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 A UNITED STATES NUCLEAR REGULATORY
{{#Wiki_filter:I


COMMISSION
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===OFFICE OF NUCLEAR REACTOR REGULATION===
UNITED STATES
WASHINGTON, D.C. 20555 April 11, 1994 NRC INFORMATION


NOTICE 94-29: CHARGING PUMP TRIP DURING A LOSS-OF-COOLANT
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
EVENT CAUSED BY LOW SUCTION PRESSURE


==Addressees==
==Addressees==
All holders of operating
All holders of operating licenses or construction permits for pressurized- water reactors.
 
==Purpose==
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information


licenses or construction
notice to alert addressees to the possibility of a charging pump trip caused


permits for pressurized- water reactors.
by inadequate suction pressure because too many pumps may be aligned to a


==Purpose==
single suction path during accident mitigation. It is expected that
The U.S. Nuclear Regulatory


Commission (NRC) is issuing this information
recipients will review the information for applicability to their facilities


notice to alert addressees
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.


to the possibility
==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


of a charging pump trip caused by inadequate
suction pressure when the operators switched the charging pump suction source


suction pressure because too many pumps may be aligned to a single suction path during accident mitigation.
from the volume control tank to the refueling water tank. During the


It is expected that recipients
subsequent evaluation of the event, the licensee determined that four pumps, three charging pumps and a boric acid makeup pump, were all taking suction


will review the information
through the same 7.6-cm [3-in.] diameter pipe. The licensee also determined


for applicability
that the high rate of flow through the suction pipe that resulted from the


to their facilities
simultaneous operation of all four pumps caused a sufficient pressure


and consider actions, as appropriate, to avoid similar problems.
reduction at the suction of the pumps to lower this pressure below the low


However, suggestions
suction trip setpoints of the charging pumps.


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


in this information
addition, the operators were running a boric acid pump to circulate the


notice are not NRC requirements;
refueling water through filters to purify it for an upcoming outage; The
therefore, no specific action or written response is required.Description


of Circumstances
boric acid pump flow was being recirculated back to the refueling water tank


During a steam generator
and did not contribute to the makeup water going into the reactor coolant


tube rupture event at Palo Verde Unit 2 on March 14, 1993 (NRC Inspection
system. The operators started the third charging pump early in the event in


Report 50-279/93-14), a charging pump tripped off on low suction pressure when the operators
an effort to restore the pressurizer level, which was decreasing because of


switched the charging pump suction source from the volume control tank to the refueling
the tube rupture. At that time all of the charging pumps were taking suction


water tank. During the subsequent
from the volume control tank, which is the normal source of makeup water for


evaluation
the reactor coolant system. Approximately 30 minutes later, in accordance


of the event, the licensee determined
with emergency procedures, the operators opened the suction valve from the


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
9404060036      po-rXE                        qq-D29      qqoqI


that the high rate of flow through the suction pipe that resulted from the simultaneous
n        TkId9L                                                                III


operation
IN 94-29
                                                        - V April 11, 1994 refueling water tank and then closed the suction valve from the volume control


of all four pumps caused a sufficient
tank.


pressure reduction
At this point one of the charging pumps tripped off. The operators were able


at the suction of the pumps to lower this pressure below the low suction trip setpoints
to restore the tripped charging pump to operation by realigning the suction of


of the charging pumps.Two charging pumps were already running when the tube rupture occurred.
the charging pumps to other suction paths from the refueling water tank.


In addition, the operators
Discussion


were running a boric acid pump to circulate
Following this event the licensee calculated that, with the boric acid pump


the refueling
running, the remaining flow capacity of the refueling water tank suction


water through filters to purify it for an upcoming outage; The boric acid pump flow was being recirculated
source that was in use was Just sufficient for two charging pumps. With all


back to the refueling
four pumps running the suction pressure was below the low suction trip set


water tank and did not contribute
points (81.0 kPa to 87.2 kPa [11.75 psia to 12.65 psia]) for the charging


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


started the third charging pump early in the event in an effort to restore the pressurizer
suction pressure allowed the remaining pumps to keep running.


level, which was decreasing
The licensee concluded that, if recirculation by the boric acid pump is not in


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
progress, sufficient suction pressure exists for all three charging-pumps.


