THE RADIOLOGICAL IMPACT OF THE
PHOSPHATE INDUSTRY - A FEDERAL PERSPECTIVE
By Richard J. Girimond
Assistant to the Director for Special Projects
Criteria & Standards Division
Office of Radiation Programs
U.S. Environmental Protection Agency
May 1976
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Presented at the 8th Annual National
Conference on Radiation Control
May 2-7, 1976
Springfield, Illinois
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INTRODUCTION
The Office of Radiation Programs (ORP) began its national study of
the phosphate industry in June, 1974. Since that time we have conducted
extensive environmental sampling, analyzed hundreds of specimens, and
performed numerous calculations and modeling tasks. This work has all
been directed toward comprehensively characterizing the radioactivity
source terms, assessing the resultant public health and environmental
impact, and determining the adequacy of existing standards and controls.
Throughout this period, whenever I was asked why the Office of Radiation
Programs is investigating the phosphate industry, I frequently noted some
*.
cynicism or at least skepticism in the inquirer's mind. In fact, you
could almost hear them say, the phosphate industry doesn't operate any
nuclear reactors, x-ray equipment, or have any involvement in the produc-
tion or use of medical isotopes, how could they possibly cause any adverse
radiological impact on the environment. Unfortunately, this is the atti-
tude many people have been taking toward man's alteration of the natural
radioactivity environment over the years. Of course, the phosphate indus-
try doesn't manufacture any radionuclides or radiation producing equipment.
However, the industry does annually redistribute in the environment
t
massive quantities of naturally-occurring radionuclides through its
products, by-products, and wastes. But that is background, you say,
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2
primordial radionuclides, there is nothing you can do about it. Indeed,
the industry redistributes only naturally-occurring radionuclides, but
whether the resultant environmental levels should be considered normal
background and whether it is controllable, are areas where a new perspec-
tive is needed nationwide. The phosphate industry is not the only group
that mines or otherwise processes large amounts of naturally-occurring
radionuclides. Numerous others including the titanium, coal, and even
building materials industries also belong to this category. Their
potential impacts will be discussed later. For now, let us focus more
closely on the phosphate industry.
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PHOSPHATE INDUSTRY OVERVIEW
The mining of phosphate rock began in the United States in 1867,
when a few tons of marketable rock were produced in South Carolina. Since
that time, the phosphate industry in the United States has experienced
tremendous growth. In 1974, the total U.S. production of marketable phos-
phate rock was about 46 million tons which had a market value of about
500 million dollars (1). At the present, the U.S. marketable phosphate
rock production accounts for about 40 percent of the total world produc-
tion. About 30 percent of the U.S. production is annually exported to
various countries around the world to improve crop yields. The richest
U.S. phosphate deposits are in the form of marine phosphorite. These are
located in Florida, North Carolina, Tennessee, and the Phosphoria Forma-
tion of Idaho, Montana, Utah, and Wyoming and depicted in Figure 1.
It has been recognized for several years that phosphate deposits
throughout the world contain appreciable concentrations of radioactive
material originating from the decay of uranium and thorium present in
the ores. Previous studies of the variability of concentrations of natu-
ral uranium and thorium in the phosphate ores produced in the United
States indicate that they range from 8 to 399 ppm (5.4 to 267 pCi per
gram) and 2 to 19 ppm (0.4 to 4 pCi per gram), respectively (2). The
highest concentrations were reported in South Carolina phosphate and the
lowest were in Tennessee phosphate rocks.
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FIGURE 1
UNITED STATES PHOSPHATE DEPOSITS
81%
AREA UNDERLAIN BY PHOSPHATE
OUTCROP OF PHOSPHATE BEDS
- PERCENT OF U.S. MARKETABLE PHOSPHATE
ROCK PRODUCTION IN 1974
SOURCES OF INFORMATION
MINERALS YEARBOOK -1974, USBM
FINAL EIS PHOSPHATE LEASING ON
THE OSCEOLA NATIONAL FOREST, FLORIDA 1974
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5
Generally, the uranium daughters in the ores, at least through
radium-226, have been shown to be in secular equilibrium. Figure 2 illus-
trates the uranium decay series. To date, most of the scientific work
that has been performed regarding radioactivity in phosphate related
materials have been focused on determining the uranium concentration in
the various phosphate formations. These studies were sparked by the quest
for sources of refinable uranium usable in the nuclear power industry or
for weapons production. Little emphasis has been placed on the health
physics or environmental radioactivity aspects of the various industry
operations. However, additional studies have recently been initiated by
industry sponsored groups and other governmental groups that should be
complementary to the study presently underway in.the Environmental Protec-
tion Agency.
