Information Notice 1996-10, Potential Blockage by Debris of Safety System Piping Which Is Not Used During Normal Operation or Tested During Surveillances
14
UNITED STATES
NUCLEAR REGULATORY COMMISSION
- '
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
February 13, 1996
POTENTIAL BLOCKAGE BY DEBRIS OF SAFETY SYSTEM
PIPING WHICH IS NOT USED DURING NORMAL
OPERATION OR TESTED DURING SURVEILLANCES
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the potential for the blockage, by debris, of
safety system piping in boiling-water reactors (BWRs) or pressurized-water
reactors (PWRs).
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.
The source of the information--contained in this information notice was the
incident reporting system (IRS) of the Organization for Economic Cooperation
and Development Nuclear Energy Agency.
The Spanish regulatory staff
authorized public dissemination of this information.
Description of Circumstances
During refueling outages at PWRs in Spain, containment sumps are usually
inspected visually to ensure that the sump, screens, and suction inlet pipes
in the emergency core cooling system (ECCS) are free of debris, and that the
sumps screens are not corroding.
In November 1993, the licensee of a PWR in Spain inspected its containment
sumps during outage surveillance. The licensee did not consider it unusual
for the sumps to contain water because there is some leakage to the sump
during functional testing of a three-way valve which connects the ECCS borated
tanks with the containment sumps.
However, in this case, the individual
inspecting the sump believed that the water was unusually dirty, so he had it
siphoned off. Once the water had been removed, he could see that three of the
four sumps had debris in the bottom below the suction pipe for the ECCS. A
closer examination of the ECCS suction lines revealed that two of the four
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February 13, 1996 ECCS lines taking suction from the sumps were partially blocked by debris.
One of the two partially blocked lines had almost half the flow area of the
pipe blocked off; the other was blocked less.
It is believed that the debris
had been there since the plant was commissioned, and that this event demon- strated a significant failure of the surveillance program.
Figure 1 shows a
cross-sectional view of the sump and indicates where the debris was found.
Upon further review, the Spanish regulators noted that there are no technical
specification requirements to inspect the piping from the containment sumps to
the ECCS to ensure that it is clear of any obstruction by debris.
It was also
noted that many sections of piping on safety systems in both PWRs and BWRs are
only called upon to function during accident conditions, and are not used
during normal operation or tested during functional surveillance tests.
Confidence in the operability of these pipes was based on the fact that they
had not been used since they were tested before plant startup.
In response to the event, Spanish regulators issued a generic letter which
asked their licensees to take four actions.
First, they were requested to
establish administrative controls, including a locking device, on the sump
hatch and on any other removable sump parts (PWRs only).
Second, they were
requested to inspect the containment sump and the piping between the sump and
the first ECCS valve which separates the part of the system that is
functionally tested from the part that is not (PWRs only).
Third, they were
requested to inspect the sump every refueling outage.
If more than 1 kilogram
of debris was found in the sump, licensees were then requested to reinspect
the piping between the sump and the functionally tested portion of the ECCS
(PWRs only). And fourth, licensees were requested to identify piping segments
of safety systems through which flow does not occur, either during normal
operation or during surveillance testing, and to analyze whether there are
reasonable guarantees that no obstruction exists (BWRs and PWRs).
Examples of
the piping segments that would require this analysis are crossover piping from
the essential service cooling system to the auxiliary feedwater system (PWRs),
relief valve discharge piping (PWRs), low-pressure coolant injection suction
piping from the condensate storage tank (BWRs), and crossover connections
between low-pressure coolant injection trains (BWRs).
Discussion
The licensee in this case concluded that the safety significance of this event
was small because the partial blockage of the lines would not prevent the ECCS
from providing sufficient core cooling.
However, it was also noted that some
of the debris could have been entrained in the water flow and could have
detrimental effects on other parts of the system (e.g., pump and valve
components and heat exchangers).
The licensee initial corrective actions
(prior to issuance of the generic letter) included cleaning up the sumps and
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February 13, 1996 suction lines, locking sump hatches, and establishing administrative controls.
These corrective actions address the root cause of the presence of debris in
the sump and suction line.