30 minutes later, in accordance
Consequently, the licensee revised the emergency procedures that involve the


with emergency
charging pumps to specify that any ongoing recirculation of the refueling


procedures, the operators
water by the boric acid pump is to be terminated when refueling water is


opened the suction valve from the 9404060036 po-rXE qq-D29 qqoqI n TkId9L III
needed for emergency makeup.


IN 94-29-V April 11, 1994 refueling
Licensees of pressurized-water reactors use the charging systems in a number


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
of ways for accident mitigation, such as including the charging system as a


were able to restore the tripped charging pump to operation
part of the automatic safety injection system. Charging systems are also used


by realigning
as a source of pressurizer spray to depressurize the reactor when the reactor


the suction of the charging pumps to other suction paths from the refueling
coolant pumps are shut down. Emergency operating procedures often refer to


water tank.Discussion
the charging systems for other uses as well.


Following
Some licensees do not isolate the volume control tank (or its equivalent) when


this event the licensee calculated
the charging system source is switched to the refueling water tank (or its


that, with the boric acid pump running, the remaining
equivalent), but depend on the static pressure in the refueling water tank to


flow capacity of the refueling
keep the volume control tank from draining. Should the volume control tank


water tank suction source that was in use was Just sufficient
empty in response to lower-than-expected suction pressure, hydrogen cover gas


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
normally contained in this tank could enter the charging system suction and


pressures, only one pump tripped. Once this first pump tripped, the resulting
cause the pumps to malfunction.


rise in suction pressure allowed the remaining
IN 94-29 April 11, 1994 This information notice requires no specific action or written response. If


pumps to keep running.The licensee concluded
you have any questions about the information in this notice, please contact


that, if recirculation
the technical contact listed below or the appropriate Office of Nuclear


by the boric acid pump is not in progress, sufficient
Reactor Regulation project manager.


suction pressure exists for all three charging-pumps.
Brian K. Gr es, Director ter- Division of Operating Reactor Support


Consequently, the licensee revised the emergency
Office of Nuclear Reactor Regulation


procedures
Technical contact:  Warren C. Lyon, NRR


that involve the charging pumps to specify that any ongoing recirculation
(301) 504-3892 Attachment:


of the refueling water by the boric acid pump is to be terminated
===List of Recently Issued NRC Information Notices===


when refueling
Ak-1achment


water is needed for emergency
IN 94-29 April 12, 1994 LIST OF RECENTLY ISSUED


makeup.Licensees
NRC INFORMATION NOTICES


of pressurized-water
Information                                  Date of


reactors use the charging systems in a number of ways for accident mitigation, such as including
Notice No.            Subject                Issuance    Issued to


the charging system as a part of the automatic
92-51,        Misapplication and            04/12/94  All holders of OLs or CPs


safety injection
Supp. 1        Inadequate Testing of                      for nuclear power reactors.


system. Charging systems are also used as a source of pressurizer
Molded-Case Circuit


spray to depressurize
Breakers


the reactor when the reactor coolant pumps are shut down. Emergency
94-28          Potential Problems with      04/05/94    All holders of OLs or CPs


operating
Fire-Barrier Penetration                  for nuclear power reactors.


procedures
Seals


often refer to the charging systems for other uses as well.Some licensees
94-27          Facility Operating            03/31/94    All holders of OLs or CPs


do not isolate the volume control tank (or its equivalent)
Concerns Resulting from                    for nuclear power reactors.
when the charging system source is switched to the refueling


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


water tank to keep the volume control tank from draining.
94-26          Personnel Hazards and          03/28/94    All holders of OLs or CPs


Should the volume control tank empty in response to lower-than-expected
Other Problems from                        for nuclear power reactors.


suction pressure, hydrogen cover gas normally contained
Smoldering Fire-Retard- ant Material in the


in this tank could enter the charging system suction and cause the pumps to malfunction.
Drywell of a Boiling- Water Reactor


IN 94-29 April 11, 1994 This information
93-17,         Safety Systems Response        03/25/94    All holders of OLs or CPs


notice requires no specific action or written response.
Rev. 1        to Loss of Coolant and                    for nuclear power.


