Information Notice 2007-18, Operating Experience Regarding Entrainment of Gas or Debris Into Auxiliary Feedwater Systems: Difference between revisions

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{{#Wiki_filter:UNITED STATES
{{#Wiki_filter:UNITED STATES


NUCLEAR REGULATORY COMMISSION
===NUCLEAR REGULATORY COMMISSION===
OFFICE OF NUCLEAR REACTOR REGULATION


OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, DC 20555-0001


WASHINGTON, DC 20555-0001 May 13, 2007 NRC INFORMATION NOTICE 2007-18:               OPERATING EXPERIENCE REGARDING
===May 13, 2007===
NRC INFORMATION NOTICE 2007-18:


===OPERATING EXPERIENCE REGARDING===
ENTRAINMENT OF GAS OR DEBRIS INTO
ENTRAINMENT OF GAS OR DEBRIS INTO


AUXILIARY FEEDWATER SYSTEMS
===AUXILIARY FEEDWATER SYSTEMS===


==ADDRESSEES==
==ADDRESSEES==
Line 38: Line 41:
addressees of operating experience regarding possible entrainment of air or debris into
addressees of operating experience regarding possible entrainment of air or debris into


auxiliary feedwater (AFW) systems, potentially affecting the operability of these systems. The
auxiliary feedwater (AFW) systems, potentially affecting the operability of these systems. The


NRC expects that recipients will review the information for applicability to their facilities and
NRC expects that recipients will review the information for applicability to their facilities and


consider actions, as appropriate, to avoid similar problems. Suggestions contained in this IN
consider actions, as appropriate, to avoid similar problems. Suggestions contained in this IN


are not NRC requirements; therefore, no specific action or written response is required.
are not NRC requirements; therefore, no specific action or written response is required.
Line 49: Line 52:
Several events have occurred at nuclear power facilities involving possible entrainment of gas
Several events have occurred at nuclear power facilities involving possible entrainment of gas


or debris into AFW systems. Air or debris entrained in AFW systems can impact the capability
or debris into AFW systems. Air or debris entrained in AFW systems can impact the capability


of the AFW pumps to perform their specified safety functions. Several recent events are
of the AFW pumps to perform their specified safety functions. Several recent events are


discussed below:
discussed below:
Line 58: Line 61:
A design deficiency resulted in gas coming out of solution and collecting in the nuclear service
A design deficiency resulted in gas coming out of solution and collecting in the nuclear service


water system where the Train A AFW assured suction was located. When this was recognized, the licensee decided to use operator manual alignments to preclude gas entrainment into the
water system where the Train A AFW assured suction was located. When this was recognized, the licensee decided to use operator manual alignments to preclude gas entrainment into the


AFW pumps when alignment was to the standby nuclear service water pond. NRC inspectors
AFW pumps when alignment was to the standby nuclear service water pond. NRC inspectors


identified that the licensee was crediting non-seismic pipe for no less than 30 minutes after a
identified that the licensee was crediting non-seismic pipe for no less than 30 minutes after a


seismic event to allow time to perform the AFW valve lineup. Consequently, there was not
seismic event to allow time to perform the AFW valve lineup. Consequently, there was not


reasonable assurance that the non-seismic pipe would be available to support supplying water
reasonable assurance that the non-seismic pipe would be available to support supplying water


to the AFW pumps. (NRC Integrated Inspection Report 05000369/2004005 and
to the AFW pumps. (NRC Integrated Inspection Report 05000369/2004005 and


05000370/2004005, October 8, 2004, Agencywide Documents Access and Management
05000370/2004005, October 8, 2004, Agencywide Documents Access and Management


System (ADAMS) Accession No. ML042860339)
System (ADAMS) Accession No. ML042860339)  
The licensee subsequently initiated a piping modification and test program to address the issue.
The licensee subsequently initiated a piping modification and test program to address the issue.


