ML20072E678
| ML20072E678 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 06/17/1983 |
| From: | William Jones OMAHA PUBLIC POWER DISTRICT |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| LIC-83-146, NUDOCS 8306270105 | |
| Download: ML20072E678 (2) | |
Text
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o Omaha Public Power District 1623 Hamey Omaha, Nebraska 68102 402/536-4000 June 17, 1983 LIC-83-146 Mr. Robert A.
Clark, Chief U.
S.
Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Division of Licensing Operating Reactors Branch No. 3 Washington, D.C.
20555
Reference:
Docke t No. 50-285
Dear Mr. Clark:
Thermal Shield Concerns for Fort Calhoun Station At Omaha Public Power District's request, C-E Power Systems has completed an analysis of the effects of a dropped thermal shield in the Fort Calhoun Station reactor.
The results of that analysis, as requested by the Commission's letter dated June 1, 1983, are attached.
Please note the results of this analysis do not differ significantly from the preliminary assessment of the Commission's safety evalu-ation which accompanied the above referenced letter.
Sincerely, W. C. pones Division Manager Production Operations WCJ/TLP:jmm Attachment cc:
Le Boeu f, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, N.W.
Washington, D.C.
20036 Mr.
E.
G.
Tourigny, Project Manager Mr.
L.
A.
Yandell, Senior Resident Inspector 8306270105 830617 C[5 PDR ADOCK 05000285 p
PDR lh {
45.5124 Employment with Equal Opportunity Male / Female
Attachment REPORT ON EVALUATION OF A DROPPED THERMAL SHIELD AT THE FORT CALHOUN STATION The District has received a report from combustion Engineer-ing (C-E Report CEN-249(0)) detailing the results' of an evaluation of the mechanical and hydraulic effects of a dropped thermal shield at the Fort Calhoun Station.
This evaluation was referenced in the District's submittal dated April 26, 1983.
The conclusions of the report are sum-marized below.
The evaluation demonstrated that if the thermal shield were to become detached from its supports and drop from its normal position, it could move downward only 1-15/16 inches before contacting the core support barrel snubber spacer blocks.
The impact stresses on the snubber spacer blocks as a result of such a drop would be well within allowable stresses for normal operation.
Failure of the spacer blocks, resulting in a further drop to the core stops, is extremely unlikely.
The evaluation also showed that if the thermal shield drops to the snubber blocks in an upright position, the impacts on i
core inlet flow distribution and system flow rate are negli-gible.
This result applies regardless of the degree of eccentricity of the thermal shield in its dropped position.
If the thermal shield were to drop to a fully eccentric and tilted position, there could be a total reduction in the inlet flow rate to the limiting fuel assembly of 144.
On a conservative basis, this flow reduction could result in a reduction in overpower margin of 14%.
The present overpower margin available to mitigate Anticipated Operational occur-rences is 174.
This is sufficient to offset the impact of the flow reduction resulting from the thermal shield dropping to a fully eccentric and tilted position, without violating the core minimum DNBR limit.
This evaluation has demonstrated that the mechanical and hydraulic ef fects of a dropped thermal shield would not compromise the safety of the Fort Calhoun Station.
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