ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 24

Document Title:

Characterization of Occupational 

Exposure to Radium and Radon Progeny 

During Recovery of Uranium from 

Phosphate Materials

Document Number: ORAUT-OTIB-0043

Revision: 00

Effective Date: 01/06/2006

Type of Document: OTIB

Supersedes: None

Subject Experts: Gary R. Daer, Roger A. Gard, and Michalene Rodriguez 

Document Owner

Approval: Signature on File Approval Date: 01/06/2006

Elyse M. Thomas, Task 2 Manager

Concurrence: Signature on File Concurrence Date: 01/05/2006

Kate Kimpan, Project Director

Approval: Signature on File Approval Date: 01/06/2006

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR 

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 2 of 24

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION

NUMBER DESCRIPTION

01/06/2006 00 New document to describe characterization of occupational exposure 

to radium and radon progeny during recovery of uranium from 

phosphate materials. First approved issue. Training required: As 

determined by the Task Manager. Initiated by Gary R. Daer, Roger 

A. Gard, and Michalene Rodriguez.
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 3 of 24

TABLE OF CONTENTS

SECTION TITLE 

Acronyms and Abbreviations ...............................................................................................................

PAGE

5

1.0 PURPOSE ...............................................................................................................................6

2.0 BACKGROUND .......................................................................................................................6

3.0 LITERATURE REVIEW............................................................................................................7

3.1 Federal Sources ...........................................................................................................8

3.2 Florida Institute of Phosphate Research Study .............................................................8

 3.2.1 External Exposure.............................................................................................9

 3.2.2 Internal Exposure..............................................................................................9

 3.2.3 Radon Exposure ............................................................................................. 10

3.3 Scientific Publications.................................................................................................10

3.4 Other Reviews............................................................................................................11

4.0 OCCUPATIONAL EXPOSURE CHARATERIZATION............................................................ 11

4.1 Internal and External Exposure Considerations ..........................................................11

 4.1.1 External Exposure........................................................................................... 12

 4.1.2 Internal Exposure............................................................................................ 12

4.2 Radon Exposure.........................................................................................................13

5.0 INDIVIDUAL PROGENY EQUIBRIUM FRACTIONS AND UNATTACHED FRACTIONS....... 14

References ........................................................................................................................................16

ATTACHMENT A, SYNOPSIS OF PHOSPHATE PLANT DATA IN THE NIOSH SITE RESEARCH 

DATABASE ....................................................................................................................................... 18

ATTACHMENT B, DATA FROM FIPR (1998).................................................................................... 19
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 4 of 24

LIST OF TABLES

TABLE TITLE PAGE

4-1 Annual external exposure....................................................................................................... 12

4-2 Phosphate 238U activity concentrations................................................................................... 12

4-3 Internal deposition..................................................................................................................13

4-4 Phosphate plant worker radon WL values .............................................................................. 14

A-1 Synopsis of phosphate plant data in the NIOSH Site Research Database ............................. 18

B-1 Phosphate facility radon measurements................................................................................. 19

B-2 Annual exposure to radon progeny in wet rock loading .......................................................... 20

B-3 Chemical plant radon readings, summary statistics 1989 to 1994 .......................................... 20

B-5 Radon readings in rock tunnels, 1996 .................................................................................... 21

B-6 Radon readings in rock tunnels using e-perms, 1996............................................................. 22

B-7 Terradex radon measurements, summary statistics 1982 to 1996.......................................... 23

B-8 Chemical plant track-etch radon results, 1993 to 1996........................................................... 24

LIST OF FIGURES

FIGURE TITLE PAGE

3-1 Inhalation dose for the shipping area .......................................................................................9

3-2 Inhalation dose for the rock area............................................................................................ 10
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 5 of 24

ACRONYMS AND ABBREVIATIONS

AEC U.S. Atomic Energy Commission

ATSDR Agency for Toxic Substances and Disease Registry

AWE atomic weapons employer

Bq becquerel

DOE U.S. Department of Energy

EPA U.S. Environmental Protection Agency

FIPR Florida Institute of Phosphate Research

ft foot

g gram

HPS Health Physics Society

hr hour

keV kiloelectron volt, 1,000 electron volts

L liter

m meter

min minute

mrad millirad

mrem millirem

NCRP National Council on Radiation Protection and Measurements

NIOSH National Institute for Occupational Safety and Health

NORM naturally occurring radioactive material

pCi picocurie

TENORM technologically enhanced naturally occurring radioactive material

TIB technical information bulletin

U.S.C. United States Code

UNSCEAR United Nations Scientific Committee on the Effects of Atomic Radiation

WL working level

WLM working level-month

yr year

μR microroentgen
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 6 of 24

1.0 PURPOSE

Technical information bulletins (TIBs) are general working documents that provide guidance 

concerning the preparation of dose reconstructions at particular sites or categories of sites. They will 

be revised in the event additional relevant information is obtained. TIBs may be used to assist the 

National Institute for Occupational Safety and Health (NIOSH) in the completion of individual dose 

reconstructions.

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act of 2000 (42 U.S.C. § 7384l (5) and (12)).

This TIB characterizes occupational radiation exposure from the extraction of uranium during 

nonmonazite phosphate processing at atomic weapons employer (AWE) facilities. Exposure models 

and associated data have been acquired and/or extrapolated from existing published scientific 

research and Federal studies.

2.0 BACKGROUND

Phosphate rock extraction is the fifth largest U.S. mining industry in terms of quantity of mined 

material. Florida produces approximately 80% of the domestic capacity. North Carolina and 

Tennessee generate 10%, and Idaho, Utah, Montana, and Wyoming combine to produce the 

remaining 10%. The method chosen to handle the rock and ore depends on the desired final 

product—elemental phosphorous, gypsum, or fertilizer. The treatment type determines the innate 

physical, chemical, and radiological characteristics of the material including the distribution and 

concentration of naturally occurring radionuclides (such as uranium) within the matrix of the product or 

waste stream. In this manner, phosphate mining and processing effectively redistribute a significant 

fraction of uranium and its progeny within various phosphate products and byproducts, which results

in what is commonly known as technologically enhanced naturally occurring radioactive material 

(TENORM). Phosphate ore from Florida typically contains the highest concentration of uranium, 

which is about 0.01% 238U (in contrast to uranium ore, which contains up to 10% 238U). In addition, 

phosphate ores contain concentrations of 232Th consistent with those found in soil.

