ML18227B283

Response to Request for Supplemental Information for Proposed Amendment to Facility Operating Licenses

ML18227B283
Person / Time
Site:	Turkey Point
Issue date:	02/15/1978
From:	Robert E. Uhrig Florida Power & Light Co
To:	Stello V Office of Nuclear Reactor Regulation
References
L-78-56
Download: ML18227B283 (16)

Text

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

DISTRIBUTION FQR INCOMING 'MATERIAL 50-250/251 REC: STELLO V ORG: UHRIG R E DQCDATE: 02/15/78 NRC FL PWR 8. LIGHT DATE RCVD: 02/22/78 DOCTYPE: LETTER NOTARIZED: NO COPIES RECEIVED

SUBJECT:

LTR 3 ENCL 3 FORWARDING INFO SUPPLEMENTING PROPOSED AMEND TO FACILITY OPERATING LIC NO DPR-31 8( DPR-42 DTD 01/27/78 CONCERNING 19/ TUBE PLUGGING.

I PLANT NAME:TURKEY PT 53 REVIEWER INITIAL: X JM TURKEY PT 83 'ISTRIBUTER INITIAL:

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)~~gPjgIfg~) f'gLCIIf,f l7 FLORIDA POWER 8c LIGHT COMPANY February 15, 1978 L-78-56 Office of Nuclear Reactor Regulation Attention: Mr.. Victor Stello, Director Division. of Operating Reactors U. S'. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Stello:

Re: Turkey Point Units 3 and 4 Docket Nos. 50-.250 and 50-251 NRC Information- Re uest The attached information supplements our proposed amendment to Facility Operatin'g Licenses DPR-31 and DPR-41 dated January 27, 1978,(L-78-32). It is being submitted in response to questions from your staff.

Very truly yours, Robert E. Uhrig Vice President REU/MAS/RJA/bab Attachment cc: Mr. James P. O'Reilly, Robert Lowenstein, Esquire Region II PEOPLE... SERVING PEOPLE

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ATTACHMENT Re: Turkey Point Units 3 6 4 Docket Nos. '50-250 6 50-251 19% Tube Plu in Question 1 Justification of the use of 98% of, the thermal design flow for analysis with 19% of the steam generator tubes plugged requires flow measurement: data from which this point can be .extrapolated. Provide the flow versus tube plugging level data points. Describe (1) the tests from which these points were obtained, (2) the error analysis 'performed, and (3') the method of assuming conservatism in the use of the 98% flow point.

Res onse 1 The use of 98% thermal design flow in the analysis was based on the evaluation that it would conservatively bound the pro-jected reactor coolant flow with 19% steam generator tube plugging.. The evaluation was performed as follows:

(a) Sensitivity values obtained from the NSSS supplier indicated that 3% to 4% tube plugging would result in 1% reactor coolant flow reduction.

(b) Elbow tap hP measurements which 'have been taken after each refueling on Unit 4 (0 13.2% plugging range) have confirmed the sensitivity predicted by the NSSS supplier.

(c) FPL. performed a reactor coolant flow test. on Unit 4 in August 1977 to determine actual flow with the existing tube plugging of 13.2%. Appropriate sen-sors were calibrated just, prior to the test and then a steady state calorimetric heat balance method was used to determine reactor coolant flow. The resulting. flow was 103.4% of the thermal design flow.

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Extrapolation to 19% plugging (using the conser-vative relationship of 1% flow reduction for 3%

tube plugging) results in a 1.93% flow reduction.

Therefore, the predicted reactor coolant flow at plugging is 101.5% of the thermal design flow.

(d) The conservative industry accepted error band associated with reactor coolant flow measurements is + 3%. Although the FPL calculated error analysis concluded that this value is somewhat high, the more conservative value of 3% was used for this evaluation.

Subtracting the entire 3% uncertainty from the pre-dicted flow for 19% tube plugging results in the use of 98% thermal design flow in the analysis and ensures that the analysis;will bound the predicted reactor coolant flow.

Question 2 Justify the reduction in the overtemperature hT and overpower hT trip points of 1.4% and 0.9%, respectively, when the flow is assumed reduced by 2%.

