ML20236M705
| ML20236M705 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/02/1998 |
| From: | Hernan R NRC (Affiliation Not Assigned) |
| To: | Scalice J TENNESSEE VALLEY AUTHORITY |
| References | |
| GL-96-06, GL-96-6, TAC-M96866, TAC-M96867, NUDOCS 9807140220 | |
| Download: ML20236M705 (5) | |
Text
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Mr. J. A. Scalice July 2, 1998
' Chtf Nucle:r Officer end Executiva Vice Pr:sident Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION ON RESPONSE TO GENERIC LETTER 96-06 FOR SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 (TAC NOS. M96866 AND M96867)
Dear Mr. Scalice:
The U.S. Nuclear Regulatory Commission staff has reviewed the submittal by Tennessee Valley Authority (TVA) dated January 28,1997, regarding Generic Letter 96-06,
" Assurance of Equipment Operability and Containment Integrity During Design Basis Accident l
Conditions." TVA's submittal addresses the issues of waterhammer, two-phase flow and l
thermally induced pressurization of piping runs penetrating the containment. Our letter to you of May 27,1998, addressed the thermally induced pressurization of piping runs penetrating the containment. The enclosure to this letter identifies additional information that we are requesting in order to continue our review of the waterhammer and two-phase flow issues for the Sequoyah Nuclear Plant, Units 1 and 2. We are requesting that TVA provide this h1 formation by August 30,1998, in order to support the staff's review schedule.
Sincerely, Original signed by onaW. Heman,' SeNomoject Manager P
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PDR Project Directorate 11-3 yU Division of Reactor Projects - 1/ll Office of Nuclear Reactor Regulation Docket Nos. 50-327 and 50-328 l
Enclosure:
Request for Additional Information cc w/enct See next page t
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Docket File - OGC.
BClayton LPlisco, Rll JZwolinski RHernan '
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OFFICIAL RECORD COPY DOCUMENT NAME: G:tSQN\\96866.RAI
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at REQUEST FOR ADDITIONAL INFORMATION FOR RESOLUTION OF GL 96-06 ISSUES AT SEQUOYAH 1 AND 2 (TAC NOS. M96866 AND M96867)
Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions," dated September 30,1996, included a request for licensees to evaluate cooling water systems that serve containment air coolers to assure that they are not vulnerable to waterhammer and two-phase flow conditions. Tennessee Valley Authority (the licensee) provided its assessment of the waterhammer and two-phase flow issues for Sequoyah 1 and 2 in a letter dated January 28,1997. The licensee's response indicated that the essential raw cooling water (ERCW) system, which provides cooling water to the lower compartment coolers (LCCs) and upper compartment coolers (UCCs), is essentially isolated post-accident. However, ERCW is aligned to the LCCs for long-term cooling following a main steam line break (MSLB). The licensee's assessment appeared to be very qualitative and in order to assess the licensee's resolution of these issues, the following additional information is requested:
. Notes: a. The following questions are applicable to ERCW cooling associated with the '
LCCs and UCCs.
- b. To the extent that positive measures are implemented to eliminate the potential for waterhammer and two-phase flow conditions, question numbers 1,2,3, and l
4 may not be fully applicable.
1 i
1.
Provide a complete and detailed description of the " worst case" scenarios for both waterhammer and two-phase flow that could occur in the ERCW system within the constraints imposed by the licensing basis of the plant, taking into consloeration the complete range of event possibilities, pararnotars, and system configurations (including situations where containment isolation has not occurred, if this is a possibility). For example, all waterhammer types and water slug scenarios should be considered, as well as temperatures, pressures, flow rates, load combinations, availability of off-site power, l
and potential component failures. Additional two-phase flow considerations include:
the effects of two-phase flow on heat t(ani,.er, the consequences of steam formation, transport, and accumulation; e
cavitation, resonance, and fatigue effects; and erosion considerations.
it is important for licensees to realize that in addition to heat transfer considerations, L
two-phase flow also involves structural and system integrity concems that must be l.
' addressed. Licensees may find NUREG/CR-6031 " Cavitation Guide for Control Valves," helpful in addressing some aspects of the two-phase flow analyses.
y.
ENCLOSURE 9
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- 4, 2
l Notes: a. The licensee's response indicated that containment temperature will i
decrease to less than 120' F before ERCW is initiated following a MSLB.
. The licensee's response did not describe the effects of steam that might have formed earlier into the event.
- b. The licensee's response did not recognize the potential for column separation and rejoining.
c,. The licensee's response did not address loss-of-power scenarios.
