Information Notice 2020-04, Operating Experience Regarding Failure of Buried Fire Protection Main Yard Piping: Difference between revisions

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{{#Wiki_filter:UNITED STATES
{{#Wiki_filter:ML20223A333 UNITED STATES


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


WASHINGTON, DC 20555-0001 December 17, 2020
WASHINGTON, DC 20555-0001  
NRC INFORMATION NOTICE 2020-04:                         OPERATING EXPERIENCE RELATED TO FAILURE
 
December 17, 2020  
 
NRC INFORMATION NOTICE 2020-04:  
OPERATING EXPERIENCE RELATED TO FAILURE


OF BURIED FIRE PROTECTION MAIN YARD PIPING
OF BURIED FIRE PROTECTION MAIN YARD PIPING
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manufacturing license under 10 CFR Part 52, Licenses, certifications, and approvals for nuclear
manufacturing license under 10 CFR Part 52, Licenses, certifications, and approvals for nuclear


power plants. All applicants for a standard design certification, including such applicants after
power plants. All applicants for a standard design certification, including such applicants after


initial issuance of a design certification rule.
initial issuance of a design certification rule.
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addressees of operating experience involving the loss of function of buried cast iron fire water main
addressees of operating experience involving the loss of function of buried cast iron fire water main


yard piping due to multiple factors, including graphitic corrosion 1, overpressuration, low-cycle
yard piping due to multiple factors, including graphitic corrosion1, overpressuration, low-cycle


fatigue, and surface loads. Some of the operating experience has not been captured in industry- wide operating experience reports. The NRC expects that recipients will review the information for
fatigue, and surface loads. Some of the operating experience has not been captured in industry- wide operating experience reports. The NRC expects that recipients will review the information for


applicability to their facilities and consider actions, as appropriate, to avoid similar problems. INs
applicability to their facilities and consider actions, as appropriate, to avoid similar problems. INs


may not impose new requirements, and nothing in this IN should be interpreted to require specific
may not impose new requirements, and nothing in this IN should be interpreted to require specific
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minimum criteria for materials, design, fabrication, testing, inspection, and certification of all
minimum criteria for materials, design, fabrication, testing, inspection, and certification of all


structures, systems, and components important to safety. In 10 CFR 50.48, Fire protection, the
structures, systems, and components important to safety. In 10 CFR 50.48, Fire protection, the


NRC requires that each operating nuclear power plant has a fire protection plan that satisfies 10
NRC requires that each operating nuclear power plant has a fire protection plan that satisfies 10  
CFR Part 50, Appendix A, General Design Criterion 3, Fire protection. General Design Criterion 3 states that fire detection and fighting systems of appropriate capacity and capability be provided
CFR Part 50, Appendix A, General Design Criterion 3, Fire protection. General Design Criterion 3 states that fire detection and fighting systems of appropriate capacity and capability be provided


and designed to minimize the adverse effect of fires on structures, systems, and components that
and designed to minimize the adverse effect of fires on structures, systems, and components that


1         Graphitic corrosion is a form of galvanic corrosion that occurs in wet or moist environments; it is also known as
1 Graphitic corrosion is a form of galvanic corrosion that occurs in wet or moist environments; it is also known as


selective leaching.
selective leaching. are important to safety, and that firefighting systems be designed to assure that their rupture or
 
ML20223A333 are important to safety, and that firefighting systems be designed to assure that their rupture or


inadvertent operation does not significantly impair the safety capability of these structures, systems, and components. Subpart H of 10 CFR Part 70 establishes the NRC's fire protection program
inadvertent operation does not significantly impair the safety capability of these structures, systems, and components. Subpart H of 10 CFR Part 70 establishes the NRC's fire protection program


requirements for fuel cycle facilities. Some specific source material licensees have similar
requirements for fuel cycle facilities. Some specific source material licensees have similar


commitments in their NRC license. In 10 CFR 70.61 of Subpart H, the NRC requires each
commitments in their NRC license. In 10 CFR 70.61 of Subpart H, the NRC requires each


applicant or licensee to limit the risk of each credible high-consequence event. Several fuel cycle
applicant or licensee to limit the risk of each credible high-consequence event. Several fuel cycle


facilities, including some specific source material facilities, have fire suppression systems credited
facilities, including some specific source material facilities, have fire suppression systems credited


as mitigative controls needed to meet these performance requirements. The purpose of these
as mitigative controls needed to meet these performance requirements. The purpose of these


programs is to safeguard any nuclear material on site and protect the public from radioactive
programs is to safeguard any nuclear material on site and protect the public from radioactive
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The fire protection main yard piping is typically maintained at required operating pressures using
The fire protection main yard piping is typically maintained at required operating pressures using


pressure maintenance components, such as a jockey pump. The smaller pump accommodates
pressure maintenance components, such as a jockey pump. The smaller pump accommodates


nominal system leakage from either non-pressure-boundary sources (e.g., packing, gaskets) or
nominal system leakage from either non-pressure-boundary sources (e.g., packing, gaskets) or


pressure boundary sources (e.g., through-wall defect). The jockey pump prevents cycling of the
pressure boundary sources (e.g., through-wall defect). The jockey pump prevents cycling of the


larger main fire pumps, which start on decreasing header pressure or another anticipatory signal.
larger main fire pumps, which start on decreasing header pressure or another anticipatory signal.
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The water supply of any fire protection system is often considered the most critical component of
The water supply of any fire protection system is often considered the most critical component of


