ML18153C767
| ML18153C767 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 10/02/1991 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 89-572G, GL-89-13, NUDOCS 9110080264 | |
| Download: ML18153C767 (14) | |
Text
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VIRGINIA ELECTRIC AND PowER COMPANY RICHMOND, VIRGINIA 23261 October 2, 1991 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 Serial No.
NURPC Docket Nos.
License Nos.
CONSOUDATED RESPONSE TO GENERIC LETTER 89~13 SERVICE WATER SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT 89-572G R3 50-280 50-281 DPR-32 DPR-37 Generic Letter 89-13 required actions to address various problems with service water systems which have, in the past, led to system degradation or failure. Virginia Electric and Power Company letter (Serial No.89-572) dated January 29, 1990, described the program that would be implemented to ensure that the service water (SW) system at Surry Power Station will be in compliance with appropriate regulations, specifications, and licensing basis documentation. This response was supplemented for Surry by letters (Serial Nos. 89-572B, D, and F) dated January 18, 1991, March 28, 1991, and July 8, 1991, respectively, and letter (Serial No.91-087) dated March 14, 1991.
In our letter (Serial No. 89-572E) dated April 30, 1991, we committed to provide a comprehensive revision of our initial January 29, 1990 response incorporating subsequent supplements and additions. Our initial response, as it applies to Surry, and the associated revisions for each requirement are provided in Attachment 1.
Although this revision contains no new commitments nor modifies previously specified ones, this response supercedes our previous correspondence on Generic Letter 89-
- 13. Should you have further questions, please contact us.
Very truly yours, r* r"""",
1 ul\\-*-: ~-'
ML) 'Qv-;T' W. L. Stewart Senior Vice President - Nuclear Attachment
- 1. Generic Letter 89-13 Activities - Revision of Initial Response
cc:
U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station e
COMMONWEAL TH OF VIRGINIA )
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COUNTY OF HENRICO
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The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by W. L. Stewart who is Senior Vice President - Nuclear, of Virginia Electric and Power Company.
He is duly authorized to execute and file the foregoing document in behalf of that Company, and the statements in the document are true to the best of his knowledge and belief.
Acknowledged before me this.J...S:!.. day of ({}{!igk,,J, 19:l.L.
My Commission Expires: ~
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Notary Public (SEAL)
e ATTACHMENT i GENERIC LETTER 89-13 ACTIVITIES REVISION OF INITIAL RESPONSE
RESPONSE TO GENERIC LETTER 89-13:
SERVICE WATER PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT I.
For open-cycle service water systems, implement and maintain an ongoing program of surveillance and control techniques to significantly reduce the incidence of flow blockage problems as a result of biofouling.
A program acceptable to the NRC is described in "Recommended Program to Resolve Generic Issue 51" (Enclosure 1) [to Generic Letter 89-13].
It should be noted that is provided as guidance for an acceptable program.
An equally effective program to preclude biofouling would also be acceptable.
Initial activities should be completed before plant startup following the first refueling outage beginning 9 months or more after the date of this letter.
All activities should be documented and relevant documentation should be retained in appropriate plant records.
Initial Response:
Generic Letter 89-13 recommends a surveillance and control program to reduce the effects of biofouling. The recommended program is comprised of four actions, which include:
A.
Visual inspection, once per refueling cycle, of the intake structure for macroscopic biological fouling organisms, sediment, and corrosion.
B.
Chemical treatment of the service water system with chlorine or another biocide, whenever the potential for macroscopic biological fouling exists.
C.
Periodic flushing and flow testing of infrequently used cooling loops to ensure that they are not fouled or clogged.
D.
Annual sampling of water and substrate to determine if Asiatic clams have populated the water source.
We have evaluated the above four recommended actions. Visual inspection of the intake structures at our nuclear stations will be performed as part of our routine inspection and maintenance program discussed in our response to item Ill.
... At Surry Power Station, a chemical treatment system for biofouling is being considered.
However, the issues associated with chemical treatment for Surry's service water discharge into the James River are complex due to environmental considerations.
