ML20198E665
| ML20198E665 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 08/21/1985 |
| From: | Massin H COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 0425K, 425K, NUDOCS 8511140127 | |
| Download: ML20198E665 (6) | |
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i Commonwealth Edison
' one First Nation't Plaza. Chic'go. Ilknois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 August 21, 1985 PRIORITY R M M
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f8Q Mr. James G. Keppler
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Regional Administrator
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799 Roosevelt Road - Region III
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Subject:
LaSalle County Station Unit 1 Deferral of Unit 1 High Drywell Temperature Modification NRC Docket No. 50-373 References (a):
C.W. Schroeder Letter to J.G. Keppler Dated December 22, 1983, Report on High Drywell Temperature (b):
J.G. Marshall Letter to J.G. Keppler dated September 4, 1984, High Drywell Temperature Long Term Corrective Actions
Dear Mr. Keppler:
Reference (a) identified to Region III the short term actions which Commonwealth Edison planned to take to address the problem of high tempera-tures in the Unit 1 drywell. Reference (b) informed you that the scheduled completion dates for modifications that implement long term corrective action regarding the observed initial high drywell temperature problems were the end of the first refueling outage for each unit. This letter documents our judgment for amending that commitment by deferring the LaSalle Unit 1 drywell cooling modification until the second refueling outage at Unit 1.
The intent of this modification is to restore drywell cooling redundancy.
The Unit 1 drywell cooling modification consists of two essentially independent jobs: ' work inside the drywell for additional coolers with the associated piping and ductwork, and work outside the drywell for an additional chiller and increased chilled water flows. Our intention is to defer the inside drywell work to the second refuel outage.
Interim actions taken to improve drywell cooling have been successful in decreasing temperature to the point where the equipment's qualification status and the continued operation of the plant is not affected. CECO has evaluated the status of drywell cooling and has enneluded there is no negative impact during normal operations from deferring inside drywell wurk.
Drywell temperatures pose no hazard to the operability of environmentally qualified equipment (see Attachment). The analysis reported in Table I of the attachment is judged to be conservative and yet adequately establishes a511240227 esos21 AUG 2 31985 DR ADOCK 05000373 p
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v J.'G. Keppler August 21, 1985 the-qualification of safety-related equipment located in the drywell with the cooling system left in its current configuration. Postponement of the drywell portion of the proposed modification for the upcoming Unit 1 outage will not, therefore, adversely affect the qualification analyses presently on file.
The deferral of this work is part of an overall program to reduce the scope of work scheduled for the Unit 1 first refuel outage. Primary candidates for deferral are jobs which have the following characteristics:
(1) Large complex jobs on which engineering design has not been finalized.
(2) Jobs which may require a large number of engineering changes while the physical work is in progress.
(3) Drywell work.
The drywell cooling project falls in each of these categories.
If you have any questions regarding this matter, please contact this office.
Very truly yours, bd H. L. Massin Nuclear Licensing Administrator 1m Attachment cc: Dr. A. Bournia Region III Inspector - LSCS 0425K
r ATTACFNENT During the startup of Unit 1 it was determined that a single containment cooling equipment train, i.e., one chiller, one chilled water pump, one chilled water cooler and fan were unable to maintain the drywell temperature below 135oF average temperature. The unanticipated high temperature was due to higher than calculated sensible heat load.
The station was able to operate satisfactorily using one chiller, two chilled water pumps, two fan coolers and two fans. For brief periods of high lake temperature a second chiller is used. In a subsequent shutdown of Unit 1, damage to electrical cables was noted by station personnel. A systematic inspection of the Unit 1 drywell and equipment was conducted.
The operating temperature readings from drywell monitors were used to establish a temperature profile for the drywell. Some additional tempor-arily installed thermocouples around the safety relief valves were also utilized for temperature indications. A correlation was made of available temperature data and observed damage. The bulk high temperature effects appear to be limited to elevation 804 feet and above with some local problems below that level. The degradation problem was caused by excessive hot spots. The local spots on some cable coincided with physical contacts on hot piping or high temperature surfaces. Only the upper area of the drywell had a volumetric or bulk overtemperature.
