JOSEPH M. FARLEY NUCLEAR PLANT · 2013. 7. 9. · (;.n egc.g . ~energy measurements group egg-1183-1812 c uc-41 march 1982 an aerial radiological survey of the joseph m. farley nuclear

(;.n EGc.G . ~ENERGY MEASUREMENTS GROUP

EGG-1183-1812 C UC-41

MARCH 1982

AN AERIAL RADIOLOGICAL SURVEY OF THE

JOSEPH M. FARLEY NUCLEAR PLANT

AND SURROUNDING AREA

THE

REMOTE SENSING

lABORATORY OF THE UNITED STATES

DEPARTMENT OF ENERGY

DOTHAN, ALABAMA DATE OF SURVEY: DECEMBER 1979

DISCLAIMER

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~n'>EGc.G ENERGY MEASUREMENTS GROUP

AN AERIAL RADIOLOGICAL SURVEY OF THE

JOSEPH M. FARLEY NUCLEAR PLANT

AND SURROUNDING AREA

DOTHAN, ALABAMA

DATE OF SURVEY: DECEMBER 1979

T. C. MAGUIRE G. R. SHIPMAN Project Scientists

REVIEWED BY

W. J. Tipton, Head Nuclear Radiation Physics Section

This Document is UNCLASSIFIED

G. P. Stobie Classification Officer

EGG-1183-1812 MARCH 1982

This work was performed by EG&G for the United States Nuclear Regulatory Commission through an EAO transfer of funds to Contract Number DE-AC08-76NV01183 with the United States Department of Energy.

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ABSTRACT

An aerial radiological survey was performed during the period 8 to 19 December 1979 over a 2000 square kilometer area centered on the two unit Joseph M. Farley Nuclear Plant near Dothan, Alabama. Radiological data were collected by flying north-south lines spaced 900 meters apart at an altitude of 150 meters above ground level. Processed data showed that all gamma rays detected within the survey area were those expected from naturally occurring radionuclides. Count rates obtained from the aerial platform were converted to exposure rates at 1 meter above the ground and are presented in the form of a radiation contour map. The observed exposure rates were between 4 and 12 microroentgens per hour {JIR/h), with most of the area ranging between 4 and 10JJR/h. These values include an estimated cosmic ray contribution of 4.0 11R/h but do not include any contribution from airborne radionuclides, i.e., radon. Exposure rates obtained from ground measurements taken within the survey area were in close agreement with the aerial data.

The data were also in close agreement with those obtained from a similar survey conducted during March 1977. Comparison of the results from both surveys indicated that no detectable change in the radiological characteristics of the survey area has occurred due to the operation of unit number 1 during the intervening period. The same equipment and procedures were utilized for both surveys.

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CONTENTS 0

2 Abstract

Sections

4 1.0 Introduction

4 2.0 Natural Background Radiation

4 3.0 Survey Site Description

4 4.0 Survey Description

4 4.1 Aerial Measurements 6 4.2 Ground-Based Measurements

7 5.0 Data Analysis

0 7 6.0 Results

7 6.1 Results of 1979 Survey 7 6.2 Comparison of 1977 and 1979 Survey Results

9 7.0 Conclusions

0 Figures

5 1 Aerial Survey Flight Lines and Survey Area Boundaries

6 2 Aerial Measurement Platform: Beechcraft King Air A-100

6 3 Interior of the Mobil Computer Processing Laboratory

8 4 Exposure Rate Contour Map Superimposed on a USGS Topographic Map of the Area Surrounding the Joseph M. Farley Nuclear Plant (December 1979 Survey)

9 5 Gamma Ray Energy Spectrum Typical of the Natural Terrestrial Background Radiation in the Area Surrounding the Joseph M. Farley Nuclear Plant (December 1979 Survey)

10 6 Exposure Rate Contour Map Superimposed on a USGS Topographic Map of the Area Surrounding the Joseph M. Farley Nuclear Plant (March 1977 Survey)

11 7 Gamma Ray Energy Spectrum Typical of the Natural Terrestrial Background Radiation in the Area Surrounding the Joseph M. Farley Nuclear Plant (March 1977 Survey)

Table

9 1 Comparison of Results from Ground-Based and Aerial Data (December 1979 Survey)

12 References

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1.0 INTRODUCTION

The United States Department of Energy (DOE) maintains the Remote Sensing Laboratories (RSL) in Las Vegas, Nevada and in Washington, D.C. The RSL is operated for the DOE by the Energy Measurements Group of EG&G. One of the major functions of the RSL is to manage an aerial surveillance program called the Aerial Measuring System (AMS) .

