Information Notice 1985-65, Crack Growth in Steam Generator Girth Welds

Crack Growth in Steam Generator Girth Welds

ML031180225
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, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	07/31/1985
From:	Jordan E NRC/IE
To:
References
IN-85-065, NUDOCS 8507290456
Download: ML031180225 (5)

SSINS No.: 6835 IN 85-65 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 July 31, 1985 IE INFORMATION NOTICE NO. 85-65: CRACK GROWTH IN STEAM GENERATOR

GIRTH WELDS

Addressees

All nuclear power pressurized water reactor (PWR) facilities holding an operat- ing license (OL) or a construction permit (CP).

Purpose

This information notice is provided to alert recipients of a potentially

significant problem pertaining to the growth in indications in steam generator

circumferential welds. Ultrasonic examination had determined previously that

the welds were acceptable. It is suggested that recipients review the informa- tion for applicability to their facilities and consider actions, if appropri- ate, to preclude a similar problem occurring at their facilities. However, suggestions contained in this information notice do not constitute NRC require- ments; therefore, no specific action or written response is required.

The NRC is continuing to evaluate pertinent information. An additional notifi- cation will be made if specific actions are determined to be required.

Description of Circumstances

In 1982 Indian Point Station Unit 3 had a leak at weld No. 6 on one of their

steam generators (see Information Notice 82-37). Weld No. 6 is a full- penetration circumferential weld located in the transition zone between

the tube bundle and steam dryer areas, below the feedwater nozzles, and

subject to thermal cycling. The crack was started by corrosion and operating

temperature fluctuations caused it to grow through the wall because of low-cycle

fatigue. The repair method reduced the defects to an acceptable level.

Ultrasonic examinations have been performed during outages since 1982 and in

the summer of 1985. Previously known indications that appear to have grown in

size are being evaluated.

In 1983 Surry Power Station Unit 2 performed ultrasonic examinations of the

No. 6 welds. The original construction weld at Unit 2 is 6 inches above the

weld that attached the lower portion of all three replacement steam generators

in 1980 (see attached sketch). The examination showed widespread indications

of discontinuities on the inside surface of this weld in the "A" steam genera- tor. None of the indications seemed large enough to be rejected and it was

8507290456

IN 85-65 July 31, 1985 decided that they were surface blemishes of reflections from weld geometry. In

March 1985, an ultrasonic reexamination was performed on the original construc- tion weld at Surry and larger, but acceptable, discontinuities were found in

the same locations. The inside surface of the weld in generator A was

visually examined, but no defects were seen. However, when magnetic particle

testing was performed at the request of the NRC, closely spaced linear cracks

were found over a large portion of the circumference. The appearance of these

cracks was similar to those at Indian Point. The safety significance is that

substantial loss of secondary coolant could occur without warning if cracking

degradation continued undetected.

The cracks in generator A were in a narrow band at the upper edge of the weld

and covered almost the entire inside diameter. The cracks were as deep as 1/2 inch and were covered by the surface oxide, which obscured detection by visual

examination. Generators B and C had numerous, smaller, circumferential cracks

in the same location. To complicate matters, there were 10 unacceptable

subsurface indications in generator B, based on the requirements of ASME

Section XI, IWB-3511. After a fracture and fatigue evaluation, these subsur- face indications were accepted by ASME IWB-3600. The surface cracks in all

three generators were removed by grinding; repair welding was not necessary.

Weld No. 6 was made on-site and had high residual stresses as a result of the

low preheat and postweld heat treatment temperatures. The steel in the vicini- ty of the weld pitted when the secondary water contained high oxygen concen- trations (higher than 25 ppb) and contaminants such as chlorides and copper

ions. In addition to internal pressure, this portion of the steam generator

has a change in cross-section and undergoes thermal cycling. Heat treatment of

the nearby replacement weld in 1980 reduced the residual stresses, but could

not undo any existing damage to the original construction weld. The cracks ran

from pit to pit and grew to an unacceptable size in less than one inspection

period.

At the next outage, the No. 6 welds in all three steam generators at Surry Unit

2 will be partially examined by magnetic particle testing. The subsurface

indications in generator B also will be examined by ultrasonic methods. Slow

growing corrosion cracks are irregular in length and depth. When the cracks

are located in the fusion line between the weld and the base metal, evaluation

is very difficult by ultrasonic methods alone. Magnetic particle testing is

more sensitive than visual examination and supplements ultrasonic examinations

where there is a possibility of surface defects. ASME Section XI specifies the

maximum allowable planar indications and the methods of examination, but these

methods may not be sufficient to identify indications and defects in all cases.

Additional surface preparation, calibration notches, personnel training, and

smaller ultrasonic probes may result in a better understanding of the ultrason- ic indications.

IN 85-65 July 31, 1985 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

ar L. Jordan Director

Division of Eme gency Preparedness

and Engineering Response

Office of Inspection and Enforcement

P. Cortland, IE

(301) 492-4175 Attachments:

1. Sketch of Steam Generator

2. List of Recently Issued IE Information Notices

Attachment 1 IN 85-65 July 31, 1985 Sketch Showing Steam Generator A

ORIGINAL

CONSTRUCTION

_- WELD N006

/ 9980 WELD

6 N. THAT ATTACHED

THE REPLACEMENT

STEAM GENERATORS

V,

Attachment 2 IN 85-65 July 31, 1985 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

85-64 BBC Brown Boveri Low-Voltage 7/26/85 All power reactor

K-Line Circuit Breakers, With facilities holding

Deficient Overcurrent Trip an OL or CP

Devices Models OD-4 and 5

85-63 Potential for Common-Mode 7/25/85 All power reactor

Failure of Standby Gas Treat- facilities holding

ment System on Loss of Off- an OL or CP

Site Power

85-62 Backup Telephone Numbers to 7/23/85 All power reactor

the NRC Operations Center facilities holding

an OL and certain

fuel facilities

85-61 Misadministrations to Patients 7/22/85 All power reactor

Undergoing Thyroid Scans facilities holding

an OL and certain

fuel facilities

85-60 Defective Negative Pressure 7/17/85 All power reactor

Air-Purifying, Fuel Facepiece facilities holding

Respirators an OL or CP

85-59 Valve Stem Corrosion Failures 7/17/85 All power reactor

facilities holding

an OL or CP

85-58 Failure Of A General Electric 7/17/85 All power reactor

Type AK-2-25 Reactor Trip facilities designed

Breaker by B&W and CE holding

an OL or CP

85-57 Lost Iridium-192 Source 7/16/85 All power reactor

Resulting In The Death Of facilities holding

Eight Persons In Morocco an OL or CP; fuel

facilities; and

material licensees

85-56 Inadequate Environment 7/15/85 All power reactor

Control For Components And facilities holding

Systems In Extended Storage an OL or CP

Or Layup

OL = Operating License

CP = Construction Permit