ML20058H284
| ML20058H284 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 11/03/1990 |
| From: | St Laurent N YANKEE ATOMIC ELECTRIC CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| BYR-90-147, NUDOCS 9011150125 | |
| Download: ML20058H284 (3) | |
Text
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YANKEE M0MIC ELECTRIC COMPANY r.,.-,n..,
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ON HC87 Box 160, Rowe Massachusetts 01367 sf FF.
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, TAN KEE November 3, 1990 I
BYR 90-147 i
i Office of Nuclear Reactor Regulation f
United States Nuclear Regulatory Commission Washington, DC 20555 l
l Attention:
Dr. Thomas E. Murley, Director
References:
(a)
License No. DPR-3-(Docket'No. 50-29) i
Subject:
Maintenance Activity for Current ' Yankee Nuclear.
i Power Station Outage i
l Dear Sir In a recent telephone communication with. NRC staff,-Yankee personnel provided a description of a maintenance activity to be l
performed during the current maintenance outage.
This letter provides a written description of the maintenance activity.
l On November 1,1990, during a reactor startup after a refueling 1
- outage, control rod number twenty four (24) was found to be j
disconnected from its drive shaft.
Control rods in the Yankee l
reactor are top driven, cruciform blades suspended from a drive shaft and dash pot mechanism.
They are attached to the-drive shaft by spring loaded fingers operated by a small shaft runnir.3 down the i
l center length of the drive shaft.
With the determination that i.he l
control rod was not latched to the drive shaft,-an orderly plant shutdown and cool down were initiated.
The plant is currently in Mode 5 with the main coolant temperature -less than 140 degrees l
Fahrenheit and the main coolant loops and reactor head vented to the low pressure vent header.
Operation in Mode 5 does not constitute refueling operations.
l Refueling operations begin with entry into Mode 6 which occurs when the first reactor head stud is de-tensioned.
Refueling operations cease when the last reactor head stud is tensioned.
In the current l
configuration, with the reactor head in place and all reactor head studs fully tensioned, the routine method of handling drive shafts to latch onto control rods is not feasible.
The reactor ~ head prevents proper location of' the manipulator crane and universal i
handling tool above control rod twenty four.-.Thus, j
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1 9011150125 901103 i
PDR ADOCK 05000029 S
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United States Nuclear Regulatory Commission November 3,1990 Attention: Dr. Thomas E. Murley, Director Page 2 BYR 90-147 1
the operability requirements of Technical Specification LCO 3.9.6, the manipulator crane and universal handling
- tool, are not applicable.
A maintenance evolution has been developed to latch the control rod to the drive shaft.
Access to the drive shaft latching-mechanism can be gained by either removing the reactor head or by removing the individual control rod housing.
Based upon thw approximately 28 man-rem needed to remove and install the reactor head and the length of time necessary to perform that evolution, Yankee has chosen the latter option to latch the control rod.
After removal of the housing and the control rod drive mechanism a manual 3atching tool suspended from an auxiliary hoist will be used to latch the control rod.
It is anticipated the latching evolution will be initiated on November 3, 1990 after 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />.
This maintenance effort involves activities similar to those conducted during refueling.
Therefore, the following administrative controls will be implemented.
1.
Per Technical Specification 3.1.1.2 the -main coolant boron concentration has been adjusted to provide a shutdown margin of at least 5% delta K/K with the most reactive rod fully withdrawn.
This boron concentration is 2147
?pm and the current main coolant boron concentratnon is greater than 2300 nom.
2.
Containment refueling integrity will_ be established during removal of the control rod housing, latching the control rod and re-installation of the control rod housing.
3.
Refueling communications will be established during all activities involving potential rod movement.
4.
A licensed senior reactor operator (SRO) will be prest A at the job site during all activities involving potential rod movement.
5.
Neutron flux -monitoring will be consistent with the requirements applied during refueling activities.
r 6.
Handling equipment will be load tested prior to use.
l 7.
Handling tools and hoist loads will be administrative 1y l
controlled to minimize the possibility for overload.-
8.
All operations associated:with the control: rod latching will be conducted in accordance with PORC approved 1
01:58PM -ANKEC ATOMIC ELEC (
',. NOV 05 '90 United States Nuclear Regulatory Consission November 3,,1990 Attention: Dr. Thomas E. Nurley, Director Page 3 BYR 90-147 procedures which have had a 10 CFR 50.59 review.
>t 9.
The control rod drive shaft and absorber assembly will be manipulated and lifted only to the extent necessary to verify the latch mechanisa le engaged.
Yankee Atomic Electric Ceapany has developed 'a maintenance i
evolutien to latch control red twenty-four to its drive shaft.
Wo.-
trust the information presented is sufficient to define the process i
and the controls in place to properly complete the maintenance. We will continue to keep you informed of the progress of this maintenance evolution through the USNRC Resident Inspectors.
very truly yours,
~
i YANKEE ATONIC ELECTAIC COMPANY k & 0 hM'4 N. N. St. Laurent Plant Superintendent
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cc. USNRC Region 2 USNRC Resident Inspector, YNPS USNRC, Division of Reactor Projects - I/II Project Directorate 1-3 1
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