ML20236W270
| ML20236W270 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 07/30/1998 |
| From: | Geoffrey Edwards PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-06, GL-96-6, NUDOCS 9808050182 | |
| Download: ML20236W270 (14) | |
Text
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.PECO NUCLEAR ecco e e,ov Comnae, 965 Chesterbrook Boulevard t
l A Unit of PECO Energy Wayne.PA 19087 5691 July 30,1998 I
Docket Nos. 50-352 l
50-353 License Nos. NPF-39 NPF-85 1
l U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 1
l
Subject:
Limerick Generating Station, Units 1 and 2 Response to NRC Request For Additional Information (RAl)
Regarding Generic Letter 96-06
Dear Sir / Madam:
By letter dated May 4,1998 the NRC requested additional information related to l
PECO Energy Company's response to Generic Letter (GL) 96-06 " Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions," for Limerick Generating Station, Units 1 and 2.
Attached to this letter is PECO Energy Company's response to the Limerick j
Generating Station RAl. It should be noted that, although the underlying issues associated with this RAI are largely inapplicable to the Limerick units and thus do not represent a safety concern, the time and resources required to respond to this RAI were significant. This information is being submitted under affirmation, and the required affidavit is enclosed.
If you have any questions regarding this submittal, please contact us.
Very truly yours, w_ k -
t G. D. Edwards
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g Director - Licensing f k l
M i
i Enclosure / Attachment "lUvv3 cc:
H. J. Miller, Administrator, Region I, USNRC A. L. Burritt, USNRC Senior Resident inspector, LGS 9808050182 980730 r
yDR ADOCK 05000352 PDR
I COMMONWEALTH OF PENNSYLVANIA ss i
COUNTY OF CHESTER J. B. Cotton, being first duly sworn, deposes and says: that he is Vice l
President of PECO Energy Company, the Applicant herein; that he has read the enclosed request for additional information regarding Generic Letter 96-06 " Assurance of Equipment Operability and Containment Integrity During Design-Basis Accident Conditions," for Limerick Generating Station, Units 1 and 2, Facility Operating License Nos. NPF-39 and NPF-85, and knows the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information, and belief, hdnb U
/
Subscribed and sworn to before me this 8 day l
of July 1998.
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/
/
Notary Public i
NOTARIAL SEAL carol A. WALTON, Notary Publio Qg of Philadelphia. h da. county My Commission Expwess May 28,200t_
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l ATTACHMENT l
LIMERICK GENERATING STATION -
UNITS 1 AND 2 Docket Nos.
l 50-352 50-353 License Nos.
NPF-39 NPF-85 l
Response to RAI l
"PECO Energy Response to the
_ NRC's Request for Additional Information Dated 05/04/98 Regarding Generic Letter 96-06" Response - 11 pages l
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July 30,1998 Dockit Nos. 50-352/353 Attachment Page1
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The following is a complete response to your request for additional information (RAl) dated May 4,1998 regarding our response to Generic Letter 96-06, Assurance of Equipment Operability and ContainmentIntegrity During Design-Basis Accident Conditions," dated February 10,1997 for Limerick Generating Station, Units 1 and 2.
The NRC staff's questions, taken from the LGS RAl, are reprinted for convenience and to facilitate a complete response for LGS.
The following contains a discussion regarding the LGS design as a source of background information (Section 1.) and our response to the staff's questions (Section i
ll.) Please refer to Figure 1 for a simplified diagram of the LGS drywell cooling system.
For more details on system design, please refer to the referenced Updated Final Safety Analysis Report (UFSAR) figures.
L BACKGROUND INFORMATION Design And Operation Of The Drywell Cooling System During Normal Plant Operation 1 The Unit 1 and Unit 2 normal drywell cooling function is provided by the drywell chilled water system (DCWS). This system provides chilled water to the containment coolers via two redundant loops inside containment. Chilled water is supplied through a supply penetration and returned through a return penetration (per loop). There are two containment penetration isolation valves (PCIVs) on each supply penetration and two PCIVs on each return penetration. These motor operated PCIVs automatically isolate on a LOCA signal.
