U-603026, Submits Response to RAI Re Illinois Power Response to GL 96-06, Assurance of Equipment Operability & Containment Integrity During Design-Basis Accident Conditions
| ML20249B169 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 06/15/1998 |
| From: | Walter MacFarland ILLINOIS POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20249B170 | List: |
| References | |
| GL-96-06, GL-96-6, TAC-M96796, U-603026, NUDOCS 9806220130 | |
| Download: ML20249B169 (6) | |
Text
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1rnnois Powar Company Chnton Power Stabon PL Box 678 Clanton. IL 61727 Tet 217 935-5623 Fax 217 9354632 Walter G. MacFarland IV Senior Mce Presdent and Cruet Nuc ear Officer ILLINSIS u.6mo26 P9WER so.uo l
An thinova Company June 15, 1998 l
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Docket No. 50-461 1
Document Control Desk Nuclear Regulatory Commission Washington, D. C. 20555
Subject:
Illinois Power Response to Request for Additional Information Related to the Generic Letter 96-06 Response for the Clinton Power Station. Unit 1 (TAC No. M96796)
Dear Madam or Sir:
The purpose of this letter is to provide the Illinois Power (IP) response to the request for additional information (RAl) related to the IP response to Generic Letter (GL) 96-06, " Assurance of Equipmer.t Operability and Containment Integrity During
. Design-Basis Accident Conditions," dated January 28,1997 (letter U-602686), as supplemented by letter U-602785 dated July 24,1997.
The IP response to the subject RAI is provided in Attachment 2 to this letter. provides an affidavit supporting the facts set forth in this letter.
Sincerely yours, Lwba 6:.)hn V
(
Walter G. MacFarland IV I
Senior Vice President and ChiefNuclear Officer 1
bU A mlh Attachments cc:
NRC Clinton Licensing Project Manager NRC Resident Office, V-690 Regional Administrator, Region III, USNRC i_
Illinois Department of Nuclear Safety 9906220130 980615 il e
PDR ADOCK 05000461 4 p
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Walter G. MacFarland, IV, being first duly sworn, deposes and says: That he is Senior Vice President and Chief Nuclear Officer at Illinois Power; that this letter supplying information for Generic Letter 96-06 has been prepared under his supervision and direction; that he knows the contents thereof; and that to the best of his knowleige and belief said letter and the facts contained therein are true and correct.
Date: This IS' _ day ofJune 1998.
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i Signed:
Vk Walter G. Ma'cFarland, IV 1
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l STATE OFILLINOIS l SS.
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Subscribed and sworn to before me this /f' day ofJune 1998.
maxi c3 b (Notary [ublic)
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Page 1 of 4 The requested information from the NRC RAI relative to the IP response to GL l
96-06, along with IP's responses are provided below.
1.
If a methodology other than that discussed in NUREG/CR-5220," Diagnosis of Condensation-Induced Water llammer," was used in evaluating the elT2 cts l
of water hammer, describe this alternative methodology in detail. Also, explain why this methodology is applicable and gives conservative results for the Clinton unit (typically accomplished through rigorous plant-specific modeling, testing, and analysis).
IP Response As stated in letter U-602686 dated January 28,1997, Clinton Power Station (CPS) does not rely on flow to any coolers to mitigate the consequences of the design basis accident (i.e., LOCA). However, as also stated in letter U-602686, operation of the Drywell (VP) and Supplemental Drywell (WO) cooling systems is possible post LOCA as allowed in CPS Emergency Operating Procedure (EOP) 4402.01, "EOP-6 Primary Containment Control." These systems were evaluated, at representative worst case locations, for potential catastrophic damage due to water hammer using simplified methods. Since VP or WO chiller performance is not required or assumed for design basis accident mitigation, the affect of a water I
hammer event on containment integrity was of primary concern in the evaluation.
The IP evaluation did not assume initiation of Drywell cooling concurrent with the initiation of a LOCA event. It was assumed that since neither the VP nor WO system would be initiated until post-LOCA, vapor could be formed in these systems and collect at system high points. The associated pressure rise at these locations was calculated based on a variation of the classical water hammer equation provided by " Hydraulics of Pipelines," by J. Paul Tullis, copyright 1989, Wiley Interscience. No credit was taken for air and other gases in the fluid which would decrease wave speed. The resulting pressure wave was assumed to travel through the system from the point of vapor collapse without credit for reduction in amplitude due to friction. The affects of changes in flow area (positive and negative) and the affects of branching were considered. The resulting forces were determined at critical locations (near containment penetrations) based on the conservative head rise discussed above and the pipe area. Simplified calculations were done to determine the resulting pipe stresses in these locations. Credit for shape factor or extended allowable was not taken. The resulting calculated stresses were well below allowables (ASME,Section III, level D).