Since its inception in 1958, the AMS has continued a nationwide effort to document baseline radiological conditions surrounding energy-related sites of interest, including: nuclear power plants, manufacturing and processing plants and research laboratories employing nuclear materials.1 At the request of federal or state agencies, and by direction of the DOE, the AMS is deployed for various aerial survey operations.

The aerial radiological survey of the Joseph M. Farley Nuclear Plant and surrounding area near Dothan, Alabama, was requested by the U.S. Nuclear Regulatory Commission. Its purpose was to characterize the natural background radiation in the survey area prior to the start-up of unit number 2, an 860 MW pressurized water reactor (PWR). Unit number 1, also an 860 MW pressurized water reactor, has been in operation since December 1977. A similar survey utilizing the same equipment and procedures was conducted in March 1977 prior to the start-up of unit number 1.2

~0 NATURALBACKGROUND RADIATION

Natural background radiation originates from radioactive elements present in the earth, airborne radon, and cosmic rays entering the earth's atmosphere from space. The terrestrial gamma radiation originates primarily from the uranium decay chain, the thorium decay chain, and radioactive potassium. Local concentrations of these nuclides produce radiation levels at the surface of the earth typically ranging from 1 to 15 J1R/h.3 Some areas with high uranium and thorium concentrations in surface minerals exhibit even higher radiation levels, such as the Colorado Plateau area of the United States. One member of each of the uranium and thorium

decay chains is radon, a noble gas, which can diffuse through soil and be transported through the air to other locations. Therefore, the level of airborne radiation depends on the meteorological conditions, the mineral content of soil, the soil permeability, etc., existing at each location at a particular time. The airborne radiation typically contributes from 1 to 10% of the natural background radiation levels.

Cosmic rays, the space component, interact in a complicated manner with the elements of the earth's atmosphere and the soil. These interactions produce an additional natural source of gamma radiation. Radiation levels due to cosmic rays vary with altitude and geomagnetic latitude. Typical values range from 3.3JJR/h at sea level in Florida to 12 11R/h at an altitude of 3 km (10,000 ft) in Colorado.

The natural terrestrial radiation levels generally depend upon the type of soil and bedrock immediately below and surrounding the point of measurement. Within cities, the levels are also influenced by the nature of street and building materials.

3.0 SURVEY SITE DESCRIPTION

In order to characterize the natural background radiation in the area surrounding the Joseph M. Farley Nuclear Plant, the AMS was utilized during the period 8 to 19 December 1979 to survey a 2000 square kilometer area near Dothan, Alabama. The two unit Joseph M. Farley Nuclear Plant (operated by the Alabama Power Company) was at the center of the survey area. The plant is located near the west bank of the Chattahoochee River, 24 km east of Dothan. The community of Columbia is 7 km north and Ashford is 13 km southwest of the plant.

4.0 SURVEY DESCRIPTION

4.1 Aerial Measurements

Measurements were made along 46 flight lines approximately 50 kilometers long and spaced approximately 900 meters apart (Figure 1 ). Twenty-eight thallium activated sodium iodide, Nal (Tl), crystals mounted in a Beechcraft King Air A-100 fixed-wing aircraft (Figure 2) detected

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Figure 2. A E RIA L ME AS U REM EN T P LA T F 0 R M: BEECHCRAFT KING AIR A-100

the gamma rays while flying at an altitude of 150 meters and at a ground speed of 80 meters per second . Each Nai(Tl) crystal was 10 em in diameter and 10 em thick. The instrumentation and equipment used on this survey are described briefly here. A more detalied description of AMS systems and procedures can be found in a previous report.4

Scintillation pulses from each detector were summed and input to the Radiation and Environmental Data Acquisition and Recorder (REDAR) system on-board the aircraft. These pulses were first fed to an analog-to-digital converter and fanned out to : (1) a 300-channel multichannel analyzer for energy spectral information (0.05 to 3.0 MeV), (2) a gross count register for determining the rate of gamma ray detection integrated over energy, and (3) five single channel analyzers set up to monitor gamma rays with energies of particular interests.

The information from each of these subsystems, along with the position and altitude at which the measurement was made, was stored on a 9-track magnetic tape for later analysis. The altitude information was obtained from an on-board radar altimeter which gives the actual height above the ground with an uncertainty of approximately ±3 meters at a normal survey altitude of 150 meters. Positional information was derived from a microwave ranging system (MRS) consisting of two remotely located transponders and an on­board interrogator. The on-board interrogator

used the transit time of a microwave pulse to obtain the distance from the aircraft to each remote unit. Position uncertainty varied over the survey area, but was typically ±15 meters. The position information was also processed in real time on-board the aircraft to provide steering information to the pilot for flying the predetermined flight lines.

