Information Notice 1997-84, Rupture in Extraction Steam Piping as a Result of Flow-Accelerated Corrosion

Rupture in Extraction Steam Piping as a Result of Flow-Accelerated Corrosion

ML031050037
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, 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, Crane
Issue date:	12/11/1997
From:	Roe J Office of Nuclear Reactor Regulation
To:
References
IN-97-084, NUDOCS 9712090140
Download: ML031050037 (12)

'

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001

December 11, 1997

NRC INFORMATION NOTICE 97-84: RUPTURE IN EXTRACTION STEAM PIPING AS A

RESULT OF FLOW-ACCELERATED CORROSION

Addressees

All holders of operating licenses for nuclear power reactors except those who have permanently

ceased operations and have certified that fuel has been permanently removed from the reactor

vessel.

Purpose

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

addressees to potential generic problems related to the occurrence and prediction of flow- accelerated corrosion (FAC) in extraction steam systems. 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.

Description of Circumstances

On April 21, 1997, Omaha Public Power District's Fort Calhoun Station, while operating at 100-

percent power, experienced an approximate 0.56 m2 [6 ftl rupture of a 30.5-centimeter [12- inch]-diameter sweep elbow (radius equal to five times the pipe diameter) in the fourth-stage

extraction steam piping. The operator, upon hearing steam noise and observing steam rising

from the turbine deck, believed that a steam line had broken and manually scrammed the

reactor. As a precaution, emergency boration was initiated. The main turbine tripped

automatically as a result of the reactor trip. The turbine trip had the effect of isolating the

rupture. Plant systems and related parameters responded as expected during the event.

The steam line rupture damaged a nonsafety-related electrical load center in the vicinity of the

pipe break. Additionally, collateral damage was experienced in several cable trays and pipe

hangers, and insulation containing asbestos was blown throughout the turbine building. Certain

portions of the fire protection system actuated in response to fusible links in the sprinkler heads

melting because of high temperature. Because there were no personnel in the immediate

vicinity of the rupture, no one was injured.

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IN 97-84 December 11, 1997 The fourth-stage extraction steam system emanates from the outlet of the high-pressure turbine

and preheats the feedwater heaters. The design operating conditions in the piping are

2068 kilopascal gauge [300 psig] and 2180C [4250F], with a steam quality of approximately

92 percent. The piping is fabricated of A-1 06B carbon steel and has a nominal wall thickness of

0.953 centimeter [0.375 inch]. The licensee's root cause assessment attributed the failure to

FAC in the extraction steam piping. Initial indications of degradation in the extraction steam line

at the Fort Calhoun facility were first discovered in 1985, when the furthest upstream long- radius elbow (radius equal to one and a half times the pipe diameter) was replaced because of

a pinhole leak. At that time the next upstream sweep elbow was also replaced.

The fourth-stage extraction steam system had been recognized as a system that was

susceptible to erosion and/or corrosion. It was, therefore, being monitored by the licensee's

erosion and corrosion control program. Part of the licensee program was utilizing the

CHECWORKS computer code to identify high-wear-rate areas to be selected for inspection.

The CHECWORKS model for the fourth-stage extraction steam piping predicted that long- radius elbows would wear at a higher rate than the sweep elbows when exposed to similar

conditions. Using CHECWORKS predictions, the licensee inspected and replaced all four long- radius elbows, but the failed sweep elbow was never inspected.

Part of the licensee's corrective actions following the rupture included inspecting all sweep

elbows that had not been previously inspected. The measured wall thickness (0.112 centimeter

[0.044 inch]) of the furthest downstream sweep elbow in the fourth-stage extraction piping was

also significantly below the minimum wall thickness (0.272 centimeter [0.107 inch]) specified by

code requirements and had to be replaced. Additionally, another sweep elbow in the fourth- stage extraction piping was also replaced because the wear (measured wall thickness of

0.394 centimeter [0.155 inch]) was considered excessive, even though it was not below the

minimum allowable thickness.

The CHECWORKS predictions of the wear in the fourth-stage extraction steam system were

not consistent with the actual observed wear rates as measured on the components, that is, sweep elbows showed substantially greater wear than predicted.

IN 97-84 December 11, 1997 Subsequent investigations by the licensee determined that the inconsistencies between

predicted and actual wear were due to two factors. First, the "line correction factor" calculated

by CHECWORKS for the fourth-stage extraction steamline was not within the acceptable range

specified in the CHECWORKS users' manual. The line correction factor in CHECWORKS is

used to adjust wear rate predictions in a given line to account for plant operating conditions that

may vary with time. It is determined by comparing predicted wear to measured wear at

locations in the line which have been inspected.

