ML100640449 

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

OFFICE OF NUCLEAR REACTOR REGULATION 

OFFICE OF NEW REACTORS 

WASHINGTON, DC 20555-0001 

June 18, 2010 

NRC INFORMATION NOTICE 2010-12: CONTAINMENT LINER CORROSION 

ADDRESSEES 

All holders of an operating license or construction permit for a nuclear power reactor issued 

under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, “Domestic Licensing of 

Production and Utilization Facilities,” except those who have permanently ceased operations 

and have certified that fuel has been permanently removed from the reactor vessel. 

All holders of or applicants for a standard design certification, standard design approval, 

manufacturing license, or combined license issued under 10 CFR Part 52, “Licenses, 

Certifications, and Approvals for Nuclear Power Plants.” 

PURPOSE

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

addressees of recent issues involving corrosion of the steel reactor containment building liner. 

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

consider actions, as appropriate, to avoid similar problems. The suggestions contained in this 

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

DESCRIPTION OF CIRCUMSTANCES 

Beaver Valley Power Station

On April 23, 2009, during a refueling outage at Beaver Valley Power Station, Unit 1, the licensee 

performed a visual examination of the interior reactor containment building steel liner in 

accordance with Subsection IWE, “General Visual Examination,” of American Society of 

Mechanical Engineers (ASME) Section XI of the Boiler and Pressure Vessel Code, “Rules for 

Inservice Inspection of Nuclear Power Plant Components.” At a containment elevation of 

746 feet, the licensee identified an area approximately 3 inches in diameter that exhibited 

blistered paint. The paint blister was intact at the time of discovery. Collapse of the blister 

during further inspection revealed a protruding rust product underneath. The licensee then 

cleaned this area to allow further evaluation. The cleaning activity uncovered a rectangular area 

of approximately 1 inch (horizontal) x 3/8 inch (vertical) that penetrated through the entire liner 

plate thickness. Ultrasonic testing (UT) of the surrounding area showed liner thinning within an 

area of approximately 10 square inches. The licensee removed the corroded section of the liner 

and discovered a partially decomposed piece of wood approximately 2 inches x 4 inches x 

6 inches embedded in the concrete behind the section of the liner. The wood was left behind as 
IN 2010-12 

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a result of inadequate housekeeping and quality assurance practices during the original 

construction of the containment wall in the early 1970s. 

The licensee determined that the cause of the through-wall liner corrosion was a pitting-type 

corrosion (rust) originating from the concrete side caused by foreign material (wood) that was in 

contact with the containment carbon steel liner. Licensee corrective actions included removing 

the embedded wood, grouting the concrete area that was displaced by the wooden debris, and 

welding a new section of steel plate to replace the previously removed portion of the liner. The 

licensee also scheduled an examination of the containment liner during the next refueling 

outage at Beaver Valley Power Station Units, 1 and 2 to visually inspect 100 percent of the 

accessible liner area. In addition, the licensee stated in its license renewal submittals that it 

would perform: (a) supplemental volumetric examinations of 1-square-foot samples in at least 

75 random locations of each unit’s containment liner in order to statistically determine whether 

the containment liner is unacceptably degraded by corrosion originating from the concrete side; 

and (b) supplemental volumetric examinations of a minimum of eight one-foot square locations 

in the accessible areas of liner plate at locations that operating experience shows are 

susceptible to localized pitting corrosion. 

Additional information is available in Beaver Valley Licensee Event Report 50-334/2009-003-00, 

dated June 18, 2009, and Beaver Valley Power Station, Unit 1, NRC Routine Inspection 

Report 05000334/2009006, dated July 6, 2009, which can be found on the NRC’s public Web 

site under Agencywide Documents Access and Management System (ADAMS) Accession 

Nos. ML091740056 and ML091870328, respectively. 

Brunswick Steam Electric Plant

During a refueling outage in 2008 at Brunswick Steam Electric Plant, Unit 1, the licensee 

performed a VT-1 visual inspection of the primary containment penetration sleeve for the 

personnel air lock and found two bulged areas. The discovery of thinned areas on the bulges 

led the licensee to perform UT examinations of the entire Unit 1 personnel air lock penetration 

sleeve. These additional UT inspections identified many discrete locations that were below the 

minimum wall thickness established by the design-basis containment liner specification. 

During construction, the outside diameter of the sleeve was wrapped with two layers of 1/4 inch 

felt and the felt was covered with a layer of 60 mil ethylene propylene film. The felt was 

intended to permit the sleeve to expand when subjected to thermal loading. The licensee’s 

evaluation determined that the bulges were caused by corrosion product buildup between the 

sleeve and the concrete backing. This corrosion was caused by the felt that wrapped the 

outside of the containment penetration sleeve; which became wet during the original 

construction. 

Samples of the degraded areas of the sleeve and felt wrapping were sent to the licensee’s 

center for evaluation of potential ongoing corrosion mechanisms. These evaluations identified 

that the pitting and corrosion on the concrete side of the sleeve were caused by under-deposit 

corrosion. 
IN 2010-12 

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Licensee corrective actions include installing a new concentric sleeve inside the personnel air 

lock penetration to repair the existing containment penetration sleeve. Following this planned 

modification, the new sleeve will become the primary containment liner for this penetration. 

