ML19262A918
| ML19262A918 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 12/03/1979 |
| From: | Moody D YANKEE ATOMIC ELECTRIC CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| TASK-08-01.A, TASK-8-1.A, TASK-RR 791208, WYR-79-149, NUDOCS 7912110314 | |
| Download: ML19262A918 (2) | |
Text
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Telephone 617 366-9011 na 710 390-0739 YANKEE ATOMIC ELECTRIC COMPANY a.
2 1 WYR 79-149 20 Turnpike Road Westborough, Massachusetts 01581
.Yamass
~~
December 3, 1979 United States Nuclear Regulatory Commission Washington, DC 20555 Attention:
Mr. Dennis L. Ziemann, Chief Division of Operating Reactors
References:
(1) License lo. DPR-3 (Docket No. 50-29)
(2) USNRC Letter to all Power Reactors dated August 8,1979 (3) YAEC Letter to USNRC dated October 27, 1979 (4) YAEC Letter to USNRC dated November 1,1979 (5) YAEC Letter to USNRC dated November 16, 1979
Dear Sir:
SUBJECT:
Voltage Regulator Installation Reference (3), reported as LER 50-29/79-26, a potential under voltage problem when Yankee Rowe was operating with certain bus tie breakers closed.
A meeting was held with NRC staff on November 6, 1979, to discuss this potential problem and propose hardware modificetions to correct same. It should be stressed that the potential undervoltage problem could only occur if certain bus ties are closed and a safety injection signal is received while the offsite grid voltage is at the minimum expected value. Technical Specifications require that chese bus ties be open while the plant is above 30 MWe, therefore, this potential problem does not exist above 30 MWe, As stated in reference (4), interim operating procedures have been implemented to assure that safety-related busses are supplied with adequate voltage at all times.
Reference (5) described the modification proposed by us to correct this potential problem. This modification included the installation of voltage regulators to our 2400 volt system. Engineering, materials procurement and onsite work have progreased simultaneously.
The proposed voltage regulators will be in place and all preparatory work completed by December 8,1979 To date, this work has been continuing on a seven day per week basis and every effort to install the equipment has been accomplished in an expeditious manner.
All of this work has been performed under adverse outdoor uceking conditions.
1528 075 7R12110 f
O United States Nuclear Regulatory Commission December 3, 1979 Attention:
Mr. Dennis L. Ziemann, Chief Page Two The initial design phase scheduled the final ties to be made over a four day period and called for removing one line at a time from service as allowed in Technical Specifications.
Recently, during the final engineering review it became evident that due to the magnitude of alterations to the existing bus duct with the equipment de-energized, the plant would have to be brought to cold shutdown for approximately two weeks. These alterations will include substantial cutting and modification to the existing busses and duct work. Duct risers will be installed at the termination points of the bus ducts to enclose the cable terminations.
Four 750 MCM cables per phase will be terminated within these duct risers. All of the above alternatives must be accomplished with the busses de-energized.
In Arder to minimize thermal stresses on our primary system and avoid a two week outage during system peak load demand we request to make the voltage regulator final ties and the modification operation.31 in mid-January of 1980. This also will coincide with our plan to implement certain equipment modifications as required by NUREG 0578.
If an unexpected cooldown were to occur between now and mid-January, we will remain in a cold shutdown condition until the voltage regula. tor modification is operational.
Additionally, should a plant trip be experienced during this period, which because of its nature will require the plant to remain off line for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or more, then the plant shall remain off line until the modification effort is completed.
We trust that you find this information satisfactory; however, should you desire additional information, please contact us.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY E. Moody Manager of Operations dmp 1528 076 e