ML20248D697
| ML20248D697 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/29/1989 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 89-619A, NUDOCS 8910040366 | |
| Download: ML20248D697 (2) | |
Text
-
9 o
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 Septanber 29, 1989 United States Nuclear Regulatory Commission Serial No.
89-619A Attention: Document Control Desk NO/JDH:jm] R2 Washington, D.C. 20555 Docket Nos.
50-338 50-339 License Nos. ' NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 LARGE BREAK LOCA ANALYSIS INPUT ERROR Virginia Electric and Power Company has completed its evaluation of the impact of the Large Break LOCA analysis input error that was described in our August 21,1989 letter (Serial No.89-619).
That letter also described the temporary operating restrictions which were imposed at that time due to the analysis error.
This letter summarizes the results of our evaluations and confirms that the restrictions that had been imposed on the operation of Unit 1 are no longer necessary. The results of this evaluation were reviewed and approved by the Station Nuclear Safety and Operating Committee on September 19,1989. The operating restrictions were subsequently removed on that date.
The North Anna LBLOCA model has been revised to incorporate a reduced steam generator tube plugging level of 15% and Unit 1 Cycle 8 specific core design inputs that bound current cycle operation. This reanalysis assumed that all LOCA-related Technical Specification parameters were at their most limiting values. The peak clad temperature obtained for this reanalysis is 2193 degrees F, which is below the 10CFR50.46 limit of 2200 degrees F. Operation of Unit 2 for Cycle 7 was evaluated based on the differences in current steam generator tube plugging levels and using current Unit 2 cycle specific core design inputs. This evaluation confirmed that Unit 2 is bounded by the reanalysis for Unit 1. The results verify that Units 1 and 2 comply with the acceptance criteria for LOCA analyses specified in 10CFR50.46 for the duration of the current fuel cycles, Further, the Technical Specifications for which operating restrictions had been applied (i.e., containment average temperature, RWST temperature and heat flux hot channel factor) have been verified to be applicable over their full range.
As a result of this analysis, the allowable steam generator tube plugging limit in any steam generator is 15% for Unit 1 and 11% for Unit 2.
Currently, Unit 1 has a maximum tubo plugging of 13.1% and Unit 2 has a maximum of less than 6%. In the event it becomes necessary to exceed the current plugging limits assumed in this t
HA 38M "!sBaa 1a P
PNU 0
9 L
p 7---
7m-, y y
,y'
,/
analysis l additional LOCA analyses will be required. Additional margin and relaxation
~
from currentlimits on cycle. specific core design inputs is'; expected to be achieved
= through use of the approved Westinghouse BASH large break' LOCA methodology.
f:'
if, you have any questions _ or require additional'information, please contact us
- immediately. -
Very truly yours, l
y M
- . W. L. Stewart Senior Vice President - Power oc:
United States Nuclear Regulatory Commission Region ll :
101 Marietta Street, N.W.
Suite 2900 Atlanta, GA. 30323 Mr. J. L. Caldwell NRC Senior Resident inspector
'. North Anna Power Station j
i I
i l _
'i l
- - _ _ _ _ - - - - - _ _ _ _ _.. _ _ _ _ _ _ _. _ _. - _ _ _ _ _ _ _ _ _ _ _ _ _. _ _