ML082100120

Evaluation Regarding the Steam Generator Tube Inspection Reports for the 2007 (IR14) Outage

ML082100120
Person / Time
Site:	Diablo Canyon
Issue date:	08/01/2008
From:	Wang A NRC/NRR/ADRO/DORL/LPLIV
To:	Conway J Pacific Gas & Electric Co
Wang, A B, NRR/DORL/LPLIV, 415-1445
References
GL-04-002, TAC MD6690
Download: ML082100120 (5)

Text

August 1, 2008

Mr. John Conway

Senior Vice President - Station

Generation and Chief Nuclear Officer

Pacific Gas and Electric Company

Diablo Canyon Power Plant

P.O. Box 770000

San Francisco, CA 94177-0001

SUBJECT:

DIABLO CANYON POWER PLANT, UNIT NO. 1- EVALUATION REGARDING THE STEAM GENERATOR TUBE INSPECTION REPORTS FOR THE 2007

(1R14) OUTAGE (TAC No.: MD6690)

Dear Mr. Conway:

By letters dated August 27, 2007 (Agencywi de Documents Access and Management System (ADAMS) Accession Nos. ML072420339 and ML072470561), November 26, 2007 (ML073390290), and June 6, 2008 (ADAMS Accession No. ML081700278), Pacific Gas and

Electric Company (PG&E, the licensee), submitt ed information summarizing the results of the 2007 steam generator (SG) tube inspections at Diablo Canyon Power Plant, Unit No. 1 (DCPP-

1). These inspections were performed during the fourteenth refueling outage (1R14). In

addition to these reports, the U.S. Nuclear Regulatory Commission (NRC) staff summarized

additional information concerning the 2007 SG tube inspections at DCPP-1 in an NRC letter to

DCPP-1 dated August 8, 2007 (ADAMS Accession No. ML072130034).

The NRC staff has completed its review of these reports and concludes that the licensee

provided the information required by their technical specifications. The NRC staff review of the

reports is enclosed.

If you have any questions regarding this matter, please contact me at (301) 415-1445.

Sincerely,

/RA by Jack Donohew for/

Alan B. Wang, Project Manager

Plant Licensing Branch IV

Division of Operating Reactor Licensing

Office of Nuclear Reactor Regulation

Docket No. 50-275

cc: See next page

ML081700278), Pacific Gas and

Electric Company (PG&E, the licensee), submitt ed information summarizing the results of the 2007 steam generator (SG) tube inspections at Diablo Canyon Power Plant, Unit No. 1 (DCPP-

1). These inspections were performed during the fourteenth refueling outage (1R14). In

addition to these reports, the U.S. Nuclear Regulatory Commission (NRC) staff summarized

additional information concerning the 2007 SG tube inspections at DCPP-1 in an NRC letter to

DCPP-1 dated August 8, 2007 (ADAMS Accession No. ML072130034).

The NRC staff has completed its review of these reports and concludes that the licensee

provided the information required by their technical specifications. The NRC staff review of the

reports is enclosed.

If you have any questions regarding this matter, please contact me at (301) 415-1445.

Sincerely,

/RA by Jack Donohew for/

Alan B. Wang, Project Manager

Plant Licensing Branch IV

Division of Operating Reactor Licensing

Office of Nuclear Reactor Regulation

Docket No. 50-323

cc: See next page

DISTRIBUTION

PUBLIC LPLIV Reading RidsNrrPMAWang Resource RidsNrrDorl Resource RidsNrrLAGLappert RidsNrrDorlLpl4 Resource RidsAcrsAcnwMailCenter Resource RidsRegion4MailCenter Resource RidsOgcRp Resource KKarwoski

ACCESSION NO.:

ML082100120

• memo OFFICE LPL4/PM LPL4/LA CSGB/BC LPL4/BC (A)

LPL4/PM NAME AWang JDonohew for GLappert AHiser* MThadani AWang JDonohew for DATE 7/31/08 7/30/08 07/18/08 8/01/08 8/01/08

U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGUALTION

SUMMARY

OF STAFF REVIEW OF 2007 STEAM GENERATOR TUBE INSPECTIONS DIABLO CANYON POWER PLANT, UNIT NO. 1 TAC No. MD6690 DOCKET No. 50-275 By letters dated August 27, 2007 (Agencywi de Documents Access and Management System (ADAMS) Accession Nos. ML072420339 and ML072470561), November 26, 2007 (ADAMS

Accession No. ML073390290), and June 6, 2008 (ADAMS Accession No. ML081700278),

Pacific Gas and Electric Company (PG&E, the licensee) submitted information summarizing the

results of the 2007 steam generator (SG) tube inspections at Diablo Canyon Power Plant, Unit

No. 1 (DCPP-1). These inspections were performed during the fourteenth refueling outage

(1R14). In addition to these reports, the U.S. Nuclear Regulatory Commission (NRC) staff

additional information concerning the 2007 SG tube inspections at DCPP-1 in an NRC letter to

DCPP-1 dated August 8, 2007 (ADAMS Accession No. ML072130034).