Line 82: Line 85:
NRC inspectors identified an inadequate procedure that could have resulted in sufficient air in
NRC inspectors identified an inadequate procedure that could have resulted in sufficient air in


an AFW pump suction to make it inoperable. The procedure addressed the realignment of the
an AFW pump suction to make it inoperable. The procedure addressed the realignment of the


AFW pumps suction from the condensate storage tank to the service water system using a
AFW pumps suction from the condensate storage tank to the service water system using a
Line 88: Line 91:
pipe that was normally voided to preclude potential leakage through a closed valve that could
pipe that was normally voided to preclude potential leakage through a closed valve that could


adversely affect steam generator chemistry. The voided 6-inch diameter pipe section was
adversely affect steam generator chemistry. The voided 6-inch diameter pipe section was


11-feet long. The licensee responded with a procedure change to adequately fill the affected
11-feet long. The licensee responded with a procedure change to adequately fill the affected


piping prior to transferring the suction supply. (NRC Inspection Report 05000346/2005004, June 14, 2005, ADAMS Accession No. ML051660047)
piping prior to transferring the suction supply. (NRC Inspection Report 05000346/2005004, June 14, 2005, ADAMS Accession No. ML051660047)


===Watts Bar Nuclear Plant===
===Watts Bar Nuclear Plant===
The Watts Bar backup safety-related water supply to the AFW system is provided by the
The Watts Bar backup safety-related water supply to the AFW system is provided by the


essential raw cooling water (ERCW) system. On January 13, 2006, the licensee discovered air
essential raw cooling water (ERCW) system. On January 13, 2006, the licensee discovered air


in a 12-inch ERCW pipe that supplies water to a motor-driven AFW pump and a turbine-driven
in a 12-inch ERCW pipe that supplies water to a motor-driven AFW pump and a turbine-driven


AFW pump and in an attached 30-inch pipe. The licensee determined that the air in the 12-inch
AFW pump and in an attached 30-inch pipe. The licensee determined that the air in the 12-inch


pipe was, in part, caused by inadequate filling and venting during work performed in the Cycle 6 refueling outage. The air in the 30-inch discharge pipe and a portion of the 12-inch pipe was
pipe was, in part, caused by inadequate filling and venting during work performed in the Cycle 6 refueling outage. The air in the 30-inch discharge pipe and a portion of the 12-inch pipe was


due to gas coming out of solution. Corrective actions included the establishment of continuous
due to gas coming out of solution. Corrective actions included the establishment of continuous


vent paths for the 30-inch ERCW Train A and B discharge headers and the addition of
vent paths for the 30-inch ERCW Train A and B discharge headers and the addition of
Line 111: Line 114:
ultrasonic equipment for verification of the water level in the 30-inch headers and the 12-inch
ultrasonic equipment for verification of the water level in the 30-inch headers and the 12-inch


header. (Licensee Event Report 2006-001-00, March 14, 2006, ADAMS Accession No.
header. (Licensee Event Report 2006-001-00, March 14, 2006, ADAMS Accession No.


ML060760381)
ML060760381)
Line 118: Line 121:
The backup source of water to the emergency feedwater pumps (the licensees designation for
The backup source of water to the emergency feedwater pumps (the licensees designation for


the AFW pumps) is the service water system. In its inspection report, the NRC reported that
the AFW pumps) is the service water system. In its inspection report, the NRC reported that


the safety-related water supply could become unavailable due to the accumulation of tubercles
the safety-related water supply could become unavailable due to the accumulation of tubercles
Line 124: Line 127:
or other debris and that the flow control valves were not designed to handle relatively unclean
or other debris and that the flow control valves were not designed to handle relatively unclean


service water. (NRC Inspection Report 05000395/2005007, March 10, 2005, ADAMS
service water. (NRC Inspection Report 05000395/2005007, March 10, 2005, ADAMS


Accession No. ML050700044)
Accession No. ML050700044)
Line 133: Line 136:
condensate storage tank is designed to ensure sufficient condensate remains available if this
condensate storage tank is designed to ensure sufficient condensate remains available if this


tank should fail during a design basis earthquake. An NRC inspection team found that the
tank should fail during a design basis earthquake. An NRC inspection team found that the


licensee failed to follow procedural requirements and establish the necessary foreign material
licensee failed to follow procedural requirements and establish the necessary foreign material


exclusion areas. As a result, foreign materials could cause AFW operational problems
exclusion areas. As a result, foreign materials could cause AFW operational problems


following a seismic event. Further, the licensee failed to properly address industry operating
following a seismic event. Further, the licensee failed to properly address industry operating


experience related to foreign materials in AFW water sources. (NRC Inspection Report
experience related to foreign materials in AFW water sources. (NRC Inspection Report


