ML19347D738
| ML19347D738 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, LaSalle  |
| Issue date: | 03/19/1981 |
| From: | Rausch T COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-80-25, NUDOCS 8103261193 | |
| Download: ML19347D738 (7) | |
Text
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Commonwealth Edison One First National Pina. Ch.cago filinois Address Reply to: Post Office Box 767 Chicago Illinois 60C90 s
- [1@f gf4 March 19, 1981 s
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I-Mr. James G. Keppler, Director Directorate of Inspection and
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- b2OI98Ihmh7 Enforcement - Region III 9' "*4 jg2y"nmam,g; U.S. Nuclear Regulatory Commission
/s 799 Roosevelt Roaa c,
y Glen Ellyn, IL 60137 so o
Subject:
Dresden Station Units 1, 2 and 3 Quad Cities Station Units 1 and 2 LaSalle Station Units 1 and 2 Response to IE Bulletin 80-25
" Operating Problems with Target Rock Safety-Relief Valves at BWRs" NRC Dociet Nos. 50-10/237/249, 50-254/265, and 50-373/374 Reference (a):
J. G. Keppler letter to C. P.eed dated December 19, 1980
Dear Mr. Keppler:
Reference (a) transmitted IE Bulletin 80-25 requiring a response to concerns identified with Target Rock Safety-Relief valves at BWRs.
The Commonwealth Eaison Company responses for Dresden Units 1, 2, and 3, Quad Cities Units 1 and 2, and LaSalle Units 1 and 2 are provided in the enclosure to this letter.
In the case of LaSalle County Units 1 and 2, our response indicates that the engineering review of the Safety-Relief valve pneumatic supply systems i, still in progress.
We intend to provide the complete LaSalle response within two months.
Modifications determined to be necessary will be completed prior to the fuel load dates for the respective units.
To the best of my knowledge and belief the statements contained herein and in the enclosure are true and correct.
In some respects these statements are not based on my personal knowledge but upon information furnished by other Commonwealth Edison employes.
Such information has been reviewed in accordance with Company practice and I believe it to be reliable.
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Please a
.ess any questions you may have concerning this matter to this off.ce.
Very truly yours, C
%4 Thomas J. Rausch Nuclear Licensing Administrator Special Projects Attachment cc:
NRC RIII In'spector - Dresden NRC RIII Inspector - Quad Cities NRC RIII Inspector - LaSalle Director of Inspection and Enforcement-(WA)
SUBSCRISED and SWOJN to before me this N 17/
day of 2/M
-c 1981 f
Not ary7 ub l i c 15898
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T Enclosure Commonwealth Edison Company Kesponse to IE Bulletin 80-25 Dresden Unit 1 This bulletin does not apply to Dresden Unit I since there are no combined safety relief valves on the unit, and none of the relief valves are pneumatically operated.
Dresden Units 2 and 3 1.
Dresden presently utilizes two 3-stage Target Rock Safety-Relief Valves, one each on Units 2 and 3.
The solenoid actuators installed are manufactured by the Automatic Valve Company (AVCo.), Model C-5450-5.
The Unit 2 Target Rock Safety-Relief Valve was last operateo during relief valve operability testing curing unit startup on October 20, 1979.
The Unit 3 Target Rock Safety-Relief Valve was last operated for relief valve operability testing durin unit startup on May 5, 1980.
Since Dresden Station does not use the 2-stage Target Rock valves on the Target Rock solenoid actuators, this item of the Bulletin does not apply.
2.
Tha overhaul requirements specified in Item 2 of the Bulletin will not be incorporated in the Dresden operating procedures.
Dresden Station utilizes comprehensive maintenance procedures for testing ano overhaul of the Target Rock and Electromatic Safety-Relief Valves.
Maintenance procedures, DMP 200-35 and DMP 200-37, explicitly detail instructions for removal, disassembly, inspection, and adjustment of the valves.
Valve and actuating mechanism design does not allow for pressure setpoint testing with steam prior to return to service.
The specified procedures are useo both for periodic overhaul surveillance and subsequent to valve failures.
All failures of the Target Rock and Electromatic Safety-Relief Valves are reported in License Event Reports.
3.
As required in Item 3, a comprehensive review and walkdown of the Drywell Pneumatic System and Backup Nitrogen Supply System on both units was conducted at Dresden Station.
These systems provide a pneumatic supply to the Target Rock Safety-Relief Valve, Ma' Steam Isolation Valves (MSIV's), and other miscellaneous air-operated valves in the drywell.
Normal supply to the drywell air-operated valves is via the Drywell Pneumatic System from the pump-back air compressors.
The drywell pneumatic air compressors are tied into the Pump-Back System.
The pump-back air compressors take suction from the torus ano supply both i
I
' drywell instrument air and the drywell itself with nitrogen, maintaining the proper drywell-to-torus differential pressure via a controller located in the control room.
The drywell pneumatic compressors take their suction from the drywell atmosphere and supply the drywell i
pneumatic supply header with a pressure range of 80-100 psig.
Pressure relief is proviaed for the Drywell Pneumatic System at the compressors and receiver tank and are set at 125 psig.
The Pump-Back System provides nitro 9en at a nominal pressure of 100 psig.
Pressure relief is set at 125 psig for the pump-back compressors and receiver tank.
If the Pump-Back System was to fail to maintain 80 psig to the drywell pneumatic supply header, the first drywell pneumatic compressor would start and supply nitrogen to the drywell air-operated valves.
If the drywell pneumatic supply header pressure continues to drop, at 75 psig the idle drywell pneumatic compressor would start.