Phosphate ore is processed by either dry thermal or wet acid methods. The thermal approach

produces elemental phosphorous using an electric arc furnace. The byproduct material is a vitrified 

slag containing uranium and 226Ra. Concentrations of uranium and 226Ra entrained in the slag range 

from 20 to 50 pCi/g and 4 to 40 pCi/g, respectively (Egidi 1997). The wet chemical phosphoric acid 

treatment process on the other hand primarily produces phosphate fertilizers whose principal 

byproducts are phosphogypsum and phosphoric acid scale. During wet chemical processing, there is

selective separation and concentration of naturally occurring radium and uranium; nearly 80% of the 

226Ra is concentrated in the phosphogypsum while approximately 86% of the uranium ends up in the 

phosphoric acid scale (Egidi 1997). For work contracted under the auspices of the weapons program, 

only the wet acid treatment process was used to recover uranium from phosphate ores. Sites such as 

the Tennessee Valley Authority and Virginia-Carolina Chemical Company are known to typically 

employ the dry thermal methods for processing phosphate ores. However, under AWE contract, 

these sites employed wet process techniques to perform research and development efforts for 

extracting uranium from phosphate ores. The R & D efforts were performed using pilot plants which 

were conducted on a completely separate basis from the arc furnace facilities. 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 7 of 24

Typical phosphate plant operations consist of mining and beneficiation (separation of ore from sand 

and clay), ore drying and grinding, and acid processing. The majority of phosphate mining operations 

used strip mining. A typical strip mine is a trench 10 m deep and 99 m wide. The phosphate ore 

consists of rock and pebble embedded in a sand and clay matrix. During beneficiation, the sand and 

clay are separated from the phosphate rock. At the drying and grinding facility, the phosphate ore is 

reduced to pebbles in preparation for the acid wash. This process generates large quantities of dust

and poses the highest potential for radon exposure in the phosphate industry (Birky 2005a). The 

phosphate is then transported to the acid facility where it is reacted with sulfuric acid to make 

phosphoric acid, typically to produce fertilizers. Because of the natural abundance of uranium in 

phosphate ore, some sites adjusted their processes to add steps to chemically precipitate uranium 

from phosphoric acid. For those sites that extracted uranium under a U.S. Atomic Energy 

Commission (AEC) contract, product packing also generated airborne particulate. Due to the nature 

of plant operations, workers were frequently in close contact with large amounts of ore, products, and 

wastes that contained TENORM and radium as well as their concomitant alpha-emitting progeny such 

as radon. 

An inert gas, radon decays as a series of short-lived radionuclides that can attach electrostatically to 

aerosols. As mentioned above, plant operations generate large quantities of particulate (especially 

during loading, unloading, crushing, and drying activities), so there is a potential for elevated levels of 

airborne radionuclides in the work environment. Mitigating factors such as environmental conditions 

(ambient dust levels, etc.) and ventilation notwithstanding, it is likely that phosphate plant workers 

spent some fraction of their shifts exposed to airborne particulates that resulted in a corresponding 

occupational radiation exposure from inhalation of long-lived alpha-producing radionuclides as well as 

radon and its progeny. 

Around 1950, the AEC was interested in developing methods for recovering uranium from 

low-concentration sources such as phosphate rock (Wilkinson 1976). In addition to its potential use 

as a nuclear fuel source, uranium was a key component of the early weapons production program. A 

review of the U.S. Department of Energy (DOE) Office of Worker Advocacy on-line facilities database 

revealed that there were efforts to recover uranium from phosphate byproducts at the following AWE 

sites: Allied Chemical and Dye Corporation, Armour Fertilizer Works, Blockson Chemical Company, 

Dow Chemical Company (Pittsburg, California), Gardinier Incorporated, International Minerals and 

Chemical Corporation, Mathieson Chemical Company, Tennessee Valley Authority, Texas City 

Chemicals Incorporated, Virginia-Carolina Chemical Corporation, and W.R. Grace Company, 

Agricultural Chemical Division. Each facility is described as having been under contract with the AEC 

to investigate methods to produce uranium from phosphoric acid. Resultant worker exposure to 

TENORM and its long- and short-lived progeny during wet chemical phosphate production activities at 

these plants are of particular interest.

3.0 LITERATURE REVIEW

Initial efforts for this bulletin focused on the collection of existing data that addresses the radiological 

hazards associated with uranium-mining activities and the recovery of uranium during phosphate 

production. The goal was to construct a technically defensible, claimant-favorable method for 

characterizing worker exposure to radon progeny during AEC uranium extraction operations. 

Preference was given to documents that addressed wet chemical phosphate production in Florida 

because the radiological characteristics of the ore, the production methods, and the techniques 

employed to extract the uranium determine the radiological source term and, correspondingly, 

establish the basis for potential occupational dose during work activities performed under AWE 

contracts. 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 8 of 24

Adequate quantification of radiation exposure to workers necessitates detailed characterization of the 

work environment as well as specific sources of external and internal radiation. In addition, data that 

directly support radiological characterization (source information, monitoring results, discrete process 

exposures, etc.) and information on models used to estimate radon and radon progeny levels were 

considered important criteria for the literature review. Of particular interest were studies that 

documented phosphate plant literature reviews, which provided links to additional sources of 

information. Scientific and epidemiological literature was culled from several sources: The Florida 

Institute of Phosphate Research (FIPR), the Health Physics Society (HPS), Federal agency technical 

information centers (which included national and international scientific committee documents),

NIOSH data capture activities, DOE archives, and the U.S. Environmental Protection Agency (EPA) 

Region 8 Technical Library.

In general, the search process found that older studies of phosphate facilities were not typically useful 

because (1) the working level (WL) concept had not yet been developed, (2) measurement techniques 

were not as sensitive, and (3) most of the documents lacked detailed data on the radiological 

characteristics of phosphate operations. Of the information repositories evaluated, Federal sources 

such as EPA, the Agency for Toxic Substances and Disease Registry (ATSDR), international and 

national scientific committee reports, and studies published by HPS and FIPR usually provided the 

most data.

3.1 FEDERAL SOURCES

Over the last 30 yr, the EPA Office of Radiation Programs has published a variety of reports on 

various aspects of the uranium and phosphate industry. Research and investigative studies have 

produced a compendium of data on the potential for exposure to TENORM, specifically on uranium, 

thorium, radium, radon, and radon progeny. Much of the EPA effort has focused on radon flux, indoor 

WL measurements, and risk assessment model development. In addition, the ATSDR maintains an 

on-line registry that details the hazards associated with radon exposure. Of particular interest to this 

study are those sources that (1) document radon flux measurements from phosphogypsum piles at 

Florida phosphate plants (EPA 1986), (2) define radon exhalation rates for phosphate and uranium 

source material (EPA 1979), and (3) provide radon emanation rates from phosphate mining (ATSDR

2005). 

According to Federal research, the concentrations of radium in gypsum piles and uranium mill tailings 

range from 12.8 to 42.8 pCi/g and 50 to 980 pCi/g, respectively (EPA 1979). Radon exhalation values 

can be as high as 8,070 pCi/(m2

-min) for gypsum and 72,000 pCi/(m2-min) for uranium mill tailings 

(EPA 1979). While there are a few physical differences between phosphogypsum and uranium mill 

tailings, the primary difference in exhalation rate is due to lower 226Ra concentrations in gypsum, a 

relationship directly related to the low abundance of uranium in phosphate ore (0.01% versus 0.1 to 

10% for uranium ores). Measured radon flux (also referred to as exhalation) at selected Florida 

phosphate plants has only ranged from 26.4 to 2,526 pCi/(m2

-min) depending on factors such as the 

thickness of the source matrix, moisture, and degree of disturbance of the source material (EPA

1986). 

