ML20154Q624
| ML20154Q624 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/28/1988 |
| From: | Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 88-453, NUDOCS 8810040021 | |
| Download: ML20154Q624 (2) | |
Text
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e VIHO1NIA l$LHCTHIC AND Powan CoupANY HrcaMo xn, VIwo ix A unusit i
September 28, 1988 United States Nuclear Regulatory Commission Serial No. 88 453 Attention: Document Control Desk h !0JV:Jmj i
Washington, D.C.
20555 Doc N No.
50-338 j
License No. NPF-1 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY l
NORTH ANNA POWER STATION UNIT 1 CYCLE LENGTH EXTENSION North Anna Unit 1 is currently in its seventh cycle of operation.
A reload safety evaluation was performed by Virginia Power for the core design prior to the start of Cycle 7.
Based on this evaluation it was determined that the 4
reload did not result in an unreviewed safety question as defined in 10 CFR 50.59, and therefore, NRC approval of the reload was not required.
This information was provided to the NRC in our letter of June 3,1987, Serial No.
1 87-179A.
The purpose of this letter is to request NRC approval of operation I
of the Cycle 7 core with a maximum fuel rod burnup which is in excess of that previously approved by the NRC.
This approval is required as a result of a i
j change in the current fuel cycle length.
As discussed in our letter dated September 12,1988 (Serial No.88-511), the current fuel cycle has recently been extended to April 1989 in order to fully utilize the fuel in the reactor J
and to defer operating and maintenance costs associated with the refueling i
l outages.
h
- I For the revised Unit I
fuel
- cycle, a
limited number of fuel rods (approximately 376 fuel rods or 0.9% of the core) will achieve end-of-life (E0L) burnups greater than the burnup value approved by the NRC in their safety evaluation report for WCAP 10125, "Extended Burnup Evaluation of Westinghouse fuel."
The lead rod burnup is projected to exceed the NRC approved burnup value by approximately 2215 MWD /MTV.
NRC approval is being requested for operation with fuel rod burnups in excess of the NRC approved r
limit.
l Normal operation of either of the North Anna units would typically not result l
l in fuel achieving such high burnup levels.
However, Virginia Electric and Power Company is currently participating in a program with EPRI and i
Westinghouse to obtain data on fuel rod corrosion at high burnups in high coolant temperature commercial units.
As part of this program, eight fue'.
assemblies are being irradiated for their fourth consecutive 18 month operating cycle in North Anna 1.
Four of the.e assemblies are in peripheral locations, but four have been placed in rebtively high power positions to i
achieve high burnup levels.
These high burnup assemblies will achieve assembly average burnups of about 59,100 MWD /MTU under the revised Cycle 7 design.
In contrast, typical lead rod average burnups for recent North Anna i
fuel have been approximately 47,000 to 51,000 MWD /MTV, with batch average fo (
o discharge burnups of approximately 41,000 MWD /MTV.
8810040021 880928 o
DR ADOCK 050 0
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A safety evaluation was performed to assess the impact of operation with fuel j
burnups in excess of the NRC approved limit.
This safety evaluation consisted of a 'Jel performance evaluation to determine if fuel rod design criteria i
would se met at the higher burnup, and an evaluation of the impact of the I
hight burnup on previously analyzed accidents.
Based on this evaluation it i
was c nciJded that the potential consequences of previously analyzed accidents i
1 are not increased by this increase in maximum fuel rod burnup.
The fuel performance evaluation is discussed below.
l The approved version of Westinghouse's high burnup topical report (WCAP 10125-P A) includes data from both commercial and test reactor fuel 4
which has operated to rod average burnups beyond the approved burnup limit.
1 The burnup levels of some of this fuel were comparable to those which the North Anna 1 fuel will achieve during Cycle 7.
These high burnup data indicated that no sedden or unexpected change in performance occurs in progressing to extended burnups.
Therefore, Virginia Electric and Power Company concludes that the Westinghouse fuel performance models and design methods can be extended to the burnups that the North Anna 1 fuel will achieve during this cycle.
Fuel performance calculations have been performed using the Westinghouse fuel performance models for the North Anna fuel, assuming that the unit operates in accordance with the revised outage schedule.
These calculations show the fuel rod design criteria described in Section 4.2.1 of the North Anna UFSAR are satisfied to burnups exceeding the proposed maximum fuel rod burnup.
]
This proposed increase in maximum fuel rod burnup for fuel cycle 7 has been reviewed by the Station Nuclear Safety and Operating Committee and the Safety Evaluation and Control Staff.
It has been determined that the increase does not involve an unreviewed safety question as defined in 10 CFR 50.59.
1 Very tru y
s i
f W. R. Cartwr ght Vice President - Nuclear cc:
U. S. Nuclear Regulatory Commission i
101 Marietta Street, N.W.
Suite 2900 Atlanta, GA 30323 Mr. J. L. Caldwell NRC Senior Resident inspector North Anna Power Station