As such, we expect to have an evaluation concerning chemical treatment completed prior to the end of the next Surry refueling outage. We will report the results of our evaluation and our intended actions with respect to chemical treatment in our next submittal for Surry Power Station, following the next refueling outage...
Surry Power Station has one portion of the service water system which is not normally operating. This section is the service water supply and return to [discharge for] the Page 1 of 10
recirculation spray heat exchangers (RSHXs). The supply and return to the RSHXs are normally closed; and the RSHXs are maintained in a dry layup condition, resulting in a wetted stagnant pipe section up to the inlet valves on the supply and downstream of the outlet valves on the return. The remaining portion between the inlet and outlet valves is maintained in dry layup. It is undesirable to flow test this loop and wet the heat exchangers. As an alternative, the RSHX inlet and outlet service water lines will be inspected to ensure that they are not unacceptably fouled. In addition, the service water lines associated with the control room air conditioning chiller condensers will also be periodically inspected. While these lines are normally in use, they have a low flow rate and a history of biofouling. Periodic inspection and subsequent cleaning is therefore appropriate. Necessary procedure changes and initial inspections will be completed prior to restart following the next refueling outage for each Surry unit.
... [Annual] Sampling [of the service water supply for asiatic clams] at Surry is not required because the service water supply is brackish.
SURRY UPDATED RESPONSE:
The Unit 1 High Level Intake Structure was inspected during the 1990 refueling outage. Inspections of the Unit 2 High Level Intake Structure, Screenwells 'A' and 'C,'
were performed during the refueling outage while respective trains were dewatered for SW pipe cleaning and coating. Virginia Institute of Marine Sciences (VIMS) personnel were present for the inspection of the 'C' screenwell. Most of the intake structure surfaces were covered with a dense accumulation of hydroids. The effects of this condition on SW system reliability are being considered as part of the ongoing ecosystem study. Future inspections will be conducted under the station preventive maintenance program.
A diver inspection of the Low Level Intake Structure was performed in January, 1991.
This inspection included verification of the condition of the Emergency Service Water Pump suction bells. No adverse conditions were identified at that time. However, we have experienced significant fouling of the suction bells during the summer months in this and prior years. Monthly periodic tests and future inspections and cleaning will be conducted as continuing corrective actions.
RSHX SW piping is maintained in dry layup from the approximate elevation of 12'-0" in the 36" header to the RSHX discharge isolation valves, 1/2-SW-MOV-105/205A, B, C, and D. The balance of the RSHX SW piping, from the header isolation valves 1/2-SW-MOV-103/203A, B, C, and D to elevation 12'-0" of the 36" header, is maintained in wet layup. This methodology serves to reduce the initial service water inrush velocities, thereby minimizing the potential for hydroid entrainment in the flowstream which was observed during the RSHX SW flow tests described in our letter (Serial No.91-087) dated March 14, 1991. Modifications have been implemented to provide a permanent water source and meet biocide requirements for wet layup of this portion of the service water piping inlet headers. Procedures have been developed and implemented to periodically verify proper wet layup conditions. Recent flow testing of one Unit 2 RSHX SW subsystem and inspection of the non-tested subsytem provided evidence that the wet layup has been effective.
The Unit 1 RSHX SW piping was inspected during the 1990 refueling outage. Unit 2 RSHX SW inlet piping was inspected during the 1991 refueling outage in conjunction Page 2 of 10
with the SW pipe cleaning and coating effort. Inspection of the RSHX SW outlet piping is normally impractical since no isolable boundary exists downstream of the 1 /2-SW-MOV-105/205 valves. Without dewatering the discharge tunnel, inspection of the outlet piping would compromise personnel safety.
Portions of this piping can be inspected by removing the expansion joints downstream of 1/2-SW-MOV-105/205 valves provided access to the interior of the pipe is limited in order to provide adequate egress capability. Because of these considerations, only the RSHX SW outlet piping from just downstream of 2-SW-MOV-205C to the first change in direction was inspected. This inspection was performed while the associated expansion joint was removed to support installation of the temporary flow instrumentation during recent Unit 2 flow testing.