Table 1 compares the total uranium and radium-226 extracted from the
earth by the phosphate industry to that from the uranium mining industry.
Since the beginning of each of these mining industries, the phbsphate
industry has mined the equivalent of 321 thousand tons of U^CL, whereas,
the uranium industry has mined the equivalent of 270 thousand tons (3,4).
While the concentration of uranium and other radionuclides in uranium
industry ores are generally about ten to twenty times those found in the
phosphate industry, both groups have been adding large, comparable quan-
tities of naturally-occurring radionuclides into the biosphere. The
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FIGURE 2
URANIUM - 238 DECAY SERIES
ATOMIC WGT.
ELEMENT
ATOMIC NO.
HALF-LIFE
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7
majority of the.phosphate rock mining in the U.S. has occurred in Florida,
where about 87 percent of the total U.S. output was produced in 1974.
Whereas, the total production of ore for the uranium mining industry has
been distributed'through several western States, with primary production
from the Colorado Basin area. New Mexico has been the State providing
the most uranium ore with cumulative production of about 40 percent of
the total. Clearly, from these comparisons, a substantial quantity of
natural radionuclides have been distributed through the Florida environ-
ment. Therefore, the EPA study has focused particular attention on
assessing the industry's impact on Florida.
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TABLE 1
HISTORICAL COMPARISON OF QUANTITIES OF URANIUM AND RADIUM 226 EXTRACTED BY
THE U.S. URANIUM AND PHOSPHATE MINING INDUSTRIES
INDUSTRY
PHOSPHATE
MINING
INDUSTRY
MINE
ROCK
MARKETABLE
ORE
URANIUM MINING
INDUSTRY
SHORT TONS OF ORE
(x 10*J
TOTAL THRU
1964
1710
531
58
TOTAL THRU
1974
2840
880
147
SHORT TONS OF U3 O8
(x 103|
TOTAL THRU
1964
193lb.c.
56'b'cl
147
TOTAL THRU
1974
321lb.c»
go(b.e,
270
CURIES OF RADIUM 226
(x 103)
TOTAL THRU
1964
50">
14le»
38"»
TOTAL THRU
1974
83(a)
23'"
69«"»
(a) ASSUMING EQUILIBRIUM WITH THE URANIUM-238 PARENT.
(b) ASSUMING A URANIUM CONCENTRATION OF 120 PPM.
(c) NO CONTRIBUTION WAS INCLUDED FOR TENNESSEE ORE.
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PHOSPHATE MINING AND BENEFICIATION
Florida land-pebble phosphate deposits are characterized by pebbles
and fine phosphatic sand dispersed in a nonphosphatic sandy clay. This
matrix, varying in thickness from 1 to 50 feet but averaging about 16
feet, is covered by an overburden of quartz sand and clay that averages
20 feet in thickness (5).
The standard mining practice in the Florida land-pebble phosphate
fields is to strip the overburden and mine the phosphate matrix with drag-
lines as shown in Figures 3 and 4. Electric-powered walking draglines
with 35 to 70 cubic yard buckets work in cuts varying from 150 to 250
feet in width and from a few hundred yards to a mile or more in length.
The cuts are from 50 to 70 feet deep. Overburden is stacked on unmined
ground adjacent to the initial cut by means of a dragline, until succes-
sive cuts allow it to be cast into adjacent mined-out cuts. As each cut
is stripped of overburden and then mined, the ore is stacked in a suction
well or sluice pit that has been prepared on unmined ground. High pres-
sure water is used to produce a slurry of about 40 percent solids from
the matrix. This slurry is then pumped via pipe to the washer plant.
In this manner, a typical operation will mine about 400 acres of land
per year, remove 13 million cubic yards of overburden, and mine 9 million
yards of matrix per year.
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;/> ;.v-* ;,v/
FIGURE 3
DRAGLINE STRIPPING OVERBURDEN
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:.: :'(£*." WaV-*7XH
"** ~* .. j'fr ?».- '-v-:; - j- -* ^'^ **4
*v: *> >. s. ~*y- r > a***. ,v:< ^: .-- .-^'-?
