ML20151A641

Safety Evaluation Supporting Amend 23 to License DPR-3

ML20151A641
Person / Time
Site:	Yankee Rowe
Issue date:	03/17/1976
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20151A635	List: ML20151A632 ML20151A637 ML20151A641 ML20151A643 ML20151A647
References
NUDOCS 8011030818
Download: ML20151A641 (3)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 23 TO FACILITY OPERATING LICENSE N0'. DPR-3 [5E55 YANKEE ATOMIC' ELECTRIC COMPANY. .

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Introduction ~=N By application dated February 19, 1976, and supplement dated March 3, 1976,  ;===-

4 Yankee Atomic Electric Company (the licensee) proposed changes to the .3=L; Technical Specifications appended to License No. DPR-3 for the Yankee-Rowe [T.M.2; 4 reactor. The proposal involves the replacement of the constant multiplier 8,27 for xenon redistribution, specified in Section1D.2.C. (1), Item C, with a 52.+4 burnup dependent multiplier and a hold requirement at reduced power  ;= @ r following deep control rod insertion. di

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Discussion  ;]

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Presently, the licensee is authorized to operate Yankee-Rowe in the 4-loop mode within the limiting Linear Heat Generation Rate (LHGR) in Section J.?5

.D.2.C. (1) of the Technical Specifientions. We have previously concluded- Msi (our Safety Evaluation dated December 4,1975) that operation of Yankee ' t=g Rowe with Core XII in this manner assures compliance with 10 CFR Part 50, fE

!!50. 46. For determining the allowable fraction of full power, Section (,f7 D.2.C. (1) requires that the peak full power LHGR include several penalty ~ ~ 5.'

factors including a 10 percent multiplier to account for the effects of =' C .

, xenon redistributio.n. We found this constant xenon redistribution factor 7 to be conservatively large and acceptable. In their February 19, 1976,

'.4 submittal and the March 3, 1976 supplement, the licensee proposed a ,

burnup dependent xenon multiplier including a hold requirement at low erg =

power following control rod insertion below 75 inches that would be based -  ;

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on the actual xenon transient characteristics of Yankee-Rowe.

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Acceptable control rod insertion limits are specified for Core XII operation i as a function of percent of allowable power. This restricts axial peaking pg=W factors within allowable values, taking into account the required limits on =j shutdown cargin and maximum heat flux in addition to the limiting LHGR g

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imposed by the results of the Core XII Appendix K ECCS performance evaluation I..... -

for Yankee-Rowe. Xenon redistribution which results from power changes due [F" ~

to control rod motion could adversely affect the axial peaking factor. To.  :' .,_

provide assurance that the reactor is operated at all times within the i!!gdC

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limiting LHGR which is directly related to the axial peaking factor, Specification D.2.C requires that the constant 10 percent penalty for f=

xenon redistribution be included to determine'the allowable fraction of pT" full power. The licensee's February 19, 1976 proposal involves the p";;;

replacement of this constant xenon redistribution penalty with a xenon multiplier that varies from one percent (1.01) at the beginning of core " " " -

life to six percent (1.06) at the end of core life as specified in H=: .

Figure 8-4. .In addition, if control rod Group A is inserted below E 75 inches, allowable power may not be regained until power has been at a reduced Icyc1 (using the burnup dependent multiplier specified in -

Figure 8-5) 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 Group A between 75 and -

90 inches. This would preclude xenon transients to cause an unacceptable '

power distribution.  :

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.7 Because Yankee-Rowe has a small core consisting of 76 fuel assemblies it is stable with respect to xenon and any xenon transients are rapidly . [= ~

damped. As further described in detail in the March 3, 1976 supplement, _.

the licensee has obtained data during Core XII operation to validate ,

calculational methods (previously found to be acceptable by us) used p to predict the xenon transient characteristics of Yankee-Rowe throughout ,

the life of Core XII. From our review of the data and information '

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provided in the application for license amendment, we find that the b. ... ..

' calculational methods used by the licensee conservatively predict the k course of xenon transients that result from control rod insertions.

Therefore, these methods are acceptable for the development of the proposed  :

multipliers that account for the effects of xenon redistribution on the b =

peak full power LHGR. These multipliers have been included in the Technical Specification for use to determine the allowabic fraction of full power in E accordance with Section D.2.C. (1) . We also find that the burnup dependent r; multipliers in the proposed Figure 8-4, and the proposed 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> bold at the .

reduced power (in accordance with proposed Figure 8-5) following deep control rod insertions, as previously discussed in this Safety Evaluation, provide

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additional margins to calculated valuer, conservatively account for '

the effects of xenon redistribution and, are acceptable. We have concluded that the proposed change does not involve an increase in the allowable LHGR and consequently does not decrease the margins with respect to the require-ments for compliance with 10 CFR 850.46.

We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this .

determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR 851.5(d)(4) that an environmental statement, negative declaration, or environmental impact appraisal need not be prepared in h(.

connection with the issuance of this amendment.

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j Conclusion  ?::{:.l ,,

5 sis We have. concluded, based on the considerations discussed above, that

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(1) because the change does not involve a significant increase in the  :== a probability or consequences of accidents previously considered and does s===

not involve a significant decrease'in a safety margin, the change does =9

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not involve a significant ha:ards 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 _.,g;3 conducted in compliance with the Comission's regulations and the issuance _ .. . :: . < .

of this amendment will not be inimical to the comon defense and security i-s ~R or to the health and safety of the public. ii. s.e id

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Date: March 17, 1976  ; ))

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