ORP/EERF-78-1
RADIATION DOSE ESTIMATES DUE TO
AIR PARTICULATE EMISSIONS FROM
SELECTED PHOSPHATE INDUSTRY
OPERATIONS
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
-------
Technical Note
ORP/EERF-78-1
Radiation Dose Estimates
due to
Air Particulate Emissions from
Selected Phosphate Industry Operations
J. E. Partridge
T. R. Morton
E. L. Sensintaffar
Eastern Environmental Radiation Facility
Office of Radiation Programs
U.S. Environmental Protection Agency
P. O. Box 3009
Montgomery, Alabama 36109
G. A. Boysen
Occupation Health and Injury Control Branch
Navajo Area Office
Window Rock, Arizona 86515
June 1978
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
Eastern Environmental Radiation Facility
Montgomery, Alabama 36109
-------
EPA Review Notice
This report has been reviewed by the Environmental Protection
Agency (EPA) and approved for publication. Approval does not
signify that the contents necessarily reflect the views and policies
of the EPA, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
-------
PREFACE
The Eastern Environmental Radiation Facility (EERF) participates in the identification
of solutions to problem areas as defined by the Office of Radiation Programs. The Facility
provides analytical capability for evaluation and assessment of radiation sources through
environmental studies and surveillance and analysis. The EERF provides technical
assistance to the State and local health departments in their radiological health programs
and provides special analytical support for Environmental Protection Agency Regional
Offices and other federal government agencies as requested.
This study is one of several current projects which the EERF is conducting to assess
environmental radiation contributions from naturally occurring radioactivity.
Charles R. Porter
Director
Eastern Environmental Radiation Facility
in
-------
ABSTRACT
The EPA Office of Radiation Programs has conducted a series of studies to determine
the radiological impact of the phosphate mining and milling industry. This report describes
the efforts to estimate the radiation doses due to airborne emissions of particulates from
selected phosphate milling operations in Florida.
Two "wet process" phosphoric acid plants and one ore drying facility were selected for
this study. The 1976 Annual Operations/Emissions Report, submitted by each-facility to the
Florida Department of Environmental Regulation, and a field survey trip by EPA personnel
to each facility were used to develop data for dose calculations. The field survey trip
included sampling for stack emissions and ambient air samples collected in the general
vicinity of each plant. Population and individual radiation dose estimates are made based
on these sources of data.
IV
-------
CONTENTS
Page
Preface iii
List of Tables and Figures v-vi
Abstract iv
I. Introduction 1
II. General Processes: Description and Emissions 1
III. Data Collection 6
IV. Dose Assessment 21
V. Summary and Conclusions 30
List of Tables
1. Annual Summary of Emissions - Ore Drying Facility 7
2. Annual Summary of Emissions - Wet Process Plant A 7
3. Annual Summary of Emissions - Wet Process Plant B 8
4. Radium, Uranium, and Thorium Concentrations in Florida
Phoshate Industry Products 9
5. EPA Stack Sampling Data 12
6. Annual Summary of Emissions for Sources Sampled by EPA 13
7. Comparison of EPA and Facility Sampling Data 15
8. 210Po data for Wet Process Plant A 15
9. High Volume Air Samples Around Phosphate Ore Dryer Plant 18
10. High Volume Air Samples Around Wet Process Phosphate Plants 18
11. Ambient Air Sampling Stations 19
12. Isotopes Above Average Background 20
13. Andersen Samplers Operated at Polk County, FL 22
14. List of Assumptions in Computer Modeling Common to All Three Plants 26
15. Dose Conversion Factors 27
16. Dryer Plant Source Term 27
17. Wet Process Plant A Source Term 27
18. Wet Process Plant B Source Term 27
19. Individual Dose Estimates 28
20. Population Doses within 80 km 29
21. Dose Predictions Based on High Volume Samples 29
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List of Figures
Page
1. 238U and 232Th Decay Series 2
2. Phosphate Rock Processing, Flow Diagram 3
3. Wet Process Phosphoric Acid Flow Diagram 5
4. Thermal Process Flow Diagram 9
5. EPA Stack Sampling Train 13
6. Off-Site Air Sampling Sites 16
7. Phosphate Mining and Processing Area 17
8. Ore Drying Plant. Log Probability Plot of Particle Size 23
9. Wet Process Plant B. Log Probability Plot of Particle Size Run #1 24
10. Wet Process Plant B. Log Probability Plot of Particle Size Run #2 29
VI
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I. Introduction
The EPA Office of Radiation Programs has been conducting studies of the
radiological impact of the phosphate mining and milling industry.(1-4) Phosphate ore
has been shown to contain varying amounts of naturally occurring radionuclides of
238U and 232Th series (figure 1). The mining and milling of these ores results in the
dispersal of radium, uranium, thorium, and other radionuclides throughout the
environment, which could increase the radiation doses to the general population. The
objective of this investigation was to estimate the population and individual radiation
doses due to airborne emissions of particulates around selected phosphate milling and
processing facilities in central Florida.
II. General Processes: Description and Emissions
A. Phosphate Rock Processing
The preparation of phosphate rock generally involves strip mining to obtain
ore, benefication to remove impurities, drying to remove moisture, and grinding to
improve reactivity. These operations are shown graphically in figure 2. In the strip
mining operations the overburden is stripped from above the phosphate ore using
electric draglines. The ore is removed by the same dragline and dropped into a
sluice pit. In this pit, high pressure water is used to produce a slurry which is then
pumped to the washer plant.
In the washing and benefication process, marketable rock is separated from
sand tailings and clay slimes. This is accomplished through a series of screening
and flotation steps.
From the washing process the marketable rock is transferred to the drying and
storage area. Here the wet rock is dried in large rotating drums. After drying, the
rock is separated according to size and grade and stored. The material from the
dryers may be ground using ball mills before storage.
The predominate airborne emissions from this portion of the phosphate
industry are in the form of fine rock dust from drying and grinding operations.
