ML17309A637
| ML17309A637 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 07/21/1998 |
| From: | Mecredy R ROCHESTER GAS & ELECTRIC CORP. |
| To: | Vissing G NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-06, GL-96-6, TAC-M96814, NUDOCS 9807290262 | |
| Download: ML17309A637 (17) | |
Text
CATEGORY 1 REGULAT i INFORMATION DISTRIBUTIO YSTEM (RIDS)
I
'ACCESSION NBR:9807290262 DOC.DATE: 98/07/21 NOTARIZED: YES DOCKET FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G 05000244 AUTH.NAME MECREDY,R.C.
'UTHOR AFFILIATION Rochester Gas 5 Electric Corp.
RECIP.NAME RECIPIENT AFFILIATION VISSING, G. S.
SUBJECT:
Forwards addi info re response to GL 96-06,as requested in 980414 ltr. C DISTRIBUTION CODE: A072D COPIES RECEIVED:LTR ENCL SIZE:
TITLE: GL 96-06, "Assurance of Equip Oprblty & Contain.Integ. during Design T
05000244 E
RECIPIENT COPXES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL NRR/WETZEL,B. 1 1 PD1-1 PD 1 1 0 VISSING, G. 1 1 INTERN : FILE CE 1 1 NRR/DE/EMEB 1 1 R/DSSA SCSB 1 1 NRR/DSSA/SPLB 1 1 EXTERNAL: NOAC 1 1 NRC PDR 1 1 D
U N
NOTE TO ALL "RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD) ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED: LTTR 9 ENCL 9
.1 I
ROCHESTER GAS AND ELECTRIC CORPORATION 89EASTAVENUE, ROCHESTER, NY. 14649-0001 AREA COOE 716-546-2700 ROBERT C. MECREDY Vice President Nvdear Operations July 21, 1998 U.S. Nuclear Regulatory Commission Document Control Desk Attn: Guy S. Vissing Project Directorate I-l Washington, D.C. 20555
Subject:
Response to Request for Additional Information (RAI) Related to Generic Letter 96-06 (TAC No.
M96814)
R. E. Ginna Nuclear Power Plant Docket No. 50-244 Ref. (1): Letter from Guy S. Vissing (NRC) to Robert C. Mecredy (RG&E),
SUBJECT:
REQUEST FOR ADDITIONALINFORMATION RELATED TO GENERIC LETTER 96-06 RESPONSE FOR R. E. GINNA NUCLEAR POWER PLANT (TAC NO. M96814), dated April 14, 1998
Dear Mr. Vissing:
By Reference 1, the NRC staff requested additional information regarding the Response to Generic Letter 96-06 for the R. E. Ginna Nuclear Power Plant. The attachment to this letter provides the requested information.
Very y yours, Robert C. Mecredy Attachment Subscribed and sworn to before me on this 21st day of July, 1998 C'.
Public u'otary MARIE C. VII.I.ENEUVE YoiR Notary Public, State of New Monroe County Commission Exltires October 31, 19m
'st8072'st0262 'st8072i PDR ADQCK 05000244 P PDR
~ ~
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xc: Mr. Guy S. Vissing (Mail Stop 1482)
Project Directorate I-l Division of Reactor Projects I/II Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 U.S. NRC Ginna Senior Resident Inspector
RESPONSE TO NRC REQUEST FOR ADDITIONALINFORMATION (RAI)
FOR RESOLUTION OF GENERIC LETTER 96-06 ISSUES AT THE R. E. GINNA NUCLEAR POWER PLANT I. Ifa methodology other than (or in addition to) that discussed in NUREGICR-5220,
, "Diagnosis of Condensation-Induced Waterhammer", was used in evaluating the effects of waterhainmer, describe this alternate methodology in detaiL Also, explain why this methodology is applicable and gives conservative results for the Ginna plant (typically acco>nplished through rigorous plant-speci Jt c modeling, testing, and analysis).
Response
Rochester Gas and Electric Corporation's (RG&E's) analyses which were the bases of original response to GL 96-06 evaluated that severe waterhammer has a very low probability of occuring at the SW water piping upstream and downstream of the Containment Recirculation Fan Coolers (CRFC's) due to the presence of heated water that acts as a buffer between cold water sections and steam that formed at the CRFC's during fan coastdown. The analyses also considered a very conservative situation that when waterhammer does occur at CRFC tubes and SW piping, using predictive methods similar to NUREG/CR-5220, the structural integrity of the SW pressure boundary will not fail in the hoop direction which has the dominant stress field.
