Information Notice 1997-10, Liner Plate Corrosion in Concrete Containments

Liner Plate Corrosion in Concrete Containments
	ML031050365
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	03/13/1997
From:	Martin T; Office of Nuclear Reactor Regulation
To:	;
References
	IN-97-010, NUDOCS 9703140144
	Download: ML031050365 (12)
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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 March 13, 1997 NRC INFORMATION NOTICE 97-10: LINER PLATE CORROSION IN CONCRETE

CONTAINMENTS

Addressees

All holders of operating licenses or construction permits for power reactors.

Purpose

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

addressees to occurrences'of corrosion in the liner plates of reinforced and pre-stressed

concrete containmnents, and to detrimental effects such corrosion could have on containment

reliability and availability under design-basis and beyond-design-basis events. It is expected

that recipients will review this information for applicability to their facilities and consider

actions, as appropriate. However, suggestions contained in this information notice are not

NRC requirements; therefore, no specific action or written response is required.

Background

Criterion 16 of the General Design Criteria of 10 CFR Part 50 requires that the reactor

containment and associated systems shall be provided to establish an essentially leaktight

barrier against the uncontrolled release of radioactivity to the environment. To meet this

leak-tightness requirement, the inside surfaces of concrete containments are lined with thin

metallic plates, generally between 6.2 mm (1/4 in.) and 9.5 mm (3/8 in.) thick. The liner

plates are attached to the concrete by means of stud anchors or structural rolled shapes or

both.

The design process assumes that the liner plates do not carry loads. However, the normal

loads, such as from concrete shrinkage, creep and thermal changes, imposed on the

concrete containment structure are transferred to the liner plates through the anchorage

system. Internal pressure and temperature loads are directly applied to the liner plate. Thus, under design-basis conditions, the liner plate could experience significant strains.Section III,

Division 2 of the American Society of Mechanical Engineers (ASME) Boiler and Pressure

Vessel Code (also called American Concrete Institute Standard 359), "Code for Concrete

Reactor Vessels and Containments," allows liner tensile strains up to 0.004 cm/cm (inchfinch)

of material for normal operating stresses, and up to 0.01 cm/cm (inch/inch) for stresses

resulting from the postulated environmental and accident conditions. American Society for

Testing and Materials (ASTM) Standard A516 (or equivalent) steel is typically used in the

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IN 97-10

March 13, 1997 construction of containments. The minimum ultimate tensile strain of the liner material is

0.2 cm/cm (inch/inch). Thus, there is a minimum safety factor of 20 above the theoretically

calculated liner strains.

Any corrosion (metal thinning) of the liner plate could change the failure threshold of the liner

plate under a challenging environmental or accident condition. Thinning changes the

geometry of the liner plate, creating different transitions and strain concentration conditions.

This may reduce the design margin of safety against postulated accident and environmental

loads.

Description of Circumstances

Inspections of containment liners have shown various degrees of corrosion.

In January 1993, an NRC inspector pointed out corrosion of the drywell liner at Unit 2 of the Brunswick plant. The liner was corroded at various spots at the junction of the

base floor and the liner. A subsequent examination of Unit I showed similar

corrosion.

During the NRC staffs structural assessment review in June 1992, the staff noted

peeled coating and spots of liner corrosion at Trojan (not operating) and at Beaver

Valley Unit 1.

Before integrated leak rate testing of the containment at Salem Unit 2 in 1993, the

licensee's staff noted minor corrosion of the containment liner.

During the NRC staff's structural assessment review in April 1992, discoloration of the

vertical portion of the containment liner was observed at an insulation joint at

Robinson Unit 2.

Discussion

Of the five occurrences cited above, four (Trojan and Beaver Valley Unit 1, Salem Unit 2, and

Robinson Unit 2) were found to be benign from the standpoint of safety. However, the

licensees were sensitized to the conditions for future monitoring and repairs, as appropriate.

Corrosion of the liner plate at Brunswick Units 1 and 2 was significant from the standpoint of

safety. The sealing material along the circumference at the junction of the drywell.wall and

the bottom floor had significantly degraded from the water accumulation at the junction. The

liner plate was found to have pitted significantly (as much as 50 percent of the original

thickness) at various locations along the circumference. Before the restart of the two

Brunswick units, the licensee cleaned the joint areas, repaired the pitted liner plate areas, and resealed the entire gap at the junction with dense silicone elastomer. The repair of the

pitted areas consisted of (1) welding the pitted areas, (2) examining the repaired areas in

accordance with the ASME Section III, Division 2, and (3) recoating the repaired areas.

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IN 97-10

March 13, 1997 Corrosion of a liner plate can occur at a number of places where the metal can be exposed

to moisture, or where moisture can condense (behind insulation) or accumulate. Potential

locations for liner plate corrosion are (1) the junction of the containment cylinder and

intermediate floors and basemat concrete (PWRs and Mark IlIl BWRs), (2) the junction of the

drywell and the base or intermediate concrete floors (Mark I, Mark II concrete containments),

(3) adjacent to crane girder rails and supports attached to the liner plate (concrete

containments), (4) water-soaked areas where carbon steel liner plate is used (Mark II and

Mark Ill containments), and (5) behind insulation and ice-condenser baskets.

An amendment to 10 CFR 50.55a became effective September 9, 1996. This amendment, by endorsing the use of Subsections IWE and IWL of Section Xl of the ASME Boiler and

Pressure Vessel Code, provides detailed requirements for inservice inspection of containment

structures. Inspection (which includes examination, evaluation, repair, and replacement) of

concrete containment liner plate in accordance with the 10 CFR 50.55a requirements

involves consideration of the potential corrosion areas.

This information notice requires no specific action or written response. If you have any

questions about information in this notice, please contact one of the technical contacts listed

below or the appropriate NRR project manager.

Thomas T. Martin, Directo

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical Contacts: Hans Ashar, NRR

(301) 415-2851 E-mail: hga@nrc~gov

R. A. Benedict, NRR

(301) 415-1157 E-mail: rabl@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

Ad 74aI F4 u

K2 Attachment

IN 97-10

March 13, 1997 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

97-09 Inadequate Main Steam 03/12/97 All holders of OLs

Safety Valve (MSSV) or CPs for nuclear

Setpoints and Perform- power reactors

ance Issues Associated

with Long MSSV Inlet

Piping

97-08 Potential Failures 03/12/97 All holders of OLs

for General Electric or CPs for nuclear

Magne-Blast Circuit power reactors

Breaker Subcomponents

97-07 Problems Identified 03/06/97 All holders of OLs

During Generic Letter or CPs for nuclear

89-10 Closeout power reactors

Inspections

97-06 Weaknesses in Plant- 03/04/97 All holders of OLs

Specific Emergency or CPs for nuclear

Operating Procedures power reactors with

for Refilling the with once-through

Secondary Side of Dry steam generators

Once-Through Steam

Generators

91-85, Potential Failures of 02/27/97 All holders of OLs

Rev. 1 Thermostatic Control or CPs for nuclear

Valves or Diesel power reactors

Generator Jacket

Cooling Water

97-05 Offsite Notification 02/27/97 All holders of OLs

Capabilities or CPs for nuclear

power reactors and

test and research

reactors

OL = Operating License

CP = Construction Permit

IN 97-10

March 13, 1997 Corrosion of a liner plate can occur at a number of places where the metal can be exposed

to moisture, or where moisture can condense (behind insulation) or accumulate. Potential

locations for liner plate corrosion are (1) the junction of the containment cylinder and

intermediate floors and basemat concrete (PWRs and Mark Ill BWRs), (2) the junction of the