ML19210A167

Nonroutine 10-Day Rept 75-08 Re 751119 Unplanned Release of Radioactivity.Two Open Valves Vented Radioactive Gas from Coolant Drain Tank to once-through Steam Generator.Caused by Inadequate Procedures.No Tech Specs Limits Exceeded

ML19210A167
Person / Time
Site:	Three Mile Island
Issue date:	11/26/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
Shared Package
ML19210A165	List: ML19210A164 ML19210A167
References
75-08, 75-8, NUDOCS 7910240891
Download: ML19210A167 (2)

Text

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UONRCUTINE 10 !'AY REPCRT 75-08 REPORT OF AN UNFLAN'!ED RELEASE OF RADI0 ACTIVE MATERIAL

< CCCURRING CN UOVEMPER 19, 1975 Descriptien of Occurrence:

On November 19, 1975 between the hours of 02h5 and 1830 (15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> and L5 minutes),

an inadvertent release of gasecus radioactive material occurred due to opening BS-V23A/B and FS-V25A/B in accordance with the Operating Procedure 1106-16, Once Through Steam Generator Wet and Dry Layup Procedure. As a result of opening these two (2) valves , the Reactor Coolant Drain lank was vented to the seccadary side of the Cnce Through Stea= Generators. In doing this,the radioactive gas which was in the Reactor Ccolant train Tank was drawn into the steam generater which vac under a vacuum conditicn at the time, and subsequently drawn into the =ain ecndenser in the Turbine Building where it was discharged via the =ain condenser vacuum pumps to the Turbine Building vent. The release of the radioactive gas was detected 4-~adiately by the condenser vacuum pump effluent , radiation moniter RM-AS. When this occurred, the operators realized that the radicactive gas was coming frc= the venting cperation and i==ediately closed the valves SS-V23A/B and NS-V25A/3.

Upon investigation into the nature of the occurrence, it was determined that while the procedures were folleved as required, the step requiring the opening of the tvc (2) valves was inappropriate for the vacuts condition which existed in the steam generator at the time.

A second release occurred on Nove=te 9,1975 between the hours of 1955 and 2151 (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 56 =inutes) when a Reactor Coolant Pump was started as part of the plant heatup evolution. The resultant 10 F te=perature increase in the steam generators caused some radioactive gas to come out of solution and be released through the vacuum pump vent.

Cause of the Occurrence:

Procedure inadequacy was the apparent cause of the occurrence in that two (2) valves which were specified to be open in a venting precedure should rever have been opened in view of the conditions existing in the Steam Generator and Reactor Ccolant Drain Tank at the time of the occurrence.

Analysis of the Occurrence:

For the folleving reasons it is believed that the release of radicactive material en November 19, 1975, did not endanger either the health or safety of the public.

a. None of the limits of the TMI Unit 1 Technical Specifications were exceeded.

b. None of the maxi =um permissible concentration limits for non-radiation workers as given in 10 CFR 20 were exceeded at the site boundary.

c. No individual en site at the time of the release received a radiation dose in excess of the limits fbr radiatien vcrkere specified in 10 CFR 20.

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Corrective Action:

bediate corrective action as described above was taken to terminate the rele as e . Additicnally, the operating procedures vill be revit ed to prevent a recurrence of the incident by not venting the Orice Through Steam Generators secondary side to the Reacter Ccolant Drain Tank.

Failure Data:

Previous failure data - Hone Eauintent Identific ation:

Not Applicable.

Peles-c Data:

Note: In no case did any member of the public or any statien contractor personnel receive a radiation dose near the applicable limit given in 10 CFR 20.

The initial release censisted of 2.75 curies of predecinantly 133Xe (995). Based on radiation monitoring system strip chart recordings and samples of the affected area during the release, the maximum noble gas release rate during the 15 hour1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> h5 -

minute period was 8.26 x 102 g3/sec which is belev the Technical Specification ligit 3 f 1.2 x 105 M3 /sec. The average release rate during the period was 1.62 x 10 M /sec.

The second release censisted of 2 91 x 10-2 curies of predeminantly 133xe (99<,),

Similar to the above, the maximum ncble gas release rate during the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 5 x 10 1 M3 /see and the average release rate for the 56minuteperiodwas3.g/sec.

period was 1.39 x 101 M 1476 139