Phosphate rock dryers are usually equipped with dry cyclones followed by wet
scrubbers. Phosphate rock grinders can be a considerable source of particulates.
Because of the extremely fine particle size, baghouse collectors are normally used
to reduce emissions.
B. Phosphoric Acid
Phosphoric acid is produced by two principal methods, the wet process and
the thermal process. The wet process is usually employed when the acid is to be
used for fertilizer production, and the thermal process is normally used for high-
grade chemical and food products.
-------
URANIUM - 238 DECAY SERIES
THORIUM - 232 DECAY SERIES
238
92u
45x10* yr
7,
'
234
90Th
24 da.
234
91Pa
/
^.,
234
92^
2.5xl05yr.
/M
A
230
90Th
Sxltfyr.
f
226
88Ra
1620 yr.
f~
222
86Rn
3.8 da.
?
218
84Po
3 min.
'
214
82Pb
27 min.
I 214 210
84^ 84*°
1.6x10* sec. 138 da.
/n /n
214 // L 210 /A /
83Bi #., 83Bi ^« -T
19.7 min. ty 5 da. y
/ '
/7B ^ 210 // B.ir 206
V 82^ V 82Pb
19.4 yr. Stable
232
90Th
1.4x1Ot)yr.
n
1
1
228
ggRa
5.5 yr
228
89^
6.1 hr
228
90^
1.9 yr
/M
//\r
*'V
224
88**
3.6 da
I"
220
86Rn
54 sec
f
212
84**
0.16 sec.
?,
'
212
82^
10.6 hr.
212
84^
3 x 1C7 sec.
/n
212 /\\
83Bi S/B.Y «
1 hr. "' U
/r?35T
/V I |a.Y 208
%.t 82^
y Stable
/
203 // e.Y
81TI V
3.1 min.
Figure 1. 2MU and M2Th decay series.
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Pit Mine
Or
Mat
-n
1
Water
f
Sluice Pit
Screen
n
Slime 11
Slime Storage
Pond
=-
Floatation
Sand 11
Tailings \l
Sand Tailings
Storage
, ____^ Drying ^______^ Phosphate
* Grinding ^ Rock
Figure 2. Phosphate rock processing, flow diagram.
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Wet Process Plants
The general operations performed at a wet process phosphoric acid plant are
shown in figure 3. In the wet process plants studied, phosphate rock is usually
received in railroad cars. The rock is dropped from car hoppers onto conveyor belts
which moves the rock to temporary storage. Car vibrators or shakers are used to
help dislodge rock packed in the railroad cars causing a very dusty environment in
the immediate vicinity of the unloading facility.
From storage, the rock is ground as necessary, using large ball mills. The
crushed rock is then mixed with sulfuric acid in the reactor vessel to make
phosphoric acid. After reaction, calcium sulfate (gypsum) is separated from the
phosphoric acid in pan filters and pumped as a slurry to the waste gypsum pile. The
phosphoric acid is normally concentrated to 54 percent PiOs and is then
transferred to the fertilizer plant for use in manufacturing various fertilizer
products. Gaseous fluorides are the major airborne emission problem in wet
process phosphoric acid facilities. Additional emission problems result from the
transferring of phosphate rock within the plant.
Thermal Process Plants
In the "thermal process" plants phosphate rock, coke and siliceous material
are electrically smelted in a furnace (figure 4). Elemental phosphorus is recovered
by condensing vapors from the furnace. The elemental phosphorus can then be
used to produce phosphoric acid.
Although elemental phosphorus is the principal product at these facilities,
ferrophosphorus and slag are also sold for various uses. The major atmospheric
contaminant from thermal process phosphoric acid manufacture is phosphoric
acid mist.
C. Phosphate Fertilizer Production
Phosphatic fertilizers can generally be divided into three categories: (1)
normal superphosphate, (2) triple superphosphate, and (3) ammonium
phosphates.
Normal superphosphate is the product resulting from the acidulation of
phosphate rock with sulfuric acid. Normal superphosphate contains from 16 to 22
percent P2Os .
Triple superphosphate is the product of the reaction between phosphate rock
and phosphoric acid. The product usually contains approximately 46 percent
The two general classes of ammonium phosphates are monoammonium
phosphate and diammonium phosphate. Several processes are used to
manufacture ammonium phosphates. Basically, phosphoric acid, sulfuric acid,
and anhydrous ammonia are allowed to react to produce the desired grade of
ammonium phosphate.
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Phosphate
Rock
Sulfuric
Acid
Gypsum
Pile
Drying
Grinding
Reactor
Vessel
Filter
Dry
Fertilizer
Product
Phosphoric
Acid
Fertilizer
Plant
Acid
Evaporator
Figure 3. Wet process phosphoric acid flow diagram.
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The primary airborne emissions from the production of phosphate fertilizers
are gaseous fluorides and some particulates from the grinding, drying, and storage
of the products.
Most facilities have granular fertilizer stored in large warehouse buildings. The
product is deposited in the building via conveyer belts and from there it is
outloaded as required using front-end loaders. When the product is being moved
by front-end loaders, the airborne particulates are visible.
For the purposes of this study, only particulate emissions known to contain
elevated levels of radioactivity were of interest. Those sources, determined from
previous studies, are operations involving phosphate rock dust and the drying,
storing, and shipping of finished fertilizer products.
III. Data Collection
To estimate population and individual radiation doses in the vicinity of the selected
operations, two sources of data were used: (1) the 1976 Annual Operations/Emissions
Report submitted by each facility to the Florida Department of Environmental
Regulation; (2) an EPA field survey of the facilities (February 1977).
Two wet process phosphoric acid plants and one ore drying facility were selected
for detailed study. These plants were selected because they generally typify the
phosphate industry in central Florida. Only wet process phosphoric acid plants (i.e. no
thermal process plants) were evaluated in this study since this is the most common
type of plant in the central Florida area.