>_ «L-i .' ^ i ' . ^ '-ff> tJ!v-.=^.- ~ ^ <3L *
FIGURE 4
DRAGLINE BUCKET REMOVING MATRIX
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12
Similar wet mining techniques are used to extract phosphate rock in
North Carolina. However, in Tennessee and the western States, dry mining
techniques are employed in which the mined rock is transported to the
beneficiation plant or mill by trucks or rail cars.
While a sizable portion of the rock mined in the western States can
be utilized directly in mills without upgrading the P20g percentage, most
of the Florida and North Carolina ores require beneficiation (i.e., increas-
ing the PpCL content by physical separation). The flow diagram for
materials movement to and from a typical Florida beneficiation facility
is shown in Figure 5. The numbers in boxes are the uranium-238 concen-
trations and the numbers in ovals are radium-226 concentrations for the
respective input and output materials (6). Table 2 presents the estimated
total activities of radium-226 and uranium-238 present in the mine rock
and beneficiation plant products based upon the concentrations in
Figure 5 and 1974 U.S. production data. Of the total radium-226 and
uranium present in the 1974 Florida beneficiation plant products and
wastes, approximately 42% was in the marketable rock, 48% was in the
slimes, and the remainder was in the sand tailings.
In beneficiation, water 1s used for processing 1n addition to being
used as a transportation medium. Both fresh water from deep wells and
reclaimed water from slime settling ponds are used by the phosphate
industry. Approximately 10,000 gallons of water are necessary to produce
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SLIMES (TO SLIME POND)
PHOSPHATE MINE
BENEFICIATION
PLANT
MARKETABLE
PHOSPHATE
ROCK
SAND
TAILING (TO TAILINGS PILE)
URANIUM - 238 CONCENTRATION (pCi/GRAM)
RADIUM - 226 CONCENTRATION (pCi/GRAM)
FRACTION OF THE TOTAL INPUT MINE ROCK TO THE BENEFICIATION PLANT
FIGURES
TYPICAL FLORIDA PHOSPHATE MINING AND BENEFICIATION OPERATION
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TABLE 2
ESTIMATED TOTAL RADIUM-226 AND URANIUM 238 ACTIVITIES IN
FLORIDA PHOSPHATE MINE PRODUCTS AND WASTES FOR 1974
MATERIAL
MINE ROCK
MARKETABLE
ROCK
SLIMES
SAND(b)
TAILINGS
TOTAL
1974 PRODUCTION
(x 106 TONS)
142.1
37.0
39.0
60.1
136.1
RADIUM-226
(CURIES)
*
1398
1590
409
3397
URANIUM 238
(CURIES)
1387
1569
289
3245
(a) BASED ON 2110 POUNDS OF SLIMES PRODUCED PER TON OF PRODUCT
(b) BASED ON 3250 POUNDS OF SAND TAILINGS PRODUCED PER TON OF PRODUCT
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15
one ton of marketable phosphate rock. As the mining progresses, mined-
out areas are used for the disposal of tailings and slimes, in addition
to overburden. Some of the sand tailings and overburden is used to con-
struct retaining dams in mined-out areas, behind which phosphatic clay
slimes settle and dewater.
Several slime ponds have discharges to the environment. The discharge
quantities depend upon the facility's degree of recycle, overall water
consumption, and local precipitation. Since most of the radioactivity in
the waste products of beneficiation is present in the slimes,, this could
pose potential problems to receiving streams if the radioactivity was not
removed prior to discharge. To examine this aspect, the concentration
of radium-226 was determined for slime discharges and effluent discharges
from seven mine and beneficiation plants. This data is illustrated in
Table 3. The concentration of dissolved radium-226 in slime discharges
was less than 5.0 picocuries per liter at all seven facilities. The con-
centration of radium-226 in the undissolved fraction varied greatly and
was highly dependent on the total suspended solids in the slime discharge.
The radium-226 concentrations in picocuries per gram of the undissolved
fraction at all seven facilities are in the same order of magnitude
emphasizing the importance of the total suspended solids concentration
in determining the total concentration of radium-226 in picocuries per
liter in the slime discharge. Although no chemical process is used to
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16
treat the discharge from the slime ponds, low dissolved radium-226
concentrations were observed in the effluents. This is attributed to
the generally low dissolved radium-226 concentrations in the slime
discharge.