It has been noted in previous NRC generic communications that debris could
prevent such safety systems as the ECCS from functioning reliably throughout a
design-basis accident. These previous NRC communications have dealt with the
potential for debris to clog the ECCS strainers (operational debris, loss-of- coolant-accident-generated debris, or a combination of both).
The debris
described in this information notice is another example of the potential
fordebris to impair the operation of safety systems. Although the licensee in
this case has determined that the debris found in its sump was insufficient to
prevent the ECCS from performing its safety function, such debris could damage
individual components of the safety system (e.g., pumps), degrade system
performance, or (in combination with the debris generated during a loss-of- coolant accident) could accelerate a loss of net positive suction head for the
ECCS pumps.
Related Generic Communications
NRC Bulletin 93-02 and Supplement 1:
"Debris Plugging of Emergency Core
Cooling Suction Strainers," dated May, 11,
1993, and February 18, 1994.
NRC Information Notice 92-85: "Potential Failures of Emergency Core
Cooling Systems Caused by Foreign Material Blockage," dated
December 23, 1992.
"Partial Plugging of Suppression Pool
Strainers at a Foreign BWR," dated September 30, 1992.
"Debris in Containment Emergency Sumps
and Incorrect Screen Configurations," dated November 21, 1989.
"Pump Wear and Foreign Objects in Plant
Piping Systems," dated November 16, 1988.
"Potential for Loss of Post LOCA
Recirculation Capability Due to Insulation Debris Blockage," dated
May 19, 1988.
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February 13, 1996 This information notice requires no specific
you have any questions about the information
one of the technical contacts listed below.
action or written response.
If
in this notice, please contact
e s .Crut
r
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact:
Eric J. Benner, NRR
(301) 415-1171 Internet:ejbl@nrc.gov
Robert B. Elliott, NRR
(301) 415-1397 Internet:rbe@nrc.gov
Attachments:
1. Figure 1:
Scheme of Containment Sump
2. List of Recently Issued NRC Information Notices
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FIGURE 1. Scheme of containment sump
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Attachment 2
February 13, 1996 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
96-09
96-08
96-07
96-06
96-05
96-04
96-03
Damage in Foreign Steam
Generator Internals
Thermally Induced Pres- sure Locking of a High
Pressure Coolant Injec- tion Gate Valve
Slow Five Percent Scram
Insertion Times Caused
By Viton Diaphragms in
Scram Solenoid Pilot
Valves
Design and Testing
Deficiencies of Tornado
Dampers at Nuclear Power
Plants
Partial Bypass of Shutdown
Cooling Flow from the
Reactor Vessel
Incident Reporting Require- ments for Radiography
Licensees
Main Steam Safety Valve
Setpoint Variation as a
Result of Thermal Effects
02/12/96
02/05/96
01/26/96
01/25/96
01/18/96
01/10/96
01/05/96
All holders of OLs or CPs
for pressurized water
reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for boiling water reactors
All holders of OLs or CPs
for nuclear power reactors
All holders of OLs or CPs
for boiling water reactors
All radiography licensees
and manufacturers of radio- graphy equipment
All holders of OLs or CPs
for nuclear power reactors
OL = Operating License
CP = Construction Permit
<I
February 13, 1996
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact:
Eric J. Benner, NRR
(301) 415-1171 Internet:ejbl@nrc.gov
Robert B. Elliott, NRR
(301) 415-1397 Internet:rbe@nrc.gov
Attachments:
1. Figure 1:
Scheme of Containment Sump
2. List of Recently Issued NRC Information Notices
Reviewed and concurred on by tech editor 12/18/95 IN faxed to Jose Villadoniga of Consejo De Seguiridad on
IN concurred on by Bill Upshaw of International Programs
Reviewed by Mike Cullingford on 2/6/96.
- See previous concurrence
DOCUMENT NAME: 96-1O.IN
2/6/96.
on 1/4/95 To receive a copy of this document, Indicate In the box: AC" - Copy without enclosures 'E' - Copy with enclosures "N' - No copy
OFFICE
TECH CONTS I
SCSB:DSSA I
PECB:DRPM
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IP
NAME
EBenner*
CBerlinger*
AChaffee*
D4 d
DATE
01/03/96
01/16/96
01/18/96
02/ /96
OFFICIAL RECORD COPY
IN 96-xx
February xx, 1996 potential for foreign material to impact operation of safety systems.