The reactor enclosure cooling water (RECW) system may be used as a backup means of containment cooling should DCWS be unavailable. However, the valves used to align RECW to the drywell unit coolers are closed and administratively controlled such that they are treated as locked closed valves. Normal plant operation with drywell cooling provided by the RECW system is limited by plant Technical Specifications since these valves do not receive an automatic isolation signal. For this reason, use of the RECW system for the drywell cooling function is not addressed regarding GL 96-06.
The DCWS has an elevated head tank connected to the pump suction header and hence the return line from the containment. The head tank is located high above the refueling floor and is vented to the refueling floor atmosphere. A level switch controls makeup water to the tank to maintain level, while a second level switch controls an alarm in the main control room on high or low tank level, indicative of a failure of the tank makeup.
The drywell cooling function of the DCWS is non-safety related and not required for mitigation of any design basis accident. The safety related function of containment cooling is provided by the suppression pool cooling mode of the residual heat removal (RHR) system. Wetwell spray may also be used for safety related containment cooling.
The head tank is non-safety related and non-seismic, and the level switches on the tank are non-safety related.
For more information on the design and operation of the normal containment cooling l
L_____________
July 30,1998 Docket Nos. 50-352/353 Attachment Page 2 systems'of DCWS and RECW, see LGS UFSAR sections 9.2.8 and 9.2.10.1, respectively.
O'pera' ion Of The Drywell Cooling System During'A Design Basis LOCAf t
For boiling water reactor (BWR) plants, there are two concems for waterhammer in the containment cooling lines as identified in GL 96-06. The first concem is an "immediate response waterhammer". For plants that do not isolate their containment cooling lines, and that have the potential for an automatic restart of the drywell cooling water pumps, there may be a potential for a GL 96-06 waterhammer on automatic restart of the drywell cooling water pumps. The second concern is a "long-term response waterhammer." Many BWR plant emergency operating procedures (EOPs) permit operators to re-establish drywell cooling during an event. If steam voids have formed in the drywell cooling lines, there may be a potential for a GL 96-06 waterhammer on manual restart of the drywell cooling function. Although not required as part of the design basis for the plant, it is important to show that such action during a design basis event will not aggravate the event and result in consequences beyond the design basis.
The LGS DCWS is non-safety related and not required for mitigation of any design basis accident. The DCWS PCIVs close on receipt of a LOCA signal. Should a loss of off-site power (LOOP) also occur concurrently with the LOCA, the DCWS pumps would stop almost ir;stantaneously, while the containment cooler fans will coast to a stop and the PCIVs will close at a nominal closure time of 40 seconds. Re-establishment of drywell cooling is not required for any postulated design basis LOCA.
Since the LGS design isolates the drywell cooling lines in the event of a LOCA, and there is no potential for automatic restart of the drywell cooling water pumps during this isolation, LGS does not have the potential for the aforementioned "immediate response waterhammer".
Current emergency operating procedures (EOPs) direct operators to maximize drywell cooling if drywell temperature cannot le maintained below 135'F (maximum normal operating temperature). During a design basis LOCA, this EOP step will direct operators to evaluate the availability of DCWS. If determined to be available, operators will re-establish containment cooling with DCWS. Tank level indication is considered necessary for system availability.
Since the LGS EOPs permit re-establishment of drywell cooling during an event, LGS has reviewed its plant design and operating procedures for the aforementioned "long-term response waterhammer". The results of this review are discussed below.
Generic Letter 96-06 Waterhammer Concern.
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As identified above, LGS is not susceptible to the "immediate response waterhammer" and is evaluated for the "long-term response waterhammer".
The containment response to a design basis large break LOCA is discussed in the LGS UFSAR section 6.2. The drywell temperature profile for this event rises from an t______________--------_-----_-----
July 30,1998 Docket Nos. 50-352/353 Attachn ent Page 3 assumed initial drywell temperature of 150*F to a peak drywell temperature of 288'F at 9 seconds, then drops to 275.8'F at 34 seconds and to 208'F at 10 minutes (Reference LGS UFSAR Figures 6.2-4A and 6.2-8A). For the design basis large main steam line break (MSLB), drywell temperature peaks at about 330*F at less than 1 second, then drops to about 275'F at 10 seconds, then drops to approximately 180*F at 200 seconds (Reference LGS UFSAR Figure 6.2-13). Thus the maximum time during which the drywell temperature exceeds 275*F is about 30 seconds. Although a second drywell temperature peak occurs later in tne event due to suppression pool heat-up, drywell temperature never again exceeds 275'F. For these reasons, a drywell temperature of 275*F was conservatively assumed for this evaluation of the potential for steam void formation within the drywell cooling water lines. The saturation pressure at this temperature is approximately 30.7 psig.
