ML20236J041
| ML20236J041 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 06/30/1998 |
| From: | Swailes J NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-06, GL-96-6, NLS980093, NUDOCS 9807080017 | |
| Download: ML20236J041 (7) | |
Text
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P.O. BOX B E EB SKA 68321 Nebraska Public Power District "r!%==""
,_m-NLS980093 June 30,1998 l
U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:
Subject:
Response to NRC Generic Letter 96-06 Cooper Nuclear Station, NRC Docket 50-298, DPR-46
Reference:
- 1. NRC Generic Letter 96-06 dated September 30,1996," Assurance of Equipment Operability and Containment Integrity during Design-Basis Accident Conditions"
" Response to NRC Generic Letter 96-06"
- 3. NRC Letter, dated April 24,1998," Request for Additional Information Related to NRC Generic Letter 96-06, " Assurance of Equipment Operability and Containment Integrity during Design-Basis Accident Conditions" This submittal provides the Nebraska Public Power District (District's) response to the request for additional information (Reference 3) on the District's response (Reference 2) to potential vulnerabilities of the Reactor Equipment Cooling (REC) system, as it serves the containment air coolers, to waterhammer and two-phase flow effects (Reference 1).
In Reference 2 the District stated that the Cooper Nuclear Station (CNS) containment air cooler cooling water system (REC) is not susceptible to either waterhammer or two-phase flow conditions during postulated accident conditions. This conclusion was based on the design of the REC system, coupled with the worst case containment time-temperature profile calculated for a design basis Loss-of-Coolant-Accident (LOCA), which precludes the onset of boiling within these coolers and thus eliminates the possibility of waterhammer and two-phase flow.
Throughout this LOCA event, these coolers will remain pressurized by the REC system's I
clevated surge tank, which increases the boiling point of the cooling water. Although the peak
\\'l containment accident temperature is about 10 F above this boiling point, this difference diminishes to zero after about 17 seconds as the peak containment temperature decreases. Since p
this is a short-term transient, a conservative calculation was performed by the District (NEDC Qo' 97-13) to determine if enough heat could be transferred into the coolers, during this short time
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NLS980093 June 30,19'98 Page 2 of 4 period, such that boiling could occur. The results of this calculation, which are contained in, determined that boiling would not occur. The temperature rise of the containment air cooler IEC cooling water was determined via an in-house developed and validated computer program, which was based upon the forward, fm' ite temperature difference methodology. The surface coefficients were also constantly recalculated to provide more accurate modeling.
The District's evaluation also considered the potential for the onset of boiling within the cooler's interconnecting piping using the same methodology utilized by NEDC 97-13. The results of this evaluation indicated that the coolers were the limiting components even though the peak temperature difference and the transient duration are greater in the interconnecting piping. This was documented as an assumption in NEDC 97-13, since the same computer code was used in this calculation.
Condensation-induced waterhammer and two-phase flow in the containment air coolers are not expected to occur since the calculated maximum water temperature in the REC system remains below the boiling point throughout the event. Thus, the additional information requested in items 1-4 is not applicable for CNS since an analysis for waterhanuner and two-phase flow was not required to be performed. A simplified diagram of the system, showing the major components, relative elevations, length of piping runs, and the location of any orifices as requested by item five is shown in Attachment 2.
A recent NRC Inspection Team raised the issue of REC leakage in a post LOCA condition. The REC leakage criteria presently established as a result of this question ensures that the above analysis remains valid.
Should you have any questions concerning this matter, please contact me.
Sincerely, p
.V1. Nwai s Vice 're dent f Nuclear Power
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Attachments cc: Regional Administrator USNRC - R.egion IV Senior Project Manager l
NLS980093 Jund 30,19'98 Page 3 of 4 USNRC - NRR Project Directorate IV-1 Senior Resident Inspector USNRC NPG Distribution i
NLS980093 June 30,19'9'8 Page 4 of 4 STATE OF NEBRASKA -
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l J,11. Swailes, being first duly sworn, deposes and says that he is an authorized representative of L
the Nebraska Public Power District, a public corporation and political subdivision of the State of Nebraska; that he is duly authorized to submit this correspondence on behalf of Nebraska Public Power District; and that the statements contained herein are true to the best of his knowledge and belief.-
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Subs ibed in my s :nce and sworn to before me this 30 day of Juc-
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ATTACHMENT 3 LIST OF NRC COMMITMENTS l
Corrpspor}d,ence No: NLS980093 The following table identifies those actions committed to by the District in this document. Any other actions discussed in the submittal represent intended or planned actions by the District.
They are described to the NRC for the NRC's l information and are not regulatory commitments.
Please notify the NL&S Manager at l
Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITTED DATE COMMITMENT OR OUTAGE l
NONE j
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l PROCEDURE NUMBER 0.42 l
REVISION NUMBER 6 l
PAGE 9 OF 13 l
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