Information Notice 1997-17, Cracking of Vertical Welds in the Core Shroud and Degraded Repair

Cracking of Vertical Welds in the Core Shroud and Degraded Repair

ML031050352
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:	04/04/1997
From:	Martin T Office of Nuclear Reactor Regulation
To:
References
IN-97-017, NUDOCS 9704020035
Download: ML031050352 (10)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 April 4, 1997 NRC INFORMATION NOTICE 97-17: CRACKING OF VERTICAL WELDS IN THE CORE

SHROUD AND DEGRADED REPAIR

Addressees

All holders of operating licenses or construction permits for boiling-water reactors (BWRs).

Purpose

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

addressees to the discovery of cracks in vertical welds in the core shroud and degradation of

core shroud repairs at Nine Mile Point Nuclear Station, Unit I (NMPI). 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

Cracking of Vertical Welds

During the current refueling outage (March 1997), Niagara Mohawk Power Corporation, the

licensee for NMP1, was performing an augmented inservice inspection of welds in its

repaired core shroud in accordance with Boiling Water Reactor Vessel and Internals Project

(BWRVIP), "Guidelines for Reinspection of BWR Core Shrouds" (BWRVIP-07). On March 14,

1997, the licensee informed the NRC that it found significant cracking in vertical welds V9 and VI 0. (Welds V9 and VI 0 extend for 228.6 centimeters [90 inches] near the mid-plane of

the shroud). The indications were located in the heat-affected zones both on the outside

diameter and to a lesser extent on the inside diameter. Approximately two-thirds of the

length of these welds were cracked to a depth of 50 to 80 percent of the wall. As specified

by BWRVIP-07 criteria, the licensee expanded the inspection sample to include other vertical

shroud welds.

Niagara Mohawk had last examined vertical welds during the 1995 refueling outage as part of

its pre-modification inspection plan. At that time, the licensee performed enhanced visual

examinations from the inside-diameter surface of four vertical welds (V9, VI 0, VI1, and VI 2)

for a length of 15.2 centimeters [6 inches] near their intersection with the H5 circumferential

weld. No crack indications were found in these areas during the 1995 inspection or during

the current inspections.

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IN 97-17 April 4, 1997 Also, in the spring of 1996, Georgia Power Company (GPC) reported indications in vertical

core shroud welds VS and V6 at the Edwin I. Hatch Nuclear Plant, Unit 1. GPC conducted

the inspection in accordance with the guidance in BWRVIP-07. GPC reported two indications

of 5.1 centimeters [2 inches] and 30.5 centimeters [12 inches] in the V5 weld on the outside

diameter. They also reported one indication 81.3 centimeters [32 inches] long and four small

(3.05 centimeters [1.2 inches]) indications in V6 on the outside diameter. Inspections of the

inner diameter of both the V5 and V6 welds showed no cracking. A limited visual inspection

of 54.7 centimeters [18 inches] of the vertical welds V5 and V6 near the intersection with the

horizontal H4 welds in the fall 1994 outage had not revealed any cracks. At least a part of

the region of one of the indications that was found in 1996 in the V6 vertical weld had been

visually inspected in the fall 1994 outage and was found to be uncracked.

Degraded Repair at NMP1 Niagara Mohawk found the core shroud repair, which had been installed during the 1995 refueling outage, was degraded. The repair consisted of four pretensioned tie rods running

vertically from the top to the bottom of the core shroud. Inspections showed that the core

shroud lower wedge support was not in contact with the reactor vessel wall and the outside- diameter surface of the shroud as required. The function of this wedge support is to restrain

the shroud laterally during a seismic event, and it is held in place by a spring latch device

that failed on the tie rod at the .90-degree azimuth location. According to the licensee's

preliminary evaluation, the lack of contact could have affected the performance of the lower

wedge support during a postulated seismic event.

The failed latch (called a "retainer clip") in the lower part of the 90-degree tie rod assembly

resulted in shifting of the associated lateral support block downward to the end of the tie rod.