the system. The function of underground or buried fire water main yard piping is to move the water
the system. The function of underground or buried fire water main yard piping is to move the water


from its source to its final point of use. This piping must be extremely reliable, capable, and able
from its source to its final point of use. This piping must be extremely reliable, capable, and able


automatically to distribute enough water directly to a fire to extinguish it or to hold it in check until
automatically to distribute enough water directly to a fire to extinguish it or to hold it in check until
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Internal corrosion of ferrous piping materials (cast iron, ductile iron, and carbon steel) can be a
Internal corrosion of ferrous piping materials (cast iron, ductile iron, and carbon steel) can be a


problem for fire water supply systems. Microbiological action is the most common mechanism
problem for fire water supply systems. Microbiological action is the most common mechanism


causing the internal corrosion process to occur. Living microorganisms such as sulfate-, iron-, and
causing the internal corrosion process to occur. Living microorganisms such as sulfate-, iron-, and


manganese-reducing bacteria cause this form of corrosion. These bacteria can develop in the
manganese-reducing bacteria cause this form of corrosion. These bacteria can develop in the


piping environment with or without oxygen. They can be concentrated and accelerate internal
piping environment with or without oxygen. They can be concentrated and accelerate internal


corrosion, causing either pitting (creating pinhole leaks) or mineral deposits that introduce
corrosion, causing either pitting (creating pinhole leaks) or mineral deposits that introduce


increased pressure loss due to the turbulence of the water flow. This is referred to as
increased pressure loss due to the turbulence of the water flow. This is referred to as


microbiologically induced corrosion. External corrosion of buried fire water main yard piping has no
microbiologically induced corrosion. External corrosion of buried fire water main yard piping has no


adverse effect on the flow of water through the piping system, up to the point of pipe failure.
adverse effect on the flow of water through the piping system, up to the point of pipe failure.
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corrosivity, and stray electric ground currents.
corrosivity, and stray electric ground currents.


Actions to mitigate external corrosion typically include properly designed and applied coatings;
Actions to mitigate external corrosion typically include properly designed and applied coatings;  
appropriately specified and installed backfill; and properly designed, tested, and maintained
appropriately specified and installed backfill; and properly designed, tested, and maintained


cathodic protections systems. Coatings, however, have a finite effective life, and coating
cathodic protections systems. Coatings, however, have a finite effective life, and coating


degradation has been identified in some instances of external corrosion. One method of minimizing
degradation has been identified in some instances of external corrosion. One method of minimizing


both internal and external corrosion of buried fire water main yard piping is to use nonferrous piping
both internal and external corrosion of buried fire water main yard piping is to use nonferrous piping


materials such as HDPE. Some plants have replaced cast iron piping with HDPE piping because it
materials such as HDPE.   Some plants have replaced cast iron piping with HDPE piping because it


is immune to service water corrosion and highly resistant to fouling.
is immune to service water corrosion and highly resistant to fouling.
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Some plants have replaced cast iron piping with HDPE piping because it is immune to service water
Some plants have replaced cast iron piping with HDPE piping because it is immune to service water


corrosion and highly resistant to fouling. However, HDPE piping is a relatively new material
corrosion and highly resistant to fouling. However, HDPE piping is a relatively new material


compared to cast iron piping, and therefore long-term service-life data does not exist in significant
compared to cast iron piping, and therefore long-term service-life data does not exist in significant


quantities. The NRC has approved the replacement of steel piping with HDPE piping in American
quantities. The NRC has approved the replacement of steel piping with HDPE piping in American


Society of Mechanical Engineers Class 3 safety-related nuclear service water system piping associated with the essential service water system at Callaway Plant (ADAMS Accession No.
Society of Mechanical Engineers Class 3 safety-related nuclear service water system piping associated with the essential service water system at Callaway Plant (ADAMS Accession No.
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ML083100288), the emergency diesel generator jacket water coolers at Catawba Nuclear Station
ML083100288), the emergency diesel generator jacket water coolers at Catawba Nuclear Station


(Catawba) (ADAMS Accession No. ML091240156), and the plant service water at Hatch, Unit 2 (ADAMS Accession No. ML15337A414). In addition, Catawba has installed aboveground HDPE for
(Catawba) (ADAMS Accession No. ML091240156), and the plant service water at Hatch, Unit 2 (ADAMS Accession No. ML15337A414). In addition, Catawba has installed aboveground HDPE for


nonsafety-related applications. Nonsafety-related use is not part of the NRC approval.
nonsafety-related applications. Nonsafety-related use is not part of the NRC approval.


