ML031330357

Letter, Steam Generator Tube Inservice Inspection Telephone Conference

ML031330357
Person / Time
Site:	Diablo Canyon
Issue date:	05/13/2003
From:	Jaffe D NRC/NRR/DLPM/LPD4
To:	Rueger G Pacific Gas & Electric Co
Jaffe D, NRR/DLPM, 415-1439
References
TAC MB5152
Download: ML031330357 (5)

Text

May 13, 2003 Mr. Gregory M. Rueger Senior Vice President, Generation and Chief Nuclear Officer Pacific Gas and Electric Company Diablo Canyon Power Plant P.O. Box 3 Avila Beach, CA 93424

SUBJECT:

DIABLO CANYON POWER PLANT, UNIT NO. 1 - STEAM GENERATOR TUBE INSERVICE INSPECTION TELEPHONE CONFERENCE (TAC NO. MB5152)

Dear Mr. Rueger:

The NRC staff informed Pacific Gas and Electric Company (PG&E) that a telephone conference would be held with PG&E to discuss the ongoing results of the steam generator (SG) tube inspections to be conducted during the Spring 2002, Diablo Canyon Power Plant, Unit No. 1, refueling outage. The staff stated that the telephone conference would be scheduled after the majority of the tubes had been inspected, but before the SG inspection activities had been completed. The staff indicated their plans to document the telephone conference, as well as any material that PG&E may provide to the NRC staff in support of the telephone call via a brief summary.

The enclosure represents a summary of the telephone conference held on May 20, 2002, in which ongoing results of the SG tube inspections conducted during the refueling outage were discussed. The material received from PG&E prior to this telephone conference is attached to the enclosed summary of the conference call.

Sincerely,

/RA/

David H. Jaffe, Acting Project Manager, Section 2 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-275

Enclosure:

Summary of Conference Call cc w/encl: See next page

ML NRR-106 OFFICE PDIV-2/PM PDIV-2/LA PDIV-2/SC NAME DJaffe EPeyton SDembek DATE 5/12/03 5/13/03 5/13/03 Diablo Canyon Power Plant, Units 1 and 2 cc:

NRC Resident Inspector Richard F. Locke, Esq.

Diablo Canyon Power Plant Pacific Gas & Electric Company c/o U.S. Nuclear Regulatory Commission P.O. Box 7442 P.O. Box 369 San Francisco, CA 94120 Avila Beach, CA 93424 Mr. David H. Oatley, Vice President Mr. Pete Wagner and General Manager Sierra Club California Diablo Canyon Power Plant 2650 Maple Avenue P.O. Box 56 Morro Bay, California 93442 Avila Beach, CA 93424 Ms. Nancy Culver City Editor San Luis Obispo The Tribune Mothers for Peace 3825 South Higuera Street P.O. Box 164 P.O. Box 112 Pismo Beach, CA 93448 San Luis Obispo, CA 93406-0112 Chairman Mr. Ed Bailey, Radiation Program Director San Luis Obispo County Board of Radiologic Health Branch Supervisors State Department of Health Services Room 370 P.O. Box 942732 (MS 178)

County Government Center Sacramento, CA 94234-7320 San Luis Obispo, CA 93408 Mr. James D. Boyd, Commissioner Mr. Truman Burns California Energy Commission Mr. Robert Kinosian 1516 Ninth Street (MS 31)

California Public Utilities Commission Sacramento, CA 95814 505 Van Ness, Room 4102 San Francisco, CA 94102 Mr. James R. Becker, Vice President Diablo Canyon Operations Diablo Canyon Independent Safety and Station Director Committee Diablo Canyon Power Plant ATTN: Robert R. Wellington, Esq. P.O. Box 3 Legal Counsel Avila Beach, CA 93424 857 Cass Street, Suite D Monterey, CA 93940 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower & Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064

SUMMARY

OF CONFERENCE CALL BETWEEN THE NRC STAFF AND PACIFIC GAS AND ELECTRIC COMPANY REGARDING THE 2002 STEAM GENERATOR INSPECTION RESULTS DIABLO CANYON UNIT 1 DOCKET NO. 50-275 The NRC staff participated in a conference call with Pacific Gas and Electric Company (PG&E/the licensee) representatives on May 20, 2002, to discuss the ongoing steam generator (SG) inspection activities at Diablo Canyon Unit 1. The licensee provided supporting information which is attached.

At the time of the call, data acquisition and analyses were complete. Details of the licensees initial inspection scope and expansion criteria are described in the licensees written materials.

Several of these topics were discussed during the conference call.

- In the U-bend region, 100 percent of the tubes in Rows 1 and 2, plus 20 percent of the tubes in Row 3, were inspected with a rotating probe coil (RPC) equipped with a Plus point (+Pt) coil. The expansion of the inspection to Row 3 of the U-bends is due to a recent report of low-row U-bend indications found in other plants.

- Of the approximately 150 tubes deplugged during the outage, no tubes exhibited any swelling.

- Although minor primary-to-secondary leakage was observed during the cycle, no through-wall flaws were detected nor were any leaking plugs identified during the visual inspection.

- The scope of the plus-point coil inspections of dents at the tube support plate differ from steam generator to steam generator since the extent of denting and the cracking observed varies from steam generator to steam generator.

- The licensee indicated that all tubes which were not expanded in the tubesheet (i.e.,

NTEs) were plugged.

- The selection of which dings to inspect was random (i.e., the size of the ding was not used in the selection criteria).

The licensee provided a table in the attached material summarizing the inspection findings.

Several of the items in the table were clarified during the conference call, as discussed below.

W* Alternate Repair Criteria (ARC) (Axial indications in the WEXTEX region inside tubesheet):

There was one axial primary water stress corrosion cracking (PWSCC) indication which failed to meet the W* criteria. This was a new indication (i.e., was not detected or present in the previous inspections).

During this outage, no in-situ testing was performed to support the W* leakage model. This is due to the fact that none of the flaws met the W* in-situ testing selection criteria.

Generic Letter (GL) 95-05, "Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking" One indication was detected in a tube at a tube support plate location with a tube support plate ligament indication. This indication will be addressed in the licensees response to GL 95-05.

U-Bend Noise The licensee inspected the U-bend region of the tubes from Row 1 to Row 3 with a mid-range plus point coil. U-bends with high noise levels were also inspected with high frequency plus point coils.

Axial PWSCC ARC Mixed-mode indications were detected at two dented support plate intersections. One indication consists of an inside-diameter axial flow and an outside diameter (OD) circumferential flaw separated by 0.65 inches. The other mixed-mode indication consisted of an OD axial flaw and an OD circumferential flaw. Both of the tubes were plugged. The indications were small.

They will be further evaluated and will be discussed in the licensees 90-day report.

In-Situ Testing There was no in-situ testing performed during this outage. The licensee stated that none of the flaws detected during the outage met the in-site testing criteria. The licensee further stated that, based on the evaluation, the flaws were not even close to meeting the in-site testing criteria.

The NRC staff did not have any further questions and determined a followup call was not required.

Attachments: Material Provided by Licensee (ADAMS Accession No. ML030550720)