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 l

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

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

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v BYRON STAT ON i AND SURROUNDING AREA h BYRON, ILLINOIS DATE OF SURVEY: APRIL 1985 o SW488lx'M$or l R  !

O DISCL.\lMER This report was prepared as an account of work sponsored by an agency of the United States Government.

Neither the United States Government nor any agency thereof, nor any of their employees, makes any O

warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usef ulness of anyinformation, apparatus, product,or process disclosed,or represents thatits use would not infringe privdtely owned rights. Reference herein to any specific commercial product, process, or serv!ce by trade name, trademark, manuf acturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States O

Government or any agency thereof.

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i Printed in the United States of America.

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l 5285 Port Royal Road-l Springfield, Virginia 22161 NTIS price codes l

Printed copy: A02 3 Microfiche copy: A01 9:

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EG G-10282-1083 dEGrG ENERGYMEASUREMENTS JULY 1985

4 AN AERIAL RADIOLOGICAL SURVEY OF THE D BYRON STATION AND SURROUNDING AREA BYRON, ILLINOIS D

DATE OF SURVEY: APRIL 1985 D

A. E. Fritzsche Project Scientist ,

'3 REVIEWED BY O

?K) $6-W. J. Tipton$ Assistant Manager Aerial Measurements Operations O

This Document is UNCLASSlFIED O , j lD G. P. Stobie

! Classification Officer C This work was performed by EG&G/EM for the United States Department of Energy, O:? ice of Nuclear Safety, and the United States Nuclear Regulatory Commission under Contract Number D E- AC08-83NV10282.

lO

n-V ABSTRACT O

An aerial gamma survey was conducted over the Byron Station,locatsd 5 kliometers (3 miles) south of Byron, Illinois, during the period 11 A tsll l through 17 Aprii 1985. The survey included a 260-square-kilometer (100-square-mile) area centered on the Station.

A contour map of the terrestrial gamma es. osure rate plus cosmic exposure ret .it the 1-meter level was prepared and verlaid on an aerial photograr.h and a USGS topographic map of the area.The terrestrial plus O cosmic gamma exposure rate ranged from a minimum of 5.0 microroentgens per hour ( R/h) over the Rock River to a maximum of 12pR/h 7 kilometers (4 miles) west of the facility. A machine-aided search of the data showed no man-made gamma emitters in the survey area.

Soil samples and ion chamber measurements were obtained at four locations to support the serial data.

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=O CONTENTS

'O Abstract .. .. . . . . 2 O

v Sections 1.0 Introduction . . . . . . 5 "o 2.0 Survey Equipment and Methods . . . . . . 5 2.1 Aircraf t System . .. . . . . . .. .. 5 2.2 Data Van . . .. . . . . . . ... .. 5 2.3 Ground-Based Measurements . . . . . . . . . ... . 5 6

y 2.4 Byron Survey Method . . . . . . . . ..

3.0 General Data Reduction .. . .. . .. . 7 3.1 Gross Count . .. . . . . ... . . . .... 7 3.2 Spectral Windows . .. .. . . 7 4.0 Results . .. ... .. .. . ... 8

(~) . . .

4.1 Exposure Rate Contour Map . . .. . . .. . 8 4.2 Exposure Rates from Airborne Radon Daughters . . . . 8 4.3 Man-Made Gamma Emitters . . . . . . . . . . . 8 4.4 Ground-Based Measurements . . . . . . .. . 8

!O Figures 0 1 Aerial Gamma Measuring System . . . .. 5 2 Data Reduction Van System . . . 6 3 Total Gamma Exposure Rate Contours from the April 1985 Survey of the Byron Station and Surrounding Area . .. . . . .... 9 q~ 10 4 Typical Gamma Energy Spectrum Over the Byron Station Survey Area .

5 Gamma Energy Spectrum Over the Area just North of the Byron Station . . 10 6 Potassium-40 Gamraa Energy Spectrum Obtained Over the Farmers' Co-Op in Byron, Illinois . . . . . . . . 11 0

3 cO

4 I

O.

Tables I

1 . Byron Survey Parameters 6 Q . . . .. . ...... . ...... . . . . . .

i 2 Comparison of Aerial and Ground-Based Measurements . .. . . ... ... 11 l

l

-3' Detailed Comparison of Aerial and Ground-Based Measurements  ;

at Site 4 . . . . . . . . . . .... . . . ... ... . . . ... .... . .. 12 0I References . . . . . . . .... - -.. . . .. .. .. . . .. . . 13 O-O O.

