ML20141F643

Forwards Amended Significant Hazards Evaluation & Revised Tech Spec Pages Removing Rod Bow Penalty from Nuclear Enthalpy Hot Channel Factor,Per Util 851127 Request to Amend Licenses NPF-2 & NPF-8

ML20141F643
Person / Time
Site:	Farley
Issue date:	04/11/1986
From:	Mcdonald R ALABAMA POWER CO.
To:	Rubenstein L Office of Nuclear Reactor Regulation
References
TAC-60291, TAC-60292, NUDOCS 8604230114
Download: ML20141F643 (8)

Text

. kiling Address

- Alabama Power Company E00 North 18th Street Post Off ace Box 2641 o.rming3am. Alabama 35291

) Telepto@ 205 783-6090 -

R. P. Mcdonald Serwor Vice President Flintridge Buttding dl{l[Xl[1][] 00WCf

' ' " ' - * " ^"

April 11, 1986 J

Docket Nos. 50-348 50-364 Director, Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission

-Washington, D.C. 20555 Attention: Mr. L. S. Rubenstein Gentlemen:

Joseph M. Farley Nuclear Plant - Units 1 and 2 Deletion of Rod Bow Penalty Technical Specification Change By letter dated November 27, 1985 Alabama Power Company requested changes to Technical Specification 3/4.2.3 and the accompanying Bases for Farley Nuclear Plant Units 1 and 2. This proposed change involves the removal of the Rod Bow Penalty from the Technical pecification calculation of the nuclear enthalpy hot channel factor, F As a result of discussions with the NRC staff, it has been detemined that the significant hazards evaluation included with the November 27, 1985 submittal should be modified. Therefore, Alabana Power Company is providing an amended significant hazards evaluation and revised Bases pages

- for Units 1 and 2, as Attachments 1 and 2 respectively, in order to provide additional clarification on the source of the generic DNB margins and credit taken to offset rod bow penalty.

This supplemental submittal in no way affects the proposed changes to Technical Specification 3/4.2.3 which were included with the November 27, 1985 submittal. This supplemental submittal only provides clarification to the Background section of the significant halards evaluation and the Basis section of Technical Specification 3/4.2.3 and does not alter the analysis or conclusions of the significant hatards evalisation. Therefore, Alabama Power Company reaffirms that the proposed deletion of the Rod Bow Penalty from the Technical Specifications does not involve a significant hazards g consideration. O y

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fir. L. S. Rubenstein April 11, 1986 1, U. S. Nuclear Regulatory Commission Page 2 Following NRC approval of the proposed Technical Specification change, Alabama Power Company will incorporate the rod bow inf ormation which formed the basis for this change as well as the amount of generic DNBR margin utilized to offset the effect of rod bow in the FSAR Update.

Pursuant to 10CFR170.21, the required License Amendment Application fee of

$150.00 was enclosed with Alabama Power Company's November 27, 1985 submittal. In accordance with 10CFR50.90, three (3) signed originals and 40 copies of this request are enclosed. A copy of this change has been sent to Mr. Dan Turner, the Alabama State Designee, in accordance with 10CFR50.91(b)(1).

If there are any questions, please advise.

Respectfully submitted, (gy1, p fe [oALABAMAPOWiR) b +'

R. P. Mcdonald SWORN TO AND SUBSCRIBED BEFORE ME TH S [/ DAY OF JYIf 1986

)V\mEGhNof0 My omissionNotafy gblic k-//-JT Expi re's:

RPM / JAR:kpc-050 Attachments cc: Mr. L. B. Long Dr. J. N. Grace Mr. E. A. Reeves Mr. W. H. bradford Mr. Dan Turner

ATTACINENT 1 Significant Hazards Evaluation Pursuant to 10 CFR 50.92 for the Proposed Removal of the Rod Bow Penalty i from the Technical Specifications Proposed Change Remove the Rod Bow Penalty (RBP) from the Units 1 and 2 Technical Specification 3.2.3 and revise the corresponding discussion in the bases.

Background

The phenomenon of fuel rod bowing in Westinghouse PWRs is considered in the -

departure from nucleate boiling ratio (DNBR) safety analysis of Farley Nuclear Plant (FNP) Units 1 and 2. In the early 1970s much larger fuel rod bowing than had been predicted was observed in Westinghouse low parasitic (LOPAR) fuel assemblies. Due to this larger rod bow, the DNBR analyses were reevaluated. Subsequently, the DNBR effects due to rod bow were redefined and a rod bow pepity (RBP) was applied to the Technical Specification calculation of F 3H. Additionally, the RBP as a function of burnup was defir.ed in the Technical Specifications by the addition of Figure 3.2-3.