Salem Nuclear Generating Station

In October 2009, at Salem Nuclear Generating Station Unit 2, the licensee inspected the 

containment moisture barrier (the silicone RTV [room temperature vulcanizing] seal between the 

concrete floor and containment liner) and found heavy corrosion on the containment liner within 

6 inches of the concrete floor. This area of the containment liner was considered inaccessible 

because it was normally covered by an insulation package that consisted of a layer of sheet 

metal, a layer of plastic sheeting, and a layer of insulation. The licensee had not inspected the 

containment liner areas covered by this insulation because ASME Code Section XI allowed an 

exemption for inaccessible areas. In response to this discovery, and as a conservative 

approach to the license renewal process, the licensee decided to enhance inspections of the 

containment liner above the moisture barrier within about 6 inches of the concrete floor and to 

randomly inspect several other areas that were covered by the insulation package. To perform 

the inspections, the licensee removed that portion of the insulation package that extended 

below the lower leak detection channel for the entire containment liner circumference, and cut 

through and removed the insulation package for four other randomly selected areas. Licensee 

inspections in these four areas identified some corrosion but subsequent ultrasonic 

measurements did not indicate significant wall loss. 

To evaluate the effect of the identified general corrosion on the safety function of the 

containment boundary and to meet the expanded inspection requirements of ASME Code 

Section XI, the licensee performed ultrasonic testing of 440 locations on the bottom 6 inches of 

the cylindrical portion of the containment liner. Based on the results of the measurements at 

these locations, the licensee determined that the liner remained operable because the lowest 

thickness measured was 0.677 inches, which was above the design-required minimum wall 

thickness of 0.43 inches. The actual safety significance of this general corrosion was minor 

because there was significant design margin for the liner in this area. 

The licensee reviewed the circumstances that led to the identified areas of heavy corrosion on 

the liner and determined that previous containment liner inspections were not performed 

adequately. Specifically, examinations should have identified evidence of corrosion (rust on 

floor) and prompted removal of lagging to determine the source of the corrosion products. 

The licensee determined that the source of the moisture that caused the liner corrosion at the 

joint between the containment liner and concrete floor was service water leakage from the 

containment fan coil units and associated piping. Licensee corrective actions included 

conducting frequent containment walk-downs to identify, isolate, and repair any identified 

service water leaks; verifying that the leakage from existing service water leaks did not reach 

the containment liner; and, until the base of the containment liner is re-coated during a future 

refueling outage, revising procedures to ensure liner inspections were performed when 

containment service water leaks were identified. In addition, the licensee stated in its license 

renewal submittals that it would perform supplemental and augmented examinations of the liner 

plates at random and non-random locations. 
IN 2010-12 

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BACKGROUND 

Related NRC communications include the following: 

• IN 2004-09, “Corrosion of Steel Containment and Containment Liner,” dated 

April 27, 2004 (ADAMS Accession No. ML041170030) 

• IN 1997-10, “Liner Plate Corrosion in Concrete Containments,” dated March 13, 1997 

(ADAMS Accession No. ML031050365) 

DISCUSSION 

This IN provides examples of containment liner degradation caused by corrosion. Concrete 

reactor containments are typically lined with a carbon steel liner to ensure a high degree of leak 

tightness during operating and accident conditions. The reactor containment is required to be 

operable as specified in plant technical specifications to limit the leakage of fission product 

radioactivity from the containment to the environment. The regulations at 10 CFR 50.55a, 

“Codes and Standards,” require the use of Subsection IWE of ASME Section XI to perform 

inservice inspections of containment components. The required inservice inspections include 

periodic visual examinations and limited volumetric examinations using ultrasonic thickness 

measurements. The containment components include the steel containment liner and integral 

attachments for the concrete containment, containment personnel airlock and equipment hatch, 

penetration sleeves, moisture barriers, and pressure-retaining bolting. The NRC also requires 

licensees to perform leak rate testing of the containment pressure-retaining components and 

isolation valves according to 10 CFR Part 50, Appendix J, “Primary Reactor Containment 

Leakage Testing for Water-Cooled Power Reactors,” as specified in plant technical 

specifications. This operating experience highlights the importance of good quality assurance, 

housekeeping and high quality construction practices during construction operations in 

accordance with 10 CFR Part 50, Appendix B, “Quality Assurance Criteria for Nuclear Power 

Plants and Fuel Reprocessing Plants.” 

Operating experience shows that containment liner corrosion is often the result of liner plates 

being in contact with objects and materials that are lodged between or embedded in the 

containment concrete. Liner locations that are in contact with objects made of an organic 

material are susceptible to accelerated corrosion because organic materials can trap water that 

combined with oxygen will promote carbon steel corrosion. Organic materials can also cause a 

localized low pH area when they decompose. Organic materials located inside containment can 

come in contact with the containment liner and cause accelerated corrosion. However, 

corrosion that originates between the liner plate and concrete is a greater concern because 

visual examinations typically identify the corrosion only after it has significantly degraded the 

liner. In some cases, licensees identified such corroded areas by performing ultrasonic 

examination of suspect areas (e.g., areas of obvious bulging, hollow sound). 