If you have any questions
Loss of Offsite Power


about the information
94-25          Failure of Containment        03/25/94    All holders of OLs or CPs


in this notice, please contact the technical
Spray Header Valve to                      for nuclear power reactors.


contact listed below or the appropriate
Open due to Excessive


Office of Nuclear Reactor Regulation
Pressure from Inertial


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


===Reactor Support Office of Nuclear Reactor Regulation===
94-24          Inadequate Maintenance        03/24/94    All holders of OLs or CPs
Technical


contact: Warren C. Lyon, NRR (301) 504-3892 Attachment:
of Uninterruptible Power                  for nuclear power reactors.
List of Recently Issued NRC Information


Notices
Supplies and Inverters


Ak-1achment
94-23          Guidance to Hazardous,        03/25/94    All NRC Licensees.


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


NOTICES Information
Waste Generators on the


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


and Inadequate
Minimization Program


Testing of Molded-Case
OL - Operating License


Circuit Breakers Potential
CP - Construction Permit


Problems with Fire-Barrier
. I If                                                                  IN 94-29 April 11, 1994 This information notice requires no specific action or written response. If


Penetration
you have any questions about the information in this notice, please contact


Seals Facility Operating Concerns Resulting
the technical contact listed below or the appropriate Office of Nuclear


from Local Area Flooding Personnel
Reactor Regulation project manager.


Hazards and Other Problems from Smoldering
orig /s/'d by CIGrimes


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
Brian K. Grimes, Director


Spray Header Valve to Open due to Excessive Pressure from Inertial Effects of Water Inadequate
Division of Operating Reactor Support


Maintenance
Office of Nuclear Reactor Regulation


of Uninterruptible
Technical contact:    Warren C. Lyon, NRR


Power Supplies and Inverters Guidance to Hazardous, Radioactive
(301) 504-3892 Attachment:
      List of Recently Issued NRC Information Notices


and Mixed Waste Generators
*SEE PREVIOUS CONCURRENCE


on the Elements of a Waste Minimization
OFFICE  *OGCB            *TECH ED    *SRXB/DSSA  *C:SRXB/DSSA


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.
NAME    DCKirkpatrick    RSanders    WCLyon      RJones


93-17, Rev. 1 94-25 94-24 94-23 OL -Operating
DATE  111/30/93         111/30/93    , 12/20/93    12/22/93
        *D:DSSA    *C:OGCB/DORS    D:DORS/NRR


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


Permit
IN 94-xx


.I If IN 94-29 April 11, 1994 This information
March xx, 1994 This information notice requires no specific action or written response. If


notice requires no specific action or written response.
you have any questions about the information in this notice, please contact


If you have any questions
the technical contact listed below or the appropriate Office of Nuclear


about the information
Reactor Regulation project manager.


in this notice, please contact the technical
Brian K. Grimes, Director


contact listed below or the appropriate
Division of Operating Reactor Support


Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


project manager.orig /s/'d by CIGrimes Brian K. Grimes, Director Division of Operating
Technical contact:    Warren C. Lyon, NRR


===Reactor Support Office of Nuclear Reactor Regulation===
(301) 504-3892
Technical
*SFF PREVOUS CONCURRENCE


contact: Warren C. Lyon, NRR (301) 504-3892 Attachment:
OFFICE    *OGCB            *TECH ED        *SRXB/DSSA  *C:SRXB/DSSA
List of Recently Issued NRC Information


Notices*SEE PREVIOUS CONCURRENCE
NAME      DCKirkpatrick    RSanders        WCLyon      RJones


OFFICE *OGCB *TECH ED *SRXB/DSSA
DATE      11/30/93        11/30/93        12/20/93  1 12/22/93
                                        .--  .1
  *D: DSSA    *C:OGCB/DORS    D:DORS/NRR


*C:SRXB/DSSA
AThadani    GHMarcus        BKGrimes


NAME DCKirkpatrick
01/04/94    01/11/94        03/  /94 DOCUMENT  NAME:  CHARGING.DCK                I=01tw


RSanders WCLyon RJones DATE 111/30/93
O                                                                IN 94-xx
111/30/93 , 12/20/93 12/22/93*D:DSSA*C:OGCB/DORS


D:DORS/NRR
January xx, 1994 This information notice requires no specific action or written response. If


AThadani GHMarcus BKGrimes6 01/04/94 01/11/94 04/L /94 VULUMMN NAME: 4-M. IN
you have any questions about the information in this notice, please contact


IN 94-xx March xx, 1994 This information
the technical contact listed below or the appropriate Office of Nuclear


notice requires no specific action or written response.
Reactor Regulation project manager.


