ML20248L444
| ML20248L444 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/15/1998 |
| From: | Sorensen J NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-06, GL-96-6, NUDOCS 9806110162 | |
| Download: ML20248L444 (4) | |
Text
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orthern States Power Company Prairie Island Nuclear Generating Plant 1717 Wakonade Dr. East Welch, Minnesota 55089 May 15,1998 Generic Letter 96-06 U S Nuclear Regulatory Commission
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Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos.50-282 License Nos. DPR-42 50-306 DPR-60 Summary of Telephone Conference Regarding a Request for Additional Information Related to Generic Letter 96-06," Assurance of Equipment Operability and ContainmentIntegrity During Design-Basis Accident Conditions" (TAC Nos. M96854 and M96855)
The purpose of this letter is to document our understanding of a conference call (April l
29,1998) with NRC Staff. The call was initiated by NSP in order to ensure that we had an accurate understanding of NRC comments contained b an April 10,1998 Request f
e of Additional information (RAl) regarding Generic Letter 96-06, " Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident
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Conditions."
Attached is a summay of the conversation as we understood it. We would appreciate feedback if our summary does not accurately reflect the Staffs understanding of the issues we need to address in our response to the RAl.
In light of the comments contained in the RAI, NSP has evaluated the original operability determination and determined that the conclusions are still valid. The areas which need to be resolved pertain to ensuring that the design basis is satisfied.
9806110162 980515 PDR ADOCK 05000282 P
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C US NRC l
Page 2 5/a5/98 With this letter we have made no new NRC commitments. Please contact Jack Leveille (612-388-1121, Ext. 4662) if you have any questions related to this letter.
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Joel P Sorensen Plant Manager Prairie Island Nuclear Generating Plant c: Regional Administrator - Region lil, NRC 3
Senior Resident inspector, NRC NRR Project Manager, NRC J E Silberg (without enclosures)
Attachment:
Summary of Telephone Conference Regarding a Request for Additional Information Related to Generic Letter 96-06 l
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GL9606,3. DOC
Summary of Telephone Conference Regarding a Request for Additional Information Related to Generic Letter 96-06 On April 10,1998, the NRC issued a Request for Additional information (RAl),
pertaining to the resolution of GL 96-06 issues (water hammer and two phase flow) at Prairie Island (received by NSP April 20,1998). A conference call was held on April 29 at 9 AM CST between representatives from the NRC and NSP to discuss RAI comments in order that NSP may obtain clarification and more detail regarding the comments. The individuals who participated in the phone call are as follows:
NRC: Beth Wetzel NSP: Don Anderson Jim Tatum Jeff Kivl Steve Thomas a.
The numbers below correspond to the comment numbers on page 1 of the enclosure attached to the RAl.
I 1.
NSP needs to provide the documented basis for concluding that the column separation and rejoining analysis is bounding. The specific items discussed are as follows:
Air entrainment - NSP took credit for a small amount of air entrainment; which
- results in a small reduction in the speed of sound used in the Joukowsky equation. NSP considered that this was conservative based on information from EPRI and the evaluations provided in the response to the RAI in September 1997. The NRC would like to see an evaluation demonstrating that this bounds the lowest value of air entrainment which could be experienced at Prairie Island.
Single Failure Evaluation - As part of the analysis and evaluation, NSP considered various single failures. However, this was not detailed in previous information provided to the NRC. NSP will provide a summary of this evaluation to the NRC. The NRC stated that the review should not be limited to the active single failures considered as part of the design basis, but should also look at single failures which could worsen the potential water hammer.
2.
Based on system configuration, experimental evidence and available research documentation, NSP has reasonable assurance that the highest case loadings on the piping will be due to a column separation and rejoining event. However, NSP needs to provide a more rigorous analysis of the potential for different types of water hammer in addition to the column separation and rejoining. The NRC has specific comments related to the experiments performed to substantiate these conclusions:
e Attachm:nt 5/15/98 Page 2 The applicability of the experiments to a fan cooler and associated piping in an actual power plant needs to be demonstrated.
The discussion for how the steam clears the water out of the pipe without flowing over the water is very simplistic. There is no accounting for actual system configurations such as bends, waterboxes, tees, etc.
The experiments do not adequately look at steam generation within the fan cooler unit.
The' scaling is qualitative in lieu of quantitative. The bias due to scale distortion is not quantified.
in summary, the NRC considers that additional work needs to be done to close-out this comment and that it will be a difficult task using the current approach.
Use of a Froude Number of 0.5. NSP believes that, based on ASME
-Transactions paper and EPRI documentation, a Froude Number down to 0.5 is acceptable for ensuring that a horizontal pipe will run full. The NRC wants to be assured that use of a Froude Number below 1.0 is appropriate for Prairie Island.
3.
As part of the Quality Assurance for the PIPEPLUS program, benchmarking has been performed. NSP will explain this in an update to the submittal.
4.
NSP acknowledged that the two phase flow model needs to run for a 93% pump cun/e case and that NSP was waiting for NRC review of the methodology provided in response to the first RAI (September 1997). The NRC stated that they know of no comments on this analysis methodology. NSP stated that, based on this information, NSP will proceed with the additional computer runs.
Evaluation of other effects due to two phase flow (e.g., erosion, cavitation, vibration, etc.)-- NSP stated that its interpretation is that these were long term type effects and that, due to the short duration of the two phase flow condition
- (under the bounding analysis), this was not a significant concern. The NRC stated that NSP cannot rule out the short term effects without characterizing the two phase flow problem and evaluating it's effects on components. The NRC said that they knew of short term detrimental effects (severe piping wastage) in some specific instances. NSP requested reference materiais in this regards since documentation reviewed indicated this was a potential long term concern.
The NRC is checking with the Mechanical Branch for some examples.
GL9606.3. DOC i
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