The objects and materials that caused liner corrosion that licensees have found lodged between 

or embedded in the containment concrete include both foreign material (e.g., wooden pieces, 

workers’ gloves, wire brush handles) and material that was deliberately installed as part of the 

design such as the felt material described in the above example at Brunswick Steam Electric 
IN 2010-12 

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Plant, Unit 1. Although there is no regulatory requirement to do so, one or more licensees have 

chosen to review design documents to identify locations where organic material was 

intentionally installed between the liner or penetration sleeve and schedule additional 

examinations of these areas to monitor for liner material loss. 

GENERIC IMPLICATIONS 

In response to the above through-wall corrosion at Beaver Valley Power Station, Unit 1, the 

NRC Office of Nuclear Reactor Regulation requested the NRC Office of Regulatory Research to 

begin an assessment to better understand the possible mechanisms responsible for throughwall corrosion of containment liners. The NRC staff has also engaged committee members for 

ASME Section XI to devise a formal tracking mechanism to monitor industry experience and 

events involving containment liner corrosion. Subsection IWE of ASME Section XI could then 

be updated using insights from these events. 

CONTACT 

This IN requires no specific action or written response. Please direct any questions about this 

matter to the technical contacts listed below or to the appropriate Office of Nuclear Reactor 

Regulation (NRR) project manager. 

/RA/ /RA by MShuaibi for/ 

Timothy McGinty, Director Glenn Tracy, Director 

Division of Policy and Rulemaking Division of Construction Inspection and 

Office of Nuclear Reactor Regulation Operational Programs 

 Office of New Reactors 

Technical Contacts: Mike Brown, NRR William Jessup, NRR 

 301-415-4096 301-415-2972 

 E-mail: Michael.Brown@nrc.gov E-mail: William.Jessup@nrc.gov 

 Paul Klein, NRR 

 301-415-4030 

 E-mail: Paul.Klein@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. 
IN 2010-12 

Page 5 of 5 

Plant, Unit 1. Although there is no regulatory requirement to do so, one or more licensees have 

chosen to review design documents to identify locations where organic material was 

intentionally installed between the liner or penetration sleeve and schedule additional 

examinations of these areas to monitor for liner material loss. 

GENERIC IMPLICATIONS 

In response to the above through-wall corrosion at Beaver Valley Power Station, Unit 1, the 

NRC Office of Nuclear Reactor Regulation requested the NRC Office of Regulatory Research to 

begin an assessment to better understand the possible mechanisms responsible for throughwall corrosion of containment liners. The NRC staff has also engaged committee members for 

ASME Section XI to devise a formal tracking mechanism to monitor industry experience and 

events involving containment liner corrosion. Subsection IWE of ASME Section XI could then 

be updated using insights from these events. 

CONTACT 

This IN requires no specific action or written response. Please direct any questions about this 

matter to the technical contacts listed below or to the appropriate Office of Nuclear Reactor 

Regulation (NRR) project manager. 

/RA/ /RA by MShuaibi for/ 

Timothy McGinty, Director Glenn Tracy, Director 

Division of Policy and Rulemaking Division of Construction Inspection and 

Office of Nuclear Reactor Regulation Operational Programs 

 Office of New Reactors 

Technical Contacts: Mike Brown, NRR William Jessup, NRR 

 301-415-4096 301-415-2972 

 E-mail: Michael.Brown@nrc.gov E-mail: William.Jessup@nrc.gov 

 Paul Klein, NRR 

 301-415-4030 

 E-mail: Paul.Klein@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. 

ADAMS Accession No.: ML100640449 TAC ME3101 

OFFICE IOEB:DIRS SCVB:DSS Tech Editor BC:SCVB:DSS D:DSS 

NAME MBrown JBettle KAzariah-Kribbs RDennig WRuland 

DATE 03/30/10 05/24/10 e-mail 05/21/10 e-mail 05/24/10 e-mail 5/27/10 e-mail 

OFFICE BC:EMCB:DE BC:CSGB:DCI BC:SPCV:DSRA BC:RASB:DLR BC:IOEB:DIRS 

NAME MKhanna RTaylor JMcKirgan RAuluck JThorp 

DATE 5/25/2010 e-mail 5/25/10 e-mail 5/27/10 e-mail 6/9/10 e-mail 5/25/10 e-mail 

OFFICE LA:PGCB:NRR PM:PGCB:NRR (A)BC:PGCB:NRR D:DCIP:NRO D:DPR:NRR 

NAME CHawes DBeaulieu TAlexion GTracy(MShuaibi 

for) 

TMcGinty 

OFFICE 6/10/10 5/27/10 6/10/10 7/17/10 6/18/10 

OFFICIAL RECORD COPY