ML16343A560
| ML16343A560 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/21/1998 |
| From: | Steven Bloom NRC (Affiliation Not Assigned) |
| To: | Rueger G PACIFIC GAS & ELECTRIC CO. |
| References | |
| TAC-M97254, TAC-M97255, NUDOCS 9801290116 | |
| Download: ML16343A560 (12) | |
Text
january 21, 1998 Mr. Gregory M. Rueger, Senior Vice President and General Manager Pacific Gas and Electric Company Nuclear Power Generation N9B P. O. Box 770000 San Francisco, California 94177
SUBJECT:
REQUEST FOR ADDITIONALINFORMATION-PROPOSED TECHNICAL SPECIFICATION CHANGE REGARDING VOLTAGE BASED STEAM GENERATOR TUBE REPAIR CRITERIA (TAC NOS. M97254 AND M97255)
Dear Mr. Rueger:
By letter dated February 26, 1997, Pacific Gas and Electric Company (PGKE) submitted a license amendment to incorporate the voltage-based repair criteria for steam generator tubes into the technical specifications.
The staff has generated a list of questions as a result of our review.
In order to complete our review, the additional information listed in the enclosure is required.
Please'submit your response within 60 days from receipt of this letter.
Sincerely, Original Signed By Steven D. Bloom, Project Manager Project Directorate IV-2 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-275 and 50-323
Enclosure:
Request for Additional Information cc w/encl: See next page DISTRIBUTION'ocket Files PUBLIC PDIV-2 r/f EGA1 WBateman EPeyton SBloom OGC ACRS PGwynn, RIV HWong, RIV TSullivan, 0-7-D-4 DOCUMENT NAME:DC97254. RAI OSIER ggr p~p To receive a copy of this document, indicate in the box: "C" ~ Copy without enclosures "E" = Copy with enclosures "N" ~ No copy OFFICE PH/PD4-NANE SBloo DATE 01/
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Mr. Gregory M. Rueger january 21, 1998 cc w/encl:
NRC Resident Inspector Diablo Canyon Nuclear Power Plant c/o U.S. Nuclear Regulatory Commission P. O. Box 369 Avila Beach, California 93424 Dr. Richard Ferguson, Energy Chair Sierra Club California 1100 11th Street, Suite 311 Sacramento, California 95814 Ms. Nancy Culver San Luis Obispo Mothers for Peace P. O. Box 164 Pismo Beach, California 93448 Chairman San Luis Obispo County Board of Supervisors Room 370 County Government Center San Luis Obispo, California 93408 Mr. Truman Burns Mr. Robert Kinosian California Public Utilities Commission 505 Van Ness, Room 4102 San Francisco, California 94102 Mr. Steve Hsu Radiologic Health Branch State Department of Health Services Post Office Box 942732 Sacramento, California 94232 Diablo Canyon Independent Safety Committee ATTN: Robert R. Wellington, Esq.
Legal Counsel 857 Cass Street, Suite D Monterey, California 93940 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower & Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Christopher J. Warner, Esq.
Pacific Gas & Electric Company Post Office Box 7442 San Francisco, California 94120 Mr. Robert P. Powers Vice President and Plant Manager Diablo Canyon Nuclear Power Plant P. O. Box 56 Avila Beach, California 93424 Telegram-Tribune ATTN: Managing Editor 1321 Johnson Avenue P.O. Box 112 San Luis Obispo, California 93406
LI E
ED STEA Page D-3 of Attachment D. Pacific Gas and Electric Company (PGRE) states that the voltage-based repair criteria willnot be applied to tube-to-tube support plate (TSP) intersections where the tubes with degradation may potentially collapse or deform as a result of the combined postulated loss-of-coolant accident (LOCA) and safe shutdown earthquake (SSE) loadings [i.e., the wedge region]. PGKE also states that tubes in this region willinitiallybe inspected with a bobbin probe, further inspected with a rotating pancake coil (RPC) probe ifdegradation is detected with the bobbin probe, and plugged only ifRPC detects crack-like indications.
