ML17059B477

Summary of 970320 Telcon W/Util to Discuss Licensee Current Observations from Insp of Core Shroud Vertical Welds & Tie Rod Assemblies in Progress at Plant,Unit 1

ML17059B477
Person / Time
Site:	Nine Mile Point
Issue date:	03/24/1997
From:	Hood D NRC (Affiliation Not Assigned)
To:	NRC (Affiliation Not Assigned)
References
TAC-M98170, NUDOCS 9703270212
Download: ML17059B477 (30)

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555<001 March 24, 1997 LICENSEE:

Niagara Hoh wk Power Corporation

-FACILITY:

Nine Mile Point Nuclear Station Unit No.

1

SUMMARY

OF TELEPHONE CONVERSATION OF MARCH 20,

1997, ON CORE SHROUD INSPECTION "BSERVATIONS (TAC NO. M98170}

On March 20, 1997, the NRC staff participated in a telephone conference call with Niagara Mohawk Power Corporation (NMPC and licensee) to discuss the licensee's current observations from inspections of core shroud vertical welds and tie rod assemblies (also called core shroud stabilizers) that are in progress at Nine Hile Point Nuclear Station, Unit 1.

Participants are listed in Enclosure l.

Enclosure 2, which includes the agenda and handouts,

'was faxed to the NRC by the licensee prior to the telephone conference.

BACKGROUND The telephone conference results from the following prior notifications that the licensee provided in accordance with 10 CFR 50.72(b):

l.

On March 14, 1997, the licensee notified the NRC that as a result of augmented in-service inspection of the core shroud in accordance with Boiling Water Reactor Vessel Internal Project (BWRVIP07), "Guidelines for Reinspection of BWR Core Shrouds,"

as authorized by the NRC staff by letter dated March 3, 1997, weld indications (cracks) have been found in a significant portion of vertical welds V9 and V10.

The indications were observed in.the heat affected zones on the outside diameter.

Consequently, the licensee would expand the inspection sample to determine the extent of cracking of other vertical welds in accordance with BWRVIP07 criteria and would perform engineering assessments of the results to assess the acceptability of the cracking and any safety implications.

The licensee also noted that all fuel 'is in the spent fuel pool at this time.

2.

On March 19, 1997, the licensee reported that a core shroud lower tie rod assembly lateral contact, whose function is to restrain the shroud laterally during a seismic event, was not contacting the reactor vessel wall and outside diameter shroud surface as required (see ).

The lower contact is supposed to be held by a spring latch device, but inspection revealed that the latch had failed on the tie rod assembly located at the 90'zimuth.

The spring latch devices for the 270'nd 350'ie rod assemblies were observed to exhibit signs of degradation.

The tie rod assemblies had been installed during the previous refueling outage in 1995.

The licensee will perform engineering evaluations of the lack of contact for the seismic event and assess the affect on shroud integrity.

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DISCUSSION The licensee has formed a Shroud f ". oject Team to assess the inspection results and root cause of the NHPI core shroud deficiencies, interface with industry and

NRC, recommend a course of action, and assist with obtaining NRC concurrence regarding any changes to the shroud modification designs or inspection plans previously approved by the NRC.

In addition to NHPC engineering and management personnel, the team includes the BWRVIP Executive Chairman and BWRVIP Inspection Chairman (who are also employees of NHPC),

and several General Electric employees.

The licensee provided Indication Maps showing the extent and depth of flaws during ultrasonic examination of shroud welds V9 and V10 (see pages 2 through 4 of Enclosure 2, handouts).

These maps show that the deeper cracks were observed from the shroud outer diameter and are concentrated in the upper third of the height of welds V9 and V10.

No through-wall cracks were found and the maximum flaw depth was 82 percent for V9 and 66 percent for V10.

All

~vertical welds are being inspected by a combination of ultrasonic or visual

means, depending upon accessibility.

Welds are being located by use of an eddy current technique.

The latch (called a "retainer clip" on page 7 of Enclosure 2, handouts) in the lower portion of the 90'ie rod assembly wasobserved to be missing and the associated lateral support block had shifted downward until encountering a

retaining pin.

Visual inspection of the other three tie rod assemblies revealed apparent degradation (i.e., "discoloration" ) of latches in the 270'nd 350'ie rod assemblies.

The lateral support block for the 350'ssembly has shifted downward about I/O inch.

The licensee is preparing a

Deviation/Events Report on the latches and evaluating the potential consequences of a postulated multiple loss of retainer clips.

The licensee also found that the nut at the top of the 270'ie rod had loosened

somewhat, although the retaining device for the nut remained in place.

The other three tie rod nuts will be checked for tightness.

The lateral support for the 270'ie rod assembly, which was contacting the recirculation blend nozzle and was scheduled for replacement, was observed to have shifted slightly.

The licensee noted that the current restart schedule for Unit I is April 9, 1997, but will be adjusted as needed.

Upon completion of inspections and evaluations, the licensee. will develop corrective actions.