Monitoring jockey pump run times and fire water storage tank levels for adverse trends may help to
Monitoring jockey pump run times and fire water storage tank levels for adverse trends may help to


detect leaks that could further degrade piping. Excessive jockey pump cycling or a pump that is
detect leaks that could further degrade piping. Excessive jockey pump cycling or a pump that is


continuously running may be indicative of a leak that can erode the supporting soil, resulting in the
continuously running may be indicative of a leak that can erode the supporting soil, resulting in the


cast iron piping being unsupported and subject to tensile stress. These conditions can result in
cast iron piping being unsupported and subject to tensile stress. These conditions can result in


catastrophic failure of the fire main.
catastrophic failure of the fire main.
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contributor for U.S. nuclear power plants and may be a significant contributor to a plants total core
contributor for U.S. nuclear power plants and may be a significant contributor to a plants total core


damage frequency. 2 This IN gives examples in which failures of the buried fire water system main
damage frequency.2 This IN gives examples in which failures of the buried fire water system main


yard piping involved degradation from selective leaching (graphitic corrosion), overpressure, cyclic
yard piping involved degradation from selective leaching (graphitic corrosion), overpressure, cyclic


fatigue, and surface loads. Degradation of buried fire water main yard piping could impair the
fatigue, and surface loads. Degradation of buried fire water main yard piping could impair the


operation of the fire water suppression system and thus impact the overall risk at the plant.
operation of the fire water suppression system and thus impact the overall risk at the plant.
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Cast iron piping is susceptible to the loss of material caused by selective leaching, and it is prone to
Cast iron piping is susceptible to the loss of material caused by selective leaching, and it is prone to


sudden ruptures because of its brittle nature. Multiple failures have occurred when pressure
sudden ruptures because of its brittle nature. Multiple failures have occurred when pressure


transients from main fire pump starts caused significant cracking in the cast iron piping. These
transients from main fire pump starts caused significant cracking in the cast iron piping. These


ruptures have mostly occurred during periodic pump testing and indicate an increased likelihood of
ruptures have mostly occurred during periodic pump testing and indicate an increased likelihood of


failures during an actual demand on the fire protection system. Taking steps to minimize pressure
failures during an actual demand on the fire protection system. Taking steps to minimize pressure


transients during periodic testing may mask potential piping degradation.
transients during periodic testing may mask potential piping degradation.
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Leakage from the fire protection water system can be assessed by monitoring pressure
Leakage from the fire protection water system can be assessed by monitoring pressure


maintenance during component activity (e.g., jockey pump run times). However, non- pressure-boundary leakage cannot be distinguished readily from through-wall degradation, and the
maintenance during component activity (e.g., jockey pump run times). However, non- pressure-boundary leakage cannot be distinguished readily from through-wall degradation, and the


ability to find leakage locations in buried piping will depend on the leak rate and soil drainage
ability to find leakage locations in buried piping will depend on the leak rate and soil drainage


characteristics. In addition, long-term non-pressure-boundary leakage may contribute to higher soil
characteristics. In addition, long-term non-pressure-boundary leakage may contribute to higher soil


corrosivity, resulting in more aggressive degradation of the piping. The examples discussed in this
corrosivity, resulting in more aggressive degradation of the piping. The examples discussed in this


IN illustrate the importance of an effective fire water system aging management program and
IN illustrate the importance of an effective fire water system aging management program and
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operating nuclear power plant sites.
operating nuclear power plant sites.


Buried fire water piping systems are built to withstand high levels of pressure. However, the sudden
Buried fire water piping systems are built to withstand high levels of pressure. However, the sudden


starting and stopping of flow caused by such components as pumps or hydrants can trigger a
starting and stopping of flow caused by such components as pumps or hydrants can trigger a


sudden and even dangerous increase in pressure that those systems cannot handle. Buried fire
sudden and even dangerous increase in pressure that those systems cannot handle. Buried fire


water piping is vulnerable to cracking from applied loads, such as pressure surges or other dynamic
water piping is vulnerable to cracking from applied loads, such as pressure surges or other dynamic
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loading.
loading.


2       These include the NRC technical opinion paper Fire PRA Maturity and Realism: A Technical Evaluation, issued January 2016 (Agencywide Documents Access and Management System (ADAMS) Accession
2 These include the NRC technical opinion paper Fire PRA Maturity and Realism: A Technical Evaluation, issued January 2016 (Agencywide Documents Access and Management System (ADAMS) Accession


No. ML16022A266), and various detailed plant fire risk analyses related to license amendment requests for the
No. ML16022A266), and various detailed plant fire risk analyses related to license amendment requests for the
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Extended Completion TimesRITSTF Initiative 4b. Nothing in this IN should be interpreted to require specific action; however, enhancements used at
Extended Completion TimesRITSTF Initiative 4b. Nothing in this IN should be interpreted to require specific action; however, enhancements used at


other sites include 1) replacing buried piping with high-density polyethylene (HDPE) piping;
other sites include 1) replacing buried piping with high-density polyethylene (HDPE) piping;  
2) incorporating current National Fire Protection Association (NFPA) code and standard
2) incorporating current National Fire Protection Association (NFPA) code and standard


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Operating experience has indicated that multiple failures of the buried cast iron fire water main yard
Operating experience has indicated that multiple failures of the buried cast iron fire water main yard


piping have occurred due to aging effects, including graphitic corrosion (i.e., selective leaching),
piping have occurred due to aging effects, including graphitic corrosion (i.e., selective leaching),  
corrosion buildup, low-cyclic fatigue, and general wall thinning or localized loss of material.
corrosion buildup, low-cyclic fatigue, and general wall thinning or localized loss of material.