Acceptance of the practice of allowing a tube, with degradation identified by a bobbin probe, to remain in-service based on a lack of RPC confirmation may be acceptable ifit can be demonstrated that the RPC probe has a threshold of detection approximately equal to or less than the repair limits in the technical specifications for the mode of degradation of interest.
Based on work done in support of the voltage-based plugging criteria (documented in Draft NUREG 1477, "Voltage-Based Interim Plugging Criteria for Steam Generator Tubes" ), it was determined that the bobbin coil may have a greater sensitivity to outside diameter (OD) tube degradation than RPC probes.
Also, it was determined that a lack of confirmation by RPC may not indicate that the outside diameter stress corrosion cracking (ODSCC) degradation depth is less than 40 percent through-wall (the technical specifications repair limit). Therefore, PGRE's proposal for addressing indications in the wedge region may not be adequate, because it would potentially permit ODSCC indications to remain in-service that are potentially greater than the technical specifications (TS) repair limit.
In addition, PGSE stated that only indications that were confirmed as "crack-like" by RPC would be plugged/repaired.
This aspect may also be inadequate because it is known that not all repairable indications (e.g., ODSCC/IGA and wear at TSPs) are crack-like.
Provide additional technical justification to support PGRE's proposal to address indications Identified in wedge region tubes in light of the problems identified above.
Otherwise, modify the proposal accordingly.
The NRC staff has agreed with the Nuclear Energy Institute (NEI) on a protocol by which the industry willperiodically update the ODSCC database used to perform Generic Letter (GL) 95-05-specified calculations.
The staff concluded that the protocol was acceptable, with one exception, in a letter from Brian Sheron, NRC, to David Modeen, NEI, dated April 10, 1997.
In a letter from R. Clive Callaway, NEI, to Edmund Sullivan, NRC, dated October 28, 1997, NEI made a proposal regarding the one exception (mentioned above) which the NRC staff has found acceptable.
The NRC staff
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I is currently preparing a response letter to NEI to indicate as such.
Please state your intent with respect to whether you intend to followthe protocol for determining which database you willutilize.
In addition, PG8 E states that the most current revision of the EPRI database (to be used in performing GL 95-05 specified calculations) that has been submitted to the NRC is EPRI Topical Report NP-7480-L, Addendum 1, "Steam Generator Tubing Outside Diameter Stress Corrosion Cracking at Tube Support Plates Database for Alternate Repair Limits, 1996 Database Update," Final Report November 1996. This is not the most current revision of the EPRI database.
Please state your intent as to which database you willbe using.
Lastly, the Joseph M. Farley Nuclear Plant (Farley) recently identified pulled tube data which was determined to be "significant" per Item 5 of the protocol discussed above.
Therefore, a revision to the EPRI database and associated correlations is required.
Please state your intent on whether you intend on including the Farley tube puli data in your database and associated correlations.
Provide a justification ifyou do not intend on including the Farley tube pull data.
NRC Information Notice (IN) 97-79 stated that Braidwood had used two different temperature conditions in comparing the projected end-of-cycle tube leakage with the maximum allowable primary-to-secondary leakage.
The IN went on to say that other licensees may have made similar mistakes.
Please discuss this issue as it may relate to PG8 E calculations.
4.
Proposed Technical Specification (TS) Section 4.4.5.4a.10)e.
"Note 2:" of this section does not comply with GL 95-05. The portion underlined below was excluded.
Please revise the proposed TS accordingly or provide a basis for why the TS does not need to be revised.
["The upper voltage repair limitis calculated according to the methodology 95 0~'I 5.
Proposed TS Section 4.4.5.5d.1) does not comply with GL 95-05. The portion underlined below was excluded.
Please revise the proposed TS accordingly or provide a basis for why the TS does not need to be revised.
["Ifestimated leakage based on the projected end-of-cycle (or ifnot practical, using the actual measured endef-cycle) voltage distribution exceeds the leak limit for the next operating cycle."j 6.
Page D-20 ofAttachment D. PG8E states that RPC standards that have EDM notches qualiTied to Appendix H of the EPRI PWR Steam Generator Examination Guidelines for detection of degradation specific to the DCPP steam generators willbe used in lieu of the specific RPC standard requirements described in Appendix Ato WCAP-12985, Revision 1. Discuss how the use of different standards willaffect the quality of the RPC inspection (e.g., change in detection sensitivity, signai-to-noise ratio, etc.).