3.2 FLORIDA INSTITUTE OF PHOSPHATE RESEARCH STUDY

The FIPR has evaluated data compiled over the past 20 yr and collected new information from 

phosphate mines, chemical plants, and outside contractors. The focus was on central Florida where 

concentrations of naturally occurring radioactive material (NORM) in the phosphate ore are higher. 

Personnel monitoring, exposure rates, area monitoring, environmental monitoring, and radon 

measurements were supplied by the phosphate and service industries. Samples were collected from 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 9 of 24

the mine area, rock-handling area, phosphoric acid production area, dry production area, shipping 

area, and service area. The following sections summarize the results of these studies from FIPR

(1998). 

3.2.1

The external dosimetry data from past studies as well as that from recent research (FIPR 1998) 

indicate that the annual radiation dose from phosphate production activities is less than 100 mrem. 

One phosphate company provided thermoluminescent dosimeter data for 1979 to 1996 for 

approximately 650 employees. The exchange frequencies were monthly as well as quarterly, which 

provided over 31,200 data entries. The mine area, rock area, and phosphoric acid areas provided 

personnel with the highest external doses, but “few employees exceeded the annual dose limit to 

members of the general public” (FIPR 1998) (the limit was 500 mrem per any 12-month period

b1992).

External Exposure

3.2.2

As a part of the FIPR (1998) study, air samples were collected at various locations throughout a 

phosphate facility’s various plants. The air sampling was performed in areas not only suspected to 

have elevated concentrations of 226Ra, but also in additional working areas without suspected 

elevated levels. Samples were collected during work activities that would elevate air concentrations. 

The air samples were analyzed both for gross alpha and beta as well as gamma spectroscopy 

analysis to determine the radionuclides present and their fractional contributions. The calculated air 

sample results were not corrected to subtract out any fraction of particulate that is non-respirable. 

Internal Exposure

The air sample results were coupled with inhalation Dose Conversion Factors (using ICRP Report No. 

68) and results from time motion studies to estimate inhalation of TENORM. The inhalation 

component of the total effective dose equivalent was calculated for the various work activities or areas 

at the plant: Rock area, phosphoric acid area, dry products area, shipping area, pan-chipping 

turnaround activity, and reactor-cleaning turnaround activity. A series of lognormal dose curves were 

presented, which indicated that the shipping area posed the greatest risk for internal exposure with a 

range from 0 to 350 mrem/yr (Figure 3-1). The area with the next greatest potential was the rock area 

(Figure 3-2). Intake amounts were not specified. 

Figure 3-1. Inhalation dose for the shipping area.
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 10 of 24

Figure 3-2. Inhalation dose for the rock area.

3.2.3

FIPR (1998) presents several sources of previously collected data as well as data from 

measurements collected by FIPR staff. The data from previous work is summarized as:

Radon Exposure

• A University of Florida study of radon WL exposures due to the process of wet rock loading

• Data sets of radon activity concentration measurements from 1989 to 1994, 1995 to 1996, and 

1993 to 1996 indicated as being collected at a phosphate facility’s chemical plant

• A data set from 1982 to 1996 indicating summary statistics of radon levels at a facility’s 

chemical plant as well as other locations such as rock tunnels and some mining related 

locations

• Data sets of radon activity concentration measurements from 1996 for a facility’s rock tunnels. 

Several of the above studies represent normal work locations or activities that were conducted apart 

from uranium extraction processes conducted under AWE contracts. Due to applicability of the 

Defense Authorization Act, only chemical plant data is considered as being representative of radon

levels that workers could have been exposed to during uranium extraction activities. 

3.3 SCIENTIFIC PUBLICATIONS

Publications from the scientific community were reviewed including Health Physics journal articles and 

reports from the National Council on Radiation Protection and Measurements (NCRP) and the United 

Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). 

The journal articles are highly mathematically oriented and offer insight to the physical and 

radiological characteristics of radon and its short-lived progeny that affect airborne concentrations and 

thus WLs. In addition to the magnitude of a radon source and natural radioactive decay, other factors 

affecting WLs are loss of radon and its progeny due to ventilation, the percentage of progeny that 

attach themselves to airborne particulate, surface plate-out of airborne particulate with attached 

progeny, and to some extent gravitational settling of the progeny. While the articles were beneficial in 

presenting some of the fundamental concepts of radon and progeny behavior, the mathematical 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 11 of 24

models found during literature review would require a series of assumptions for choosing parameter 

values such that use of any of the models becomes impracticable, especially when measured values 

are available. 

Because there may be some inconsistency in values in the individual journal articles, the reports 

prepared by NCRP and UNSCEAR are useful in that values are presented for equilibrium fraction F

as well as external gamma dose that are recognized by the scientific community. This analysis 

preferred the use of a nationally or internationally recognized value (if present) over that of any value 

from a single study presented in a journal article. 

3.4 OTHER REVIEWS

Detailed characterization of radon and radon progeny WLs for each AWE facility requires site-specific 

data on the radiological conditions during wet chemical phosphoric acid uranium recovery operations. 

The NIOSH Project archives contain site source documents linked to a master summary spreadsheet. 

Source documentation contains information on personnel monitoring, cohort exposure data, area and 

environmental monitoring, and general site statistics. 

Attachment A provides a summary of the review of the records collected for the NIOSH Project. The 

record survey yielded very little information of practical use for estimating site-specific occupational 

radon exposures. As a consequence, data and technical approaches from other existing literature 

were adapted to generate claimant-favorable values for occupational exposure based on conditions 

for workers involved with uranium extraction at a phosphate plant. 

4.0 OCCUPATIONAL EXPOSURE CHARACTERIZATION

Technological enhancement of uranium during wet chemical phosphoric acid processing, as well as 

the subsequent radioactive decay, presents discrete radiological health concerns to phosphate plant 

personnel. Occupational external exposure to radium and the potential internal dose from radon and 

its progeny as well as respirable particulate matter containing long-lived radionuclides are of particular 

interest. While the most technically satisfying approach would be to address exposure concerns for 

each AWE facility during its specific period of uranium recovery operations, the literature review

process has demonstrated that the available documentation does not provide enough detail to 

complete such a task in a reasonable and time-efficient approach. Therefore, this document 

describes the development of a single approach that covers all listed AWE phosphate facilities. The 

results are radon and radon progeny levels in units of WL-months (WLM). 

4.1 INTERNAL AND EXTERNAL EXPOSURE CONSIDERATIONS

For the purpose of this analysis, the evaluation of occupational exposure was limited to the naturally 

occurring radioactive material that was technologically enhanced during the processing of phosphate 

ores. Analysis of additional internal and/or external exposure from uranium extract (yellow cake) has 

been left to the appropriate site-specific technical basis document.