Table 3
RADIUM-226 CONCENTRATIONS IN PHOSPHATE MINE EFFLUENTS
FACILITY
1
2
3
4
5
6
7
HEAVY SLIME DISCHARGE
DISSOLVED
pCi/LITER
0.82
4.8
2.0
0.6
22
1
0.95
UNDISSOLVED
pCi/LITER
102
1074
97.6
37.7
520
2248
725.5
pCi/gm
21,3
72.6
30.5
9.8
52.0
33.6
15.0
EFFLUENT DISCHARGE
DISCHARGE
POINT
A
B
C
A
A
A
-
-
A
DISSOLVED
pCi/LITER
0.66
0.52
0.68
0.02
0.34
2.2
0.24
-
-
1.01
UNDISSOLVED
pCi/LITER
026
0.28
028
0.56
1.1
0.74
0.74
-
-
0.14
pCi/gm
17.3
21:5
18.7
31.1
52.4
385
28.5
-
-
7.0
The total concentration of racfium-226 in every effluent discharge
sample analyzed was less than 3.0 picocuries per liter. Comparison of
the slime discharge and effluent discharge concentrations indicate that
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17
no specific reduction in soluble radium-226 is predictable from the data
obtained at the seven facilities. This is understandable since present
»
treatment of the slimes involves only settling of solids and consequently
no appreciable precipitation of soluble radium-226 would be expected.
The reduction of total radium-226 from the slime discharge to the efflu-
ent discharge ranged from 92% to greater than 99.9% in the facilities
studied. This was primarily due to removal of suspended solids containing
large amounts of radium-226. Therefore, because of the significance of
the contribution of the radium-226 contained in the suspended solids to
the total concentration of radium-226 observed in either the slime or
effluent discharge, great reductions in suspended solids levels between
the slime discharge and the effluent will result in corresponding
reductions in radium-226 concentrations.
4
Based on this information, it is concluded that practicable control
technology is available to readily limit total radium-226 discharges to
surface waters to less than 3-4 pCi per liter. Actual .estimation of
population dose resulting from such a discharge will depend upon the
total discharge, the stream characteristics, the number of mines dis-
charging to the stream, and the downstream population using it for potable
water. Recognizing these parameters, it is highly unlikely that dis-
charges from mines would result in radium-226 concentrations greater
than 0.25 pCi per liter above normal to downstream users (7).
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18
PHOSPHATE MILLING AND MANUFACTURING
The marketable phosphate rock can be processed by either of two
types of facilities, the wet process phosphoric acid plant or the elec-
tric furnace plant.
Wet Process Phosphoric Acid Plants
In the wet process phosphoric acid plant, the raw materials are
ground phosphate rock, 93 percent sulfuric acid, and water. Phosphate
rock is mixed with the sulfuric acid after the acid has been diluted with
water. This reaction produces phosphoric acid and gypsum. Following the
reaction in the attack vessel, the mixture is filtered to separate the
gypsum from the phosphoric acid (approximately 30 percent P?^* ^e
gypsum is pumped as a slurry to a large pile near the facility where it
is allowed to dewater (refer to Figures 6 and 7). Since approximately
4.5 tons of gypsum are produced per ton of phosphoric acid, a Targe
phosphoric acid plant would produce about 2.7 million tons of gypsum per
year. .
The two other major products are triple superphosphate and ammonium
phosphate fertilizers. Triple superphosphate is produced by reacting
phosphoric acid and ammonia. All of these processess are graphically
presented in Figure 8 along with their corresponding radioactivity
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FIGURE 6
GYPSUM SLURRY RELEASED AT THE
TOP OF THE GYPSUM PILE
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$?$£'''fjfKA*'.} * '-fk'-"'ni(-' '!
m:Mmm^
FIGURE 7
GYPSUM SLURRY DEWATERING
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21
concentrations. The numbers in boxes indicate the radium-238
concentrations and the numbers in ovals are the radium-226 concentrations
in each material.
Gross radioactivity balancing of the input phosphate rock and the
product phosphoric acid and phosphogypsum indicates that approximately
one percent of the radium-226, and 80 percent of the uranium is dissolved
during the acidulating by sulfuric acid. The numbers are quite similar
to radium-226, uranium, and thorium dissolution by the acid leach process
of milling uranium ore (8). This is not surprising since similar tech-
niques and chemicals are used in both industrial processes.
