ML20216D696
| ML20216D696 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 04/14/1998 |
| From: | Olshan L NRC (Affiliation Not Assigned) |
| To: | Sumner H SOUTHERN NUCLEAR OPERATING CO. |
| References | |
| GL-96-06, GL-96-6, TAC-M96819, TAC-M96820, NUDOCS 9804150405 | |
| Download: ML20216D696 (6) | |
Text
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Mr. H. LL Sumner, Jr.
April 14, 1998 Vice President'- Nucleir1
+
w Hatch Project Southern Nuclear Operating Company, Inc.
Post Office Box 1295 Birmingham, Alabama 35201-1295~
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE GENERIC LETTER 96-06 RESPONSE FOR HATCH, UNITS 1 AND 2 (TAC NOS, M96819 AND M96820)
Dear Mr. Sumner:
Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment
' integrity During Design-Basis,;f:cident 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. You provided an assessment of the waterhammer and two-phase flow issues for the Hatch units in a letter dated January 27,1997. In order to complete our review of your resolution of these
- issues, we will require additional information as discussed in the enclosure. Please provide this c
.information by June 30,1998, ln' order to support our review schedule for GL 96-06.
Sincerely, ORIGINAL SIGNED BY:
Leonard N. Olshan, Senior Project Manager Project Directorate ll-2 9804150405'900414 Division of Reactor Projects - 1/11 PDR ADOCK 05000321 Office of Nuclear Reactor Regulation P
' Docket Nos. 50-321 and 50-366
Enclosure:
As stated cc w/ encl: See next page; Distribution:
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April 14, 1998 Mr. H. L. Sumner, Jr.
Vice President-Nuclear Hatch Project Southem Nuclear Operating Company, Inc.
Post Office Box 1295 Birmingham, Alabama 35201-1295
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE GENERIC LETTER 96-06 RESPONSE FOR HATCH, UNITS 1 AND 2 (TAC NOS. M96819 AND M96820)
Dear Mr. Sumner:
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. You provided an assessment of the waterhammer and two-phase flow issues for the Hatch units in a letter dated January 27,1997, in order to complete our review of your resolution of these issues, we will require additional information as discussed in the enclosure. Please provide this information by June 30,1998, in order to support our review schedule for GL 96-06.
Sincerely, M
L.
,l flu Leonard N. Olshan, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects - 1/II Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366
Enclosure:
As stated cc w/ encl: See next page j
t c-4 i
Edwin I. Hatch Nuclear Plant
- cc:
Charles A. Patrizia, Esquire Mr. Emest L' Blake, Jr.
Paul, Hastings, Janofsky & Walker Shaw, Pittman, Potts 10th Floor and Trowbridge 1299 Pennsylvania Avenue 2300 N Street, NW.
Washington, DC 20004-9500 Washington, DC 20037 Chairman Mr. D. M. Crowe Appling County Commissioners Manager, Licensing County Courthouse Southem Nuclear Operating Baxley, Georgia 31513 Company, Inc.
P. O. Box 1295 Mr. J. D. Woodard Birmingham, Alabama 35201-1295 Executive Vice President Southem Nuclear Operating
. Resident inspector Company, Inc.
Plant Hatch P. O. Box 1295 11030 Hatch Parkway N.
Birmingham, Alabama 3E201-1295 Baxley, Georgia 31531 Mr. P. W. Wells Regional Administrator, Region ll General Manager, Edwin 1. Hatch U.S. Nuclear Regulatory Commission
' Nuclear Plant Atlanta Federal Center Southem Nuclear Operating 61 Forsyth Street, SW, Suite 23T85 Company, Inc.
Atlanta, Georgia 30303 U.S. Highway 1 North P. O. Box 2010 Mr. Charles H. Badger
. Baxley, Georgia 31515 Office of Planning and Budget Room 610 Mr. R. D. Barker 270 Washington Street, SW.