In addition to these facility oriented data, ambient air samples were collected using
high-volume air samplers. These air samples were collected throughout the general
area of phosphate mining and milling.
A. Facility Reported Data
Each of three facilities studied supplied a copy of their 1976 Annual
Operations/Emissions Report. These reports detail total particulates given in
average pounds per hour and in total tons per year for each source. From these
reports total particulate emissions from sources known to contain radioactivity
were determined.
Annual airborne particulate emissions for each facility are summarized in
tables 1, 2, and 3. Radioactivity emissions were calculated by assuming the
concentration of radioactivity in the effluent from a given process to be the same as
the concentration in the raw products. Following this assumption, total
particulates were multiplied by previously determined concentrations shown in
table 4 (1) to yield the radioactivity emissions.
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Table 1
Annual summary of emissions (a)
Ore drying facility
Radium (b)
Uranium (b)
Thorium (b)
Phos
Phos
Phos
Source
Rock Dryer #1 (c)
Rock Dryers #3 & 4
Rock Transfer
Total
Operating
Time (hr)
4114
4338
4338
Total
Particulates
9
5.85 x 107
6.52 x 107
3.76 x 107
226Ra
MCi
2450
2740
1570
234U
MCi
2400
2670
1540
235 y
MCi
110
120
70
238(J
MCi
2400
2670
1540
227Tn
MCi
120
130
80
228Th
MCi
40
40
20
230Tn
MCi
2470
2760
1590
232Tn
MCi
30
30
20
(combined totals
for six stacks)
(a) From 1976 Air Pollutant Emissions Report.
(b) Radioactivity results calculated from Facility Rpoort and previous radioactivity
measurements of phosphate rock.
(c) Combined totals for twin stacks.
Table 2
Annual summary of emissions (a)
Wet Process - Plant A
Radium (b)
Uranium (b)
Thorium (b)
Total
Total
Source
TSP Dryer
Dry Product (TSP)
Shipping
Phos Rock Grinding
Phos Acid Process
(Phos Rock)
Phos Acid Process
/r^i. . n i.\
Operating
Time (hr)
4560
500
3950
6460
4000
Particulates
g
4.9 x
12.4x
15.3x
17.6 x
2.0 x
10s
10s
105
10s
10s
226Ra
MCi
12.5
26.1
64.1
74
8.4
234 y
MCi
34.5
72.1
62.5
72.2
8.2
235y
MCi
1.7
3.5
4.0
4.5
0.5
238 y
MCi
34.5
72.1
62.5
72.2
8.2
227Tn
MCi
0.71
1.5
3.1
3.5
0.4
228Th
MCi
0.54
1.1
0.9
1.1
0.12
230Tn
MCi
28.7
59.7
64.5
74.5
8.4
232Tn
MCi
0.77
1.62
0.67
0.77
0.09
(a) From 1976 Air Pollutant Emissions Report.
(b) Radioactivity results calculated from Facility Report and previous radioactivity
measurements of phosphate rock and GTSP.
-------
Table 3
Annual summary of emissions (a)
Wet Process - Plant B
Radium (b)
Uranium (b)
Thorium (b)
Source
DAP Reactor/
Granulator
DAP Dryer
TSP Reactor/Blunger
TSP Dryer
Product Storage (c)
Product Shipping (c)
Ore Unloading
(Phos Rock)
Unground Rock Storage
Storage (5 sources -
combined)
Phos Rock Feed
Phos Rock Grinding
& Storage
Ball Mill
(Phos Rock)
Ground Rock Silo
Feed Bin (Phos Rock)
Phos Rock Storage
Total
Operating
Time (hr)
7516
7516
7410
7410
8400
8400
8400
8400
8400
8400
8400
8400
8400
8400
Total
Particulates
g
7.19
7.41
2.13
11.4
9.88
11.7
3.53
1.50
2.15
2.15
0.86
2.04
1.52
1.51
x107
x107
x 107
x107
x 107
x 107
x 107
x107
x107
x107
x107
x107
x1010
x1010
228Ra
MCi
403
415
447
2390
2070
2460
1480
630
903
903
360
860
640
630
234U
MCi
4530
4670
1240
6610
5730
6790
1450
615
882
882
353
840
620
620
235y
MCi
216
222
60
319
277
328
67
29
41
41
16
39
29
29
zaey
M Ci
4530
4670
1240
6610
5730
6790
1450
615
882
882
353
840
620
620
227Th
MCi
115
119
26
140
119
140
71
30
43
43
17
41
30
30
228Tn
MCi
58
59
19
102
89
105
22
9
13
13
5
12
9
9
230Th
MCi
4670
4820
1020
5470
4740
5620
1490
630
910
910
360
863
640
640
232Th
MCi
29
96
28
148
128
150
15
/
9
9
4
9
7
7
(a) From 1976 Air Pollutant Emissions Report.
(b) Radioactivity results calculated from Facility Report and previous radioactivity
measurements of phosphate rock DAP and TSP.
(c) TSP radioactivity values used for calculations.
-------
Table 4
Radium, uranium and thorium concentrations
in Florida phosphate industry products (a)
Material
Diammonium
Phosphate (DAP)
Triple Super-
Phosphate (TSP)
Marketable Phos
Rock
Radium-226
(pCi/g)
.5.6
21
42
234
63
58
41
Uranium (pCi/g)
235 238
3.0 63
2.8 58
1.9 41
227
1.6
1.2
2.0
Thorium |
228
0.8
0.9
0.61
pCi/g)
230
65
48
42.3
232
0.4
1.3
0.44
(a) From reference (1).
Coke Silica
Phosphate y- __^_;=B_
Rock
Blending Sizing
Calcining
»
Electric
Furnace
Vapors
Phosphorus
Condenser
Ferrophosphorus
and Slag
Figure 4. Thermal process flow diagram.
