Information Notice 1998-31, Fire Protection System Design Deficiencies and Common-Mode Flooding of Emergency Core Cooling System Rooms at Washington Nuclear Project Unit 2
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
August 18, 1998
FIRE PROTECTION SYSTEM DESIGN DEFICIENCIES
AND COMMON-MODE FLOODING OF EMERGENCY
CORE COOLING SYSTEM ROOMS AT
WASHINGTON NUCLEAR PROJECT UNIT 2
Addressees
All holders of operating licenses for nuclear power reactors, except those licensees that 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 a rupture of a fire water system valve, due to a water hammer, In a fire main
vertical riser at Washington Nuclear Project Unit 2 (WNP-2) that flooded two emergency core
cooling system (ECCS) equipment rooms. 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
On June 17, 1998, WNP-2 was in Mode 4 (cold shutdown) and preparations were underway for
a plant startup. At approximately 1:45 p.m., multiple fire alarms were received In the control
room coincident with three main fire pumps automatically starting and several loud water
hammer noises being heard throughout the plant. The water hammer caused a fire protection
isolation valve (FP-V-29D) to rupture In the fire protection system riser In the northeast stairwell
of the reactor building. Water from the stairwell entered residual heat removal (RHR) pump
room C through a watertight door that had not been adequately secured and began rapidly
flooding the room. A reactor drains system valve (FDR-V-609) located In a line connecting the
sumps of the RHR C and low-pressure core spray (LPCS) pump rooms failed to dose as
designed and allowed water to flow Into the LPCS pump room. The flood water completely
submerged the RHR C pump and motor and the Division 11 keepfill pump, which serves RHR B
and C and is also located In the room. Water in the LPCS pump room rose to a level just below
the pump motor and also completely submerged the minimum flow valve and the Division I
keepfill pump, which serves both the LPCS and RHR A trains.
808 12E0 98-052 180012 gal~~
L1 a
' JIN 98-31 August 18, 1998 To isolate the flooding, plant operators secured the fire pumps, which Impaired the normal fire
suppression capability of the station. On the basis of these events, the plant operators
declared a notification of unusual event (NOUE) and activated the plant emergency response
organization. As a compensatory measure for the loss of the normal fire suppression capability, the nearby Hanford fire department dispatched emergency equipment to the site.
Subsequently, the plant staff placed the fire suppression system In an alternate configuration, which was less susceptible to water hammer and terminated the unusual event.
Iti scu s sio n
I.
Fire Protection System Design and Operation
The fire protection system at WNP-2 consists of two diesel-driven and two electric- driven fire pumps. The two electric pumps and one of the diesel pumps have a capacity
of 2000 GPM each and draw a supply from the circulating water basin. The remaining
diesel-driven pump has a capacity of 2500 GPM and Is supplied by a 400,000-gallon
embankment-supported Fabritank (i.e., bladder). The fire pumps are normally in
standby and the system pressure Is maintained at approximately 150 psig by a
220-GPM jockey pump. The system Is arranged such that the pumps supply a main
header, which, In tum, supplies various yard hydrant Isolation valves and building
standpipes. The risers in the reactor building are the high points of the fire main system
at WNP-2 and rise approximately 180 feet above the main yard loop.
Additionally, the design also includes a number of PRE-ACTION systems, which are not
normally filled with water. Upon actuation of the associated detector(s) for a given PRE-
ACTION system, the PRE-ACTION system valves will open and allow water to flow from
the main header Into the associated piping. Some of the plant PRE-ACTION systems
are activated by Ionization-type detectors, whereas other PRE-ACTION systems rely on
thermal detectors for actuation. However, the sprinkler heads associated with the
downstream piping are not actuated during a PRE-ACTION unless the thermal-fusible
links are melted on the individual heads, thereby completing the flow path for the fire
water.