Individual samples of phosphoric acid displayed a great variation
of radium-226 concentration ranging from a few hundred to greater than
one thousand picocuries per liter. The variation was not observed to be
a function of solids content or P^Og concentration. The average of seven
phosphoric acid samples was 840 pCi/liter of radium-226. This translates
to a concentration of less than one pCi per gram of 52% phosphoric acid,
whereas uranium concentration was about 51,000 pCi per gram.
Ammonium phosphates (DAP and MAP) were observed to have radium-226
concentrations of about 5 pCi per gram. Uranium concentrations were a
factor of 10 greater than the radium-226 concentrations. The relatively
low radium-226 concentration and much higher uranium concentration is
attributed to the fact that production of ammonium phosphates uses only
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22
ammonia and phosphoric acid with no direct reaction with phosphate rock.
Consequently, the bulk of the'radioactivity introduced to the reaction
comes from the phosphoric acid which is enriched with uranium and defi-
cient in radium-226 due to the partition by removal of the phosphogypsum.
Triple superphosphate (TSP) contained about 4 times as much
radium-226 and about the same concentration of uranium as ammonium phos-
phate fertilizer. This is because triple superphosphate is produced by
acidulating phosphate rock with phosphoric acid. Therefore, the product
triple superphosphate would be expected to display comprise activities
in the reactants, phosphate rock and phosphoric acid, which display
markedly different radium-226, and uranium concentrations.
In order to estimate the total activities of radium-226 and uranium
in the wet process phosphoric acid plant products and by-products, 1973
production data (1974 data is not yet available) was obtained and used in
conjunction with the material radioactivity concentrations shown in
Figure 8. The resulting total activity estimates are shown in Table 4 (9).
Approximately 80% of the product radium-226 activity is contained
in the phosphogypsum. Although the radium-226 concentrations of normal
superphosphate and triple superphosphate are similar to that of the phos-
phogypsum, the bulk magnitude of the phosphogypsum produced is sufficient
to outweigh the individual contributions of the other products (10).
Phosphoric acid contributes a major portion of the total uranium activity.
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1 41 |
MARKETABLE /-N ^
PHOSPHATE (42)
ROCK ^-^
MARKETABLE
SULFURIC
ACID
DIGESTOR 1 J FILT
PHOSPHORIC
ACID
1 41 |
I 1
o 1
FRI _,,i
|51,000|
(840)
__w, TO rsvi
AMMONIA
MIXER
MIXER
i
PSUM PILE
I 59 I
V AMMONIUM
~ PHOSPHAlb
©
| 58 |
_ ., M.,^ TRIPI F
^^ ^ SUPERPHOSPHATE
PHOSPHATE
ROCK
42
| | - CONCENTRATION OF URANIUM - 238 (pCI PER GRAM)
- CONCENTRATION OF URANIUM - 226 (pCi PER GRAM)
EXCEPT PHOSPHORIC ACID CONCENTRATION IS
EXPRESSED AS pCi PER LITER.
FIGURES
PRODUCTION FLOWSHEET FOR A WET-PROCESS PHOSPHORIC ACID PLANT
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TABLE 4
ESTIMATED TOTAL RADIUM-226 AND URANIUM-238 ACTIVITY IN PHOSPHATE
FERTILIZER PRODUCTS AND BYPRODUCTS BASED ON 1973 PRODUCTION DATA
MATERIAL
NORMAL
SUPERPHOSPHATE
TRIPLE
SUPERPHOSPHATE
AMMONIUM
PHOSPHATES
PHOSPHORIC
ACID
GYPSUM
PRODUCTION
(x 106 JONS)
3.4
3.7
5.8
11(0
25.3
(x 106 JONS P2O$)
0.62
1.72
2.67
5.62
RADIUM-226
(CURIES)
77
69
30
5.5
760
URANIUM-238
(CURIES)
77
190
330
600
140
(a) WET PROCESS PRODUCTION USING FLORIDA ORE
(b) BASED ON 4.5 TONS GYPSUM PER TON P2O5
(c) ASSUMING 50 PERCENT P2O5 ACID
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25
It is emphasized that the columns are not directly additive to
determine the total radioactivity in the products because some of
the activity reflected in the phosphoric acid is also accounted in
the ammonium phosphate and triple superphosphate estimates because
phosphoric acid is used to produce these products. From these
estimates, it is evident that a sizable inventory of radioactivity
is present in the phosphoric acid plant products and by-products.
