ML17164A763
| ML17164A763 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 08/20/1998 |
| From: | Nerses V NRC (Affiliation Not Assigned) |
| To: | Byram R PENNSYLVANIA POWER & LIGHT CO. |
| References | |
| GL-96-06, GL-96-6, TAC-M96875, TAC-M96876, NUDOCS 9808260216 | |
| Download: ML17164A763 (7) | |
Text
August 20, 1998 Mr. Robert G. Byram Senior Vice President-Generation and Chief Nuclear Officer Pennsylvania Power and Light Company 2 North Ninth Street Allentown, PA 18101
SUBJECT:
REQUEST FOR ADDITIONALINFORMATION(RAI) REGARDING RESPONSE TO GENERIC LETTER (GL) 96-06 FOR THE SUSQUEHANNA STEAM ELECTRIC STATION, UNITS 1 AND2 (TAC NOS. M96875 AND M96876)
References:
Letters from Pennsylvania Power 8 Light Company to NRC regarding the Susquehanna Steam Electric Station, Units 1 and 2, response to Generic Letter (GL) 96-06 dated January 29, 1997, May 9, 1997, and June 30, 1997
Dear Mr. Byram:
The NRC staff has reviewed the referenced submittals by the Pennsylvania Power 8 Light Company regarding GL 96-06, "Assurance of Equipment Operability and Containment Integrity During Design Basis Accident Conditions." Your January 29, 1997, submittal, addressed issues related to water hammer, two-phase flow and thermally-induced pressurization of piping runs penetrating the containment at the Susquehanna Steam Electric Station.
You provided additional information regarding these issues on May 9, 1997.
In a June 30, 1997, submittal, you provided a plan to resolve the issue of thermally-induced pressurization of piping runs penetrating the containment.
The NRC staff has been reviewing your submittals, however, we have determined that additional information is required to complete our review.
In order to complete its evaluation of your responses to the generic letter, the NRC requests that you provide a response to the enclosed RAI by October 30, 1998.
Ifyou have any questions regarding this request, please contact me at (301) 415-1484.
9808260216
'9i80820 PDR ADOCK 05000387 PDR Ll Docket Nos. 50-387 and 50-388 Sincerely, original signed by D.Brinkman for Victor Nerses, Senior Project Manager Project Directorate I-2 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
Enclosure:
RAI cc w/encl: See next page S
U 0 Docket File PUBLIC PDI-2 Reading JZwolinski RCa ra VNerses MO'Brien SMalur OGC ACRS JTatum LMarsh CAnderson, RGN-I OFFICE PDI-2/PM NAME SMaiurrb DATE t /2~/98 PDI-2/PM VNerses 2/m/98 PDj;2/i
(.8 MO> rien f98 PDI-2/D RCa ra 8 /a /98 OFFICIAL RECORD COPY DOCUMENT NAME: SU96875.RAI
Mr. Robert G. Byram Pennsylvania Power 8 Light Company Susquehanna Steam Electric Station, Units 1 &2 CC:
Jay Silberg, Esq.
Shaw, Pittman, Potts 8 Trowbridge 2300 N Street N.W.
'ashington, D.C. 20037 Bryan A. Snapp, Esq.
Assistant Corporate Counsel Pennsylvania Power 8 Light Company 2 North Ninth Street Allentown, Pennsylvania 18101 k
Licensing Group Supervisor Pennsylvania Power 8 Light Company.
2 North Ninth Street Allentown, Pennsylvania 18I01 Senior Resident Inspector U. S. Nuclear Regulatory Commission P.O. Box 35 Berwick, Pennsylvania 18603-0035 Director-Bureau of Radiation Protection Pennsylvania Department of Environmental Resources P. O. Box 8469 Harrisburg, Pennsylvania 17105-8469 Mr. Jesse C. Tilton, III Allegheny Elec. Cooperative, Inc.
212 Locust Street P.O. Box 1266 Harrisburg, Pennsylvania 17108-1266 Regional Administrator, Region I
U.S. Nuclear Regulatory Commission 475 Allendaie Road King of Prussia, Pennsylvania 19406 General Manager Susquehanna Steam Electric Station Pennsylvania Power and Light Company Box 467 Berwick, Pennsylvania 18603 Mr. Herbert D. Woodeshick Special Office of the President Pennsylvania Power and Light Company Rural Route 1, Box 1797 Benuick, Pennsylvania 18603 George T. Jones Vice President-Nuclear Operations Pennsylvania Power and Light Company 2 North Ninth Street Allentown, Pennsylvania 18101 Dr. Judith Johnsrud National Energy Committee Sierra Club 433 Orlando Avenue State College, PA 16803 Board of Supervisors Salem Township P.O. Box 405 Berwick, PA 18603
U 96-06 ISS 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 licensee's 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 at Susquehanna Steam Electric Station (SSES), Units 1 and 2, in letters dated January 29 and May 9, 1997. Your response indicated that the drywell cooling system at SSES is non-safety related and automatically isolates on a loss-of-coolant accident (LOCA). However, the Emergency Operating Procedures at SSES allow the operators to use the drywell coolers following a LOCA, ifthey are available.
