ML20137D556

Aerial Radiological Survey of Byron Station & Surrounding Area,Apr 1985

ML20137D556
Person / Time
Site:	Byron
Issue date:	07/31/1985
From:	Stobie G, Tipton W EG&G, INC.
To:	NRC
References
EGG-10282-1083, UC-41, NUDOCS 8601170027
Download: ML20137D556 (16)

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'O f,kEGsc THE ENERGYMEASUREMENTS lll }l SENSING LABORATORY l

EGG-10282-1083 U C-41 OPERATED FOR THE U.S.

lO JULY 1985 DEPARTMENT OF ENERGY BY EG&G/EM O

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b>a 7 O A O l If the winduw, a-b,is placed where gamma rays The gamma energy spectra shown in Figures 4 from a man-made emitter would occur in the spec-and 5 (from the reactor area and immediately trum, the result of Equation 4 could be expected north of the reactor area) illustrate that only ,J to increase over the constant value. This equation natural gammas exist there but in different quan-is routinely applied in the data reduction sof tware tities. The reactor area spectrum has smaller K-l when a search is made for specific isotopes. 40, Bi-214, and Tl-208 peaks than does the area in general, when a search is made f or an unknown or non-specific gamma emitter, a and b are set to An anomaly was found over the Farmers' Co-Op in O ?8 kev and 1400 kev, respectively; this range the town of Byron. An examination of the net includes most of the long-lived gammas from spectrum (anomaly spectrum minus a neighboring man-made isotopes. The upper limit of the back-spectrum) showed an excess of K-40 (Figure 6). ground window, c,is set at 3016 kev. This window The K-40 is probably contained in the many tons arrangement is called the man-made gross count of fertilizer stored there. (MMGC) ratio. O" Plots of the MMGC were produced routinely in the post-flight data evaluations during the Byron 4.2 Exposure Rates From Airborne survey. Radon Daughters During the aerial survey, the computed back-9 "" 9 * "* * " ""*' ' ( * * ' ' * ^) 4*0 RESULTS radon contributiens) varied over a range from S60 to 980 cps. Since the aircraft and cosmic f ractions of 4.1 Exposure Rate Contour Map background are about 500 cps, the radon contri-The principal result obtained from the gamma bution ranges from 60 cps to 480 cps at the 300 ft survey of the Byron Station is the exposure rate survey altitude. These count rates imply expo-contourmap(Figure 3)of the260-square-kilometer sures from airborne radon at the grot.nd level of ,U (100-square-mile) area surrounding the Station, fromlessthan0.1 R/hto0.3 R/h.The uncertainty The map represents the measured terrestrial is about 50 percent of these values. gamma exposure rate plus an estimated cosmic component * (3.8 R/h) at 1 meter above the earth's surface. The highly variable airborne radon 4.3 Man-Made Gamma Emitters daughter component is not included. The MMGC (discussed in Section 3.2) was used The contour map was composed from approxi-to search the Byron aerial data for man-made mately 47,000 data points, each representing gamma emitters. None were found above the about 0.6 hectares (1.4 acres). Each data point is minimum detectable activity of about 0.1 Ci/m2 composed of a 256-channel gamma energy spec-for a large-area source or about 4 mci for a point tr, n,a pressure and a temperature measurement, source on the ground surface. The minimum C and measured spatial coordinates (altitude and activity or source intensity that can be found by two transponder distances), the MMGC method is limited primarily by the aerial system counting statistics. The exposures at 1 m above the ground, shown on the map (Figure 3), range from a low of 6 R/h in the vicinity of the reactor buildings and over the Rock River to 12 R/h over some of the farmland. 4A Ground-Based Measurements g' A more detailed contour map (not shown) indi-cates that exposure levels around the reactor and Itn chamber measurements and soil samples over the Rock River are as low as 5 R/h. Note that were collected at four sites within the survey these exposure values include a cosmic contribu-boundaries during the aerial survey. The site tion of 3.8 R/h. While the cosmic component is lo':ations are labeled in Figure 3. The soil samples quite uniform, the varying terrestrial component were dried and counted on a calibrated gamma nf (from K-40, the U-238 series, and the Th-232 spectrometer in the laboratory. The "in situ" series) causes most of the changes throughout exposures were computed from the primary iso-i the survey area. topic concentrations in the soil samples 5 and 0 Ds !O ,y . y,,; _ ;,,,. ;. s'__h TC D. j g _ Cl/ 8 D D ), p, y. :.' l~~'.. C' s - g,y z p v - E r } T C': I* C. O b; h-l % C e-E g~ a'o. \\ -; w <s; o o 9 ,4 B' ',g ^^* a C l [ O. Dj D o TC ' R e -Q gg C ( D cp'! :. "k 7 m g N. ..x 1 r ,D N C D f ) se x.