it is noted that a design basis small steam line break inside containment may attain a peak drywell temperature of approximately 340*F. This event involves a slow heat-up of the drywell and drywell temperature is not expected to exceed 275'F during the time for PCIV closure.
By design, the elevation of the bottom of the DCWS head tank outside containment is no lower than elevation 393 feet (Actual layout at LGS has the bottom of the tank above elevation 398 feet). Elevation of the drywell cooling penetrations is at 270 feet 8 inches centerline. These penetrations are the high point for the drywell cooling lines inside containment. Assuming a conservatively high temperature of 135'F for the water in the head tank line (density of 61.464 lbm/cu ft), this yields a static head pressure of at least 52 psig at the penetration, well above the saturation pressure for the drywell temperature of 275'F. Thus, the cooling lines are maintained at a pressure which precludes steam formation throughout the isolation of the drywell cooling lines.
Following isolation of the cooling lines, containment temperature may cause pressure in the cooling lines to increase due to heat absorption and thermal pressurization. A thermal relief valve is provided for protection of the containment unit coolers. This valve will maintain pressure in the line below its nominal setpoint of 135 psig. With a setpoint tolerance of 3% and a blowdown of 8% of nominal setpoint of 135 psig, line pressure may be as low as 120 psig. This pressure again precludes steam void formation because the saturation temperature for 120 psig is greater than 350*F, which is above the 340*F maximum containment temperature for any design basis accident.
Therefore, there is no potential at LGS for the "long-term response waterhammer" upon re-opening the system.
Thus, at LGS there is no potential for waterhammer in the drywell cooling lines during a design basis LOCA, either during the isolation of the cooling lines ("immediate response waterhammer") or should the operators re-establish drywell cooling per i
existing EOPs ("long-term response waterhammer").
Generic Letter 96-06 Two-Phase Flow Concern
Use of DCWS for containment cooling during a design basis LOCA is not required as part of the design basis for LGS. However, current EOPs direct operators to maximize w__--___-_
l July 30,1998 Dockst Nos. 50-352/353 i
f Attachment Page 4 j
d'ywell c'ooling if containment temperatures cannot be maintained below 135'F.
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Therefore, although not required as part of the design basis for the plant, it is possible during the mitigation of a design basis LOCA that the DCWS may be used. The NRC concern for plants such as LGS is that such operation does not aggravate the design basis LOCA to yield results that are worse than the licensed design basis analyses.
The concern is that such use of DCWS during a design basis LOCA does not result in loss of the safety related containment isolation function for the DCWS containment penetrations, j
LGS is evaluated below for the GL 96-06 two-phase flow concem by determining a conservative estimate for the coolant temperature at the outlet of the unit cooler. The equation for the heat transfer from the air to the cooling water and the heat absorbed by the cooling water is:
q = c([n c,),n.n(T,, - T, ) = m c,(T, - T,,,)
where q is the heat transferred to the cooling water (and thus the heat absorbed by the
)
cooling water), c is the overall effectiveness of the unit coolers, (mcp),nin is the maximum 1
heat transfer capability for the unit cooler, Tn is the temperature of the hot atmosphere inside containment, T is the temperature of the cold (inlet) water cooling the unit I
cooler, m is the mass flow rate of the cooling water, c is the specific heat capacity for p
the cooling water, Tom is the temperature of the cooling water at the outlet nozzle, and Tin is the temperature of the cooling water at the inlet nozzle. Note that T. and Tin are identical. This expression is true for both the design conditions and the conditions during the LOCA.
The evaluation for coolant exit temperature has been performed assuming either a nitrogen-only containment environment, and then assuming a steam-only containment environment. The evaluation has also been performed assuming the effectiveness of the unit cooler remains the same as the design conditions, then assuming a worst possible effectiveness of 1.0 (a perfect heat exchanger) for the nitrogen environment and less than 1.0 for the steam environment.