05000361;362/2006009, December 8, 2006, ADAMS Accession No. ML063420342) Kewaunee Nuclear Power Plant
05000361;362/2006009, December 8, 2006, ADAMS Accession No. ML063420342) Kewaunee Nuclear Power Plant
Line 147: Line 150:
The AFW pump shaft seals require a small amount of leakage to maintain adequate cooling
The AFW pump shaft seals require a small amount of leakage to maintain adequate cooling


and sealing. Leakage reduction or loss can cause loss of seal cooling and lubrication with
and sealing. Leakage reduction or loss can cause loss of seal cooling and lubrication with


subsequent seal degradation that may allow air flow into the pump inlet if the inlet pressure is
subsequent seal degradation that may allow air flow into the pump inlet if the inlet pressure is


sub-atmospheric, a condition that may occur following a steam line break. This may cause
sub-atmospheric, a condition that may occur following a steam line break. This may cause


pump damage due to air entrainment. (Licensee Event Report 2005-006-00, May 25, 2005, ADAMS Accession No. ML051530312 and NRC Inspection Report 05000305/2005010,
pump damage due to air entrainment. (Licensee Event Report 2005-006-00, May 25, 2005, ADAMS Accession No. ML051530312 and NRC Inspection Report 05000305/2005010,
October 16, 2005, ADAMS Accession No. ML052290348)
October 16, 2005, ADAMS Accession No. ML052290348)


Line 168: Line 171:
Licensees rely on backup water supplies to AFW systems in response to low probability events, such as seismic and station blackout events, that render normal and preferred water sources
Licensees rely on backup water supplies to AFW systems in response to low probability events, such as seismic and station blackout events, that render normal and preferred water sources


unavailable. The above events indicate that use of backup water sources or other unique and
unavailable. The above events indicate that use of backup water sources or other unique and


potentially overlooked conditions may introduce air or debris that could render AFW inoperable
potentially overlooked conditions may introduce air or debris that could render AFW inoperable
Line 174: Line 177:
and illustrate the importance of having developed a complete understanding of the implications
and illustrate the importance of having developed a complete understanding of the implications


of gas or debris in AFW systems. This is particularly important for operational aspects that are
of gas or debris in AFW systems. This is particularly important for operational aspects that are


not tested, as illustrated by the above events where the likelihood of being in the condition was
not tested, as illustrated by the above events where the likelihood of being in the condition was
Line 183: Line 186:


==CONTACT==
==CONTACT==
This information notice requires no specific action or written response. Please direct any
This information notice requires no specific action or written response. Please direct any


questions about this matter to the technical contact listed below or the appropriate Office of
questions about this matter to the technical contact listed below or the appropriate Office of
Line 190: Line 193:


/RA/
/RA/
                                      Michael J. Case, Director


===Michael J. Case, Director===
Division of Policy and Rulemaking
Division of Policy and Rulemaking


Office of Nuclear Reactor Regulation
===Office of Nuclear Reactor Regulation===


===Technical Contact:===
===Technical Contact:===


===Warren C. Lyon, NRR===
===Warren C. Lyon, NRR===
                    301-415-2897 e-mail: wcl@nrc.gov
        301-415-2897 e-mail: wcl@nrc.gov


Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.


==CONTACT==
==CONTACT==
This information notice requires no specific action or written response. Please direct any
This information notice requires no specific action or written response. Please direct any


questions about this matter to the technical contact listed below or the appropriate Office of
questions about this matter to the technical contact listed below or the appropriate Office of
Line 211: Line 214:


/RA/
/RA/
                                        Michael J. Case, Director


===Michael J. Case, Director===
Division of Policy and Rulemaking
Division of Policy and Rulemaking


Office of Nuclear Reactor Regulation
===Office of Nuclear Reactor Regulation===


===Technical Contact:===
===Technical Contact:===


===Warren C. Lyon, NRR===
===Warren C. Lyon, NRR===
                      301-415-2897 e-mail: wcl@nrc.gov
        301-415-2897 e-mail: wcl@nrc.gov
 
Note:  NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.
 
