ML19254C744
| ML19254C744 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/10/1979 |
| From: | NORTHEAST UTILITIES |
| To: | |
| Shared Package | |
| ML19254C738 | List: |
| References | |
| RO-50-336-79-01, RO-50-336-79-1, NUDOCS 7910170298 | |
| Download: ML19254C744 (2) | |
Text
,j...
Faciltiy:
Millstone fluclear Power Station Report liumber:
ETS-f1R/50-245/50-336/79-01 Report Date:
October 10, 1979 Occurrence Date:
August 24, 1979 DESCRIPTIOt 0F GCCU!mE"CE:
The following level of Ag-llom activity was observed in the third quarter sample of oysters from within 500 feet of the discharge and this exceeded the control stations average Ag-110m activity by greater than a factor of ten.
Analysis Confirmation Rescits Location Report Date Date (oCi/g)
Control Stations - Average of Giants ileck and Goldan Spur 9/18 10/1 0.01 1 0.01 Witb{
500 feet of discharge 9/18 10/1 1.01 C.1 PLANT OPERATING CCNDITIClS PRIOR TO OCCURREI:CE:
Millstone Unit 1 - Operating at close to 100% power except for a refueling shutdown from April 28 through June 28.
Millstcne Unit 2 - After a refueling outage ending on May 23 and low pcwer tests, operating at close to 100% power.
CAUSE OF OCCURREi;CE:
flatural oysters do not exist within 500 feet of the discharge.
TMvertheless, oyster trays were located in the discharge channel (quarry cut) and sampled since 1974.
However, with the start-up of Unit 2 in late 1975, the added flow thrcugh the quarry cut proved to be too great to maintain the trays at this location. Thus, no technical specification samples could ba obtained frca 1976 through 1978.
In the spring of 1979 a less turbulent area in the quarry cut was discovered v;hich was suitable for locating oysters trays.
Oyster samples have been located there since the second quarter of 1979.
Due to the location of this sample within the boundaries of the cuarry and thus without any near-field dilution factors, and due to slight increases in plant liquid discharges as a result af the refueling outages, the third quarter oyster sample showed plant related levels of Ag-llCm, CO-53 (0.06 pC1/ga) and C0-60 (0.07 pCi/ga).
Only the Ag-llom was 10 times the background level.
I157 182 7 910170 e2 7 I 3
s
- ju. -
CORRECTIVE ACTION:
The Apprndix I Technical Specifications will re'sult in specification of more realistic sampling locations in keeping with natural availability of sheilfish and food pathways to man. These have been submitted to the URC.
DOSE CONSEQUENCE:
Although natural oysters do not exist at or within the sample lccation, a dose calculation (Reg. Guide 1.109 methods) was performed, assuming an individual could have consumed shellfish having the Ag-110m, Co-53 and Co-60 concentrations as observed for the period of a whole year.
This results in a calculated dase to the critical organ, which in this case is the gastrointestinal tract - Icwer large intestine, of 0.3 milliren/ year.
This is a small fraction (0.0025) of the natural background radiation exposure (120 milliren) to which this ind!ndual is normally exposed.
Thus the dose consequence of this event is insignificant.
This reporting requirement is conservatively designed.
Oatside of the quarry, the plant discharges are rapidly diluted by the Long Island Sound to belcw detectab!c level s.
Thus detectable concentrations cf radioactivity from the station
- are not present at locatic " where shellfish naturally exist.
The monitoring program a: t'ese locations verifies this.
I157 083 e
-