B16965, Provides Response to GL 97-06, Degradation of SG Internals Dtd 971230.Commitment Made by Util,Encl

Provides Response to GL 97-06, Degradation of SG Internals Dtd 971230.Commitment Made by Util,Encl

ML20217L828
Person / Time
Site:	Millstone
Issue date:	03/26/1998
From:	Bowling M NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
B16965, GL-97-06, GL-97-6, NUDOCS 9804070392
Download: ML20217L828 (8)

Text

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Rope Ferry Rd. (Route 156), Toterford, CT 06385 NuclearEnergy Malstone Nudear Power Station Northeast Nudear Energy Company teri r CT 06385-0128 (860) 447-1791 Fax (860) 444-4277 The Nonhemt Utilities System ,

MAR 2 61998 i Docket No. 50-336 B_1ft965 t

Re: 10CFR50.54(f)

' GL 97-06 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 l

Millstone Nuclear Power Station, Unit No. 2 Response to Generic Letter 97-06, Dooradation of Steam Generator internals {

1 This letter provides Northeast Nuclear Energy Company's (NNECO) response to Generic Letter (GL) 97-06' regarding Degradation of Steam Generator internals.

GL 97-06 requests that NNECO submit a written response which includes the following information:

1. Discussion of any program in place to detect degradation of steam generator internals and a description of the inspection plans, including the inspection scope, '

frequency, methods, and equipment.

l-l The discussion should include the following information:

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l (a) Whether inspection records at the facility have been reviewed for indications of

tube support plate signal anomalies from eddy-current testing of the steam generator tubes that may be indicative of support plate damage or ligament cracking. If the addressee has performed such a review, include a discussion of the findings.

t (b) Whether visual or video camera inspections on the secondary side of the steam generators have been performed at the facility to gain information on the g condition of steam generator internals (e.g., support plates, tube bundle

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. . wrappers, or other components). If the addressee has performed such inspections, include a discussion of the findings.

(c)Whether degradation of steam generator internals has been detected at the facility, and how the degradation was assessed and dispositioned. }

' GL 97-06, " Degradation of Steam Generator Intemais," dated December 30,1997.

9804070392 900326 I PDR ADOCK 05000336:

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U.S. Nuclear Regulatory Commission B16965Page 2 2.' if the addressee currently has no program in place to detect degradation 'of steam generator internals, include a discussion and justification of the plans and schedule

- for establishing such a program, or why no program is needed.

Attachment 1 provides NNECO's response to the requested items described above.

NNECO's commitments associated with this letter are provided in Attachment 2.

Should you have any questions regarding this submittal, please contact Mr. Ravi G.

Joshi at (860) 440-2080.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY v

M. L. Bowling, Jr. l Millstone Unit No. 2 Recovery Officer 1

Swom to and subsc,ii:,cd before me

'this c2d # day of *md .1998 A\

PETER J. M!NER l1 My Commission expires 2fd#N$ _

Attachment ec:- W. D. Travers, Ph.D, Director, Special Projects Office H. J. Miller, Region l Administrator D. G. Mcdonald, Jr., NRC Senior Project Manager, Millstone Unit No. 2 D. P. Beaulieu, Senior Resident inspector, Millstone Unit No. 2 l P. F. McKee, Deputy Director of Licensing - Special Projects Office

W._ D. Lanning, Deputy Director of inspections - Special Project Office l

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Docket No 50-336 B16965 i

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Attachment 1 Millstone Nuclear Power Station, Unit No. 2 Response to GL 97-06,

• Degradation of Steam Generator Internals" l

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March 1998 i

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U.S. Nuclear Regulatory Commission B16965/ Attachment 1/Page 1 )

Millstone Nucirar Power Station, Unit No. 2 Response to GL 97-06, " Degradation of Steam Generator internals"

Introduction:

Generic Letter (GL) 97-06, Degradation of Steam Generator (SG) Intemals was issued to:

(1) Alert addressees to the previously communicated findings of damage to steam generator intemais, namely, tube support plates and tube bundle wrappers, at foreign Pressurized Water Reactors (PWR) facilities; l 1

(2) Alert addressees to recent findings of damage to steam generator tube support plates at a U.S. PWR facility; (3) Emphasize to addressees the importance of performing comprehensive examinations of steam generator intemals to ensure steam generator tube structural integrity is maintained in accordance with the requirements of Appendix B to 10 CFR Part 50; and (4) Require all addressees to submit information that will enable the NRC staff to verify whether addressees' steam generator intemals comply with and conform to the currer,t licensing bases for their respective facilities.

This response provides information for Millstone Unit No. 2 (MP2) requested t;'"11..

