ML080860710

Request for Additional Information Regarding Steam Generator Tube Inspection Reports for 2007 (1R14) Outage

ML080860710
Person / Time
Site:	Diablo Canyon
Issue date:	04/04/2008
From:	Wang A NRC/NRR/ADRO/DORL/LPLIV
To:	Conway J Pacific Gas & Electric Co
Wang, A B, NRR/DORL/LPLIV, 415-1445
References
TAC MD6690
Download: ML080860710 (5)

Text

April 4, 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 - REQUEST FOR ADDITIONAL INFORMATION REGARDING STEAM GENERATOR TUBE INSPECTION REPORTS FOR 2007 (1R14) OUTAGE (TAC NO. MD6690)

Dear Mr. Conway:

By letters dated August 27 (two letters), and November 26, 2007, Pacific Gas and Electric Company (the licensee), submitted information summarizing the results of the 2007 steam generator (SG) tube inspections at Diablo Canyon Power Plant, Unit No. 1. These inspections were performed during the 14th 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 Diablo Canyon Power Plant, Unit No. 1 in a letter dated August 8, 2007.

The NRC staff has determined that we require additional information to complete our review of the SG inspection results. A request for additional information is enclosed. The request was discussed with Tom Grozan of your staff on March 31, 2008, and it was agreed that a response would be provided within 60 days of receipt of this letter.

If you or your staff have questions concerning the resolution of this matter, please contact me at (301) 415-1445.

Sincerely,

/RA/

Alan B. Wang, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-275

Enclosure:

Request for Additional Information cc w/encl: See next page

April 4, 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 - REQUEST FOR ADDITIONAL INFORMATION REGARDING STEAM GENERATOR TUBE INSPECTION REPORTS FOR 2007 (1R14) OUTAGE (TAC NO. MD6690)

Dear Mr. Conway:

By letters dated August 27 (two letters), and November 26, 2007, Pacific Gas and Electric Company (the licensee), submitted information summarizing the results of the 2007 steam generator (SG) tube inspections at Diablo Canyon Power Plant, Unit No. 1. These inspections were performed during the 14th 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 Diablo Canyon Power Plant, Unit No. 1 in a letter dated August 8, 2007.

The NRC staff has determined that we require additional information to complete our review of the SG inspection results. A request for additional information is enclosed. The request was discussed with Tom Grozan of your staff on March 31, 2008, and it was agreed that a response would be provided within 60 days of receipt of this letter.

If you or your staff have questions concerning the resolution of this matter, please contact me at (301) 415-1445.

Sincerely,

/RA/

Alan B. Wang, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-275

Enclosure:

Request for Additional Information cc w/encl: See next page DISTRIBUTION:

PUBLIC RidsNrrPMAWang RidsOgcRp LPLIV Reading RidsAcrsAcnwMailCenter RidsNrrDorlDpr RidsRgn4MailCenter RidsNrrDciCsgb RidsNrrLAJBurkhardt RidsNrrDorlLpl4 KKarwoski, NRR RidsNrrLAGLappert ADAMS Accession Number: ML080860710 *Staff-provided RAI Memo OFFICE LPL4/PM LPL4/LAiT LPL4/LA NRR/DCI/CSGB LPL4/BC NAME AWang GLappert JBurkhardt AHiser (*) THiltz, MTM for DATE 4/4/08 4/3/08 4/3/08 3/18/08 4/4/08 OFFICIAL RECORD COPY

Diablo Canyon Power Plant, Units 1 and 2 (3/10/2008) cc:

NRC Resident Inspector City Editor Diablo Canyon Power Plant The Tribune c/o U.S. Nuclear Regulatory Commission 3825 South Higuera Street P.O. Box 369 P.O. Box 112 Avila Beach, CA 93424 San Luis, Obispo, CA 94306-0112 Sierra Club San Lucia Chapter Director, Radiologic Health Branch ATTN: Andrew Christie State Department of Health Services P.O. Box 15755 P.O. Box 997414, MS 7610 San Luis Obispo, CA 93406 Sacramento, CA 95899-7414 Ms. Nancy Culver Mr. James Boyd, Commissioner San Luis Obispo California Energy Commission Mothers for Peace 1516 Ninth Street MS (31)

P.O. Box 164 Sacramento, CA 95831 Pismo Beach, CA 93448 Mr. James R. Becker Chairman Site Vice President San Luis Obispo County Diablo Canyon Power Plant Board of Supervisors P.O. Box 56 1055 Monterey Street, Suite D430 Avila Beach, CA 93424 San Luis Obispo, CA 93408 Jennifer Tang Mr. Truman Burns Field Representative Mr. Robert Kinosian United States Senator Barbara Boxer California Public Utilities Commission 1700 Montgomery Street, Suite 240 505 Van Ness, Room 4102 San Francisco, CA 94111 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 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 Jennifer Post, Esq.