Page D-21 of Attachment D. DCPP Unit 1 - Inspection of intersections with dents greater than or equal to (>) 5 volts.
Unit 1 contains a large number of dents > 5 volts at the 6th and 7th TSP. The current RPC inspection scope proposal would not require any inspection at the 6th or 7th TSP unless indications were Identified at gg the lower TSPs.
Based on the large percentage of dents > 5 volts which are in the 6th and 7th TSP, the staff believes that these TSPs should be sampled each outage.
Propose a modified inspection scope accordingly.
Page D-21 ofAttachment D. DCPP Unit1-inspection of intersections with dents > 5 volts, The RPC initial inspection scope and the expansion criteria are determined based only on the Identification of PWSCC or circumferential cracking indications. Another purpose of performing RPC of dents > 5 volts is to identify axial ODSCC that may have been masked by a dent when performing the bobbin coil examination.
Please modify
'he criteria for determining initial scope and expansion criteria to include axial ODSCC not detected by bobbin, or provide additional technical justification to support PG&E's original proposal.
Page D-21 of Attachment D. DCPP Unit 1 - Inspection of intersections with dents > 5 volts. The staff believes that ifan RPC scope expansion to 20% of the next highest TSP in a SG is required, a minimum of 50 intersections in that SG at that TSP should be sampled, or all the dents at that TSP should be sampled ifthere are less than 50 dents at that TSP. Please modify the expansion criteria accordingly.
Page D-23 of Attachment D. DCPP Units 1 and 2-Augmented inspection program of intersections with dents less than (<) 5 volts. The staff is unable to review this issue because an augmented program was not proposed.
Please propose an augmented inspection program of intersections with dents < 5 volts for staff review.
Page D-28 of Attachment D. DCPP - Unit 1 - PG8E's original proposal for meeting GL 95-05 criteria for the tube pull program discussed tube pull plans for 1R8 and 1R9.
Because GL 95-05 voltage-based plugging criteria willnot be implemented until 1R9, please discuss your current plans for performing tube pulls and how they willmeet GL 95-05 requirements (i.e., quantity and selection criteria).
What are PGLE's plans regarding deplugging and returning-to-service tubes (i.e.,
recovering tubes) with axial ODSCC'? There is some industry experience which indicates that the ODSCC in this type of tube may experience a higher growth rate, once the tube has been returned to service, than in a tube that has never been plugged.
Please discuss PGRE's plans in light of this industry experience (e.g., special inspection plans, special acceptance criteria, special monitoring and/or reporting criteria, treatment as a separate population in leakage/burst calculations with respect to growth rate, etc.).
Proposed TS Section 4.4,6.2.1.
The proposed addition of bullet "f."to paragraph 4.4.6.2.1 of the TS states that SG primary-to-secondary leakage willbe determined at least once per 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, except when the source term and mass flow rates are changing.
Clarify whether this would be applicable to MODES 3 and 4 ggJy, or to MODES 1,2,3, and 4.
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4 Ifthe proposed bullet "f."is applicable in Modes 1 and 2, then provide a technical justification for permitting the plant to operate for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in these modes without determining the primary-to-secondary leakage.
COMMENT-NO RESPONSE NECESSARY Page D-11 ofAttachment D. GL 95-05 states that a constant value of 0.6 should be assumed for the probability of detection (POD) of ODSCC flaws. PGKE requested approvai to use a POD that is a function of voltage and is described as the Probability of Prior Cycle Detection (POPCD) in EPRI Topical Report NP-7480-L, Addendum 1, "Steam Generator Tubing Outside Diameter Stress Corrosion Cracking*at Tube Support Plates Database for Alternate Repair Limits, 1996 Database Update," Final Report November 1996.
Currently, the NRC staff is addressing the POPCD issue generically with the industry through NEI. PGKE willbe permitted to use a revised POD, in lieu of a constant value of 0.6, ifand when a revised POD is approved by the NRC. Until that occurs, PG8 E willbe required to use a constant value of 0.6. This willbe documented in the NRC safety evaluation.
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