- d. The licensee's response indicated that a stuck open relief valve in the ERCW system was considered to be the single active failure. All potential failures must be considered such that the worst-case scenario is recognized and addressed.
2.
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 attemate methodology in detail. Also, explain why this methodology is applicable and gives conservauve results (typically accomplished through rigorous plant-specific modeling, testing, and analysis).
3.
For both the waterhammer and two-phase flow analyses, provide the following information:
- a. Identify any computer codes that were used in the waterhammer 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),
- b. Describe and justify all assumptions and input parameters (including those used in any computer codes) rJch 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),
- c. Determine the uncertainty in the waterhammer and two-phase flow analyses, explain how the uncertainty was determined, and how it wre e u.ed for in the analyses to assure conservative results.
4.
Confirm that the waterhammer 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 will continue to perform its design-basis functions as assumed in the safety analysis report for the facility and that the containment isolation valves will remain operable.
e.
e-3 5.
Describe positive measures that have been taken (or will be taken) to eliminate the potential for waterhammer and two-phase flow conditions in the ERCW system, such as placing restrictions on use of the ERCW system following an accident. Describe the worst-case scenarios and how much margin to boiling will exist.
6.
Implementing measures to assure that waterhammer will not occur, such as restricting post-accident operation of the affected system or maintaining head tank pressure, is an acceptable approach for addressing the waterhammer and two-phase flow concems.
However, all scenarios must be considered to assure that the vulnerability to waterhammer has been adequately addressed. Cot?irm that all scenarios have been considered such that the measures that have oeen established are adequate to address
- all situations.
7.
Discuss specific system operating parameters that must be maintained in order for the waterhammer and two-phase flow analyses to be valid (e.g., head tank pressure, temperature, and level), and explain why it would not be appropriate to establish Technical Specification requirements for these system parameters. Also, describe and justify reliance on any non-safety related instrumentation and controls in this regard.
8.
Confirm that a complete failure modes and effects analysis (FMEA) was completed for al; components (including electrical and pneumatic failures) that could impact performance of the ccc!ing water system and confirm that the FMEA is documented and available for review, or explain why a complete and fully documented FMEA was not performed.
9.
Explain cnd justify all uses of " engineering judgemant."
- 10.
Provide a simplified diagram of the affe::ted systems, showing major components, active components, relative elevations, lengths of piping runs, and the location of any orifices and flow restrictions.
11.
Describe in detail any plant modifications or procedure changes that have been made or are planned to be made to resolve the waterhammer and two-phase flow issues,
. Including schedules for completing these actions.
Mr. J. A. Scalice SEQUOYAH NUCLEAR PLANT Tennessee Valley Authority cc:
Senior Vice President Mr. Pedro Salas, Manager Nuclear Operations Tennessee Valley Authority ~
Licensing and Industry Affairs Sequoyah Nucicar Plant 6A Lookout Place Tennessee Valley Authority 1101 Market Street P.O. Box 2000 Chattanooga, TN 37402-2801 Soddy Daisy, TN 37379 j
Mr. Jack A. Bailey Mr. J. T. Herron, Plant Manager I
Vice Presider.i Sequoyah Nuclear Plant Engineering & Technical Services Tennessee Valley Authority Tennessee Valley Authority P.O. Box 2000 6A Lookout Place Soddy Daisy, TN 37379 1
1101 Market Street
.1 Chattanooga, TN 37402-2801 Regional Administrator I
U.S. Nuclear Regulatory Commission
' Mr. Masoud Bajestani Region ll Site Vice President 61 Forsyth Street, SW.
Sequoyah Nuclear Plant Suite 23T85-Tennessee Valley Authority Atlanta, GA 30303-3415 P.O. Box 2000 '
Soddy Daisy, TN 37379 Mr. Melvin C. Shannon Senior Recident inspector General Counsel Sequoyah Nuclear Plant Tennessee Valley Authority U.S. Nuclcar Regulatory Commission ET 10H 2600 Igou Ferry Road 400 West Summit Hill Drive Soddy Daisy, TN 37379 Knoxville, TN 37902 Mr. Michael H. Mobley, Director l
Mr. Raul R. Baron, General Manager TN Dept. of Environment & Conservation NuclearAssurance Division of Radiological Health l
Tennessee Valley' Authority 3rd Floor, L and C Annex SM Lookout Place 401 Church Street 1101 Market Street Nashville, TN 37243-1532 Chattanooga, TN 37402-2801 County Executive Mr. Mark J. Burzynski, Manager Hamilton County Courthouse Nuclear Licensing _
Chattanooga, TN 37402-2801 Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801 O