ML20083C242

Provides Response to 910910 Request for Addl Info Re Review of SAR Update Request.Result Compared W/Data from NUREG-0851 for Ar-41 Total Body Dose

ML20083C242
Person / Time
Site:	U.S. Geological Survey
Issue date:	09/19/1991
From:	Danni Smith INTERIOR, DEPT. OF, GEOLOGICAL SURVEY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-NUREG-0851, RTR-NUREG-851 NUDOCS 9109260104
Download: ML20083C242 (11)

Text

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' *s United States Department of the Interior un-  ?

M-w GEOLOGICAL SURVEY BOX 25045 M.S. 973 Y "s i

DENVER FEDERAL CENTER DENVER, COLORADO 80225 W WlPLY RtiIR 10.

BRANCH OF GEOCHEMISTRY September 19, 1991 Docket 50-274 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Sirs:

This is in response to your request for additional information dated September 10, 1991, concerning the review of our Safety Analysis Report update request.

Our original request dated August 7, 1991 was conservative since it assumed that the Ar-41 cloud presented an infinite radius, hemispherical source. A more realistic approach is to evaluate the USGS reactor room as an equivalent finite-radius hemispherical source. The reactor room dimensions are 21 feet by 35.5 feet with a height of 16.5 feet. This gives a volume of 12,300 cubic feet.

A hemisphere with an equivalent volume would have a radius of 18.04 feet (550 cm). This 550 cm radius hemisphere will be used to approximate the USGS reactor room configuration.

The gamma flux at the center of the finite hecisphere can be compared to the gamma flux at the center of an infinite hemisphere by appropriate evaluate of the following equation for symmetric spherical sources:

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l g g c-9 s i- ew (Ref: Principles of Radiation Protection, Morgan and Turner, John Wiley and Sons, Inc., 1967, p.285)

Evaluating this ratio for a radius of 550 cm and an attenuation coefficient of 5.6 x 10'5 1/cm gives a flux ratio of 33. (An' air density of 0.001116 g/cm3 is assumed for this altitude.) Thus, the 910o260104 910919 '

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whole body dose received from a uniform Ar-41 cloud in the reactor room would be approximately a factor of 33 below the dose received from an infinite hemispherical source of argon.

1. Exoosure to Reactor Staff and other Radiation Workers:

Evaluation of_ potential doses to the USGS staff assumes that the typical Ar-41 concentration in the reactor room during full power operation is 4.35 x 10~6 uCi/ml. Also assumed is that exposure to an infinite hemisphecical cloud of Ar-41 at the MPC for restricted areas (2 x 10 6 uCi/ml) for 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> per week over 13 weeks would give a whole body dose of 1.25 rom. Further assuming that a staff member typically spends 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> per week in the reactor room during reactor operation gives the following dose evaluation: j Quarterly stay time: 8 X 13 = 104 hours0.0012 days <br />0.0289 hours <br />1.719577e-4 weeks <br />3.9572e-5 months <br /> Dose = (4. 35x10 6 / 2x10) X (104 hrs / 520 hrs) X 1.25 rem /

33 (correction for finite radius).

Dose = 0.0165 rem or 16.5 mrom per quarter This routine exposure is well below the quarterly limit of 1.25 rems given in 100FR20.101. '

Evaluation of the accidental release of a saturated level of Ar-41  !

from the lazy susan assumes that 860 mci is distributed in the reactor room instantaneously and remains in the room for 12 minutes.

The Ar-41 concentration would be 2.46 x 10'3 uci/ml, and this is assumed to be constant during the 12 minute exposure time. Assuming that personnel in the room remain during the entire 12 minute period, the resulting dose would be:

Dose = (2.46x10'3 / 2x10) X (.2 hr / 520 hrs) X 1.25 rem / 33 Dose = 0.0179 rem or 17.9 mrem.

This accidental exposure is well below the quarterly limit of 1.25 i

rems given in 10CFR20.101,

2. Exnnsure to minors:

Exposure of minors during tours of the reactor facility is evaluated :ith the following assumptions:

ar-41 concentration in _ air = 4.35 x 10 6 uCi/ml Stay time = 0.5 hr Continuous exposure at unrestricted area MPC (4 x 10

( uCi/ml) for one year (365 days or 8760 hours0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br />) would give l

a dose of 0.5 rem.

A dose correction factor of 33 is applicable for - the i finite dimensions of the reactor room.

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The resulting dose is given Dose = (4.35x10 by): X (0.5 hr / 8760 hr) X 0.5 rem / 33

/ 4x10' Dose = 9.4 x 10 4 rem or 0.094 mrem.

This calculated dose is about 0.1 mrom and provides good agreement with the typical pocket dosimeter dose recordings of zero. It is also well within the limits of 10CFR20.104.

3. Use of other cases in lazy susan:

Hitrogen gas is frequently used in the lazy susan to reduce Ar-41 production; however, we prefer to not take credit for this potential dose reduction in the hazard analyses.

4. Use of ource cas_in the lazy susan:

Nitrogen gas is frequently used as a purge gas in the lazy susan; however, we prefer to not take credit for this potential dose reduction in the hazard analyses.

5. Small-volume duct exhaust:

The small-volume duct to exhausc air from the reactor room was not installed during the facility construction and is not available for use.

6. Exposure in unrestricted areas:

Evaluation of doses from Ar-41 to personnel in unrestricted areas ~ outside the reactor building - were performed by several methods. The assumed releases were:

Routine: 11.4 Ci per year, distributed over about 200 operating days.

Accident: 0.86 Ci acute release.

