ML20199C777
| ML20199C777 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 11/14/1997 |
| From: | Cruse C BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9711200134 | |
| Download: ML20199C777 (9) | |
Text
I C"4ut.t:s 11. CCns:
II:Jtimore Ga and Electric Cenpany Vice President Cahen Cliffs Nuclear Power Plant Nudear Energy 1650 Cahen Chffs Parkwny 1.usby, Mar)tand 20657 410 495-4455 November 14,1997 U. S. Nuclear Regulatory Commission Washington, DC 20555 A'ITENTION:
Document Control Desk SUl! JECT:
Calvert Clifts Nuclear Power Plant Unit No.1; Docket No. 50-317 Response to Request for Additional Information License Amendment RcguestL.Scrvice Water licAt Exchancers Replacement
REFERENCE:
(a)
Letter from hir, C.11. Cruse (DGE) to NRC Document Control Desk, dated hiay 16,1997, License Amendment Request: Service Water lleat Exchangers Replacement fly letter dated hlay 16,1997 (Reference a), Baltimore Gas and Electric Company (IlGE) submitted a license amendment application to the Nuclear Regulatory Commission (NRC) to implement a modification that constitutes an unreviewed safety question as described in 10 CFR 50.59. The modification involves replacing the service water heat exchangers with new plate and frame heat exchangers having increased thermal performance capability. The unreviewed safety question is due to the addition of a straines and control valves, which will introduce a potential for malfunctions of a different type from those previously evaluated in the Updated Final Safety Analysis Report. The purpose of this letter is to provide a written response to the NRC request for additic.nal information presented to BGE during teleconferences to discuss the hiny 16 application, conducted on September 18 and October 31,1997.
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Docum:nt Control Desk November 14.1997 Page 2 Attachment (1) to this letter provides BGE's response. The information contained in Attachment (1) does not change the No Significant liazards Determination presented in Reference (a). Should you have further questions regarding this matter, we will be pleased to discuss them with you.
Veiy truly yours,
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r STATE OF MARYLAF
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COUNTY OF CALVt..
1, Charles 11. Cruse, b.ig duly sworn, state that I am Vice President Nuclear Energy Division, Baltimore Gas and Electric Company (BGE), an( that I am duly authorized to execute and file this License Amendment Request on behalf of BGE. To the best of my knowledge and belief, the statements contained in this document are true and correct. To the extent that these statements are not based on my personal knowledge, they are based upon information provided by other BGE employees and/or consultants. Such information has been reviewed in accordance with company practice and I believe it to be reliable.
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a Notary Public in and fo the State of Maryland and County of r' ed and sworn before n,1 day of M11/l#
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WITNESS my lland and Notarial Seal:
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Attachment:
(1)
Response to NRC Verbal Request for Additional Information Made on September 18 and October 31,1997 cc:
R. f leishman, Esquire
- 11. J. Miller, NRC J. E. Silberg, Esquire Resident inspector, NRC A. W. Dromerick, NRC R.1. McLean, DNR Director, Project Directorate 1-1, NRC J.11. Walter, PSC
ATTACHMENT (1)
BGE RESPONSE TO NRC VERBAL REQUEST FOR ADDITIONAL INFORMATION MADE ON SEPTEMBER 18 AND OCTOBER 31, 1997, REGARDING BGE'S MAY 16, 1997, LICENSE AMENDMENT APPLICATION I
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llaltimore Gas & Electric Company Docket No. 50-317 November 14,1997
MTACllMENT (1)
HGE RESPONSE TO NRC VERHAL REQUEST FOR ADDITIONAL INFORMATION MADE ON SEPTEMHER 18 AND OCTOBER 31, 1997, REGARDING HGE'S MA) 16, 1997 APPLICATION NRC. Ques 11om No, I lias a failure mode and effects analysis been performed for the new service water (SRW) heat exchangers? If so, has it resulted in any unreviewed safety question?
IBGE Response The failure modes and effects of all new components, including the SRW heat exchangers, were evaluated during the design phase of the project. No unreviewed safety questions were identined other than those associated with the strainers and contro! valves that were described in Reference (a).