This event was Initiated by the actuation of fire detectors during cutting and grinding
activities, which were taking place In the diesel generator building. The fire detectors, sensing the smoke from the maintenance activities, activated a fire protection PRE-
ACTION station, which caused the associated PRE-ACTION valves to open and fill the
normally dry sprinkler line header. (A second PRE-ACTION station also actuated due to
sympathetic effects.) However, no actuation of the associated sprinklers occurred since
they are ultimately Initiated by thermal-fusible links. The depressurization of the fire
water system during the filling of the PRE-ACTION lines caused significant voiding In the
upper portions of the reactor building vertical fire main risers and generated an auto- start signal for all four main fire water pumps to start on low system pressure. Three of
the pumps started Immediately, and the fourth pump began a 30-second time delay
sequence for starting. The concurrent operation of the three pumps resulted In a rapid
reflood of the reactor building risers and collapsed the void that had been created in the
northeast stairwell riser. This sequence of events caused a significant water hammer
~'JIN 98-31 August 18, 1998 that ruptured a 12-inch, cast-iron, fire protection system Isolation valve that was located
in the stairwell riser. The licensee determined that the design of the fire protection
system was Inadequate in that the system Is configured such that destructive water
hammer forces are generated during anticipated transients when the system is in a
normal lineup. Specifically, the significant voiding caused by the PRE-ACTION
actuation, coupled with the simultaneous starting of the main fire pumps and the
unfavorable geometry of the reactor building riser and its associated supports, contributed to the severity of this event.
Common-Mode Flooding Considerations
During the event, approximately 163,000 gallons of water were Introduced into the
northeast stairwell, RHR C, and the LPCS pump rooms. Additionally, some minor
leakage of flood water occurred between the LPCS pump room and the vestibule
separating that room from the adjacent high pressure core spray pump room. Water
also leaked from the RHR C pump room Into the adjacent reactor core Isolation cooling
room through a double watertight door arrangement that separates those two rooms.
With respect to the flooding of the ECCS rooms, It was determined that the door to the
RHR C pump room was left In an unsecured condition sometime before the event. A
review of a door alarm printout from the common alarm station indicated that the door
had changed state several minutes before the fire protection system rupture. With the
door In an unsecured or open condition, an unrestricted pathway existed for flood water
to flow from the stairwell Into the RHR C pump room. However, It was noted that the
watertight doors for the northeast stairwell access to the RHR C pump room and the
LPCS pump room were not designed or Installed to prevent flooding from the stairwell
from entering the associated pump rooms (the doors were designed to seal from Inside
the rooms). Thus, even If the door had been secured, water would have entered the
pump rooms, albeit at a much slower rate. The licensee's flooding analyses had
assumed that a stairwell flood would eventually render the LPCS and RHR C systems
Inoperable and that operator actions to start the RHR A and B trains would be taken
before the loss of the keepfill pumps for those systems that are located in the LPCS and
RHR C pump rooms.
The floor drains for the RHR C pump room and the LPCS pump room drain to the same
sump. A single isolation valve, FDR-V-609, located In the drain line, Is designed to
Isolate the LPCS pump room drain from the RHR C pump room drain In the event that
the sump Is overfilled. This nonsafety-related Isolation valve is air operated via a four
way shuttle valve and accumulator. During normal operation the Isolation valve Is
opened and closed by supplying or removing air pressure to the four way shuttle valve
which ports the air to the isolation valve operator and the accumulator. The system Is
designed such that the isolation valve should fall closed on a loss of air supply pressure.
This air supply Is controlled (on/off) by a solenoid operated valve, FDR-SPV-609 which
Is upstream of the four way shuttle valve. The licensee believes that during the flooding
event the solenoid operated valve failed to fully close which resulted in a reduction of
pressure in the accumulator (resulting in a lower force to drive the sump Isolation valve
closed) and a failure to vent the air supply line to atmosphere (higher pressure In the
IN 98-31 August 18, 1998 supply line opposes closing of the sump isolation valve). As a result, the sump isolation
valve failed to close automatically when the sump reached Its high level trip point. This
allowed water from the RHR C pump room to flow through the 3-inch sump cross- connect piping and into the LPCS pump room flooding it to a level just below the pump
motor. Plant operators were unable to close the isolation valve manually from the
control room. The licensee's preliminary failure analysis Indicated that the solenoid
operated valve, an ASCO model #WJNP831654E, likely failed to operate due to age
hardening of the Buna-N diaphragm. The licensee believes that this diaphragm has not
been replaced since initial plant construction. The licensee was continuing its failure
analysis at the time this Information Notice was Issued.
