ML20094H775
| ML20094H775 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 03/06/1992 |
| From: | Gates W OMAHA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LIC-92-074R, LIC-92-74R, NUDOCS 9203110264 | |
| Download: ML20094H775 (3) | |
Text
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Omaha Public Power District 444 South 16th Street Mall Omaha, Nebraska 68102-2247 402/636-2000 March 6, 1992 LIC-92-074R U. S. Nuclear Regulatory Commission ATTH: Document Control Desk Mail Station Pl-137 Washington, DC 20555
References:
1.
Docket No. 50-285 American Society of Mechanical Engineers (ASME) Winter 1980 2.
Boiler and Pressure Vessel Code Section XI, 1980 Edition, Addenda Letter from Combustion Engineering Owners Group 3.
Hutchinson) to NRC (Document Control Desk) "CEOG(J. J.
Submittal of CEN-412, Relaxation of Reactor Coolant Pump Casing Ins ection Requirements" Dated November 27, 1991 (CE0G 716 4.
ASM Code Case N-481, " Alternative Examination Requirement for Cast Austenitic Pump Casings" 5.
Letter from the NRC (J. T. Larkins) to 0 PPD ( W. G. Gates)
Dated December 18 1991, " Request for Implementation of ASME CodeCaseN-498,EortCalhounStation, Unit 1(TACNo.
M82081)"
Gentlemen:
SUBJECT:
Request for Approval to Implement Provisions of ASME Code Case N-481 Pursuant to 10 CFR 50.55a(a)(3), Omaha Public Power District (OPPD) requests relief from performing the Reactor Coolant Pump (RCP) casing volumetric weld examination (Item B12.10) by Table IWB-2500-1 of Reference 2.and internal surface visual exami B12.20) that are required Raference 3 is the primary basis for this relief request.
The Reference 3 topical report was submitted to the NRC for review on November 27, 1991 by Combustion Engineering. This topical report provides specific analyses of the potential for RCP casing weld failure for six (6) nuclear power plants including Fort Calhoun Station (FCS)
This raport fulfills the evaluation requirement of Reference 4 by providing a persuasive analysis to demonstrate that the failure of the RCP casing welds at Fort Calhoun Station during the Station's lifetime is not a credible event.
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U. S. Nuclear Regulatory Commission LIC-92-074R Page 2 In lieu of the examination requirements of Item B12.10 and B12.20, Reference 4 specified the following alternative examinations:
1.
VT-1 visual examination of the external surface of one Reactor Coolant Pump each 10-year inspection interval.
2.
VT-2 visual examination during the Reactor Coolant System Hydrostatic lest.
3.
VT-3 visual examination of the RCP internals whenever a pump is disassembled for maintenance.
Reference 3 justified use of the alternative examinations noted above based on a significant reduction in radiation exposure to personnel. This would be accomplished without reducing the level of quality or safety of the Reactor Coolant System pressure boundary.
Reference 3 shows the FCS RCP casing integrity to be retained for 175 years under expected service conditions.
OPPD agrees with the conclusion of Reference 3 that the VT-1 visual examination of the external surfaces specified in Reference 4 would not be effective from a risk / benefit standpoint. The VT-1 examination would provide only limited benefit over the analytical demonstration of stability described in the topical report. The removal and replacement of the RCP insulation for access to the external surfaces and the examination itself would result in personnel radiation exposure of approximately 12 man-rem for each RCP.
The VT-2 and VT-3 examinations specified in Reference 4 are considered to be effective and require minimal radiation exposure, since no additional insulation removal is required to perform them.
It is therefore proposed that the analytical results of Reference 3 be accepted as an alternative to the VT-1 examination of the external surface of one RCP casing weld.
Fort Calhoun Station received NRC approval to implement Code Case N-498,
" Alternate Rules for Ten-Year Hydrostatic Pressure Testing Class 1 and 2 Systems" (Reference 5). Therefore, the VT-2 examination would be completed in conjunction with a Reactor Coolant System (RCS) leak test instead of a RCS hydrostatic test.
In summary, OPPD requests relief from the requirements of item B12.10 and B12.20 in Table IWB-2500-1 of Reference 2.
Justification for this relief includes the analysis provided in Reference 3 and performance of the following alternative examinations:
1.
VT-2 visual examination of the RCPs during the Reactor Coolant System leakage test performed in accordance with Item B15.10 of Table IWB-2500-1 of Reference 2 each refueling outage.
2.
VT-3 visual examination of the interior surfaces of the RCP to the extent practical whenever a pump is disassembled for maintenance.
1
9 U. S. Nuclear Regulatory Commission LIC-92 074R Page 3 Approval of this relief request is requested by July 1, 1993. This will allow implementation prior to the currently scheduled fall 1993 Refueling Outage.
If you should have any questions, please contact me.
Sincerely fr..N 5 %
W. G. Gates Division Manager Nuclear Operations WGG/sel c:
LeBoeuf, Lamb, Leiby & MacRae D. L. Wigginton, NRC Senior Project Manager S. D. Bloom, NRC Project Engineer R. D. Martin, NRC Regional Administrator, Region IV R. P. Mullikin, NRC Senior Resident Inspector
.