Characterization of Radioactive Aerosols in Florida Phosphate Processing Facilities

Figures & data

FIG. 1 Series of processes in the Florida phosphate industry. Rectangular and oval elements of the chart represent, respectively, the type of process and the phosphate material at each process.

FIG. 2 The ²³⁸U decay series. The numbers in the parenthesis indicate the physical half-life of each radionuclide.

TABLE 1 ^a ICRP 66 ^b HRTM default aerosol parameters and input aerosol parameters for dose sensitivity study

Aerosol		Input parameters
parameters	ICRP default values	for dose calculation
Aerosol size	^c AMAD = 5 μ m (workplace)	AMAD = 0.01–100 μ m
	AMAD = 1 μ m (general public)
Distribution	log-normal distribution	GSD = 1 and GSDICRP66 ^2
	^d GSDICRP66 = 1 + 1.5[1 − (100 ^e AMTD^1.5+ 1)^− 1]
	GSD ICRP66 = 2.50 for AMAD = 5 μ m
	GSD ICRP66 = 2.47 for AMAD = 1 μ m
Density	3 g/cm^3	0.7 and 11 g/cm^3
Shape factor	1.5	1 and 2
Absorption type	^f Type M	Types ^g F and ^h S

FIG. 3 Aerosol size distribution. Capital letters in legend are plant identifiers. Plant A-a and Plant A-b refer to the same company plant (Plant A), but two different locations within the plant.

TABLE 2 Active operational systems and ventilation conditions during aerosol sampling at the various storage areas

^a Plant	Running system	Ventilation
A-a	Conveyor, Reclaimer	Closed
A-b(1)	None	Open
A-b(2)	Payloader	Open
B	Payloader	Open
C	Conveyor	Open
D-a	Reclaimer	Closed
D-b	Payloader	Closed
E	Payloader	Open
F	Payloader	Open

TABLE 3 Density of bulk products, settled dusts, and aerosols

Type of	Number of	Mean mass
sample	samples	density g/cm^3
Bulk product	11	1.72 ± 0.08
Settled dust	11	1.71 ± 0.07
Aerosol (< 100 μ m)	4	1.70 ± 0.06
Aerosol (< 10 μ m)	6	1.59 ± 0.07

FIG. 4 Shape of particles collected at granulator area in plant A. A: 1st impactor stage particles (scale is 50 μ m), B: 4th impactor stage particles (scale is 10 μ m), and C: 7th impactor stage particles (scale is 1 μ m).

FIG. 5 Energy Dispersive X-ray Spectroscopy (EDXS) count peak of airborne particles at storage area in plant A. A: large-size particles (1st impactor stage), B: medium-size particles (4th impactor stage), and C: small-size particles (7th impactor stage).

TABLE 4 ^a Chemical composition of dry products

		Component (w%)
Dry product	Chemical formula	N	P2O5	P	Other elements or compounds
MAP	NH4H2PO4	10∼ 11	50∼ 52	22	H2O, CaO, Fe2O3,
DAP	(NH4)2HPO4	18	46	20	Al2O3, MgO, SO4, Si

TABLE 5 Phosphorus, silicon, and sulfur composition in different size particles. The types of dry products generated in plants A and D are ^a MAP and ^b DAP, respectively

	Component (w%)
	Impactor	Plant A (MAP)			Plant D (DAP)
Area	stage	P	Si	S	P	Si	S
Granulator	1st				28.3	0.3	1.7
	4th				21.7	3.0	3.0
	7th				2.9	13.3	8.9
	1st	17.3	6.0	1.9	19.4	5.5	2.8
Storage	4th	13.2	2.9	0.4	24.1	0.3	2.2
	7th	0.7	10.7	13.0	21.5	0.3	7.4
	1st	25.9	1.3	1.5	27.3	2.4	4.3
Shipping	4th	26.6	1.5	2.0	12.3	2.5	7.1
	7th	2.5	5.7	19.3	1.7	13.4	21.9

