ML19261F193

Nonroutine 10-Day Rept 74-08 Re 741120-21 Unplanned Release of Radioactive Matl.Caused by Inadequate Procedural Guidance on Valve Closure Prior to Drawing of Vacuum.Valves Reclosed & Procedural Changes Initiated.No Excessive Doses Occurred

ML19261F193
Person / Time
Site:	Three Mile Island
Issue date:	11/30/1974
From:	METROPOLITAN EDISON CO.
To:
Shared Package
ML19261F185	List: ML19261F184 ML19261F193
References
74-08, 74-8, NUDOCS 7910250612
Download: ML19261F193 (2)

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ENCLOSURE Metropolitan Edison Company Three Mile Island Duclear Station, Unit 1 (TMI-1)

Docket No. 50-289 Operating License DPR-50 Nonroutine Report 74-08 Report of an Unplanned Release of Radioactive Material Occurring on November 9-20,1974

1. De;cription of Release:

Between the hours of 1940 and 0340 (8.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />) on November 19-20, 1974, while f a *he process of returning to power operation after a maintenance outage, an unplannad release of radioactive material occurred due to some improperly tightened valves in the vent line from the Reactor Coolant (RC) Drain Tank to the Steam Generators (SG) .

At the cime of the release both the Steam Generators and the Main Condenser were under vacuum and the Main Steam Vent Line Valves (not the leaking SG Vent Line Valves referred to above) and *Ne Turbine Bypass Valves were open. In that both the Condenser and Steam Generators were under vacuum and that there were open flow paths from the RC Drain Tank, through the Steam Generators, and to the Condenser, radiogas was drawn into the Condenser from the Drain Tank and was then discharged by the Condenser Vacuum Pumps through Exhdust Monitor RM-AS .

A high-level alarm was received in the Control Room from Exhaust Monitor RM-A5 and a gaseous sample was taken. Plant Operations personnel then proceeded to locate the source and cause of the release.

Having succeeded in this , they next re-closed the partially open valves , thereby reducing and eventually terminating the release.

No plant or contractor personnel were directly exposed to the released material in that it was completely contained in installed piping prior to its discharge from the plant.

2. Apparent Cause of the Release:

Inadequate procedural guidance was the apparent cause of the occurrence in that steps were not included in existing Station Operating Procedures to insure that the subject valves were tightly closed prior to drawing of a vacuum in the Steam Generators.

3. Analysis of the Occurrence:

For the following reasons it is believed that the unplanned telease of radioactive material on the 19th and 20th of November did not endanger either the health or safety of *.he public:

a. None of the limits of the TMI-l Technical Specifications were exceeded.

1481 109 7910250 b /8

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. . b. None of the Maximum Permissable Concentration limits for non-radiation workers listed in 10 CFR 20 were exceeded at the site boundary.

c. No individual on site at the time of the release received a radiation dose in excess of the limits for radiation workers listed in 10 CFR 20.

4. Corrective Action:

Immediate corrective actions were taken as described above to locate the source and cause of the release and then to secure the release.

As a leng-term preventative action procedural steps have been initiated to insure that the subject valves are tightly closed prior to the drawing of a vacuum in the Steam Generators.

5. Failure Data:

Not applicable.

6. Release Data:

Note:

• • • In no case did any member of the public or any plant or contractor personnel receive a radiation dose in excess of the limits stated in 10 CFR 20. ***

The total release consisted of 0.366 curies of predominantly Ze-133. These determinacions were obtained from the chart recordings of Exhaust Monitor RM-A5 and from a gaseous sample collected at dhe Condenser Vacuum Pump dischar e. The activity of this gaseous sample was measured as 4.72 x 10 uC1/ml. The gross gaseous release rate was 4.8 x 102 g3 which is well below the Technical Specification limit of 1.2 x 10/sec,3/sec 53 .

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