ML20247L757
| ML20247L757 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/26/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-004, IEB-88-4, NRCB-88-04, NRCB-88-4, TXX-89251, NUDOCS 8906020247 | |
| Download: ML20247L757 (6) | |
Text
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Log # TXX-85251 1
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File # 10110 C
C 10119
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1UELECTRIC WHHam J. CahHl,Jr.
Executive Vice President U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C.
20555
SUBJECT:
COMANCHE l PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 NRC BdLLETIN 88-04:
POTENTIAL SAFETY-RELATED PUMP LOSS' REF:
1)
TV Electric letter TXX-88556 from W. G. Counsil to NRC dated July 8, 1988 2)
TU Electric letter TXX-88817 from W. G. Counsil to NRC dated November 30, 1988 3)
TU Electric letter TXX-89140 from W. J. Cahill, Jr. to NRC dated March 13, 1988 Gentlemen:.
Reference 1) provided TU Electric's initial response to six action items in the subject NRC Bulletin.
In that letter, TU Electric indicated that the evaluation of the identified safety related systems and pumps for Unit 1 and common would be completed by December 1, 1988.
References 2 and 3 provided the revised schedule for completion of this evaluation and subsequent submittal of the required information.
The enclosed revision of the initial response incorporates the Unit I and common systems evaluation results. Actions planned to resolve potential miniflow concerns are described therein.
Sincerely, William J. Cahill, Jr.
JLR/vid c - Mr. R. D. Martin, Region IV Resident Inspectors CPSES (3) 8906020247 890526 l
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400 North Olive Street LB 81 Dallas, Texas 75?01
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Attachment to TXX-89251'-
'May'26, 1989-Page 1 of-1 UNITED STATES OF AMERICA
' NUCLEAR REGU!,ATORY COMMISSION
-In the Matter of
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Texas Utilities Electric Company
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Docket Nos. 50-445
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50-446 (Comancho Peak Steam Electric
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Station Units 1 & 2)'
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AFFIDAVIT William J. Cahill, Jr. being duly sworn, hereby deposes and says that he is Executive Vice President,-Nuclear of TU Electric, the Applicant herein: that he is duly authorized to sign and file with the Nuclear P.egulatory Commission this response to NRC Bulletin 88-04; that he is familiar with the content thereof; and that the matters set forth therein are true and correct to the best of his knowledge, information and belief.
William J. Ca
- 1. Jr.
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Executive Vic resident, Nuclear l
STATE OF TEXAS
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' COUNTY OF DALLAS
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Subscribed and sworn to before er, a Netary Public in and for nex on this M '_' day of Ma/
, 1989, 1
j Nota,,P.,,1c 4
My commission expires:
1 1
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' ' Attachment to TXX-89251 M'ay 26, 1989 Page 1 of_4 F.ESPONSE TO NRC BULLETIN 88-04 POTENTIAL SAFETY-RELATED PUMP LOSE Action Item #1:
"Promptly determine whether or not its facility has any safety-related system with a pump and piping system configuration that does not preclude pump-to-pump interaction during miniflow operation and could therefore result' in dead heading of oie or more of the pumps."
RespoDifi
' TV Electric identified the following systems with pump and piping system
- configurations that do not preclude pump-to-pump interface during miniflow operation.and could potentially result in dead-heading one or more pumps thus preventing performance of its safety function. These systems are:
Chemical & Volume Control (CVCS)
(Boric Acid Transfer and Centrifugal Charging Pumps)
(Containment Spray Pumps)
Action Item #2:
"If the situation described in Item I exists, evaluate the system for flow division taking into consideration, (a) the actual line and component resistances for the as-built configuration of the identified system; (b) the head versus flow characteristics of the installed pumps,. including actual test data for " strong" and " weak" pump flows; (c) the effect of test instrument error and reading error; and (d) the worst case allowances for deviation of pump test paremeters as allowed by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI Paragraph IWP-3iOO."
Resconse:
The safety-related systems identified in response to Item I have been evaluated as delineated in Item 2 and the results are as follows:
The current CVCG configuration for the suction and discharge lines of the Boric Acid Transfer (BAT) pumps has the potential for dead-heading these pumps when both Units 1 and 2 are operating. A modification to the CVCS configuration was approved to address this issue. The modification will assure that no more than one operating BAT pump will rely on a single throttle valve which is located in a recirculation line for minimum flow protection.
This modification will eliminate the potential for damage to an active pump resulting from simultaneous operation of Units 1 and 2 and will be implemented prior to Unit 2 fuel load.
1.
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Attachment to TXX-89251 May 26, 1989 Page 2 of 4 The current CVCS configuration for the suction end discharge lines of the Centrifugal Charging pumps, when using alternate miniflow lines, has the potential for dead-heading these pumps.
Another derign modification recommended by Westinghouse has been initiated for both Units to address this potential pump-to-pump interaction.
The alternate miniflow relief valve inlet lines will be moved upstream of the discharge check valves to eliminate this potential for pump dead-heading. The Unit 1 modification will be completed prior to fuel load and the Unit 2 modification will be completed as part of the completion activities for Unit 2.
The Westinghouse evaluation of the CT system concluded that while the system configuration during operating modes had the potential for dead-heading to occur since the discharge lines of the CT pumps cre connected to a common header, dead-heading is prevented by the following design features:
1.
The CT recirculation system is designed such that each pump operates at approximately 25% of best efficiency flow when all pumps are operating. Therefore, low flow conditions, where the pumps are susceptible to dead-heading, are avoided.
2.
