Information Notice 1994-29, Charging Pump Trip During a Loss-of-Coolant Event Caused by Low Suction Pressure: Difference between revisions

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{{#Wiki_filter:I.' 4 AUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555April 11, 1994NRC INFORMATION NOTICE 94-29: CHARGING PUMP TRIP DURING A LOSS-OF-COOLANTEVENT CAUSED BY LOW SUCTION PRESSURE
{{#Wiki_filter:I.' 4 A UNITED STATES NUCLEAR REGULATORY
 
COMMISSION
 
===OFFICE OF NUCLEAR REACTOR REGULATION===
WASHINGTON, D.C. 20555 April 11, 1994 NRC INFORMATION
 
NOTICE 94-29: CHARGING PUMP TRIP DURING A LOSS-OF-COOLANT
 
EVENT CAUSED BY LOW SUCTION PRESSURE


==Addressees==
==Addressees==
All holders of operating licenses or construction permits for pressurized-water reactors.
All holders of operating
 
licenses or construction
 
permits for pressurized- water reactors.


==Purpose==
==Purpose==
The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to the possibility of a charging pump trip causedby inadequate suction pressure because too many pumps may be aligned to asingle suction path during accident mitigation. It is expected thatrecipients will review the information for applicability to their facilitiesand 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.
The U.S. Nuclear Regulatory
 
Commission (NRC) is issuing this information
 
notice to alert addressees
 
to the possibility
 
of a charging pump trip caused by inadequate
 
suction pressure because too many pumps may be aligned to a single suction path during accident mitigation.
 
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
 
During a steam generator
 
tube rupture event at Palo Verde Unit 2 on March 14, 1993 (NRC Inspection
 
Report 50-279/93-14), a charging pump tripped off on low suction pressure when the operators
 
switched the charging pump suction source from the volume control tank to the refueling
 
water tank. During the subsequent
 
evaluation
 
of the event, the licensee determined
 
that four pumps, three charging pumps and a boric acid makeup pump, were all taking suction through the same 7.6-cm [3-in.] diameter pipe. The licensee also determined
 
that the high rate of flow through the suction pipe that resulted from the simultaneous
 
operation
 
of all four pumps caused a sufficient
 
pressure reduction
 
at the suction of the pumps to lower this pressure below the low suction trip setpoints
 
of the charging pumps.Two charging pumps were already running when the tube rupture occurred.
 
In addition, the operators
 
were running a boric acid pump to circulate
 
the refueling
 
water through filters to purify it for an upcoming outage; The boric acid pump flow was being recirculated
 
back to the refueling
 
water tank and did not contribute
 
to the makeup water going into the reactor coolant system. The operators
 
started the third charging pump early in the event in an effort to restore the pressurizer
 
level, which was decreasing
 
because of the tube rupture. At that time all of the charging pumps were taking suction from the volume control tank, which is the normal source of makeup water for the reactor coolant system. Approximately
 
30 minutes later, in accordance
 
with emergency
 
procedures, the operators
 
opened the suction valve from the 9404060036 po-rXE qq-D29 qqoqI n TkId9L III
 
IN 94-29-V April 11, 1994 refueling
 
water tank and then closed the suction valve from the volume control tank.At this point one of the charging pumps tripped off. The operators
 
were able to restore the tripped charging pump to operation
 
by realigning
 
the suction of the charging pumps to other suction paths from the refueling
 
water tank.Discussion
 
Following
 
this event the licensee calculated
 
that, with the boric acid pump running, the remaining
 
flow capacity of the refueling
 
water tank suction source that was in use was Just sufficient
 
for two charging pumps. With all four pumps running the suction pressure was below the low suction trip set points (81.0 kPa to 87.2 kPa [11.75 psia to 12.65 psia]) for the charging pumps. Because the trip set points are set at slightly different
 
pressures, only one pump tripped. Once this first pump tripped, the resulting
 
rise in suction pressure allowed the remaining
 
pumps to keep running.The licensee concluded
 
that, if recirculation
 
by the boric acid pump is not in progress, sufficient
 
suction pressure exists for all three charging-pumps.
 