Program Manager Atlanta, Georgia 30334 Fossil & Nuclear Operations Oglethorpe Power Corporation
- Harold Reheis, Director 2100 East Exchange Place Department of Natural Resources P. O. Box 1349
. 205 Butler Street, SE., Suite 1252 Tucker, Georgia 30085-1349 Atlanta, Georgia 30334 Steven M. Jackson Senior Engineer-Power Supply Municipal Electric Authority
' of Georgia ~
1470 Riveredge Parkway, NW Atlan's, Georgia 30328-4684
REQUEST FOR ADDITIONAL INFORMATION FOR RESOLUTION OF GENERIC LETTER 96-06 ISSUES AT HATCH NUCI FAR PLANT. UNITS 1 AND 2 (TAC NOS. M96319 AND M96820)
Generic Letter 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. Southern Nuclear Operating
. Company (the licensee) provided its assessment of the waterhammer and two-phase flow issues for the Hatch units in a letter dated January 27,1997. The licensee's response indicated that the containment coolers at Hatch are not credited in the accident analysis, but the Emergency Operating Procedures (EOPs) do direct the operators to use the containment area -
coolers for drywell temperature control. Consequently, waterhammer is a valid possibility. The units are different in that Hatch Unit 1 uses plant service water, an open cooling water system, to cool the containment area coolers, while Hatch Unit 2 uses the nonsafety-related chilled water system (a closed cooling water system with a surge tank) for this function. On both units, the Reactor Building Closed Cooling Water (RBCCW) system, a closed loop cooling water system, is used to cool containment equipment coolers. In order to assess the licensee's resolution of the waterhammer and two-phase flow issues, the following additional information is requested:
1.
The event descriptions provided in the January 27,1997, response require some clarification. For example, it is not clear to what extent automatic functions occur such as when the cooling water pumps trip and when the containment /drywell isolation valves for the cooling water systems go closed, and to what extent these functions are automatically restored at some point during the event. Provide a detailed description of the " worst case" scenarios for waterhammer and two-phase flow, which is clear on component status and response, 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 temwatures, pressures, flow rates, load combinations, and potential component fraWes. Additional examples include:
the consequences of column separation and rejoining (not adequately addressed for Hatch Unit 1);
the consequences of steam formation, transport, and accumulation; cavitation, resonance, and fatigue effects; and erosion considerations.
=
The licensee's assessment of the two-phase flow issue only addressed heat transfer considerations, and did not include consideration of the last three items (above).
Licensees may find NUREG/CR-6031, " Cavitation Guide for Control Valves," helpful in addressing some aspects of the two-phase flow analyses.
Enclocure
s
- .. 2.
The licensee's response indicates that because EOPs do not provide for use of the RBCCW system and the containment equipment coolers, this system is not a concem for waterhammer. However, during an accident, operators may consider the RBcew system to still be available as an option for accident mitigation. Discuss measures that exist to assure that operators will not use the RBCCW system as an option during periods when waterhammer and two-phase flow could compromise system integrity.
3.
The waterhammer dW,. ion for Hatch Unit 2 is confusing. The licensee's response indicates that waterhammer could occur in the chilled water system and, because a detailed waterhammer analysis has not been performed, plant procedures were revised l
to prohibit operation of the containment area coolers when containment temperatures j
are above the point where boiling may occur. However, the discussion goes on to say I
that preliminary evaluation shows that the containment boundary provided by the system piping and cooling coils is expected to be maintained following a waterhammer event. Clarification is required as to what positive measures have been taken, including procedure changes and changes to EOPs, to assure that containment integrity will not be compromised as a result of a waterhammer in the chilled water system.
4.
Confirm that the waterhammer and two-phase flow 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 systems and confirm that the FMEA is documented and available for review, or explain why a complete and fully documented FMEA was not performed.
5.
Explain and justify all uses of " engineering judgement" that were used in assessing the waterhammer and two-phase flow issues.
]
6.
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. Explain why this methodology is applicable and gives conservative results for the Hatch units (typically accomplished through rigorous plant-specific modeling, testing, and analysis). Also, provide the following information for each of the Hatch units (as applicable):
a.
Identify any computer codes that were used in the waterhammer and two-phase flow analyses and describe the methods used to benchmark the codes for the specific loading conditions involved (see Standard Review Plan Section 3.9.1).
i b.
Describe and justify all assumptions and input parameters (including those used in any computer codes) such as amplifications due to fluid struc+ure interaction, cushioning, speed of sound, force reductions, and mesh sizes, and explain why 1
the values selected give conservative results. Also, provide justification for omitting any effects that may be relevant to the analyt.is (e.g., fluid structure interaction, flow induced vibration, erosion).
E -.--
l Determine the uncertainty that exists in the waterhammer and two-phase flow c.
analyses, explain how the uncertainty was determined, and how it was accounted for in the analyses to assure conservative results for the Hatch units.
L For those scenarios where waterhammer and two-phase flow could occur
{
(e.g., measures have not been taken to prevent occurrence), confirm that the waterhammer and two-phase flow loading conditions will not exceed any design specifications or recommended service conditions for the piping system and components (e.g., containment /drywell isolation valves), 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.
8.
Provide a simplified diagram of the affected systems, showing major components, active comperients, relative elevations, lengths of piping runs, and the location of any orifices and flow restrictions.
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