IP Calculation No. IP-M-0435 is provided as Attachment 3. This calculation provides the methodology for the evaluation.
2.
For both the water hammer and two-phase flow analyses, provide the following information:
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Page 2 of 4 1
a.
Identify any computer codes that were used in the water hammer and two-phase flow analyses and describe the methods used to bench mark the codes for the specific loading conditions involved (see Standard Review Plan Section 3.9.1).
IP Response:
No computer codes were used to perform the analysis.
I b.
Describe and justify all assumptions and input parameters (including those used in any computer codes) such as amplifications due to fluid structure interaction, cushioning, speed of sound, force reductions, and mesh sizes, and explain why the values selected give conservative results. Also, provide justification for omitting any effects that may be relevant to the analysis (e. g., fluid structure interaction, flow induced vibration, erosion).
IP Response:
l Assumptions, input parameters, and conservative assumptions are provided in the response to question # 1 above.
c.
Provide a detailed description of the " worst case" scenarios for water hammer and two-phase flow, taking into consideration the complete l
range of event possibilities, time of system alignment, system I
configurations, and parameters. For example, all water hammer types and water slug scenarios should be considered, as well as temperatures, pressures, flow rates, load combinations, and potential component failures. Additional examples include:
the effects of void fraction on flow balance and heat transfer; e
the consequences of steam formation, transport, and e
accumulation; cavitation, resonance, and fatigue efTects; and e
erosion considerations.
e Licensees may find NUREG/CR-6031," Cavitation Guide for Control Valves," helpfulin addressing some aspects of the two-phase flow analyses.
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The " worst case" water hammer scenario is the vapor bubble collapse induced water hammer described in the IP response to question #1 above. Since CPS does not rely on flow to any coolers to mitigate the consequences of the design bases accident, and due to the simplified conservative nature of the IP analysis, rigorous analysis of other noted factors was not performed.
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d.
Confirm that the analyses included a complete failure modes and effects analysis (FMEA) for all components (including electrical and pneumatic failures) that could impact performance of the cooling water system, and confirm that the FMEA is documented and available for review, or explain why a complete and fully documented I
FMEA was not performed.
l IP Response:
Due to the simplified nature of the evaluations a complete and fully documented FMEA was not performed. As discussed in letter U-606686, non-safety systems allowed to be utilized in EOPs are not designated to safety related criteria.
Analysis shows that in the unlikely event that a waterhammer were to occur due to the post-LOCA use of the VP or WO systems, the ability to provide containment isolation and integrity would be maintained. Therefore, the worst possible result would be the inability for WO and VP to perform drywell cooling functions. No credit is taken for these systems to provide drywell cooling during design bases events. Therefore, they do not provide a design basis safety function.
Explain and justify all uses of" engineering judgment."
e.
IP Response:
All uses and the justification for " engineering judgment" are provided in Calculation IP-M-0435 provided as Attachment 3 to this letter.
3.
Determine the uncertainty in the weter hammer and two-phase flow analyses, explain how the uncertainty was determined, and how it was accounted for in the analyses to assure conservative results for the Clinton Power Station.
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Based on the approach discussed in the IP response to question # 1 above, uncertainty analysis was not performed.
4.
Confirm the water hammer and two-phase flow loading conditions do not exceed any design specifications or recommended service conditions for the piping system and components, including those stated by equipment vendors; and confirm that the system integrity will be maintained.
IP Response:
As discussed above in the IP response to question 2.d, non-safety systems allowed to be utilized in EOPs are not designed to safety related criteria. VP and WO system functional integrity is not a concern since credit is not taken for these systems to provide drywell cooling during design bases events. Simplified analysis approaches were used as discussed above.
5.
Provide a simplified diagram of the system, showing major components, active components, relative elevations, lengths of piping runs, and the location of any orifices and flow restrictions.
IP Response:
Piping Analytical and Physical Data drawings for the VP and WO systems are provided in Attachment 4 to this letter.
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