The information requested includes:

(1) A discussion of any program in place to detect degradation of steam generator ,

intemals and a description of inspection plans, including the inspection scope, j frequency, methods and equipment. The GL requires discussions to include the i following information for each facility: l (a) Whether inspection records at the facility have been reviewed for indications of tube support plate signal anomalies from eddy current testing of the steam I generator tubes that may be indicative of support plate damage or ligament cracking.

(b)Whether visual or video camera inspections on the secondary side of the steam generators have been performed at the facility to gain information on the condition of the steam generator internals (e.g., support plates, tube bundle wrappers, or other components).

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U.S. Nuclear Regulatory Commission j

B16965/ Attachment 1/Page 2 >

(c) Whether degradation of steam generator internals has been detected at the facility, and how the degradation was assessed and dispositioned.

(2)If the addressee currently has no program in place to detect degradation of steam generator internals, include a discussion and justification of the plans and j schedule for establishing such a program, or why no program is needed.

Response

(1) Northeast Nuclear Energy Company (NNECO) has no formal program in place at MP2 to detect degradation of steam generator internals at this time. However,

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secondary side inspections have been performed:

(a)The Balek & Wilcox international (BWI) replacement steam generators L

installed at MP2 in 1992 have lattice tube supports fabricated from 410 type ferritic stainless steel. Those supports are expected to be significantly more resistant to flow erosion and general corrosion than the carbon steel supports which have experienced degradation in the industry.

l Eddy-Current Testing (ECT) techniques capable of identifying erosion, corrosion l or ligament cracking in steam generators having 410 stainless steel . lattice l supports are not available. However, ECT inspections are capable of detecting i the absence of support signals which could result from severe degradation. No such findings have been observed in the MP2 steam generators.

(b) During Cycle 12 Refueling Outage, in October 1994, after the first operating cycle of the MP2 replacement steam generators, an extensive visual, and video examinstion of the steam drum, U-bend, and tubesheet regions of both steam )

i generators was performed by BWI. Each steam generator was inspected for i

erosion, corrosion, and any unusual characteristics. Specific areas examined i included:

e steam outlet nozzle, e primary and secondary steam separators, e primary and secondary decks, supports and seals, e feedwater assembly as accessible, e U-bend support structure, i

-e top lattice support as accessible, and e top of the tube sheet.

U.S. Nuclear Regulatory Comtr.ission 816g65/ Attachment 1/Page 3 4

l (c) No degradation of the steam generator internals was detected during the inspections described in (b) above:

. An examination of the upper steam drums and outlet nozzles revealed no evidence of material degradation.

. The steam separators and dock structures were examined from a number of access points. There was no evidence of erosion. All welds appeared

!, b9 sound. Scattered minor pitting was observed at the bottom of some of the steam separators.

. .The feedwater rings and the shroud cones showed discoloration of the oxide film, likely due to flow impingement at each J-tube exit, however there were no signs of erosion or material degradation. The original layout markings applied during the initial fabrication of the steam generators were still clearly visible.

e A video examination of several J-tubes from inside the feedwater headers j revealed no signs of erosion of the J-tube to feedwater ring weld joints.

L e One shroud to lug to shen interface was inspected. This lug was over the handho!e in SG #2. There were no signs of material degradation.

. A video examination included the blowdown lanes and annulus areas of the tubesheets and a$ncent SG tubes. All areas examined appeared to

, be in good conditicq. A foreign object, thought to be a piece of weld wire, l was retrieved from the tubesheet in SG #2. No associated damage was observed. An oddy current inspection of the tubes in the location of the foreign object confirmed that there was no (de damage.

(2) The nuclear power industry recently voted to adopt an initiative requiring each utility !

l to implement the guidance provided in NEl 97-06, " Steam Generator Program l Guidelines", no later than the first refueling outage starting after January 1,19%.

l Included in the guidelines is a requirement to monitor secondary-side SG l components whose failure could pmvent the SG from fulfilling its intended safety functions. The monitoring shallinclude l

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. design reviews,  !

e assessment of potential degradation mechanisms, L e evaluation of industry experience, and e inspections, as necessary. I i-NNECO plans to follow NEl 97-06 including the inspection guidelines contained in the latest revision of the EPRI PWR SG Examination Guidelines. '

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, Docket No. 50-336 B16965 Attachment 2 Millstone Nuclear Power Station, Unit No. 2 Commitments Associated With GL 97-06

" Degradation of Steam Generator internals" t

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U.S. Nuclear Regulitory Commission B16965/ Attachment 2/Page 1 List of Regulatory Commitments The following table identifies those actions committed to by Northeast Nuclear Energy Company (NNECO)in this document.

COMMITMENT DATE OR REGULATORY COMMITMENT OUTAGE t

l B16965-01 NNECO plans to follow NEl 97-06 On going commitment.

! including the inspection guidelines contained in the latest revision of l the EPR! PWR SG Examination Guidelines.

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