NRC.Duntion No. 2 On Page 2, Attachment (1), of Reference (a), it is indicated that during a loss of coolant accident (l.OCA) the SRW System design temperature initially increases to ll5'F, and subsequently decreases below 105'F within 35 minutes, if the design temperature of the emergency diesel generator is 105'F, why is 115'F acceptable during a LOCA7 IIGE Response Our existing design basis calculations analyze two extremes for SRW heat exchanger performance during the hitial phase of a 1.OCA. System operating limits and maintenance requirements are based on whichever case is more limiting.
Casel Service water heat exchanger performance is evaluated assuming minimum expected SRW How to the containment air coolers and containment air coolers fouled at their design limit. In this case, the SRW temperature at the outlet of the SRW heat exchanger must be maintained at or below 105'F during all phases of the accident. These assumptions match the assumptions made in the containment analysis and result in the highest containment temperatures and pressures. however, they do not rnaximize the potential heat load placed on the SRW System.
Casel Service water heat exchanger performance is evaluated assumina the maximum expected SRW How to the containment air coolers and clean containment air coolers. These assumptions will maximize the system heat load since the heat duty of the containment air coolers is greater, but will result in lower containment temperatures and pressures, in this case, the SRW heat exchanger must maintain SRW temperature at the outlet s ll5'F during the Orst 35 minutes of the accident, and s 105'F at all other times during the accident. In this case, temperature will only exceed 105'F if the heat removal capacity of the containmer.t air coolers exceeds their capacity in Case 1.
These two cases bound expected system performance during the LOCA and ensure that the containment heat removal capacity will always meet or exceed the value assumed in the containment analysis.
Fairbanks Morse, the diesel generator manufacturer, has evaluated diesel generator performance with cooling water temperatures up to ll5'F returning to s105'F within thirty Ove minutes, and concluded that engine components will not experience any adverse effects, no power loss will b soted, and the temperature transient is acceptable. Both transients, as described above, are part of o existing system design basis, 1
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I AIIAC11MrNT (1)
IIGE RESPONSE TO NitC VEllllAL REQUEST FOR ADDITIONAL INFORh1ATION h1ADE ON SEPTEMilER 18 AND OCTOllER 31,199'i, REGARDING llGE'S MAY 16, 1997, APPLICATION
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'the proposed replacement of the SRW heat exchangers does not change the system design temperatures or the assumptions in the containment analysis. The same cases described above cre included in the new design calculations for the heat exchanger and SRW System thermtl performance.
NRf'.Qucationnoul What maximum design temperature is assumed for the Chesapeake llay water, and what is the corresponding temperature for ths 3RW System?
IlGE Response The new SRW heat exchangers are designed to operate at llay temperatures up to 90'F. With saltwater (SW) inlet temperature at 90 F, either pair of SRW heat exchangers will maintain SRW outlet temperature within its current design limits. These limits are less than or equal to 95'F during normal operations and less than 105'F during accident conditions, except during the first 35 minutes of a I.OCA when temperature may exceed 105'F under conditiens described in response to Question No. 2, but will remain below II5'F. Post LOCA SRW temperature will be less than or equal to 105'F for all accident operating conditions after 35 minutes.
NRC_QucationEoci On Page 3, Attachment (1), of Reference (a), it is stated, "The materials chosen for the new Piles (Titanium for the plates and EPDM for the gaskets) and the method by which the Piles are assembled provide deterrence to the erosion / corrosion problem that has damaged the existing heat exchangers."
Explain how the method by which the plate and frame heat cxchangers (Piles) are assembled provides deterrence to crosion/ corrosion.
IlG E ltesponse Each Pile consists of a fixed cover and a movable cover that are bolted together to compress a stack of titanium plates. The plates and their gaskets form the flow channels. The titanium plates were selected, in part, to minimize erosion effects experienced with the existing shell and tube heat exchangers. He fixed and movable covers (end panels)in the new SRW heat exchangers are made of carbon steel, which is susceptible to corrosion in a SW environment. To protect these panels, the SW nonles are lined with titanium and the SRW nonles are lined with stainless steel. Each end plate, i.e., the titanium plate immediately adjacent to a cover, is gasketed in a manner to prevent 110w of either liquid between the carbon steel plate and the adjoining titanium plate. Therefore, the carbon steel pressure covers are protected from direct contact with the working fluids. This method of Pile assembly is intended to minimize corrosion of the carbon steel components.
