ML19262A169
| ML19262A169 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/24/1974 |
| From: | METROPOLITAN EDISON CO. |
| To: | |
| Shared Package | |
| ML19262A170 | List: |
| References | |
| NUDOCS 7910260491 | |
| Download: ML19262A169 (4) | |
Text
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ENCLOSURE (1)
Metropolitan Edison Cc=pany Three Mile Island Nuclear Station, Unit 1 (IMI-1)
Docket No. 50-289 Operating License No. DPR-50 Nonroutine 10-Day Raport b
C i m M[MU@][T Mt A
_a Report of Three Unplanned Radioactive Releases Occurring on October 6, 8, and 9-10,1974 1.
Description of Occurrences:
October 6 Between the hours of 0145 and 0415 (2.5 hcurs) on October 6,1974, an unplanned release of radioactive material occurred in the Reactor Coolant (RC) Was te Evaporator Roca of the Auxiliary Building due to a leak in the Vacuun Puno Discharge Diaphragm Valve of the RC Waste Evaporator System. This release was recorded by the RM-A8 Auxiliary and Fuel Handling Building Exhaust Monitor, but the level of radiation was so low that no " alert" alarn was received in the Control Rec =;
and the higher-than-normal reading was subsequently detected by a control rocs operator during a periodic check of the instrument.
A similar release occurrei again between the hours of 0815 and 1115 (3.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />) on October 6.
Again, the release was recorded by the RM-AS conitor and no " alert" alarm was received, and the higher-than-nor=al reading was subsecuently detected by a control rocs operator during a periodic chach of die ins trcnent.
October 8 Between the hours of 1000 and 1345 (3.75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br />) on October 8, 1974, an unplanned release of radioactive caterial occurred in the RC Waste Evaporator Roca of the Auxiliary Building dua to a leak in the loop seal of the RC Waste Evaporator Feed Tank. Both an alert-level and then a high-level radiation alarm were received in the Control Rocn from the Auxiliary Building Exhaust Monitor (RM-A6).
October 9-10 Between the hours of 2330 and 0300 (3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />) on October 9-10, 1974, an unplanned release of radioactive =aterial occurred in the Auxiliary Building. Both an alert-level and then a high-level radiation alar were received in the Control Room f rom the Auxiliary 3uilding Exhaust Monitor (RM-A6).
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In all of the above-described occurrences, as soon as the higher-than-normal readings were detected, the Auxiliary Building was ordered evacuated; personnel in the innediate area of each release underwent datontamination and were checked for ingested radioactive material and dosage received; appropriate correctiva actions were taken to secure the releases; and Health Physics personnel proceeded to the affected area to collect air and scear samples for analysis.
2.
Apparent Cause of Occurrences :
October 6 Cocoonent f ailure was the apparent cause of the unplanned releases of October 6, in that the Vacuus Fung Discharge Diaphragn Valve of the RC Waste Evaporator developed a leak.
October S Personnel error in the installing of a plug in the loop seal of the RC Waste Evaporator Storage Tank was the apparent cause of the unplanned release of October S.
A similar series of unplanned releases involving this loop seal occurred on Septenber 5, 6, and 7,1974 (::enroutina 10-Day Report 74-01, dated October 3,1974). As a result, it was decided to cut and plug the seal until the seal could be redesigned and cace a;ain cade cperaticnal; and it was the improper installation of the plug that pernitted ncble gases to escape from the vent header, through the loop seal, and into the RC Waste Evaporator Roo=.
October 9-10 The release was suspected to have resulted f rc= a leak or leaks in the Was te Evaporator Sys te=.
Two stall leaks were subsequently dis-covered: one was due to a ruptured disc on the RC Waste Evaporator Faed Tank and the other was due to a loose plug on the loop seal of the Feed Tank. It is believed that the ruptured dise was due to the inadequate fesi;n of the U:ste 2va: orator Feed T:nk loop seal (refer-ence Ncnroutine 10-Day Report 74-01) in that if the seal did not hava to be plugged, the disc ost likely would not have ruptured. Th e loose plug ca the loop seal is believed to be due to personnel error in that the installed plug was nor adequately tightened.
3.
Analysis of Occurrences:
For the following reasons it is believed that none of the unplanned releases in question endangered either the health or safety of the public:
a.
None of the limits in the TMI-l Technical Specifications were exceeded.
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b.
None of the >Mxi=un Per=issable Concentration li=its 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 releases received a radiation dose in excess of the li=1ts for radiation workers listed in 10 CFR 20.
4.
Corrective Action:
October 6 I==ediate actions were taken as previously described to protect per-sonnel and deter =ine levels of conta=ination. As a long-ter=
corrective action to prevent future releases, the leaking valve was replaced.
October 8 I==ediate actions were taken as previously described to protect per-sonnel and deter =ine levels of conta=ination. Also the loop seal plug was re-installed. As a long-ter: corrective action to prevent future releases, a co=prehensive progrc= with the following
=ajor provisions was instituted by plant =anage=ent.
a.
Extra watch standers were assigned on a temporary basis to =onitor those para =eters which might provide an insight into the condi-tions which are likely to precede an unplanned release; and a report has been written viich contains recorrendations on hcw potential future releases can be better anticipated and thereby prevented.
b.
Manase=ent will review the report centioned in a. above and make deter =inations of which reco==endations will be i=ple=ented.
October 9-12 Ic=ediate actions were taken as previously describec to protect per-sonnel and deter =ine levels of conta=ination; and, the two s=all leaks that were previously described were discovered and repaired.
Plant =anagement also had the follouing practices imple=ented on a te=porary basis to further protect any personnel desiring to enter the 231-foot level of the Auxilicry Euilding:
The Shif t Supervisor's per=ission had to be obtained before any a.
individual entered the 281-foot level.
b.
Any individual with per=ission to enter the 2Sl-foot level had to wear the appropriate anti-contamination clothing and carry a respirator.
. It was further ordered by plant management that additional conitors be placed throughout the 281-f oot level on a tecporary basis in an attempt to detect anv potential future releases as quickly as possible so that the source of a potential release could be located before the radioactive caterial decayed. It is also intended to use the present shutdown period to thoroughly examine the Waste Evaporator Syste= for possible leaks.
All of the above-described temporary practices for the October 9-10 incident were continued until canagement confidence in the control of the unplanned releases had been regained.
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