Consequently, the licensee revised the emergency
 
procedures
 
that involve the charging pumps to specify that any ongoing recirculation
 
of the refueling water by the boric acid pump is to be terminated
 
when refueling
 
water is needed for emergency
 
makeup.Licensees
 
of pressurized-water
 
reactors use the charging systems in a number of ways for accident mitigation, such as including
 
the charging system as a part of the automatic
 
safety injection
 
system. Charging systems are also used as a source of pressurizer
 
spray to depressurize
 
the reactor when the reactor coolant pumps are shut down. Emergency
 
operating
 
procedures
 
often refer to the charging systems for other uses as well.Some licensees
 
do not isolate the volume control tank (or its equivalent)
when the charging system source is switched to the refueling
 
water tank (or its equivalent), but depend on the static pressure in the refueling
 
water tank to keep the volume control tank from draining.
 
Should the volume control tank empty in response to lower-than-expected
 
suction pressure, hydrogen cover gas normally contained
 
in this tank could enter the charging system suction and cause the pumps to malfunction.
 
IN 94-29 April 11, 1994 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact the technical
 
contact listed below or the appropriate
 
Office of Nuclear Reactor Regulation
 
project manager.Brian K. Gr es, Director ter-Division of Operating
 
===Reactor Support Office of Nuclear Reactor Regulation===
Technical
 
contact: Warren C. Lyon, NRR (301) 504-3892 Attachment:
List of Recently Issued NRC Information
 
Notices
 
Ak-1achment
 
IN 94-29 April 12, 1994 LIST OF RECENTLY ISSUED NRC INFORMATION
 
NOTICES Information
 
Date of Notice No. Subject Issuance Issued to 92-51, Supp. 1 94-28 94-27 94-26 Misapplication
 
and Inadequate
 
Testing of Molded-Case
 
Circuit Breakers Potential
 
Problems with Fire-Barrier
 
Penetration
 
Seals Facility Operating Concerns Resulting
 
from Local Area Flooding Personnel
 
Hazards and Other Problems from Smoldering
 
Fire-Retard- ant Material in the Drywell of a Boiling-Water Reactor Safety Systems Response to Loss of Coolant and Loss of Offsite Power Failure of Containment
 
Spray Header Valve to Open due to Excessive Pressure from Inertial Effects of Water Inadequate
 
Maintenance
 
of Uninterruptible
 
Power Supplies and Inverters Guidance to Hazardous, Radioactive
 
and Mixed Waste Generators
 
on the Elements of a Waste Minimization
 
Program 04/12/94 04/05/94 03/31/94 03/28/94 03/25/94 03/25/94 03/24/94 03/25/94 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All NRC Licensees.
 
93-17, Rev. 1 94-25 94-24 94-23 OL -Operating
 
License CP -Construction
 
Permit
 
.I If IN 94-29 April 11, 1994 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact the technical
 
contact listed below or the appropriate
 
Office of Nuclear Reactor Regulation
 
project manager.orig /s/'d by CIGrimes Brian K. Grimes, Director Division of Operating
 
===Reactor Support Office of Nuclear Reactor Regulation===
Technical
 
contact: Warren C. Lyon, NRR (301) 504-3892 Attachment:
List of Recently Issued NRC Information
 
Notices*SEE PREVIOUS CONCURRENCE
 
OFFICE *OGCB *TECH ED *SRXB/DSSA
 
*C:SRXB/DSSA
 
NAME DCKirkpatrick
 
RSanders WCLyon RJones DATE 111/30/93
111/30/93 , 12/20/93 12/22/93*D:DSSA*C:OGCB/DORS
 
