ML20236G976
| ML20236G976 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 06/30/1998 |
| From: | Terry C, Walker R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-06, GL-96-6, TXX-98164, NUDOCS 9807070034 | |
| Download: ML20236G976 (6) | |
Text
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muminosimums mmmer 9
Log # TXX-98164
""l-File # 10010 Z
C Ref #
10035 7UELECTRIC GL-96-06 c, % %
June 30,1998 Senior %ce President
& PrincipalNuclear Oficer U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION ON GENERIC LETTER 96-06 " ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN BASIS ACCIDENT CONDITIONS" REF:
- 3) NRC Letter from the T. J. Polich, NRR, to C. L. Terry, dated April 6,1998, 1
On October 1,1996, the NRC issued Generic Letter 96-06, " Assurance of Equipment Operability and Containment Integrity during Design Basis Accident Conditions."
TU Electric provided the final response to the NRC request in Reference 1. In that response, TU Electric identified 4 (four) actions to address Generic Letter 96-06. Per Reference 2, the status of the actions and schedule for completion of the remaining actions for the subject Generic Letter were provided. The NRC requested additional information regarding post accident operation of the containment fan coolers in Reference 3. As discussed in Reference 2, TU Electric does not intend to operate the containment fan coolers when there is a possibility of a waterhammer or two phase flow. Per phone conversation with Mr. T. J. Polich and Mr. J. Tatum e f the NRR on April 21,1998, criteria for restarting the fan coolers without risk of twa phase flow and waterhammer may be provided as a response to ' Reference 3 ic !!ca of addressing the l
l specific information requested. Attachment 1 provides our response to the l
information requested in Reference 3.
h if you have any questions regarding the attached information, please contact Mr. J. D. Seawright at (254) 897-0140.
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U 9807070034 980630 l
i PDR ADOCK 05000445 P
PDR-COMANCllE PEAK STEAM ELECT VIC STATION j,h1hk P.O. Box 1002 Glen Rose, Te>, 76043-1002
TXX-98164 Page 2 of 2 This communication contains updated commitments regarding CPSES Units 1 and 2 as identified in Attachment 2.
Sincerely, VV%
C. L. Terry By:
dW4 Rogdf D. Walker Regulatory Affairs Manager JDS/jds -
Attachments c-Mr. E. W. Merschoff, Region IV Mr. 7. J. Polich, NRR Mr. J. l. Tapia, Region IV Resident inspector, CPSES 1
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. to TXX 98164 Page 1 of 2 Question 1:
It is important that the isolation valves for the non-safety related cooling water system remain operable such that the ability for the valves to close and provide a leak tight seal is assured should a waterhammer occur. Provide a detailed description of the
" worst case" scenario that would cause the greatest challenge to these valves, taking into consideration the complete range of event possibilities, system configurations, and parameters. For example, all waterhammer types and water slug scenarios should be considered, as well as temperatures, pressures, flow rates, load combinations, and potential component failures. The following information should also be included:
a.
If a methodology other than that discussed in NUREG/CR-5220," Diagnosis of Condensation-Induced Waterhammer," was used in evaluating the effects of waterhammer, describe this alternate methodology in detail. Also, explain why this methodology is applicable and gives conservative results for the Comanche Peak Units (typically accomplished through rigorous plant-specific modeling, testing, and analysis).
b.
Identify any computer codes that were used in the waterhammer 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).
c.
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).
d.
Confirm that the analyses included a complete failure modes and effects analysis (FMEA) for all components (including electrical and pneumatic failures that could affect the severity of the waterhammer and confirm that the FMEA is documented and available for review, or explain why a complete and fully documented FMEA was not performed, e.
Explain and justify all uses of " engineering judgement." Determine the uncertainty in the waterhammer analysis, explain how the uncertainty was determined, and how it was accounted for in the analysis to assure conservative results.
g.
Confirm ths.t the waterhammer loading conditions do not exceed any design specifications or recommended service conditions for the non-safety related cooling water system isolation valves, including those stated by the valve vendor.
h.
Provide a simplified diagram of the system, showing major components, relative l
elevations, and lengths of piping runs.
. to TXX 98164 Page 2 of 2
Response
a.
No detailed waterhammer analyses have been performed because restoration of ventilation chilled water to the containment fan coolers is not required after an accident and provisions have been made for engineering to evaluate the l
conditions prior to chill water restoration (see below).
I b.