During normal plant operations, activities with the potential for occupational exposure were mining 

and beneficiation, ore drying and grinding, the wet acid process, maintenance, work in vicinity of 

phosphogypsum stacks, and product packaging and handling. For the purposes of reconstructing 

exposures due to work under AWE contract, only the work locations and activities related to extraction 

of uranium from phosphate ores should be considered. As a result, mining and beneficiation, ore 

drying and grinding, and nonuranium product packaging and handling were not considered. The 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 12 of 24

chemical plants that performed the uranium extraction using the wet acid process and the resultant 

waste streams in the form of the phosphogypsum stacks were considered. 

4.1.1

The primary constituent for external exposure is 226Ra because of its beta-gamma emission relative to 

the alpha-emitting constituents of the 238U decay series. Due to chemical separation in the wet acid

process, radium scale builds up at several locations in the processing equipment. The radiation levels 

peak in the acid-wash section, with dose rates as high as 10 mrem/hr (Lardinoye and Weterings 

1982). With consideration of the nature of their duties, duration of work activities, and frequency of 

such work; a maximally exposed worker (operator or maintenance) could receive up to 220 mrem/yr

(Lardinoye and Weterings 1982). NCRP (1993) reports exposures for a 2,000 hr/yr occupancy at 

phosphogypsum stacks as 70 mrem; Laiche and Scott (1991) estimated a range for that occupancy of 

48 to 68 mrem. For the purposes of dose reconstruction, the above data may be represented with a 

lognormal distribution having a geometric mean of 70 mrem/y, a 95th percentile value of 220 mrem/y, 

and a geometric standard deviation of 2.00. Table 4-1 summarizes these values.

External Exposure

Table 4-1. Annual external exposure.

Exposure 

(mrem/yr) Comments

Dose 

distribution

Photon energy 

distribution (keV)

220 Upper bound for exposures to plant workers with 

high occupancy in and around process equipment

Constant 50% 30–250

50% >250

70 Exposure from work located at gypsum stacks Lognormal, 

GSD=2.00

50% 30–250

50% >250

a. GSD = geometric standard deviation.

4.1.2

Botezatu and Iacob (2004) conducted characterization studies in a phosphate plant for occupational 

exposure due to NORM. Particulate concentrations generated during operations were given as a 

range from 0.01 to 0.1 g/m3

. Radioactivity concentrations were given as 0.087 to 23.75 Bq/g for 238U 

and 0.17 to 18.6 Bq/g for 226Ra. The particle size measurements resulted in a percentage of 

respirable particles of 81% 4 μ or less. 

Internal Exposure

While Botezatu and Iacob (2004) did not reveal the location of the phosphate plant, the upper range of 

the activity concentrations are much higher than typical ores processed in U.S. facilities. American 

phosphate ores contain an average of about 0.01% uranium (Roessler et al. 1979). Table 4-2 lists the 

activity concentrations from the Roessler et al. analysis of central Florida phosphate materials:

Table 4-2. Phosphate 238U activity 

concentrations.

Physical form

U-238 concentration 

(pCi/g)

Average Range

Matrix 38.5 20.2–83.4

Pebble 45.8 36.0–68.1

Rock concentrate 31.9 20.1–49.8

Clays 27.1 16.0–49.2

Tailings 4.7 1.5–10.4

5% phosphoric acid 6.3 --

10% phosphoric acid 17.1 --
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 13 of 24

30% phosphoric acid 30.0 --

Gypsum <0.5 <0.4–<0.7

Because the average value of 45.8 pCi/g for phosphate pebble is the maximum average from Table 4-

2, for conservatism, this value is used in calculating internal deposition rates. The range of 36.0-68.1 

pCi/g may be approximated with a lognormal distribution with a geometric mean equal to 45.8 pCi/g, a 

95th percentile value of 68.1 pCi/g, and a geometric standard deviation of 1.27.

In similar work for EPA, Guimond, Mills, and Windham (1977), found 232Th activity concentrations as 

being 0.44 pCi/g in marketable rock (rock concentrate). According to Table 4-2 above, 238U is present 

in 44% greater abundance in pebble product than rock concentrate. Therefore, it is reasonable to 

assume that 232Th also exists in similar relative abundance, and an activity of 0.63 pCi/g would be 

expected for 232Th in pebble form. Given that no range of measurement values are given for 232Th, it 

is assumed that the abundance of thorium is also distributed lognormally with a geometric mean of 

0.63 pCi/g and a geometric standard deviation of 1.27. The resulting 95th percentile value would then 

be 0.933 pCi/g.

Table 4-3 lists the intakes calculated using the value of 0.1 g/m3 for dust loading, and a breathing rate 

of 1.2 m3

/hr. For maximizing conditions, the 95th percentile values of 68.1 pCi/g and 0.933 pCi/g are 

used for 238U and 232Th respectively. Best estimate conditions utilize the geometric mean values of 

45.8 pCi/g and 0.63 pCi/g for 238U and 232Th respectively.

Table 4-3. Internal deposition.

Dose reconstruction approach Distribution Intake amount 

(pCi/hr) Radionuclide

Maximizing Constant 8.17 U-238 in equilibrium with its daughters

1.12E-01 Th-232 in equilibrium with its daughters

Best Estimate Lognormal

GSD=1.27

5.5 U-238 in equilibrium with its daughters

7.56E-02 Th-232 in equilibrium with its daughters

4.2 RADON EXPOSURE

Because of release of radon gas during phosphate plant operations, radon poses a high potential for 

occupational exposure. The literature review produced very little data about radon or WL at 

phosphate facilities during AWE operations. As indicated in Attachment A, Virginia-Carolina had an 

average daytime radon concentration between 0.6 and 0.9 pCi/L with progeny concentration 

measurements indicating a WL of less than 0.01. However, the measurements occurred before 

remediation and after the uranium extraction facility had ceased operation and been torn down. Only 

a concrete pad remained at the time of monitoring. 

Due to the lack of data from AWE sites, this analysis used the data in FIPR (1998) to determine radon 

concentrations and WLs. This was possible because the factors that affect radon concentrations 

have changed very little over time. No significant changes in the construction of wet process acid 

plants had occurred since the time of AWE operations (Birky 2005b). While environmental regulations 

led to decreased overall emissions, the controls had little or no effect on occupational radon levels. In 

addition, the rate of ore processing has increased over time (Birky 2005b). 

Attachment B lists the data from FIPR (1998). The data sets indicated as “Chemical Plant” refer to 

the building or structure that processed rock concentrate using a chemical or wet acid process (Birky 

2005c). As mentioned in Section 4.1, this analysis limited consideration of occupational exposures to 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 14 of 24

activities relevant to uranium extraction. Therefore, radon measurements related to rock tunnels, wet 

rock loading, and mining operations were not considered. Measurements from those locations have 

been highlighted in gray and were not included in analysis of occupational radon exposure. The data 

sets that gave summary radon concentrations for a span of years were given equal weight with those 

that gave concentrations over shorter periods. The combined measurements formed a set of

130 data points that have a geometric mean of 0.751 pCi/L and a geometric standard deviation (GSD) 

of 1.989. The 95th-percentile value is 2.33 pCi/L.

Table 4-4 lists WLs calculated using an equilibrium factor F of 0.4 (ICRP 1981; UNSCEAR 1993).

