ML20085C294

Suppl to 910531 Application for Amend to License NPF-3, Revising Tech Spec 5.3.1, Fuel Assemblies to Permit Repair of Fuel Assemblies Containing Defective Fuel Rods

ML20085C294
Person / Time
Site:	Davis Besse
Issue date:	08/29/1991
From:	Shelton D CENTERIOR ENERGY
To:
Shared Package
ML20085C293	List: ML20085C289 ML20085C294 ML20085C298
References
1976, NUDOCS 9109040248
Download: ML20085C294 (6)

Text

, ,. Docket Number 50-346 Licensa Number HPF-3 Serial Number 1976 Enclosure Page 1 APPLICATION FOR AMENDMENT TO FACILITY OPERATING LICENSE NUHJER NPF-3 DAVIS-BESSE NUCLEAR POVER STATION UNIT NUMBER 1 Attached are requested changes to the Davis-Besse Nuclear Pover Station Unit Number 1, Facility Operating License Number NPF-3. Also included is the Safety Assessment and Significant flazards Consideration.

The proposed changes submitted under cover letter Serial Number 1976 concern:

Appendix A, Technical Specification 5.3.1, ruel Assemblies p.

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By: I

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6. C. Shelton, VTEe Prest ent, Nuclear - Davis-Besse Sworn and Subscribed before me this 29th day c f August, 1991.

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Notary PuY11c, State of Ohio WELYNl.. DE.o D W PtG UC,s;A g (j Q g g E4*es A4 r, ty, 9109040248 910829 PDR ADOCK 05000346 p PDR t

. Docket Numbat 50-346 License Number NPF 3 Serial Number 1976 Enclosure Page 2 The following information is provided to support issuance of the requested changes to the Davis-Besse Nuclear Power Station, Unit Number 1, Operating License Number NPF 3. Appendix A. Technical Specification 5.3.1, Fuel Assemblies.

A. Time Required to implement: This change is to bo implemented within 45 days after the NRC issuance of the License Amendment.  !

B. Reason for change (License Amendment Request 91-0011, R1): This change vill allow the repair of fuel assemblies containing defective fuel rods. The scope of the repairs vill be limited to ensure that iepaired fuel assemblies remain bounded by the currently NRC approved methodologies as justified by analyses or ,

tests.

C. Safety Assessment and Significant !!arards Considerations See attached.

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, Docket Number 50-346 License Numbar NPF-3 Sarial Number 1976 Attachment  !

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Safety Assessment and Significant Hazards Consideration for License Amendment Request 91-0011, Rev. 1 TITLE: Revision to Technical Specification (TS) 5.3.1, Fuel Assemblies (FA), to Allow the Repair of FAs Containing Defective Fuel Rods.

DESCRIPTION:  !

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This License Amendment Request (LAR) proposes a revision of TS 5.3.1 to j allov replacerent of defective fuel tods with stainless steel filler 4 rods in the B&V Fuel Company (BJFC) designed Mark B FA. The acceptability of non-fuel bearing rods vill be determined by cycle  !

specific analyses, using applicable Nuclear Regulatory Commission (NRC) ]

approved codes and methodologies which are valid for the configurations j used. .

There is a potential that such changes to FAs vill be performed at the Davis-Besse Nuclear Fover Station, Unit 1 (DBNPS) during the seventh refueling outage (7RFO). Because of the specific descriptive vording '

cf the present TS 5.3.1, a TS change is needed to allov the use of repaired FAs. Due to the need to be in the refueling mode (Hode 6) to determine the specific changes that must be made to a FA, it might not be possible to accomplish a TS revision at that time without causing a restart delay. A requert is being made at this time to incorporate new TS vording that vill avoid the need to expend both Toledo Edison's

- (TE's) and the NRC's resources in administering an expedient TS revision during 7RFO. This vill minimize the risk of a restart delay caused by administrative processing.