Review of the current LGS design for the DCWS concludes that there is no potential for two-phase flow in the containment cooling lines during a design basis event at the LGS plant.
As identified above, the DCWS is considered unavailable and will not be used for containment cooling during a design basis LOCA if level in the DCWS head tank is below the alarm setpoint. This alarm setpoint, including tolerance, is above the I
required bottom of the tank at elevation 393 feet 0 inches. Static head at the containment penetration, which is the high point for the drywell cooling lines inside containment, is therefore maintained at a pressure of at least 52 psig and two-pnase flow is therefore not credible for water temperatures below 299'F. Since the head tank I
is on the return line, flow losses will tend to increase the pressure at the retum
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penetration, and thus increase the boiling temperature.
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July 30,1998 Docket Nos. 50-352/353 Attachment Page 5 The design basis for the DCWS is to maintain the average drywell temperature below 135' during normal plant operation, and for the cooling water to enter the unit coolers at 50*F and exit at 66.4*F.
l The LGS review conservatively assumes containment atmospheric conditions of 340*F and 55 psig, and a cooling water supply temperature of 120*F. Flow rates through the unit cooler are assumed the same as design conditions.
l Results of the analysis for coolant exit temperature are as follows.
l Nitrogen Steam l
Environment Environment Design Effectiveness 283*F 249'F Worst-Case 300*F 252*F Effectiveness l
These results indicate a realistic maximum coolant water temperature of 249'F.
Although analysis for the nitrogen environment and a perfect heat exchanger results in i
an exit temperature of 300*F (slightly in excess of the aforementioned limit of 299*F for steam formation in the cooling lines), this result is extremely conservative and unrealistic. It is only provided to show an absolute worst-case limit.
Thus, the expected drywell coolant water temperature for the worst-case design basis LOCA at LGS is not great enough to generate steam in the cooling lines inside containment and use of DCWS during the event will have no detrimentalimpact on the containment isolation function of the DCWS penetrations. The margin to two-phase flow for LGS is 299 - 249 = 50*F.
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July 30,1998 Docket Nos. 50-352/353 Attachment i
Page 6 Figure 1 - LGS Drywell Cooling System (2 loops)
Ref: UFSAR Figures 9.2-25 & 9.2-27 1
lcom.inm.ni r.n..iion. l li'j 393*0" 2 7o' s-og,.
>:x:
x
\\\\ x x>
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From To DCWS DCWS pump pump discharge au ction 267' 3"
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,3p PSV.I 3: A 15V13:B thiop A6 tioop B) 064* 3" 26I' 5" thatwat Uma Cooler r
intermedime Unit Coolers 24 6'3*
24 3' B' l
1.cwest UmiCswier I
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July 30,1998 Docket Nos. 50-352/353 Attachment Page 7 l
II.
RESPONSE TO NRC's REQUEST FOR ADDITIONAL INFORMATION QUESTION:
- 1. Discuss specific system parameterrequirements that must be maintained to assure i
that waterhammer will not occur (e.g., head tank level, temperature, pressure), and
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state the minimum margin to boiling that exists, including consideration of i
measurement and analytical uncertainties. Describe andJustify reliance on any non-safety related instrumentation and controls for assuring that waterhammer will not occur, and explain whyit would not be appropriate to establish Technical Specification requirements for maintaining these parameters.
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RESPONSE
The evaluation for waterhammer provided above includes no specific system parameter requirements that must be maintained to assure that waterhammer will not occur.
As identified above, the LGS design includes the automatic isolation of the drywell I
cooling lines upon receipt of a LOCA signal. Therefore, there is no potential for the "immediate response waterhammer" During an event, operators may be directed by EOPs to re-establish drywell cooling.
There is, however, no potential for the "long-term response waterhammer" because line pressure in the isolated line is maintained by a relief valve with a nominal setpoint of 135 psig. Minor drift of this setpoint has no impact on the conclusion of the review. Even at l
a line pressure of 120 psig, which allows for a 3 percent setpoint tolerance and an 8 l
percent reset of the valve, the boiling temperature for this pressure is 350*F. This j
provides a minimum margin to boiling of 10*F above the maximum containment temperature expected for any design basis event.