Res onse 2 Although thermal design flow has been reduced by 2%, core average temperature at each power level has not changed from the pre-flow reduction values,. However, Delta-T across the core has increased by 2%. To maintain the same core average

.temperature, Tcol~ leg must be reduced and Thot leg increased by an equal amount (<.6 0 F). Since DNB is primarily a function of the maximum coolant temperature, reductions in Tcold leg do not affect the setpoints. Thus only half of the Delta-T change (Thot leg) results in a DNB Penalty. Therefore, the Overtemperature and Overpower Delta-T setpoints need to be reduced by < 1% to account for a 2% flow reduction.

This is accomplished by a 1.37% reduction in the K term 1 t of the Overtemperature Delta-T equation (Kl reduced from

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1.095 to 1.08) and by an actual 1.17% reduction in the first term of the Overpower Delta-T equation (first term reduced from 1.113 to 1.100) .

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(Note: The first term of the Overpower Delta-T equation is shown as 1.11 in the Technical Specifications. Changing this term to 1.10 results in a calculated reduction of 0.9%. The actual value of the first term is, however, 1.113. Consequently, changing this term to 1.100 results in an actual reduction of 1.17%.)

Question 3 Page 2 of the safety evaluation submitted quotes a DNB limit of DNBR = 1.24. Why is this value vsed rather than DNBR ='.1.30?

'Support the use of" this limit.

Res onse 3 The new Technical Specification core limits, which allow for a 2% reduction in the thermal design flow; will continue to ensure that the minimum DNBR for the transients protected by the Overtemperature dT setpoints will be limited to 1.30.

The DNBR limit of 1.24 is the mir imum allowable DNBR for the "L-grid" DNB correlation .(Referez ces 1 and 2). This is the correlation used in licensing the Turkey Point Units. However, for all DNB transients analyzed for the Turkey Point Plants a minimum DNBR of 1.30 continues to be met. The DNB margin bet-ween 1.30 and 1.24 is stil'1 avaiZ.able to offset DNB penalties due to fuel rod bow (References X.,and 2).

REFERENCES

1. Letter to V. Stello, Director, Division of Operating Reactors, USNRC, from C. Eicl=eldinger, Manager, Nuclear Safety Department, Westinghouse Electric Corporation, August 13, 1976.

2. NRC Xnterim Safety Evaluation Report on Effects of Fuel Rod Bowing on Thermal Margin Calculations for Light Water Reactors (Revision I), February 16, 1977.

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K(6576"l tI';-. lt, Illà FLORIDA'POWER 8 LIGHT COMPANY February '8,1>978 L-78-47'ffice of Nuclear Reactor Regulation Attn: Mr. George Lear, 'Chief 2

'Division o'f Operating Reactors, Branch I3 ~

U..S. Nuclear Regulatory Commission E/Jtgg Washington,. D,.C. 20555 8g

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Dear Mr. Lear:

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Re: Site Visit Fire Protection Program Evaluation Turkey Point Units 3 .and 4 Docket Nos. '50-250 .and50-251 Your letter of February 7, 1978 requested that the NRC Fire Protection Review Team visit the Turkey Point Plant during the week of February 13, 1978. 'The conditions at the plant., however, make that week very inconvenient for us..

As you know, Turkey Poi;nt Unit 3 is scheduled to return to service following a refueling ',o'utage during that week. Also, Unit. 4 is currently scheduled to undergo a steam generator inspection at that

.time. Because of the activities associated',with the startup of Unit 3'nd the inspection of Unit 4, it, is difficult for .us to make the appropriate personnel available to assist with your review. We would be more able to support, your effort during the week beginning March 27,. 197,8'.

lj7e understand that you will complete your review of our Fire Protection Reevaluation Report in the near future. We would appreciate receiving any. questions which were identified during your review by February 27, 1978 i.'f the Review .team intends to,discuss our report during their visit.

Your ery truly, obert E'.:Uhrig Vice President REU/NLR/lec 780460035 cc:. 'Robert Lowenstein, esq..

J. P:. O'ei;1 ly., Region 'l 4aod S III'/o PEOPLE... SERVING PEOPLE

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