Degradation can occur internally or externally to the pipe, or both. Degradation may develop due to
Degradation can occur internally or externally to the pipe, or both. Degradation may develop due to


environmental conditions, or it may be initiated as a result of deficiencies in system design, installation, or maintenance. Licensees can detect only such flow blockage as fouling from silt or
environmental conditions, or it may be initiated as a result of deficiencies in system design, installation, or maintenance. Licensees can detect only such flow blockage as fouling from silt or


sediment, internal coating failures that block flow, or internal tuberculation (i.e., small mounds of
sediment, internal coating failures that block flow, or internal tuberculation (i.e., small mounds of


corrosion products on the inside of the pipe). Internal degradation due to corrosion, selective
corrosion products on the inside of the pipe). Internal degradation due to corrosion, selective


leaching, or cracking cannot be detected by NFPA periodic testing. Below are descriptions of
leaching, or cracking cannot be detected by NFPA periodic testing. Below are descriptions of


recent or recently available operating experience concerning failures of buried fire water main yard
recent or recently available operating experience concerning failures of buried fire water main yard
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piping.
piping.


===Edwin I. Hatch Nuclear Plant, Units 1 and 2===
Edwin I. Hatch Nuclear Plant, Units 1 and 2 On January 25, 2019, a buried 12-inch-diameter fire protection cement-lined cast iron main yard
On January 25, 2019, a buried 12-inch-diameter fire protection cement-lined cast iron main yard


pipe ruptured as a result of fire water sectional valve isolation capability testing. The pressure
pipe ruptured as a result of fire water sectional valve isolation capability testing. The pressure


drops from the rupture led to all three fire water pumps starting on a low-pressure signal. After
drops from the rupture led to all three fire water pumps starting on a low-pressure signal. After


securing the two diesel-driven fire water pumps, the licensee was able to maintain the system
securing the two diesel-driven fire water pumps, the licensee was able to maintain the system
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header pressure with only the motor-driven and jockey pumps running.
header pressure with only the motor-driven and jockey pumps running.


The piping rupture was caused by the start of a fire pump and the subsequent pressure surge. The
The piping rupture was caused by the start of a fire pump and the subsequent pressure surge. The


resulting leak eroded the supporting soil around the pipe, intensifying the bending forces on the
resulting leak eroded the supporting soil around the pipe, intensifying the bending forces on the


pipe, with a catastrophic pipe failure occurring four hours after the initial pressure change. During
pipe, with a catastrophic pipe failure occurring four hours after the initial pressure change. During


the four-hour period between the fire water sectional valve isolation capability testing and the pipe
the four-hour period between the fire water sectional valve isolation capability testing and the pipe
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rupture, the licensee observed that the jockey fire pump was cycling excessively, indicating a loss
rupture, the licensee observed that the jockey fire pump was cycling excessively, indicating a loss


of pressure in the fire protection system from the leak. The licensee later identified a preexisting
of pressure in the fire protection system from the leak. The licensee later identified a preexisting


pipe crack that had propagated over time until the remaining piping material could no longer
pipe crack that had propagated over time until the remaining piping material could no longer
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withstand the stresses and ultimately failed.
withstand the stresses and ultimately failed.


===Surry Power Station, Units 1 and 2===
Surry Power Station, Units 1 and 2 On July 13, 2019, during a periodic test of the electric fire pump, a rupture occurred in a buried
On July 13, 2019, during a periodic test of the electric fire pump, a rupture occurred in a buried


section of 12-inch-diameter fire protection main yard piping. The resulting loss of system pressure
section of 12-inch-diameter fire protection main yard piping. The resulting loss of system pressure


initiated an automatic start of the diesel-driven fire pump. Operators isolated the leak, restoring the
initiated an automatic start of the diesel-driven fire pump. Operators isolated the leak, restoring the


fire protection system function after approximately 18 minutes, but the leak resulted in a loss of an
fire protection system function after approximately 18 minutes, but the leak resulted in a loss of an
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The fire protection main yard piping was made of gray cast iron, internally lined with cement mortar
The fire protection main yard piping was made of gray cast iron, internally lined with cement mortar


and externally protected with a bituminous coating. Initial investigation into the rupture found a
and externally protected with a bituminous coating. Initial investigation into the rupture found a


10-foot longitudinal crack along the bottom surface of the pipe, and a second circumferential crack
10-foot longitudinal crack along the bottom surface of the pipe, and a second circumferential crack


on an adjacent pipe segment that was apparently caused by uplift forces from flow through the initial longitudinal crack. Subsequent evaluations determined that long standing exposure to moist
on an adjacent pipe segment that was apparently caused by uplift forces from flow through the initial longitudinal crack. Subsequent evaluations determined that long standing exposure to moist


or wet soil had resulted in the external reduction in wall thickness at several locations due to
or wet soil had resulted in the external reduction in wall thickness at several locations due to


graphitic corrosion. The thin asphalt coating could not protect the pipe from the highly corrosive
graphitic corrosion. The thin asphalt coating could not protect the pipe from the highly corrosive


environment. The piping was approximately 49 years old. The licensee modified its selective
environment. The piping was approximately 49 years old. The licensee modified its selective


leaching aging management program to increase the number of examinations that it performed to
leaching aging management program to increase the number of examinations that it performed to


identify selective leaching. Additional information can be found in Virginia Electric and Power Co.,
identify selective leaching. Additional information can be found in Virginia Electric and Power Co.,  
Supplement to Subsequent License Renewal Application, dated October 31, 2019 (ADAMS
Supplement to Subsequent License Renewal Application, dated October 31, 2019 (ADAMS


Line 335: Line 335:
July 2019 Surry Power Station Fire Main Yard Loop Piping Rupture
July 2019 Surry Power Station Fire Main Yard Loop Piping Rupture