D:DORS/NRR
 
AThadani GHMarcus BKGrimes6 01/04/94 01/11/94 04/L /94 VULUMMN NAME: 4-M. IN
 
IN 94-xx March xx, 1994 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact the technical
 
contact listed below or the appropriate
 
Office of Nuclear Reactor Regulation
 
project manager.Brian K. Grimes, Director Division of Operating
 
===Reactor Support Office of Nuclear Reactor Regulation===
Technical
 
contact: Warren C. Lyon, NRR (301) 504-3892*SFF PREVOUS CONCURRENCE
 
OFFICE *OGCB *TECH ED *SRXB/DSSA
 
*C:SRXB/DSSA
 
NAME DCKirkpatrick
 
RSanders WCLyon RJones DATE 11/30/93 11/30/93 12/20/93 1 12/22/93.-- .1*D: DSSA*C:OGCB/DORS
 
D:DORS/NRR
 
AThadani GHMarcus BKGrimes 01/04/94 01/11/94 03/ /94 I=01tw DOCUMENT NAME: CHARGING.DCK
 
IN 94-xx January xx, 1994 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact the technical
 
contact listed below or the appropriate
 
Office of Nuclear Reactor Regulation
 
project manager.Brian K. Grimes, Director Division of Operating
 
===Reactor Support Office of Nuclear Reactor Regulation===
Technical
 
Contact: Warren C. Lyon, (301) 504-3892 NRR*SEE PREVIOUS CONCURRENCE
 
OFFICE *OGCB *TECH ED *SRXB/DSSA
 
*C:SRXB/DSSA
 
NAME DCKirkpatrick
 
I RSanders WCLyon RJones DATE I1/30/93 J >/BY 11/30/93 112/20/93
12/22/93 D:DSSA Okl C:OGCB/DORS
 
D:DORS/NRR
 
c llAThadani GHMarcus MYA1 BKGrimes 01/04/94 01/ti/94 01/ /94 DOCUMENT NAME: CHARGING.DCK
 
-* I IN 93-xx December xx, 1993 This information
 
notice requires no specific action or written response.
 
If you have any questions
 
about the information
 
in this notice, please contact the technical
 
contact listed below or the appropriate
 
Office of Nuclear Reactor Regulation
 
project manager.Brian K. Grimes, Director Division of Operating
 
===Reactor Support Office of Nuclear Reactor Regulation===
Technical
 
Contact: Warren C. Lyon, NRR (301) 504-3892 Af. -.-/*SEF PREVIOUS CONCURRENCE
 
,____1 ____ _ _____' /s OFFICE *OGCB *TECH ED ' XifDSSA SU C:SRXB/DSSAI
 
I NAME DCKirkpatrick
 
RSanders WCLyon TC K ns RJones V DATE 11/30/93 1 11/30/93 2 /£ ./z/'?L I3 L , ..a D:DSSAM C:OGCB/DORS
 
D:DORS/NRR
 
ATha n GHMarcus I BKGrimes F 1k/ & _ /91 _ 1 /93r4 DOCUMENT NAME: CHARGING.DCK
 
3 a9 IN 93-xx December xx, 1993 This information
 
notice requires no specific action or written response.
 
If you have any questions


==Description of Circumstances==
about the information
During a steam generator tube rupture event at Palo Verde Unit 2 on March 14,1993 (NRC Inspection Report 50-279/93-14), a charging pump tripped off on lowsuction pressure when the operators switched the charging pump suction sourcefrom the volume control tank to the refueling water tank. During thesubsequent evaluation of the event, the licensee determined that four pumps,three charging pumps and a boric acid makeup pump, were all taking suctionthrough the same 7.6-cm [3-in.] diameter pipe. The licensee also determinedthat the high rate of flow through the suction pipe that resulted from thesimultaneous operation of all four pumps caused a sufficient pressurereduction at the suction of the pumps to lower this pressure below the lowsuction trip setpoints of the charging pumps.Two charging pumps were already running when the tube rupture occurred. Inaddition, the operators were running a boric acid pump to circulate therefueling water through filters to purify it for an upcoming outage; Theboric acid pump flow was being recirculated back to the refueling water tankand did not contribute to the makeup water going into the reactor coolantsystem. The operators started the third charging pump early in the event inan effort to restore the pressurizer level, which was decreasing because ofthe tube rupture. At that time all of the charging pumps were taking suctionfrom the volume control tank, which is the normal source of makeup water forthe reactor coolant system. Approximately 30 minutes later, in accordancewith emergency procedures, the operators opened the suction valve from the9404060036 po-rXE qq-D29 qqoqIn TkId9L III