Magnetic tapes with recorded data from the aerial radiological survey were processed after each flight with the Radiation and Environmental Data Analyzer and Computer (REDAC) system. This computerized data analysis system was built into a five-ton step van. The interior of this van is shown in Figure 3. The REDAC system consisted primarily of a Data General NOVA 840 computer and peripherals. An extensive inventory of software routines was available for data processing .

Figure 3. INTERIOR OF THE MOBILE COMPUTER PROCESSING LAB ORA TORY

4.2 Ground-Based Measurements

Exposure rate values were measured with an ionization chamber placed one meter above the ground at selected locations within the survey area (see Figure 1 ). Ground sampling was done at the same time the aerial survey was conducted. In addition to the ion chamber measurements, ten soil samples were taken from each of two sites (Numbers 1 and 6). The soil samples were analyzed and results tabulated for this report by a team of scientists at EG&G's Santa Barbara Laboratory. Systems and procedures for soil sample data collection and analysis are outlined in a separate publication.s

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5.0 DATA ANALYSIS

Aerial radiation data were analyzed and processed to produce a gross count contour map and to determine the particular radioisotopes giving rise to the radiation levels within the survey area. The gross count contour map describes the radiation distribution of terrestrial radioisotopes. The airborne and cosmic ray contributions to these radiation levels were removed by subtracting the count rate measured over a body of water near the site from those measured over the survey area. The water line utilized for this survey was over the Walter F. George Reservoir approximately 16 kilometers north of the survey area.

The resulting net count rate of terrestrial origin was converted to an approximate exposure rate at one meter above the ground by applying a conversion factor of 680 counts per second per microroentgen per hour (J.IR/h). This factor was derived from many measurements made over areas with known concentrations of naturally occurring radionuclides. 4 An estimated cosmic ray contribution of 4 J.IR/h was then added to produce the total exposure rate at one meter minus any airborne radon contribution.

Analysis of the spectral data allows the determination of the specific radioisotopes responsible for the exposure rates in the area. Man-made radioisotopes, if present, can be identified by determining the energies of the detected gamma rays. Similarly, gamma-emitters typical of naturally occurring radioisotopes will yield characteristic energy spectra.

6.0 RESULTS

6.1 Results of 1979 Survey

An exposure rate contour map (derived from gamma ray gross count rates) of the area surrounding the Joseph M. Farley Nuclear Plant is shown in Figure 4. The exposure rates shown in micro roentgens per hour (J.IR/h) were normalized to a distance of one meter above the ground level and include a contribution from cosmic rays of 4 J.IR/h. These nominal values of exposure rates resulted from gamma rays emitted by naturally occurring radioisotopes within the energy range from 0.05 to 3.0 MeV. Deviations of the exposure rates from the nominal range overt he survey area (6 to 10 J.IR/h) were evident in several spots. The

presence of water in the rivers and low lying areas can lead to the lower levels of gamma ray activity as shown in Figure 4. Values above the nominal range (level E) were found in regions with higher than average concentrations of naturally occurring potassium and thorium. For example, the E levels along the Chattahoochee River banks in the southern portion of the survey area were found to be due to these radioisotopes. Regions such as these are commonly encountered throughout the U.S. A gamma ray energy spectrum typical of the natural terrestrial background radiation in the survey area is shown in Figure 5. Noted on the figure are the radioisotopes which emit gamma rays with energies corresponding to peaks in the spectra.

Results of the ground measurements are given in Table 1 along with the corresponding results from the aerial survey. As shown, there is good agreement between the two types of measurements. A major contribution to any discrepancy between ground and aerial survey results is due to the fact that each aerial measurement represents an average exposure rate over a much broader area than does a ground measurement.

6.2 Comparison of 1977 and 1979 Survey Results

The results of the survey conducted in March 1977 are summarized in Figures 6 and 7. 2

Comparison of the exposure rate contour maps from each survey (Figures 4 and 6) shows good agreement between the significant features of each. The exposure rate over the majority of the survey area in each case was between 6 and 8 J.IR/h (level C in both Figures 4 and 6).

Deviations in the boundaries of areas with low values of exposure rates are to be expected, especially in low lying areas where the standing water and soil moisture content can vary significantly over the year.* However, the general locations with low exposure rates (level 8 in Figures 4 and 6) in the eastern and southern regions of the survey area were the same in both surveys. Locations with exposure rate values

*Soil moisture measurements were repeated in only one location (number 7) during the 1979 survey, and, hence, significant quantitative soil moisture comparisons between the two surveys could not be made.

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Figure 5.

ENERGY CMEV) GAMMA RAY ENERGY SPECTRUM TYPICAL OF THE NATURAL TERRESTRIAL BACKGROUND RADIATION IN THE AREA SURROUNDING THE JOSEPH M . FARLEY NUCLEAR PLANT (DECEMBER 1979 SURVEY)

above the nominal range (levels 0 and E in Figures 4 and 6) also appear to be the same in both surveys. Again, slight variation in the boundaries can be expected due to changes in soil moisture and standing water.