Pacific Gas & Electric Company P.O. Box 7442 San Francisco, CA 94120

REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 2007 STEAM GENERATOR TUBE INSPECTIONS DIABLO CANYON POWER PLANT, UNIT NO. 1 DOCKET NO. 50-275 OPERATING LICENSE NO. DPR-80 By letters dated August 27 (two letters, References 1 and 2), and November 26, 2007 (Reference 3), Pacific Gas and Electric Company (the licensee), submitted information summarizing the results of the 2007 steam generator (SG) tube inspections at Diablo Canyon Power Plant, Unit No. 1. These inspections were performed during the 14th 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 Diablo Canyon Power Plant, Unit No. 1 in a letter dated August 8, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML072140015).

In order for the NRC staff to complete its review of these reports, we request responses to the following questions:

1. On page 2-4 of Enclosure 2 of Reference 2, you indicated that preliminary disposition of a Plus Point signal at the seventh support plate on the cold-leg side was initially attributed to axial primary water stress-corrosion cracking. This indication was then dispositioned based on tracing the bobbin signal to the baseline inspection. Please discuss the nature of the Plus Point signal. Discuss whether the bobbin indication could be a result of some other artifact at this location (which is not changing) and, therefore, the Plus Point indication is a result of the development of a new crack-like indication.

2. On page 2-9 of Enclosure 2 of Reference 2, you discussed two indications which merged. You appear to have concluded that the depth of the combined indication did not undergo significant growth in depth since the maximum voltage of the combined indication was comparable to the maximum voltage of the indications during the prior inspection. Please discuss whether these indications were depth-sized using phase analysis (since phase analysis is used in depth sizing these types of indications).

3. On page 9 of 113 of Enclosure 3 of Reference 2, you indicated that you re-performed the operational assessment using the 2R13 probability of prior cycle data. Please discuss why this assessment was re-performed.

4. On page 13 of 113 of Enclosure 3 of Reference 2, you indicated that there were some tubes where an outside diameter-initiated indication could not always be found in the bobbin lookup results from 1R13. Presumably, these were for indications called distorted inside diameter support (DIS) indications. Please discuss under which alternate repair criteria these indications were assessed. If

an indication was a DIS in 1R13, the NRC staff would have expected that it would have been inspected with a rotating probe and either dispositioned as non-flaw like, as a primary water stress-corrosion cracking indication, or as some other type of flaw. If the 1R14 bobbin indication was now classified as a distorted outside diameter-initiated indication, the NRC staff would have expected that it would have also been inspected with a rotating probe (since previous DISs would have been inspected). Please clarify. Please also refer to the discussion on page 20 of 113 in which it appears that a DIS indication in 1R13 was also classified as an axial outside diameter stress-corrosion crack not detectable with the bobbin.

5. On page 1-22 of Reference 3, you discuss ligament cracking of the tube support plates. Since none of the new indications were traceable to the preservice inspection, please discuss any insights on the cause of these indications.

REFERENCES

1. PG&E Letter DCL-07-084, to U.S. Nuclear Regulatory Commission, from Donna Jacobs, PG&E, Docket No. 50-275, OL-DPR-80, Diablo Canyon Unit 1, Inservice Inspection Report for Unit 1 Fourteenth Refueling Outage (ADAMS Accession No. ML072420339).

2. PG&E Letter DCL-07-085, to U.S. Nuclear Regulatory Commission, from Donna Jacobs, PG&E, Docket No. 50-275, OL-DPR-80, Diablo Canyon Unit 1, Results of Steam Generator (SG) Tube Alternate Repair Criteria (ARC) Inspections for Diablo Canyon Power Plant Unit 1 Fourteenth Refueling Outage (ADAMS Accession No. ML072470188).

3. PG&E Letter DCL-07-106, to U.S. Nuclear Regulatory Commission, from Donna Jacobs, PG&E, Docket No. 50-275, OL-DPR-80, Diablo Canyon Unit 1, 180-Day Steam Generator Report for Diablo Canyon Power Plant Unit 1 Fourteenth Refueling Outage (ADAMS Accession N o. ML073390290).