IN 94-29-V April 11, 1994 refueling water tank and then closed the suction valve from the volume controltank.At this point one of the charging pumps tripped off. The operators were ableto restore the tripped charging pump to operation by realigning the suction ofthe charging pumps to other suction paths from the refueling water tank.DiscussionFollowing this event the licensee calculated that, with the boric acid pumprunning, the remaining flow capacity of the refueling water tank suctionsource that was in use was Just sufficient for two charging pumps. With allfour pumps running the suction pressure was below the low suction trip setpoints (81.0 kPa to 87.2 kPa [11.75 psia to 12.65 psia]) for the chargingpumps. Because the trip set points are set at slightly different pressures,only one pump tripped. Once this first pump tripped, the resulting rise insuction pressure allowed the remaining pumps to keep running.The licensee concluded that, if recirculation by the boric acid pump is not inprogress, sufficient suction pressure exists for all three charging-pumps.Consequently, the licensee revised the emergency procedures that involve thecharging pumps to specify that any ongoing recirculation of the refuelingwater by the boric acid pump is to be terminated when refueling water isneeded for emergency makeup.Licensees of pressurized-water reactors use the charging systems in a numberof ways for accident mitigation, such as including the charging system as apart of the automatic safety injection system. Charging systems are also usedas a source of pressurizer spray to depressurize the reactor when the reactorcoolant pumps are shut down. Emergency operating procedures often refer tothe charging systems for other uses as well.Some licensees do not isolate the volume control tank (or its equivalent) whenthe charging system source is switched to the refueling water tank (or itsequivalent), but depend on the static pressure in the refueling water tank tokeep the volume control tank from draining. Should the volume control tankempty in response to lower-than-expected suction pressure, hydrogen cover gasnormally contained in this tank could enter the charging system suction andcause the pumps to malfunction.
in this notice, please contact the technical


IN 94-29April 11, 1994 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation project manager.Brian K. Gr es, Director ter-Division of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contact: Warren C. Lyon, NRR(301) 504-3892Attachment:List of Recently Issued NRC Information Notices
contact listed below or the appropriate


Ak-1achmentIN 94-29April 12, 1994 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to92-51,Supp. 194-2894-2794-26Misapplication andInadequate Testing ofMolded-Case CircuitBreakersPotential Problems withFire-Barrier PenetrationSealsFacility OperatingConcerns Resulting fromLocal Area FloodingPersonnel Hazards andOther Problems fromSmoldering Fire-Retard-ant Material in theDrywell of a Boiling-Water ReactorSafety Systems Responseto Loss of Coolant andLoss of Offsite PowerFailure of ContainmentSpray Header Valve toOpen due to ExcessivePressure from InertialEffects of WaterInadequate Maintenanceof Uninterruptible PowerSupplies and InvertersGuidance to Hazardous,Radioactive and MixedWaste Generators on theElements of a WasteMinimization Program04/12/9404/05/9403/31/9403/28/9403/25/9403/25/9403/24/9403/25/94All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All NRC Licensees.93-17,Rev. 194-2594-2494-23OL -Operating LicenseCP -Construction Permit
Office of Nuclear Reactor Regulation


.I IfIN 94-29April 11, 1994 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation project manager.orig /s/'d by CIGrimesBrian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contact: Warren C. Lyon, NRR(301) 504-3892Attachment:List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE *OGCB *TECH ED *SRXB/DSSA *C:SRXB/DSSANAME DCKirkpatrick RSanders WCLyon RJonesDATE 111/30/93 111/30/93 , 12/20/93 12/22/93*D:DSSA*C:OGCB/DORSD:DORS/NRRAThadani GHMarcus BKGrimes601/04/94 01/11/94 04/L /94VULUMMN NAME: 4-M. IN
project manager.Brian K. Grimes, Director Division of Operating