About 80% of the marketable phosphate rock used in the U.S.
goes into the production of fertilizer. Estimating the amount of
radioactivity distributed through the various regions of the United
States is difficult because these primary phosphate fertilizers are
frequently mixed and blended to form a variety of commercial ferti-
lizers. It is difficult to trace these blends to determine if they
originated from normal superphosphate, triple superphosphate, ammo-
nium phosphate, or phosphoric acid. Recognizing the information
deficiency in estimating radioactivity distribution among the States,
the approximate amount of distribution can be inferred from Table 5
which gives the 1974 U.S. phosphate fertilizer consumption by State.
The total U.S. consumption was about 5.7 million tons PO^C- Approx-
imately 52 percent of this was ued in the north central States, thus
emphasizing the potential in that region for crop uptakes and soil
runoff to surface and ground waters (11).
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Table 5
1974 U.S. Phosphate Fertilizer Consumption by State
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
State
Illinois
Iowa
Texas
Indiana
Ohio
Minnesota
Missouri
California
Kansas
Georgia
North Carolina
Michigan
Wisconsin
Nebraska
Alabama
North Dakota
Kentucky
Oklahoma
Florida
Pennsylvania
Tennessee
New York
Mississippi
Arkansas
South Carolina
Thousand Tons
P2°5
478
398
296
292
271
268
189
183
176
153
152
148
139
136
113
110
108
105
104
93
91
90
88
80
75
Rank
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
i
- State
Washington
Idaho
Virginia
Louisiana
South Dakota
Montana
Maryland
Oregon
Colorado
Arizona
New Jersey
Utah
Maine
Delaware
New Mexico
Hawaii
West Virginia
Puerto Rico
Wyoming
Vermont
Massachusetts
Connecticut
Rhode Island
Nevada
New Hampshire
Alaska
Thousand Tons
P2<>5
71
69
69
69
62
61
45
45
44
36
20
19
18
16
16
16
10
9
8
7
7
5
3
2
2
.4
TOTAL 5070
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27
Turning from the products back to the environmental aspects around
the phosphoric acid plant, we find that each wet process phosphoric
acid plant incorporates a large cooling pond (^500 acres) of contaminated
water for recycle in the plant. During periods of excess rainfall it
becomes necessary to discharge water from these ponds to nearby streams.
Field studies were conducted at several such facilities to determine
the extent to which the discharge practices introduced radioactivity to
the surface streams. Raw process water was found to contain from 55 to
86 pCi per liter total radium-226 and from 400 to 1825 pCi per liter of
uranium-238. This data showed that in the process waters radionuclides
were substantially out of equilibrium. This is because the uranium was
dissolved preferentially over radium-226 by the acidulation and filtra-
tion step where the uranium entered the process water.
«
To prepare process water for discharge to the environment, the pH
of the water must be increased from its normal 1.5 - 2.0 to 6-9. To do
this, slaked lime is normally added to the discharge water in a step
called "double liming." Our studies have shown that this treatment is
highly effective in removing radionuclides from the discharge. Radium-
226 removal of greater than 96 percent was observed in all situations
studied. Corresponding reductions in uranium and thorium were also fou nd.
Therefore, use of this treatment allows minimization of radionuclides
entering the environment through liquid discharges.
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28
Elemental Phosphorus Facilities
In the thermal processing of phosphate rock, silica and coke are
added and this mixture is electrically reduced to form elemental phos-
phorus. Ferrophosphorus and calcium silicate slag by-products are also
produced in this process. Present data indicates that most of the radio-
activity enters this facility in the phosphate rock and leaves the
facility in the slag. Figure 9 illustrates radium-226 concentrations in
materials at an elemental phosphorus plant using Florida ore. Although
the data is yet incomplete, there are indications that significant
quantities of Po-210 may be emitted from these facilities during calcining
or furnace operations. In this respect, calcining operations at wet pro-
cess phosphoric acid plants may also be volatilizing Po-210 and releasing
it to the environment.