The high drywell temperature resulted from poor air flow distribu-tion, inadequately sealed penetrations, gaps in installed thermal metallic reflective insulation, and a full perimeter thermal gap around the RPV.
An evaluation was performed by Sargent & Lundy Engineers which included the following:
the primary containment structure the drywell cooling system the biological shield the electric cable mechanical and electrical equipment in the drywell Corrective actions were performed a; delineated in CECO's transmit-tal to the U.S. NRC Region III dated December 22, 1983, from C. W. Schroeder to J. G. Keppler (reference (a)).
In CECO's letter dated September 4, 1984 from J. G. Marshall to J. G. Keppler (reference (b)), we identified our long term corrective actions and schedule to restore drywell cooling redundancy.
Following the initial discovery of the high drywell temperatures, an assessment of the remaining qualified life was completed for all safety-related equipment and cables. This assessment was based on actual plant data extrapolated to include areas where measurements were not directly taken. The results of this assessment are provided in reference (a); refer m
s.
-. to page 5, table III-1 for safety-related electrical equipment and to page 9, tables XV-1 and IV-2 for cables. Based on this analysis, the following actions were taken: -All safety-related electrical cables above elevation 796'-0" were replaced as well as nineteen (19) mechanical snubbers. All remaining cable and equipment, althouoh having a decreased service life due to overtemperature conditions, were judged to be undamaged and were retained.
Also reported in table IV-2 of reference (a) were maximum allowable temperatures for cable such that the remaining qualified life would not expire before replacement, which, if necessary, cculd be implemented during the first refueling outage. These maximum temperatures were intended to represent threshold values not to be exceeded during subsequent unit operation.
Following the return to service of the unit, an augmented temperature monitoring program was instituted to assure that the above pre-defined thresholds were in fact not exceeded. Additionally, this monitoring program provided actual plant data which formed the basis for the reevaluation of qualified life, as discussed below.
Actual plant data collected between November 1983 and May 1984 were used to develop thermal gradients within the drywell based on plant power conditions. For each safety-related component or family of components, a service temperature was identified from this data base. This value was assumed to persist for the remaining plant life and yielded qualified lives as reported in Table I below.
TABLE I Qualified Item, Manufacturer Model No.
Life (years)(1)
Reference Solenoid Valves, Crosby IMF-2
> 10 EQ-LSO41 Solenoid Valves, Asco HTX832320V, 40(2)
CQD-020141 HTX8320A20V Solenoid Valves, Asco HVA-206-852 40 EQ-LS001 Penetration Assemblies, Conax Custom 40 EQ-LSO40 EQ-LS005 EQ-LS023 EQ-LSO24 Thermocouples, Weed EAB 39.5 EQ-L5029 Resistance Temperature 611 40 EQ-LS030 Detectors, Wced
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TAELE :I (Cont'd)
Qualified Item;~ Manufacturer Model'No.
Life (years)(1)
Reference Limit Switch, Namco-EA-740 40 EQ-LS019 Radiation' Detector, General RD-23 40 EQ-L5032 Atomics Seal Assemblies, Namco EC-210 4.l(3)
EQ-LSO44 Valve Operators,'Limitorque SMB 40 EQ-LSO45 Lift Indicating Switch
-SN/65256-00-0027 40(4)
EQ-LS083(4)
Assembly, Crosby Cables Various Okonite Co.
40 EQ-LSO25 Samuel Moore 40 EQ-LS051 Rockbestos 40 EQ-LS052 EQ-LS053 Raychem 40 EQ-LS055 t
NOTES:
1.
It may be necessary to perform maintenance, including part replacement, to preserve the reported qualified life.
- 2. :These solenoids are to be replaced during the refueling outages with the NP-series valves.
3.
Initial installation of these devices is scheduled during the refueling outage; they were not installed during the high temperature exposure.
4.
Final documentation is in final preparation.
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,. s Note that the above analysis did not take credit for unit outages or further improvements to the drywell cooling system.
No credit has been taken in the determination of qualified lifetime for the proposed drywell cooling modification. When the modification is installed, and if the monitoring program confirms additional margins have been attained, the margins to the qualified lifetimes for selected components might very well be increased.
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