IN 94-xxMarch xx, 1994 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contact:Warren C. Lyon, NRR(301) 504-3892*SFF PREVOUS CONCURRENCEOFFICE *OGCB *TECH ED *SRXB/DSSA *C:SRXB/DSSANAME DCKirkpatrick RSanders WCLyon RJonesDATE 11/30/93 11/30/93 12/20/93 1 12/22/93.-- .1*D: DSSA*C:OGCB/DORSD:DORS/NRRAThadani GHMarcus BKGrimes01/04/94 01/11/94 03/ /94I=01twDOCUMENT NAME: CHARGING.DCK
===Reactor Support Office of Nuclear Reactor Regulation===
Technical


IN 94-xxJanuary xx, 1994 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor Regulation
Contact: Warren C. Lyon, NRR (301) 504-3892 t OFFICE OGCB TECH ED SRXBA 54 l C:OGCB/DORS


===Technical Contact:===
D:DORS/NRR
Warren C. Lyon,(301) 504-3892NRR*SEE PREVIOUS CONCURRENCEOFFICE *OGCB *TECH ED *SRXB/DSSA *C:SRXB/DSSANAME DCKirkpatrick I RSanders WCLyon RJonesDATE I1/30/93 J >/BY 11/30/93 112/20/93 12/22/93D:DSSA Okl C:OGCB/DORSD:DORS/NRR c llAThadani GHMarcus MYA1 BKGrimes01/04/94 01/ti/94 01/ /94DOCUMENT NAME: CHARGING.DCK


-* IIN 93-xxDecember xx, 993This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor Regulation
NAME fDCKirkpatrick


===Technical Contact:===
RPoUlm'us
Warren C. Lyon, NRR(301) 504-3892Af. -.-/*SEF PREVIOUS CONCURRENCE,____1 ____ _ _____' /sOFFICE *OGCB *TECH ED ' XifDSSA SU C:SRXB/DSSAI INAME DCKirkpatrick RSanders WCLyon TC K ns RJones VDATE 11/30/93 1 11/30/93 2 /£ ./z/'?L I3L , ..aD:DSSAMC:OGCB/DORSD:DORS/NRRATha n GHMarcus I BKGrimesF 1k/ & _ /91 _ 1 /93r4DOCUMENT NAME: CHARGING.DCK3a9 IN 93-xxDecember xx, 993This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor Regulation


===Technical Contact:===
WCLyon GHMarcus BKGrimes DATE /(1g9/93PZ-@  
Warren C. Lyon, NRR(301) 504-3892t OFFICE OGCB TECH ED SRXBA 54 l C:OGCB/DORS D:DORS/NRRNAME fDCKirkpatrick RPoUlm'us WCLyon GHMarcus BKGrimesDATE /(1g9/93PZ-@ Iit/3093 j/93 / /93 / /93 1DOCUMENT NAME: CHARGING .CK l"05-- 1  
Iit/3093 j/93 / /93 / /93 1 DOCUMENT NAME: CHARGING .CK l"05-- 1}}
}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Revision as of 14:00, 31 August 2018

Charging Pump Trip During a Loss-of-Coolant Event Caused by Low Suction Pressure
ML031060474
Person / Time
Site: Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant  Entergy icon.png
Issue date: 04/11/1994
From: Grimes B K
Office of Nuclear Reactor Regulation
To:
References
IN-94-029, NUDOCS 9404060036
Download: ML031060474 (9)
v • d • e


I.' 4 A UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 April 11, 1994 NRC INFORMATION

NOTICE 94-29: CHARGING PUMP TRIP DURING A LOSS-OF-COOLANT

EVENT CAUSED BY LOW SUCTION PRESSURE

Addressees

All holders of operating

licenses or construction

permits for pressurized- water reactors.