(ADAMS Accession No. ML20056D677)
(ADAMS Accession No. ML20056D677)  
 
North Anna Power Station, Units 1 and 2


===North Anna Power Station, Units 1 and 2===
In October 2001, a 12-inch buried fire water main yard pipe ruptured during routine fire pump
In October 2001, a 12-inch buried fire water main yard pipe ruptured during routine fire pump


performance testing. Excavation identified a crack more than eight feet long that had progressed
performance testing. Excavation identified a crack more than eight feet long that had progressed


mainly in the axial direction down the length of the pipe. The analysis of the gray cast iron piping
mainly in the axial direction down the length of the pipe. The analysis of the gray cast iron piping


determined that the failure most likely occurred as a result of a low-cycle fatigue process that
determined that the failure most likely occurred as a result of a low-cycle fatigue process that


originated at a pre-existing manufacturing flaw in the pipe. Periodic pump tests apparently caused
originated at a pre-existing manufacturing flaw in the pipe. Periodic pump tests apparently caused


pressure surges in the system. Otherwise, the overall condition of the pipe appeared to be good, with no indications of damage to the internal mortar lining or of external corrosion. This information
pressure surges in the system. Otherwise, the overall condition of the pipe appeared to be good, with no indications of damage to the internal mortar lining or of external corrosion. This information


was recently provided as part of the North Anna Power Station, Application for Subsequent License
was recently provided as part of the North Anna Power Station, Application for Subsequent License
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Safeguards (NMSS) project manager.
Safeguards (NMSS) project manager.


/RA/
/RA/  
                                            Christopher G. Miller, Director
Christopher G. Miller, Director


Division of Reactor Oversight
Division of Reactor Oversight
Line 368: Line 369:
Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


Technical Contacts:   Naeem Iqbal, NRR                     James A. Gavula, NRR
Technical Contacts: Naeem Iqbal, NRR
 
James A. Gavula, NRR
 
301-415-3346 


301-415-3346                        630-829-9755 E-mail: Naeem.Iqbal@nrc.gov          E-mail: James.Gavula@nrc.gov
630-829-9755 E-mail: Naeem.Iqbal@nrc.gov


Brian D. Allik, NRR                  James Downs, NMSS
E-mail:  James.Gavula@nrc.gov


610-337-5376                         301-415-7744 E-mail: Brian.Allik@nrc.gov         E-mail: James.Downs@nrc.gov
Brian D. Allik, NRR
 
James Downs, NMSS
 
610-337-5376
 
301-415-7744 E-mail: Brian.Allik@nrc.gov             E-mail: James.Downs@nrc.gov


John Dymek, Region II
John Dymek, Region II


404-997-4496 E-mail: John.Dymek@nrc.gov
404-997-4496 E-mail: John.Dymek@nrc.gov
 
Note:  NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Library/Document Collections.
 
ML20223A333                                                                  *concurred via e-mail
 
OFFICE
 
APLB:DRA:NRR*
NCSG:DNLR:NRR*
NCSG:DNLR:NRR*
BC:EB2:DRS:RII*
NAME
 
NIqbal
 
JGavula
 
BAllik
 
SShaeffer
 
DATE
 
10/02/2020
10/07/2020
10/07/2020
10/02/2020
OFFICE
 
EB2:DRS:RII*
Tech Editor*
BC:APLB:DRA:NRR*
BC:NCSG:DNRL:NRR*
NAME
 
JDymek
 
JDougherty
 
JBorromeo
 
SBloom
 
DATE
 
10/08/2020
08/17/2020
10/09/2020
10/07/2020
OFFICE
 
BC:CTCF:DFM:NMSS* CTCF:DFM:NMSS*
D:DRA:NRR*
D:DNRL:NRR*
NAME
 
MDiaz
 
SShaeffer
 
MFranovich
 
ABradford
 
DATE
 
10/21/2020
10/20/2020
10/21/2020
10/29/2020
OFFICE
 
D:DFM:NMSS*
D: EB2:DRS:RII*
IOEB:DRO:NRR*
IOEB:DRO:NRR*
NAME
 
AKock
 
MFranke
 
IBetts
 
MLintz


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


ML20223A333                                  *concurred via e-mail
10/23/2020
10/20/2020
11/20/2020
10/29/2020
OFFICE


OFFICE APLB:DRA:NRR*        NCSG:DNLR:NRR*   NCSG:DNLR:NRR*     BC:EB2:DRS:RII*
BC:IOEB:DRO:NRR*  
NAME    NIqbal              JGavula          BAllik              SShaeffer
D:DRO:NRR*  


DATE    10/02/2020          10/07/2020      10/07/2020          10/02/2020
NAME
OFFICE EB2:DRS:RII*          Tech Editor*    BC:APLB:DRA:NRR*    BC:NCSG:DNRL:NRR*
NAME   JDymek              JDougherty      JBorromeo          SBloom


DATE    10/08/2020          08/17/2020      10/09/2020          10/07/2020
LRegner
OFFICE  BC:CTCF:DFM:NMSS* CTCF:DFM:NMSS*      D:DRA:NRR*          D:DNRL:NRR*
NAME    MDiaz                SShaeffer        MFranovich          ABradford


DATE    10/21/2020          10/20/2020      10/21/2020          10/29/2020
CMiller
OFFICE  D:DFM:NMSS*          D: EB2:DRS:RII*  IOEB:DRO:NRR*      IOEB:DRO:NRR*
NAME    AKock                MFranke          IBetts              MLintz