Table 4-4. Phosphate plant worker radon WL values.

DR approach

Radon concentration 

(pCi/L) F WL WLM/yr Distribution

Best estimate 0.751 0.4 0.003 0.036 Lognormal, GSD=1.989

Maximizing 2.33 0.4 0.0093 0.112 Constant

5.0 INDIVIDUAL PROGENY EQUILIBRIUM FRACTIONS AND UNATTACHED FRACTIONS

Radon daughter products primarily get trapped in the lungs; therefore the primary concern of radon 

daughters is lung exposure. For the purpose of the EEOICPA, radon exposures for lung cancers are 

expressed in units of Working Level Months. In most instances, radon exposure to organs other than 

the lung are negligible (> 1 mrem/year); however, there may be a small number of cases that warrant 

evaluation of exposure to other organs. Since the exposure unit of WLM is applicable only for lung 

cancer dose reconstructions, individual organ dose in rem would need to be calculated for non-lung 

dose reconstructions.

Inhalation rates for radon daughters would be necessary in order to determine internal doses. The 

equilibrium factors for each of the short-lived radon progeny and the fractions that are not attached to 

airborne particulate must be known for calculation of inhalation rates. Domanski (1979) calculated 

values for the individual equilibrium factors. To correspond with an overall equilibrium factor F of 0.4, 

the individual factors are 0.656, 0.446, and 0.259 for RaA, RaB, and RaC, respectively. 

The unattached fraction is an inverse function of particle concentration with secondary dependence 

on particle size (NCRP 1984). As a result, unattached fractions tend to be higher for typical indoor 

atmospheres [8% according to Nikezic, Hack, and Yu (2002)], than in dusty conditions such as mining 

atmospheres where the unattached fraction is only about 1% (Birchall and James 1994). 

NCRP (1984) lists the unattached fractions fa, fb, and fc for RaA, RaB, and RaC, respectively, as a 

function of particle concentration. For a particle concentration of 1 × 104 particles/cm3

, which best 

represents the likely atmosphere in a phosphate facility, the resultant unattached fractions are 

fa = 0.18, fb = 0.021, and fc = 0.0007.

The lung absorption half-life of Pb-214 and Bi-214 have been measured to be 10 hour and 13 hours

respectively (Marsh and Birchall). Using the parameters described here and the assumed absorption 

half-life for Po-218 of 10 hours, the dose to various organs from radon progeny can be calculated. 

The dose per 2000 hour work year from the progeny associated with a 0.751 pCi/L radon gas 

concentration is less than 1 mrem/yr for all organs outside the respiratory tract. 

The dose from the radon gas itself dissolved in the body tissues can be estimated using ICRP 32. 

This publication gives an equilibrium conversion factor of 3.33E-7 rem/hr per pCi/L. This conversion 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 15 of 24

factor produces an annual dose to organs other than the respiratory tract of approximately 1.55 mrem 

per 2000 hour year for a continuous exposure to 2.33 pCi/L. 

The dose to the kidney (highest exposed organ other than the respiratory tract) from radon associated 

with this Technical Information Bulletin is approximately 2 mrem per year. Therefore, all organs not 

associated with the respiratory tract will be assigned an annual radiation dose of 2 mrem to account 

for exposure to radon and its progeny. 
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 16 of 24

REFERENCES

ATSDR (Agency for Toxic Substance and Disease Registry), 2005, Toxicological Profile for Radon, 

Section 5.5, U.S. Department of Health and Human Services, Centers for Disease Control and 

Prevention, on-line database.

Birchall, A., and James, A. C., 1994, “Uncertainty Analysis of the Effective Dose per Unit Exposure 

from Radon Progeny and Implications for ICRP Risk-Weighting Factors,” Radiation Protection 

Dosimetry, volume 53, Nos. 1–4, pp. 133–140.

Birky, B., 2005a, “Occupational, Radiological Exposures in the Phosphate Industry,” electronic mail to 

J. Guido (Oak Ridge Associated Universities Team), July 13, Florida Institute of Phosphate 

Research, Bartow, Florida.

Birky, B., 2005b, “Phosphate Plant Radon Levels,” electronic mail to R. Gard (Oak Ridge Associated 

Universities Team), September 1, Florida Institute of Phosphate Research, Bartow, Florida.

Birky, B., 2005c, “Re: Phosphate Plant Radon Levels,” electronic mail to R. Gard (Oak Ridge 

Associated Universities Team), September 2, Florida Institute of Phosphate Research, Bartow, 

Florida.

Botezatu, E., and O. Iacob, 2004, “Radiation Hazard for Workers Related to NORM in Phosphate 

Fertilizers and Energy Production,” 11th Congress of the International Radiation Protection 

Association, May.

Domanski, T., 1979, “Correlation between the equilibrium factor F and the relative concentration of 

radon daughters in mine air”, Health Physics, Vol. 137, 177.

Egidi, P., 1997, “Introduction to Naturally Occurring Radioactive Material,” 42nd Annual Meeting of the 

Health Physics Society, July.

EPA (U.S. Environmental Protection Agency), 1979, A Preliminary Radiological Assessment of 

Radon Exhalation from Phosphate Gypsum Piles and Inactive Uranium Mill Tailings Piles, 

EPA 520/5-79-004, Office of Radiation Programs, Washington, D.C.

EPA (U.S. Environmental Protection Agency), 1986, Radon Flux Measurements on Gardinier and 

Royster Phosphogypsum Piles Near Tampa and Mulberry, Florida, EPA 520/5-85-029, Office 

of Radiation Programs, Washington, D.C.

FIPR (Florida Institute of Phosphate Research), 1998, Evaluation of Exposure to Technologically 

Enhanced Naturally Occurring Radioactive Materials (TENORM) in the Phosphate Industry, 

Publication 05-046-155, Bartow, Florida.

Guimond, R. J., Mills, W. A., and Windham, S. T., 1977, “Radiation Exposures in the Florida 

Phosphate Industry,” International Radiation Protection Association Meeting #4, Paris, France, 

volume 3, pp. 1049–1052.

ICRP (International Commission on Radiological Protection), 1981, Limits for Inhalation of Radon 

Daughters by Workers, Publication 32, Pergamon Press, Oxford, England.
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 17 of 24

J. W. Marsh and A. Birchall, Determination of Lung-to-Blood Absorption Rates for Lead and Bismuth 

which are appropriate for Radon Progeny, Radiation Protection Dosimetry, Vol. 83, No 4, pp 331-337 

(1999)

Laiche, T. P., and Scott, L. M., 1991, “A Radiological Evaluation of Phosphogypsum,” Health Physics, 

volume 60, number 5, pp. 691–693.

Lardinoye, M. H., and K. Weterings, 1982, “Unexpected 226Ra Build-up in Wet Process PhosphoricAcid Plants,” Health Physics, volume 42, number 4, pp. 503–514.

NCRP (National Council on Radiation Protection and Measurements) Report No. 78, 1984, 

Recommendations of the National Council on Radiation Protection and Measurements, 

Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters in 

the United States, Bethesda, Maryland, May.

