ML20202E148
| ML20202E148 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 02/09/1998 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20202E152 | List: |
| References | |
| 98-051, 98-51, NUDOCS 9802180084 | |
| Download: ML20202E148 (6) | |
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VIMOINIA ELECTHIC AND POWER COMI%NY Iticuxoxo, VIRGIN 1A 20061 February 9, 1998 U.S. Nuclear Regulatory Commission Serial No.98-051 Attention: Document Control Desk NL&OS/ETS R2 Washington, D.C. 20555 Docket Nos.
50-338 50-339 Licence Nos. NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NQRTH ANNA POWER STATION UNITS 1 AND 2 TECHNICAL SPECIFICATION CHANGE EDG ALLOWED OUTAGE TIME r
REQUEST FOR ADDITIONAL INFORMATION in a January 13,1998 telephone conference call, the NRC Staff requested additional information to continue their review of our proposed Technict.1 Specification change for Emergency Diesel Generator Aliwed Outage Tirres. A response to each question is provided in Attachment 1 to this letter. The NRC also recommended administrative changes (e.g., revision bars, punctuation, etc.) in the November 18,1997 submittal.
Those administrative changes are provided in Attachment 2 to this letter.
A Technical Specification change to require a Configuration Risk Management Program (CRMP) is being evaluated and will be submitted by separate correspondence following completion of intemal reviews.
-If you have any. questions or require additional information conceming this matter, please contact us.
Very truly yours, 6-vu I
l James P. O'Hanlon Senior Vice President - Nuclear
,l Attachments o
._, v v v o Commitments made in this letter:
1.
Submit Technical Specifications change to require a CRMP.
DO O O 0338 p
PDR i
. U.S. Nuclear Regulatory Commission cc:
Region ll Atlanta Federal Center -
61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia ~ 30323 Mr. M. J. Morgan ' _
NRC Senior Resident inspector North Anna Power Station E
s l' I
- 4. a
4 Response to Request for Additiontiinformation t
RESPONSE TO NRC QUESTIONS EDG AOT TECHNICAL SPECIFICATION CHANGE Questions associated with Nov. 18.1997 RAI resoonse Question:
On page 3 (Last Sentence,1st ): re "Once the maintenance has been initiated, then on-line maintenance risk evaluations limit the equipment which can be simultaneously out of service."
How are these on line maintenance risk evaluations performed?
Answer:
This sentence refers to the fact that once the maintenance activity has been evaluated for PRA risk significance by the Supervisor of Station Scheduling using tne on-lhe maintenar 9 matrix, it is submitted for management concurrence as a specific configuration on the plan of the day. When the plan of the day is signed by the Assistant Station Manager Operations and Maintenance it becomes the only configuration which can be worked at that time. A configuration which is a subset of the approved configuration could be worked since the risk evaluation would.be bounding. If emergent work results, once work on the planned configuration is l
initiated, the on-line maintenance matrix "config+1" columns are used to reclassify the work window colcr. The Technical Specifications requirements for operability of redundant systems or equipment are also satisfied.
Question:
-On page 4 (First sentence,2nd ): " impact the core damage frequency..."
Should this be frequency or probability?
Answer:
We are referring tc minimizing risk by restricting the change in core damage frequency to an acceptable interval that the equipment can be removed from service. The acceptable interval is detemiined by using a 1E-6 change in core damage probability limit ac suggested in the EPRI PSA Applications guide. So, probability is the correct word.
f 4
. Question:
On page 6 (Last sentence,1st ): "... no equipment is unavailable..."
Does this mean no equipment in the configuration is unavailable or all eauioment is available?
Answer:
The phrase means that all equipment is assumed operable in the initial risk evaluation as compared to the change in risk when all components in the configuration are assumed to be inoperable. A configuration is one of the entries in the on-line maintenance matrix that has been analyzed using the PSA model.
Question:
On page 2, Question 4 "The EDG battery has been verified to operate under Station Blackout Conditions for the four (4) hour event. The load profile assumes three (3) unsuccessful P.atomatic starts (due to mechanical problems), followed by a continuous P $ and a 1 aal successful start at the end of the four (4) hour duty cycle. Field %shing will occur only upon successf'il mechanical start."
Did we assume that the EDG field flashing would occur on the failed start attempts?
Answer:
As stated in our original response, the only time the field flash was assumed to be required was on the final attempt to start the EDG at the end of the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> duty cycle. The EDG logic is such that for unsuccessful starts where the EDG does not attain a speed of 250 rpm or higher, the field flash'.ng will not occur. Mechanical problems were assumed to preclude the EDG from attaining the speed of 250 rpm.
General Electrical' Distribution Question:
- Question:
The NRC_was concerned about how we responded to IEIN 97-21, " Availability of Alternate AC Power Source Designed for Station Blackout Event," dated April 18, 1997.
Answer:
The SBO DG batteries are capable of starting the diesel within one hour of loss of offsite power. However, the design base scenario assumes that prior to the SBO event the SBO DG !s not running ar.d the AAC support loads are energized. Issues involving extended loss of offsite power to the diesels are outside the design basis, i
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