Purpose

The U.S. Nuclear Regulatory

Commission (NRC) is issuing this information

notice to alert addressees

to the possibility

of a charging pump trip caused by inadequate

suction pressure because too many pumps may be aligned to a single suction path during accident mitigation.

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

During a steam generator

tube rupture event at Palo Verde Unit 2 on March 14, 1993 (NRC Inspection

Report 50-279/93-14), a charging pump tripped off on low suction pressure when the operators

switched the charging pump suction source from the volume control tank to the refueling

water tank. During the subsequent

evaluation

of the event, the licensee determined

that four pumps, three charging pumps and a boric acid makeup pump, were all taking suction through the same 7.6-cm [3-in.] diameter pipe. The licensee also determined

that the high rate of flow through the suction pipe that resulted from the simultaneous

operation

of all four pumps caused a sufficient

pressure reduction

at the suction of the pumps to lower this pressure below the low suction trip setpoints

of the charging pumps.Two charging pumps were already running when the tube rupture occurred.

In addition, the operators

were running a boric acid pump to circulate

the refueling

water through filters to purify it for an upcoming outage; The boric acid pump flow was being recirculated

back to the refueling

water tank and did not contribute

to the makeup water going into the reactor coolant system. The operators

started the third charging pump early in the event in an effort to restore the pressurizer

level, which was decreasing

because of the tube rupture. At that time all of the charging pumps were taking suction from the volume control tank, which is the normal source of makeup water for the reactor coolant system. Approximately

30 minutes later, in accordance

with emergency

procedures, the operators

opened the suction valve from the 9404060036 po-rXE qq-D29 qqoqI n TkId9L III

IN 94-29-V April 11, 1994 refueling

water tank and then closed the suction valve from the volume control tank.At this point one of the charging pumps tripped off. The operators

were able to restore the tripped charging pump to operation

by realigning

the suction of the charging pumps to other suction paths from the refueling

water tank.Discussion

Following

this event the licensee calculated

that, with the boric acid pump running, the remaining

flow capacity of the refueling

water tank suction source that was in use was Just sufficient

for two charging pumps. With all four pumps running the suction pressure was below the low suction trip set points (81.0 kPa to 87.2 kPa [11.75 psia to 12.65 psia]) for the charging pumps. Because the trip set points are set at slightly different

pressures, only one pump tripped. Once this first pump tripped, the resulting

rise in suction pressure allowed the remaining

pumps to keep running.The licensee concluded

that, if recirculation

by the boric acid pump is not in progress, sufficient

suction pressure exists for all three charging-pumps.

Consequently, the licensee revised the emergency

procedures

that involve the charging pumps to specify that any ongoing recirculation

of the refueling water by the boric acid pump is to be terminated

when refueling

water is needed for emergency

makeup.Licensees

of pressurized-water

reactors use the charging systems in a number of ways for accident mitigation, such as including

the charging system as a part of the automatic

safety injection

system. Charging systems are also used as a source of pressurizer

spray to depressurize

the reactor when the reactor coolant pumps are shut down. Emergency

operating

procedures

often refer to the charging systems for other uses as well.Some licensees

do not isolate the volume control tank (or its equivalent)

when the charging system source is switched to the refueling

water tank (or its equivalent), but depend on the static pressure in the refueling

water tank to keep the volume control tank from draining.

Should the volume control tank empty in response to lower-than-expected

suction pressure, hydrogen cover gas normally contained

in this tank could enter the charging system suction and cause the pumps to malfunction.