The current emegency operating procedure clearly identifies that high containment temperature conditions can cause flashing /waterhammer to occur l
and chilled water to containment should not be aligned under these conditions.
This provision is adequate to ensure the waterhammer is prevented and containment integrity ensured prior to use of containment fan coolers after an accident. TU Electric will revise the emergency operating procedure to clarify that the plant staff will assess the potential of flashing and waterhammer prior to aligning the ventilation chilled water to containment.
l To enhance the engineering teams response, guidance for assessing the potential for a waterhammer will be developed and will be available for the emergency response team to determine if the potential for a waterhammer exists.
The guidance provided to the emergency response team will ensure that the ventilation chilled water system is evaluated for flashing /waterhammer prior to returning to service after an accident any time the post accident temperature has exceeded 200 F. The guidance for evaluating the potential of the ventilation chilled water system for flashing /waterhammer will consider the bulk temperature of containment to ensure saturation temperature has not been reached for the. ventilation chilled water system, and verifies that the voids do not exist in the system inventory.
l The guidance will contain a summary of the potential waterhammer phenomena and the key physical parameters of the ventilation chilled water system (e.g.,
heat removal capabilities, surge tank elevation and instrumentation, thermal lag time, etc.) and the containment environment (e.g., pressure and temperature transients) which would be required to evaluate the circumstances and ensure a waterhammer does not occur upon restoration.
The guidance will also identify potential waterhammer induced failure modes and effects and pre-planned mitigation c.
Not applicable. See a, above.
d.
Not applicable. See a and b, above.
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e.
Not applicable. See a, above.
j f.
Not applicable. See a, above.
g.
Not applicable. See a, above.
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I to TXX 98164 Page 3 of 2 h.
Flow diagrams for the containment ventilation fan coolers (Figure 9.4-5) and for the venti!ation chilled water system (Figure 9.4-11] are contained in the CPSES FSAR.: low Diagram Volumes for both Unit 1 and Unit 2.
Question 2:
)
Describe assurances that exist that the surge tank leval alarm will be functional and reliable following accident conditions, including a description of environmental conditions, qualification and redundancy of instrumentation and circuitry, etc.
Response
The ventilation chilled water surge tank is located outdoors on the roof of the Fuel Build!ng (El. 919'-9.5"]. Reliable commercial grade instrumentation and alarms are provided. The use of non-safety grade instrumentation is suitable for this application as described below. Due to their location, the relevant environmental conditions post accident would be expected to be similar to normal. The functionality of the surge tank instrumentation would be assessed prior to restoring containment ventilation.
Whenever water level in the surge tank falls below the low level set point, a makeup valve automatically opens to admit demineralized water into the tank. When the tank water level reaches the high level setpoint, the valve will automatically close. In the event containment cooling is restored, the operator can monitor the cycling of this valve to assess and quantify potentialleakage into containment. The surge tank is also provided with a high-high and low-low annunciation level switch for alarm in the Control Room. The low-low alarm would indicate significant leakage exceeding the makeup rate. The operator car also monitor the high-high alarm for significant in-leakage from containment. The surge tank is provided with a liquid level gage for visual inspection of the water level in the event the alarms are not functional.
Additionally, redundant Class 1E accident monitoring instrumentation is provided for containment water level and is covered by CPSES Technical Specification 3/4.3.3.3.
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Attac,hment 2 to TXX 98164 Page 1 of 1 COMMITMENT
[27146]
TU Electric will revise the emergency operating procedure to clarify that the plant staff will assess the potential of flashing and waterhammer prior to aligning the ventilation chilled water to containment.
To enhance the engineering teams response, guidance for assessing the potential for a waterhammer will be developed and will be available for the emergency response team to determine if the potential for a waterhammer exists.
The guidance provided to the emergency response team will ensure that the ventilation chilled water system is evaluated for flashing /waterhammer prior to returning to service after an accident any time the post accident temperature has exceeded 200 F. The guidance for evaluating the potential of the ventilation chilled water system for flashing /waterhammer will consider the bulk temperature of containment to ensure saturation temperature has not been reached for the ventilation chilled water system, and verifies that the voids do not exist in the system inventory.
The guidance will contain a summary of the potential waterhammer phenomena and the key physical parameters of the ventilation chilled water system (e.g., heat removal capabilities, surge tank elevation and instrumentation, etc.) which would be required to evaluate the circumstances and ensure a waterhammer does not occur on restoration.
The guidance will also identify potential waterhammer induced failure modes and effects and pre-planned mitigation l
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