If you have any questions
Brian K. Grimes, Director


about the information
Division of Operating Reactor Support
 
in this notice, please contact the technical
 
contact listed below or the appropriate


Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


project manager.Brian K. Grimes, Director Division of Operating
===Technical Contact:===


===Reactor Support Office of Nuclear Reactor Regulation===
===Warren C. Lyon, NRR===
Technical
                        (301) 504-3892
  *SEE PREVIOUS CONCURRENCE


contact: Warren C. Lyon, NRR (301) 504-3892*SFF PREVOUS CONCURRENCE
OFFICE  *OGCB              *TECH ED      *SRXB/DSSA  *C:SRXB/DSSA


OFFICE *OGCB *TECH ED *SRXB/DSSA
NAME    DCKirkpatrick    I RSanders      WCLyon      RJones


*C:SRXB/DSSA
DATE    I1/30/93 >/BYJ 11/30/93        112/20/93    12/22/93 D:DSSA Okl C:OGCB/DORS      D:DORS/NRR  c  ll


NAME DCKirkpatrick
AThadani    GHMarcus MYA1 BKGrimes


RSanders WCLyon RJones DATE 11/30/93 11/30/93 12/20/93 1 12/22/93.-- .1*D: DSSA*C:OGCB/DORS
01/04/94    01/ti/94        01/ /94 DOCUMENT NAME: CHARGING.DCK


D:DORS/NRR
-
* I


AThadani GHMarcus BKGrimes 01/04/94 01/11/94 03/ /94 I=01tw DOCUMENT NAME: CHARGING.DCK
IN 93-xx


IN 94-xx January xx, 1994 This information
December xx, 1993 This information notice requires no specific action or written response. If


notice requires no specific action or written response.
you have any questions about the information in this notice, please contact


If you have any questions
the technical contact listed below or the appropriate Office of Nuclear


about the information
Reactor Regulation project manager.


in this notice, please contact the technical
Brian K. Grimes, Director


contact listed below or the appropriate
Division of Operating Reactor Support


Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


project manager.Brian K. Grimes, Director Division of Operating
===Technical Contact:===


===Reactor Support Office of Nuclear Reactor Regulation===
===Warren C. Lyon, NRR===
Technical
                              (301) 504-3892
      *SEF  PREVIOUS CONCURRENCE                      Af. -.-/      ,
      ____1                        ____                                  _  _____'        /s


Contact: Warren C. Lyon, (301) 504-3892 NRR*SEE PREVIOUS CONCURRENCE
OFFICE  *OGCB                *TECH ED    '  XifDSSA  SU            C:SRXB/DSSAI I


OFFICE *OGCB *TECH ED *SRXB/DSSA
NAME      DCKirkpatrick      RSanders      WCLyon    TC K ns      RJones      V


*C:SRXB/DSSA
DATE    11/30/93          1 11/30/93      2                /£/z/'?L


NAME DCKirkpatrick
.          I3 L,  .              .                a


I RSanders WCLyon RJones DATE I1/30/93 J >/BY 11/30/93 112/20/93
D:DSSAM
12/22/93 D:DSSA Okl C:OGCB/DORS


D:DORS/NRR
ATha


c llAThadani GHMarcus MYA1 BKGrimes 01/04/94 01/ti/94 01/ /94 DOCUMENT NAME: CHARGING.DCK
F1k/
              n


-* I IN 93-xx December xx, 1993 This information
&
                    C:OGCB/DORS


notice requires no specific action or written response.
GHMarcus


If you have any questions
/91
                        _ _
                                  I /93r4
                                  1 D:DORS/NRR


about the information
BKGrimes


in this notice, please contact the technical
DOCUMENT NAME:    CHARGING.DCK


contact listed below or the appropriate
3 a9


Office of Nuclear Reactor Regulation
IN 93-xx


project manager.Brian K. Grimes, Director Division of Operating
December xx, 1993 This information notice requires no specific action or written response. If


===Reactor Support Office of Nuclear Reactor Regulation===
you have any questions about the information in this notice, please contact
Technical


Contact: Warren C. Lyon, NRR (301) 504-3892 Af. -.-/*SEF PREVIOUS CONCURRENCE
the technical contact listed below or the appropriate Office of Nuclear


,____1 ____ _ _____' /s OFFICE *OGCB *TECH ED ' XifDSSA SU C:SRXB/DSSAI
Reactor Regulation project manager.