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SURVEVBOUN'DdRYT DATE Of diiUT ~ ~~~ CONVERSION SCALE @ GROUND SAMPLE O MEASUREMENTS EXPOSURE RATE AT 1 ISETER LETTER ASOVE GROUND LASEL LEVEL (pR/h)* LOCATION DIAGR AM A 5.0 - 6.0. B 6.0 - 8.0 0

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90 ~.eters (3ms feet). A cosmic IL compownt of 3.8 pR/h has bsen added to the measured Q terrestrial component. Figure 3. TOTAL G AMMA EXPOSURE RA TE CONTOURS FROM THE APRIL 1985 SURVEY OF THE BYRON S TA TION AND SURROUNDING AREA O 9 o n se f ..gy , ' < <,, '.. ;-FARM C. (r ) jj [,m ,o l ' r{C A kd J C /. J 7 g(4 - .g h Wr gB lr

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c' t. a ], ~' . h A. '(, g r. Q h ~ l g DYE OF ~676~~ -1 TME I ~ ^ RVEY A VJa ; CONVERSION SCALE l h GROUNDSAMPLE MEASUREMENTS gu LocAfton otAGRA80 4 l 3 I URVEY 4 OCATIO IL D Figure 3. TOTAL GAMMA EXPOSURE RATE CONTOURS FROM THE APRIL 1985 SURVEY OF THE BYRON STATION AND l SURROUNDING AREA 9 +3000.0 +3000.0 8"Bi 0.61 MeV j,4[y,y +2400 0 +2400.0 2 = 0.1 _a j +1800.0 8"B' +1800.0 x0.1 -g y g h +1200.0 x1.0

rue, h +1200.0 1.46 MeV

) h 8"Bi "Tl U6 MeV mn o +600 0-O +600.0 x1.0 0 2.62 MeV o L ~ s +.0 +0 g +.0 +5 1.0 1.5 2.0 2IS 3.0 +0 +5 150 1.5 2IO 25 5 3.0 ~ d ENERGY (MeV) ENERGY (Me!) Fleure 6. TYPICAL GAMMA ENERGY SPECTRUM OVER Figure s. GAMMA ENERGYSPECTRUM OVER THE AREA THE BYRON STATION SURVEY AREA . LUST NORTH OF THE BYRON STATION included the effect of soll moisture.s The expo-

3. Since only a limited number of soil samples g

J sure values are compared with the ion chamber were taken, statistical deviations are significant. measurements and thE, aerial measurements in Table 2. These exposure values represent the

4. The ground cover reduces the computed terrestrial plus the cosmic components only, isotopic exposure by as much as 5 percent.

A special effort to compare aerial and ground The isotopic and ion chamber measurements fall measurements was made at site 4. The serial ) within the aerial measurement interval at each site system flew slowly overhead at 30,60, and 91-except for site 3 where the aerial eneasurement is meter (100,200, and 300-ft) altitudes while ion about 1 uR/h higher than the ion chamber and soil chamber measurements were made. Table 3 com-sample measurements. There are several contri-pares an experimental estimate of K-40, U-238, butors to differences among the measurement and Th-232 f rom the serial data to the soil sample methods: measurement as well as exposures from the ion chamber and aerial methods.

1. The aerial data were not taken at exactly the same places and times as the ground data, The aerial and ground-based expcsure measure-except for site 4.

ments in Tables 2 and 3 agree within the limits of the measurements' errors. The aerial measure-

