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

Technical

Contact: 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

6 N._- WELD N0 0 6/ 9980 WELD THAT ATTACHED THE REPLACEMENT

STEAM GENERATORS

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 85-63 BBC Brown Boveri Low-Voltage

K-Line Circuit Breakers, With Deficient

Overcurrent

Trip Devices Models OD-4 and 5 Potential

for Common-Mode

Failure of Standby Gas Treat-ment System on Loss of Off-Site Power Backup Telephone

Numbers to the NRC Operations

Center 7/26/85 7/25/85 7/23/85 85-62 85-61 85-60 Misadministrations

to Patients 7/22/85 Undergoing

Thyroid Scans Defective

Negative Pressure 7/17/85 Air-Purifying, Fuel Facepiece Respirators

Valve Stem Corrosion

Failures 7/17/85 Failure Of A General Electric 7/17/85 Type AK-2-25 Reactor Trip Breaker All power reactor facilities

holding an OL or CP All power reactor facilities

holding an OL or CP All power reactor facilities

holding an OL and certain fuel facilities

All power reactor facilities

holding an OL and certain fuel facilities

All power reactor facilities

holding an OL or CP All power reactor facilities

holding an OL or CP All power reactor facilities

designed by B&W and CE holding an OL or CP All power reactor facilities

holding an OL or CP; fuel facilities;

and material licensees All power reactor facilities

holding an OL or CP 85-59 85-58 85-57 Lost Iridium-192 Source Resulting

In The Death Of Eight Persons In Morocco Inadequate

Environment

Control For Components

And Systems In Extended Storage Or Layup 7/16/85 7/15/85 85-56 OL = Operating

License CP = Construction

Permit