ML20084Q845
| ML20084Q845 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 08/20/1973 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084Q849 | List: |
| References | |
| NUDOCS 8306140293 | |
| Download: ML20084Q845 (2) | |
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O.J Czmm nwIilth Edis:n Ouad-Cities Nuclear Power Station Post Offico Box 216 I
Cordova, tilinois 61242
.<E' Telephone 309/654-2241
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August 2d, 1973 t.{ \\ gg> ['
l lc J. F. O' Leary, Director Directorate of Licensing U. S. ATOMIC ENERGY COMMISSION Washington, D. C.
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SUBJECT:
quad-CITIES NLCLEAR POWER STATION - Unit 1 1
Docket No. 50-254; DPR-29, Appendix A, Section 1.0.A.2, 3.7.A.1 and 6.6.8.1
Dear Mr. O' Leary:
On August 10, 1973 with the Unit I reactor shutdown the suppression chamber water level exceeded the requirements of Technical Specification.3.7.A.I.
The purpose of this letter is to inform you of the details of this abnormal occurrence which was previously reported by telegram on that date.
PROBLEM & INVESTIGATION At 0021 on August 10, 1973 an air leak developed on main steam isolation valve 203-10 The valve drifted closed and the reactor subsequently isolated and scrammed. Following the scram a cooldown was initiated in preparation for a drywell entry to inspect and repair the MSIV air line. At about 0625, re-actor pressure had been reduced to less than 50 PSIG and the control room operator was preparing to initiate the shutdown cooling system.
In doing so an incorrect valve lineup was created and water from the condensate sto-rage tank increased the level in the suppression chamber to +24" thus ex-ceeding Technical Specification 3.7.A.I.b.
EVALUATION AND CORRECTIVE ACTIONS A.
Safety lmolications The LCO of specification 3.7.A.I.b. requires that the suppression chamber level be maintained between +2 and -2 inches when the reactor is not in the cold shutdown condition. At the time that the upper limit on level was exceeded, the reactor had been shutdown with all rods in for over six hours and was very close to being less than 212 degrees. Thus the safety significance of this occurrence is relatively minor.
As described below the IA RHR pump was Inoperable for a period of about.
24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> because its suction valve was closed. Monthly surveillance l
on the RHR system had been conducted on August 8, 1973, however, thus all remaining components of the system were known to be operable. Three of the four pumps are required for the RHR system to perform its safety function.
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1 Mr. J. O ' Leary August 20, 1973 8.
Determin'ation of Cause and Corrective Action
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On August 9,1973, prior to the scram a procedure had been developed for flushing the RHR system piping in order to reduce radiation levels in the l
room resulting from previous shutdown cooling system operations. This procedure required closing the IA pump suction valve from the suppression chamber,1001-7A, opening the suction valve from the condensate storage tank, 1001-42A, and flushing through valves 1001-20 & 21 to the conden-ser. Due to a misunderstanding on the day shift of August 9, however, this procedure was not completed and the valve lineup was not returned to normal. At the time of the occurrence the operator noticed that the RHR torus suction valve was still closed and when he opened it, a flow path was established directly from the condensate storage tank to the torus. The immediate corrective action was to close the 1001-7A valve from the control room and then return the manual valves from the storage tank to their normal position.
In order to prevent a repetition of this type of occurrence in the future, temporary procedures involving abnormal valve lineups in safety systems will be supervised directly by an Individual with no other res'ponsibill-
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ties. This individual.will work through the shift engineer and unit operator keeping them Informed of any changes in system status. He will be given no other dutics until the evolution is completed and will re-port to the shif t engineer and operating engineer when all systems have been returned to normal. These requirements will be added to the sta-tion's standing orders.
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Comulative Exeerlence A similar occurrence involving an abnormal RHR system valve lineup took place prior to a Unit 2 reactor startup on December 20, 1972 In view of this it is recognized that additional controls such as those des-cribed above are necessary.
In addition, a " GREEN BOAR 0" panel indica-ting scheme is being evaluated on a trial basis at the Dresden Nuclear Power Station. This system would make an abnormal valve lineup immediately apparent to the control room operator. There are, of course, disadvan-tages to such a scheme but if it proves acceptable from an operating view point it will be adopted at QUAD-CITIES.
Very Truly Yours, COMM0HWEALTH EDISON COMPANY QUAD-CITIES NUCLEAIUPOWER STATION
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, Station Superintendent
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cc: Regional Director Directorate of Regulatory Operations,- Region ill BBS/dkp 885-73-165
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