Wilson, RII Gregory Bowman, NRR/DIRS | |||
404-562-4613 301-415-2939 E-mail: gerald.wilson@nrc.gov E-mail: gregory.bowman@nrc.gov | |||
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, by going to the Electronic Reading Room and then to Document Collections. | |||
Distribution: | |||
IN r/f | |||
*Concurred via email | |||
**See previous concurrence | |||
ADAMS Accession Number: ML081120649 OFFICE DIRS/IOEB** TECH EDITOR* BC/DIRS/IOEB** D/NRR/DIRS | |||
NAME GBowman CHsu MRoss-Lee FBrown | |||
DATE 05/14/08 04/18/08 05/15/08 06/11/08 OFFICE DPR/PGCB DPR/PGCB BC/DPR/PGCB D/NRR/DPR | |||
NAME DBeaulieu CHawes MMurphy MCase | |||
DATE 06/5/08 06/18/08 06/18/08 06/18/08 OFFICIAL RECORD COPY}} | |||
{{Information notice-Nav}} | {{Information notice-Nav}} |
Latest revision as of 18:36, 14 November 2019
ML081120649 | |
Person / Time | |
---|---|
Site: | Brunswick ![]() |
Issue date: | 06/18/2008 |
From: | Case J NRC/NRR/ADRA/DPR |
To: | |
Bowman G, DiRS/IOEB, 415-2939 | |
References | |
IN-08-011 | |
Download: ML081120649 (5) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, DC 20555-0001 June 18, 2008 NRC INFORMATION NOTICE 2008-11: SERVICE WATER SYSTEM DEGRADATION AT
BRUNSWICK STEAM ELECTRIC PLANT UNIT 1
ADDRESSEES
All holders of operating licenses for nuclear power reactors, except those 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 (IN) to inform
addressees of recent service water problems experienced at the Brunswick Steam Electric Plant
(Brunswick) Unit 1. 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 IN are not NRC requirements; therefore, no specific action or
written response is required.
DESCRIPTION OF CIRCUMSTANCES
The licensee at Brunswick Unit 1 recently encountered problems with the service water system, including failure of one of the supply valves to the residual heat removal (RHR) service water
system, an RHR service water pump that was rendered inoperable by foreign material, and flow
degradation to a safety-related room cooler.
RHR Service Water Supply Valve Failure
On July 26, 2007, the 1B loop RHR service water supply motor-operated butterfly valve failed to
open while operators were attempting to place the B loop RHR service water pumps in service.
This caused the 1B and 1D RHR service water pumps to trip on low suction pressure. The
failure of this 24-inch Fisher Series 7600 butterfly valve was due to the loss of two taper pins
used to connect the valve stem to the valve disc. Taper pins are impact-driven into holes in the
valve stem and disc and are intended to hold them together through an interference fit. The
licensee determined that the most likely cause of the failure was that the taper pins had not
been completely driven into the holes during valve refurbishment, which allowed the pins to
become displaced during operation.
The licensee had previously reviewed operating experience, including NRC IN 2005-23, Vibration-Induced Degradation of Butterfly Valves, dated August 1, 2005, which showed that
vibration could cause these pins to come loose over time, and had determined that no action
was necessary based on different operating conditions, periodic valve inspections, and valve
assembly conducted in accordance with vendor recommendations. In light of the July 26, 2007, valve failure, licensee corrective actions included welding or staking any service water valve
taper pin that was vulnerable to loss (i.e., becoming dislodged and carried downstream). In
addition, the licensee revised their valve maintenance procedures to specify staking or welding
taper pins on these valves during refurbishment.
RHR Service Water Pump Failure
Following identification of the two missing taper pins from the loop B RHR service water supply
valve, the licensee attempted to find and retrieve both pins, but could only locate one. The
licensees operability evaluation concluded the system was operable based on their
determination that the pin had passed through the RHR service water pumps to the 1B RHR
heat exchanger, where it would remain in the heat exchangers service water inlet endbell. The
licensee based this conclusion, in part, on bench testing they conducted which consisted of
dropping a spare taper pin through a stationary pump impeller.
On August 21, 2007, the 1D RHR service water pump seized during a start attempt. The
licensees investigation identified that the pump failure was the result of the missing taper pin
from the loop B RHR service water supply motor-operated valve becoming lodged between the
pump casing and impeller. During their evaluation of the missing taper pin, the licensee had not
contacted the vendor to assist in determining whether the taper pin would pass through an
operating pump. During subsequent discussions, the vendor indicated that based on the
pumps internal clearances, they could not predict if a taper pin would pass through. Licensee
corrective actions included replacing the rotating element for the 1D RHR service water pump.