DATE   10/23/2020          10/20/2020      11/20/2020          10/29/2020
DATE
OFFICE  BC:IOEB:DRO:NRR*    D:DRO:NRR*


===NAME    LRegner              CMiller===
12/01/2020  
DATE    12/01/2020             12/17/2020}}
  12/17/2020}}


{{Information notice-Nav}}
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Latest revision as of 07:14, 3 December 2024

Operating Experience Regarding Failure of Buried Fire Protection Main Yard Piping
ML20223A333
Person / Time
Issue date: 12/17/2020
From: Mark Lintz, Chris Miller
NRC/NRR/DRO/IOEB
To:
Mark Litz NRR/DRO/IOEB, 415-4051
References
IN-20-004
Download: ML20223A333 (7)
v • d • e


ML20223A333 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, DC 20555-0001

December 17, 2020

NRC INFORMATION NOTICE 2020-04:

OPERATING EXPERIENCE RELATED TO FAILURE

OF BURIED FIRE PROTECTION MAIN YARD PIPING

ADDRESSEES

All holders of, or applicants for, a fuel facility license under Title 10 of the Code of Federal

Regulations (10 CFR) Part 40, Domestic licensing of source material.

All holders of and applicants for an operating license or construction permit for a nuclear power

reactor issued under 10 CFR Part 50, Domestic licensing of production and utilization facilities, including those that have permanently ceased operations and certified that fuel has been

permanently removed from the reactor vessel.

All holders of and applicants for a power reactor combined license, standard design approval, or

manufacturing license under 10 CFR Part 52, Licenses, certifications, and approvals for nuclear

power plants. All applicants for a standard design certification, including such applicants after

initial issuance of a design certification rule.

All holders of, or applicants for, a fuel cycle facility license under 10 CFR Part 70, Domestic

licensing of special nuclear material.

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform the

addressees of operating experience involving the loss of function of buried cast iron fire water main

yard piping due to multiple factors, including graphitic corrosion1, overpressuration, low-cycle

fatigue, and surface loads. Some of the operating experience has not been captured in industry- wide operating experience reports. The NRC expects that recipients will review the information for

applicability to their facilities and consider actions, as appropriate, to avoid similar problems. INs

may not impose new requirements, and nothing in this IN should be interpreted to require specific

action.

BACKGROUND

Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50 establishes the

minimum criteria for materials, design, fabrication, testing, inspection, and certification of all

structures, systems, and components important to safety. In 10 CFR 50.48, Fire protection, the

NRC requires that each operating nuclear power plant has a fire protection plan that satisfies 10

CFR Part 50, Appendix A, General Design Criterion 3, Fire protection. General Design Criterion 3 states that fire detection and fighting systems of appropriate capacity and capability be provided

and designed to minimize the adverse effect of fires on structures, systems, and components that

1 Graphitic corrosion is a form of galvanic corrosion that occurs in wet or moist environments; it is also known as

selective leaching. are important to safety, and that firefighting systems be designed to assure that their rupture or

inadvertent operation does not significantly impair the safety capability of these structures, systems, and components. Subpart H of 10 CFR Part 70 establishes the NRC's fire protection program

requirements for fuel cycle facilities. Some specific source material licensees have similar

commitments in their NRC license. In 10 CFR 70.61 of Subpart H, the NRC requires each

applicant or licensee to limit the risk of each credible high-consequence event. Several fuel cycle

facilities, including some specific source material facilities, have fire suppression systems credited

as mitigative controls needed to meet these performance requirements. The purpose of these

programs is to safeguard any nuclear material on site and protect the public from radioactive

releases due to a fire event.

The fire protection main yard piping is typically maintained at required operating pressures using

pressure maintenance components, such as a jockey pump. The smaller pump accommodates

nominal system leakage from either non-pressure-boundary sources (e.g., packing, gaskets) or

pressure boundary sources (e.g., through-wall defect). The jockey pump prevents cycling of the

larger main fire pumps, which start on decreasing header pressure or another anticipatory signal.

As pipes leak, over time, the water pressure inside becomes more difficult to maintain within the set

points of the jockey pump.

The water supply of any fire protection system is often considered the most critical component of

the system. The function of underground or buried fire water main yard piping is to move the water

from its source to its final point of use. This piping must be extremely reliable, capable, and able

automatically to distribute enough water directly to a fire to extinguish it or to hold it in check until

the fire brigade arrives.

Internal corrosion of ferrous piping materials (cast iron, ductile iron, and carbon steel) can be a

problem for fire water supply systems. Microbiological action is the most common mechanism

causing the internal corrosion process to occur. Living microorganisms such as sulfate-, iron-, and

manganese-reducing bacteria cause this form of corrosion. These bacteria can develop in the

piping environment with or without oxygen. They can be concentrated and accelerate internal

corrosion, causing either pitting (creating pinhole leaks) or mineral deposits that introduce

increased pressure loss due to the turbulence of the water flow. This is referred to as

microbiologically induced corrosion. External corrosion of buried fire water main yard piping has no

adverse effect on the flow of water through the piping system, up to the point of pipe failure.

Factors influencing external corrosion of buried cast iron piping include piping material, soil

corrosivity, and stray electric ground currents.