There is no reliance upon any non-safety related instrumentation or controls for assuring that waterhammer will not occur, and no need to establish Technical Specification requirements for maintaining any parameters.
QUESTION:
2.
The GL 96-06 response indicated that for small break loss of coolant accidents, operators will reestablish DCWS using existing emergency operating procedures l
(EOPs) before containment temperatures reach a point where steam generation could occur. Describe in detail the actions required by the EOPs for this situation, operator response and the timing involved, and the minimum margin to boiling that will exist, including consideration ofinherent uncertainties.
l July 30,1998 Docket Nos. 50-352/353
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Attachment l
Pages
RESPONSE
i Current EOPs direct operators to maximize containment cooling if containment temperature cannot be maintained below 135'F. This step directs operators to assess the availability of the DCWS and re-open the drywell cooling PCIVs if DCWS is
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determined to be available. Normal system procedu:es are used to re-establish DCWS flow to the containment unit coolers.
As discussed above, the "long-term response waterhammer" on re-establishment of drywell cooling is not credible at LGS. Relief valves in these lines maintain the L
pressure at the nominal setpoint of 135 psig. Even allowing for a 3 percent tolerance
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on the nominal setpoint and a blowdown of 8 percent of the nominal setpoint, the I
minimum line pressure will be 120 psig. The boiling point for this water will thus be greater than 350*F. This effords a minimum margin to boiling of 10*F from the 340*F maximum temperature in containment for any design basis event. It should also be noted that, if operators do re-establish drywell cooling during a design basis LOCA, they are most likely to do so at drywell temperatures much less than 340*F, and thus the 10*F minimum margin to boiling is very conservative.
QUESTION:
3.
In order to more fully address the two-phase flow concern, provide the following information:
a.
Provide a detailed descn*ption of the " worst case" scenario for two-phase flow, taking into consideration the complete range of event possibilities, system configurations, and parameters. For example, temperatures, pressures, flow rates, load combinations, and potential component l
failures should be considered. Additional examples include:
0 the consequences of steam formation, transport, and
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accumulation; e
cavitation, resonance, and fatigue effects; and 9
0 erosion considerations.
Licensees may find NUREG/CR-6031, " Cavitation Guide for Control Valves,"helpfulin addressing some aspects of the two-phase flow analyses. (Note:it is important forlicensees to realize that in addition to heat transfer considerations, two-phase flow also involves structural and system integrity concems that must be addressed).
RESPONSE
The LGS design basis does not credit the use of DCWS or RECW for containment l
cooling during any design basis LOCA. Operators may, per existing EOPs, re-establish l
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July 30,1998 Docket Nos. 50-352/353 Attachment Page 9 drywell cooling during a design basis LOCA. The LGS design has been reviewed for the potential for two-phase flow in the drywell cooling lines to ensure that use of DCWS during a design basis LOCA will not result in the loss of the containment isolation function of the DCWS penetrations.
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The " worst case" design basis LOCA is a small steam line break where containment temperatures may approach 340*F. Although normal DCWS supply temperature is 50'F, the LGS review for two-phase flow conservatively assumes a supply temperature of 120*F. The analysis also conservatively assumes design (single pump) flow rate, l
and all unit coolers operating. The margin to two-phase flow is 50*F.
I Since the margin to two-phase flow is great at LGS, consideration for the j
consequences of steam formation, transport, accumulation, cavitation, resonance, fatigue effects, and erosion, is not relevant to LGS. As use of DCWS is not required to mitigate the consequences of a design basis LOCA, a failure modes and effects analysis (FMEA) is not considered necessary.
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1 QUESTION:
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I 3b.
Identify any computer codes that were used in the two-phase flow analysis and describe the methods used to benchmark the codes for the specific loading conditions involved (see Standard Review Plan Section
- 3. 9.1).
RESPONSE
i No computer codes were used in the two-phase flow analysis.
QUESTION:
3c.
Descn'be andjustify all assumptions and input parameters (including l
those used in any computer codes), and explain why the values selected give conservative results. Also, providejustification for omitting any effects that may be relevant to the analysis (e.g., flow-induced vibration, erosion).