NCRP (National Council on Radiation Protection and Measurements) Report No. 118, 1993,

Recommendations of the National Council on Radiation Protection and Measurements, 

Radiation Protection in the Mineral Extraction Industry, Bethesda, Maryland, November.

Nikezic, D., Haque, A. K. M. M., and Yu, K. N., 2002, “Effects of different deposition models on the 

calculated dose conversion factors from Rn-222 progeny.” Journal of Environmental 

Radioactivity, volume 61, number 3, pp. 305–318.

Roessler, C. E., Z. A. Smith, W. E. Bolch, and R. J. Prince, 1979, “Uranium and Radium-226 in 

Florida Phosphate Materials,” Health Physics, volume 37, September, pp. 269–277.

UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation), 1993, Sources 

and Effects of Ionizing Radiation, United Nations, New York, New York..

Wilkinson, G. E., 1976, Uranium Recovery from Wet Process Phosphoric Acid, Gardinier, Inc., 

Tampa, Florida.
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/0

6/200

6 Page 18 of 24

ATTACHMENT A

Synopsis of Phosphate Plant Data in the NIOSH Site Research Database

Page 1 of 1

Table A-1. Synopsis of phosphate plant data in the NIOSH Site Research Database

AWE sites

Armour DOW IMAC Gardinier Texas City Virginia-Carolina

Years of operation 1/1/51–12/31/55 1/1/47–12/31/57 1/1/51–12/31/61 1/1/52–12/31/58 1/1/52–12/31/56 1/1/52–12/31/57

Total documentsa 2 11b 4 3 3 3

Contract/agreement X X X

General process & history X X X X X

Production amount 100 tons total with a peak 

production of 2 to 3 

tons/month; 24 tons of 

U3O8 per yearc

60 tons of uranium 

concentrate per 

year

12 tons of U3O8 per 

year

12 tons of U3O8 per year 

Facility dimensions 175 × 90 m (estimate) 90 × 250 ft – concrete pad 19 × 36 yd. concrete 

pad

10 × 10 m (concrete pad); 10 x 

17 m (building)e

Survey report: X Xf X X (pages 5–109 

missing)

X

γ exposure rate (μR/hr) 7 inside bldg, 30 

outside @ 1 m

3–7 floor surface; 

1–4 overhead beam 

surfaces

Max. 30 @ 1 m @ pad and 

100 @ 1 m adjacent to pad

120 @ 1 md 22–58 @ 1 m @ pad

8–20 @ 1 m @ building

20–100 outside 

β/γ dose rate (mrad/hr) 0.02 <0.01–0.06 @ overhead 

beams

0.1 and 0.2 0.25 0.05–0.26 @ pad

0.04–.07 @ 1 cm @ building 

Samples (pCi/g)

0.22–1.3 (beam dust)

Ra-226

0.17–0.54 (debris)

3.7–310 (beam dust)

U-238

0.95–1.2 (debris)

1,000 Ra-226 

(floor shavings) 

15–56 U-238 (residue from pad)

Soil sample results 28.3 pCi/L Ra-226 4.5-170 pCi/L Ra226; see page 78 for 

location and U 

results

14–1900 Ra-226; 

Surface (pCi/g)

6–54 U-238

5–360 Ra-226

Subsurface

2–46 U-238

Radon and radon daughter 

concentrations in air (pCi/L)

0.4–1.0 lunchroom

0.2–1.9 maintenance area

0.6–0.9 avg. daytime conc.

Rn daughters <0.01 WL

Water sample results (pCi/L) < guidelines Max. 110 U-238

Background measurements:

γ exposure rate (μR/hr) 7–11 @ 1 m 5 @ 1 m

Soil Ra-226 concentrations (pCi/g) 0.88–0.93 0.3–2.3 

Soil U-238 concentrations (pCi/g) 1.0–1.1 0.1–1.1 

β/γ dose rates (mrad/hr) 0.01–0.05 

FUSRAP elimination report X X X X

Total number of documents reviewed in the Site Research Database and Task 2’s Data Entry Source Document Review. NOTE: Duplication of documents exists among both resource databases.

a. Includes both site locations – Walnut Creek California and Madison, Illinois

b. Information in Texas City Chemical document 

c. States typical value for similar production plants in other parts of the country

d. The pilot plant at this site was disassembled in about 1960; all that remains is a concrete pad. Sometime later, a maintenance building was constructed adjacent to the pad and contains a maintenance 

room, tool cage, lunchroom and a small office. At the time of the survey in 1977, this building was occupied by personnel. 

Survey results are for the site located in Madison, Illinois. Survey for the Walnut Creek, California location states no levels above background were detected except an inaccessible area on a fume hood.
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 19 of 24

ATTACHMENT B

Data from FIPR (1998)

Page 1 of 6

Table B-1. Phosphate facility radon measurements.

Location Start date End date Result pCi/L Comments

D Granular 2nd floor stairs 12/3/1997 12/9/1997 1.1

D Reclaimer - DAP Shipping 12/2/1997 12/5/1997 1

D DAP #4 Granulator 12/8/1997 12/12/1997 0.5

D XYZ; 3rd floor workbench 12/1/1997 12/5/1997 < 0.5

H B Ship.; Platform over conv. 12/1/1997 12/5/1997 0.7

M Float Plant 12/15/1997 12/19/1997 1.6 Duplicate

M Float Plant (Retest) 1/9/1998 1/13/1998 1.5 Duplicate

M Rail Car Load-Out 12/4/1997 12/9/1997 1.4

M Pit Car #14 12/15/1997 12/19/1997 1.1 Duplicate

M Float Plant 12/15/1997 12/19/1997 0.8

M Pit-Car 12/4/1997 12/19/1997 0.7

M Pit Car #12 12/15/1997 12/19/1997 0.7

M Float Plant Lab 12/4/1997 12/9/1997 < 0.5

M Pit-Car 12/4/1997 12/9/1997 < 0.5

P Phos Acid E-Train filter p. area 12/2/1997 12/5/1997 1.7 E-Perm wet

P Phos Acid Control Room 12/3/1997 12/9/1997 1.4 Dup. with bag

P Phos Acid Control Room 12/8/1997 12/12/1997 1.4 Dup. with bag

P Phos Acid B filter pan area 12/3/1997 12/9/1997 0.9

P Phos Acid Control Room 12/9/1997 12/12/1997 < 0.5 Dup. with bag

P Phos Acid Control Room 12/2/1997 12/5/1997 < 0.5 Dup. with bag

P Phos Acid Control Room 12/1/1997 12/5/1997 < 0.5 Dup. with bag

R Rock Tunnel 12/4/1997 12/9/1997 21.5

R Rock Tunnel 12/4/1997 12/9/1997 1.4 Duplicate

R Rock Tunnel 12/8/1997 12/12/1997 40

R Rock Tunnel 12/2/1997 12/5/1997 28.8

R Rock Tunnel 12/9/1997 12/12/1997 15.8

R Rock Tunnel 12/19/1997 12/23/1997 5.8

R Wet rock unload; QC/Breakr. 12/2/1997 12/5/1997 2.4
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 20 of 24

ATTACHMENT B

Data from FIPR (1998) (Continued)

Page 2 of 6

Table B-2. Annual exposure to radon progeny in wet rock 

loading.