No concerns were identified during this inspection.
Additional outlet piping will be inspected in future outages which call for either discharge tunnel dewatering or expansion joint removal.
Provisions for future inspections of the RSHX SW inlet and outlet piping are addressed in Section Ill below.
The 8" SW lines associated with the Control Room Chiller Condensers were partially inspected during the 1990 Unit 1 refueling outage. Inspection of these lines will be completed in 1991 as they can be taken out of service and inspected non-outage.
Future inspections will be conducted under the station preventive maintenance program.
SW flow to RSHXs 2-RS-E-1 B and C (one subsystem) was verified in a special test procedure. Analysis of test data demonstrated that adequate SW flow is available to support design basis heat removal requirements. Post-test channel head, tube, and tubesheet inspections of the tested subsystem were performed with no significant findings identified.
A chemical treatment evaluation was performed and the results issued on August 6, 1990. Although this study concluded that chemical treatment was a viable option, further evaluation indicated significant operating and maintenance costs.
This consideration, combined with the need to broaden our understanding of the local ecosystem and ensure an effective and prudent long-term biofouling control strategy, prompted further evaluation. A study is currently in process and a project team has been established to evaluate alternatives by integrating local ecosystem peculiarities with available biofouling control strategies. The chemical treatment study is scheduled for completion in June, 1992.
An ecosystem study, conducted jointly by Virginia Electric and Power Company and the Virginia Institute of Marine Sciences (VIMS), has been initiated in support of the chemical treatment study. This study includes the following:
A search and review of technical and scientific literature related to marine organisms indigenous to the James River and Surry Power Station.
A colonization study of the life cycle of predominant fouling species.
An envirpnmental tolerance study of the effects of changes in ecosystem environment on predominant fouling species.
A toxicological study of the effects of biocides and water chemistry on the lifecycle of predominant fouling species.
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e An evaluation of the effectiveness and durability of various protective coating and anti-fouling technologies in retarding biological attachment.
0 An evaluation of the effects of SW system fluid dynamics on fouling attachment and detachment.
Sampling of the SW system was initiated in January, 1991. This sampling monitors temperature, pH, conductivity, dissolved oxygen, ammonia, and salinity. Hydro-Lab instruments have been placed in the intake and discharge canals to provide a level of continuous monitoring.
Sampling results are documented and correlated with borescope inspection results. Sampling data is also periodically transmitted to VIMS for analysis and correlation with ecosystem study activities. Following initiation of interim chemical treatment described below, SW chlorine levels were also monitored at the discharge canal before and during chlorine injection.
Since no chlorine has been detected, monitoring of this parameter has been discontinued.
Project team meetings are held regularly to assess study activities and discuss findings. The ecosystem study is currently scheduled to be completed in April, 1992.
Interim modifications to control hydroid growth in the 'A' and 'C' SW headers were implemented in February, 1991. These modifications involved the addition of valving and fittings to the header manways and fabrication of a portable chemical injection skid. These changes allow periodic injection of sodium hypochlorite (NaOCI) to the stagnant 48" SW headers.
Chlorine injection levels are established to ensure releases are within local, state, and federal discharge limits.
Inspection of the Unit 2 "A" 48" SW header during a September, 1991 forced outage revealed no significant fouling growth, indicating that biofouling control measures have been effective.
II.
Conduct a test program to verify the heat transfer capability of all safety-related heat exchangers cooled by service water.
The total test program should consist of an initial test program and a periodic retest program.
Both the initial test program and the periodic retest program should include heat exchangers connected to or cooled by one or more open-cycle systems as defined above.
... A program acceptable to the NRC for heat exchanger testing is described in "Program for Testing Heat Transfer Capability" (Enclosure 2) [to Generic Letter 89-13]. It should be noted that Enclosure 2 is provided as guidance for an acceptable program.
An equally effective program to ensure satisfaction of the heat removal requirements of the service water system would also be acceptable.