Elemental
Phosphorus
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For example, the stack for dryers #3 and 4 at the ore drying facility released a
total of 6.52x107 g of rock dust during 1976 and previous studies have shown that
phosphate rock has a concentration of 42 pCi/g 226Ra. Therefore, this stack
released approximately (6.52x107 g x 42 pCi/g) 27.4x108 pCi of 226Ra to the
atmosohere during 1976. Similar calculations were made for each source, isotope
and product.
1. Ore Drying Facility
The annual summary of emissions for the ore drying facility studied is
shown in table 1. Dryer #1 vents through twin stacks 24 m tall, both 1.5 m in
diameter. During 1976 this dryer processed 7.4x10* kg of wet phosphate rock.
This dryer is equipped with a wet scrubber to reduce particulate emissions.
Dryers #3 and 4 vent through a common stack 24 m tall and 2.4 m in
diameter. During 1976 these dryers processed a total of 1.98x109 kg of wet
phosphate rock. These dryers are also equipped with wet scrubbers to reduce
particulate emissions.
The six phosphate rock transfer stacks vary in height from 10.4 m to 47 m
and in diameter from 0.7 m to 2.1 m. These stacks are used to vent the various
points within the facility where phosphate rock is transferred from one location
to another. Each of these stacks is equipped with wet scrubbers to reduce
particulate emissions.
2. "Wet Process" Phosphoric Acid Plant A
The annual summary of particulate emissions for one of the wet process
plants is shown in table 2. During 1976 a total of 4.08x108 kg of phosphoric acid
and 2.27x108 kg of granular triple super phosphate, both expressed as 100
percent .PiOs were produced by this facility.
The emission sources listed in this table vent to the atmosphere at heights
ranging from 42.7 to 24.4 m above grade. These stacks are equipped with fabric
filters and wet scrubbers to reduce particulate emissions.
3. "Wet Process" Phosphoric Acid Plant B
The 1976 annual summary of particulate emissions for the other wet
process plant included in this study is shown in table 3. During 1976 this facility
produced approximately 4.31x10" kg of phosphoric acid, 2.0X108 kg of
diammonium phosphate and 9.07x107 kg of triple superphosphate all
expressed as 100 percent P2Oi
The emission sources at this facility vent to the atmosphere at heights
ranging from 12.2 m to 56.4m. The stack diameters vary in diameter from 0.15
m to 2.4 m. Fabric filters and wet scrubbers are used to reduce particulate
emissions from these sources.
10
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B. EPA Field Study
1. Stack Sampling Data
This EPA field survey of the phosphate industry in central Florida
consisted of two portions: (1) measurement of actual particulate emissions
from selected stacks at each facility; and (2) ambient air samples collected in
the immediate vicinity of each plant and other locations in the general area of
the phosphate milling operations.
Stack measurements were performed with a particulate sampling train
similar to the one shown in figure 5 and in accordance with EPA guidelines set
forth in the Code of Federal Regulations, Title 40, Part 60 (5). The sampling
train uses a 65 mm glass fiber filter to trap the particulates removed from the
stack via the sampling probe. Each filter was preweighed priorto sampling and
following the sampling period the net filter weight was used to determine the
total particulate catch. After the particulate weight had been determined, the
filters were boiled with acid to remove particulate matter. Radiochemical
analyses were then used to determine the amount of each specific
radioisotope. A total of seven stacks were sampled by this method, two at the
ore drying facility and five at the two wet process phosphoric acid plants.
Resource constraints did not permit the sampling of all emission sources
within each facility. The emission sources sampled were selected based on
previous sampling data by each facility and operations known to produce
radioactive effluents. The EPA survey data were used to supplement the facility
reported data.
The results of the EPA stack sampling survey are shown in table 5. The
annual summary of emissions for the sources sampled during the EPA survey
are shown in table 6. This summary is based on the operating times for 1976
and the survey results given in table 5.
The EPA results are compared to the facility data in table 7. Only six of the
sampled stacks are shown in this table because the TSP dryer at plant A
actually has two vents to the atmosphere, one at the 30 m level and the other at
the 42 m level. The facility normally only samples the 30 m vent for particulates
and 42 m vent for fluoride. Facility reported data in table 2 reflects particulate
emissions at the 30 m level only. During the EPA survey only particulates being
emitted from the 42 m level were sampled. Therefore, to obtain the total
particulate emissions forthis dryer, it is necessary to sum the results for the two
levels.
Generally speaking, good agreement is noted between EPA data and some
of the facility reported data. Dryers #3 and 4 reported releases are in excellent
agreement with the EPA results. The facility operator at the ore dryer facility
stated that substantial modifications had been performed on the wet scrubber
for dryer # 1 which should have reduced the total emissions from these
twin stacks. In all cases the wet process plant B reported emissions were
greater than those measured by EPA. In some instances the plant data is higher
by a factor of 10. This overestimation of releases by the facility operator will in
turn result in an overestimation of radiation doses.
11
-------
Stack
Rock Dryer #1
Rock Dryers #3 & 4
TSP Dryer Plant "A"
TSP Dryer Plant "B"
TSP R/BL Plant "B"
DAP Dryer Plant "B"
DAP R/G Plant "B"
Hours Stack
Per Flow
Year mVmin
4114 1280
4338 5390
4560 3100
7411 2378
7411 136
7516 2200
7516 788
Vol.
