Draft 

ADVISORY BOARD ON 

RADIATION AND WORKER HEALTH

National Institute for Occupational Safety and Health

EVALUATION OF TECHNICAL BASIS DOCUMENT FOR 

TEXAS CITY CHEMICALS, INC., TEXAS CITY, TEXAS

Contract No. 211-2014-58081 

Document No. SCA-TR-2018-SP004, Revision 0 

Prepared by 

Ron Buchanan, PhD, CHP 

Rose Gogliotti 

SC&A, Inc.

2200 Wilson Boulevard, Suite 300 

Arlington, VA 22201-3324 

Saliant, Inc.

5579 Catholic Church Road 

Jefferson, Maryland 21755 

May 2018 

DISCLAIMER 

This is a working document provided by the Centers for Disease Control and Prevention (CDC) technical 

support contractor, SC&A for use in discussions with the National Institute for Occupational Safety and 

Health (NIOSH) and the Advisory Board on Radiation and Worker Health (ABRWH), including its 

Working Groups or Subcommittees. Documents produced by SC&A, such as memorandum, white paper, 

draft or working documents are not final NIOSH or ABRWH products or positions, unless specifically 

marked as such. This document prepared by SC&A represents its preliminary evaluation on technical 

issues.

NOTICE: This document has been reviewed to identify and redact any information that is protected by 

the Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 
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SC&A, INC.: Technical Support for the Advisory Board on Radiation and 

Worker Health Review of NIOSH Dose Reconstruction Program 

DOCUMENT TITLE: Evaluation of Technical Basis Document for Texas City 

Chemicals, Inc., Texas City, Texas

DOCUMENT NUMBER/

DESCRIPTION:

SCA-TR-2018-SP004

REVISION NO.: 0 (Draft)

SUPERSEDES: N/A

EFFECTIVE DATE: May 18, 2018

TASK MANAGER Ron Buchanan, PhD, CHP [signature on file]

PROJECT MANAGER: John Stiver, MS, CHP [signature on file]

DOCUMENT 

REVIEWER(S):

John Stiver, MS, CHP [signature on file]

John Mauro, PhD, CHP [signature on file]

Record of Revisions

Revision 

Number

Effective 

Date

Description of Revision

0 (Draft) 5/18/2018 Initial issue
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TABLE OF CONTENTS

Abbreviations and Acronyms ......................................................................................................... 5

1 Introduction and Background ................................................................................................. 6

1.1 Texas City Chemicals SEC ............................................................................................. 6

1.2 Texas City Chemicals TBD ............................................................................................ 7

2 SC&A Original Findings from Review of 2008 SEC ER ....................................................... 8

3 TCC Internal Dose Reconstruction ....................................................................................... 10

3.1 Intakes from Development Work for the AEC ............................................................. 10

3.2 Intakes from Uranium Recovery Operations ................................................................ 10

3.2.1 Inhalation from Uranium Recovery Operations........................................................ 10

3.2.2 Ingestion from Uranium Recovery Operations ......................................................... 11

3.2.3 Radon Exposure from Uranium Recovery Operations ............................................. 11

3.3 Intakes from Phosphate Plant Operations ..................................................................... 11

3.3.1 Inhalation from Phosphate Plant Operations ............................................................ 12

3.3.2 Ingestion from Phosphate Plant Operations .............................................................. 12

3.3.3 Radon Exposure from Phosphate Plant Operations .................................................. 12

3.4 Combined Uranium Recovery and Plant Operations Intakes ....................................... 13

3.5 Intakes during the Residual Period ............................................................................... 13

3.5.1 Inhalation from Residual Period ............................................................................... 13

3.5.2 Ingestion from Residual Period ................................................................................ 14

3.5.3 Radon Exposure from Residual Period ..................................................................... 14

3.6 SC&A’s Evaluation of TCC Internal Dose Assessments............................................. 15

4 TCC External Dose Recontruction ....................................................................................... 16