Actions to mitigate external corrosion typically include properly designed and applied coatings;

appropriately specified and installed backfill; and properly designed, tested, and maintained

cathodic protections systems. Coatings, however, have a finite effective life, and coating

degradation has been identified in some instances of external corrosion. One method of minimizing

both internal and external corrosion of buried fire water main yard piping is to use nonferrous piping

materials such as HDPE. Some plants have replaced cast iron piping with HDPE piping because it

is immune to service water corrosion and highly resistant to fouling.

Some plants have replaced cast iron piping with HDPE piping because it is immune to service water

corrosion and highly resistant to fouling. However, HDPE piping is a relatively new material

compared to cast iron piping, and therefore long-term service-life data does not exist in significant

quantities. The NRC has approved the replacement of steel piping with HDPE piping in American

Society of Mechanical Engineers Class 3 safety-related nuclear service water system piping associated with the essential service water system at Callaway Plant (ADAMS Accession No.

ML083100288), the emergency diesel generator jacket water coolers at Catawba Nuclear Station

(Catawba) (ADAMS Accession No. ML091240156), and the plant service water at Hatch, Unit 2 (ADAMS Accession No. ML15337A414). In addition, Catawba has installed aboveground HDPE for

nonsafety-related applications. Nonsafety-related use is not part of the NRC approval.

Monitoring jockey pump run times and fire water storage tank levels for adverse trends may help to

detect leaks that could further degrade piping. Excessive jockey pump cycling or a pump that is

continuously running may be indicative of a leak that can erode the supporting soil, resulting in the

cast iron piping being unsupported and subject to tensile stress. These conditions can result in

catastrophic failure of the fire main.

DISCUSSION

Many probabilistic risk assessments (PRA) have shown that fire is a potentially important risk

contributor for U.S. nuclear power plants and may be a significant contributor to a plants total core

damage frequency.2 This IN gives examples in which failures of the buried fire water system main

yard piping involved degradation from selective leaching (graphitic corrosion), overpressure, cyclic

fatigue, and surface loads. Degradation of buried fire water main yard piping could impair the

operation of the fire water suppression system and thus impact the overall risk at the plant.

Cast iron piping is susceptible to the loss of material caused by selective leaching, and it is prone to

sudden ruptures because of its brittle nature. Multiple failures have occurred when pressure

transients from main fire pump starts caused significant cracking in the cast iron piping. These

ruptures have mostly occurred during periodic pump testing and indicate an increased likelihood of

failures during an actual demand on the fire protection system. Taking steps to minimize pressure

transients during periodic testing may mask potential piping degradation.

Leakage from the fire protection water system can be assessed by monitoring pressure

maintenance during component activity (e.g., jockey pump run times). However, non- pressure-boundary leakage cannot be distinguished readily from through-wall degradation, and the

ability to find leakage locations in buried piping will depend on the leak rate and soil drainage

characteristics. In addition, long-term non-pressure-boundary leakage may contribute to higher soil

corrosivity, resulting in more aggressive degradation of the piping. The examples discussed in this

IN illustrate the importance of an effective fire water system aging management program and

represent operating experience related to the failure of buried fire water main yard piping at

operating nuclear power plant sites.

Buried fire water piping systems are built to withstand high levels of pressure. However, the sudden

starting and stopping of flow caused by such components as pumps or hydrants can trigger a

sudden and even dangerous increase in pressure that those systems cannot handle. Buried fire

water piping is vulnerable to cracking from applied loads, such as pressure surges or other dynamic

loading.

2 These include the NRC technical opinion paper Fire PRA Maturity and Realism: A Technical Evaluation, issued January 2016 (Agencywide Documents Access and Management System (ADAMS) Accession

No. ML16022A266), and various detailed plant fire risk analyses related to license amendment requests for the

transition to a risk-informed, performance-based fire protection program in accordance with National Fire

Protection Association (NFPA) 805, Performance-Based Standard for Fire Protection for Light Water Reactor

Electric Generating Plants, and Technical Specifications Task Force Traveler TSTF-505, Provide Risk-Informed

Extended Completion TimesRITSTF Initiative 4b. Nothing in this IN should be interpreted to require specific action; however, enhancements used at

other sites include 1) replacing buried piping with high-density polyethylene (HDPE) piping;

2) incorporating current National Fire Protection Association (NFPA) code and standard

requirements; and 3) expanding the scope of inspection so that the intended function(s) of

structures, systems, and components will be maintained consistent with the current licensing basis

through the period of extended operation.

DESCRIPTION OF CIRCUMSTANCES

Operating experience has indicated that multiple failures of the buried cast iron fire water main yard

piping have occurred due to aging effects, including graphitic corrosion (i.e., selective leaching),

corrosion buildup, low-cyclic fatigue, and general wall thinning or localized loss of material.

Degradation can occur internally or externally to the pipe, or both. Degradation may develop due to

environmental conditions, or it may be initiated as a result of deficiencies in system design, installation, or maintenance. Licensees can detect only such flow blockage as fouling from silt or

sediment, internal coating failures that block flow, or internal tuberculation (i.e., small mounds of

corrosion products on the inside of the pipe). Internal degradation due to corrosion, selective

leaching, or cracking cannot be detected by NFPA periodic testing. Below are descriptions of

recent or recently available operating experience concerning failures of buried fire water main yard

piping.