Distribution:  IN Reading File
 
ADAMS Accession Number: ML071100075 OFFICE
 
SPWB:DSS
 
TECH EDITOR
 
BC:SPWB:DSS
 
DD:DSS
 
D:DSS
 
NAME
 
WLyon
 
LCulp by e-mail
 
GCranston
 
JWermiel
 
TMartin
 
DATE
 
04/23/07
04/27/07
04/23/07
05/10/07
05/10/07 OFFICE
 
PGCB:DPR
 
PGCB:DPR
 
BC:PGCB:DPR
 
D:DPR


Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.
NAME


Distribution: IN Reading File
DBeaulieu


ADAMS Accession Number: ML071100075 OFFICE      SPWB:DSS          TECH EDITOR        BC:SPWB:DSS      DD:DSS        D:DSS
CHawes


NAME        WLyon            LCulp by e-mail    GCranston        JWermiel      TMartin
CJackson


DATE        04/23/07          04/27/07          04/23/07          05/10/07      05/10/07 OFFICE      PGCB:DPR              PGCB:DPR              BC:PGCB:DPR        D:DPR
MCase


NAME        DBeaulieu              CHawes                CJackson          MCase
DATE


DATE        05/08/07               05/10/07               05/11/07           05/13/07 OFFICIAL RECORD COPY}}
05/08/07
05/10/07
05/11/07
05/13/07 OFFICIAL RECORD COPY}}


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

Latest revision as of 01:29, 15 January 2025

Operating Experience Regarding Entrainment of Gas or Debris Into Auxiliary Feedwater Systems
ML071100075
Person / Time
Issue date: 05/13/2007
From: Michael Case
NRC/NRR/ADRA/DPR
To:
References
IN-07-018
Download: ML071100075 (4)
v • d • e


UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, DC 20555-0001

May 13, 2007

NRC INFORMATION NOTICE 2007-18:

OPERATING EXPERIENCE REGARDING

ENTRAINMENT OF GAS OR DEBRIS INTO

AUXILIARY FEEDWATER SYSTEMS

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 operating experience regarding possible entrainment of air or debris into

auxiliary feedwater (AFW) systems, potentially affecting the operability of these systems. The

NRC expects that recipients will review the information for applicability to their facilities and

consider actions, as appropriate, to avoid similar problems. Suggestions contained in this IN

are not NRC requirements; therefore, no specific action or written response is required.

DESCRIPTION OF CIRCUMSTANCES

Several events have occurred at nuclear power facilities involving possible entrainment of gas

or debris into AFW systems. Air or debris entrained in AFW systems can impact the capability

of the AFW pumps to perform their specified safety functions. Several recent events are

discussed below:

McGuire Nuclear Station

A design deficiency resulted in gas coming out of solution and collecting in the nuclear service

water system where the Train A AFW assured suction was located. When this was recognized, the licensee decided to use operator manual alignments to preclude gas entrainment into the

AFW pumps when alignment was to the standby nuclear service water pond. NRC inspectors

identified that the licensee was crediting non-seismic pipe for no less than 30 minutes after a

seismic event to allow time to perform the AFW valve lineup. Consequently, there was not

reasonable assurance that the non-seismic pipe would be available to support supplying water

to the AFW pumps. (NRC Integrated Inspection Report 05000369/2004005 and

05000370/2004005, October 8, 2004, Agencywide Documents Access and Management

System (ADAMS) Accession No. ML042860339)

The licensee subsequently initiated a piping modification and test program to address the issue.

(Duke Energy letters to NRC dated April 25, 2006, and September 7, 2006, ADAMS Accession

Nos. ML061230672 and ML062640070, respectively)

Davis-Besse Nuclear Power Station

NRC inspectors identified an inadequate procedure that could have resulted in sufficient air in

an AFW pump suction to make it inoperable. The procedure addressed the realignment of the

AFW pumps suction from the condensate storage tank to the service water system using a

pipe that was normally voided to preclude potential leakage through a closed valve that could

adversely affect steam generator chemistry. The voided 6-inch diameter pipe section was

11-feet long. The licensee responded with a procedure change to adequately fill the affected

piping prior to transferring the suction supply. (NRC Inspection Report 05000346/2005004, June 14, 2005, ADAMS Accession No. ML051660047)

Watts Bar Nuclear Plant

The Watts Bar backup safety-related water supply to the AFW system is provided by the

essential raw cooling water (ERCW) system. On January 13, 2006, the licensee discovered air

in a 12-inch ERCW pipe that supplies water to a motor-driven AFW pump and a turbine-driven

AFW pump and in an attached 30-inch pipe. The licensee determined that the air in the 12-inch

pipe was, in part, caused by inadequate filling and venting during work performed in the Cycle 6 refueling outage. The air in the 30-inch discharge pipe and a portion of the 12-inch pipe was

due to gas coming out of solution. Corrective actions included the establishment of continuous

vent paths for the 30-inch ERCW Train A and B discharge headers and the addition of

ultrasonic equipment for verification of the water level in the 30-inch headers and the 12-inch

header. (Licensee Event Report 2006-001-00, March 14, 2006, ADAMS Accession No.