... If similar or equivalent tests have not been performed during the past year, the initial tests should be completed before plant startup following the first refueling outage beginning 9 months or more after the date of this letter....
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Initial Response:
Virginia Electric and Power Company has evaluated the practicality of testing the safety-related heat exchangers cooled by service water.
As a result, we have determined that testing cannot verify the heat transfer capability for most heat exchanger applications. For example, the RSHXs... are maintained in dry layup and would require initiating containment spray to test. Verification of the RSHXs' heat transfer capability is accomplished by assuring that the heat exchangers are maintained in their design basis dry layup condition. Another example includes those heat exchangers which have heat loads which are too small to facilitate meaningful testing. Accordingly, the Company will develop a specific program for each station to verify the heat transfer capability of the safety-related heat exchangers cooled by service water. The programs will take into account design limitations such as above.
These programs, when fully developed, will provide equally effective actions utilizing a combination of performance testing, special testing and design verification analysis, and parametric surveillance with operational requirements and limitations.
Our programs are under development and will be in place prior to restart following the next refueling shutdown on each unit.
... Surry Power Station... [has]... taken certain programmatic steps to ensure the operability of various heat exchangers cooled by service water. The methods currently in use include design analysis, cooler inspections, routine surveillance of operational parameters, periodic flow or other testing, and periodic cleaning. These activities will be reviewed to ensure adequate verification of a heat exchanger's capability to perform its design basis function and integrated into the comprehensive program discussed above.
SURRY UPDATED RESPONSE:
A testing program has been developed to test the heat transfer capability of the CCHXs. Baseline testing (i.e., clean tubes and tubesheet) has been performed on heat exchangers 1-CC-E-1 A, 8, C, and D. An analysis of the test results for 1-CC-E-1 A, 8, and D concludes that these heat exchangers, when clean, performed consistent with design specification heat transfer requirements. The test data for 1-CC-E-1 C is currently being evaluated. Subsequent tests required to establish performance trends (i.e., the effects of fouling on performance) on the CCHXs will be scheduled in 1992.
A testing program has been established for verifying the heat transfer capability of the Control Room Chiller Condensers. Baseline testing has been completed on Chillers 1-VS-E-4A, 8, and C.
Heat transfer testing of the RSHXs is not performed.
The system physical configuration makes heat transfer testing impractical without extensive modifications.
The RSHXs are maintained in dry layup during normal operation in order to preclude the possibility of microfouling. Special testing has been performed which verified adequate SW flow is available to the RSHXs to support post-OBA containment depressurization and long-term containment heat removal. An additional SW flow test is planned for the next Unit 1 refueling outage currently scheduled in early 1992.
Considerable margin exists between the design heat transfer capability of the Charging Pump Lube Oil Coolers and the design heat load. Since available heat load Page 5 of 10
is so low in comparison to cooler capacity, meaningful heat transfer testing is not considered feasible. Performance of these coolers is verified by routine monitoring of the Charging Pump bearing temperatures.
Provisions for inspections and maintenance of the Charging Pump Lube Oil Coolers are addressed in Section Ill below.
The design heat transfer capability of the Charging Pump Intermediate Seal Coolers is greater than that required to remove design heat load. Normal heat loads and design tube side temperature differentials are insufficient to achieve accurate results in heat transfer performance testing.
Seal Cooler maintenance is performed routinely as described below in Section Ill.
The design heat transfer capability of the Emergency Service Water (ESW) Pump Diesel Coolers is greater than that required to remove design heat load. Operating experience has demonstrated that design heat loads could be removed despite significant fouling. Normal heat loads and design tube side temperature differentials are insufficient to achieve accurate results in heat transfer performance testing.
Periodic Tests are performed monthly on the ESW Pumps.
These tests require manipulation of the SW throttle valve to adjust water temperature. Failure to achieve the temperature criteria with the SW throttle valve fully opened prompts a strainer change and cleaning of the previously inservice strainer basket.
Diesel Cooler maintenance is performed routinely as described below in Section Ill.