In order for the CHECWORKS predicted wear rate for a location to be valid, the line correction

factor must be between 0.5 and 2.5. For the line containing the sweep elbow that failed, the

wear rates calculated by CHECWORKS used a line correction factor that was outside this

range. Therefore, as specified in the CHECWORKS users' manual, the predicted wear rates

for this line were not valid.

Second, the line correction factor was biased and thus underpredicted the wear rates. In 1987, the licensee updated the parameters used by CHECWORKS to include the wear measured in a

long-radius elbow. One of the inputs in CHECWORKS is the length of time the component has

been In service. The licensee assumed that this elbow had been in service since initial

operation of the plant In 1973; however, the elbow had been replaced in 1985. Therefore, the

actual wear occurred over 2 years rather than the presumed 14 years. Thus, the period of time

that was assumed for the wear to have occurred caused CHECWORKS to calculate a line

correction factor that underestimated the wear rates for sites in the line.

This event revealed the importance of understanding the limitation of methodologies used in

computer programs and of incorporating accurate plant-specific data from nondestructive

examination programs.

Related Generic Communications

In NRC Bulletin 87-01, "Thinning of Pipe Walls in Nuclear Power Plants," July 9, 1987, the staff

asked licensees and applicants to inform the NRC about their programs for monitoring the wall

thickness of carbon steel piping (Accession No. 8707020018).

In NRC Generic Letter 89-08, "Erosion/Corrosion Induced Pipe Wall Thinning," May 2,1989, the staff asked licensees and applicants to Implement long-term erosion/corrosion monitoring

programs (Accession No. 8905040276).

IN 97-84 December 11, 1997 Additionally, the following NRC information notices (INs) provide information about similar

events related to FAC:

IN 82-22, "Failures in Turbine Exhaust Lines," July 9, 1982 (Accession No. 8204210392).

IN 86-106, nFeedwater Line Break," December 16, 1986 (Accession No. 8612160250).

IN 87-36, "Significant Unexpected Erosion of Feedwater Lines," August 4, 1987 (Accession

No. 8707290264).

IN 88-17, "Summary of Responses to NRC Bulletin 87-01, 'Thinning of Pipe Walls In Nuclear

Power Plants," April 22, 1988 (Accession No. 8804180039).

IN 89-53, "Rupture of Extraction Steam Line on High Pressure Turbine," June 13, 1989 (Accession No. 8906070273).

IN 91-18, "High Energy Pipe Failures Caused by Wall Thinning," March 12, 1991 (Accession No. 9103060153).

IN 91 -18, Supplement 1, "High Energy Pipe Failures Caused by Wall Thinning," December 18,

1991 (Accession No. 9112120218).

IN 93-21, "Summary of NRC Staff Observations Compiled During Engineering Audits or

Inspections of Licensee Erosion/Corrosion Programs," March 25, 1993 (Accession

No. 9303190051).

IN 95-11, "Failure of Condensate Piping Because of Erosion/Corrosion at a Flow-Straightening

Device," February 24, 1995 (Accession No. 9502210050).

IN 97-84 December 11, 1997 This information notice requires no specific action or written response. However, recipients are

reminded that they are required to consider industry-wide operating experience (including NRC

information notices) where practical, when setting goals and performing periodic evaluations

under Section 50.65, Requirement for monitoring the effectiveness of maintenance at nuclear

power plants," to Part 50 of Title 10 of the Code of Federal Regulations. If you have any

questions about the information in this notice, please contact the technical contact listed below

or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

J.).

RoActing Director

Pi ision of Reactor Program Management

ice of Nuclear Reactor Regulation

Technical contact: J. Shackelford, RIV

(817) 860-8144 E-mail: jIs2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

Attachment

IN 97-84

December 11, 1997 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

95-49, Seismic Adequacy of

12/10/97

All holders of OLs for nuclear

Sup. 1 Thermo-Lag Panels

power reactors

97-83 Recent Events Involving

12/05/97 All holders of OLs for pressurized- Reactor Coolant System

water reactors, except those

Inventory Control During

licensees who have permanently

Shutdown

ceased operations and have

certified that fuel has been

permanently removed from the

reactor vessel

97-82 Inadvertent Control Room

11/28/97

All holders of OLs for nuclear

Halon Actuation Due to a

power reactors

Camera Flash

97-81 Deficiencies in Failure

11/24197

All holders of OLs for nuclear

Modes and Effects Analyses

power reactors except those

for Instrumentation and Control

who have ceased operations

Systems

and have certified that fuel

has been permanently removed

from the vessel

97-80

Licensee Technical

11/21197

All holders of OLs for

Specifications

nuclear power reactors

Interpretations

OL = Operating License

CP = Construction Permit

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IN 97-84 December 11, 1997 This information notice requires no specific action or written response. However, recipients are

reminded that they are required to consider industry-wide operating experience (including NRC

information notices) where practical, when setting goals and performing periodic evaluations

under Section 50.65, "Requirement for monitoring the effectiveness of maintenance at nuclear

power plants," to Part 50 of Title 10 of the Code of Federal Regulations. If you have any

questions about the information in this notice, please contact the technical contact listed below

or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contact: J. Shackelford, RIV