Sampled
m>
1.76
2.68
1.65
1.93
1.64
1.32
1.39
Sample
Weight
mg
59.3
95.3
38.7
20.6
7.0
20.1
27.0
Ra-226
pCI/f liter
2.6 ± 3%
5.6 ± 2%
.06 + 12%
.40 ± 7%
.12 ±11%
.34 ± 8%
.04 ±26%
U-234
pCi/filter
1.95 ± 16%
5.01 ±13%
.214±28%
.545±21%
.187±31%
4.74 ± 7%
2.42 ± 10%
U-235
pCi/filter
.084 + 50%
.45 ± 23%
ND
.034 ± 73%
ND
.248 ± 28%
.141 ±38%
U-238
pCi/filter
1.84 ±16%
5.21 ± 13%
.176 ±31%
.50 ± 22%
.164+33%
4.37 + 7%
2.18 ±10%
Th-227
pCI/filter
.136 + 52%
.39 + 33%
ND
ND
ND
ND
ND
Th-228
pCi/filter
.403 ± 20%
.436 + 22%
.082 ±48%
.047 ± 60%
.078 + 49%
.109+ 41%
.113+40%
Th-230
pCi/filter
2.69 + 8%
4.75 + 6%
.172+32%
.453+ 19%
.16± 34%
3.94 + 7%
1.15 + 13%
Th-232
pCi/filter
.074 + 49%
,152± 37%
ND
.134+ 36%
ND
.068 + 52%
.036 ± 73%
ro
ND - Non detectable.
Table 5
EPA Stack Sampling Data
-------
Table 6
Annual summary of emissions for sources sampled (a)
by EPA
Uranium
Thorium
Source
Rock Dryer #1 (b)
Rock Dryers #3 & 4
TSP Dryer Plant "A"
TSP Dryer Plant "B"
TSP R/BL Plant "B"
DAP Dryer Plant "B"
DAP R/G Plant "B"
Total
Particulates
g
2.2 x107
5.0 x107
2.0 x 107
1.2 x107
0.2 x107
1.5 x107
0.7 x 107
226Ra
MCi
930
2900
30
220
4
260
10
234(J 235y 238y
M Ci M Ci MCi
700
2600
110
300
7
2560
620
30
240
ND
20
ND
190
40
660
2700
90
270
7
3280
560
227Th
MCi
50
200
ND
ND
ND
ND
ND
22BTh
140
230
40
30
3
80
30
230Th
MCi
97
2490
90
250
6
2960
290
232Th
/uCi
30
80
ND
70
ND
50
9
(a) Based on EPA sampling data and operating times for 1976.
(b) Combined totals for twin stacks.
Probe
Figure 5. EPA stack sampling train.
13
-------
In addition to the stack sampling, dust samples were collected from the
TSP bag house and from the ball mill dust collector at the wet process plant A.
These samples were returned to the laboratory for 210Po analysis. Based on
these analyses, total annual 210Po emissions for plant A were calculated and are
shown in table 8.
2. Off-Site Air Sampling Data
High-volume air samplers were used to collect particulate samples around
the two wet process plants and the ore drying plant. Each sampler utilized a 10
cm respirator type filter designed to trap dusts (MSA-BM-2133). Typical flow
rates ranged from 1416 l/m (50 cfm) to 1700 l/m (60cfm) at the start to 1133 l/m
(40 cfm) to 1416 l/m (50 cfm) after 2 to 3 days operation. Each sampler was
placed in a wooden housing mounted approximately 1 m above ground to
protect it from weather effects and ground level dust.
Locations for air samplers were selected primarily by availability of
electrical power at distances of approximately 300 to 1000 m from each plant.
Whenever possible samples were collected in the plume downwind from the
plants where stack sampling was being done. Distance and direction from each
plant for each sampling location are provided in tables 9 and 10. Tables 9 and
10 also indicate the volume of air drawn through the filter and the activities of
226Ra, 234U, 235U, 238U, 227Th, 228Th, 230Th, and 232Th per cubic meter of airforeach
location.
Ambient particulate levels for the general area were determined by
operating air samplers at seven additional sites (see figures 6 and 7.) These
were located coincident with Florida State Department of Environmental
Regulation air monitoring sites in Polk County. These samplers were operated
for two periods of 48 to 72 hours. Sample volume and activities of radium,
uranium, and thorium isotopes per cubic meter of air are provided in table 11.
Statistical analysis of the concentrations of each isotope for the ambient
air sampling locations indicates that location I (table 11) had significantly
higher activities than the other six locations. A one-way analysis of variance
and multiple range test proved that, at the 95 percent level of confidence,
ambient location I was above the average level determined for the six other
sites. The proximity of this sampling site to several phosphate chemical
processing plants could easily have led to the increased activity levels. The
other six ambient sites were much more distant from any on-going phosphate
processing or mining activities.
One-way analysis of variance was then used (when sufficient data was
available) to compare the concentration of each of the isotopes at each of the
locations around plant A, plant B, and the dryer plant to the concentration at the
ambient sites (excluding ambient location I). At the 95 percent level of confidence
the locations shown in table 12 were found to be above ambient concentrations for
each of the isotopes shown. There was not sufficient data for 235U and W7Th at these
locations to apply this test.
14
-------
Table 7
Comparison of EPA and facility sampling data (a)
Total Particulates
Radium-226
Uranium-234
Thorium-230
Facility
Data
9
5.85x1 07
6.52x1 07
11.4X107
2.13x107
7.41 x107
7.19x107
EPA
Data
9
2.2x1 07
5.0x1 07
1.2x107
0.2x107
1.5x107
0.7x1 07
Facility
Data
MCi
2450
2740
2390
447
400
400
EPA
Data
MCi
930
2900
220
4
260
10
Facility
Data
/"Ci
2400
2670
6610
1240
4600
4500
EPA
Data
ftd
700
2600
300
7
2560
620
Facility
Data
MCi
2470
2760
5470
1020
4800
4600
EPA
Data
/"Ci
970
2500
250
6
3000
300
Rock Dryer #1
Rock Dryers #3 & 4
TSP Dryer "B"
TSP R/BL "B"
DAP Dryer "B"
DAP R/G "B"
(a) Annual summary based on 1976 operating times.
Source
TSP Dryer
Dry Product
(TSP) Shipping
Rock Grinding
Phos Acid Process
(Rock)
Phos Acid Process
(Rock)
Table 8
2ioPo
Wet process plant A (a)
Total
Particulates
g
200x10s (b)
12.4x10s
15.3x105
17.6x105
2iop0
/* Ci/yr
630
39
62
71
2.0x10s 8
(a) Based on a Concentration of 31.6 pCi/g 210Po in TSP and 40.3 pCi/g 210Po in phos rock.
