ML20148E882

Application for Amends to Licenses DPR-39 & DPR-48,changing Tech Specs to Extend Rod Bow Penalty Curve & EFPH Clad Collapse Limits to Include Higher Region Average Fuel Burnup

ML20148E882
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	10/27/1978
From:	Reed C COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 7811070168
Download: ML20148E882 (7)

Text

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C mmenwssith Edimn f

v pne First National Plaza. Chicago. Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 ,

October 27, 1978 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission ,

Washington, D.C. 20555

Subject:

Zion Station Units 1 and 2 Proposed Change to Facility Operating I License Nos. DPR-39 and DPR-48 NRC Docket Nos. 50-295 and 50-304

Dear Sir:

Pursuant to 10 CFR 50.59, Commonwealth Edison Company ,

hereby requests a change to Operating License Nos. DPR-39 and DPR-48, Appendix A, Technical Specifications. The purpose of this emendment is to extend the FNoH rod bow penalty curve and '

the E7PH clad collapse limits to include higher region average ,

fuel ournups. The proposed change to the Zion Technical Specifications is enclosed as Attachment I.

The bases for this change follow.

FN Rod Bow Penalty Curve

&H N As utlined below, the proposed change extends the '

F AH rod bow Penalty curve to higher region average fuel burnups ,

consistent with the NRC guidance in the NRC report, " Interim Safety Evaluation Report on Effects of Fuel Rod Bowing on Thermal ,

Margin Calculations for Light Water Reactors" - Revision 1 -

February 16, 1977. 4 (1) Based on the observed channel closure of Westinghouse fuel elements of the Low Parasitic design that are  !

used at Zion Station, the amount of rod bow has j currently been calculated through a burnup of 38,300 4 MWD /MTU by using a correlation of the form a+bN Burnup as provided in the aforementioned NRC report and by meeting a 95/95 confidence level.

Using this correlation complete channel closure is calculated not to occur until after 47,000 MWD /MTU.

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C:mm:nwerith Edissn NRC Docket Nos. 50-295/304 Director of Nuclear Reactor Regulation October 27, 1978 Page 2 (2) The postulated bowing mechanisms and potential changes in fuel element behavior due to burnup have been reviewed to ensure that the correla-tion for clearance reduction is applicable for burnups up to 47,000 MWD /MTU.

(3) The full DNB penalty for complete channel closure as determined by experiment has been applied starting at 47,000 MWD /MTU, and a proportional penalty has been applied for the lesser closures occuring for lower burnups.

Increase of Clad Collapse EFPH Limit Originally, the existing clad collapse EFPH (Effective Full Power Hour) limits for Zion Station were conservatively chosen to be less than the fuel element capability but to exceed the maximum expected EFPH exposure predicted for the given fuel region. Although additional capability for further operation was known to exist, the current and expected region average discharge burnups did not necessitate quantifying this capability.

The proposed change to extend the clad collapse EFPH limits to higher exposures is still based on the same conservative assumptions and the same analysis methodology as described in the Westinghouse topical, WCAP-8381. The revised calculations indicate that no clad flattening would occur with the revised EFPH limits and that additional operational capability exists beyond these limits to preclude clad flattening.

The above considerations and the proposed Technical Specification change (Attachment I) have been reviewed by On-site and Off-Site Review with the conclusion that there are no unreviewed safety questions.

This license modification is being requested in anticipation of the inauguration of an extended burnup program at Zion Station. In light of the federal government's decision

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Comm:nwsslth Edison NRC Docket Nos. 50-295/304 Director of Nuclear Reactor Regulation October 27, 1978 .

Page 3 to forego reprocessing of light water reactor fuel, the Department ,

of Energy has recently urged fuel vendors and utilities to examine areas in which light water reactor fuel can be more efficiently utilized to conserve uranium resources and to reduce future spent fuel assembly inventories. Currently, Commonwealth Edison is reviewing ant extended burnup program with Westinghouse and EPRI. ,

This program would consist of the reinsertion of a small number of discharged fuel assemblies, four or less, in a Zion unit for '

one and possibly two additional fuel cycles to obtain assembly discharge burnups on the order of 47,000 to 55,000 MWD /MTU. To date, Westinghouse only has individual fuel rod exposure data in this range. No commercial fuel assembly data has been gathered.

Additional information on the scope of the extended burnup program planned for Zion Station including proposed fuel examinations, technical and safety reviews will be provided  ;

separately in the very near future. However, in order to facilitate a decision to inaugurate this program as soon as practicable, Commonwealth Edison requests that the NRC Staff expedite a review and approval,by December 20, 1978,of the ,

proposed mnendment change described herein. ,

Pursuant to 10 CFR 170, commonwealth Edison has '

determined that this proposed snendment is a combined Class III l and Class I Amendment. As such, Commonwealth Edison has enclosed a fee remittance in the amount of $4,400.00 for this proposed ,

anendment. Commonwealth Edison has concluded that the proposed mnendment change does not involve a significant hazards considera-tion since the calculations made in support of this amendment are  !

consistent with well defined and established analysis methods that have received previous NRC Staff approvals and since the amendment does not involve a decrease in safety margins.

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I C:mm:nw:alth Edison NRC Docket Nos. 50-295/304 Director of Nuclear Reactor Regulation October 27, 1978 Page 4 Three (3) signed originals and thirty-seven (37) copies of this letter are provided for your use.

Very truly yours, b<

Cordell Reed Assistant Vice-President attachment SUBSCRIBED and S,W RN to before me this /- , day of N6LU4nl>$k) , 1978.

]lA Mil ll) D a t001/>b fjotaryPublicQ

Commonwraith Edissn NRC Docket Nos. 50-295/304 .

ZION STATION UNITS 1 AND 2 NRC DOCKET NOS. 50-295 AND 50-304 ATTACHMENT I

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AgIeuod # d N

t i In accordance with the approved Westing- DNB Parameters: The limits on the DNB related

• house model as presented in WCAP-8381, no parameters assure that each of the parameters 1 collapses are expected throughout the is maintained within the normal steady state fuel cycle of operation. The predicted envelope of operation assumed in the transient 3

minimum times for clad flattening are: and accident analyses. The limits are consis-tent with the initial FSAR assumptions and have

! been analytically demonstrated adequate to main-Fuel Region EFPH tain a minimum DNBR of 1.30 throughout each analyzed transient.

1 19,500 2 >36,000 The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> periodic surveillance of these para-

, 3 >41,000 meters thru instrument readout is sufficient to ensure that the parameters are restored within

for Zion Unit 1. The predicted minimum their limits following load changes and other times to collapse for Unit 2 are

expected transient operation. The 18 month per-iodic measurement of the RCS total flow rate is Fuel Region EFPH adequate to detect flow degradation and ensure

! correlation of'the flow indication channels with 1 27,000 measured flow such that the indicated percent 2 >36,000 flow will provide sufficient verification of j 3 >41,000 flow rate on a 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> basis.

l A design criterium requires that pro- A quadrant to average power tilt will be indica-

posed reload fuel region exposure lev- ted by the excore detectors. The excore current els expected at the time of discharge tilt is indicated by the arrangement of the curr-not exceed the predicted minimum coll- ent recorders on the control board. Four 2-pen apse time. Operation in the exposure recorders are provided, the pens are grouped so

! range in which clad collapse is post- that, in the absence of a tilt, the two ulated is not permitted under these 1

technical specfications.

The predicted minimum time to coll-apse for all reload fuel regions is greater than 41,000 effective full

, power hours.

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