Edwin I. Hatch Nuclear Plant, Units 1 and 2 On January 25, 2019, a buried 12-inch-diameter fire protection cement-lined cast iron main yard

pipe ruptured as a result of fire water sectional valve isolation capability testing. The pressure

drops from the rupture led to all three fire water pumps starting on a low-pressure signal. After

securing the two diesel-driven fire water pumps, the licensee was able to maintain the system

header pressure with only the motor-driven and jockey pumps running.

The piping rupture was caused by the start of a fire pump and the subsequent pressure surge. The

resulting leak eroded the supporting soil around the pipe, intensifying the bending forces on the

pipe, with a catastrophic pipe failure occurring four hours after the initial pressure change. During

the four-hour period between the fire water sectional valve isolation capability testing and the pipe

rupture, the licensee observed that the jockey fire pump was cycling excessively, indicating a loss

of pressure in the fire protection system from the leak. The licensee later identified a preexisting

pipe crack that had propagated over time until the remaining piping material could no longer

withstand the stresses and ultimately failed.

Surry Power Station, Units 1 and 2 On July 13, 2019, during a periodic test of the electric fire pump, a rupture occurred in a buried

section of 12-inch-diameter fire protection main yard piping. The resulting loss of system pressure

initiated an automatic start of the diesel-driven fire pump. Operators isolated the leak, restoring the

fire protection system function after approximately 18 minutes, but the leak resulted in a loss of an

estimated 112,000 gallons from the fire protection water tanks.

The fire protection main yard piping was made of gray cast iron, internally lined with cement mortar

and externally protected with a bituminous coating. Initial investigation into the rupture found a

10-foot longitudinal crack along the bottom surface of the pipe, and a second circumferential crack

on an adjacent pipe segment that was apparently caused by uplift forces from flow through the initial longitudinal crack. Subsequent evaluations determined that long standing exposure to moist

or wet soil had resulted in the external reduction in wall thickness at several locations due to

graphitic corrosion. The thin asphalt coating could not protect the pipe from the highly corrosive

environment. The piping was approximately 49 years old. The licensee modified its selective

leaching aging management program to increase the number of examinations that it performed to

identify selective leaching. Additional information can be found in Virginia Electric and Power Co.,

Supplement to Subsequent License Renewal Application, dated October 31, 2019 (ADAMS

Accession No. ML19310E716).

July 2019 Surry Power Station Fire Main Yard Loop Piping Rupture

(ADAMS Accession No. ML20056D677)

North Anna Power Station, Units 1 and 2

In October 2001, a 12-inch buried fire water main yard pipe ruptured during routine fire pump

performance testing. Excavation identified a crack more than eight feet long that had progressed

mainly in the axial direction down the length of the pipe. The analysis of the gray cast iron piping

determined that the failure most likely occurred as a result of a low-cycle fatigue process that

originated at a pre-existing manufacturing flaw in the pipe. Periodic pump tests apparently caused

pressure surges in the system. Otherwise, the overall condition of the pipe appeared to be good, with no indications of damage to the internal mortar lining or of external corrosion. This information

was recently provided as part of the North Anna Power Station, Application for Subsequent License

Renewal, August 24, 2020 (ADAMS Accession No. ML20246G696).

CONTACT

Please direct any questions about this matter to the technical contacts listed below or to the

appropriate Office of Nuclear Reactor Regulation (NRR) or Office of Nuclear Material Safety and

Safeguards (NMSS) project manager.

/RA/

Christopher G. Miller, Director

Division of Reactor Oversight

Office of Nuclear Reactor Regulation

Technical Contacts: Naeem Iqbal, NRR

James A. Gavula, NRR

301-415-3346

630-829-9755 E-mail: Naeem.Iqbal@nrc.gov

E-mail: James.Gavula@nrc.gov

Brian D. Allik, NRR

James Downs, NMSS

610-337-5376

301-415-7744 E-mail: Brian.Allik@nrc.gov E-mail: James.Downs@nrc.gov

John Dymek, Region II

404-997-4496 E-mail: John.Dymek@nrc.gov

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

ML20223A333 *concurred via e-mail

OFFICE

APLB:DRA:NRR*

NCSG:DNLR:NRR*

NCSG:DNLR:NRR*

BC:EB2:DRS:RII*

NAME

NIqbal

JGavula

BAllik

SShaeffer

DATE

10/02/2020

10/07/2020

10/07/2020

10/02/2020

OFFICE

EB2:DRS:RII*

Tech Editor*

BC:APLB:DRA:NRR*

BC:NCSG:DNRL:NRR*

NAME

JDymek

JDougherty

JBorromeo

SBloom

DATE

10/08/2020

08/17/2020

10/09/2020

10/07/2020

OFFICE

BC:CTCF:DFM:NMSS* CTCF:DFM:NMSS*

D:DRA:NRR*

D:DNRL:NRR*

NAME

MDiaz

SShaeffer

MFranovich

ABradford

DATE

10/21/2020

10/20/2020

10/21/2020

10/29/2020

OFFICE

D:DFM:NMSS*

D: EB2:DRS:RII*

IOEB:DRO:NRR*

IOEB:DRO:NRR*

NAME

AKock

MFranke

IBetts

MLintz

DATE

10/23/2020

10/20/2020

11/20/2020

10/29/2020

OFFICE

BC:IOEB:DRO:NRR*

D:DRO:NRR*

NAME

LRegner

CMiller

DATE

12/01/2020

12/17/2020


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