ML19276H350

RO 50-289/74-01 on 741006,08 & 09-10:unplanned Radioactive Releases.Caused by Valve Leak,Faulty Installation of Loop Seal Plug,Ruptured Disc & Loose Plug.Valve Replaced,Loop Seal Plug Reinstalled & Leaks Repaired

ML19276H350
Person / Time
Site:	Three Mile Island
Issue date:	10/24/1974
From:	METROPOLITAN EDISON CO.
To:
Shared Package
ML19276H306	List: ML19276H316 ML19276H319 ML19276H325 ML19276H328 ML19276H334 ML19276H336 ML19276H341 ML19276H343 ML19276H350 ML19276H358
References
NUDOCS 7910160689
Download: ML19276H350 (4)

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ENCLOSURE (1)

Metropolitan Edison Company b T.arce Mile Isbnd Nucicar Station, Unit 1 (2I-1) i 6

Docket No. 50-289 Operating License No. *DPR-50

• Honroutine 10-Day Report '

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Report of Three Unplanned Radioactive Releases Occurring on October 6, 8, and 9-10,1974

1. Description of Occurrences: '

10ctober 6 -

Between the hours of 0145 and 0415 (2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />) on October 6, 1974, an unplanned release of radioactive material occurred in the Reactor Coolant (RC) Waste Evaporator Room of the Auxiliary Building due to a leak in theSystem.

Evaporator Vacuum Pump Discharge Diaphragm Valve of the RC Waste 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" alarm was received in the Control Room; and the higher-than-normal reading was subsequently detected by a control room operator during a periodic check of the instru=ent.

A similar release occurred 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-A8 monitor and no " alert" alarm was received, and the higher-than-normal reading was subsequently detected b~ a control room operator -

during a periodic check of the instrument. -

_ 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 material occurred in the RC Waste Evaporator Room of the Auxiliary Building due 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 Room from the Auxiliary Building Exhaust Monitor (RM-A6) .

_0ctober 9-10

!df 9-10, f19 4,26 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 an unplanned release of radioactive material occurred in the Auxiliary Building.

Both an alert-1cyc1 and then a high-level radiation alarm Honitor (RM-A6) .were received in the control Room from the Auxiliary Building Ex

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,v .i v In all of the above-cescribed occurrences, as soon aa the higher-

.than-normal readings were detceted, the Auxiliary Building was ordered evacuated; personnel in the icmediate area of each release underwent decontamination and were checked for ingested radioactive materini and dosage received; appropriate corrective actions were taken to secure the releases; and Health Physics personnel proceeded to the affected area to collect air and smear sampics for analysis.

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2. Apparent Cause of Occurrences: - -

October 6 .

Component failure was the apparent cause of the unplanned releases of October 6, in that the Vacuum Pu=p Discharge Diaphragm Valve of the RC Waste Evaporator developed a leak.

October 8 .

Personnel error in the it. stalling of a plug in the loop seal of the RC Waste Evaporator Storags Tank was the apparent cause of the unplanned release of October 8. A similar series of unplanned- releases involving tiiis loop seal occurred on Septe=ber 5, 6, and 7,1974 (Nonroutine 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 once again made operational; and it was the improper installation of the plug that permitted noble gases to escape from the vent header, through the loop seal, and into the RC Waste Evaporator Room.

October 9-10 The release was suspected to have resulted from a leak.or leaks in the Waste Evaporator Sys tem. 'No small leaks were subsequently dis-covered: one was due to a ruptured disc on the RC Waste Evaporator Feed Tank and the other was due to a loose plug on the loop seal of the Feed Tank. It is believed that the ruptured disc was due to the l

ins 3cquate design of the Uas te Evaporator Faed Tank loop seal (refer- :

ence Nonroutine 10-Day Report 74-01) in that if the seal did not have to be plugged, the disc cost likely would not have ruptured. The loose plug on the loop seal is believed to be due to personnel error in that the installed plug was not adequately tightened.

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3. Analysis of Occurrences: -- -

For the follcuing 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 Specifi a ons e exceeded. .

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b. ' None of the Ibxi=cm Permissable Concentration limits for non-radiation workers listed in 10 CFR 20 were exceeded at the site

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

4. Corrective Action: .

October 6 .

Ic=ediate actions were taken as previously described to protcet per-sonnel and deter =ine levels of contamination. As a long-term corrective action to prevent future releases, the leaking valve was replaced. .

October 8 Immediate actions were taken as previously described to protect per-sonnel and determine levels of contamination. Also the loop seal plug was re-installed. As a long-term corrective action to prevent future releases, a comprehensive program with the following major provisions was instituted by plant management.

a. Extra watch standers were assigned on a tecporary basis to monitor those parameters which might provide an insight into the condi-tions which are likely to precede an unplanned release; and a report has been written which contains recoc=endations on how pot'ential future releases can be better anticipated and thereby

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pr'evented.

b. Management will review the report centioned in a. above and make determinations of which recommendations will be implacented. .

October 9-10 Ic=ediate actions were taken as previously described to protect per-sonnel and determine levels of contamination; and, the two small leaks that were previously described were discovered and repaired.

Plant management also had the following practices imple=ented on a temporary basis to further protect any personnel desiring to enter the 281-foot level of the Auxiliary Building:

a. The ShiIt Supervisor's permission had to be obtai 3c,d before any individual entered the 281-foot level.

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'b. Any individ'ual with permission to enter the 281-foot icv'el F ad to wear the appropriate anti-ccatamination clothing and carry a respirator.

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It va's further ordered by plant managecent that additional conitors be placed throughout the 281-foot 1cyc1 on a te=porary basis in an attempt to detect any potential future relcas.cs as quickly as possibic so that the source of a potential release could be located before the radioactive material decayed. It is also intended to use the present shutdown period to thoroughly examine the Waste Evaporat.or System for possible leaks -

All. .of the above-described te=porary practices for the October 9-10

, incident were continued until management confidence in the control of the unplanned releases had_been regained. .

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