Furthermore, RG&E's preliminary evaluation of effects of the fluid/structure interaction of the efects of a traveling pressure pulse associated with a steam void collapse downstream of the CRFCs has indicated that the SW piping will be protected from loss of structural integrity by the existing seismic pipe supports in the SW piping.- This evaluation utilized more realistic values for the acoustic parameters than those presented in NUREG/CR-5220. Specifically, the acoustic velocity used in Equation 5.5 of NUREG/CR-5220 to calculate the pressure pulse from a steam void collapse was obtained from NUREG/CR-6519, "Screening Reactor Steam/Water Piping Systems for Water Hammer". Additionally, the water slug velocity used in Equation 5.5 was based upon the maximum SW volumetric flow associated with the operation of two SW pumps following a LOOP condition.
As soon as project scope and cost are finalized by EPRI, RG&E will make a final decision to participate in a combined Industry/NEI/EPRI Collaborative Project to develop a technical basis document to address waterhammer issues of GL 96-06, delineated in a June 5, 1998 letter (Reference 1) from Mr. David J. Modeen (NEI) to Mr. Ledyard B. Marsh (NRC). RG&E plans to refine the waterhammer analysis of the CRFC/SW system in a time frame consistent with the completion of this collaborative project.
RAI Response GL'96-06 2 'age
- 2. For both the waterhanuner and two-phase flow analyses, provide the following information:
- a. Identify any computer codes that were used in the waterhammer and two-phase flo 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).
Response
During analyses of two-phase flow issues, RG&E has utilized the results of a computer code, KYPIPE, "Computer Analysis of Flow in Pipe Networks Including Extended Period Simulations", Rev. 2.13 which was developed by Dr. D. J. Wood, Department of Civil Engineering, University of Kentucky.
This code has been verified and tested per RG&E Procedure QE330 (Reference 3).
During tests of the newly installed CRFCs A, B, C, &D in 1993, KYPIPE was utilized to check flow distributions for one and two service water (SW) pump operations (Reference 4). Good agreement between test and analytical results were obtained. Although KYPIPE models liquid systems, additional two-phase flow resistances were input to calculate the flow reductions with flashing.
No other computer codes have been used in the analyses of those effects.
j
- b. Describe and ustify all assumptions and input parameters (including those <<sed in any computer codes) such as amplification due to fluid structure interaction, cushioning, speed of sound, force reductions, and mesh sizes, and explain why the values selected give conservative results. Also, providej ustiflcation for omitting any effects that may be relevant to the analysis (e.g., fluid structure interaction, flow induced vibration, erosion). While the January 30, submittal was not expected to be complete in this regard, examples of information that is contained in the January 30, submittal that has not been adequately justified include:
. assumption that the containment recirculation fan coolers (CRFCs) will coast down over a period of 30 seconds;
RAI Response GL'96-06 3 'age
Response
The CRFC fan coastdown time was obtained based upon actual coastdown testing of the Ginna fans at ambient conditions to quantify the fan/motor inertial resistance.
This inertial resistance was then used in a computer model to calculate the fan/motor coastdown under accident conditions. The computer model was verified by comparing model predictions for fan start-up under ambient and Integrated Leak Rate Test (ILRT) conditions to actual fan start-up test data taken during these conditions. It should be noted that the ILRT test conditions closely match the expected post accident conditions. The computer model closely matched this data.
The computer model predicted a fan coastdown of 22 seconds. RG&E choosed to use 30 seconds in the analyses for conservatism.
applicability and validity of EPRI interim and draft reports (references 3.7 and 3.8 of the January 30, submittal;
Response
The conclusions of the EPRI reports referenced in RG&E's January 30, 1997 submittal have been supported by evaluations performed by RG&E of the CRFC steam boiling and steam growth transient using Ginna specific conditions. The RG&E evaluations concluded that appreciable boiling of steam in the CRFCs would occur following a LOOP condition. Additionally, consistent with the EPRI reports, the RG&E evaluations concluded that the resulting steam void would migrate to the SW inlet and outlet piping. Due to the U bend configuration of the Ginna SW inlet and outlet piping described in the January 30, 1997 submittal, the steam growth would cause significant heating of the water contained in the SW piping similar to that described by the EPRI reports.
other sections of the CRFCs will resist the effects of waterhammer peak pressure;
Response
As stated in RG&E's January 30, 1997 submittal, the non-tube sections of the new CRFCs were manufactured with enhanced structural capabilities. The CRFC design of the plenum boxes includes the use of pass ribs and spacers which are held together by multiple bolts that can absorb a substantial amount of strain energy.
This in combination with the attenuation due to plenum entrance/exit affects of waterhammer pressure pulses generated in the CRFC tubes or SW piping has been evaluated to be sufficient to maintain the structural functionality of the plenum boxes.