Service Water Flow Decrease to RHR Room Cooler
On August 2, 2007, operators identified that service water cooling flow through the 1B RHR
room cooler had decreased from a normal value of 380 gallons per minute (1438 liters per
minute) to 250 gallons per minute (946 liters per minute). Flow continued to decrease, and the
cooler and the B RHR loop were declared inoperable on August 16, 2007. The licensee opened
the cooler for inspection and found foreign material in the cooler inlet piping consisting of rubber
lining material from a Fisher Model 9100 butterfly valve. Because there was only one valve of
this type upstream of the affected cooler, the licensee concluded that all the material came from
this valve and had been removed during cooler cleaning. The valve was tagged closed to
prevent the release of additional material and an operability evaluation was completed. The
licensees operability evaluation concluded that the service water system was operable but
degraded, and that normal system monitoring would be effective at discovering any
unrecovered foreign material.
At Brunswick, there have been a number of failures of Fisher Model 9100 butterfly valve rubber
liners dating back to 1985 and most recently at Unit 1 in 2004. The valve believed to be the
source of the material had not been internally inspected, and the NRC inspectors questioned
the licensees operability conclusion, given the possibility that the foreign material could have
come from historical valve lining failures and that additional foreign material from these previous
failures could remain in the system. On September 9, 2007, the licensee decided to shut down Unit 1 to inspect portions of the service water system. This decision was based on the failure of
the 1D RHR service water pump and inoperability of the 1B RHR room cooler. The licensee
inspected the valve believed to be the source of the foreign material and found that its rubber
lining was intact. Additional foreign material, in the form of rubber valve lining, oyster shells, and two pieces of service water strainer tie rod with retaining nuts, was identified during these
inspections. The licensee removed the foreign material and completed a subsequent operability
determination to demonstrate that the service water system was operable prior to plant restart.
An NRC special inspection team reviewed the circumstances surrounding these issues. The
team identified that the service water system problems experienced at Brunswick occurred
because the licensee did not take adequate corrective actions to remove foreign material from
the system and did not perform an adequate loose parts analysis and operability evaluation
once foreign material was identified. Additional information is available in NRC Special
Inspection Report 05000324/2007-011 and 05000325/2007-011, dated November 16, 2007, and can be found on the NRCs public website in the Agencywide Documents Access and
Management System (ADAMS), under Accession No. ML073200779.
BACKGROUND
Related NRC Generic Communications
NRC IN 2005-23, Vibration-Induced Degradation of Butterfly Valves, dated August 1, 2005 (ADAMS Accession No. ML051740299). This IN was written to alert addressees to failure of
Fisher butterfly valves in the component cooling water system at San Onofre Nuclear
Generating Station. Two of the taper pins used to hold the stem to the disc came loose, preventing valve operation. Similar failures had been reported at Davis-Besse Nuclear Power
Station and Turkey Point Nuclear Power Plant with valves manufactured by Flowserve and
Henry Pratt Company, respectively.
DISCUSSION
Licensees are required to have an operable service water system as specified in plant technical
specifications. The Brunswick Unit 1 service water problems were the result of the loss of two
taper pins from a Fisher service water system butterfly valve, historical degradation of Fisher
butterfly valve lining material, and failure to adequately assess the impact of foreign material in
the system.
CONTACT
This information notice requires no specific action or written response. Please direct any
questions about this matter to the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation project manager.
/RA by MMaxin for/
Michael J. Case, Director
Division of Policy and Rulemaking
Office of Nuclear Reactor Regulation
Technical Contacts: Gerald Wilson, RII Gregory Bowman, NRR/DIRS
404-562-4613 301-415-2939 E-mail: gerald.wilson@nrc.gov E-mail: gregory.bowman@nrc.gov
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, by going to the Electronic Reading Room and then to Document Collections.
CONTACT
This information notice requires no specific action or written response. Please direct any
questions about this matter to the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation project manager.
/RA by MMaxin for/
Michael J. Case, Director
Division of Policy and Rulemaking
Office of Nuclear Reactor Regulation
Technical Contacts: Gerald Wilson, RII Gregory Bowman, NRR/DIRS
404-562-4613 301-415-2939 E-mail: gerald.wilson@nrc.gov E-mail: gregory.bowman@nrc.gov
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, by going to the Electronic Reading Room and then to Document Collections.
Distribution:
IN r/f
- Concurred via email
- See previous concurrence
ADAMS Accession Number: ML081120649 OFFICE DIRS/IOEB** TECH EDITOR* BC/DIRS/IOEB** D/NRR/DIRS
NAME GBowman CHsu MRoss-Lee FBrown
DATE 05/14/08 04/18/08 05/15/08 06/11/08 OFFICE DPR/PGCB DPR/PGCB BC/DPR/PGCB D/NRR/DPR
NAME DBeaulieu CHawes MMurphy MCase
DATE 06/5/08 06/18/08 06/18/08 06/18/08 OFFICIAL RECORD COPY