SYSTEMS, COMPONENTS, AND ACTIVITIES AFFECTED:

This TS revision affects the description of the FAs in TS 5.3.1 by allowing for a reduced number of fuel rods and use of stainless steel filler rods.

SAFETY FUNCTIONS OF THE AFFECTED SYSTEMS a COMPONENTS AND ACTIVITIES:

The function of the FAs is to generate power for a specified period.

The design of the FAs assures the safe operation of the reactor core within operating and safety limits. ,

- A FA is-normally composed of two hundred and eight fuel rods, sixteen 5 control rod guide tubes, one instrumentation tube, eight spacer grids, and two end fittings. The guide tubes, spacer grids, and end fittings form a structural cage to arrange the rods and tubes into a 15x15 array. Fuel rods are supported at each spacer grid by contact points.

The guide tubes are attached to the upper and lover end fittings. The use of similar material in the guide tubes and fuel rods results in minimal differential thermal expansion.

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Dockot Number 50-346 l Licanas Number NPF-3  !

Serial Nunbar 1976 Attachment Page 2 The function of TS 5.3.1 is to ensure that the fuel configuration has been analyzed using NRC tipproved anethodologies and that safety limits 1 and design criteria are maintained. j i I l EFFECTS ON SAFETY:

Fuel assembly repair by replacement of defective fuel rods with stainless steel filler rods has been implemented at other B&V designed facilities, fer example at three Mlle Island Nuclear Generating j L Station, Unit Number 1, and Arkansas Nuclear Cae, Unit No. 1. Repairs '

may involve recaging the non-defective f uel rods into a new FA structure. The new FA structure vill contain Zircaloy spacer grids.

The repairs are considered acceptable provided that the number and

, configuration of filler rod substitutions is limited to configurations for which appilcable NRC approved codes and methods are valid. The

acceptability of the repairs must also consider mechanical design issues to ensure proper mechanical performance of the repaired assembly.

A During the cycle-specific evaluation, the effects of stainless steel filler rods and the change from Inconel to Zircaloy grids (the latter analysis is to be done in the case of reenging) vill be analyzed.- The analyses vill addrc.ss the effect of the repair on performance I i parameters such as reactivity, power peaking, margin to departure from nucleate boiling for the surrounding fuel rods, and mechanical design to shov that existing' safety limits and design criteria vill still be  ;

met. The extent of the repairs allowed will be restricted to l configurations for which NRC approved methodologies are valid.

l The structure of a FA is determined by its upper and lover end fittings and the guide tubes that separate them. Fuel rods and stainless steel filler rods are contained by eight spacer grids located along the length of the guic'e tubes. The stainless steel filler rods have been designed so that they vill stay integrated with the FA over the remaining design life of the FA.

Replacement of fuel rods with stainless steel filler rods does not affect the structural ability of a FA to withstand normal handling. For 1.

a combined loss-of-coolant accident (LOCA) and Safe Shutdown Earthquake (SSE), a FA is designed to allow for a safe shutdown of the reactor. T l Based on structural evaluations completed by BVFC, it has been o determined that stainless steel filler rods do not adversely affect the performance of'a FA during a combined LOCA and SSE.

L The material used for the stainless steel filler rods (SS304) is a standard FA material, suitable for the teactor or Spent Fuel Pool (SFP) environment. The thermal expansion of the stainless steel filler rod in the radial direction vill be about three times more than a Zircaloy-4 clad fuel rod. That expansion vill compress the spring l stops on the spacer grids-about 0.002 inches more than the fuel rods.-

That compression is within the. elastic range of the spring stops, and vill.not cause any set of the spring stops.

Docket Nambar 50-346 Licenso Nunbar NPF-3 [

i Serial Numbar 1976 Attachment f Page 3 By the design of the grids, there is no adverse mechanical effect i translatable to grid springs that hold fast the surrounding fuel rods.

