ML19325C698

Application for Amend to License NPF-37,requesting one-time Extension of Interval for Performance of Visual Insp of Inaccessible Snubbers,Extending Surveillance Interval Until Unit 1 Third Refueling Outage

ML19325C698
Person / Time
Site:	Byron
Issue date:	10/13/1989
From:	Chrzanowski R COMMONWEALTH EDISON CO.
To:	Murley T Office of Nuclear Reactor Regulation
Shared Package
ML19325C699	List: ML19325C698 ML19325C701
References
NUDOCS 8910170191
Download: ML19325C698 (3)

Text

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} Commonwealth Edison

_ ' 72 West Adams Street, Chicago, Ilkncis "

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}Nv'7 X6dibiiP55/ to:0767 Chicago, Ilknois 60690 October 13, 1989

_Dr. Thomas E. Murley, Director .

I m ~ Office of Nuclear Reactor Regulation E.

'U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Byron Station Unit 1

{ Application for Amendment to Facility

. Operating License NPF-37 i NRC Docket Nos. 50-454

Dear Dr. Murley:

Pursuant to 10 CFR 50.90, Commonwealth Edison proposes to amend Appendix A, Technical. Specification of facility Operating License NPF-37. The proposed amendment requests 'a one time extension of the interval for ps.-formance of the visual Inspection of. inaccessible snubbers. The proposed amendment would extend ,

Lthe. surveillance interval;until the Unit 1, third refueling outage, scheduled to commence January 5,.1990.

The detailed description and summary of the proposed change is presented in Attachment 1. -The revised Technical Specification page is contained in Attachment 2.

'The proposed change has been reviewed and approved by both on-site and off-site review =in accordance with Commonwealth Edison procedures. Commonwealth Edison has reviewed this proposed amendment in accordance with 10 CFR 50.92(c) and has determined that no significant hazards consideration exists. This evaluation t is_ documented in Attachment 3. An Environmental Assessment has been completed and is contained in Att'.chment 4.

This one time extension is required to prevent a Unit I shutdown before the surveillance period expires on December 13, 1989. Therefore, an expedited review'of this proposed amendment is requested.

If Unit I-is shutdown between now and January 5, 1990, such that at least ifive_ days of containment access is available, then Commonwealth Edison will perform the surveillance and this request will be withdrawn or modified.

y Commonwealth Edison-is notifying the State of Illinois of our application

.for this amendment by transmitting a copy of this letter and its attachments to the p designated State Official.

Please direct any questions regarding this matter to this office.

j Very truly yours,

%03Nh p

[ A. hrzanowski Huclear Lic nsing Administrator 0331T:81 MOI cc: Byron Resident Inspector ' I l- L. N. 01shan - NRR Region III Office L Office of Nuclear Facility Safety - IDNS I

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-<R e v' . ATTACHMENT 1 DETAILED DESCRIPTION

^

Technical Specification 4.7.8b requires inaccessible snubbers to be visually inspected in accordance with the schedule based on the number of inoperable snubbers per inspection period. During the last inspection period for Byron Unit 1, one snubber in the inaccessible group failed'the-visual inspection. As a result of this failure, the next visual inspection would be required to be performed within 12 months (1 25%) from the last inspection period. Because this group of snubbers is classified as inaccessible, the unit must be siutdown for the surveillance to be performed. The surveillance must be completed by 9ecember 13, 1989 (12' months + 25%). ' Unit 1 is currently scheduled to begin a refb911ng outage on January 5, 1990. Since the unit has been operating continuously for the past 1254 days, the inaccessible snubbers have been unavailable for inspectiori.

Therefore, Byron Station requests a one time extension for the inaccessib?e snubber

. visual inspection. ~The surveillance will be performed during the Unit 1 third refueling outage.