Company No.

Mean 

(WLM/yr)

Upper limit 

(WLM/yr)

Lower limit 

(WLM/yr)

R 2 0.0046 0.0054 0.0037

L-2 6 0.84 1.5 0.003

L-1 6 0.074 0.25 0.0017

M-N 5 0.022 0.09 0.00041

M-O 5 0.009 0.023 0.0035

K-1 2 0.14 0.2 0.082

K-2E 5 0.044 0.21 0.0024

K-2W 6 0.037 0.2 0.0017

Q 1 0.0007 0.0007 0.0007

G 12 0.059 0.35 0.0064

H 8 0.0028 0.0064 0.00052

D-2 3 0.0041 0.012 0.00018

D-1 3 0.007 0.018 0.00015

E-B 9 0.062 0.34 0.00014

E-A 5 0.017 0.036 0.004

Table B-3. Chemical plant radon readings, summary statistics 1989 to 1994.

NE gypsum 

stack well

Auto shop 

SE fence

SW of 

plant

Burn 

area 

fence

Liming 

station 

ladder

Environmental 

monitoring 

well

Gypsum 

stack flux 

test

Cooling 

pond 

hand rail

Mean 2.43 2.89 0.35 1.89 1.9 2.6 6.52 2.08

Standard error 0.45 0.65 0.08 0.48 0.49 0.74 1.01 0.63

Median 0.75 2.12 0.18 0.4 0.54 0.75 4.41 0.91

Mode 0 0 0 0 0 0 0 0

Standard deviation 4.3 4.87 0.47 5.23 5.04 7.43 4.95 5.18

Sample variance 18.45 23.73 0.22 27.39 25.36 55.26 24.52 26.85

Kurtosis 9.1 20.14 12.03 29.97 40.15 32.12 0.68 19.41

Skewness 2.94 4.16 3.1 5.04 6.05 5.35 1.36 4.48

Range 21.74 30.6 2.38 40.87 40.84 56.76 15.82 27.61

Minimum 0 0 0 0 0 0 2.07 0

Maximum 21.74 30.6 2.38 40.87 40.84 56.76 17.89 27.61

Count 90 56 31 118 105 101 24 68

CL 95% 0.89 1.28 0.16 0.94 0.96 1.45 1.98 1.23

Table B-4. Radon measurements summary,

1995 to 1996.

Area Mean (pCi/L)

NE gypsum stack monitoring well 9.51

Auto shop 2.99

Environmental monitoring well 5.11

Cooling pond hand rail 3.02

Burn area fence 1.66
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 21 of 24

ATTACHMENT B

Data from FIPR (1998) (Continued)

Page 3 of 6

Table B-5. Radon readings in rock tunnels, 1996.

Start End μR/hr pCi/L Area Location

1/5/1996 2/6/1996 6 8.6 Tunnel Middle

1/5/1996 2/6/1996 6 7.284 Tunnel North

1/5/1996 2/6/1996 6 6.938 Tunnel South lower

1/5/1996 2/6/1996 6 10.121 Tunnel South upper

2/6/1996 3/13/1996 10 7.094 Tunnel Middle

2/6/1996 3/13/1996 7 8.669 Tunnel North

2/6/1996 3/13/1996 10 4.819 Tunnel South lower

2/6/1996 3/13/1996 7 10.479 Tunnel South upper

3/13/1996 4/19/1996 10 5.295 Tunnel Middle

3/13/1996 4/19/1996 7 28.137 Tunnel North

3/13/1996 4/19/1996 10 4.228 Tunnel South lower

3/13/1996 4/19/1996 7 5.157 Tunnel South upper

4/19/1996 5/14/1996 16 6.272 Tunnel Middle

4/19/1996 5/14/1996 9 16.626 Tunnel North

4/19/1996 5/14/1996 14 3.441 Tunnel South lower

4/19/1996 5/14/1996 10 4.621 Tunnel South upper

5/14/1996 6/18/1996 16 3.349 Tunnel Middle

5/14/1996 6/18/1996 9 5.574 Tunnel North

5/14/1996 6/18/1996 14 1.38 Tunnel South lower

5/14/1996 6/18/1996 10 2.135 Tunnel South upper

6/18/1996 7/17/1996 16 9.144 Tunnel Middle

6/18/1996 7/17/1996 9 7.572 Tunnel North

6/18/1996 7/17/1996 14 0.785 Tunnel South lower

6/18/1996 7/17/1996 10 1.563 Tunnel South upper

7/17/1996 8/8/1996 16 3.295 Tunnel Middle

7/17/1996 8/8/1996 9 7.031 Tunnel North

7/17/1996 8/8/1996 14 0.985 Tunnel South lower

7/17/1996 8/8/1996 10 2.562 Tunnel South upper

8/8/1996 9/23/1996 10 3.399 Tunnel Middle

8/8/1996 9/23/1996 5 59.599 Tunnel North

8/8/1996 9/23/1996 10 1.63 Tunnel South lower

8/8/1996 9/23/1996 10 2.007 Tunnel South upper

9/23/1996 10/15/1996 8 61.33 Tunnel South upper

9/23/1996 10/15/1996 10 4.355 Tunnel South upper

9/23/1996 10/15/1996 12 0.964 Tunnel South upper

9/23/1996 10/15/1996 10 1.937 Tunnel South upper
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 22 of 24

ATTACHMENT B

Data from FIPR (1998) (Continued)

Page 4 of 6

Table B-6. Radon readings in rock tunnels using e-perms, 

1996.