Visual inspection of the other three tie rod assemblies revealed some discoloration of latches

in the 270-degree and 350-degree tie rod assemblies, indicating possible degradation. The

lateral support block for the 35C-degree assembly was found to have shifted about 0.635 centimeter [1/4 inch] downward. The licensee is evaluating the potential consequences of a

postulated multiple loss of retainer clips.

The licensee also found the nut at the top of the 270-degree tie rod to be loose, although the

retaining device for the nut remained in place. The other three tie rod nuts will be checked

for tightness. It was also observed that the lateral support for the 270-degree tie rod

assembly, which was contacting the inner radial surface of a recirculation nozzle instead of

the vessel wall due to an initial mis-installation, had shifted slightly.

Discussion

In view of the extent and location of cracking at vertical core shroud welds observed at

NMP1, the BWRVIP intends to revise the shroud inspection guidance in BWRVIP-07. In the

interim, the BWRVIP has informed is members that enhanced visual examination of the core

shroud outer diameter in the high-fluence area is appropriate based on the vertical weld

cracking observed at Hatch 1 and NMP1.

IN 97-17 April 4, 1997 Niagara Mohawk is currently performing evaluations to determine if the degraded core shroud

repair would have performed satisfactorily during postulated seismic events and if the shroud

would have maintained its structural integrity under all design-basis events.

Related Generic Communications

NRC Information Notice 93-79, "Core Shroud Cracking at Beltline Region Welds in Boiling

Water Reactors," dated September 30, 1993.

NRC Information Notice 94-42, "Cracking in the Lower Region of the Core Shroud in Boiling

Water Reactors," dated June 7, 1994.

NRC Information Notice 94-42, Supplement 1, "Cracking in the Lower Region of the Core

Shroud in Boiling Water Reactors," dated July 19, 1994.

NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core Shrouds in

Boiling Water Reactors," dated July 25, 1994.

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

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

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

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: M. Banic, NRR

(301) 415-2771 E-mail: mjb@nrc.gov

C. E. Carpenter, Jr., NRR

(301) 415-2169 E-mail: cec@nrc.gov

Jai Rajan, NRR

(301) 415-2788 E-mail: jrrinrc.gov

Attachment: List of Recently II J NRC Information Notices

C 9 _puSeil ~

Attachment

IN 97-17 April 4, 1997 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

'Notice No. ' Subject Issuance Issued to

97-16 Preconditioning of 04/04/97 All holders of OLs

Plant Structures, or CPs for nuclear

Systems, and Components power reactors

Before ASME Code Inservice

Testing or Technical

Specification Surveillance

Testing

97-15 Reporting of Errors 04/04/97 All holders of OLs

and Changes in Large- or CPs for nuclear

Break Loss-of-Coolant power reactors and

Accident Evaluation all reactor fuel

Models of Fuel Vendors vendors

and Compliance with

10 CFR 50.46(a)(3)

97-14 Assessment of Spent 03/28/97 All holders of OLs

Fuel Pool Cooling or CPs for nuclear

power reactors

97-13 Deficient Conditions 03/24/97 All holders of OLs

Associated with Pro- or CPs for nuclear

tective Coatings at power reactors

Nuclear Power Plants

97-12 Potential Armature 03/24/97 All holders of OLs

Binding in General or CPs for nuclear

Electric Type HGA power reactors

Relays

92-27, Thermally Induced 03/21/97 All holders of OLs

Supp. 1 Accelerated Aging or CPs for nuclear

and Failure of ITE/ power reactors

Gould A.C. Relays

Used in Safety-Related

Applications

OL = Operating License

CP = Construction Permit

I I

- ~IN 97-17 April 4, 1997 Niagara Mohawk is currently performing evaluations to determine if the degraded core shroud

repair would have performed satisfactorily during postulated seismic events and if the shroud

would have maintained its structural integrity under all design-basis events.

Related Generic Communications

NRC Information Notice 93-79, "Core Shroud Cracking at Beltline Region Welds in Boiling

Water Reactors," dated September 30, 1993.

NRC Information Notice 94-42, "Cracking in the Lower Region of the Core Shroud in Boiling

Water Reactors," dated June 7, 1994.

NRC Information Notice 94-42, Supplement 1, "Cracking in the Lower Region of the Core

Shroud in Boiling Water Reactors," dated July 19, 1994.

NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core Shrouds in

Boiling Water Reactors," dated July 25, 1994.

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

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

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

original signed by

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: M. Banic, NRR C. E. Carpenter, Jr., NRR

(301) 415-2771 (301) 415-2169 E-mail: mjb@nrc.gov E-mail: cec@nrc.gov

Jai Rajan, NRR

(301) 415-2788 E-mail: jrr@nrc.gov

Tech Editor has reviewed and concurred on 03128/97 Attachment: List of Recently Issued NRC Information Notices

• see attached concurrences; MBanic per phonecon 3/28197 concurred on comments

DOCUMENT NAME: 97-17.IN

To receive a copy of this document. Indicate inthe box: C - Copy w/o

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OFFICE TECH CONT L C/PECB:DRPM I ID/RKPM l I

NAME MBanic* AChaffee* Tgartin

DATE 03/28/97 03/31/97 04// /97 OFFICIAL RECORD CO

IN 97-XX

April XX, 1997 Niagara Mohawk is currently performing evaluations to determine if the degraded core shroud

repair would have performed satisfactorily during postulated seismic events and if the shroud

would have maintained its structural integrity under all design-basis events.

Related Generic Communications

NRC Information Notice 93-79, "Core Shroud Cracking at Beltline Region Welds in Boiling

Water Reactors," dated September 30, 1993.

NRC Information Notice 94-42, "Cracking in the Lower Region of the Core Shroud in Boiling

Water Reactors," dated June 7, 1994.

NRC Information Notice 94-42, Supplement 1, "Cracking in the Lower Region of the Core

Shroud in Boiling Water Reactors," dated July 19, 1994.

NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core Shrouds in

Boiling Water Reactors," dated July 25, 1994.

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

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

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

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: M. Banic, NRR C. E. Carpenter, Jr., NRR

(301) 415-2771 (301) 415-2169 E-mail: mib~nrc.gov E-mail: cec@nrc.gov

Jai Rajan, NRR

(301) 415-2788 E-mail: jrr@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• see attached concurrences: MBanic oer Dhonecon 3128197 concurred on comments

OFC DE:EMCB DDlDE DIDE C/PECB:DRPM

NAME MBanic* l GLainas* BSheron* A. Chaffee*

DATE _3 /28 /97 L 3 128 97 13 /31/97 13 /31/97;

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1"7-XX

April XX, 1997 NRC Information Notice 94-42, Supplement 1, "Cracking in the Lower Region of the Core

Shroud in Boiling Water Reactors," dated July 19, 1994.

NRC Information Notice 94-42, "Cracking in the Lower Region of the Core Shroud in Boiling

Water Reactors," dated June 7, 1994.

NRC Information Notice 93-79, "Core Shroud Cracking at Beitline Region Welds in Boiling

Water Reactors," dated September 30, 1993.

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

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

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

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: M. Banic, NRR

301-415-2771 E-mail: mjbenrc.gov

C.E. Carpenter, Jr., NRR

301-415-2169 E-mail: cec@nrc.gov

Jai Rajan, NRR

301-415-2788 E-mail: jrr@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• see attached concurrences; MBanic per phonecon 3/28/97 concurred on comments

OFC DE:EMCB DD/DE DIDE C/PECB:DRPM

NAME MBanic* GLainas* BSheron* A. Chaffe____

DATE 3 /28 /97 _3 /28 /97 3 /31/97 3 51997 OFC D/DRPM

NAM T. Martin

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DATE I /97 OFFICAL RECORD CPY DOCUMENT NAME: G:%TAG\INVERT.2

IN 97-XX

April XX. 1997 postulated seismic events and if the shroud would have maintained its

structural integrity under all design-basis events.

Related Generic Communications

NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core

Shrouds in Boiling Water Reactors," dated July 25, 1994. -

NRC Information Notice 94-42, Supplement 1, "Cracking in the Low Region of

the Core Shroud in Boiling Water Reactors," dated July 19, 199 NRC Information Notice 94-42, "Cracking in the Lower Regi of the Core Shroud

in Boiling Water Reactors," dated June 7. 1994.

