ML20058M487
| ML20058M487 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 08/02/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058M479 | List: |
| References | |
| NUDOCS 9008100147 | |
| Download: ML20058M487 (4) | |
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UNITED STATES
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E, WASHINGTON, D. C. 20666 J
$g SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMECMENT N0.143 'T0 FACILITY OPERATING LICENSE NO. DPR-32 AND AMENDMENT NO.140 TO FACILITY OPERATING LICENSE NO. OPR-37 VIRGINIA ELECTRIC AND POWER COMPANY i
i SURRY POWER STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-280 AND 50-281
_ BACKGROUND By letter dated October 11, 1988, as superseded by letter dated Octobtr 30, 1989 Virginia Electric and Power Com i
to the Technical Specifications (TS) pany (the licensei) recuested amendments appunded to Facility Operating Licenses No. DPR-32 and DPR-37 issued to the licensee for operation of the Surry Nuclear Power Station, Units 1 and 2 respectively. The prcposed amendments would modify Sections 3.6,3.9and3.16oftheTStoincreasetherequirednumberofa unit's auxiliary feedwater (AFW) pumps required to be available for cross-connect to the opposite unit from ene to two. This increase in the required number of operable AFW pumps would provide an additional margin of safety for common mode failure events.
EVALUATION i
The reest., for the requirement to maintain' operable AFW pumps in the opposite unit is to ensure that in the event of a total loss of all of one unit's AFW pumps emergency cooling to that unit can be provided by the other unit's pumps.
This Is possible since the AFW systems of the two units can be cross-connected.
Each unit has three AFW pumps. Two of these pumps are electrically powered, and the third is steam powered. Under the current TS, in order to exceed 350 degrees F or 450 psig in the Reactor Coolant System for a given unit, one of the other unit's AFW pumps must be operable.
Thus, in the event of a comon mode failure of all of a unit's AFW pumps, a single failure in the oppor te unit's available AFW pump could result in a loss of all AFW to the operating unit. The proposed changes would require that before a unit exceeds the pressure and temperature limits of the Residual Heat Removal System, two of the AFW pw:ps in the opposite unit be operable.
In addition, the proposed changes would require that before operating a unit, L
two redundant trains of emergency power and supporting equipment be available to power the motor-driven AFW pumps on the opposite unit. This is accomplished by requiring that before taking a reactor critical, the opposite unit's emergency power system be operable, and all four 480v emergency busse be energized.
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The proposed changes also require that one of the two physically independent circuits from the offsite transmission network be available to energize the opposite unit's 4160v and 480v emergency bunses, that the opposite unit's emergency diesel generator be operable, that all four of the opposite unit's E
480v busses be energized, that flowpaths for supplying fuel to the diesels be operable, and that two station batteries, two battery chargers, and the DC 7
distribution system be operable.
These requirements enhance the overall availability of power to the emergency busses of the ^Mositt unit.
The licensee performed a probabilistic risk assessment to determine the allowable time that the AFW system in the opposite unit could be inoperable, provided that immediate actions were taken to effect repairs.
Based on this assessment it was determined that if an emergency power train on the opposite l
unit werr-i wed to be inoperable for up to 14 days, the contribution to core damage r1
- ould be negli9 bb.
Thus, the proposed TS allow for a 14-day i
u period to restore the oH e m anit's emergency power train before a shutdown e
is required.
The analysu Ao showed that, during such a 14-day outage, a subsequent outage with bot. ::mergency diesel generators associated with the shut down unit inoperable would not present any considerable increase in the ri d of core damage provided that (1) offsite power is available to energize one p
train, and (2) the gen w tor is returned to operability within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Thus, my the proposed changes allow a 72-hour period to return the generator to operability before a shutdown is required.
The proposed change increasing the number of the opposite unit's AFW pumps required to be operable, and the associated electrical power requirements, serve to enhance reliability and are, therefore, acceptable. The provisions allow for a 14-day period to restore an inoperable power train to service and, within
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this 14-day period, a 72-hour period in which to restore an inoperable generator in L.ie opposite unit, increase the probability of an event from 1.7E-8 to 3.1E-8 per year. This increase is not considered significant; therefore, the provisions are considered acceptable.
Based on the above, the staff finds the licensee's proposed changes to be adequate and acceptable.
ENVIRONMENTAL CONSIDERAT10N These amendments involve a change to a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. We have determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has t-previously issued a proposed finding that these an.endments involve no significant hazards consideration and there has been no public comment on such finding.
Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
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CONCLUSION
,i We.have concluded, based on the considerationn discussed above that (1) there isLreasonable assurance that the health and si.fety of the public will not be endangered by operation in the proposed manne, and (2) such activities will be
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conducted =in compliance with the Commission's regulations and the issuance of r
these amendments will not be: inimical to the common defense and security cr to at the health and fsafety-of the public.
-Dated: August 2, 1990 Principal Contributor:
G. Wunder i
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' DATED:-
A'uaust 2. 1990
-..? AMENDMENT NO.143 c TO FACILITY OPERATING LICENSE NO. DPR SURRY UNIT 1--
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AMENDMENT NO.140 TO FACILITY OPERATING LICENSE NO. DPR SURRY. UNIT 2-
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