ML20066H597
| ML20066H597 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 02/14/1991 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 91-067, 91-67, NUDOCS 9102210202 | |
| Download: ML20066H597 (2) | |
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VIROINIA Elmcritic ann Powr:n CourANY j
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11:enxoxu,VanoistA enuoi February 14,1991 United States Nuclear Regulatory Commission Serial No.
91 067 Attention: Document Control Desk NL&P/JYR:jdhR3
. ashington, D.C. 20555 Docket Nos.
50-338 W
50 339 License Nos. NPF 4 NPF 7
'a Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY RORTH ANNA-POWER-STATION UNITS 1 AND 2 HEATUP AND COOLDOWN -CURVES
'.The current North ~ Anna Unit 1 and Unit 2 heatup and cooldown curves are valid to 10 Effective Full Power Years (EFPY). The Unit 1 curves are estimated to expire in March 1993 and the Unit 2 curves in March 1994. During the latter part of 1989 and early 1990, post-irradiation test _ing and evaluation was performed on the reactor vessel n
> material specimen _s contained in the "U". Unit 2 surveillance capsule. Capsule U had.
been withdrawn from Unit-2 in' March 1989. Revised heatup and cooldown curves applicable to 17 EFPY were developed to account for the additional surveillance data.
In!a letter dated March 8,1990, we committed >to submit technical specification
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changes by, March.15,1991 10 implement revised heatup.and cooldown curves and low temperature overpressure protection system (LTOPS) setooints. It was expected
~ hat this interval provided us with sufficient time to complete the analyses, reports, and t
- draft documentation changes needed_ to implement revised curves and setpoints applicable to an extended cumulative core burnup..However, two issues-have recently be.en identified which require us to revise the date for submitting the proposed
~ hanges.
c First,'it was expected that ample operating margin would exist in the Unit _2 heatup and cooldown curves after incorporating the Capsule U results to support extending the
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applicability of th_e curves to an average core burnup to 17 EFPY. (A revision to 17-
' EFPY-was attempted because 17 EPFY is 2 EFPY beyond the removal date of the next -
Unit 2 surveillance capsule. That additional 2 EFPY period would have provided r
sufficient time for analysis, submittal, and NRC review and approval of needed-technical specification changes without any interim changes to the curves.) However,-
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for. core. burnups this far in the future, the form _of the LTOPS setpoints (i.e., step -
function) results in insufficient operating margin at low pressure and-temperature operating conditions, r
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_ Second, the. Unit 1 heatup'and cooldown curves will expire at the same time the next (surveillance capsule is-removed from Unit 1 (approximately March 1993). Thus,-it is necessary to submit revised UnitL1 technical. specifications sufficiently in advance of
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the next Unit 51: capsule-. analysis to provide adequate timeufor NRC review and I
y approval.
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. Given-these-two. considerations, we now plan to submit technical specification i-
- changes associated with revised heatup and cooldown curves for both North-Anna
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. units by. December 15,1991. This consolidated technical specification change will be submitted sufficiently in advance to support any changes needed for the Unit 1 curves and still provide us with the additional time necessary to revise-the Unit 2 curves so-
- that sufficient operating-margin is. maintained. Because-fluence data from' recent surveillance capsule dosimetry analyses indicates an excellent comparison between F
measured and predicted vessel fluence values, we are confident that the curves and
' limits currently.in-the Unit:1 and 2 technical specifications remain conservative through
- their core' average burnup of 10 EFPY.
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- Very truly y _
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W. L. Ste l rt;
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Senior Vi e President.*:/ clear p
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United States Nuclear Regulatory Commission i.
. Region Il,
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1101 Marietta Street, N.W.-
E Suite 2900 i
Atlanta, Ga 30323 1
Mr. M. S. Lesser f
NRC Senior Resident inspector North Anna Power Station-1 3