Start End μR/hr pCi/L Chute #

1/10/1996 2/20/1996 50 9.621 1

1/10/1996 2/20/1996 50 8.723 1

1/10/1996 2/20/1996 50 11.229 10

1/10/1996 2/20/1996 50 16.025 10

1/10/1996 2/20/1996 50 4.535 20

1/10/1996 2/20/1996 50 6.54 20

2/20/1996 3/8/1996 30 11.41 1

2/20/1996 3/8/1996 30 8.496 1

2/20/1996 3/8/1996 40 10.633 10

2/20/1996 3/8/1996 40 10.908 10

2/20/1996 3/8/1996 50 4.174 20

2/20/1996 3/8/1996 50 5.584 20

3/8/1996 4/3/1996 40 9.701 1

3/8/1996 4/3/1996 40 7.056 1

3/8/1996 4/3/1996 35 15.259 10

3/8/1996 4/3/1996 35 24.598 10

3/8/1996 4/3/1996 50 9.287 20

3/8/1996 4/3/1996 50 11.199 20

4/3/1996 5/6/1996 35 9.227 1

4/3/1996 5/6/1996 35 5.051 1

4/3/1996 5/6/1996 35 14.144 10

4/3/1996 5/6/1996 35 17.244 10

4/3/1996 5/6/1996 40 9.999 20

4/3/1996 5/6/1996 40 18.015 20

5/6/1996 6/17/1996 35 14.591 1

5/6/1996 6/17/1996 35 5.458 1

5/6/1996 6/17/1996 35 21.567 10

5/6/1996 6/17/1996 35 30.285 10

5/6/1996 6/17/1996 40 5.083 20

5/6/1996 6/17/1996 40 16.273 20

6/17/1996 7/31/1996 40 28.164 1

6/17/1996 7/31/1996 40 8.853 1

6/17/1996 7/31/1996 40 20.975 10

6/17/1996 7/31/1996 40 63.616 10

6/17/1996 7/31/1996 40 8.59 20

6/17/1996 7/31/1996 40 9.434 20

7/31/1996 8/27/1996 35 15.978 1

7/31/1996 8/27/1996 35 8.39 1

7/31/1996 8/27/1996 35 29.499 10

7/31/1996 8/27/1996 35 22.962 10

7/31/1996 8/27/1996 40 6.741 20

7/31/1996 8/27/1996 40 6.983 20

8/27/1996 9/13/1996 35 14.949 1

8/27/1996 9/13/1996 35 14.686 1

8/27/1996 9/13/1996 35 17.147 10

8/27/1996 9/13/1996 35 33.107 10

8/27/1996 9/13/1996 40 8.839 20

8/27/1996 9/13/1996 40 31.428 20

9/13/1996 10/8/1996 35 20.242 1

9/13/1996 10/8/1996 35 10.033 1

9/13/1996 10/8/1996 35 42.713 10

9/13/1996 10/8/1996 35 74.706 10

9/13/1996 10/8/1996 40 71.348 20

9/13/1996 10/8/1996 40 79.54 20
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 23 of 24

ATTACHMENT B

Data from FIPR (1998) (Continued)

Page 5 of 6

Table B-7. Terradex radon measurements, summary statistics 1982 to 1996 .

Area Mean (pCi/L)

DAP#1 Control Room 0.2

MAP-DAP E. Wall Control Room 0.23

Area-40 5th Floor 0.27

Auto Shop 0.27

DAP#1 Storage 0.27

Area-50 Lunch Room 0.28

Area-40 Storage 0.3

DAP#1 Shipping Control Room 0.3

Met Tower Upper Level (30 ft) 0.3

MAP-DAP Shipping Office 0.34

Pilot Plant 0.4

H.P. Lab 0.43

Area-10 Control Rooms S.C.B.A. 0.52

DAP Storage W. of Conveyor 0.52

Hall 0.53

Main Office 0.58

Safety Receptionist Window 0.59

Area-20 0.61

Ball Mill Electric Room 0.61

GSTP 0.61

Phos-Acid 0.64

MAP-DAP Control Room E. Wall 0.67

MAP Storage N.E. Corner 0.71

Met Tower Lower Level (3 ft) 0.71

Area-40 Control Room 0.72

Ball Mill Cont. Room S. Wall 0.78

Dragline Inside Cab 0.86

Dozer Inside Cab 1.2

Environmental Lab 1.4

Background 1.88

Phosphate Council 3.2

Wet Rock Lower Level 6.62

Wet Rock Lower Level 8.6

Wet Rock S. Entrance 0.98

Wet Rock Behind Refrigerator 1.1

West Rock Tunnel Chute 30 5.76

West Rock Tunnel Chute 25 8.95

West Rock Tunnel Chute 20 10.24

East Rock Tunnel Chute 25 10.94

East Rock Tunnel Chute 30 11.11

West Rock Tunnel Chute 15 11.89

West Rock Tunnel Chute 1 12.51

West Rock Tunnel Chute 5 13.07

West Rock Tunnel Chute 10 14.87

East Rock Tunnel Chute 20 18.24

East Rock Tunnel Chute 10 19.56

West Rock Tunnel Chute 33 19.96

East Rock Tunnel Chute 1 23.8

Area Mean (pCi/L)

East Rock Tunnel Chute 15 25.97

East Rock Tunnel Chute 5 26.07

West Rock Tunnel Chute 27 32.91

West Rock Tunnel Chute 16 40.23

West Rock Tunnel Chute 21 43.75

West Rock Tunnel Chute 8 47.56
Document No. ORAUT-OTIB-0043 Revision No. 00 Effective Date: 01/06/2006 Page 24 of 24

ATTACHMENT B

Data from FIPR (1998) (Continued)

Page 6 of 6

Table B-8. Chemical plant track-etch radon results, 1993 to 1996. Start End Area pCi/L

01/22/93 07/22/93 Administrative Assistant Trailer 1

Electric Shop 0.7

Environmental Tech Office 1

Filter Pan Level Offices 0.6

Main Office Bldg 0.2

Office 0.3

Office 0.6

Office 0.3

Phos-acid Control Room 0.9

07/22/93 01/24/93 Administrative Assistant Trailer 1.5

Electric Shop 0.8

Employee's Residence 1.2

Environmental Tech Office 1.8

Filter Pan Level Offices 0.7

Main Office Bldg 1

Office 0.4

Office 0.8

Phos-acid Control Room 0.7

01/24/94 07/21/94 Administrative Assistant Trailer 0.9

Electric Shop 0.5

Environmental Tech Office 1.2

Filter Pan Level Offices 0.6

Lab Bldg (main Office Bldg) 0.8

Phos-acid Control Room 0.6

Residence 0.5

Trailer 0.5

Trailer 0.7

07/21/94 01/31/94 Electric Shop 0.3

Environmental Tech Office 1.2

Filter Pan Level Offices 0.3

Instrument Shop 0.8

Lab Bldg (main Office Bldg) 1.1

Phos-acid Control Room 0.6

Safety Office 0.7

Start End Area pCi/L

01/31/95 07/21/95 Ball Mill Control Room 0.3

DAP Maintenance Lunchroom 0.3

Electric Shop 0.5

Employee's Residence 2.1

Filter Pan Level Offices 0.4

Instrument Shop 0.6

Lab Bldg (main Office Bldg) 1

Phos-acid Control Room 0.9

Rock Tunnel 5.8

Safety Office 0.6

Services 0.6

Sulfuric Control Room 0.7

Sulfuric Maintenance Office 1.2

07/21/95 01/22/95 Ball Mill Control Room 0.4

DAP Maintenance Lunchroom 0.3

Electric Shop 0.5

Filter Pan Level Offices 0.5

Instrument Shop 0.6

Lab Bldg (main Office Bldg) 0.9

Phos-acid Control Room 0.6

Rock Tunnel 5.2

Safety Office 0.5

Services 0.5

Sulfuric Control Room 0.6

Sulfuric Maintenance Office 2.9

01/17/96 07/17/96 Ball Mill Control Room 1

DAP Maintenance Lunchroom 0.4

Electric Shop 0.6

Filter Pan Level Offices 0.7

Instrument Shop 0.8

Main Office 1.4

Phos-acid Control Room 1

Safety Office 0.7

Services 0.8

Sulfuric Control Room 0.7

Sulfuric Maintenance Office 1.4