ML20077L434

Forwards Response to Suppl 2 to NRC Bulletin 89-001 Re Failure of Westinghouse Steam Generator Tube Mechanical Plugs.No Plugs Fabricated from Heat NX-5222 Installed in Any Steam Generators at Facilities

ML20077L434
Person / Time
Site:	Byron, Braidwood
Issue date:	08/09/1991
From:	Chrzanowski D COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-89-001, IEB-89-1, NUDOCS 9108120228
Download: ML20077L434 (5)

Text

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Downers Grove, Imnois costs August 9,1991 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

Subject:

Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Zion Station Units 1 and 2 Response to NRC Bulletin 89-01, Supplement 2 Failure of Westinghouse Steam Generator Tube Mechanical Plugs NRC_DochetNos 5.01454L455,_50A56/45L and_50:295/304

Reference:

(a) NRC Bulletin 89 01, dated May 15,1989 (b) M.H. Richter letter to U.S. NRC, dated June 16; 1989 (c) NRC Bulletin 89 01, Supplement 2, dated June 28,1991

Dear Sirs:

Reference (a) requested that licensees determine whether certain mechanical plugs supplied by Westinghouse are installed in their steam generators and, if co, that an action plan (including plug repa;rs and/or reolacement) be implemented to ensure that these plugs will continue to provide adequate assurance of RCPB integrity. This request applied only to plugs fabricated from inconel 600 heats NX-3279, NX-3513, NX-3962, and NX-4523 on the basis of field experience and laboratory studies indicating that plugs from these heats are highly susceptible to primary water stress corrosion cracking (PWSCC).

Reference (b) provided the Commonwealth Edison Company (CECO) response to this Bulletin.

Reference (c) requests that actions similar to those reauested in Reference (a) be extended to include all Westinghouse mechanical plugs f aoricated from thermally treated Inconel 600. These actions are to ensure that these plugs will continue to provide adequate assurance of reactor coolant pressure boundary (RCPB) integrity under normal operating, transient, and postulated accident conditions.

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Document Control Desk August 9,1991 to this let'er provides CECO's response to Supplement 2 of Bulletin 89 01.

Please address any questions you have regarding this response to this office.

Sincerely, U.

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D.J. Chrzanowski Generic issues Administrator Attachments: 1) Response to Bulletin 89-01, Supplement 2 cc: A. Bert Davis - Regional Administrator Rill Senior Resident Inspector - Z/BY/BW C. Patel - Project Manager, NRR T. Hsia - Proiect Manager, NRR R. Pulsifer - Project Manager, NRR crata of f Gwty of _I Sgnpd bef are me on tnis #E'l day i

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ATTACHMENT 1 Action Requested:

ltem 1:

Addresses are requested to verify that information contained in Table 2 of Addendum 2 to Revision 3 of Westinghouse report WCAP 12244, " Steam Generator Tube Plug Integrity Summary Report," June 1991, for their plants is correct for plugs fabricated from group 2 heats. The s aecific information to be verified is the number of Westinghouse mechanical p ugs installed in the hot leg and cold leo side of each steam generator, categorized by heat number and date ol installation. The plug operating temperatures for each plant given in this Table should also be verilied. If information from this Table is incorrect, addresses should larovide correct information. Addresses are requested to so stato if their p! anus have not installed Westinghouse mechanical plugs from group 2 heats.

CECO _Besponse:

The information contained in WCAP-12244 has been reviewed for Zion Units 1 and 2, Byron Units 1 and 2 and Braldwood Units 1 and 2. Westinghouse will be notified of the required corrections and additions. These corrections and additions do not impact any of the 2a,2b,2c, requested actions.

ActionBequested:

Addresses are requested to take the following actions, to be implemented initially during any refueling outage or extended outage (greater than four weeks) which ends 60 days or more following receipt of this bulletin and during all future refueling outages. For the period of time between receipt of the bulletin and 60 days, the actions requested in the original version of this bulletin continue to be applicable for plugs fabricated from group 1 heats.

LIEM_2 a) Addresses should implement appropriate remedial actions (i.e., repair and/or replacement) for all plugs whose estimated lifetime in item 2b, below does not extend to the next refueling outage.

CE9o_Besponse:

All alugs currently listed in WCAP 12244 as well as those plugs to be added to tie WCAP have estimated lifetimes beyond their respective units next refueling outage.

Action Beguested:

IIEM_2 b)

Remaining lifetime estimates (in effective full power days (EFPD)) are aiven in Table 2 of WCAP-12244 in the column entitled " Remain EFPD

~to MIN." These remaining lifetime estimates are relative to reference dates given in the column entitled " Reference CALC Dates " These remaining lifetime estimates may be used directly. These estimates should be adjusted to reflect any corrections noted in Actions Bequested, item 1.

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CECO _Besponse:

The Commonwealth Edison program implemented in November,1E90 will result in the implementation of remedial actions for all Inconel 600 steam generator tube plugs prior to the lifetime dates estimated in WCAP-12244.

The remaining lifetime estimates for corrected or added tube plugs are not impacted in a non-conservative way.

Acilon_Beguested:

LIEM_2 c)

For refueling outages or extended outages ending prior to November, 30,1991, remedial actions for plugs fabricated from NX-5222 may be deferred until the next scheduled refueling outage.

CECO _Besponse:

There are no plugs f abricated from heat NX-5222 installed in any CECO stearn generator therefore this action item is not applicable.

ActioILBequested:

IIEht2 d)

Installation of Westinghouse mechanical plus fabricated from inconel 600 should be discontinued.

GECo_ Response:

The installation of Wectinghouse rnechanical plugs fabricated from Inconel 600 has been discontinued at all Commonwealth Edison sites.

Action _Beguested; IIEM2 e)

If for any refueling outage, the addressee does not an to satisfy items 2a to 2d above, an alternative plan for insuring plu integrity, with appropriate technical justification, should be submi ted to the NRC at lest 30 days before the end of the refueling outage.

CECILBesponse; CECO intends te fully comply with action items 2a through 2d.

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ActionRequested:

LIEht2 f)

Prior to any plug repairs or replacement, addresses are reminded that their responsibilities under ALARA require analysis of the various plug repair or replacement methods, in choosing a plug repair or replacement method, the licensee r hould consider the accessibility of the plugs and the dose reduction benefit of using robotic manipulators.

Prior to plug repair or re alacement, the licensee should consider steam generator decu taminat on and/or local shielding to reduce working area dose rates.

CECO _Besponse Repair technologies to be employed by Commonwealth Edison will vary dependina on the specific site. Plug replacement is the preferred method of repair forbyron Un ts 1 & 2 and Braidwood Units 1 & 2. Repairs implemented in Zion Units 1 & 2 will depend upon ALARA considerations and the number of plugs to be repaired during a specific outage. This change in strategy for Zion is due to the age of the units and the number of plugs to be repaired.

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