There-are currently 291 snubbers installed on Byron Unit 1 of which 274 are classified as inaccessible. The snubbers function is to ensure that the structural integrity of the reactor coolant system (RCS) and all other safety related systems

'is maintained during and following a seismic or other event initiating dynamic i loads. Snubber-inaccessibility is determined based upon the existing radiation levels and=the expected time to perform a visual inspection in each snubber location, as well as other factors associated with accessibility during plant operations'(e.g., temperature, atmosphere, location, etc.) and the recommendations of Regulatory Guides 8.8 and 8.10. This Technical Specification amendment requests an extension until January 24, 1990, to complete the visual inspection of the inaccessible snubbers on Unit 1. This is approximately a 6 week extension (10%

extension). This extension will allow sufficient time to shut Unit I down, establish containment access, and complete the surveillance in a rafe and organized fashion. The Station believes this one time extension is acceptable for several reasons:

1. Since the last visual inspection during Unit l's second refueling outage (Sep-Nov 88), the unit has only been shutdown (Hot Standby) once for approximate 1,v 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> on January 31, 1989, (only 2 months into the interval) due to an unplanned Reactor Trip. Unit I has been continuously operating since February 1, 1989, (254 continuous days as of this writing) and we anticipate continuous operations up to the refueling outage if this or.e time extension is granted. He believe the detriment incurred (actual and potential) from an extra cooldown and heatup transient to perform this surveillance is far greater than the negligible increased risk incurred from a 6 week delay. In addition, we believe the proposed extension will still meet the intent of an accelerated surveillance frequency by performing the surveillance in approximately the 16 month versus the normally-allowed 18 months.

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x 2.X During=the last visual inspection interval of inaccessible snubbers, one

, snubber on the reactor' coolant. system was failed and was determined to be +

• frozen.- It was determined that-the cause of the failure resulted from

" ' boric. acid-and rust which coated the snubber barrel. An evaluation was ,

-performed that determined'if.the failed snubber had been frozen for the '

entire cycle, acting as a.rtgid' strut,;the piping systcm would still be acceptable:with the-additional thermal _ movement load imposed by the '

failed snubber. The failed snubber das: replaced. However, as a result I of this failure the. visual inspection interval.for inaccessible snubbers was decreased from 18 months (1 25%) to 12 months (1 25%). One snobber-failure out of 680 inaccessible snubbers (installed as of the last inspection) has decreased the allowed inspection _ interval by about

.one-third. It 1s believed this failure is not'an indication of a generic concern. Since the snubber was replaced, it is anticipated to be operable when it is next inspected.

3. All.the-inaccessible snubbers on Unit I are designed to function for the life of the: plant, approximately 40 years. ' Since Unit 1 is just now '

-completing cycle 3 it is still early in the plant design life.

, Therefore, it is early in the; design life of its snubbers so this provides additional assurance that the snubbers will operate as required.

4. Functional testing is routinely performed on snubbers in accordance with Technical Specification requirements. All 680 Inaccessible snubbers installed as of the last inspection were functionally tested during the

last outage. Defective snubbers found as a result of this functional

-testing were replaced. The 100% functional. testing of inaccessible snubbers'during the last outage provides a higher than normal level of assurance that the snubbers will perform their safety function as

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required._ There have been no events (seismic or transients) that the Station is aware of that could have impaired the operability of any snubbers-demonstrated operable after the last refueling outage. .

5. During the last refueling outage, a snubber reduction modification was performed on Unit I which reduced the number of inaccessible snubbers

.from 680 to1274. The decrease in the number of snubbers installed reduces the probability.of snubber-failures due to external causes, such as boric acid leaks. <

6. The survelliance extension requested is for a short period of time, approximately 6 weeks (10%). As the unit shuts down to begin the

' refueling outage the plant will enter modes where certain systems are not

. required to be operable. As such, the snubbers on these systems will not be required to be operable for approximately 2 weeks out of the requested 6 week extension. This reduces the actual extension period for these snubbers to approximately 4 weeks (7%). As a result the impact of the

-extension is further reduced because the number of snubbers affected by

'tb extension is decreased. In addition, the probability of a seismic or transient event occuring during this short extension, such that the snuober will be required to perform its design function, is negligible.

It is even more remote that if an event occurs that a snubber will fall to perform its function, such that the integrity of a system would be impacted.

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