In an effort to gain insight into the extent and effect of fuel rod bow on DNBR, Westinghouse Electric Corporation has obtained data from irradiated fuel assemblies. In 1975 sufficient rod bowing infonnation was available to develop an empirical model to predict rod bow as a function of region average burnup. This information and the effects of predicted rod bowing on power peaking and DNBR analyses were presented in the original WCAP-8691, which was submi tted for NRC review in January 1976. Revision 1 of WCAP-8691 (Reference 1) and References 2 and 3 document subsequent NRC inquiries and Westinghouse responses. The Westinghouse methods for predicting the ef fects of rod bow on DNB as described in the above documents were approved by the NRC staff in Reference 4.

References 1, 2 and 3 have successfully demonstrated that applicable generic credits for margin resulting from retained conservatism in the evaluation of DNBR and/or margin obtained from measured plant operating parameters, which "

are less limiting than those required by the plant safety analysis, can be used to of fset the ef fect of rod bow. The maximum DNBR penalty for rod bow which must be accour.ted for is less than 3% at 33,000 MWD /MTU as identified in Figure 2 of Reference 3. The safety analyses for FNP Units 1 and 2 maintain sufficient margin to accommodate full and low flow DNBR penalties.

This margin totals 9.1% DNBR and includes the following:

't DNB Margin %

a. Design limi t DNBR of [1.30 vs.1.28], 1.6

b. Axial Grid Spacing Coefficient (Ks) of)

'[0.046 vs. 0.059],

4.1 l

c. Thermal Diffusion Coefficient of

[0.038 vs . 0.059], ]

d. DPER Multiplier of [0.865 vs. 0.88], and 1.7

e. Pitch reduction. 1.7 Total: 9.1%

This margin is adequate to of fset all rod bow penalty for assembly average burnups of up to 33,000 MWD /MTU. The FNP nuclear design basis allows sufficient reactivity to be installed in the fuel to allw for assembly average burnups of 33,000 MWD /MTU as specified in FSAR Section 4.3.1.1. The maximum rod bow penalties accounted for in the design safety analysis are based on an assembly average burnup of 33,000 MWD /MTV. gtburnupsgreater than 33,000 MW/MTU, credit is taken for the ef fect of FAH burndown, due to the decrease in fissionable isotopes and the buildup of fission product inventory, and no additional rod bow penalty is required.

References (1) Skaritka, J., (Ed), " Fuel Rod Bow Evaluation," WCAP-8691, Revision 1 July 1979, (Proprietary) .

(2) " Partial Response to Request Number 1 for Additional Information on WCAP-8691, Revision 1" letter, E. P. Rahe, Jr., (Westinghouse) to J. R.

Miller (NRC), NS-EPR-2515, dated October 9,1981, (Proprietary).

(3) " Remaining Response to Request Number 1 for Additional Infonnation on WCAP-8691, Revision 1" letter, E. P. Rahe, Jr., (Westinghouse) to J. R.

Miller (NRC), NS-EPR-2572, dated March 16,1982, (Proprietary) .

(4) NRC letter f rom C. Thomas (NRC) to E. P. Rahe (Westinghouse) dated De. ember 29, 1982.

(5) Joseph M. Farley Nuclear Plant Unit 1 and Unit 2 FSAR Update, Docket ,

Nos. 50-348 and 50-364.

Analysis Alabama Poser Company has reviewed the requirements of 10 CFR 50.92 as they relate to the proposed deletiog of the rod bow penalty f rom the technical specification calculation of F6H and considers the proposed change not to involve a sigt.ificant hazards consideration. In support of this conclusion the following analysis is provided:

a .

5 (1) The proposed change will not significantly increase the probability or consequences of an accident previously evaluated because an adequate margin of safety to the minimum DNBR of 1.30 will be maintained for those transients which must account for the phenomenon of fuel rod bowing in the DNBR safety analysis (i.e., Condition I and Condition 11 events).

(2) The proposed change will not create the possibility of a new or different kind of accident from any accident previously evaluated because the plant configuration or mode of operation is not altered by the removal of the rod bow penalty. Adequate margin exists in the plant safety analysis to allow operation without the requirement for any DNBR related .od bow penalty.

(3) The proposed change will not involve a significant reduction in a margin of safety because the safety analyses for Farley Nuclear Plant Units I and 2 maintain Sufficient margin to a:commodate the removal of all rod bow penalties related to DNBR and the margin within the existing DNBR limits remains unaffected.