The vast majority of hydraulic resistance occurs in the individual 4 inch portion of the CT pump discharge lines as opposed to the common RWST header. This configuration minimizes the effect that one pump can have on parallel pumps because this reduces the pressure at the common miniflow header such that the weaker pump will still have sufficient miniflow.
Westinghouse's analysis further indicated that., based on its calculations, dead-heading is not possible during the operation of the CT pumps in the recirculation mode because of piping resistance and vendor rated pump developed head considerations.
Action Item #3:
" Evaluate the adequacy of the minimum flow bypass lines for safety-related centrifugal pumps with respect to damage resulting from operation and testing in the minimum flow mode. This evaluation should include consideration of the effects of cumulative operating hours in the minimum flow mode over the lifetime of the plant and during the postulated accident scenario involving the largest time spent in this mode. The evaluation should be based on best 4
current estimates of potential pump damage from operation of the specific pump models involved, derived from pertinent test data and field experience on pump damage. The evaluation should also include verification from the pump suppliers that current miniflow rates (or any proposed modifications to miniflow systems) are sufficient to ensure that there will be no pump da. mage from low flow operrtion.
If the test data do not justify the existing capacity of the bypass lines (e.g.. if the data do not come from flows compar6ble to the current capacity) or if the pump supplier does not verify the adequacy of the current miniflow capacity, the licensee should provide a plan to obtain additional tett data and/or modify the miniflow capacity as needed."
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Attechment to TXX-89251 May 26, 1989 Page 3 of 4 Responigi TV Electric ar,a Westinghouse have evaluated the adequacy of minimum flow bypass lines for safety-related centrifugal pumps with respect to dasage resulting from operation and testing in the minimum flow mode. This review was based on considerations that included pump damage estimate data derived from preoperational test data, acceptable csiculated flow rates, and supplier verified data. The evaluation included consideration of cumulative operating hours in the minimum flow mode over the lifetime of the plant and during the postulated accidert scenario involving the largest time spent in the mode.
The system pumps that were e9aluated are listed as follows:
System Pugnt Nodel n) Boric Acid Transfer Pump Chempump Model GVH-10K, GVHS-10K b) Auxiliary Feedwater Motor Ingersoll-Rand Model 4 HMTA-9 Driven Pump c) Aux 111sry Feedwater Turbine Ingersoll-Rand Model 5 HHTA-6 Driven Pura d) Station Service Water Pump Hayward Tyler Pump Model 24 VSH e) Reactor Makeup Water Pump Bingham-W1111amette Model 2x3x9HCAP f) Centrifugal Charging Pump Pacific Pump Model 2 1/2 RL-IJ g) Safety Injection Pump Pacific Pump Model 3 in. JHF h) ResidJal Heat Removal Pump Ingersoll-Rand Model 8x20 WDF
- 1) Component Cooling Water Pump Bingham-Williamette HSA 18x20x24 j) Containment Spray Pump Bingham-Williemette HSA 10x12x25
(* - Evaluation performed by TU Electric, others performed by Westinghouse)
With the modification described in Action Item #2. the pump minimum flow configurations and flow rates were found to be adequate for all of the pumps evaluated except the Reactor Makeup Water (RMW) pumps, The other pumps would be able to perform their safety function under the conditions evaluated.
The evaluation results for the RMW pump, however, initially identisied a calculated low flow rate that could result in abnormal wear and aging of system pumps. On January 26, 1989, these pumps were functionally tested utilizing an ultrasonic flow measuring devise.
The recirculation flow rate results obtained from this functional test exceeded the calculated required minimum flow rate determined by Westinghouse.
Based on this result, it was concluded that no increase in required maintenance is expected for these l
pumps.
l The proposed modification to the miniflow systems described in the response to Action Item #2 and the evaluated system pump flow rates were shown to be sufficient to prevent abnormal pump aging due to low flow operations. There was no evidence of an increase in the probability of occurrence or l
consequences of an accident.
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Attachment to TXX-89251 May 26, 1989 Page 4 of 4 Acti qp _ Item #4 :
Within 60 days of receipt of this bulletin, provide a written response that (a) summarizes the problems and the systems affected. (b) identifies the short-term and long-term modifications to plant operating procedures or hardware that have been or are being implemented to ensure safe plant operations (c) identifies an appropriate schedule for long-term resolution of this and/or other significant problems that are identified as a result of this bulletir., and (d) provides justification for continued operation particularly with regard to General Design Criterion 35 of Appendix A to Title 10 of the Code of Federal Regulations (10 CFR 50), " Emergency' Core Cooling" and 10 CFR 50.46, " Acceptance Criteria for Emergency Core Cooling System for Light Water Nuclear Power Reactors."
Resoonse:
Since CPSES is not in operation at this time, short term modifications to plant operating procedures or hardware are not required. The CVCS BAT pumps and charging pump alternate miniflow modification will be completed as described in our response to Action Item #2.
Action Item #5:
"Within 30 days of completion of the long-term resolution actions, provide a written response describing the actions taken."
Besoonse:
TU Electric will provide a written response describing the actions taken within thirty days of completion of the long-term resolution actions.
Action Item #6:
"An evaluatio.n of your actions in response to this bulletin should be documented and maintained at the plant site for a minimum of two (2) years.
That evaluation should, as a minimum, address the piping system configuration in accordance with Item 1 above, each of the four factors discussed in Item 2, pertinent test data and field experience on minimum flow operation, and verification of the adequacy of current miniflow capacity by the pump manufacturer."
Response
TU Electric will maintain a documented evaluation of the actions taken in response to NRC Bulletin 88-04 for a minimum of two (2) years following the completion of the proposed modifications.
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