Although the licensee in this case has determined that the debris found in
their sump was insufficient to prevent the ECCS from performing its safety
function, such this debris could damage individual components of the safety
system (e.g., pumps), degrade system performance or, in combination with the
debris generated during a loss-of-coolant accident, could accelerate a loss of
net positive suction head for the ECCS pumps.
Related Generic Communications
NRC Bulletin 93-02 and Supplement 1:
'Debris Plugging of Emergency Core
Cooling Suction Strainers," dated May, 11,
1993, and February 18, 1994.
NRC Information Notice
Cooling Systems Caused
December 23, 1992.
NRC Information Notice
Strainers at a Foreign
92-85:
"Potential Failures of Emergency Core
by Foreign Material Blockage," dated
92-71:
'Partial Plugging of Suppression Pool
BWR," dated September 30, 1992.
"Debris in Containment Emergency Sumps
and Incorrect Screen Configurations," dated November 21, 1989.
"Pump Wear and Foreign Objects in Plant
Piping Systems," dated November 16, 1988.
"Potential for Loss of Post LOCA
Recirculation Capability Due to Insulation Debris Blockage," dated
May 19, 1988.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact:
Eric J. Benner, NRR
(301) 415-1171 Internet: EJBINRC.GOV
Robert B. Elliot, NRR
(301) 415-1397 Internet: RBE@NRC.GOV
Attachments:
1. Figure 1: Scheme of Containment Sump
2. List of Recently Issued NRC Information Notices
Reviewed and concurred on by tech editor 12/18/95 IN concurred on by Bill Upshaw of International Programs on 1/4/95
- See previous concurrence
DOCUMENT NAME: G:\\EJB1\\FOREIGN.IN
To receive a copy of this document, Indicate hi the box: 'C' . Copy without enclosures 'E' = Copy with enclosures 'N'
- No copy
OFFICE
PECB:DRPM I C SC/PECB:DRPM I N C SCSB:DSSA I E C/PECB:DRPM
C DRPM
I
NEBenner*
EGoodwin*
CBerlinger*
IAChaffee*
DCrutchfield
DATE
1/3/96
1/4/96
01/16/96
01/18/96
01/ /96 OFFICIAL RECORD COPY
hID PA..
A
Nr96-xx
January xx, 1996 example of the potential for foreign material to impact operation of safety
systems. Although the licensee in this case has determined that the debris
found in their sump was insufficient to prevent the ECCS from performing its
safety function, it is important to realize that this debris could damage
individual components of the safety system (e.g., pumps), degrade system
performance or, in combination with the debris generated during a loss-of- coolant accident, could accelerate a loss of net positive suction head for the
ECCS pumps.
Related Generic Communications
'Potential Failures of Emergency Core
Cooling Systems Caused by Foreign Material Blockage"
NRC Bulletin 93-02 and Supplement 1:
"Debris Plugging of Emergency Core
Cooling Suction Strainers"
"Partial Plugging of Suppression Pool
Strainers at a Foreign BWRN
"Debris in Containment Emergency Sumps
and Incorrect Screen Configurations"
"Pump Wear and Foreign Objects in Plant
Piping Systems"
"Potential for Loss of Post LOCA
Recirculation Capability Due to Insulation Debris Blockage"
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact:
Eric J. Benner, NRR
(301) 415-1171 Internet: EJBINRC.GOV
Robert B. Elliot, NRR
(301) 415-1397 Internet: RBE@NRC.GOV
Reviewed and concurred on by tech editor 12/18/95 IN concurred on by Bill Upshaw of International Programs on 1/4/95
- See previous concurrence
DOCUMENT NAME: G:\\EJB1\\FOREIGN.IN
To receive a copy of this document. Indicate In the box: wC" - Copy without enclosures 'E' - Copy with enclosures N -
No copy
OFFICE
IPECB:DRPM I C SC/PECB:DRPM I N C/SCSB:DSSA I E
C/PECE
C DRPM
I
NAME
IEBenner*
IEGoodwin*
CBerlinger*
ACha
%DCrutchfield
DATE
1/3/96
1/4/96
01/16/96
01/f /96 J-%
01/ /96
OFFICiAL RECORD COPY
December xx, 1995
example of the potential for foreign material to impact operation of safety
systems. Although the licensee in this case has determined that the debris
found in their sump was insufficient to prevent the ECCS from performing its
safety function, it is important to realize that this debris could damage
individual components of the safety system (e.g., pumps), degrade system
performance or, in combination with the debris generated during a loss-of- coolant accident, could accelerate a loss of net positive suction head for the
ECCS pumps.