(b) Sum of two stack vents (100* and 140').
15
-------
AUBURNDALE
OPLANT A
©PLANT B
0DRYER PLANT
Figure 6. Off-site air sampling sites.
16
-------
MINERALS PROCESSING PLANT
CHEMICAL PLANT
39
1-4
HILLSBOROUGH COUNTY
MANATEE COUNTY
Figure 7. Phosphate mining and processing area.
17
-------
Table 9
High volume air samples around phosphate ore dryer plant
Approx. Distance Approx. Direction 226Ra 234U 235U 238U 227U 228Th 230Th 232Th
From Plant From Plant fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3
Dryer Plant
Location I
IV
IV
V
Average
Std. Deviation
260m
400m
375m
400m
400m
375m
400m
400m
230°
140°
90°
35°
140°
90°
35°
335°
6.41 19.20 0.90 18.90
10.50
0.49
5.13
8.04
1.24
4.20
0.67
8.92
0.56
4.39
4.68
1.16
3.51
0.65
0.48
0.01
0.21
0.20
0.06
0.18
0.02
8.58
0.52
4.35
4.60
1.20
3.51
0.66
0.33
0.05
0.17
0.30
0.05
0.11
0.03
0.41
0.13
0.22
0.28
0.07
0.10
0.06
8.36
0.76
4.57
7.20
1.20
3.41
0.61
0.46
0.07
0.07
0.19
0.04
0.10
0.04
4.59 5.38 0.26 5.29 0.15 0.18 3.73 0.14
3.66 6.23 0.30 6.11 0.12 0.13 3.14 0.15
Table 10
High volume air samples around wet process phosphate plants
Approx. Distance Approx. Direction 226Ra 234U 235U 238U 227Th 228Th 230Th 232Th
From Plant From Plant fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3 fCi/m3
Plant A
Location I
II
Average
Std. Deviation
Plant B
Location I
II
III
IV
V
Average
Std. Deviation
1000m
750m
1000m
300m
1370m
2100m
1000m
65°
145°
100°
210°
275°
275°
100°
0.26 0.25
2.39 0.68
1.33 0.47
1.51 0.30
0.03
0.03
0.03
0.24
0.66 0.04
0.45 0.04
0.30
0.03
0.41 0.53 0.03 0.53
1.91 2.22 0.09 2.38
0.09 0.11 - 0.12
0.21 0.32 0.0-f 0.28 0.01
1.31 1.31 0.06 1.34 0.07
0.786 0.898 0.05 0.93 0.04
0.789 0.867 0.04 0.94 0.03
0.02 0.31 0.01
0.04 0.67 0.03
0.03 0.49 0.02
0.01 0.25 0.01
0.09 0.60 0.03
0.44 2.74 0.16
0.02 0.16 0.02
0.07 0.26 0.04
0.12 1.42 0.04
0.148 1.04 0.06
0.167 1.07 0.06
18
-------
Table 11
Ambient air sampling stations
Location
Ambient Station I
I
III
IV
IV
V
V
VI
VI
VII
VII
Average
Std. Deviation
Locations II-VII Average
Std. Deviation
226Ra
'Ci/m3
5.64
2.60
0.43
1.41
1.22
0.77
0.13
0.12
0.28
0.73
0.20
0.12
0.17
0.21
1.00
1.51
0.48
0.45
"
-------
Table 12
Isotopes above average ambient concentration
Location Isotopes
Plant A
Location II 226Ra
Plant B
Location II 228Ra, 234U, 238U, z28Th, 230Th, 232Th
Dryer Plant
Location I 226Ra, 234U, 238U
Location II 226Ra, 234U, 238U, 230Th, 232Th
Location IV 226Ra, 234U, 238U, 230Th
20
-------
Particle size analysis of the air in the plume from stacks at wet process
plant A and the ore dryer plant were done with Andersen 2000 Air Samplers
(Model 65-000). These samplers utilized a series of offset filters in a specially
designed system plate that sizes aerodynamically suspended particulate
matter into four fractionations (1.1, 2.0, 3.3, and 7.0 p. m) with the submicron
material being trapped on a backup filter. High-volume air samplers used with
the Andersen 2000 samplers were calibrated with a water-filled manometer to
provide 566 liters per minute (20 cfm) flow through the filter system. These
samplers were placed directly in the plume from the plant with the aid of
portable-electric generators. The results of the analysis of these samples are
shown in table 13.
A log normal distribution was assumed for the activities deposited on the
Andersen filters. For each Andersen sampler run 234U, 228Ra, and 230Th activities
were plotted on log probability paper (figures 8, 9, and 10) to determine the
AMAD (activity median aerodynamic diameter) of the particulate emissions.
For the dryer plant a value of 8.2 M m was found for the AMAD while the AMAD
value for the wet process plant B was 2.8 n m for the first run and 2.9 nm for the
second run. Based on the preceding results, a median particle size of 8 n m was
assumed for dryer plant emissions and an AMAD of 3 /* m was assumed as the
median diameter of particulate emissions from both wet process plants.
IV. Dose Assessment
The computer code AIREM (6) was used to make dose estimates resulting from
plant emissions given in tables 1, 2, 3, and 6. AIREM uses a sector averaged diffusion
equation to determine an average concentration or dose in a given sector at a specific
downwind distance. The lung dose conversion factors are derived from information
contained in the ICRP Task Group Lung Model Report (7) and ICRP Report Number 19
(8). A list of assumptions, dose conversion factors, and total source terms for each
plant aregiven in tables 14,15,16,17, and 18. The total source terms were based on the
reported operating times for 1976 and, where available, EPA stack sampling results
were used. In those cases where EPA data were not available, previously reported data
given in tables 1, 2, and 3 were used.
