ML19247B850
| ML19247B850 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 07/05/1979 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Dunn C DUQUESNE LIGHT CO. |
| References | |
| TAC-10007, NUDOCS 7908130640 | |
| Download: ML19247B850 (4) | |
Text
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NUCLE AR REGULATORY COMMISSION
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%, ' v 9 d' July 5,1979 Docket tio, 50-334 Mr. C. ft. Dunn, Vice President Operations Division Duquesne Light Company 435 Sixth Avenue Pittsburgh, Pennsylvania 15219
Dear Mr. Dunn:
In order for us to complete our review of degraded grid voltages on the safety related station electrical buses at the Beaver Valley Power Station, Unit tio. I as submitted by your latest letter dated March 7,1979, we.will need additional information.
The enclosure to this letter addresses the areas needing clarification.
You should submit your response within 45 days following receipt of this letter.
If you have any questions, please contact us.
Sincerely,
', ghhtd4*W A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors
Enclosure:
Request for Additional Information cc: w/ enclosure See next page
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7908130
Mr. C. N. Dunn Duquesne Light Company July 5,1979 cc: Gerald Charnoff, Esquire Mr. James A. Werling Jay E. Silberg, Esquire Piant Superintendent Shaw, Pittman, Potts and Trewbridge Beaver Valley Power Station 1800 M Street, N.W.
P. O. Box 4 Washington, D. C.
20036 Shippingport, Pennsylvania 15077 Kcrin Carter, Esquire Special Assistant Attorney General Bureau of Administrative Enforcement 5th Floor, Executive House Harrisburg, Pennsylvenia 17120 Mr. Roger Tapan Stone and Webster Engineering Corporation P. O. Box 2325 Boston, Massachusetts 02107 Mr. J. D. Woodward R & D Center Westinghouse Electric Corporation Building 7-303 Pittsburgh, Pennsylvania 15230 B. F. Jones Memor'al Lib rary 663 Franklin Avenua Aliquippa, Pennsylvania 15001 Mr. Jack Carey Technical Assistant Duquesne Light Ccapany P. O. Box 4 Shippingport, Pennsylvania 15077 Mr. R. E. Martin Duquesne Light Cemcany 435 Sixth Avenue Pittsburgh, Pennsylvania 15219 Ma rvin Fein Utility Counsel City of Pittsburgn 313 City-County Suilding
?ittsburgn, Pennsylvania 15219
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REQUEST FOR ADDITIONAL INFORMATION BEAVER VALLEY POWER STATION DEGRADED GRID VOLTAGE Upon review of your subuittal of March 7,1979 concerning the staff positions on second level undervoltage protection several areas are in need of clarification.
Specifically:
- 1. Your proposal to add an additional undervoltage relay on each 4160V emergency bus does not satisfy the criterion of staff position 1 of the June 3,1977 letter or of IEEE 279-1971.
Please submit a proposal concurrent with this position.
- 2. The proposed setpoint of 90% voltage at the 4160V bus may not be sufficient.
A review of your voltage analysis dated November 11, 1976, item 1.b., states that when the 4160V bus is at 3320V (91.8%)
the 480V bus is at 394V (82%).
Based on these figures it is interpreted that an approximate 10% voltage drop exists between the 4160V bus and the 480V bus when under load.
Therefore, please furnish a voltage drop analysis by calculation or measurement of the full load voltage at the 480V bus corresponding to the proposed setpoint on the 4160V bus.
- 3. The proposed time delay of 1 minute will> preclude spurious trips for short duration degradations and motor starting voltage drops.
However, it combined with the approximate 80% voltage at the 480V emergency busses may be too long.
Substantiate by analysis that the safety related equipment can withstand this low voltage and time delay without thermal damage.
(As stated in our January 16, 1979 letter, this setpoint reflected down to the 4 emergency busses is below the minimum allowed operating voltage per ANSI CS4.1-1973 and recognized industry practice.)
- 4. Position 2 of the staff's letter of June 3,1977 requires the bypass of load shed features once the cosite power sources are supplying power to the emergency busses.
It also requires the automatic reinstatement of load shedding upon a trip of the onsite supply breakers.
In as much as the starting of large induction motors on the emergency busses can cause large transients in voltage this bypass is necessary.
The undervoltage relay cn the 4160V bus that iniciates load shedding in 3 seconds could cause emergency loads to be shed when they are most needed.
Therefore, include the bypass and auto reinstatement features in your proposed design.
- 5. Yourproposed Technical Specification cnanges do not meet our positicn 1.f.
Namely the limiting conditions for operation, surveillance recuirements, trip setooint with minimum and maximum lim ts and i
alicwable values for the second level undervoltage monitors have not v del Technical Specification been provided.
These changes would follow o
(MTS) format as close ts ;cssible.
See enclosure 2 of the June 3, 1977 letter.
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- 6. Justify why the loss-of-offsite power relays are not on the emergency bus and not designed as a Class lE system when their sole purpose is an engineered safety feature.
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