The gamma ray energy spectra typical of the survey area from both surveys (Figures 5 and 7) show that the same gamma ray emitters are present in approximately the same relative abundance. In each case, all detected radioisotopes were ones that are typical of natural background, i.e., uranium and thorium daughter products and potassium-40.

7.0 CONCLUSIONS

An aerial radiological survey, conducted during December 1979, over a 2000 square kilometer area centered on the two unit Joseph M. Farley

Table 1. Comparison of Results from Ground-Based and Aerial Data (December 1979 Survey).

Site Soil Ground Survey Inferred Exposure Rate (JJR/h) Number Moisture (%) Gamma Exposure Rate (JJR/h) from Aerial Measurement (2)

I on Soil Analysis Chamber (1) Estimate (2)

1 7.5 7.5 7.0 6 - 8 2 10.3 (3) 6 - 8 3 7.9 (3) 6- 8 4 7.9 (3) 6- 8 5 8.7 (3) 6- 8 6 6.0 9.1 7.3 6- 8 7 8.7 (3) 6 - 8 8 8.3 (3) 6- 8 9 8.5 (3) 6- 8

10 8.1 (3) 6- 8 11 8.7 (3) 6- 8 12 7.3 (4) (3) 6- 8 13 7.9 (3) 6 - 8 14 7.9 (3) 6- 8 15 7.2 (3) 4- 6 16 6.8 (3) 4- 6 17 7.9 (3) 6- 8 18 8.3 (3) 6- 8 19 9.9 (3) 8- 10 20 9.3 (3) 6- 8

Notes: (1) Measurement made with Reuter Stokes Model RSS-111, Serial No. R 574 (2) Includes cosmic ray contribution of 4.0 JJR/h (3) No soil samples taken (4) This value is the average of nine measurements made in a square array of 90 meters on a

side, 45 meters between measurement points

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0 5 10 15 KILOMETERS

GAMMA EXPOSURE RATE AT ONE METER ABOVE GROUND {J.IR/h)*

"Inferred from aerial data obtained at an altitude of 150 meters. Exposure rates include an estimated cosmic contribution of 4tJR/h but do not include any contribution from airborne radon .

Figure 6. EXPOSURE RATE CONTOUR MAP SUPERIMPOSED ON A USGS TOPOGRAPHIC MAP OF THE AREA SURROUNDING THE JOSEPH M. FARLEY NUCLEAR PLANT (March 1977 Survey)

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Nuclear Plant revealed only those gamma ray emitters expected from naturally occurring radioisotopes. Exposure rates within the survey area varied between 4 and 1211R/h, with most of the area ranging between 4 and 10 11R/h. Further, comparison of measurements made during the December 1979 survey with those from a similar survey conducted during March 1977 showed

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that no change in the radiological characteristics of the survey area was detected with the AMS system. During this time period unit number 1, an 860 MW pressurized water reactor, had been operational. Supporting ground-based measurements made while the aerial survey was being conducted (December 1979) were in good agreement with the aerial measurements.

+,0 +,5 1.0 1.5 2 . 0 2.5 9.0

ENERGY CMEV)

Figure 7. GAMMA RAY ENERGY SPECTRUM TYPICAL OF THE NATURAL TERRESTRIAL BACKGROUND RADIATION IN THE AREA SURROUNDING THE JOSEPH M. FARLEY NUCLEAR PLANT (MARCH 1977 SURVEY)

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REFERENCES

1. Jobst, J.E., "The Aerial Measuring Systems Program." Nuclear Safety, March-April 1979, 20:136-147.

2. Hilton, L.K., An Aerial Radiological Survey of the Area Surrounding the Joseph M. Farley Nuclear Plant (1978). Report No. EGG-1183-1734. Las Vegas, NV: EG&G.

3. Klement, A.W., et.al., Estimate of Ionizing Radiation Doses in the United States 1960-2000, U.S. EPA Report ORP/CD 72-1, Washington, D.C., August 1972.

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4. Boyns, P. K., The Aerial Radiological Measuring System (ARMS): Systems, Procedures, and Sensitivity (1976). Report No. EGG-1183-1691 . Las Vegas, NV: EG&G.

5. Mohr, R., Fritzsche, A., and Franks, L., Ground Survey Procedures (1976). Report No. EGG-1183-2339. Santa Barbara, CA: EG&G.

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JOSEPH M. FARLEY NUCLEAR PLANT AND SURROUNDING AREA

DOTHAN, ALABAMA EGG- 1183-1812

DATE OF SURVEY: DECEMBER 1979 DATE OF REPORT: MARCH 1982

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