ML20148J280

Safety Evaluation Supporting Amend 37 to License DPR-3

ML20148J280
Person / Time
Site:	Yankee Rowe
Issue date:	03/31/1977
From:	Office of Nuclear Reactor Regulation
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NUDOCS 8011210666
Download: ML20148J280 (8)

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. SAFETY EVALUATION BY THE OFFICE OF NUCLEAR' REACTOR REGULATION SUPPORTING AMENDMENT N0. 37 TO FACILITY OPEMTING LICENSE NO. OPR-3 YANKEE ATOMIC ELECTRIC COMPANY YANKEE NUCLEAR '0WER STATION (YANKEE-RCdE)

DOCKET NO. 50-29 j_ntroduction By letter ' dated March 2,.1977, Yankee Atomic Electric Company (YAEC) requested a changa 'to the Yankee . Nuclear Power Station (Yankee-Rowe)

Technical Specifications. YAEC's proposed change relates to extending the Y!akee-Rowe Technical Specification burnup dependent figures from the present limit of 38p effective full power days- (EFPD) to 500 EFPD.

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( Discussion The proposed change consists of revisions to the Yankee-Rowe Tcchnical Specifications which will provide limiting conditions for operation up to 500 effective full. power days (EFPD) for Core XII. This change i involves figures 3.2-1,' 3.2-3, and 3.2-4 of the Technical Specifications which define the limiting peak liner heat generation rate, the multiplier to account for xenon redistribution, and a multiplier for reduced power operation. All three parameters are functions of fuel burnup. The current Technical Specification curves are limited to 389 EFPD. YAEC proposed j.

etinding these curves to 500 EFPD to facilitate operation beyond 389 LW during the planned power coast down at the end of Cycle XII.

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! An additional Loss-of-Coolant Accident (LOCA) analysis was performed for the new end of core life to define the limiting linear generation rata (LHGR) for operation between 389 and 500 EFPD, Evaluation The allowable fraction of full power for Yankee-Rowe is determined by the following relationship:

Limiting LHGR Allowable fraction of full power =

Peak full power LHGR 8011210 b l

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~I where the limiting LHGR is determined by LOCA analyses and the peak full power LHGR includes eight factors,_ one of which is a multiplier for xenon ,

redistribution which-is a function of core lifetime. In addition if >

control rod group A is inserted below 75' inches, allowable power may not be regained until_ power has been at a reduced level for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> i with control rod group A between 75 and 90 inches. The reduced power level is the allowable fraction of full power times a multiplier which is a function of core life. An exception to this is if the rods are inserted below 75 inches and power does not go below the reduced power level calculated'above, the power must be held at the lowest attained power level for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with control rod group A between 75 and 90 ,

inches before returning to ellowable power. ,

The three factors, limiting linear heat generation rate, Xenon re-  :

distribution and reduced power level are functions of core lifetime and ,

therefore were revised to accommodate extending Core XII life beyond -t the previously defined end point of 389 EFPD. Each of these factors will be discussed separately below.

Limiting Linear Heat Generation Rate To establish the limiting LHGR, a LOCA analysis was conducted using fuel burnup conditions of 500 EFPD. The Yankee-Rowe limiting LHGR is burnup dependent and varies throughout the core life. Fuel heatup analyses were conducted for both the Exxon fuel which was fresh at the beginning of Core XII and the Gulf fuel which was present in Core XI. The new end of life peak clad temperature for the Exxon fuel was predicted to be 1590 F ar.d for the Gulf fuel 1498 F. The corresponding limiting LHGRs were 7.5 and 6.7 Kw/ft respectively. No attempt was made by YAEC to optimize the

'4miting LHGRs by incrementally increasing the LHGR until temperature aits were approached. The limits calculated will pennit coast down from 389 EFPD at the planned rate of 2.27 megawatts thermal per day to approximately 6E% of licensed power. Table 1 presents end of life LOCA analysis results ano Figure 1 shows the revised limiting LHGR curves. We conclude that the .

revised limiting LHGR curves are acceptable.

Xenon Redistribution Factor YAEC submitted a proposal for a burnup dependent xenon multiplier on February 19, 1976, and a supplement to this proposal on March 3,1976.