The design heat transfer capability of the ESW Pump Right Angle Gear Oil Coolers is greater than that required to remove design heat load. Operating experience has demonstrated that design heat loads could be removed despite significant fouling.
Normal heat loads and design tube side temperature differentials are insufficient to achieve accuracy in heat transfer performance testing. Gear Oil Cooler maintenance is performed routinely as described below in Section Ill.
Ill.
Ensure by establishing a routine inspection and maintenance program for open-cycle service water system piping and components that corrosion, erosion, protective coating failure, silting, and biofouling cannot degrade the performance of the safety-related systems supplied by service water.
The maintenance program should have at least the following purposes:
A.
To remove excessive accumulations of biofouling agents, corrosion products, and silt; B.
To repair defective protective coatings and corroded service water system piping and components that could adversely affect performance of their intended safety functions.
This program should be established before plant startup following the first refueling outage beginning 9 months after the date of this letter.
A description of the program and the results of these maintenance inspections should be documented.
All relevant documentation should be retained in appropriate plant records.
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Initial Response:
Various activities exist at... Surry Power Station that constitute elements of an inspection and maintenance program. As noted in our response to item II, various heat exchangers are currently subject to inspection and periodic cleaning. We also will inspect the service water intake structures and those additional pipe sections which provide assurance that infrequently used cooling loops are not significantly fouled. Accordingly, we will review our current activities and organize them into an integrated inspection and maintenance program. Additional areas of inspection will be evaluated on a case by case basis. Our inspection and maintenance program will be developed prior to restart following the next refueling outage for each respective unit.
SURRY UPDATED RESPONSE:
Control Room Chiller surveillance is currently performed three times per week. This procedure verifies chiller performance by monitoring a variety of chiller operating parameters including chiller condenser SW inlet and outlet temperatures and condenser differential pressure.
Corrective action (e.g., condenser cleaning) is initiated when unacceptable operating parameters are identified. Performance data is tracked and trended by the System Engineer.
Routine inspection and maintenance of the Charging Pump Lube Oil Coolers is* not performed. These coolers are relatively small and inexpensive when compared to cleaning costs.
Since effective SW side cleaning is difficult and not considered economical, cooler maintenance is accomplished by replacement. The monitoring of bearing temperatures, described above in Section II, provides early indication of cooler performance degradation and the need for preventive maintenance.
Routine inspection and maintenance of the Charging Pump Intermediate Seal Coolers is not performed. These coolers are relatively small with helical coils. Since effective SW side cleaning is difficult and not considered economical, cooler maintenance is accomplished by replacement.
The monitoring of charging pump operating parameters provides early indication of cooler performance degradation and the need for preventive maintenance.
The ESW Pump Diesel Coolers' system inspection and maintenance include removal, inspection, and cleaning of the cooler core.
Following maintenance, cooler SW temperature is verified to be within acceptable limits by adjusting the SW throttle valve.
ESW Pump Right Angle Gear Oil Coolers maintenance replaces the cooler oil inventory and verifies water flow at the gearbox cooler outlet.
Each CCHX is currently tested weekly to detect performance degradation due to biofouling. Heat exchanger cleaning is performed when conditions reach specified alert levels. Future heat transfer testing, described above in Section II, will be used to verify the adequacy of the analytical model upon which surveillance test alert and operability curves are based. Surveillance testing and/or cleaning frequencies will then be adjusted based on the results.
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~**
Unit 1 RSHX SW pipe was inspected during the 1990 refueling outage and Unit 2 RSHX SW pipe was inspected during the 1991 refueling outage as discussed in Section I. The Unit 2 "A" 48" SW header and the "D" High Level Intake Bay were inspected during a September, 1991 forced outage. Future periodic inspections of the Low Level and High Level Intake Structures, RSHX SW Inlet and Outlet Piping, and CR Chiller SW Supply Piping are being evaluated to define the scope, purpose, inspection requirements, and frequency for performing this inspection. Maintenance will be performed based on the inspection results.
IV.
Confirm that the service water system will perform its intended function in accordance with the licensing basis for the plant.
Reconstitution oi the design basis oi the system is not intended.
