ML16342D040

Requests Addl Info Re Licensee Response to GL 95-03, Circumferential Cracking of SG Tubes. Response Requested within 30 Days of Receipt of Ltr

ML16342D040
Person / Time
Site:	Diablo Canyon
Issue date:	08/31/1995
From:	Stone J NRC (Affiliation Not Assigned)
To:	Rueger G PACIFIC GAS & ELECTRIC CO.
References
GL-95-03, GL-95-3, TAC-M92239, TAC-M92240, NUDOCS 9509050350
Download: ML16342D040 (8)

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 205554001 August 31, 1995 Hr. Gregory H. Rueger Pacific Gas and Electric Company NPG - Hail Code A10D P.O.

Box 770000 San Francisco, California 94177

SUBJECT:

REQUEST FOR ADDITIONAL INFORHATION GENERIC LETTER (GL) 95-03 DIABLO CANYON NUCLEAR POWER PLANT, UNITS 1

AND 2 (TAC NOS.

H92239 AND H92240)

Dear Hr. Rueger:

On April 28, 1995, the U.S. Nuclear Regulatory Commission issued Generic Letter (GL) 95-03, "Circumferential Cracking of Steam Generator Tubes," which requested addressees to evaluate recent operating experience related to circumferential cracking, justify continued operation until the next scheduled steam generator tube inspections, and develop plans for the next steam generator tube inspections.

The staff has reviewed the response provided by Pacific Gas and Electric Company for Diablo Canyon, Units 1 and 2.

As a

result of the review of your response, the staff has identified the following areas for which additional information and/or clarification is needed to complete its review of your response to GL 95-03.

We request that you respond to this request for additional information within 30 days of receipt of this letter.

The following areas have been identified as being susceptible to circumferential cracking:

a ~

b.

c ~

d.

Expansion transition circumferential cracking Small-radius U-bend circumferential cracking Dented location (including dented tube support plate (TSP))

circumferential cracking Sleeve joint circumferential cracking 2.

In your response, area d was not specifically addressed.

Please submit the information requested in GL 95-03 per the guidance contained in the GL for this area (and any other area susceptible to circumferential cracking).

The staff realizes that some of the above areas may not have been addressed since they may not be applicable to your plant;

however, the staff requests that you clarify this (e.g.,

no sleeves are installed; therefore, the plant is not susceptible to sleeve joint circumferential cracking).

In your response it was indicated that the use of c-scan plots for analysis of rotating pancake coil (RPC) data was proceduralized as a

result of recent industry experience.

Mere RPC c-scans analyzed during C ~QgpQ 9509050350 95083k P,PDRL PDR ADQCK 05000275 ale

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Ruege> the past steam generator tube inspections7 reanalyzed to ensure that indications were August 31, 1995 If not, were the data not missed7 3.

In your response to Generic Letter GL 95-03, you indicated that dents greater than 5.0 volts had been and would be inspected with a technique capable of detecting circumferential cracking.

Provide a detailed description of the procedure used for sizing the dents (i.e., 4.0 volts on 4-20X through-wall ASHE holes at 550/130 mix). If the procedure is identical to the procedure for the voltage-based repair criteria, a

detailed description is not necessary.

It was indicated that the sample plan for dents may be limited to the lowest TSP.

Clarify if the 20X sample will be determined from the number of dents greater than 5.0 volts at,all TSPs or from the number of dents greater than 5.0 volts at the lowest hot-leg TSPs.

A large dent at an upper TSP may be more signi,ficant in terms of corrosion susceptibility as a result of higher stresses than a small dent at a

lower TSP even though the temperature is lower at the upper TSP.

'Given this, discuss the basis for the proposed sample strategy given that cracking depends on many factors including temperature and stress levels.

4.

During the last Unit 2 steam generator tube inspection

outage, a

circumferential indication was detected at the expansio'n transition region in one tube.

Provide the expansion criteria us'ed for the WEXTEX region during the previous steam generator tube inspections at Unit 2, and provide the expansion criteria to be used during the upcoming Unit 1

and 2 outages.

This request is within the original reporting burden for information collection of 350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br /> covered by the Office of Management and Budget clearance number 3150-0011, which expires July 31, 1997.

If you have any questions, please contact me at 301-415-3063.

Sincerely, Original signed by:

James C. Stone, Sensor Project Manager Project Directorate IV-2 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket Nos.