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RESPONSE
The two-phase flow review assumed 120 F for the DCWS supply temperature. Normal DCWS supply is from the chillers at a temperature of 50*F, therefore this assumption is very conservative. The review also assumes design (single pump) flow rate. A higher flow rate would result in lower exit temperatures and a larger margin to saturation. The review evaluated the potential for steam formation at the high point for cooling lines inside containment (the containment penetration). Since no steam formation is expected at the high point, no steam formation is expected in the unit cooler and l
therefore no decrease in cooling flow rate. Because the analysis indicates a large margin to saturation, no effects of two-phase flow are considered.
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l July 30,1998 Docket Nos. 50-352/353 j
Attachment Page 10 l
OUESTION:
3d.
Detennine the uncertaintyin the two-phase flow analysis, explain how
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the uncertainty was determined, and how it was accounted forin the analysis to assure conservative results.
RESPONSE
Since the use of DCWS during a design basis LOCA is not required as part of the licensing basis, since the analysis for two-phase flow was very conservative, and since the margin to two-phase flow is so great, evaluation of uncertainty is not considered j
necessary, j
QUESTION:
3e.
Confirm that the 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 l
functions as assumedin the safety analysis report for the facility, and l
that the containmentisolations valves willremain operable.
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RESPONSE
J The drywell cooling function of the DCWS is non-safety related and not required for mitigation of any design basis accident. Use of DCWS during a design basis LOCA is not part of the design basis for the system, but is permitted in the EOPs as a contingency. In addition, the LGS r' aw has shown that adequate margin to saturation exists such that two-phal flow conditions in the containtnent cooling lines will not exist for any design basis LOCA. Containment integrity is not challenged by the use of DCWS during a design basis LOCA at LGS as directed by the EOPs.
1 QUESTION:
- 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 system and confirm that the FMEA is documented and available for review, or explain why l
a complete and fully documented FMEA was not performed.
RESPONSE; The LGS design for DCWS includes the automatic isolation of the DCWS cooling lines on rreceipt of a LOCA signal. Use of DCWS during a design basis LOCA is not required as part of the design basis for the plant or the system. An FMEA is not considered necessary and has not been performed for the GL 96-06 concerns for LGS.
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July 30,1998 Docket Nos. 50-352/353 Attachment Page II OUESTiON:
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5.
Explain andjustify all uses of 'engineenngjudgment."
RESPONSE
The only use of " engineering judgment"in the LGS review for GL 96-06 waterhammer
. and two-phase flow concems, is to use a containment temperature of 275'F for evaluation of the potential for GL 96-06 waterhammer. The containment temperature profile for a design basis large break LOCA at LGS exceeds and then drops to 275'F within the first 34 seconds of the event. It is considered not credible (engineering judgment) for the static water in the cooling lines to rise from the normal retum temperature of 66.4*F to greater than 275'F in this time.
Vendor print for the unit coolers indicates a wei coil weight of 1425 lbm for both coils (each DCWS loop services a single coil of each unit cooler). Conservatively assuming only one fan and coil in operation, and that the dry coil weight is as much as 60% of the wet weight, the total mass of water in one coil is estimated at 285 lbs. For this water to heat from 66.4'F to 275'F in 34 seconds requires a heat transfer of 6.29 MBTU/hr.
Steam generation would require even more heat transfer. The design heat removal capacity for all DCWS cooling units is a total of 4.6 MBTU/hr. Therefore, the engineering judgment is well justified.
QUESTION:
6.
Provide a simplified diagram of the affected systems, showing major components, active components, relative elevations, lengths ofpiping runs, and the location of any onfices and flow restnctions.
RESPONSE
See Figure 1 above for a simplified diagram of the affected system at LGS. Lengths of pipe runs are not indicated as the lengths of runs are significant in cases where waterhammer and two-phase flow are not credible.
QUESTION:
7.
Describe in detail any modifications that have been made (or will be made) to system design or operating requirements to resolve the waterhammerand two-phase flow issues.
RESPONSE
._No modifications have been made, nor are any planned to be made, to the system design or operating requirements involving the waterhammer and two-phase flow issues. Review of the LGS design and operating procedures has adequately shown
. that GL 96-06 waterhammer and two-phase flow is not a concern at LGS.
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