Detailed evaluation of the routine argon releases was performed using . the . COMPLY version 1.4 computer program developed -by the Environmental Protection Agency (EPA) (Ref. EPA 520/1-89-002 and - EPA 520/1-89-003). This program was developed to evaluate airborne emissions of radionuclides to the atmosphere and was intended to be applied to certain NRC-licensed faciliti" Using the level 3 evaluation, an estimate of the radiation dose to the receptor is provided after the following data are input:

Radionuclide name Ar-41

. Release rate 11.4 Ci/yr Release height 7 meters Building height 6 meters Distance from source to receptor varies Building width 23 meters l- Wind speed 3.8 m/s Distance to sources of food production 700 meters l

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l Since the Ar-41 hazard is from external exposure, the source of food l production has no bearing on this evaluation.

The COMPLY code determines that a 300 meter dose of 0.059 mrem /yr will result from a yearly release of 11.4 Ci (see attached printout). This result was compared with data from NUREG-0851 for 1.r-41 total body dose. A distance of 300 meters, a wind speed of 3.8 m/s and an E stability class were used for the nomogram. The nomogram gives a dose of (0.0059 mrem /Ci X 11.4 Ci/yr) = 0.067 mrem /yr. (See attached nomogram copy.) Thus, the COMPLY code evaluation agrees quite well with the NUREG-0851 nomogram.

The COMPLY code was rerun for the necrest location in the unrestricted area. This point is along the building wall, approximately 8 meters frou the reactor room exhaust release point.

An annual release of 11.4 Ci of Ar-41 is estimated to give a dose of 7.6 mrem /yr to this nearest location in the unrestricted area. ,

(See attached printout.) Increasing reactor operations such that the annual release of Ar-41 is 25 Ci would result in a dose of 16.7 mrem per year. These levels are well within the 500 mrem annual dose limit per 10CFR20.105(a).

An accidental release of 860 mci from the lazy susan would then similarly result in a possible dose to the nearest location in the unrestricted area of:

(0.86 Ci / 11.4 C1) X 7.6 mrem = 0.57 mrem This dose would be received in less than one hour for a worst case acute release and would be less than the one hour limit of 2 mrem given in 10CFR20.105(b.1).

I hope this response provides the additional information and clarification needed for our Safety Analysis Report revision. Please j contact the Reactor Supervisor, Tim DeBey, if you have further technical questions.

,Sincerel/, f rj l f h

! David B. Smith Reactor Administrator

' Attachments: As stated Copy to: Tim DeBey, MS 424 g Subscribed and affirmed before me this /'Ml day ofib[ .s 1991.

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GEPA A Guide for Determining l Compliance with the Clean Air Act Standards for Radionuclide Emissions from NRC-Licensed and Non-DOE Federal Facilities y

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l-l Unitco States Air And EPA 520:189 003 Environmental Protection Rad:abon October 1989 l ,

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t 9/19/91 . 8:57 b

dO CFR Part 61-

-National Emission Standards

.for: Hazardous Air Pollutants REPORT'ON COMPLIANCE WITH

' T H E ' C L E ,v o nIR ACT LIMITS FOR RADIONUCLIDE EMISSIONS FROM THE COMPLY,CCDE, VERSION 1.4 4

Prepared by:

USGS GSTR DENVER FEDERAL CENTER Tim DeBey (303) 236 4726 l Prepared for:

U.S. Environmental Protection Agency ,

Office of Radiat-ion Programs Washington, D.C. -20460 L

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9/19/91 8:57 GSTR ARGON EVALUATION

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SCREENING LEVEL 3 DATA ENTERED:

Release Rate Nuclide (curies / YEAR)

AR-41 1.140E+01 Release height 7 meters.

Builcing height 6 meters.

The source and receptor are not on the same building.

Distance from the source to the recepter is 300 meters.

Building width 23 meters.

Default mean wind speed not used.

Mean wind speed is 3.80 m/sec.

Distance from the SOURCE to the FARM procucing VEGETABLES is 700 meters.

Distance from the SOURCE to the FARM procucing MILK and MEAT is 700 meters.

NOTES:

Input parameters outside the " normal" range:

l None.

RESULTS.

Effective dose equivalent: 5.9E-02 mrem /yr.

• • • Comply at level 3.

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- 9/19/91 9:04 40'CFR Part-61 National Emission Standards .

'for Hazardous Air Pollutants REPORT ON COMPLIANCE WITH THE CLEAN AIR ACT LIMITS FOR RADIONUCLIDE EMISSIONS FROM THE COMPLY CODE, VERSION 1.4 -r Prepared by:

USGS GSTR DENVER-FEDERAL CENTER Tim.DeSey (303) 236-4726 l

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l U .S . Environmental Protection Agency Office of-Radiation Programs Washington, D.C. 20460' i

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9/19/91 9:04 GSTR ARGON EVALUATION SCREENING LEVEL 3 DATA ENTERED:

Release Rate Nuclide (curies / YEAR)

AR-41 1.140E+01

, Release height 7 meters.

Building height 6 meters.

The source and receptor are not on the same building.

Distance from the source to the receptar is 8 meters.

Building wicth 23 meters.

Default mean Wind speed not used.

Mean wind speed is 3.80 m/sec.

Distance from the SOURCE to the FARM producing VEGETABLES is 700 meters.

Distance from the SOURCE to the FARM procucing M!LK and MEAT is 700 meters.

NOTES:

Input parameters outsice the " ncrmal ' r a nge :

None.

RESULTS:

Effective cose equivalent: 7.6 mrem /yr.

• • • Comply at lovel 3.

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