ML20216D279
| ML20216D279 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 03/25/1998 |
| From: | Hammer M NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20216D283 | List: |
| References | |
| NUDOCS 9804150241 | |
| Download: ML20216D279 (2) | |
Text
D.
Northern States Power Company Monticello Nuclear Generating Plant l
2807 West County Road 75 Monticello, MN 55362 March 25,1998 10 CFR Part 50 Section 50.90 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Supplement No.1 to License Amendment Request for Monticello Cycle 19 Safety Limit Minimum Critical Power Ratio dated March 13,1998 Attached is a supplement to our March 13,1998 request for an amendment to the Technical Specifications, Appendix A of the Operating License for the Monticello Nuclear Generating Plant.
The purpose of this supplement is to respond to verbal questions from the NRC Staff questioning why the March 13,1998 submittal contained attachments referencing different Safety Limit Minimum Critical Power Ratio (SLMCPR) values for calculations by General Electric (GE) versus reviews by Siemens Power Corporation (SPC).
Cycle 19 consists of 476 GE fuel bundles and eight SPC fuel bundles. The preliminary cycle 19 core design resulted in SLMCPR values of 1.11 and 1.13 for two and single loop operation, respectively.
An extended outage in the summer of 1997 to repiace torus suction strainers combined with a second unanticipated outage in November 1997 resulted in a core redesign and new (final) SLMCPR values of 1.10 and 1.11, for two loop and single loop operation, respectively.
When GE performed SLMCPR calculations for Cycle 19, the eight SPC Qualification Fuel Assemblies (QFAs) were modeled identically to the GE10 fuel which was the primary fuel loaded at the same time as the SPC QFAs. This was the same modeling approach used by GE for past cycle-specific SLMCPR calculations at Monticello. Siemens used the GE10 fuel as a design template against which QFA performance could be matched, so performance of these fuel typeo is similar. SPC was then requested to review the resulting SLMCPR values and confirm that the QFAs were not adversely impacted by the SLMCPRs resulting from these GE calculations. When SPC reviewed the impact of the preliminary Cycle 19 core design, SLMCPR values were 1.11 and 1.13.
l NSP technical personnel concluded that for reasons discussed in the SPC attachment to the March f
13,1998 license amendment request, the SPC review would bound any SLMCPR values falling between the Cycle 18 values of 1.08 and 1.09 and the preliminary Cycle 19 values of 1.11 and 1.13.
l 9804150241 980325 PDR ADOCK 05000263 eQl P
PDR Q) 3/25/98 MHV JOCENSDLAR\\SLMCPR\\SLMCPRSt DOC
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s, USNRC NORTHERN STATES POWER COMPANY March 25,,1998 Pag'e 2 During subsequent internal NSP reviews, it was determined that the maximum difference between the results that SPC reviewed and the SLMCPR values calculated by GE for the final Cycle 19 core design would be treated as a penalty or an additional" uncertainty" for QFA monitoring. The maximum " uncertainty" is 0.02 (1.13 - 1.11) based on single loop operation; (the " uncertainty" would only be 0.01 (1.11 - 1.10) based on two-loop operation.)
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Within the Monticello Cycle 19 3D-Monicore core monitoring databank, each type of fuelis assigned a specific Operating Limit Critical Power Ratio. For the GE fuel, the assigned Operating Limit Critical Power Ratio results from the transient analyses performed by NSP with the SLMCPR calculated by GE. The QFAs are assigned an Operating Limit Critical Power Ratio determined in the same manner but with the additional 0.02 administrative adder discussed above. Actions at Monticello to ensure that Operating Limit Critical Power Ratios are not exceeded are based on the ratio of any individual bundle's Operating Limit Critical Power Ratio within the 3D-Monicore databank to the actual Critical Power Ratio for that bundle. Thus during plant operation the above approach implements a QFA SLMCPR of 1.13 for single loop operation and 1.12 for two loop operation, which bound the values evaluated by SPC.
This submittal contains no new NRC commitments, nor does it modify any prior commitments. Please contact Sam Shirey (612-295-1449) if you require further information related to this request.
If11b Michael F.
mer Plant Manager Monticello Nuclear Generating Plant c:
Regional Administrator-Ill, NRC NRR Project Manager, NRC j
Resident inspector, NRC State of Minnesota l
Attn: Kris Sanda J Silberg
Attachment:
Affidavit to the US Nuclear Regulatory Commission l
i j