ML20084D813
| ML20084D813 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/22/1970 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8304120424 | |
| Download: ML20084D813 (2) | |
Text
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Regulatory Fife Cy.
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Dresden Nuclear Power' Station
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Dr. Peter A. Morris, Director
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Division of Reactor Licensing
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U.S. Atomic Energy Commission Washington, D.C.
20545 SUMECT: LICENSE DPR-19 DRESDEN NUCLEAR Po*.iER STATION UNIT 2. SECTION 6.6.B.3 0F THE TECICiICAL SPECIFICATIONS
Dear Dr. Morris:
This is to report a condition relating to the operation of the station in uhich on October 15, 1970, at approximately 6:00 p.m.,
an unplanned release of a small caount of radioactive liquid waste resulted from heating boiler blowdown after the plant heating system water had been contaminated.
Prob 1cm, Investication, and Corrective Action The Unit 2/3 radwaste concentrator is operated on heating steam from the plant heating system.
The heating secam condensate return has l
a two way valve, controlled by condensate conductivity, which normally I
returns the condensate to the heating boiler if conductivity is less than 2 pmho/cm.
If the conductivity is greater than 2 pmho/cm, the condensate is d4verted to the waste co11cetor.
Prior to the occurrence the condensate return was being routed to the waste co11cetor because of high conductivity. Considerable difficultics had been experienced with this conductivity cell and its accuracy was questionabic.
On October 13, 1970, at approximately 2400 hours0.0278 days <br />0.667 hours <br />0.00397 weeks <br />9.132e-4 months <br />, the conductivity cell indicated a step increase and remained upscale.
To determine accuracy of the cell, and to determine if the condensate could be routed back to the heating boiler, a sample was collected from the concentrator's heating system condensate return on October 14, 1970, and analyzed in the laboratory for conductivity and radioactivity.
The sample verified the accuracy of the conductivity cell, but also showed a Icvel of f
radioactivity of 512 pCi/1. At that time the waste concentrator was a
shutdown.
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8304120424 701022 PDR ADOCK 05000237 S
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.o Dr. Peter A. Fberis October 22, 1970 A sample of the heating boiler water was taken at approximately 4:00 p.m. on October 15, 1970, and analysis indicated that it contained an activity of approximately 3 x 105 pCi/1. Upon receiving the results of the analysis at 6:45 p.m., the Shift Engineer ordered the operator not l
to blow down the heating boiler.
At that time the operator informed the shift engineer that he had just blown down.the boiler.
He estimated that his blowdown had reduced the boiler drum water level by about 4 inches and that the blowdown had been of about 5 minutes duration.
Investigation of the occurrence revealed that a discharge rate of approximately 27 gallons per minute of heating boiler water, in con-junction with normal planned release in progress at the time, resulted in an activity discharge rate in the discharge canal of approximately 276 pCi/1 for abou t five minutes.
The source of the radioactivity in the heating boiler water is presently believed to have been Icakage_from the waste concentrator.
Investigation and testing the following day in3Icated that the waste concentrator had numerous leaks, both in the shell and tube bundle.
The occurrence was reviewed by the station review board the following day, October 16, 1970.
The review board considered the procedures used to terminate the release were appropriato. A procedure was formulated to cican up the heating boiler system by draining to radwaste, refilling, operating the boiler to concentrate activity, draining, refilling, etc.
Investigation will continue to confirm the source of the heating boiler water activity.
The leaking concentrator will be replaced by a new concentrator.
Investigation will continue into the cause of the failure of the vaste concentrator.
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