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1.0 INTRODUCTION

Ao serial gamma survey was conducted from 11 O April through 17 April 1985 over the Byron Station and surrounding area. The survey covered a 260-square-kilometer (100-square-mile) area centered __ g on the Station. The purpose of the survey was to 4"j g% N map the gamma environment of the area sur- n rounding the Station. The survey was performed O at the request of the United States Nuclear Regu-latory Commission.

The Byron reactor was in the proce'ss of being brought to a significant power level when the Figure 1. AERIAL GAMMA MEASURING SYSTEM operation was scrammed on 10 April 1985, the n" day prior to the start of the aerial survey. A significant reactor power level was again achieved Real-time gamma energy spectra, total gamma by 13 April 1985. count rates, and other data were output to a small CRT screen for the system operator.

The Byron facility is located in Ogle County, Illinois, S kilometers (3 miles) south of the town of The aircraf t pilot was g uided over the prog rammed g Byron, Illinois. The Rock River,3 kilometers (2 flight lines by an indicator that derived its signal miles) west of the plant, supplies the cooling from the triangulation of two UHF transponders water. The majority of the land surrounding the on the ground and a master unit in the aircraft.

facility is cultivated and fairly level with 60-meter These position data were also stored by the (200-foot) maximum elevation changes. REDAR.

g Large-area aerial photographic imagery of the v Station was obtained in July 1983 and many 22 De h oblique photographs of the site were taken during the survey. A minicomputer-based system (Figure 2) housed in a van was used during the survey to evciuate the aerial data immediately following each survey 9 *Y* * " *'"* * ** ""

• O 2.0 SURVEY EQUIPMENT AND ware that operates on the survey data stored on METHODS magnetic tape. The system operator can plot b th gamma energy spectra from any portion of 2.1 Aircraf t System the gamma survey and count rate isopleths or A Messerschmitt-Bolkow-Blohm (MBB)80-105 contours of the survey scaled to a map or photo-helicopter was used as the aerial platf orm (Figure graph. In this manner the isotope emitters, their lg~ intensity, and location can be identified.

1). The aircraft carried two detector pods, each l

containing four 10.2 cm x 10.2 cm x 40.6 cm i log-type Nal(Tl) gamma detectors as well as one 10.2 cm x 10.2 cm cylindrical gamma detector. 2.3 Ground-Based Measurements The smaller detector was used to extend the dynamic range if necessary of the large and Exposure rates were measured and soil samples g~

sensitive log-type detectors. obtained at four locations during the Byron survey.

These measurements were made to support the Gam ma signals originating in the Nal(TI) detectors integrity of the aerial results. A Reuter-Stokes were routed to the Radiation and Environmental pressurized ionization chamber was used for Data Acquisition and Recorder (REDAR IV) system each exposure measurement at a 1 meter height q" for conversion and storage on magnetic tape, at the center of a 120-meter (396 ft) diameter Pressure, temperature, and radar altitude trans- measurement area. Soil samples, to a depth of 15.0 ducer data were alst acquired and stored by the cm, were also obtained at the center and at four l REDAR. pointsof thecompasson thecircumferenceof the n 5

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f) ; terrestrial f rom the background gamma com-

.M,y j  ; ponent.The background consists of gamma

O  ; V sources from the aircraft, cosmic rays, and airborne radon.

- 4. Following the perimeter and test line flight, l

i g routine survey flights began. Each flight-

$_ , preceded by a preflight in which the system j l "" ws librated and the data tape analyzed for l 20

• proper system operation-consisted of: I I

, - a. A pass over the test line at survey altitude.

b. Passes in an north-south or south-north direction of 20 or more 16-kilometer-long (10-mile-long) survey lines.

c. A repeat pass over the test line.

All the survey flights were flown at an altitude of 90 meters (300 feet).

After each survey flight the data were eval-Figure 2. DATA REDUCTION VAN SYSTEM uated forintegrity and anomaliesin a routine Q manner on the computer-based data reduction l system. All the gamma, position, and meteo-circular area. The soil samples were dried and r I gical data were plotted and examined. ,

their gamma activities measured on a germanium-based detector system in the EG&G/EM Santa An outline of the survey parameters is given Barbara laboratory.t2 in Table 1.

O 2.4 Byron Survey Method A standardized procedure for reactor surveys was followed at Byron. The method seeks to obtain Parameter Value O iarge-area gamma environmentai data in an etfi- Survey altitude 91 m (300 ft) cient and timely manner. Steps in the procedure are as follows.