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FIGURES
PRODUCTION FLOWSHEET FOR ELEMENTAL PHOSPHORUS FACILITY*
(THE SIZE OF THE ARROWS DEPICT THE APPROXIMATE MATERIALS MASS FLOW)
COKE
MARKETABLE
PHOSPHATE
ROCK
o
SILICA
ELEMENTAL
PHOSPHORUS
(P4)
ELEMENTAL
PHOSPHORUS
FACILITY
FERROPHOSPHORUS
(FEP)
CONCENTRATION OF RADIUM 226 (pCI PER GRAM)
* - UTILIZING FLORIDA PHOSPHATE ROCK
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30
RECLAIMED PHOSPHATE LAND
On the basis of the Agency's past experience evaluating the use of
uranium mill tailings as a construction material, it was believed that
structures built on reclaimed phosphate lands which contain elevated
radium-226 concentrations could pose potential indoor radon problems.
Therefore, to evaluate this aspect, in June 1975, the Office of Radiation
Programs in conjunction with the Florida Department of Health and Reha-
bilitative Services and the Polk County Health Department, began a study
to determine the radiological significance of living and working in such
structures. Preliminary data from this study showed elevated indoor
radon daughter levels in some structures built on reclaimed lands as com-
pared to structures built on unmined soil (12). As data is continuing to
be evaluated, the existence of elevated levels in some of these structures
is being supported. The data on these structures is compared to the
Surgeon General's Guidelines in Table 6. In this respect the Surgeon
General's Guidelines are used only as an evaluation tool and not as an
applicable standard (13).
As a result of the Agency's preliminary data, the Administrator
recommended to the Governor of Florida that "as a prudent interim measure
that the start of construction of new buildings on land reclaimed from
phosphate mining areas be discouraged." .
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31
Table 6
FLORIDA INDOOR RADON DAUGHTER LEVELS
AS COMPARED TO THE SURGEON GENERAL'S
(FEBRUARY 1976)
RECLAIMED LAND STRUCTURES (N -12)
l ,05 WL : 53-1/3%
,05>x> ,01 WL : 33-1/3%
< ,01 WL : 33-1/3%
NGN-RECLAIMED LAND STRUCTUES (N = 9)
1 ,05 WL : 0
,05 > x L ,01 WL :r 22
< ,01 WL :
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32
The Environmental Protection Agency is presently acquiring
information for the development of an acceptable radiation guide
applicable to the Florida situation. An easy method of field
measurement is also needed for evaluating undeveloped land in order
to judge whether structures built on the land would be within the
radiation guide. To accomplish this latter objective, a correlation
is necessary between indoor radon daughter levels and some readily
s
measurable parameter, such as external gamma radiation levels, the
soil radium-226 concentrations, or the-emanation rates of radon-222
from the soil. Until a final acceptable radiation guide and a
correlation are established, the Agency has recommended the use of
an interim guide. This interim guide will enable screening of
proposed construction sites to determine their likelihood of posing
radon daughter problems in structures built on them.
The interim recommendations were conservatively based on the
Agency's present data which is shown in Figure 10, information
obtained from investigators of the potential hazard associated with
the use of uranium mill tailings in several western States, and
consideration of the Surgeon General's Guidelines for remedial
action in Grand Junction, Colorado (14). The interim recommenda-
tions provided to the State of Florida were as follows:
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33
INTERIM RECOMMENDATIONS FOR GAMMA EXPOSURE LEVELS
AT NEW STRUCTURE SITES ON FLORIDA PHOSPHATE LANDS
Average External Gamma
Radiation Level Recommendations
Equal or greater than 10 yR/hr Construction should be delayed
pending study or acceptable control
technology should be instituted to
preclude indoor radon daughter
problems.
Less than 10 yR/hr Construction may be initiated.
-------
1.0
.1 -
3
ui
ui
oe
ui
D 0.01.
<
o
I
oe
oc
o
i
0.001
0.0001
X-HIGH VENTILATION
LOCATIONS
I
I
10 20 30
OUTSIDE AVERAGE GAMMA LEVELS
40
FIGURE ID OBSERVED INDOOR RADON DAUGHTER LEVELS AS A FUNCTION
OF OUTDOOR AVERAGE GAMMA RADIATION LEVELS FOR DATA
COLLECTED AS OF FEBRUARY 1976.
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35
OTHER PHOSPHATE ISSUES
This paper has addressed the major aspects of the phosphate industry
which the Office-of Radiation Programs has studied and evaluated to date.
Other aspects which we are now addressing or will investigate in the
future include:
1. The positive and negative environmental impact of uranium recov-
ery from phosphate materials as well as the potential increase in uranium
reserves.