If the pressure is still dropping at 70 psig, the Drywell Pneumatic Supply Tank Low Pressure Alarm would annunciate, resulting in the opening of the backup nitrogen supply valve.
Nitrogen would now be admitted to the header from the bulk nitrogen storage tank.
The backup nitrogen supply is regulated upstream to approximately 120 psig from the bulk nitrogen storage tank.
The tank has a nominal pressure of 180 psig and an upper limit of 275 psig (based on tank nameplate working pressure of 250 psig).
At a drywell pneumatic l
header pressure of 60 psig, the Drywell Pneumatic Supply Trouble Alarm would annunciate, indicating that the backup nitrogen supply is not maintaining pressure.
It can be determined from the above information that the maximum pressure the valves could be exposed to would result from the failure of the regulating valve downstream of the storage tank.
NRC IE Information Notice No. 80-40 specified that the AVCo. solenoid valves have been tested to 300 psig and found not to leak.
Since Dresden Station employs the AVCo. solenoid valve, a failure of the regulating valve would result in an overpressurization of less than 300 psig.
Therefore, the overpressurization problem does not exist at Dresden Station.
As an aditional measure, a work request (D-09927) was initiated to install a pressure relief-valve downstream of the regulating valve.
The relief would eliminate any possible
g' overpressurization occurrences at Dresden and the addition of high pressure alarm annunciation is considered unnecesary.
4.
The contents of IE Bulletin 80-25 have been fully reviewed by station personnel.
It is our belief that the overpressurization problem described is not a problem at Dresden Station.
Existing system components, procedures, and instrumentation are adequate.
The above described work request is an added safety feature which will result in the elimination of a possible minor overpressurization and the time schedule for installation of this modification should not be dictated by IE Bulletin 80-25.
Quad Cities Stations Units 1 and 2 1.
Quad Cities Station has one Target-Rock Safety-Relief Valve (SRV) installed on each unit.
Both are 3-stage valves.
The solenoid actuators are manufactored by Automatic Company (AVCO), Model No. C5450-5.
It is not intended to change to the 2-stage Target-Rock Valves.
The Unit One Target-Rock SRV was last operated during relief valve operability testing during Cycle 6 Startup on December 20, 1980.
Tne Unit Two Target-Rock SRV was last operated during a reactor scram and Group I Primary Containment Isolation on December 3, 1980.
All main steam relief valve actuations are reported in the NRC Monthly Operations Report.
Since Quad Cities Station does not utilize 2-stage Target-Rock valves nor Target-Rock solenoid actuators, this item in the Bulletin is judged to be not applicable.
2.
Requiring operating procedures to require remedial measures for faileo safety-related equipment is deemed inappropriate.
Quad-Cities Station Utilizes comprehensive procedures for the testing and overhaul of Target-Rock and Electromatic Relief Valves.
The overhaul procedures (QMP 800-9 & 10, and QMS 800-5) outline detailed steps for the removal, disassembly, inspection, and adjustment of the valves.
Further, the design of the valves and their actuating mechanisms do not allow pressure setpoint testing with steam prior to return to service.
The abr e procedures are utilized both during periodic overb i surveillance, as well as subsequent to failures.
A1, failures are reported as LERs, and the cause and corrective action is provided
.in the individual report.
- 3.
In accordance with Item 3 of the Bulletin, a review of the Drywell Pneumatic System for each unit has been conducted.
This system provides a pneumatic supply to the Target-Rock SRV, MSIVs, and other miscellaneous air-operated valves in the drywell.
Normal supply is via air compressors (approximately 90 psig) that take a suction from the drywell atmosphere and discharge back into the drywell pneumatic header.
Upon low pneumatic header pressure (approximately 70 psig), a backup nitrogen supply valve opens.
This nitrogen bulk storage tank nominal pressure of about 185 psig..
The nitrogen buld storage tank has a nominal pressure of 185 psig and an upper limit 275 psig (based on tank nameplate working pressure of 250 psig).
Per NRC IE Information Notice 80-40, the AVC0 solenoid actuators have been pressure tested successfully to 300 psig.
Thus, a nitrogen supply overpressure situation (from a postulated regulator failure) will not result in a valve malfunction.
Further, Modifications M-4-1-80-33 and M-4-2-80-33 have been initiated to install relief valve protection on the drywell pneumatic supply header to the drywell.
A low drywell pneumatic system header pressure alarm currently exists in the Control Room.
Instrument setpoint change Number 228 has been initiated to change an existing redundant low pressure alarm to a high pressure alarm in the Control Room.
These alarms are sensed on the drywell pneumatic supply header to the drywell.
This point is located downstream from where the nitrogen backup supply is tied into the system.
Operating procedures changes will be made, as deemed necessary, upon completion of the modifications and instrument setpoint changes.
4.
We will attempt to complete the modification and setpoint changes within six months from the time the necessary parts are available on-site, however since the existing system is adequate, we do not feel that the time frame indicated in the bulletin should be mandatory.
LaSalle County Station Units 1 and 2 1.
LaSalle Station Safety-Relief Valves are manufactured by Crosby Valve Company, therefore this item does not apply.
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5-2.
The Safety-Relief Valves will not be overhauled on-site, but will be sent to Wyle Laboratories for overhaul in the event of malfunctions not clearly determined and corrected.
Station procedures will be revised prior to fuel load to describe the action to be taken in the event of a malfunction.
3.
The engineering review of the Safety-Relief Valve pneumatic supply system is still in progress.
We intend to provide a complete response to this item within two months.
Any modifications determined to be necessary will be completed prior to the fuel load dates for the respective units.
15898 s
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