RAI Response GL'96-06 Page 4 the amount of steam formed and extent of the steaIn envelope that is formed within the service water piping (i.e., where is the steamlwater interface and what is the basis for water temperature assumptions); and
Response
Preliminary evaluations of the extent of the steam bubble formed due to the SW pump and CRFC fan coastdown and start-up transients following a LOOP, have determined that the steam envelope on the discharge side of the CRFC could extend into the 8" and 14" SW piping in the Intermediate Building. Consequently, for the preliminary fluid/structural interactions discussed in response to Question 1, RGkE evaluated the expected pressure pulse from a void collapse in both the 8" and 14" SW discharge piping. Since the water slug in the SW discharge piping being driven by the start-up of the SW Pump has been heated by the CRFCs, the actual temperature of the water slug does not affect the pressure pulse generated by the collapse of the steam void. The water slug velocity is controlled by the volumetric flow of the SW pumps which are pushing the water slug through the SW piping and collapsing the steam void generated due to boiling in the CRFCs prior to the restart of the SW Pumps. Consequently, the preliminary evaluation of the fluid/structural interaction discussed in Question 1 are based upon a water slug velocity in the CRFC piping due to the start-up of two SW Pumps following a LOOP.
water te)nperature assumption used for evaluation of waterhammer in the service water system discharge piping.
Response
To minimize the time to boiling in the CRFCs and to maximize the volume'of the steam void created by boiling in the CRFCs, all of the RG&E evaluations have been performed with a maximum SW inlet temperature of 85'F. Since any steam void collapse is expected to be limited by the velocity of the water slug being driven by the operating SW Pumps, the SW temperature is expected to have little effect on the pressure pulse generated by a steam void collapse.
RAI Response GL'6-06 Page 5
- c. Provide a detailed description of the "worst case" scenarios for waterhaminer and two-phase flow, taking into consideration the complete range of event possibilities, system configurations, and para>neters. 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. Additional examples include:
the effects of void fraction on flow balance and heat transfer; the consequences of steam forInation, transport, and accumulation; cavitation, resonance, and fatigue effects; and erosion considerations.
Licensees may flnd NUREGiCR-6031, "Cavitation Guide'or Control Valves, "
helpful in addressing some aspects of the two-phase flow analyses
Response
c.1: Items related to waterhammer issues in the above RAI will be deferred until after development of the waterhammer technical basis document (References 1, 2).
Items related to two-phase flow are provided below.
c.2: Two-Phase Flow Issues The CRFC system for Ginna consists of four CRFC units, each unit includes the motor fan, cooling coils, moisture separators, high efficiency particulate air filter, duct distribution system, and instrumentation and control. During the post accident period two of the CRFC units are required for depressurization of the Containment (Reference 5). The cooling water requirements of the four CRFC units are supplied by a service water (SW) system which provides a heat sink for removal of heat during normal or accident conditions. The SW system consists of a single loop header supplied by two separate, 100% capacity, safety related pump trains (see Attachment 1 Schematic). Each train is powered from a separate Class 1E electrical bus and consists of two 100% capacity pumps and associated check and isolation valves. Due to redundancy considerations, the SW system is designed such that one SW pump can supply the cooling water requirements of the four CRFC units during design basis transients/accidents. Each of the two emergency diesels powers a SW pump which automatically starts as part of the emergency
RAI Response GL'96-06 Page 6 bus-loading sequence on loss of normal ac power coincident with a requirement for engineered safety features operation (SI signal).
During post accident condition, each of the four CRFC units will provide a minimum heat removal capacity of 54.6 MBtu/hr with Containment condition of 74.7 psia and 286 F (Ref. 5). We also note that only two of the CRFC units are required for depressurization of the Containment during post accident conditions.
RGB'as evaluated the following "worst case" scenarios as bounding cases for consideration of two-phase flow effects in the CRFC/SW systems.
Scenario No. 1:
Consideration of one 100% capacity SW pump, two available CRFC units, SW inlet water temperature of 85 F, and a design fouling factor of 0.001 hr-sq ft-oF/Btu (Reference 5). The maximum fouling limits heat transfer capacity at the CRFC units, while the maximum inlet SW temperature optimizes temperature distribution at the SW piping making two-phase formation a high possibility during a one SW pump mode of operation.
Scenario No. 2:
Consideration of one 100% capacity SW pump, two available CRFC units, SW inlet temperature of 85 F, and completely clean tubes, (i.e., fouling factor of 0.000 hr-sq ft- F/Btu). Clean tubes and a SW inlet temperature of 85 F optimizes the temperature field at the SW piping, making two-phase flow'formation a high possibility especially at outlet piping downstream of the CRFCs, for a one SW pump operation.
Scenario No. 3:
Consideration of one 100% capacity SW pump, four CRFC units, SW inlet temperature of 85 F, and completely clean tubes (i.e., fouling factor of 0.000 hr-sq ft- F/Btu). This scenario provides more flow paths for the SW flow distribution system, and consequently minimizes the SW pressure field at the inlet and outlet piping of the CRFC units. Clean tubes and the maximum SW temperature optimizes the temperature field at the SW system, especially at the CRFC outlet piping, making two-phase flow formation a high possibility during a one pump operation.