2. The radiological impact of using phosphate by-products as con-
struction materials.
3. The uptake of radionuclides by selected crops due to fertilizer
usage or growing on reclaimed lands.
4. The impact of polonium-210 and other radionuclides through the
atmospheric pathway.
The results of these studies will determine the need for additional
radiation protection standards and guides in these areas.
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36
OTHER INDUSTRIES REDISTRIBUTING
NATURALLY RADIOACTIVE MATERIALS
As I previously noted, the presence of elevated concentration of
naturally occurring radionuclides is not unique to the phosphate industry.
Consequently, the Office of Radiation Programs has efforts directed at
the assessment of the environmental impact of other industries as well
as the development of standards and guides for these industries, where
appropriate.
In general, the industries potentially redistributing significant
amounts of naturally-occurring radionuclides can be grouped into three
categories:
1. Mineral extraction industries - these include the phosphate,
uranium, coal, titanium, copper, and rare earth mining and milling
industries.
2. Energy production industries - these include coal-fired power
plants and geothermal power plants.
3. Consumer oriented industries - these include construction mater-
ials, potable water, and selected uses of geothermal energy.
At the present time the primary focus of EPA's studies are in the
areas of uranium mining and milling, phosphate mining and milling, and
construction materials. However, increased attention is being directed
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37
toward western coal utilization, geothermal applications, and potable
water. Future efforts will be directed in these and other areas where
significant potential health problems can be demonstrated.
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38
References
1. Phosphate rock-1974, Mineral Industry Surveys, Bureau of Mines,
U.S. Department of the Interior, March 1975.
2. Menzel, F. G. Uranium, radium, and thorium content in phosphate
rocks and their possible radiation hazards, Journal of Agriculture
and Food Chemistry. Vol. 16, No. 2, pp. 231-234, 1968
3. Stowasser, W. F. Phosphate rock, 1974 Bureau of Mines Mineral
Yearbook, preprint, Bureau of Mines, U.S. Department of the
Interior, 1975.
4. Statistical data of the uranium industry, U.S. Energy Research and
Development Administration, Grand Junction Office, GJO-100 (75),
January 1975.
5. Wang, K. L., Klein, B. W. and Powell, A. F. Economic significance
of the Florida phosphate industry, pp. 3-5, Information Circulat
8653, Bureau of Mines, U.S. Department of the Interior, 1974.
6. Guimond, R. J. and Windham, S. T. Radioactivity distribution in
phosphate products, by-products, effluents, and wastes, Office of
Radiation Programs, Environmental Protection Agency, Technical
Note ORP/CSD-75-3, August 1975.
7. Interim radium-226 effluent guidance for phosphate chemical and
fertilizer manufacturing, Statement of considerations, Office of
Radiation Programs, Environmental Protection Agency, August 1974.
8. Sears, M. B., Blanco, R. E., Dahlman, R. C., Hill, G. S., Ryon,
A. D. and Witherspoon, J. P. Correlation of radioactive waste
treatment costs and the environmental impact of waste effluents
in the nuclear fuel cycle for use in establishing "as low as
practicable" guides - milling of uranium ores, Oak Ridge National
Laboratory, ORNL-TM-4903, Vol. 1, May 1975.
9. Stowasser, W. F. Phosphate rock, 1973 Bureau of-Mines;Mineral
Yearbook, Bureau of Mines, U.S. Department of the Interior, 1975.
10. Slack, A. V., editor. Disposal or use of gypsum, Phosphoric Acid,
Vol. I, Part II, 1968.
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39
11. Harre, E. A. Fertilizer trends-1973, National Fertilizer Develop-
ment Center, Tennessee Valley Authority, Muscle Shoals, Alabama,
Bulletin Y-77, June 1974.
12. Preliminary findings-Radon daughter levels in structures constructed
on reclaimed Florida phosphate land, Office of Radiation Programs,
Environmental Protection Agency, Technical Note ORP/CSD-75-4,
September 1975.
13. Code of Federal Regulations, Title 10, Part 12, Grand Junction
remedial action criteria, December 1972.
14. Letter to E. Carl ton Prather, M.D., Director, Division of Health,
State of Florida from W. D. Rowe, Ph.D., Deputy Assistant Admini-
strator for Radiation Programs, Environmental Protection Agency,
January 22, 1976.
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