Therefore, there is no increase in the potential for fuel defects due .

to grid fretting. i The gap between the top of the stainless steel filler rod and the i bottom of the Upper End Fitting (UEF) is 1.7 inches for the cold l condition. As a result of temperature expansion, this gap is 1.1 l inches at 650 degrees F. The clearance vill actually increase with ,

irradiation due to the faster growth of the guide tubes compared to a [

filler rod. The overall irradiation growth of the guide tubes was i analyzed with respect to the stainless steel filler rod. Results of '

this evaluation shoved that clearance is maintained between the stainless steel filler rod and the UEF under reactor operating  ;

temperature and irradiation conditions. There are no interferences l anticipated over the remaining lifetime of a FA, and there vill be no l resultant rod bowing potential.

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The stainless steel filler rod design also vill not affect the t hydraulic lift characteristics of a FA with the start of a reactor i coolant pump. j In summary, there is no. adverse effect on safety since this TS revision '

is only for the description of the number of fuel rods in a Mark B fuel design. The number and configuration of filler rod substitutions vill '

be limited to those configurations for which applicable NRC approved l codes and methods are valid.

SIGNIFICANT tlAZARDS CONSIDERATION: ,

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The NRC has provided standards in 10 CFR 50.92(c) for determining j vhether a significant hazard exists due to a proposed amendment to an  ;

Operating License for a facility. A proposed amendment involves no  ;

significant hazards consideration if operation of the facility in -

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accordance with the proposed changes voulds (1) Not involve a  ;

significant increase in the probability or consequences of an accident i previously evaluated; (2) Not create the posribility of a new or different kind of accident from any previously evaluated; or (3) Not '

involve a significant reduction in a margin of safety. Toledo Edison -

has reviewed the proposed changes and determined that a significant  :

hazards consideration does not exist because operation of the DBNFS in l accordance with the proposed changes vould: j t

la. Not involve a significant increase in the i , ability of an accident previously evaluated because the probability of any ,

accident which is presently evaluated is independent of the  !

fuel design or assembly configuration. Therefore, no accident i initiators or assumptions are affected.  ;

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Dockot Nunbar 50-346 .

Licensa Nu2bar NPP-3 r Serial Number 1976 [

Attachment ,

Page 4 i

lb. Not involve a significant increase in the consequences o( an I accident previously evaluated because the core performance end i i

accident response vill be bounded by the cycle-specific teload l analysis, which assures that there is no adverse effect on the radiological consequences of previously evaluated accidents. ,

L i 2a. Not create the possibility of a new kind of accident from any accident previously evaluated because the modified fuel r assemblies vill meet FA design specifications. Thus, although this proposed change vould allov modifications to fuel  ;

assemblies, the effects of such modifications vould not lead to  !

the initiation of a new kind of accident.  !

2b. Not create the possibility of a different kind of accident from .!

any accident previously evaluated because the modified fuel essemblies vill meet FA design specifications. Thus, although i this proposed change vould allov modifications to iuel >

assemblies, the effects of such modifications vould not lead to i the initiation of-a different kind of accident. i t

3. Not involve a significant reduction in a margin of safety  :

because the replacement of defective fuel rods vill be analyzed  !

in the cycle-specific analysis. The number and configuration i of filler rod substitutions vill be limited to those  !

configurations for which applicable NRC approved codes and l methods are valid. This vill verify that acceptable safety l margins are maintained. Conformance to existing design i t

.r.riteria.and safety analysis limits vill be confirmed before  ;

l operation of the core for the next fuel cycle, i CONCLt!SION:  ;

5 On the basis of the above, Toledo Edison has determined that the License Amendment Request does not involve a significant hazards consideration. As this License Amendment-Request concerns proposed  ;

changes to the Technical Specifications that must be revieved by the .

Nuclear Regulatory Commission, this License Amendment Request does not l constitute an unreviewed safety question. ,

ATTACHMENT: [

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' Attached are the proposed marked-up changes to the Operating License.

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