05000369/LER-1985-021, :on 850605,personnel Overexposure Occurred. Calculations Indicate Dose of 10.6 Rems to Skin & 0.03 Rem to Whole Body.Control & Disposal of Protective Clothing Revised to Prevent Recurrence of Incident

:on 850605,personnel Overexposure Occurred. Calculations Indicate Dose of 10.6 Rems to Skin & 0.03 Rem to Whole Body.Control & Disposal of Protective Clothing Revised to Prevent Recurrence of Incident

ML20133J034
Person / Time
Site:	McGuire
Issue date:	08/02/1985
From:	Day J DUKE POWER CO.
To:
Shared Package
ML20133J026	List: 05000369/LER-1985-021, :on 850605,personnel Overexposure Occurred. Calculations Indicate Dose of 10.6 Rems to Skin & 0.03 Rem to Whole Body.Control & Disposal of Protective Clothing Revised to Prevent Recurrence of Incident 05000369/LER-1985-021-01, Forwards LER 85-021-01 Re Personnel Exposure,Initially Determined to Be Overexposure.Revised Calculation Indicates No Overexposure Occurred
References
LER-85-021, LER-85-21, NUDOCS 8508090626
Download: ML20133J034 (4)

LER-1985-021, on 850605,personnel Overexposure Occurred. Calculations Indicate Dose of 10.6 Rems to Skin & 0.03 Rem to Whole Body.Control & Disposal of Protective Clothing Revised to Prevent Recurrence of Incident

Event date:
Report date:
3691985021R00 - NRC Website

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NRC Form 300 U.S. NUCLE 173 KELULAT@2V COMM13SICN 3 838 APPROVED OMS NO 3160 4 104

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J.".$YR ACT (Lem.t to 74Jo speces a e. sooro=>eere y rdreen snap e space ryoe.,,trea I,aes/ (16' On June 5, 1985, a radioactive particle was discovered under the upper left arm of a technician involved in steam generator tube plugging who was exiting containment.

The particle was removed and later analyzed.

Initial dose calculations indicated a dose of 10.6 Rem to the skin and 0.030 Rem to the whole body, which represents an overexposure to the skin for the quarter pursuant to 10 CFR 20.101a. A review of methodology and assumptions of tne initial dose calculation has resulted in revised dose calculations which yield lower values for the dose which do not represent an overexposure.

The control and disposal of all protective clothing has been revised to prevent this type of incident from reoccurring.

The original calculation was based upon conservative methodology and assumptions about the exposure. The revised calculation is based upon more realistic assumptions. The health of the technician and the safety of the plant were unaffected by this incident.

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NXC Form 364A U S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION apeRO <EO oms NO 3 iso-oio4 EXPIRES 8/3185 FJ.CILtTV NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

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On June 5,1985 at 2200, a radioactive particle was discovered under the upper left arm of a technician who had been assisting in the plugging of a steam generator tube and had partially entered (head and arms) the steam generator.

The particle was removed and analyzed. The particle was found to have 1.219 micro Curies of Cobalt-60. On June 10, 1985, the dose was calculated to be 10.6 Rem to the skin and 0.030 Rem to the whole body. This is the dose at 7 mg/cm(2) skin depth averaged over 1 cm(2) and assumes contact with the skin for the two full hours of use of the protective clothing.

Subsequently, the dose was recalculated for more realistic assumptions, and as being delivered averaged over the dermal layer, as well as at 7 mg/cm(2).

Changing any single parameter to a more realistic value (time, exposure depth, or movement) yields a value that is not an overexposure.

Below are the results of several calculations using more realistic assumptions:

Time Skin Area Skin Depth Dose (hrs) cm (2) mg/cm(2)

Rem Literal worst case 2

1 at 7 10.6 4-125 mg/cm(2) 2 1

4-125 1.9 4-40 mg/cm(2) 2 1

4-40 5.3 Statistically likely 1

1 at 7 5.3 Most likely transfer

.5 1

at 7 2.65 1 cm movement of particle on skin 2

2 at 7 5.3 Proposed 10 CFR 20 2

10 at 7 1.06 Calculating the dose at 7 mg/cm(2) is at a thin slice location and represents a two dimensional calculation.

It is more realistic to calculate dose over a volume (three dimensional).

The time of exposure is also in question. Two hours is the maximum possible time of exposure. This conservatively assumes the particle was in the protective clothing, transferred immediately when the technician put on the protective clothing, and did not move once transferred. Since no particle motion was assumed, the dose was calculated over one square centimeter; minimal particle motion (one centimeter) would have distributed the dose as not to involve an overexposure.

Based on the above results, Duke Power concludes that no overexposure occurred.

NRC FORV 344A

1 NRC Form 364A U S. NUCLEGR REGULOTOQV COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO 3150-0104 EXPIRES 8711 @5 FACILITU NAME (Il DOCKET NUMBER (21 LER NUMBER 163 PAGE13)

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.Beginning in April, 1985 personnel contaminations occurred as a result of micro-scopic particles containing only Cobalt-60. At this time an investigation was started to determine the source of the Cobalt-60. The following possibilities were evaluated:

1.

All pure Cobalt-60 sources on site were lead tested but no sources were found to be leaking.

2.

All new steel on site used in construction was surveyed but no contaminated material was found.

3.

Detailed grid surveys of the plant were performed. No activity was above background.

4.

Surveys using maslin cloth (oil cloth) were performed. All activity was below background.

It is believed that the Cobalt-60 is coming from activated stellite in the Reactor Coolant System. Due to leakage or maintenance on primary system components the activated stellite (Cobalt 60) is picked up on the protective clothing. During laundering of protective clothing most contamination is removed. However, the Cobalt-60 particles are insoluble and can be suspended in the wash water and then redeposited on the protective clothing.

Corrective Action

The following corrective actions were initiated after the original personnel contaminations:

Extensive frisking (80 man-hours per day) of all protective clothing.

Disposal of all cloth coveralls and hoods. New coveralls and hoods purchased. Prior to mass disposal only protective clothing used in high contamination jobs had been disposed of as radwaste.

Increased the number of personnel frisking stations within the plant.

Frisking the inside of protective clothing by purchasing special (yellow) coveralls to be worn in very high contamination and high temperature areas.

More use of plastic and disposable protective clothing where possible.

Requisition of an automatic laundry monitor to eliminate technician error.

The individual was removed from furhter activities involving radiation exposure for the remainder of the quarther. The incidnet has been reviewed with appropriate personnel at other Duke stations.

NmC FORM 366A E9 03)

r NRC Form 364A U.S NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AerRovEo ous NO 3 iso-oio4 E X PIR E S 8,11 '85 F#.CILITY NAME (1)

DOCKET NUM8ER (2)

LER NUMBER (6)

PAGE (3)

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Safety Analysis

The exposure had no effect on any safety related system and the health and safety of the public were not affected.

The exposure of the technician was calculated with realistic assumptions and did not involve an overexposure. The health of the tecnician was not affected by this event.

i NRC FORv Josa IS 833