ML19210A229

Nonroutine 10-Day Rept 75-03 Re Inadvertent Sporadic Radiation Releases on 750626.Caused by Malfunctioning Evaporators While Adding Water to Coolant Bleed Tanks & Makeup Tanks

ML19210A229
Person / Time
Site:	Three Mile Island
Issue date:	07/03/1975
From:	METROPOLITAN EDISON CO.
To:
Shared Package
ML19210A227	List: ML19210A226 ML19210A229 ML19210A230
References
75-03, 75-3, NUDOCS 7910240941
Download: ML19210A229 (2)

Text

.Non-Routine 10-Day Report 75-03 Report of an Ucplanned Release cf Radioactive Material Occurring en June 26, 1975 rescription of Occurrence On June 26, between the hours cf v227 and 1529 (thirteen (13) hcurs and two (2) minutes) inadvertant sporadic releases of radicactive material occurred while adding vater to the =akeup tank and the reactor coolant bleed tanks. The tetal time of the teleases was seven (7) hcurs and six (6) minutes. The activity released was lev, no alert or alar ccnditionr en the Radiation Monitoring Syste= occurred at any time during the releases.

Therefere the releases were not discovered until the routine shift check cf r the Radiaticn Monitoring System Strip Chart Recorders. Upen investigation it was deter:1 red that the releases tera coincident with the additicn of water to the =axeup tank or the reactor c aelant bleed tanks. It is postulated that the releases cecurred frc= cne of the evaporators which were, at the time of the release, shutdo in and valved into the radicactive gas vent header system. The addition of water to the tanks caused a pressure surge which was subsequently transmitted to the shutdcun evaporaters which, in turn, leaked the radicactive gas to the Auxiliary Building Ventilaticn " 'snst System. After discovery of the releases, the evaporators were isclated frc=

the vent header system and during si=ilar =akeup operaticns, no further releases occurred.

Apparent Cause of the Occurrence Ecuipment =alfunction is the apparent cause of the cecurrence in that leaks exist in either the Miscellaneous Waste Evaporatcr, or the associated piping.

Analysis of Occurrence For the folleving reasons it is believed that the unplanned release of radio-active =aterial en the 26th cf June did not endanger either the health cr safety of the public.

a.None of the li=its in the TMI-l Technical Specificatiens were exceeded.b.Ncne of the maximum permissible concentration litits for ncn-radiation verkers 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 for radiatien workers specified in 10 CFR 20.

Corrective Action I==ediate corrective action as described above was taken to ter=inate the rele as e.

To determine the exact location of the leak, the evaporater vill be purged and leak tested.

It should be noted that due to a similar release (Non-Routine Repcrt #75-02) the Inscellaneous Waste Evaporator has previcusly been leak tested and one significant leak determined and repaired. Ecvever, in the

\gg4 C .process of starting up and shutting devn the evaporater since that time, another source of leakage has apparently developed.

Failure Data Not Applicable Release Data Note: In no case did any ce=ber of the public or any statien or contractor personnel receive a radiatien dose near the applicable limit; given in 10 CFR 20.

The total release ceasisted of 3 97 Curies of predccinantly (>95%) Xe-133, based en Rad! tien Monitoring System S~., rip Chart Recordings aum sarples of the evaporator gas space and vent header system. The =aximu= instantaneous noble gas release fate during the thirteen hcur and tvc cinute peried was 1.16 x lo, s 3 5 n /sec.=3/sec. which is below the Technical Specificaticn limit of 1.2 x 10 The average release rate for the seven hour and six minute period of the release was h.30 x 102 =3/sec. The 2h hour averaga concentration in the E evaporator cubicle was calculated to be 1.22 x 10 VCi/cc (based en the cumulative effect of all the releases), a facter of h07 times the weighted unrestricted area MPC of 3 x 10-7 pci/ce. There were no personnel e::posures a involved in the release, since there vere no operational or maintenance functions associated with the Miscellaneous Waste Evaporator during the fourteen hour period of the releases. Hcvever, based on the ma.:icum concentration in the cubicle, personnel exposures of up to 32 5 minutes veuld be allevable without exceeding the restricted area MPC for radiation workers as defined in 10 CFR 20.

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