ML20147F994

Submits Answers to Specific Questions Raised in RAI Re LAR to Allow Removal of Grease from Tendon Sheathing to Facilitate Tendon Removal During SG Replacement

ML20147F994
Person / Time
Site:	Byron, Braidwood
Issue date:	03/20/1997
From:	Hosmer J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9703270309
Download: ML20147F994 (3)

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Commonwealth litivm Company 1400 Opm Pixe g

Downers Grove.11305154*'01 l

March 20,1997 United States Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Document Control Desk

Subject:

Byron Nuclear Power Station, Units 1 and 2 Facility Operating Licenses NPF-37 and NPF-66 NRC Docket Numbers: 50-454 and 50-455 Braidwood Nuclear Power Station, Units I and 2 Facility Operating Licenses NPF-72 and NPF-77 NRC Docket Numbers: 50-456 and 50-457 Tendon Grease Amendment RAI Response

Reference:

1. J. Hosmer (Comed) Letter to USNRC, Tendon Grease Amendment, dated November 4,1996.

2. NRC Request for Additional Information Regarding Removal of Tendon Sheathing Filler Grease, dated February 10,1997.

In Reference 1, Comed submitted a License Amendment Request to the NRC to allow removal of grease from the tendon sheathing to facilitated tendon removal during the Steam Generator Replacement. In Reference 2, NRC requested additional information concerning schedules and preventing the ingress of moisture, water and damaging airborne elements u hile the grease is removed. The answers to the spe.:ific questions raised in the RAI are contained in Attachment 1.

Please address any questions or comments to Marcia Lesniak, Nuclear Licensing Akinistrator, at 630-663-6484.

i Sincerely, p

John B. Hosmer g.Cl j

Engineering Vice President 7

Attachments cc:

A. B. Beach, Regional Administrator - Rlil j

G. Dick, Byron /Braidwood Project Manage - NRR C. Phillips, Senior Resident Inspector - Braidwood S. Burgess, Senior Resident inspector - Byron l

Office of Nuclear Safety -IDNS

" 9f05270309 970320 g

gg%)(%)I,Eh DR ADOCK 050004 4 A linicom Company

l RAIitem 1:

l Please provide detailed schedules for replacement of steam generators in Unit I of Byron and Braidwood.

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Include the following information in the schedules: (1) time (month and year) when the grease will be removed from the specific tendons (2) the period during which the tendons will be without grease coverage, (3) the plant status (operating, hot shutdown, cold shutdown, etc.) during the time when the tendons will be without grease, (4) schedule for tendon removal concrete cutting, containment i

reconstruction, tendon installation, and grease installation.

l Reynmse:

i The following tabulation is based on current schedule development for the Byron Unit I steam generator replacement outage (SGRO). As discussed in our project presentation meeting to the NRC Staff on 7

January 22,1997, the schedule for the Byron SGRO has been accelerated from the date described in our November 4,1996 request. The dates and durations depicted are based on current planning and scheduling.

i Activity Plant Byron Schedule Braidwood Status Schedule i

Mobilize contractor NA May 1997 Note 1 Begin grease removal powe; operation June 1997 Complete grease removal power operation August 1997 i

Plant shutdon for SGRO November 7,1997 Tendon detensioning/ removal cold shutdown and Outage days I thru 10 refueling i

Concrete removal, rebar cutting, defueled Outage days 1I thru 18 liner plate removal for the containment opening (CO)

Steam generator changeout, fitup defueled Outage days 19 thru 67

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Reston, liner plate defueled Outage days 53 thru 59 Replace rebar and concrete in CO defucted Outage days 60 thru 73 l

Reinstall tendons, including defueled or refueling Outage days 68 thru 73 grease replacement Retension tendons cold shutdown Outage days 74 thru 77 l

Containment restored cold shutdown Outage day 78 l

Note 1: The durations shown for Byron are expected to be representative of j

those for Braidwood, detailed clanning for the Braidwood outage has not been i

initiated, but the overall outage is expected to be slightly shorter and lag the Byron outage by approximately one year.

Therefore, the currently planned period during which the tendons will be without grease coverage is about eight months.

RAIItem 2:

Please proside information regarding protecting the tendons from ingress of moisture, water, and damaging airborne elements, such as chlorides, and sulfides, during the time when the tendons are not covered with grease. Some of the methods used in the past have been filling the ducts with an inert gas at a slightly positive pressure or filling the grease caps with fresh grease after removing the grease from the tendons.

Response

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As stated in Comed's submittal, the grease removal operation, even when assisted by the introduction of dry air, is not expected to remove the entire grease inventory in the tendon sheathing. As a minimum, a residual layer of grease will remain on the tendon wire surface, providing protection against the elements.

I Use of dry air will ensure that no moisture is introduced into the tendon sheathing. The tendon end anchors / grease caps are not directly exposed to the weather elements because the existing buttress and dome walkway enclosures at Byron /Braidwood Stations provide protection for the tendon end anchor / grease caps.

l Any opening used for the introduction of air or for grease outflow will be rescaled following the grease removal operation. Therefore, Comed has concluded that the tendons would be adequately protected from the effects of moisture, water, and any damaging airborne elements while the grease is being removed and during the limited time w hen the grease is removed from the tendon sheathirg void.

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