50-275; 50-323 cc:

See next page DOCUMENT NAME: DCSGC.RAI DISTRIBUTION'ocket File PUBLIC JRoe EGA1 WBateman KThomas JStone DHcDonald ACRS (4),

TWFN PDIV-2 Reading

OGC, 015B18

KPerkins, WCFO

JDyer, RIV DChamberlain, RIV EPeyton KKarwoski, EHCB OFC NAME DATE PDIV-2/LA KT o s:pk JStone 8'

/95 3 /) /95 ey on g />i/95 0

ICIAL R CORD C

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Mr. Gregory M. Rueg the past steam generator tube inspections2 reanalyzed to ensure that indications were August 31, 1995 If not, were the data not missed?

3.

In your response to Generic Letter GL 95-03, you indicated that dents greater than 5.0 volts had been and would be inspected with a technique capable of detecting circumferential cracking.

Provide a detailed description of the procedure used for sizing the dents (i.e., 4.0 volts on 4-20X through-wall ASME holes at 550/130 mix). If the procedure is identical to the procedure for the voltage-based repair criteria, a

detailed description is not necessary.

It was indicated that the sample plan for dents may be limited to the lowest TSP.

Clarify if the 20X sample will be determined from the number of dents greater than 5.0 volts at all TSPs or from the number of dents greater than 5.0 volts at the lowest hot-leg TSPs.

A large dent at an upper TSP may be more significant in terms of corrosion susceptibility as a result of higher stresses than a small dent at a

lower TSP even though the temperature is lower at the upper TSP.

Given this, discuss the basis for the proposed sample strategy given that cracking depends on many factors including temperature- =and stress levels.

4.

During the last Unit 2 steam generator tube inspection

outage, a

circumferential indication was detected at the expansion transition region in one tube.

Provide the expansion criteria used for the WEXTEX region during the previous steam generator tube inspections at Unit 2, and provide the expansion criteria to be used during the upcoming Unit 1

and 2 outages.

This request is within the original reporting burden for information collection of 350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br /> covered by the Office of Management and Budget clearance number 3150-0011, which expires July 31, 1997.

If you have any questions, please contact me at 301-415-3063.

Sincerely, Original signed by:

James C. Stone, Senior Project Manager Project Directorate IV-2 Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket Nos.

50-275; 50-323 cc:

See next page DOCUMENT NAME: DCSGC.RAI DISTRIBUTION:

Docket File PUBLIC JRoe EGA1 WBateman KThomas JStone DMcDonald ACRS (4),

TWFN PDIV-2 Reading

OGC, 015B18

KPerkins, WCFO

JDyer, RIV DChamberlain, RIV EPeyton KKarwoski, EMCB OFC PDIV-2/LA PDIV-2/PM PDIV-2/PH NAME de~yon KT o s:pk JStone DATE

'Z /Bl/95 Z Q /95 OF ICIAL R CORD C

P P') /95

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Hr. Gregory H. Rueger CC:

NRC Resident Inspector Diablo Canyon Nuclear Power Plant c/o U.S. Nuclear Regulatory Commission P. 0.

Box 369 Avila Beach, California 93424 Dr. Richard Ferguson, Energy Chair Sierra Club California 1100 11th Street, Suite 311 Sacramento, California 95814 Hs.

Nancy Culver San Luis Obispo Mothers for Peace P. 0.

Box 164 Pismo Beach, California 93448 Hs. Jacquelyn C. Wheeler P. 0.

Box 164 Pismo Beach, California 93448 Managing Editor The Count Tele ram Tribune 1321 Johnson Avenue P. 0.

Box 112 San Luis Obispo, California 93406 Chairman San Luis Obispo County Board of Supervisors Room 370 County Government Center San Luis Obispo, California 93408 Mr. Truman Burns Hr. Robert Kinosian California Public Utilities Commission 505 Van Ness, Room 4102 San Francisco, California 94102 Hr. Steve Hsu Radiologic Health Branch State Department of Health Services Post Office Box 942732 Sacramento, California 94232 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower

& Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Hr. Peter H. Kaufman Deputy Attorney General State of California 110 West A Street, Suite 700 San

Diego, Cal iforni a 92101 Christopher J.

Warner, Esq.

Pacific Gas L Electric Company Post Office Box 7442 San Francisco, California 94120 Mr. Warren H. Fujimoto Vice President and Plant Manager Diablo Canyon Nuclear Power Plant P. 0.

Box 56 Avila Beach, California 93424 Diablo Canyon Independent Safety Committee ATTN:

Robert R. Wellington, Esq.

Legal Counsel 857 Cass Street, Suite D

Monterey, California 93940

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