Ill
Licensee Corrective Actions
As an Immediate corrective action, the licensee pumped the water from the flooded
areas. The fire protection system was returned to a functional (but degraded) status by
isolating the ruptured valve and returning the PRE-ACTION system to Its normal
condition. Subsequently, the licensee repaired or replaced all affected components.
The ruptured 12-inch cast-iron valve was replaced with a cast-steel valve. As interim
corrective actions, the licensee has established a nitrogen bubble at the top of both the
fire water system risers In the reactor building to provide a cushioning effect, and is
maintaining two fire pumps In continuous operation in order to avoid the significant
voiding expected during postulated PRE-ACTION scenarios. The licensee briefed NRC
management on the corrective actions at a public meeting In the Region IV offices in
Arlington, Texas, on July 2, 1998. The licensee committed to long-term corrective
actions, which included reviews to determine if the flooding analysis in the final safety
analysis report is adequate and whether the floor drain valves and door seals meet
design requirements. Additionally, the licensee is reviewing potential design changes
for the fire protection system to eliminate the susceptibility to water hammer. The
licensee restarted the unit on July 3, 1998.
An NRC augmented inspection team (AIT) was on site from June 17 to 23, 1998. The
results of the AIT were presented at a public exit meeting on site on July 8, 1998, and
were documented in NRC Inspection Report 50-397/98-16, which was Issued on
July 17, 1998. Preliminary Notification of Occurrence PNO-IV-98-026, which described
this event, was issued on June 18, 1998, updated on June 19, 1998, and updated again
on June 23, 1998.
-IN
98-31 August 18, 1998 This information notice requires no specific action or written response. However, licensees are
expected to review the information provided to determine whether similar system vulnerabilities
exist at their facilities. Additionally, recipients are reminded that they are required by 10 CFR
50.65 to take industry-wide operating experience (including the information presented in NRC
information notices) into consideration, where practical, when setting goals and performing
periodic evaluations. 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 Project Management
Office of Nuclear Reactor Regulation
Technical contacts:
Jeffrey Shackelford, Region IV
817-860-8144 E-mail: jls2@nrc.gov
Phillip Qualls, NRR
301-415-1849 E-mail: pmq@nrc.gov
Charles Petrone, NRR
301-415-1027 E-mail cdp@nrc.gov
Attachment: List of Recently Published Information Notices
7AZ
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A' T
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Attachment
August 18, 1998
Page 1 of I
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
98-30
98-29
Effect of the Year 200 Computer
Problem on NRC Licensees and
Certificate Holders
8/12/98
All material and fuel cycle
licensees and certificate holders
Predicted increase In Fuel Rod
Cladding Oxidation
Development of Systematic
Sample Plan for Operator
Licensing Examinations
Steam Generator Tube End
Cracking
813198
8/3/98
7124198
98-28
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.
All holders of operating licenses
for nuclear power plants
All holders of operating licenses
for pressurized-water reactors
except those who have
permanently ceased operation
and have certified that fuel has
been permanently removed for
the reactor vessel
98-27
96-48, Sup. 1 Motor-Operated Valve
Performance Issues
7/24198
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.
01 = Operating License
CP = Construction Permit
IN 98-31 August 18, 1998 This information notice requires no specific action or written response. However, licensees are
expected to review the information provided to determine whether similar system vulnerabilities
exist at their facilities. Additionally, recipients are reminded that they are required by 10 CFR
50.65 to take industry-wide operating experience (including the information presented in NRC
information notices) into consideration, where practical, when setting goals and performing
periodic evaluations. 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.