TABLE 6 Radioactivity concentrations for ²³⁸U, ²²⁶Ra, and ²¹⁰Pb in bulk dry products, settled dust, and sampled aerosols smaller than 10 μ m. Mean and one standard derivation are given for n > 1

		Mean radionuclide concentration (pCi/g)
		DAP				MAP
Region	Sample	n	^238U	^226Ra	^210Pb	n	^238U	^226Ra	^210Pb
Central Florida	^a Published values		46.0–82.8	0.6–12.1			46.0–81.8	1.4–21.6
	Bulk product	4	90.2 ± 24.1	1.1 ± 0.6	6.7 ± 3.8	4	63.1 ± 10.3	1.5 ± 0.5	8.4 ± 4.4
	Settled dust	3	112.2 ± 28.3	0.8 ± 0.1	9.3 ± 3.2	4	70.9 ± 19.6	1.2 ± 0.5	9.0 ± 7.1
	Sampled aerosols	3	65.37 ± 17.0	1.85 ± 1.65	16.1 ± 9.5	1	49.8	2.56	62.51
	(≤ 100 μ m)
	Sampled aerosols	4	69.6 ± 22.2	2.5 ± 1.5	25.8 ± 7.4	1	55.1	3.8	86.61
	(≤ 10 μ m)
Northern Florida	^a Published values		25.3	0.5
	Sampled aerosols	1	35.72	1.2	17.26
	(≤ 100 μ m)
	Sampled aerosols	1	29.41	0.81	25.52
	(≤ 10 μ m)

FIG. 6 Effective dose coefficient of ²³⁸U for various aerosol parameters. The other parameters except those indicated in the legend follow ICRP 66 human respiratory tract model (HRTM) default values.

CF . 2003a . Material Safety Sata Sheet (Diammonium Phosphate) , Long Grove, IL : CF Industries, Inc .

 Google Scholar

CF . 2003b . Material Safety Data Sheet (Monoammonium Phosphate) , Long Grove, IL : CF Industries, Inc .

 Google Scholar

Mosaic . 2003b . Material Safety Data Sheet (Monoammonium Phosphate). , Riverview, FL : Mosaic Company .

 Google Scholar

Mosaic . 2003a . Material Safety Data Sheet (Diammonium Phosphate). , Riverview, FL : Mosaic Company .

 Google Scholar

PCS . 2003b . Material Safety Data Sheet (Monoammonium Phosphate). , Northbrook, IL : PotashCorp .

 Google Scholar

PCS . 2003a . Material Safety Data Sheet (Diammonium Phosphate). , Northbrook, IL : PotashCorp .

 Google Scholar

Guimond , R. 1978 . The Radiological Aspects of Fertilizer Utilization. , pp. 380 – 393 . Washington, DC : U.S. Nuclear Regulatory Agency . NUREG/CP-0001.

 Google Scholar

Roessler , C. E. , Smith , Z. A. , Bolch , W. E. and Prince , R. J. 1979 . Uranium and Radium-226 in Florida Phosphate Materials . Health Phys. , 37 : 269 – 277 . [INFOTRIEVE] [CSA]

 PubMed Web of Science ®Google Scholar

Owen , R. and Hyder , L. 1980 . Technologically Enhanced Naturally Occurring Radioactivity: An Overview. , Oak Ridge, TN : Oak Ridge National Laboratory . ORNL/CF-80/265.

 Google Scholar

NCRP . 1987 . Radiation Exposure of the U.S. Population from Consumer Products and Miscellaneous Sources. , Bethesda, MD : National Council on Radiation Protection and Measurements . Report No. 95.

 Google Scholar

Birky , B. , Tolaymat , T. , Warren , B. , Bolch , W. , Ammons , R. , McNally , T. and Nall , W. 1998 . Evaluation of Exposure to Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) in the Phosphate Industry , Bartow, FL : Florida Institute of Phosphate Research . FIPR Publication No. 05-046-155.

 Google Scholar