Related Generic Communications
"Potential Failures of Emergency Core
Cooling Systems Caused by Foreign Material Blockage"
NRC Bulletin 93-02 and Suppleme
Cooling Suction Strainers'
Strainers at a Foreign BWRE
"Debris Plugging of Emergency Core
"Partial Plugging of Suppression Pool
"Debris in Containment Emergency Sumps
and Incorrect Screen Configurations"
Piping Systems"
"Pump Wear and Foreign Objects in Plant
"Potential for Loss of Post LOCA
Recirculation Capability Due to Insulation Debris Blockage"
This
you
one
- information notice requires no specific action or written response.
If
have any questions about the information in this notice, please contact
of the technical contacts listed below.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
nical contact:
Eric J. Benner, NRR
(301) 415-1171
2/s77 /B~77A.
E-mail: EJB1@NRC.GOV
Tech
Robert B. Elliot, NRR
(301) 415-1397 E-mail: RBE@NRC.GOV
Reviewed and concurred on by tech editor 12/18/95 IN concurred on by Bill Upshaw of International Programs on 1/4/95
- See previous concurrence
DOCUMENT NAME: G:\\EJB1\\FOREIGN.IN
Tn rvaei
a *nnv
nf Mthis
documnnt. Indlenta In the box: 'C'
= Coov without enclosures 'E'
- Coov with enclosures 'N'
- No copy
OFFICE
Contacts
.C SC/PECB:DRPM I N
CC/SCSB:gA
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C/PECB:DRPM I lC/RPM
I
'NAME
EEGoodwin*
}CB[I
1AChaffee
DCrutchfield
DATE
1/3/96 1/ /96 1/4/96
96 l
017e/ /96
01/
/96
OFFICIAL RECORD COPY
\\t
95-xx
December xx, 1995 example of the potential for foreign material to impact operation of safety
systems. Although the licensee in this case has determined that the debris
found in their sump was insufficient to prevent the ECCS from performing its
safety function, it is important to realize that this debris could damage
individual components of the safety system (e.g., pumps), degrade system
performance or, in combination with the debris generated during a loss-of- coolant accident, could accelerate a loss of net positive suction head for the
ECCS pumps.
Related Generic Communications
"Potential Failures of Emergency Core
Cooling Systems Caused by Foreign Material Blockage"
NRC Bulletin 93-02 and Supplement 1:
'Debris Plugging of Emergency Core
Cooling Suction Strainers"
"Partial Plugging of Suppression Pool
Strainers at a Foreign BWR"
"Debris in Containment Emergency Sumps
and Incorrect Screen Configurations"
NRC Information Notice 88-87: 'Pump Wear and Foreign Objects in Plant
Piping Systems"
NRC Information Notice 88-28: *Potential for Loss of Post LOCA
Recirculation Capability Due to Insulation Debris Blockage"
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contact: Eric J. Benner, NRR
(301) 415-1171 E-mail: EJBINRC.GOV
Robert B. Elliot, NRR
(301) 415-1397 E-mail: RBE@NRC.GOV
Reviewed and concurred on by tech editor 12j18/95 Use of Spanish documentation for IN approved by Bill Upshaw of International
Programs on 1/3/95 DOCUMENT NAME: G:\\EJB1\\FOREIGN.IN
To receive a copy of this document, indicate In
the box: "C"
- = Copy without enclosures 'E" =Copy
with enclosures 'N" - No copy
OFFICE
PECB:DRPM
SC/PECB:DRPM I
C/SCSB:DSSA I -C/PECB:DRPM
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EBenner ith5 IEGoodwink,.
ICBerlinger
AChaffee
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DATE
01/1 /96 U
01/
/96
101/
/96
01/
/96
01/
/96 OFFICIAL RECORD COPY