2. The aerial system " sees" a larger area (6 to 10 ment of U-238, Th-232, and K-40 is less th'n the 3

hectares) than does the g round system (about soil sample measurement by about 10 percent 1 hectare). but, nonetheless, it is reasonable. O-e 10 1 e 4 +150 0 } +120.0 G! I +90.0 4 i COMPTON "K 5 CONTINUUM 1.46 MeV / trg + 60.0-N 5o +30.0 O +0 ~ +0 + 50 1.0 1.5 2.0 2.5 3.0 ENERGY (MeV) Figure s. POTASSIUM-40 GAMMA ENERGYSPECTRUM OBTAINED OVER THE FARMERS' CO-OP IN B YRON, ILLINOIS 3 Table 2. Comparison of Aerial and Ground Based Measurements Dry Sollisotopic Composition Exposure Rate (seR/h) Soil Moisture U-238 Th 232 Cs 137 K-40 lon Site t (%) (ppm) (ppm) (pCl/g) (pCl/g) Isotopic 8 Chamber 3 Aerial 1 17.2 1.5 2.8 0.3 9.2 0.7 0.29 0.02 15.7 0.8 10.2 0.6 9.7 0.5 8-10 2 16.9 1.1 2.7 0.2 8.7 0.2 0.24 0.01 16.2 0.7 10.0 0.5 10.0 0.5 8 -10 D-3 11.5 1.0 1.3 0.2 4.6 0.7 0.30 0.04 9.8 1.2 7.4 0.4 7.8 0.5 8 -10 4 18.9 1.5 3.5 0.2 11.C 0.6 0.35 0.04 17.5 0.7 11.3 0.5 10620.5 10 -12 ' The site locations are shown in Figure 3. 8 The exposure rate from the isotopic concentrations was computed using Beck's conversion.s The exposure rate computed from the isotopic concentrations includes the effect of soil moisture and a cosmic component of 3.8 pR/h. + ) 3 The measr ed airborne radon esposure rate. 0.3 pR/h. has been subtracted from the ton chamber measurements at sites 3 and 4 where a redon es'.imate was available from the aerial data. O i i i p 1 11 0 O Table 3. Detailed Comparison of Aerial and Ground-Based Measurements at Site 4 9 Ground-Based Aerial Measurement Measurement 1 U-238 3.5 10.2 ppm 3.2 ppm Th-232 11.5 i 0.6 ppm 10.2 ppm Cs-137 0.3510.04 pCl/g 6 K-40 17.5 0.7 pCi/g 16.0 ppm Isotopic Exposure 3 11.3 0.5 R/h 10.5 R/h lon Chamber Exposure 4 10.7 0.5 R/h Aerial Total Count 10.5 1.0 R/h Exposure O ' The errors in this experimentalisotopic extraction method are being evaluated and are probably on the order of the soil sample method. 8 The absolute isotopic extraction routine does not include Cs-137 for the aerial data. 8 Exposures include the terrestrial and cosmic components only. Exposures also include the effect of soil moisture.

• A radon exposure estimate (from the aerial data) of 0.3 R/h has been subtracted from the ion chamber exposure measurement.

O D g m w/ 9 12 ,a .__________m l l ) l l-REFERENCES I l 1. Quam, W. and Engberg, K. October 1978. Low Background Ge(Li) Detector with Anticoincidence Nel Annulus. Report No. EGG-1183-2326. Santa Barbara, CA: EG&G/EM. i 2. Low Background Ge(LI) Detector Gamma-Ray Spectroscopy System with Sample Changer. Report l No. EGG-1183-2383. Santa Barbara, CA: EG&G/EM. 3. Boyns, P.K. July 1976. The Aerial Radiological Measuring System (ARMS): Systems, Procedures a7d Sensitivity. Report No. EGG-1183-1691. Las Vegas, NV: EG&G/EM. 4. " Environmental Radiation Measurements." December 1976. NCRP Report No. 50. p. 30. Washington, D.C.: National Council on Radiation and Measurements. 5. Beck, H.L. et al. September 1972. In Situ Ge(LI) and Nal(Tl) Gamma-Ray Spectrometry. Report No. ) HASL 258. TID-4500. Health and Safety Laboratory: U.S. Atomic Energy Commission. 6. Caroll, T.R. November 1981. " Airborne Soil Moisture Measurement Using Natural Terrestrial Gamma Radiation." Soll Science. Vol.132, No. 5. b D D 3 o l l) 13 i DISTRIBUTION NRC/HQ LBL L. K. Cohen (1) H. A. Wollenberg (1) E.D. Weinstein (2) NRC/ REGION lli EG&G/EM L. Kers (7) H.M. Borella, SBO (2) P. K. Boyns, LVAO (1) Z.G. Burson, LVAO (1) J. F. Doyle, LVAO (1) DOE /ONS L. A. Franks, SBO (1) L.J. Deal (5) A. E. Fritzsche, LVAO (1) R. E. Lounsbury, WAMD (4) R. L. Lynn, SBO (1) DOE /OMA T. C. Maguire, WAMD (1) J. A. Michael, LVAO (1) J. C. Dobes (1) R. A. Mohr, SBO (1) L. G. Sasso, LVAO (1) G. P. Stobie, LVAO l1) T. P. Stuart, LVAO (1) DOE / TIC W. J. Tipton, LVAO (1) W.D. Matheny (2) G.G. Widner, LVAO (1) P. H. Zavattaro, LVAO (1) DOE /NV G.C. Allen (1) LIBRARIES H. F. Hahn, EMO (1) D. A. Nowack (1) AMO (10) G.M. Plummer (1) Archives (1) D.C. Quenell (1) Senta Barbara (1) BYRON STATION BYRON. Ill ' 'OIS EGG-10284 -1083 DATE OF SURVF.: APRIL 1985 DATE OF REPORT. JULY 1985 V _ ___