ML17037C242
| ML17037C242 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 04/09/1974 |
| From: | Skovholt D US Atomic Energy Commission (AEC) |
| To: | Schneider R Niagara Mohawk Power Corp |
| References | |
| Download: ML17037C242 (4) | |
Text
Docket No. 50-220 Hiagaxa Mohawk Power Corporation ATTN:
Hr. R. R. Schneider Vice Pxesidont - Electric Operations 300 Erie Boulevard Pest
- Syracuse, New York 13202 Gentlemen:
APR g )g74 Distribution Docket File AEC PDR.
Local PDR Branch Reading JRBuchanan, ORNL DJSkovholt, L:OR
- TJCarter, L:OR ACRS (16)
RO (3)
OGC DLZiemann, L:ORB if/2 CJDeBevec, L:ORB II2
- JLSapir, L:ORB //2 RH)iggs, L:ORB II2
- SVarga, L:RP In a letter dated November 30, 1973, you submitted information concerning the extent and consequences of possible invertod poison tubes in the control blades of the Nine Mile Point Unit 1 reactor.
He have reviewed your submittal along with the associated General Electric generic sub-mittal dated October 8, 1973, and have concluded that without additional supporting evidence the assumption of a homogeneous dofect rate of 5X is not )ustified.
In addition, relatively small groupings of defective blades can pxoduce the maximum undesirable effects.
Therefore, to maintain the current safety margin requirements until an inspection of the xods is performed, we are requiring that the following action be implemented within 15 days after receipt of this letter.
1.
Subtract a value of 0.2X delta k from the current allowable insequence control rod reactivity worth.
2.
Add a value of 10 psi to the maximum pressure calculated for the safety valve sizing pressurization transient and confirm that adequate margin exists.
3.
Establish a procedure to report any observed reactivity anomaly greater than 0.5X to the AEC within 10 days of the observation.
It is important that uncertainties associated with the possible presence of defective control blades be either significantly reduced ox eliminated as soon as practicable.
You should, therefore, inspect a homogeneous sampling of about 50X or more of the control rods during the next refueling outage and complete the inspection of the entire core within the next two refueling outages.
ll II I
Niagara Mohawk Power Corporation
- 2 APR g 797y If the calculated potential shutdmm margin loss (assuming full settling in all the observed inverted poison tubes) extrapolated to include uninspected rods is less than 0.5X delta k, add the calculated value to 0.25/ delta k to obtain the minimum shutdown margin requirement for the following fuel cycle.
You may xeduce the minimum shutdown margin require-ments by the calculated xeactivity uncertainty removed by the replacement.
of defective blades.
If the results of the inspection yield a potenti.al equivalent full-core shutdown margin loss greater than 0.51 delta k, inspection results should be submitted to the AEC for review befoxe the end of the outage and some amount of blade replacement may be required.
Based upon the inspection x'esults and any blade replacements, subsequent restrictions on insequence contxol rod xeactivity worths and pressure margins willbe ad)usted to reflect known core conditions.
In the interim, we strongly encourage the performance of-an inservice inspection of control rods during any shutdown of significant duration before your next refueling outage.
Sincerely, Donald J. Skovholt Assistant Director for Operating Reactors Directorate of Licensing cc:
J. Bruce HacDonald, Esquire Deputy Comnd.ssioner and Counsel New York State Department of Commerce -and Counsel to the Atomic Energy Council 99 Washington Avenue Albany, New York 12210 Axvtn Z. Upton, Esquire LeBoeuf, Lamb, Leiby 5 HacRae 1757 N Street, N. W.
Washington, D. C.
20036 Dr. William Geymoux Staff Coordinator New York State Atomic Fnergy Council New York State Department of Commerce 112 State Street Albany, New York 12207 Anthony ?'. Roisman, Esquire Berlin, Roisnan and Kessler 1712 N Street, N. W.
Washington, D. C.
20036 Oswego Ci.ty Library X740Y SURHAM23v'ATCW L:ORB //
JLSapir: sg 4/8/74 L:ORB I/
CJDeB c
IJ gP~
L:0 DLZiemann c,lf lw L:0 DJ o holt 4/
/7'4 Porm hEC-3ld (Rev. 9.33) hECM 0240 CI'0 CA2 IO 1IA00 I
$20 204
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