RAI Response GL'96-06 7 'age Evaluation of these "worst case" scenarios are documented in References 6, 7, and
- 8. In cases where two-phase flow can form, RGB'nvestigated the effects of void fraction on flow balance and heat transfer considering the consequence of steam formation, transport, and accumulation of two-phase inventory. Utilizing Reference 9, RG8cE also evaluated the effects of two-phase flow field in the erosion, cavitation, resonance, and fatigue of the piping pressure boundary. These effects are negligible since there is no violent collapse of the two-phase flow and the duration is short term.
Results of the evaluation are summarize below.
- 1. For scenarios 1, 2 Ec 3 two-phase flow will not form at the CRFC coils.
- 2. For scenarios 1, 2 and 3, two phase flow can occur at the SW discharge piping downstream of the CRFCs and outside of Containment. Effects of this condition on flow balance and heat transfer were further investigated and found that each CRFC can still provide the minimum heat removal capacity (References 6, 7, 8) to perform its design-basis function as required in the accident analysis for Ginna (Reference 13).
- d. Confirm that the 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 system and conPrm that the FMEA is documented and available for review, or explain why a complete and fully documented FMEA was not performed.
Response
The analyses that were undertaken by RG&E to respond to the original GL 96-06 requirements and the current RAI took into consideration results of FMEA analysis (Reference 11) and the single active failure analysis of the Ginna Service Water system (Reference 10). These analyses are well documented and are available for review.
RAI Response GL'6-06 8 'age
- e. Explain and justify all uses of "engineering judgment".
Response
To limit the extent of the analyses needed to be performed for assessing the consequences of two-phase flow in the SW discharge piping on CRFC heat removal capability, RGAE used engineering judgement to establish bounding cases that would be analyzed. For example, the heat removal capability of the CRFC was analyzed for the two bounding CRFC fouling conditions of no fouling (clean CRFCs) and design fouling. These results are expected to envelope the results obtained for any other fouling condition. Consequently, based upon this engineering judgement, detailed two-phase flow analyses were only performed for these two cases. Enginering judgement was also used to identify conservative two-phase frictional resistances for SW System piping and components. Additionally, based upon engineering judgement it was decided that minimum lake level elevation and maximum lake temperature would provide conservative results for the overall CRFC heat removal capability in the two-phase flow analyses that were performed.
Engineering judgement was also used within the two-phase flow design analyses for modeling of those components and parameters that are not expected have a significant impact on the final two-phase flow results.
- 3. Determine the uncertainty in the water hammer and two-phase flow analyses, explain how the uncertainty was determined, and how it was accounted for in the analyses to assure conservative results for the Ginna plant.
Response
RG8~E addressed uncertainties in the two-phase flow analyses by using conservative inputs and assumptions as described below or by performing sensitivity studies when it was not certain of the conservative nature of an input or assumption. For example, during the determination of "worst case" scenarios for investigating effects of two-phase flow, the following conservative cases were considered:
- a. Two and four CRFC unit operations were studied separately.
- b. Service water inlet temperature of 85 F was used, although the maximum system design temperature is 80 F (Reference 5).
- c. Only one of four SW pumps is considered available.
- d. Consideration of bounding cases of completely clean and completely fouled tubes per design requirements.
Confirm that the water hammer and two-phase flow loading'conditions do not exceed any design specifications or recommended servi ce conditions for the piping system and components, including those stated by equipment vendors; and confiI7n that the system will continue to perform its design-basis functions as assumed in the safety analysis report for the faciltity.
Response
Utilizing the assumptions as described in the response to question 1, RG&E evaluated the impact of waterhammer and two-phase flow on the piping system, components and supports. Structural integrity of the SW system pressure boundary (piping, components, and supports) will be maintained. RG&E will perform more detailed analyses of the potential waterhammer effects based upon the results of future EPRI research efforts as described in question 1 response.
In the evaluation of "worst case" scenarios for effects of two-phase flow, it was confirmed that minimum heat transfer capacity of each CRFC unit is still maintained at 54.6 MBtu/hr. Consequently, the CRFC and SW systems will continue to perform its design basis function as considered in Ginna accident analysis (Reference 13).
- 5. Provide a simpltJied diagram of the system, showing major components, active components, relative elevations, length ofpiping runs, and the location of any ortJi ces and flow restrictions.
Response
Simplified diagrams of Ginna CRFC/SW systems showing those items requested in the RAI are attached.
Attachment 1: Schematic Diagram Showing SW System Supply Trains to CRFC's.
Attachment 2: Simplified Piping Layout Showing SW Paths To and From CRFC's.
RAI Response GL'6-06'age 10 RKliX<RKNCE
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