This submittal also included a hold requirement at low power following control rod insertion below 75 inches based on measured xenon transient characteristics for Yankee-Rowe. The proposed xenon multiplier varied from one oercent (1.01' at the beginning of core life to six percent (1.06) at the end of core life (389 EFPD). This proposal was approved and t.as issued as Amendment No. 23

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r to the Yankee-Rowe Operating License on March 17, 1976. The present proposal involves linearly extrapolating the xenon redistribution factor out to the newly defined end of life (from:389 to 500 EFFD).

Figure 2tshows the proposed extrapolation along-with the calculated data  !

- points obtained using the computer code SIMULATE.~ The SIMULATE' code was verified by comparing predictions with data taken from a test conducted ,

at Yankee-Rowe on December 30'and 31,1975, and reported in YAEC Report l No. 1098 dated March 1976. Comparison between calculated and experimental  ;

data showed good agreement.

It appears from Figure 2 that if a curve were drawn through the data points' j

- and extended.to 500 EFPD,.that it would approach the Technical Specifi- ,

cation value. We have considered a ' calculated factor at 500 EFPD and find i that the xenon redistribution factor will not be above the Technical Specification- value, furthermore, we have considered that the xenon-multiplier was calculated for full power operation and that beyond '389- 1 EFPD the power will' be declining as the plant coasts down which would reduce severity of any' xenon transients. We therefore' conclude that linear extrapolation of the xenon redistribution factor is acceptable.

Reduced Power Level Factor i

The reduced load multiplier is applied to offset the increase in peaking l which could be induced by an increase in power level combined with control '

rod withdrawal from below to above the full power insertion limit. This reduction in power for a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period allows sufficient time for the initial xenon redistribution to accommodate itself to the new power dis-tribution. The reduced load multiplier was determined from a series of typical xenon transients using the SIMULATE model for Core XII beginning of cycle, middle of cycle and end of cycle conditions (based on a cycle length of 389 EFPD) all transients used the critical boron at that time in life. The calculated data and the Technical Specification values are shown on Figure 3. Linear extrapolation of the multiplier to 500 EFPD compare to extrapolation of the data, combined with the consideraiton that power reduction will start at 389 EFPD leads us to conclude that linear extrapolation of the reduced power multiplier is acceptable. t On the basis of our evaluation, we conclude that extending the Yankee-Rowe burnup curves to 500 EFPD is acceptable.

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Environmental Consideration We have determined that the amendment does not authorize a change in l effluent types or total amounts nor an . increase in power level and will  ;

not result in any significant environmental impact. Having made this l determination, we have further concluded that the amendment involves l an action which is insignificant from the standpoint of environmental  !

impact and, pursuant to 10 CFR 551.5(d)(4), that an er.vironmental i impact statement or negetive declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.

Conclusion We have concluded, based upon the considerations discussed above, that:

(1) cecause the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.

Date: March 31, 1977 l

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TABLE 1 Yankee Rowe Core 12 End-of-Core Life L0vA Analysis Surmary of Fesults Break Type 0.6 DECLG Fuel Type __Exxen Golf Rod Linear Heat Generation Rate , kw/ f t 7( 6.7 Peak Clad Te=perature, F 1590.3(3) 1497.9(3)

Peak Clad Terperature Location, Ft. 4.04 4.00

. 30 .22 thximum Local Zg/H2O React. ion,1 lbximum Local Zg/H;0 Reaction Location, Ft. 6.04 4.04

<1 <1 Total Core %g/II 20 Renetion, 7. 500 Burnup , EFI'D 500 (1) Calculations performed at the following conditions:

License Core Power Mwt 600 Power Used for Analysis, FWt 616 Accumulator Water Volume, Ft. 700 Upper Hend Temperature, OF 560 (2) Analysis Pe r Co rmed with' r.NC Return-to-Nocleate Boiling Heat Trans fe r Lockout Model (3) No-Burst Predicted Time Sequence of Events Event Time, Seconds Event 0.0

, Pipe Rupture 0.0 Begin Accumulator Spillage 0.0 Loss of Of fsite Power 7.58 Safety Injection Signal 20.00 Accumulator Injection, Intact Loops 32.58 Safety Injection Pump Flev Start' 33.46 End of Blowdown (E03) 39.54 End of Bypass (E0BY)

Bottom of Core Recovery (BOCRIC) 101.60 Accumulator Empty 109.26 Peak Clad Temperature Reached (Exxon / Gulf) 115.94/135.14

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