orig Is/'d by C.l. Grimes
for
Jack W. Roe, Acting Director
Division of Reactor Project Management
Office of Nuclear Reactor Regulation
Technical contacts:
Jeffrey Shackelford, Region IV
817-860-8144 E-mail: jIs2@nrc.gov
Phillip Qualls, NRR
301-415-1849 E-mail: pmq@nrc.gov
Charles Petrone, NRR
301-415-1027 E-mail cdp@nrc.gov
Attachment: List of Recently Published Information Notices
DOCUMENT NAME: G:\\CDP\\WNP-IN.003
- SEE PREVIOUS CONCURRENCE
To receive a copy of this document, Indicate in the box C=Copy wlo attachment/enclosure E=Copy with attachment/enclosure N = No copy
OFFICE
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DATE
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7/20/98
7/22/98
7/24/98
OFFICIAL RECORD COPY
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7/30/98
87/98
IN 98- xx
Julyxx, 19 Page 5 This information notice requires no specific action or written response. Ho ever, licensees are
expected to review the information provided to determine whether similar ystem vulnerabilities
exist at their facilities. Additionally, recipients are reminded that they
e required by 10 CFR
50.65 to take industry-wide operating experience (including the info
tion presented in NRC
information notices) into consideration, where practical, when settin goals and performing
periodic evaluations. If you have any questions about the inform
on in this notice, please
contact one of the technical contacts listed below or the approprite Office of Nuclear Reactor
Regulation (NRR) Project Manager.
Jack W. Ro , Acting Director
Division of
eactor Project Management
Office o0'Nuclear Reactor Regulation
Technical contacts:
Jeffrey Shackelford, Region IV
817-860-8144
/
E-mail: jIs2@nrc.9ov
Phillip QuaRls, RR
301-415-184, E-mail: pm#@nrc.gov
Charles fetrone, NRR
301-41 ,-1027 E-ma cdp@nrc.gov
Attachment: List of Rece tly Published Information Notices
DOCUMENT NAME: G CDP\\WNP-IN.003
- SEE PREVIOUS CO CURRENCE
To receive a copy of this document, Ind'te In the box C=Copy wlo attachmentlenclosure E=Copy with attachmentlenclosure N = No copy
[OFFICE
PECB* i
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7/22/98
7/24/98
OFFICIAL RECORD COPY
OFFICE
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IN 98-xx
July xx, 1998 This information notice requires no specific action or written response. However, licensees
should review the information provided to determine whether similar system vulnerabilities exist
at their facilities. Additionally, recipients are reminded that they are required by 10 CFR 50.65 to take industry-wide operating experience (including the information presented in NRC
-
information notices) into consideration, where practical, when setting goals and perfor
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periodic evaluations. If you have any questions about the information in this noti
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contact one of the technical contacts listed below or the appropriate Office of
lear Reactor
Regulation (NRR) Project Manager.
Jack W. Roe, Acting
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Division of Reactor oject Management
Office of Nuclea
eactor Regulation
Technical contacts:
Jeffrey Shackelford, Region
817-860-8144 E-mail: jls2@nrc.gov
Phillip Qualls, NRR
301-415-1849 E-mail: pmq@ c.gov
Charles Pe one, NRR
301-415-
27 E-mail
p@nrc.gov
Attachment: List of Rece y Published Information Notices
DOCUMENT NAME:
- \\CDP\\WNP-IN.0
(
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- SEE PREVIOUS C NCURRENCE
To receive a copy of this document
dicate in the box C=Copy wfo attachment/enclosure E=Copy with attachment/enclosure N = No copy
OFFICE
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7/22/98(email)
7/22/98 (email)
7/ /98
7/ /98
IN 98-xx
July xx, 1998 This information notice requires no specific action or written response. However, licensees
should review the information provided to determine whether similar system vulnerabilities exist
at their facilities. Additionally, recipients are reminded that they are required by 10 CFR 50.65 to take industry-wide operating experience (including the information presented in NRC
information notices) into consideration, where practical, when setting goals and performing
periodic evaluations. 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 Project Management
Office of Nuclear Reactor Regulation
Technical contacts:
Jeffrey Shackelford, Region IV
817-860-8144 E-mail: jls2@nrc.gov
Phillip Qualls, NRR
301-415-1849 E-mail: pmq@nrc.gov
Charles Petrone, NRR
301-415-1027 E-mail cdp@nrc.gov
Attachment: List of Recently Published Information
DOCUMENT NAME: G:\\CDP\\WNP-IN.00%
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To receive a copy of this document, Indicate In the box C=Copy wlo attachmentlenclosure E=Copy with attachment/enclosure N = No copy
OFFICE
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