NRC Information Notice 93-79, "Core Shroud Cracking t Beltline Region Welds

in Boiling Water Reactors," dated September 30, 19 This information notice requires no specific af ion or written response. If

you have any questions about the informatio n this notice, please contact

one of the technical contacts listed below the appropriate Office of

Nuclear Reactor Regulation (NRR) project m ager.

Tho s T. Martin, Director

Di ision of Reactor Program Management

ifce of Nuclear Reactor Regulation

Technical contacts: M. Banic, RR

301-415- 71 E-mail* mjb@nrc.gov

C.E Carpenter, Jr., NRR

30 -415-2169 mail: cec@nrc.gov

Jai Rajan

301-415-2788 E-mail: jrr@nrc.gov

Attachment: Lis of Recently Issued NRC Information Notices

• see attached oncurrences: MBanic per phonecon 3/28/97 concurredOD on

comments

OFC DADMCB DD/DE D/DE C/PECB:DRPM

NAME ABanic* GLainas* BSheron* A. Chaffee -

DATE/ 3 /28 /97 3 /28 /97 3/31/97 / /97 VC D/DRPM

INAAE T.Martin

DATE / /97 OFFICIAL RECORD COPY] DOCUMENT NAME: G:\TAG\INVERT.2

11. - IN 97-XX

April XX, 1997 Related Generic Communications

NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core

Shrouds in Boiling Water Reactors," dated July 25, 1994.

NRC Information Notice 94-42, Supplement 1, "Cracking in the Lower Region of

the Core Shroud in Boiling Water Reactors," dated July 19. 1994.

NRC Information Notice 94-42, "Cracking in the Lower Region of e Core Shroiid

in Boiling Water Reactors," dated June 7, 1994.

NRC Information Notice 93-79, "Core Shroud Cracking at Bel ne Region Welds

in Boiling Water Reactors," dated September 30, 1993.

This information notice requires no specific action o written response. If

you have any questions about the information in thi notice, please contact

one of the technical contacts listed below or the propriate Office of

Nuclear Reactor Regulation (NRR) project manager

Thomas . Martin, Director

Divis n of Reactor Program Management

Off e of Nuclear Reactor Regulation

Technical contacts: M. Banic, NR

301-415-277 E-mail: b@nrc.gov

C.E. C penter, Jr., NRR

301- 5-2169 E-m 1: cec@nrc.gov

Jai Rajan

301-415-2788 E-mail: jrr@nrc.gov

Attachment: Lis of Recently Issued NRC Information Notices

• see attached ncurrences; MBanic per phonecon 3/28/97 concurred on

commentst/

FC DEXMCB l IDD/DED l C/PECB:DRPM

NAME Aanic* GLainas* BS_ A. Chaffee

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NAME T. Martin

DATE I/ /97

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DOCUMENT NAME: G:\TAG\INVERT.2

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April XX, 1997 Related Generic Communications

NRC Generic Letter 94-03, "Intergranular Stress Corrosion Cracking of Core

Shrouds in Boiling Water Reactors." dated July 25, 1994.

NRC Information Notice 94-42. Supplement 1, "Cracking inthe Lower Region of

the Core Shroud in Boiling Water Reactors." dated July 19. 1994.

NRC Information Notice 94-42, "Cracking in the Lower Region of the Core Shroud

inBoiling Water Reactors," dated June 7. 1994.

NRC Information Notice 93-79. "Core Shroud Cracking at Beltline Region Welds

in Boiling Water Reactors," dated September 30, 1993.

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

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: M. Banic, NRR

301-415-2771 E-mail: mjb@nrc.gov

C.E. Carpenter, Jr., NRR

301-415-2169 E-mail: cec@nrc.gov

Jai Rajan

301-415-2788 E-mail: jrr@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

OFC PECB:DRPM DE:EMCB D/DE IF C/PECB:DRPM

NAME Greene 9/7 MBanic 9 GLainaso i- A. Chaffee

DATE 3 /IV/97 1 I//97 3 /9/97 Y/' / /97

422* 3 OFC D/DRPM

NAME T.Martin

DATE / /97 j

[OFFICIAL RECORD COPY]

DOCUMENT NAME: G:\TAG\INVERT.2