IN 94-29 April 11, 1994 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation

project manager.Brian K. Gr es, Director ter-Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contact: Warren C. Lyon, NRR (301) 504-3892 Attachment:

List of Recently Issued NRC Information

Notices

Ak-1achment

IN 94-29 April 12, 1994 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 92-51, Supp. 1 94-28 94-27 94-26 Misapplication

and Inadequate

Testing of Molded-Case

Circuit Breakers Potential

Problems with Fire-Barrier

Penetration

Seals Facility Operating Concerns Resulting

from Local Area Flooding Personnel

Hazards and Other Problems from Smoldering

Fire-Retard- ant Material in the Drywell of a Boiling-Water Reactor Safety Systems Response to Loss of Coolant and Loss of Offsite Power Failure of Containment

Spray Header Valve to Open due to Excessive Pressure from Inertial Effects of Water Inadequate

Maintenance

of Uninterruptible

Power Supplies and Inverters Guidance to Hazardous, Radioactive

and Mixed Waste Generators

on the Elements of a Waste Minimization

Program 04/12/94 04/05/94 03/31/94 03/28/94 03/25/94 03/25/94 03/24/94 03/25/94 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All NRC Licensees.

93-17, Rev. 1 94-25 94-24 94-23 OL -Operating

License CP -Construction

Permit

.I If IN 94-29 April 11, 1994 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation

project manager.orig /s/'d by CIGrimes Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contact: Warren C. Lyon, NRR (301) 504-3892 Attachment:

List of Recently Issued NRC Information

Notices*SEE PREVIOUS CONCURRENCE

OFFICE *OGCB *TECH ED *SRXB/DSSA

  • C:SRXB/DSSA

NAME DCKirkpatrick

RSanders WCLyon RJones DATE 111/30/93

111/30/93 , 12/20/93 12/22/93*D:DSSA*C:OGCB/DORS

D:DORS/NRR

AThadani GHMarcus BKGrimes6 01/04/94 01/11/94 04/L /94 VULUMMN NAME: 4-M. IN

IN 94-xx March xx, 1994 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation

project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contact: Warren C. Lyon, NRR (301) 504-3892*SFF PREVOUS CONCURRENCE

OFFICE *OGCB *TECH ED *SRXB/DSSA

  • C:SRXB/DSSA

NAME DCKirkpatrick

RSanders WCLyon RJones DATE 11/30/93 11/30/93 12/20/93 1 12/22/93.-- .1*D: DSSA*C:OGCB/DORS

D:DORS/NRR

AThadani GHMarcus BKGrimes 01/04/94 01/11/94 03/ /94 I=01tw DOCUMENT NAME: CHARGING.DCK

IN 94-xx January xx, 1994 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation

project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

Contact: Warren C. Lyon, (301) 504-3892 NRR*SEE PREVIOUS CONCURRENCE

OFFICE *OGCB *TECH ED *SRXB/DSSA

  • C:SRXB/DSSA

NAME DCKirkpatrick

I RSanders WCLyon RJones DATE I1/30/93 J >/BY 11/30/93 112/20/93

12/22/93 D:DSSA Okl C:OGCB/DORS

D:DORS/NRR

c llAThadani GHMarcus MYA1 BKGrimes 01/04/94 01/ti/94 01/ /94 DOCUMENT NAME: CHARGING.DCK

-* I IN 93-xx December xx, 1993 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation

project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

Contact: Warren C. Lyon, NRR (301) 504-3892 Af. -.-/*SEF PREVIOUS CONCURRENCE

,____1 ____ _ _____' /s OFFICE *OGCB *TECH ED ' XifDSSA SU C:SRXB/DSSAI

I NAME DCKirkpatrick

RSanders WCLyon TC K ns RJones V DATE 11/30/93 1 11/30/93 2 /£ ./z/'?L I3 L , ..a D:DSSAM C:OGCB/DORS

D:DORS/NRR

ATha n GHMarcus I BKGrimes F 1k/ & _ /91 _ 1 /93r4 DOCUMENT NAME: CHARGING.DCK

3 a9 IN 93-xx December xx, 1993 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation

project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

Contact: Warren C. Lyon, NRR (301) 504-3892 t OFFICE OGCB TECH ED SRXBA 54 l C:OGCB/DORS

D:DORS/NRR

NAME fDCKirkpatrick

RPoUlm'us

WCLyon GHMarcus BKGrimes DATE /(1g9/93PZ-@

Iit/3093 j/93 / /93 / /93 1 DOCUMENT NAME: CHARGING .CK l"05-- 1


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