Flight line spacing 152 m (500 f t)

1. One UHF transponder unit was placed at the Flight line length 16 km (10 mi)

Greater Rockford Airport and a second unit Number of lines 107 O on a farm 2 kilometers (1 mile) south of Seward, lilinois. These transponders, together Flight line direction N-S with the Byrcn Station, formed an approxi- Area surveyed 260 sq km (100 sq mi) mate equilateral triangle. 89* 16'55" W, Location of Byron Reactor 42* 04'30" N

2. A perimeter survey of roads in the 260 squ re-kilometer (100-square-mile) area was Gamma data (er;argy O then flown. The position data from the tran- spectra, livetime) sponders were used to scale each subsequent acodire rate 1 per second survey datum to its correct position on a map and an aerial photograph of the area.

. 3. A test line, approximately 2 kilometers (1 5. During the aerial survey, ground-based mile) long, was located durina the perimt.ter exposure rate measurements were made and flight. This line was flown at several altitudes soil samples collected at f our locations within so that the gamma and meteorological data the survey area. These data were used to O

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) i support the aerial measurements. A special where effort was made to obtain ground-based and aerial data at the same time at one of these A = altitude in ft ]

locations. GC(A) = gross count rate at altitude A (cps) l

) B = cosmic, aircraft, and radon

6. Af ter the data acquisition flights were com- background [

j pleted, the total gamma count rates (less W background) were plotted to form a contour The coefficient 0.001840. was normalized to the map. The plot was overlaid on a USGS map mean air temperature (17* C) and pressure (14.5 and an EG&G/EM aerial photograph of the psi) during the Byron survey.

g area bef ore the survey crew lef t the operation Equation 2 was used to compute the exposure site. rate from the terrestrial gross count rate. For the Byron survey, flown at 91 meters (300 feet),

Equation 2 becomes-3.0 GENERAL DATA REDUCTION l D The aerial system uses two primary methods to E treat gamma fluence measurements as seen by Ne (1 m) = (GC - 8)/830 R/h (3)

Nal(Tl) detectors. The first is the gross count (GC) or tota' gamma count rate. The second is the spectral window technique. These and other The gross count has been used for many years in methods are described in detail in a separate the aerial system as a measure of exposure. Its g publication.a simplicityyieldsa rapid assessment of thegamma environment.

Anomalous or non-natural gamma sources are 3.1 Gross Count found from increases in gross count rate over the natural count rates. However, subtle anomalies

- The gross count is defined as the integral count in are difficult to find using the gross count rate in the energy spectrum between 38 kev and 3016 kev.

areas where its magnitude is variable due to, for example, geologic or ground cover changes.

3016 kev Differential energy data reduction methods, as discussed in the next section, are used to increase GC = {

38 kev Energy Spectrum (1) the aerial system's sensitivity to anomalous ga m ma O emitters.

This integral includes all the natural gammas from potassium-40, uranium-238, and thorium- 3.2 Spectral Windows 232 (the major terrestrial, natural gamma emitters).

Other natural contributors to this integral are The aerial system produces each second a gamma f3 cosmic rays, aircraft background, and airborne energy spectrum f rom which the GC is computed.

radon daughters. Generally, the ratio of natural components in any two integral sections (windows) of the energy The response versus altitude of the aerial system s ectrum will remain nearly constant in any given

to terrestrial gammas has been measured over a ea-documented test line near Las Vegas, Nevada for j which the concentration values and the 1-meter exposure rates have been measured separately. b c From this calibration the terrestrial gross count rate has been associated with the 1-meter expo-y M

= Constant (4)

-sure rate in microroentgens per hour ( R/h) for E=a E=b natural radioactivity. The conversion e luation is:

g where E 5m l1 m) = ((GC(A) B]/1440} Exp(0.001840 x A)pR/h E = energy (2) c>b>a 7

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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 g' Rock River to 12 R/h over some of the farmland. 4A Ground-Based Measurements 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 n quite uniform, the varying terrestrial component were dried and counted on a calibrated gamma (from K-40, the U-238 series, and the Th-232 spectrometer in the laboratory. The "in situ" f

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

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• Inferred from aerial survey data collected atan altitude of I 90 ~.eters (3ms feet). A cosmic IL compownt of 3.8 pR/h has bsen added to the measured terrestrial component.

Q 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

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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 g included the effect of soll moisture.s The expo- 3. Since only a limited number of soil samples 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.

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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

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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.

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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.

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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.

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DISTRIBUTION NRC/HQ LBL L. K. Cohen (1) H. A. Wollenberg (1)

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BYRON STATION BYRON. Ill ' 'OIS EGG-10284 -1083 DATE OF SURVF.: APRIL 1985 DATE OF REPORT. JULY 1985 V

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