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NITACilMENT (1)
HGE RESPONSE TO NRC VEltHAL REQUEST FOR ADDITIONAL INFORMATION MADE ON SEPTEMBER 18 AND OCTOHER 31, 1997, REGARDING HGE'S MAY 16, 1997, APPLICATION i
NRCRuntion No. 5 What - *he bw"". muling factor for the Piles? Is the baseline fouling factor included in the design l
8 bases' calculations in the same manner as the baseline fouling factor for the existing SRW heat exchangers?
IIGE Response
%e total fouling resistance of the existing shell and tube heat exchangers has been divided into two components based on our current heat exchanger testing program. The Hrst component is the baseline fouling, which is the fouling resistance measured in the heat exchanger after the tube side of the heat exchanger has been cleaned. This measured resistance includes shell side fouling, test uncertainty, and any differences between actual heat exchanger perfonnance and that predicted by the empirical heat transfer cc,rrelations used to evaluate it. The measured baseline fouling resistance has been relatively constant and repeatable over the past five years. He second component is the maximum tube side fouling resistance that will build up between heat exchanger cleanings due to growth of a biofilm and some silt accumulation in the biofilm. These two components are added together to establish a total fouling resistance, which is used in the design basis calculations.
2 The plate heat exchangers are designed for a total fouling of 0.0004 ft F hr/Blu. This value is based on industry recommendations for our application, a detailed review of available literature, and the current recommendations by the 11 eat Transfer Research, Inc. for the expected flow conditions.
This total fouling resistance is included in the design basis calculations. Test data is not ava!!sble to break this total fouling resistance into a baseline fouling and a SW side fouling comparable to those used in the shell and tube heat exchanger calculations.
NRCSuntionEam6 What are llGE's plans for post installation and post maintenance testing of the Piles.
HGE Response De PiiEs are included in the post-modification test plans for the Saltwater and SRW Systems.
Speci0cally, the design flow rates to the heat exchangers will be verified in various system line ups, and heat exchanger differential pressure and flow data will be recorded to verify vendor-supplied design information. He heat exchanger high SW difTerential pressure alarm and low SW flow alarms will also be tested.
Ileat exchanger thermal performance testing will not be included in the post modification test since there is insufficient system heat load available in other than hiode 1. The Piles will be incorporated into the heat exchanger test program established in response to C:ncric Letter 8913. Thermal performance is being tested prior to installation through the use of a side stream monitor (SSM).
He SSM consists of a small plate heat exchanger sized to duplicate the Dow characteristics of the actual installation. He hot side of the heat exchanger is supplied by chemically treated, pure water in a closed loop system simulating the conditions in the SRW System. The cold water side is supplied from the plant's SW System. The SSM is instrumented and equipped with a data acquisition system to continuously monitor the heat exchangers thermal performance. The SSM has been in continuous operation since June 1997, and is being used to validate heat exchanger design
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AIIACllMENT (1)
HGE RESPONSE TO NRC VERHAL REQUEST FOR ADDITIONAI INFORMATION hiADE ON SEPTEMBER IN AND OCTOBER 31, 1997, REGARI)ING HGE'S MAY 16, 1997 APPLICATION data, such as the total fouling resistance, and thermal performance calculations, it is expected that the SSM will be part of the long range test program for these heat exchangers after installation.
After initial system acceptance, specific post. maintenance test requirements will have to be reviewed when subsequent maintenance is planned to ensure they are adequate for the activity being performed. in general, it is expected that the post maintenance testing will be limited to a leak check at system operating pressure.
IiAChncationEn.1 What h the impact of minimum now reduction on the system design from 16,830 gpm, for the existing tube and shcIl heat exchanger, to 9000 gpm for two piles? Explain the difference in system now requirements before and after modi 0 cation.
HGE Response ne minimum required SW How to the existing shell and tube SRW heat exchangers is 16,830 ppm.
Normally, SW flow to the new Piles will be controlled at about 4500 gpm, while the minimum required flow in the design basis calculations is 4000 gpm. Minimum required How to the component cooling heat exchangers post recirculation actuation signal,5500 gpm, is unaffected by this modi 0 cation. Likewise, the minimum required now to the Emergency Core Cooling System pump room air coolers, when in operation, is una'Tected.