Individual and population dose estimates to the lung were made for each plant.
Individual dose estimates were based on the nearest residence to each plant except in
the case of wet process plant A where no residence was nearby. Individual dose
estimates were also made for the maximum lung dose at the 400 m distance. This
distance represents the nearest residence assumed to be realistically possible at a
typical plant where the distance is measured from the point of release and not the site
boundary. This distance was chosen as a reference point for comparison purposes
only. Population doses were based on population distributions generated by computer
code from U.S. Census Bureau information for this area. Individual lung dose
estimates (mrem/yr) and population doses (person-rem/yr) are given in tables 19 and
20. Ground level release with deposition and depletion plus a building wake correction
(9) were assumed for the individual dose calculations. Elevated release points were
assumed for some calculations; however, they did not significantly change the results.
The results of elevated release point calculations are not shown in this report.
The dose estimates from wet process plant A reflect the addition of 210Po to the
source term as shown in table 8. These 210Po values were available for this plant only
and are estimated to contribute approximately 12 percent of the annual dose from wet
process plant A releases.
21
-------
Table 13
Andersen samplers operated at Polk County, FL
(fCI/m3)
Particle Size
Location/Isotope
Ore Dryer
234U
23SU
238|J
227Th
228Th
230Tn
232jn
226Ra
Sample Gross Wt.
Wet Process Plant B
Run 1
234U
235U
238U
228Tn
230Th
232jn
226Ra
Sample Gross Wt.
Run 2
23XU
23SU
238U
228Tn
230Th
232jn
226Ra
Sample Gross Wt.
7 Mm
Filter A
21.9
1.46
21.1
-
1.13
22.7
0.541
26.5
0.033g
2.54
-
1.85
1.14
3.12
0.706
1.77
0.01 8g
0.985
-
1.49
0.286
1.24
0.175
1.12
0.002g
3.3-7.0 Mm
Filter B
9.33
-
8.95
1.34
10.8
1.00
9.27
0.01 4g
1.18
-
0.850
0.784
3.18
-
2.43
0.0004g
1.44
0.175
1.44
0.372
0.810
-
0.743
0.01 5g
2.0-3.3 Mm
Filter C
3.74
-
4.03
-
0.96
4.96
-
4.64
0.006g
1.04
0.794
1.04
3.94
0.828
2.87
0.0004g
1.08
0.275
1.32
0.335
1.06
0.335
0.892
-
1.1-2.0 Mm
Filter D
2.56
-
2.46
-
1.09
2.56
-
4.42
O.OOSg
1.08
-
1.26
0.993
0.993
-
2.65
*
0.364
-
0.364
0.282
0.870
0.818
O.OOOSg
1.1 M m
Filter E
4.98
0.618
5.41
-
0.982
5.70
5.96
0.006g
1.70
-
1.95
0.960
0.960
0.861
2.87
"
1.04
-
0.926
0.283
1.11
0.632
0.967
O.OOSg
22
-------
10
ro
tn
I
o
I
c
8
*w
o>
]3
r
£
U-234
Th-230
O Ra-226
0.01
0.1
0.5 1
10
20 30 40 50 60 70 80 90 95 98 99
Cumulative percent
Figure 8. Ore drying plant. Log probability plot of particle size.
99.9
99.99
-------
10
rva
o
I
CO
0
O
i
U-234
Th-230
O Ra-226
0.01
0.1
0.5 1
10 20 30 40 50 60 70
Cumulative percent
80
90 95 98 99
99.9
99.99
Figure 9. Wet process Plant B. Log probability plot of particle size run #1.
-------
10
N>
Ul
CO
8
U-234
Q Th-230
O Ra-226
0.01
0.1
0.5 1 2 5 10
20 30 40 50 60 70
Cumulative percent
80 90 95 98 99
99.9
99.99
Figure 10. Wet process Plant B. Log probability plot of particle size run #2.
-------
Table 14
List of assumptions in computer modeling
common to all three plants
1. 16 sectors
2. 5 stability classes (A-E)
3. 8 radionuclides (U-238, U-235, U-234, Th-227, Th-228, Th-230, Th-232, Ra-226)
4. Mixing layer depth: 1000m
5. Rainfall fraction: .05
6. Washout coefficient: 2.0 x 10-4 I/sec
7. Meteorological data based on Orlando (McCoy, AFB), Florida, information
8. Population distributions generated by computer code based on U.S. Census Bureau information
9. With dry deposition and depletion - deposition velocity: 1 cm/sec
10. Dose conversion factors
A. 3 m AMAD particle size for Wet Process Plants A and B
8 m AMAD particle size for Dryer Plant
B. Class Y lung model (assumes insoluble particles)
C. Pulmonary lung dose
D. Dose refers to a 50 year dose commitment
E. Breathing rate of 23 nWday (adult male)
F. Lung mass of 570 g
G. Continuous expsure for a year
26
-------
Table 15
Table 16
Dose conversion factors
Dryer plant source term*
Isotope
226Ra
assy
235(J
234|J
227Th
228Th
230Th
232Th
210Po
(mrem/sec)/(Ci/m3)
1.20x108
1.02x108
1.10x108
1.20x10"
2.80x107
4.60x108
1.10x10"
1.60x10"
2.80x107
Isotope
238JJ
235 U
234(J
227Th
228Jh
230Th
232Th
226Ra
Ci/year
4.90x10-3
3.41x10-"
4.84x10-3
3.25x10-4
3.93x10-"
5.05x10-3
1.27x10-"
5.40x10-3
"Based on operating times given in table 1.
Table 17
Wet process plant A source term*
Isotope Ci/year
Table 18
Wet process plant B source term*
23B|J
235(J
227Tn
228Th
230Th
232Tn
226Ra
210PO
3.40x10-"
1.40x10-5
3.60x10-4
9.20x10-6
4.38x10-5
3.26x10-"
3.90x10-6
2.15x10-"
8.10x10-"
Isotope
238(J
2351I
227Th
228Tn
230Th
232Th
226Ra
Ci/year
2.3x10-2
1.1x10-3
2.3x10-2
6.0x10-"
4.3x10-"
2.0x1O-2
4.8x10-"
1.1x10-2
"Based on operating times given in table 2.