I NAME DCKirkpatrick
Brian K. Grimes, Director


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
Division of Operating Reactor Support


D:DORS/NRR
Office of Nuclear Reactor Regulation


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


3 a9 IN 93-xx December xx, 1993 This information
===Warren C. Lyon, NRR===
                    (301) 504-3892 t OFFICE


notice requires no specific action or written response.
NAME


If you have any questions
OGCB


about the information
fDCKirkpatrick


in this notice, please contact the technical
TECH ED


contact listed below or the appropriate
RPoUlm'us


Office of Nuclear Reactor Regulation
SRXBA 54 lC:OGCB/DORS


project manager.Brian K. Grimes, Director Division of Operating
WCLyon      GHMarcus
 
===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
D:DORS/NRR


NAME fDCKirkpatrick
BKGrimes


RPoUlm'us
DATE    /(1g9/93PZ-@* Iit/3093        j/93    / /93          / /93            1 DOCUMENT NAME: CHARGING .CK                          l


WCLyon GHMarcus BKGrimes DATE /(1g9/93PZ-@
"05--                                         1}}
Iit/3093 j/93 / /93 / /93 1 DOCUMENT NAME: CHARGING .CK l"05-- 1}}


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

Latest revision as of 04:29, 24 November 2019

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
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, Misapplication and 04/12/94 All holders of OLs or CPs

Supp. 1 Inadequate Testing of for nuclear power reactors.

Molded-Case Circuit

Breakers

94-28 Potential Problems with 04/05/94 All holders of OLs or CPs

Fire-Barrier Penetration for nuclear power reactors.

Seals

94-27 Facility Operating 03/31/94 All holders of OLs or CPs

Concerns Resulting from for nuclear power reactors.

Local Area Flooding

94-26 Personnel Hazards and 03/28/94 All holders of OLs or CPs

Other Problems from for nuclear power reactors.

Smoldering Fire-Retard- ant Material in the

Drywell of a Boiling- Water Reactor

93-17, Safety Systems Response 03/25/94 All holders of OLs or CPs

Rev. 1 to Loss of Coolant and for nuclear power.

Loss of Offsite Power

94-25 Failure of Containment 03/25/94 All holders of OLs or CPs

Spray Header Valve to for nuclear power reactors.

Open due to Excessive

Pressure from Inertial

Effects of Water

94-24 Inadequate Maintenance 03/24/94 All holders of OLs or CPs

of Uninterruptible Power for nuclear power reactors.

Supplies and Inverters

94-23 Guidance to Hazardous, 03/25/94 All NRC Licensees.

Radioactive and Mixed

Waste Generators on the

Elements of a Waste

Minimization Program

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 DOCUMENT NAME: CHARGING.DCK I=01tw

O 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, NRR

(301) 504-3892

  • SEE PREVIOUS CONCURRENCE

OFFICE *OGCB *TECH ED *SRXB/DSSA *C:SRXB/DSSA

NAME DCKirkpatrick I RSanders WCLyon RJones

DATE I1/30/93 >/BYJ 11/30/93 112/20/93 12/22/93 D:DSSA Okl C:OGCB/DORS D:DORS/NRR c ll

AThadani 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

  • SEF PREVIOUS CONCURRENCE Af. -.-/ ,

____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

ATha

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C:OGCB/DORS

GHMarcus

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1 D:DORS/NRR

BKGrimes

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

NAME

OGCB

fDCKirkpatrick

TECH ED

RPoUlm'us

SRXBA 54 lC:OGCB/DORS

WCLyon GHMarcus

D:DORS/NRR

BKGrimes

DATE /(1g9/93PZ-@* Iit/3093 j/93 / /93 / /93 1 DOCUMENT NAME: CHARGING .CK l

"05-- 1


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