ML20215C284

Forwards Change to Significant Hazards Consideration for License Change Application 146.Change Quantifies Reduction in Excess Shutdown Margin Expected by Inserting All Control Rods to 226 Steps

ML20215C284
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	12/08/1986
From:	Lindblad W PORTLAND GENERAL ELECTRIC CO.
To:	Varga S Office of Nuclear Reactor Regulation
References
TAC-63526, NUDOCS 8612150088
Download: ML20215C284 (2)

Text

. _ . .

, A'

.gj? '.

PORTLAND GENEMAL ELECTRIC CourANy 121 S. W. S ALuow syngry -

WILLIAM J. LIN DBLAD . PoRTLANo OREGON 97204 (503)226-8875 December 8, 1986.

Trojan Nuclear Plant Docket 50-344 License NPF-1 Director of Nuclear Reactor Regulation ATTE: Mr.~ Steven A. Varga Director, PWR-A Project Directorate.No. 3 U.S. Nuclear Regulatory Commission Washington DC 20555

Dear Mr. Varga:

License channe Application 146 Pursuant to our discussion with your staff concerning LCA 146, attached is our change to the Significant Hazards Consideration for this LCA. . This change

. quantifies the reduction in excess shutdown margin expected by inserting all control rods to 226 steps.

Sincerely,.

he N

- O c: Mr. Lynn Frank, Director State of Oregon Department of Energy Mr. Michael J. Sykes Chairman of County Commissioners 8612150088 t' OD PDR ADOCK861208 05000344 p.

PDR 1 P

4- ,

& ~

. LCA 146 Page 2 of 3 A similar change to the Point: Beach Nuclear Plant' technical specifica-

~

.x :tions was approved-by the NRC in Reference 2. '

4 SIGNIFICANT WATAanS'CONSIDgEATION DETERMINATION'-

.This change does not involve a'significant increase in the probability

-or' consequences of an. accident. Rod insertion is limited to ensure

-that: -(1) power distribution limits are met, and (2) minimum SHUTDOWN

~ MARGIN is maintained. No change ~is' proposed-to.either the power

~

distribution related.. limits (TTS 3/4.2) or the minimum SHUTDOWN MARGIN

-(TTS 3.1.1.1). This chango does not alter the conclusions of the reload safety evaluation performed for Cycle 9.

'This change does not create a new or different kind of accident.

. Changing the definition of " fully withdrawn" to >225 steps as-opposed to 228 steps does not affect power distribution limits nor the minimum SHUTDOWN MARGIN. . Since these limits are unaffected, a new or different kind of accident is not created.'

This change does not significantly reduce a margin of safety. Because of the low rod worth in the top region of the core, the proposed change has a negligible impact on power distribution. Similarly, the effect on shutdown margin is minimal, and can be accommodated by available excess ,

shutdown margin. At the most restrictive end-of-life condition, there is typically about 400 pcm or more excess shutdown margin available. The insertion of all control rods to 226 steps will reduce the amount of available excess shutdown margin by only about 4 to 6 pcm. Sufficient peaking factors and DNB margin are available to accommodate this small .

perturbation in power distribution, which is not expected to be notice-able. The minimal impact on excess shutdown margin and power distribu-tion is insignificant when compared to the major improvement to control rod mechanical integrity afforded by this change. The current Cycle 9 reload.' safety evaluation (Reference 3) indicates-that there is no impact on the accident evaluation for Cycle 9 by inserting all control rods to 226 steps, i ,

ii In the April 6, 1983 Federal Register, the NRC published a list of exam-l pies of amendments that are not likely to involve a significant hazards i consideration. Example No. 6 of that list applies to the changes proposed herein and states:

i "A change which either may result in some increase to the probability F_ or consequences of a previously analyzed accident or may reduce in l- .some way a safety margin, but where the results of the change are clearly within all acceptable criteria with respect to the system or component specified in the Standard Review Plan, es, a change resulting from the application of a small refinement of a previously used calculational model or design method."

Based on the above evaluation, the proposed change does not pcss a g

t significant hazard.

f\

i g~ ..,,.n , - , , - . , . - ..._, , . , . . ,__ - - , . . . . , , . . - ,- ---