ML19260A941
| ML19260A941 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 11/21/1979 |
| From: | Burger A Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7912060175 | |
| Download: ML19260A941 (4) | |
Text
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NUCLEAR REGULATORY COMMISSION y
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WASHINGTON, D. C. 20655 November 21, 1979 g.....f Docket No. 50-29 LICENSEE:
Yankee Atomic Electric Company (YAEC)
FACILITY:
Yankee Nuclear Power Station (Yankee-Rowe)
SUBJECT:
SUMMARY
OF MEETING HELD ON NOVEMBER 8, 1979, TO DISCUSS THE ADEQUACY OF THE ELECTRIC DISTRIBUTION SYSTEM VOLTAGES On November 8,1979, members of the NRC staff met with YAEC representatives (the licensee) at the NRC offices in Bethesda, Maryland. The purpose of the meeting was to discuss the licensee's proposed modifications to assure the adequacy of the Yankee-Rowe electric distribution system voltages during all modes of operation. A list of attendees is provided as an attachment.
Th. licensee presented specific details of a previously reported (licensee's letter to the NRC, I&E, dated October 27,1979) potential low electric distribution system voltage condition. This problem was identified as the result of the licensee's computer studies (in response to our letter to all power reactor licensees, dated August 8,1979) to determine if the offsite power system in conjunction with the onsite power distribution system has sufficient capacity to start and operate all safety loads, assuming all ons' ner sources are not available.
The ' dee-Rowe onsite electrical distribution system has three 2400 V buse.;, three 480 V buses, and three 480 V emergency buses for powering the safeguards loads. Two cf the three buses are normally connected to the offsite grid which supplies power to switchyard from the two incoming 115 KV lines.
The third bus is normally powered by the main generator.
When the main generator is disconnected from the third bus, such as during plant startup, this bus is connected to the offsite power by closing the norrrally open bus tie breakers to the other buses.
Af ter startup when the generator is synchronized to the grid, the bus is isolated from the other buses by manually opening the bus tie breakers. The licensee stated that the computer studies indicate an undervoltage problem on the 480 V emergency buses, when all three buses are tied to offsite power (with the tie breakars closed as during startup).
However, the studies confirmed an adequate voltage ' level on the emergency buses during all modes of operation vnen the. third bus is supplied from the generator with the bus tie breakers open. The licensee stated that two approaches had been considercJ to correct this potential voltage degradation problem:
(1) prucedurally, by load shedding, or (2) by use of voltage regulators.
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- The licensee is proceeding with the preferred approach 2.
One voltage regulator will be instelled on the low side of the No. 2 and No. 3 115 KV - 2.4 KV station service transformers. The licensee stated that based on the voltage computer analyses these regulators are capable of maintaining an adeq6 ate voltage l' vel on the 480 V emergency buses (for e
starting aad running the emergency core cooling system pumps) during all modes of plant operations including plant startup. The licensee indicated that they have also evaluated the effect of this modification on the station service transformers. The evaluation confirmed that use of the voltage regulators will not cause exceeding the rating of the transfonners.
The licensee stated that the two 250 KV voltage regulators will be supplied by Allis-Chalmers and that engineering, installation of the regulators and tie in of the regulators to the onsite grid (during a weekend plant shutdown) will be accomplished within three weeks from the date of this meeting.
For assurance that all 480 V emergency buses are supplied with adequate voltage during all modes of operation, the licensee has in effect administrative procedures. These procedures require a designated operator in the control room to open the bus tie breakers if a safety injection actuation signal is received. This procedure will remain in effect in the interim period until the new voltage regulators are tied to the grid. The licensee also agreed as an additional interim measure to arrange for direct communication between the control room operator and the dispatcher. This allows rapid exchange of information on impending critical conditions on the grid and to alert the dispatcher to take reasonable action to improve the grid voltage condition. The staff considers the above described actions for resolving the reported undervoltage condition of the 480 V emergency buses to be acceptable. The licensee agneed to confinn these actions in a letter to the NRC. The licensee also confirmed that they will provide by mid-December 1979 a complete written response to our August 8,1979 request relating to the adequacy of the electric distribution system voltages at Yankee-Rowe.
jA Alf d Burger, Project Manager Operating Reactors Branch #2 Division of Operating Reactors
Attachment:
List of Attendees cc w/ attachment:
See next page 1510 271
. cc w/ attachment:
Mr. Lawrence E. Minnick, President Yankee Atomic Electric Company 20 Turnpike Road Westboro, Massachusetts 01581 i
Greenfield Community College 1 College Drive Greenfield, Massachusetts 01301 Mr. Robert H. Groce Licensing Engineer Yankee Atomic Electric Company 20 Turnpike Road Westboro, Massachusetts 01581 i
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ATTACHMENT LIST OF ATTENDEES NOVEMBER 8, 1979 YAEC F. D. Baxter R. T. Turcotte D. Moody B. L. Drawbridge P. Johnson NRC M. Chiramal I, Ahmed W. Lazarus D. Tondi A. Burger G. Lainas 1510 273 P