Conclusion Based upon the analysis provided herewith, Alabama Power Company has determined that the proposed Technical Specification change will not significantly increase the probability or consequences of an accident previously evaluated, create the possibility of a new or different kind of accident f rom any accident previously evaluated, or involve a significant reduction in a mergin of safety. Therefore, Alabama Power Company has determined that the proposed change meets the requirements of 10 CFR 50.92(c) and does not involve a significant hazards consideration.

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t ATTACHMENT 2 Proposed Changed Pages i

Unit 1 Revision -

Page B 3/4 2-4 Replace Unit 2 Revision Page B 3/4 2-4 Replace 1

l L - . .

POWER DISTRIBUTION LIMITS I BASES EE E ESE EE E333E3 E 3 3 3 E 3 3 E ESS E ES EE SE E33333333 3 E E E E ES S S S 33 B B S S EBER ESE E E E 33 E 3 3 3 3 3 3 FfH will be maintained within its limits provideg conditions a.

through d. above are maintained. The relaxation of FEH as a function of THERMAL POWER allows changes in the radial power shape for all permissible rod insertion limi ts.

When an Fn measurenent is taken, an allowance for both experimental error and manufheturing tolerance must be made. An allowance of 5% is

'dppropriate for a full core map taken with the incore detector flux mapping system and a 3% allowance is appropriate for manufacturing tolerance.

When FjH is measured, experimental error must be allowed for and 4% is the appropriate allowance for a full core mag taken with the incore detection system. The specified limit for FSH also contains an 8% allowance f r uncertainties which means that normal operation will result in F H11.55/1.08. The 8% allowance is based on the following considerations:

a. Abnormal perturbations in the radial power shape, such as from rod N

misalignment, af fect FAH more directly than Fg ,

b. Although rod movement has a direct influence upon limiting FO to w hin its limit, such control is not readily available to limit F H,and

c. Errors in prediction for control power shape detected during startup physics tests can be cncpensated for in Fg by restricting axial flux di st ribu tion. This compensation for F[H is less readily available.

Fuel rod bowing reduces the value of DNB ratio. Credit is available to of fset this reduction in the generic margin. The generic design margins, totaling 9.1% DNBR, conpletely offset any rod bow penalties (less than 3%

for the worst case which occurs at a burnup of 33,000 MWD /MTU). This margin includes the following:

1) Design limi t DNBR of 1.30 vs.1.28

2) Axial Grid Spacing Coefficient (ks) of 0.046 vs. 0.059

3) Thermal Dif fusion Coefficient of 0.038 vs. 0.059

4) DNBR Multiplier of 0.865 vs. 0.88

5) Pitch reduction 1

FARLEY-UNIT 1 B 3/4 2-4 AMENDMENT N0.

POWER DISTRIBUTION LIMITS

~

BASES

=== ........................................................................

F H will be maintained within its limits provide conditions a.

throug d. above are maintained. The relaxation of F as a function of THERMAL POWER allows changes in the radial power shape or all permissible rod insertion limits.

When an Fo measurenent is taken, an allwance for both experimental error and manufacturing tolerance must be made. An allowance of 5% is appropriate for a full core map taken with the incore detector flux mapping system and a 3% allowance is appropriate for manufacturing tolerance.

When F[H is measured, experimental error must be allowed for and 4% is the appropriate allwance for a full core mag taken with the incore detection system. The specified limit for F ggalso contains an 8% allowance fgr uncertainties which means that normal operation will result in The 8% allowance is based on the following considerations:

F[H <1.55/1.08.

a. Abnormal perturbations in the radial power shape, such as from rod misalignment, af fect F H more directly than FQ,

b. Although rod movement has a direct influence upon limiting Fg to within its limit, such control is not readily available to limit FfH, and

c. Errors in prediction for control power shape detected during startup physics tests can be co:Tensated for i Fg by restricting axial flux di st ribu tion. This cocpensation for H is less readily available.

Fuel rod bowing reduces the value of DNB ratio. Credit is available to of fset this reduction in the generic margin. The generic design margins, totaling 9.11 DN3R, cocpletely of fset any rod bow penalties (less than 3%

f or the worst case which occurs at a burnup of 33,000 M2/MTU). This margin includes the follwing:

1) Design limi t DNBR of 1.30 vs.1.28

2) Axial Grid Spacing Coefficient (ks) of 0.046 vs. 0.059

3) Thermal Dif fusion Coefficient of 0.038 vs. 0.059

4) DNBR Multiplier of 0.865 vs. 0.88

5) Pitch reduction FARLEY-UNIT 2 B 3/4 2-4 AMENDMENT N0.

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