(817) 860-8144 E-mail: jls2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC

TECH EDITOR*

RIV/DRS*by email

RIV/DRS*by email

PECB:DRPM*

NAME

R. Sanders

J. Shackelford

D. Chamberlain

T. Greene

l DATE

09/11/97

09/16/97

109/16/97

09/20/97 OFC

EMCB:DE*

C(A)/EMCB:DE*

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SUPECB:DRPM*

NAME

K. Parczewski

E. Sullivan

B. Sheron

R. Dennig

DATE

9/23/97

9/23/97

9/23/97

11/21/97 I

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NAME

S. Richards

J. &

DATE

11/26/97

12/6197 j

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[OFFICIAL RECORD COPY]

DOCUMENT NAME: 97-84.IN

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IN 97-XX

November XX, 1997 This information notice requires no specific action or written response. However, recipients are

reminded that they are required to consider industry-wide operating experience (including NRC

information notices) where practical, when setting goals and performing periodic evaluations

under Section 50.65, "Requirement for monitoring the effectiveness of maintenance at nuclear

power plants," to Part 50 of Title 10 of the Code of Federal Regulations. If you have any

questions about the information in this notice, please contact the technical contact listed below

or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contact: J. Shackelford, RIV

(817) 860-8144 E-mail: jis2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC

l TECH EDITOR*

RlV/DRS*by email

RIV/DRS*by email

PECB:DRPM*

NAME

R. Sanders

J. Shackelford

D. Chamberlain

T. Greene

DATE

j 09/11/97

09/16/97

09/16/97

09/20/97 OFC

EMCB:DE*

C(A)/EMCB:DE*

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NAME

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IN 97-XX

November XX, 1997 This information notice requires no specific action or written response. However, recipients

are reminded that they are required to consider industry-wide operating experience (including

NRC information notices) where practical, when setting goals and performing periodic

evaluations under Section 50.65, "Requirement for monitoring the effectiveness of

maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of Federal

Regulations. If you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation

(NRR) project manager.

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contact: J. Shackelford, RIV

(817) 860-8144 E-mail: jIs2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC

TECH EDITOR*

RIV/DRS*by email

RIVIDRS*by email

PECB:DRPM*

NAME

R. Sanders

J. Shackelford

D. Chamberlain

T. Greene

DATE

09/11197

09/16/97

09116197

09/20/97 OFC

EMCB:DE*

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NAME

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E. Sullivan

B. Sheron

R. DennigI

DATE

9/23/97

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DATE

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DOCUMENT NAME: G:\\TAG\\INFAC

IN 97-XX

November XX, 1997 This information notice requires no specific action or written response. However, recipients

are reminded that they are required to consider industry-wide operating experience (including

NRC information notices) where practical, when setting goals and performing periodic

evaluations under Section 50.65, "Requirement for monitoring the effectiveness of

maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of Federal

Regulations. If you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation

(NRR) project manager.

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contact: J. Shackelford, RIV

817-860-8144 E-mail: jls2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC

TECH EDITOR*

RIV/DRS*by email

RIV/DRS*by email

PECB:DRPM*

NAME

R. Sanders

J. Shackelford

D. Chamberlain

T. Greene

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IN 97-XX

October XX, 1997 This information notice requires no specific action or written response. However, recipients

are reminded that they are required to consider industry-wide operating experience (including

NRC information notices) where practical, when setting goals and performing periodic

evaluations under Section 50.65, "Requirement for monitoring the effectiveness of.

maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of Federal

Regulations. If you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear Reactor Regulation

(NRR) project manager.

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contact:

J. Shackelford, RIV

817-8604144 E-mail: jls2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC

TECH EDITOR

RIVIDRS

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NAME

R. Sanders*

J. Shackelford

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IN 97-XX

September XX, 1997 This information notice requires no specifi action or written response. However, recipients

are reminded that they are required to

industry-wide operating experience (including

NRC information notices)

where practical, when setting goals and

performing periodic evaluations under Section 50.65, "Requirement for monitoring the

effectiveness of maintenance at nuclear power plants," to Part 50 of Title 10 of the Code of

Federal Regulations. If you have any questions about the information in this notice, please

contact the technical contact listed below or the appropriate Office of Nuclear Reactor

Regulation (NRR) project manager.

Jack W. Roe, Acting Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contact:

J. Shackelford, RIV

(7817-860-8144

_

E-mail: jls2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC

TECH EDITOR

RIV/DRS

RIV/DRS

l PECB:DRPM

NAME

R. Sanders 0

J. Shackelford

D. Chamberlain

T. Greene

l DATE

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