ML060760381)

Virgil C. Summer Nuclear Station

The backup source of water to the emergency feedwater pumps (the licensees designation for

the AFW pumps) is the service water system. In its inspection report, the NRC reported that

the safety-related water supply could become unavailable due to the accumulation of tubercles

or other debris and that the flow control valves were not designed to handle relatively unclean

service water. (NRC Inspection Report 05000395/2005007, March 10, 2005, ADAMS

Accession No. ML050700044)

San Onofre Nuclear Generating Station

The seismically qualified Enclosure Building surrounding the non-seismically qualified

condensate storage tank is designed to ensure sufficient condensate remains available if this

tank should fail during a design basis earthquake. An NRC inspection team found that the

licensee failed to follow procedural requirements and establish the necessary foreign material

exclusion areas. As a result, foreign materials could cause AFW operational problems

following a seismic event. Further, the licensee failed to properly address industry operating

experience related to foreign materials in AFW water sources. (NRC Inspection Report

05000361;362/2006009, December 8, 2006, ADAMS Accession No. ML063420342) Kewaunee Nuclear Power Plant

The AFW pump shaft seals require a small amount of leakage to maintain adequate cooling

and sealing. Leakage reduction or loss can cause loss of seal cooling and lubrication with

subsequent seal degradation that may allow air flow into the pump inlet if the inlet pressure is

sub-atmospheric, a condition that may occur following a steam line break. This may cause

pump damage due to air entrainment. (Licensee Event Report 2005-006-00, May 25, 2005, ADAMS Accession No. ML051530312 and NRC Inspection Report 05000305/2005010,

October 16, 2005, ADAMS Accession No. ML052290348)

BACKGROUND

Some of the issues of gas entrainment on AFW systems are similar to the concerns discussed

in NRC IN 2006-21, Operating Experience Regarding Entrainment of Air into Emergency Core

Cooling and Containment Spray Systems, dated September 21, 2006, ADAMS Accession No.

ML062570468.

DISCUSSION

Licensees rely on backup water supplies to AFW systems in response to low probability events, such as seismic and station blackout events, that render normal and preferred water sources

unavailable. The above events indicate that use of backup water sources or other unique and

potentially overlooked conditions may introduce air or debris that could render AFW inoperable

and illustrate the importance of having developed a complete understanding of the implications

of gas or debris in AFW systems. This is particularly important for operational aspects that are

not tested, as illustrated by the above events where the likelihood of being in the condition was

small, but the condition impacted defense-in-depth and resulted in a failure to comply with the

plant design basis.

CONTACT

This information notice requires no specific action or written response. Please direct any

questions about this matter to the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

/RA/

Michael J. Case, Director

Division of Policy and Rulemaking

Office of Nuclear Reactor Regulation

Technical Contact:

Warren C. Lyon, NRR

301-415-2897 e-mail: wcl@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.

CONTACT

This information notice requires no specific action or written response. Please direct any

questions about this matter to the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

/RA/

Michael J. Case, Director

Division of Policy and Rulemaking

Office of Nuclear Reactor Regulation

Technical Contact:

Warren C. Lyon, NRR

301-415-2897 e-mail: wcl@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.

Distribution: IN Reading File

ADAMS Accession Number: ML071100075 OFFICE

SPWB:DSS

TECH EDITOR

BC:SPWB:DSS

DD:DSS

D:DSS

NAME

WLyon

LCulp by e-mail

GCranston

JWermiel

TMartin

DATE

04/23/07

04/27/07

04/23/07

05/10/07

05/10/07 OFFICE

PGCB:DPR

PGCB:DPR

BC:PGCB:DPR

D:DPR

NAME

DBeaulieu

CHawes

CJackson

MCase

DATE

05/08/07

05/10/07

05/11/07

05/13/07 OFFICIAL RECORD COPY


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