This confirmation should include a review of the ability to perform required safety functions in the event of a failure of a single active component.
To ensure that the as-built system is in accordance with appropriate licensing basis documentation, this confirmation should include recent (within the past 2 years) system walkdown inspections.
This confirmation should be completed before plant startup following the first refueling outage beginning 9 months or more after the date of this letter.
Results should be documented and retained in appropriate plant records.
Initial Response:
Virginia Electric and Power Company is currently undertaking an extensive Configuration Management Project. Included in this effort is establishing the design basis for the service water system... The resulting Design Basis Documents and associated references will be reviewed to confirm that the service water system will perform its intended safety function. The above review will also ensure that safety functions of the service water system are not vulnerable to a single failure of an active component.
The Configuration Management Project also includes system walkdowns to verify the as-built system. These walkdowns will be completed for each unit prior to restart following the next refueling outage. However, some of the items identified during the walkdowns may remain open. Any item of safety significance will be resolved prior to restart. As part of the recent operational readiness assurance program, Surry Power Station has performed system walkdown inspections of those portions of the service water system relied upon for performance of emergency operating procedures.
Completion of the design basis documentation and associated reviews and walkdowns prior to restart following the next refueling outage is limited to the open-cycle service water system as defined in Generic Lett~r 89-13.
Associated intermediate systems will be completed over the course of the Configuration Management Project. Under the current schedule, closed-cycle service water systems will be completed by December 15, 1992.
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SURRY UPDATED RESPONSE:
The SW and Recirculation Spray systems' Design Basis Documents (DBDs) have been issued. DBDs for interfacing systems including component cooling and residual heat removal are currently in progress. However, the control room air conditioning DBD is being deferred due to the system upgrade presently under way. A SW system single failure review was completed which concludes that the SW system is not vulnerable to consequences due to to a single failure of any active component. Single failure reviews for interfacing systems will be completed following issuance of the the associated DBDs indicated above.
Physical verification of the Units 1 and 2 SW system were completed during the 1990 Unit 1 and 1991 Unit 2 refueling outages, respectively.
Physical verification of interfacing systems will be completed, as previously stated, by December 15, 1992.
V.
Confirm that maintenance practices, operating and emergency procedures, and training that involves the service water system are adequate to ensure that safety-related equipment cooled by the service water system will function as intended and that operators of this equipment will perform effectively.
This confirmation should include recent (within the past 2 years) reviews of practices, procedures, and training modules.
The intent of this action is to reduce human errors in the operation, repair, and maintenance of the service water system.
This confirmation should be completed before plant startup following the first refueling outage beginning 9 months or more after the date of this letter.
Results should be documented and retained in appropriate plant records.
Initial Response:
As noted in our response to item IV above, Virginia Electric and Power Company is currently involved in a Configuration Management Project.
As the design basis documentation is completed, we intend to review our maintenance, operating, and emergency procedures, and training, to ensure that they are consistent with the design basis.
At Surry Power Station, a review of various maintenance practices and procedures, operating and emergency procedures, and training programs was performed for the open-cycle service water system in response to a Safety System Functional Inspection (SSFI) in 1988. Action items associated with the findings resulting from this review have been completed. In addition, we will review appropriate procedures and training following completion of the design basis documentation as previously discussed.
Completion of the reviews is expected within twelve months following issuance of the design basis documentation. While this completion date extends beyond the next refueling outage, it is justified based on the scope of work necessary to generate the design basis documentation and perform its associated procedure reviews...
In addition to the programs described above,... [Surry is] involved in a procedures upgrade program to review and upgrade the station procedures. This program will provide further assurance of the adequacy of service water procedures. Completion of the procedure upgrade program is planned for 1995.
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SURRY UPDATED RESPONSE:
Reviews of maintenance practices and procedures, operating and emergency procedures, and training are currently being performed for the open cycle SW system.
Additional reviews required by our previous commitments will be completed within one year following issuance of the respective DBDs. Completion of these reviews, with the exception of control room air conditioning, is scheduled for December 15, 1992.
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