0 In the May 9, 1997, submittal, twelve containment penetrations at each unit that are susceptible to thermally-induced pressurization were identified.
In the June 30, 1997, submittal, you indicated that you are pursuing two options for resolving the issue of thermally-induced overpressure for these systems.
One option involves ongoing engineering efforts to evaluate the susceptible containment penetrations.
The other option involves participation in ongoing American Society of Mechanical Engineers'ode initiatives on this issue.
In order to complete our review of the your resolution of these issues, the following additional information is requested:
Note: 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 4 may not be fullyapplicable.
1.
Provide a complete and detailed description of the "worst case" scenarios for both waterhammer and two-phase flow that could occur in the cooling water systems that provide cooling for the drywell coolers within the constraints imposed by the licensing basis of the plant, taking into consideration the complete range of event possibilities, parameters, 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, and potential component failures. Additional two-phase flow considerations include:
~
the consequences of steam formation, transport, and accumulation;
~
cavitation, resonance, and fatigue effects; and
~
erosion considerations.
It is important to realize that in addition to heat transfer considerations, two-phase flow also involves structural and system integrity concerns that must be addressed.
You may find NUREG/CR-6031, "Cavitation Guide for Control Valves," helpful in addressing some aspects of the two-phase flow analyses.
ENCLOSURE
2.
Ifa 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 (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) such as ampliflications 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, thermal inertia of the piping system, 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 was accounted 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 willremain operable.
5.
Describe positive measures that have been taken (or willbe taken) to eliminate the potential for waterhammer and two-phase flow conditions, such as placing restrictions on head tank parameters or on use of the drywell cooling system following an accident.
With these controls in place, describe the worst-case scenarios and how much margin to boiling will exist.
6.
Implementing measures to assure that waterhammer willnot occur, such as restricting post-accident operation of the affected system and placing restrictions on head tank level, is an acceptable approach for addressing the waterhammer and two-phase flowconcerns.
However, all scenarios must be considered to assure that the vulnerability to waterhammer has been adequately addressed.
Confirm that all scenarios have been considered such'that the measures that have been established are adequate to address all applicable situations.
7.
Discuss specific system parameters and operating restrictions that must be maintained in order for the waterhammer and two-phase flowanalyses 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 use of any non-safety-related instrumentation and controls for maintaining these parameters and operating restrictions.
8.
Confirm that a complete failure modes and effects analysis (FMEA) was completed for all components (including electrical and pneumatic failures) that could impact performance of the affected cooling water systems and confirm that the FMEA is documented and available for review, or explain why a complete and fullydocumented FMEAwas not performed.
9.
Explain and justify all uses of "engineering judgement."
10.
Provide a simplified diagram of the affected systems, showing major components, active components, relative elevations, lengths of piping runs, and the location of any oriflices 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.
12.
For those penetrations that are susceptible to thermally-induced overpressure and were found to be acceptable by engineering evaluation, provide the following information:
- a. The applicable design criteria for the piping and the valves, including the'required load combinations
- b. A drawing of the piping run between the isolation valves, including the lengths and thicknesses of the piping segments and the type and thickness of the insulation
- c. The maximum-calculated temperature and pressure for the pipe run. Describe, in detail, the method used to calculate these pressure and temperature values.
This should include a discussion of the heat transfer model used in the analysis and the basis for the heat transfer coefficients used in the analysis.
13.
For those penetrations that are susceptible to thermally-induced overpressure and were
'ound acceptable based on leakage through the isolation valves, provide the following information:
- a. A description of the applicable design criteria for the piping and valves, including the required load combinations
- b. A drawing of the valve. Provide the pressure at which the valve was determined to liftoff its seat or leak and describe the method used to estimate this pressure.
Discuss any sources of uncertainty associated with the estimated liftoff,or leakage pressure
- c. The calculated maximum stress in the piping run based on the estimated liftoffor leakage pressure.
- 14. The non-safety-related drywell floor sump system discharge piping is a closed-loop system inside the containment and was identified as susceptible to thermally-induced pressurization.
You indicated that the system is protected from overpressure because the check valves will leak, and that such leakage is confirmed by the operational history. Provide additional information regarding the leakage of these valves including the method of measuring the leakage and the quantity of the leakage measured.
Also provide a comparison of the measured leakage with the leakage necessary to prevent overpressurization of the piping.
I'i
~
~
I