The SGs at DCPP-1 are Westinghouse model 51 SGs. Each SG contains 3,388 mill-annealed

Alloy 600 tubes. Each tube has a nominal outside diameter of 0.875 inch and a nominal wall

thickness of 0.050 inch. The tubes are supported by a number of carbon steel tube support

plates and Alloy 600 anti-vibration bars. The tubes were explosively expanded into the

tubesheet at both ends for the full length of the tubesheet.

The licensee provided the scope, extent, methods, and results of their SG tube inspections in

the documents referenced above. In addition, the licensee described corrective actions (i.e., tube plugging) taken in response to the inspection findings.

As a result of the review of the reports, the NRC staff has the following comments/observations:

No crack-like flaws have ever been identified in the tubes at cold-leg tube support plate

elevations where distorted outside diameter bobbin indicators have been reported.

Approximately 31 percent of the inferred bobbin voltages (from the rotating probe data) were

non-conservative when compared to the measured bobbin voltages. Some of these indications

had measured bobbin voltages of approximately 2 volts.

Sludge lancing was not performed during the 2007 outage, in part, because of the small amount

of sludge removed during the previous outage (1R13) and the chemical cleaning performed in

the 1R12 outage in which about 19,000 pounds of sludge and scale were removed from the

steam generators.

A detailed review of the condition monitoring and operational assessment was not performed for

the degradation mechanisms that are not addressed by an alternate tube repair criteria (such as

axial primary water stress corrosion cracking indications at tube support plate elevations).

However, the results of these assessments appear reasonable given the plug-on-detection

approach for crack-like indications and past inspection results.

The 2007 steam generator tube inspections were the last planned tube inspections for these

steam generators since the licensee plans to replace them during their next DCPP-1 outage (in

2009).

Based on a review of the information provided, the NRC staff concludes that the licensee

provided the information required by their technical specifications. In addition, the NRC staff

concludes that there are no technical issues that warrant follow-up action at this time since the

inspections appear to be consistent with the objective of detecting potential tube degradation

and the inspection results appear to be consistent with industry operating experience at similarly

designed and operated units.

Diablo Canyon Power Plant, Units 1 and 2

cc:

NRC Resident Inspector

Diablo Canyon Power Plant

c/o U.S. Nuclear Regulatory Commission

P.O. Box 369

Avila Beach, CA 93424

Sierra Club San Lucia Chapter

ATTN: Andrew Christie

P.O. Box 15755

San Luis Obispo, CA 93406

Ms. Nancy Culver

San Luis Obispo

Mothers for Peace

P.O. Box 164

Pismo Beach, CA 93448

Chairman San Luis Obispo County Board of

Supervisors

Room 370 County Government Center

San Luis Obispo, CA 93408

Mr. Truman Burns

Mr. Robert Kinosian

California Public Utilities Commission

505 Van Ness, Room 4102

San Francisco, CA 94102

Diablo Canyon Independent Safety

Committee

ATTN: Robert R. Wellington, Esq.

Legal Counsel

857 Cass Street, Suite D

Monterey, CA 93940

Regional Administrator, Region IV

U.S. Nuclear Regulatory Commission

Harris Tower & Pavillion

612 E. Lamar Blvd, Suite 400 Arlington, TX 76011-4125

Richard F. Locke, Esq.

Pacific Gas & Electric Company

P.O. Box 7442

San Francisco, CA 94120

City Editor The Tribune

3825 South Higuera Street

P.O. Box 112

San Luis Obispo, CA 93406-0112

Mr. Ed Bailey, Chief

Radiologic Health Branch

State Department of Health Services

P.O. Box 997414 (MS 7610)

Sacramento, CA 95899-7414

Mr. James D. Boyd, Commissioner

California Energy Commission

1516 Ninth Street (MS 31)

Sacramento, CA 95814

Mr. James R. Becker, Vice President

Diablo Canyon Operations

and Station Director

Diablo Canyon Power Plant

P.O. Box 3

Avila Beach, CA 93424

Jennifer Tang

Field Representative

United States Senator Barbara Boxer

1700 Montgomery Street, Suite 240

San Francisco, CA 94111