'Based on operating times given in table 3.
27
-------
Table 19
Source
Dryer Plant
Wet Plant "A"
Wet Plant "B"
Individual dose
(mrem/yr)
Maximum
Location Lung Dose
400m S
15
400m NNW
840m S
800m W*
1860mW
2700m E
No residence at this location. The nearest residence would receive much less than 1 mrem/yr.
400m S
400m S
1.4
60
Nearest Residence
Location Lung Dose
5.5
7.4
0.7
5
1.5
28
-------
Table 20
Population doses within 80 km (a)
Source Person-rem/yr (b)
Dryer Plant 1.2
Wet Plant A 0.1
Wet PlantB 6.6
(a) Ground level release assumed
(b) To the lung
Table 21
Dose predictions based on high volume samples (a)
Location Lung Dose (mrem/yr)
Average Ambient
w/o Location I 8.5 (b)
Ambient Station I 33.0 (c)
Wet Process Plant B
Location II (300 m, 210°) 21.0 (c)
(a) Based on data in tables 10 and 11.
(b) 1 m AMAD particle size.
(c) 3 m AMAD particle size.
29
-------
V. Summary and Conclusions
The results of this study show small, but measurable, increases in levels of
radioactivity in air surrounding these selected phosphate milling operations. This is
evidenced by results of the air sampler measurements shown in tables 9,10,11, and 12.
However, it should be noted that levels statistically above background were measured
in only 5 of the 12 locations sampled. Also these locations were all within 750 m from
the respective plants. The dose estimates based on data from ambient locations also
show the effects of the phosphate industry airborne emission. The projected lung dose
at ambient location I is 33 mrem/yr compared with an average of 8.5 mrem/yr at the
remaining ambient locations.
Dose projections based on stack release data also indicate the magnitude of
individual lung doses in the area. The maximum individual dose at the nearest actual
residence is estimated to be 7.4 mrem/yr (above background, i.e., in addition to
background). This location was 840 m south of the ore drying facility.
Population doses within 80 km of the wet process plant B were calculated to be 6.6
person-rem per year. However, this dose is most likely overestimated due to the
overestimation of releases by the facility operator.
The estimated doses based on stack sampling data and on high-volume sampling
data at location II near wet process plant B were within a factor of 4 and most likely
would be closer if more accurate source terms were available.
In conclusion, the results of this study show slight increases in the levels of
radioactivity in air surrounding the plants studied. These slight increases in air
concentration are estimated to produce an individual lung dose of a few mrem/yr to
persons living in the immediate area of these plants. These estimations are based on
stack measurements at the point of release and on air samples collected at the point of
interest. Based on our data, it appears the ore drying operations are the most
significant source of airborne radioactive particulates.
30
-------
REFERENCES
1. GUIMOND, R. J., and S. T. WINDHAM. Radioactivity Distribution in Phosphate
Products, By-Products, Effluents, and Wastes, ORP/CSD-75-3 (August 1975).
2. WINDHAM, S. T., J. E. PARTRIDGE, and T. R. MORTON. Radiation Dose Estimates to
Phosphate Industry Personnel. EPA-520/5-76-014.
3. U.S. ENVIRONMENTAL PROTECTION AGENCY. Preliminary Findings, Radon
Daughter Levels in Structures Constructed on Reclaimed Florida Phosphate Land.
Technical Note ORP/CSD-75-4. Office of Radiation Programs, U.S. Environmental
Protection Agency, Washington, DC 20460.
4. FITZGERALD, J. E., R. J. GUIMOND, and R. A. SHAW. A Preliminary Evaluation of the
Control of Indoor Radon Daughter Levels in New Structures. EPA-520/4-76-018.
5. FEDERAL REGISTER. Standards of Performance for New Stationary Sources.
Federal Register, Vol. 36, No. 247 (December 1971).
6. MARTIN, J. A., et al. AIREM Program Manual. EPA-520/1 -74-004. (May 1974).
7. HEALTH PHYSICS JOURNAL. ICRP Task Group Lung Model. Health Physics, Vol. 12,
pp.173-207 (1966).
8. ICRP PUBLICATION 19. The Metabolism of Compounds of Plutonium and the
Actinides. Pergamon Press, New York, NY (May 1972).
9. NRC REGULATORY GUIDE 1.111. Methods for Estimating Atmospheric Transport and
Dispersion of Gaseous Effluents in Routine Releases from Light-Water Cooled
Reactors. (March 1976).
31
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TECHNICAL REPORT DATA
(Please read Instruction! on tht reverie before completing)
. REPORT NO.
ORP/EERF-78-1
3. RECIPIENT'S ACCESSION NO.
. TITLE AND SUBTITLE
Radiation Dose Estimates due to Air
Articulate Emissions from Selected Phosphate
Industry Operations
E. REPORT DATE
June 1978
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
J. E. Partridge
^- K . > , **
orton
G. A. Boysen
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING
10. PROGRAM ELEMENT NO.
Eastern Environmental Radiation Facility
P. 0. Box 3009
Montgomery, Alabama 36109
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Radiation Programs
Washington. P..C.
13. TYPE OF REPORT AND PERIOD COVERED
In house
14. SPONSORING AGENCY CODE
EPA/200/03
15. SUPPLEMENTARY NOTES
16. ABSTRACT
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Air emissions
Radiation dose
Phosphate industry
21. NO. OF PAGES
40
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (This Report)
unclassified
20. SECURITY CLASS (THIl paftl
unclassified
EPA Form 2220-1 (*-7J)
*U.S. GOVERNMENT PRINTING OFFICE: 1978-7^6-721/600'*. Region
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