The required How to the SRW heat exchangers was reduced, based on vendor recommendations, to improve the performance of the heat exchangers and to reduce the pressure drop across the pile to better match existing SW pump operating characteristics, plate and frame heat exchangers operate more efficiently if the hot and cold now rates ase approximately matched. While the minimum required Gow to the SRW heat exchangers was reduced significantly, the total SW How will be maintained near its existing value by use of the SW bypass line. The bypass line will allow total system flow to exceed SRW heat exchanger Dow. In the existing SW System, total SW flow ranges between 15,000 and 20,000 ppm during normal operations. With the use of the bypass line, total system Dow in the modified system is expected to be between 14,000 and 18,000 gpm. This change in total system flow has been evaluated. All components will receive their minimum required now and pump performance will not be adversely afTected by the shift in opercting points.
The minimum pump Dow requirement is 10,000 ppm. The existing system is protected by procedmal requirements to maintain SW hee:ler pressure below 25 psig, in the modified systcm, the setpoint for the pressure control valve in the SW bypass line will be selected to maintain SW pump Cow above the minimum requirement. The control valve in the bypass line will be automatically repositioned to maintain minimum pump Dow during any system configuration changes.
NRCRun11onEum8 On Page 5, Attachment (1), of Reference (a), it is stated that a number of structural modifications will be required to accommodate the replacciaent of the two existing shell and tube heat exchangers with the 4
r ATIACllMENT_II)
HGE RESPONSE TO NRC VERHAL REQUEST FOR ADDITIONAL INFORMATION MADE ON SEPTEMBER IN AND OCTOHER 31, 1997, REGARDING llGE'S MAY 16, 1997, APPLICATION new Piles. Describe the defense in depth measures planned for shutdown safety during the construction activity for these modifications.
HGE Response llaltimore Gas and lilectric has evaluated the replacement activities and determined load handling to be the major activity afTecting shutdown safety. A logic diagram that depicts the sequence of activities for out1ge demolition and installation has been developed. The development of these activities takes into account the requirements of the Calvert Clifts Load llandling Procedure, lead handling instructions will be developed for mose activities meeting this criteria and these instructions will be incorporated into the fic!d w n package. Defining and establishing a safe load path and rigging plan prior to implementation will ensure that shutdown safety concerns relative to load handling are addressed.
Furthermore, Design Instructions are being prepared which will identify actions or criteria to address the operational impact of implementing the modification. These actions or criteria will be addressed in the planning, scheduling, and work packages associated with the modification.
Defense-in depth measures for shutdown safety are addressed in Calvert Clifts procedure NO 1 103, " Conduct of lower Mode Operations" and the consequences of the construction activities for this modification will be addressed to satisfy the requirements of this procedure.
NRC_QucationEnd On Page 7 Attachment (1), of Reference (a), a description of normal opers. tion with one Pile secured is provided. 'lhls option assumes removing one containment air cooler from service to enable the afTected subsystem to remain operable while the one Pile is out of service, llow do you justify this option since such an operation is not allowed by the Calvert Cliffs Technical Specifications?
IIGE Response We are withdrawing this operational option from this application, if, in the future, we decide to incorporate the flexibility of operating with one Pile secured in our operational plan, we will submit a Technical Specification change request with appropriate justification.
SRC_QuestionEud Identify any changes needed to the Technical Specification Suncillance requirements for the new control valves that will be added as part of the heat exchanger replacement.
l IlGE Rest.onse ne new control valves will be covered by Technical Specification Surveillance Requirements 4.0.5," Surveillance Requirements for inservice inspection and testing of ASME Code Class I, 2, and 3 components," and 4.7.5.1, " Saltwater System." Therefore, changes to the Technical Specification Surveillance Requirements are not needed. [ NOTE: Automatic valve position changes are not initiated by the Safety injection Actuation System (Sl AS), hence the new control valves will continue to operate post-SI AS in the same manner as they were operating before the accident.)
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ATTACllMENT f1)
BGE RESPONSE TO NRC VERHAL REQUEST FOR ADDITIONAL INFORMATION MADE ON SEPTEMMER 18 AND OCTOBER 31, 1997, REGARDING BGE'S MAY 16, 1997, APPLICATION HEFERENCE:
(a)
Letter from Mr. C. II. Cruse (BGE) to NRC Document Control Desk, dated May 16,1997, License Amendment Request: Service Water IIcat Exchangers Replacement 6