The licensee plans to address any changes associated with the 1995 shroud repair that was designed as an alternative to the requirements of the American Society of Mechanical Engineers (ASHE) Boiler and Pressure Vessel Code pursuant to 10 CFR 50.55a(a)(3)(i) as approved by the NRC staff by letters dated March 31,

1995, and March 3,

1997, and request NRC staff approval for these changes or any significant change in the core shroud reinspection plan.

The NRC staff requested that the licensee provide a followup telephone conference call upon completion of the inspections.

The NRC staff also requested that the licensee meet with the NRC to discuss'esults of its technical evaluations, root cause assessment, and plans for corrective actions prior to restart of Unit 1.

The NRR Project Manager will schedule the conference call and meeting upon the licensee's request.

Sincerely, Docket No. 50-220 Darl S.

Hood, Senior Project Manager.

Project Directorate I-I Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation

Enclosures:

1.

Participants 2.

Agenda and Handouts 3.

Core Shroud Stabilizers cc:

See next page

I I

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B. Ralph Sylvia Niagara Mohawk Power Corporation Nine Mile,Point Nuclear Station Unit No.

1 CC:

Mr. Richard B. Abbott Vice President and General Manager-Nuclear Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station P.O.

Box 63

Lycoming, NY 13093 Hr. Hartin J.

McCormick, Jr.

Vice President Nuclear Safety Assessment and Support Niagara Mohawk Power Corporation Nine Hile Point Nuclear Station P.O.

Box 63

Lycoming, NY 13093 Hs. Denise J. Wolniak Manager Licensing Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station P.O.

Box 63

Lycoming, NY 13093 Hr. Kim A. Dahlberg General Hanager - Projects Niagara Mohawk Power Corporation Nine Mile Point Nuclear Station P.O.

Box 63

Lycoming, NY 13093 Hr. Norman L. Rademacher Plant Manager, Unit 1

Nine Mile Point.Nuclear Station P.O.

Box 63

Lycoming, NY 13093 Regional Administrator, Region. I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Resident Inspector U.S. Nuclear Regulatory Commission P.O.

Box 126

Lycoming, NY 13093 Charles Donaldson, Esquire Assistant Attorney General New York Department of Law 120 Broadway New York, NY 10271 Hr. Paul D. Eddy State of New ",ork Department of Public Service Power Division, System Operations 3 Empire State Plaza

Albany, NY 12223 Mr. F. William Valentino, President New York State

Energy, Research, and Development Authority Corporate Plaza West 286 Washington Avenue Extension

Albany, NY 12203-6399 Hark J. Wetterhahn, Esquire Winston 5 Strawn 1400 L Street, NW Washington, DC 20005-3502 Gary D. Wilson, Esquire Niagara Mohawk Power Corporation 300 Erie Boulevard West

Syracuse, NY 13202 Supervisor Town of Scriba Route 8, Box 382

Oswego, NY 13126

PARTICIPANTS March 20, 1997 NMPC R. Abbott M. McCormick C. Terry N. Rademacher S.

Leonard D. Harrison R. Corieri T. Oldfield G. Inch W. Yager D. Baker J. Hetninway (GE)

J. Charnley (GE) et al.

NRC G. Lainas R.

Wessman R.

Herman J. Strosnider K. Wickman R.

Frahm Sr.

T. Green J.

Rajan M. Banic D. Hood W. Gleaves G. Carpenter B. Sheron et al.

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IJ The NRC staff requested that the licensee provide a followup telephone conference call upon completion of the inspections.

The NRC staff also requested that the licensee meet with the NRC to discuss results of its technical evaluations, root cause assessment, and plans for corrective actions prior to restart of Unit 1.

The NRR Project Manager will schedule the conference call and meeting upon the licensee's request.

Sincerely, Docket No. 50-220

/s/

Darl S.

Hood, Senior Project Manager Project Directorate I-1 Division of Reactor Projects I/II Office of Nuclear Reactor Regulation

Enclosures:

1.

Participants 2.

Agenda and Handouts 3.

Core Shroud Stabilizers cc:

See next page DISTRIBUTION'Hard Co Docket File PUBLIC PDI-1 Reding, OGC ACRS E-Mail S. Collins/F. Miraglia R.

Zimmerman S.

Varga J. Zwolinski S.

Bajwa D.

Hood S. Little D.

Ross G. Lainas R.

Wessman R.

Herman J.. Strosnider K. Wickman R.

Frahm, Sr.

T. Green J.

Rajan M. Bani W. Gleaves G. Carpenter B. Sheron K. Manoly C. Cowgill, RI L. Doerflein, RI W. 'Dean, EDO G. Holahan DOCUMENT NAME:

G: iNMPliNMP198170. TEL To receive a copy of this document, indicate in the box:.

"C" = Copy without

, attachment enclosure "E"

Co y with attachment/enclosure "N" = No co y OFFICE NAME PM:PDI-1 DNood/ra I LA:PDI-1 sLIttla D:PDI-1 SBajNa DATE 03/

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03/40/97 0 f>c>a Recor Copy 03/

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