4.1 External Dosimetry....................................................................................................... 16

4.2 External Exposure from Development Work for the AEC ........................................... 16

4.3 External Exposures from Uranium Recovery Operations ............................................ 16

4.3.1 Penetrating Dose from Uranium Recovery Operations ............................................ 16

4.3.2 Shallow Dose from Uranium Recovery Operations ................................................. 17

4.3.3 Shallow Dose from Contaminated Clothing from Uranium Recovery Operations .. 17

4.3.4 Hand and Forearm Dose from Uranium Recovery Operations................................. 17

4.4 External Exposures from Phosphate Plant Operations ................................................. 18

4.4.1 Penetrating Dose from Plant Operations ................................................................... 18

4.4.2 Shallow Dose from Plant Operations ........................................................................ 18

4.4.3 Shallow Dose from Contaminated Clothing from Plant Operations ........................ 18
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4.4.4 Hand and Forearm Dose from Plant Operations ....................................................... 18

4.5 External Exposures during the Residual Period ........................................................... 18

4.5.1 Penetrating Dose during the Residual Period ........................................................... 18

4.5.2 Nonpenetrating Dose during the Residual Period ..................................................... 19

4.6 Occupational Medical X-ray Examinations .................................................................. 19

4.7 SC&A’s Evaluation of TCC External Dose Assessments ............................................ 19

5 Summary and Conclusions ................................................................................................... 20

5.1 Original SEC ER Findings ............................................................................................ 20

5.2 Evaluation of TCC TBD ............................................................................................... 20

6 References ............................................................................................................................. 21
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ABBREVIATIONS AND ACRONYMS

ABRWH or 

Advisory Board Advisory Board on Radiation and Worker Health 

AEC Atomic Energy Commission

AWE Atomic Weapons Employer 

DOE U.S. Department of Energy 

dpm disintegrations per minute

EPA U.S. Environmental Protection Agency 

ER evaluation report 

FIPR Florida Institute of Phosphate Research

h hour 

ICRP International Commission on Radiological Protection 

keV kiloelectron volt

MCNPX Monte Carlo N-Particle Transport Code eXtended

mrad millirad

mrem millirem

NIOSH National Institute for Occupational Safety and Health

ORAUT Oak Ridge Associated Universities Team

OTIB ORAUT technical information bulletin

pCi picocurie 

R roentgen 

SDC Smith-Douglas Corporation 

SEC Special Exposure Cohort 

SRDB Site Research Database

TBD technical basis document

TCC Texas City Chemicals Inc.

U uranium 

WLM working level month 
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1 INTRODUCTION AND BACKGROUND

Construction on the Texas City Chemicals Inc. (TCC) plant in Texas City, Texas began in 1952. 

The plant was designed to produce animal feed and fertilizer from phosphate rock. The plant also 

had a contract with the Atomic Energy Commission (AEC) to construct a uranium recovery plant 

to extract uranium as a byproduct of the phosphates. TCC also had a development contract with 

the AEC to evaluate leach zone material. Preliminary operations began at both the new fertilizer 

plant and uranium recovery plant on October 5, 1953. The plant encountered a number of 

problems during startup, and the plant produced only a limited amount of uranium, 

approximately 300 pounds, for the AEC during the first few months of operation. Due to 

equipment problems, the plant never reached full-scale uranium production. TCC ceased 

operations in 1956 and filed for bankruptcy. Following bankruptcy in 1956, the Smith-Douglas 

Corporation (SDC) acquired TCC. SDC did not pursue uranium work with the AEC. SDC was 

later acquired by Borden Chemical, who operated the phosphate plant until it closed in 1977. 

1.1 TEXAS CITY CHEMICALS SEC

Petitioners filed a Special Exposure Cohort (SEC) petition in March 2007, covering the dates 

January 1, 1952, through December 31, 1956. On August 17, 2007, Petition SEC-0088 qualified 

for evaluation. The National Institute for Occupational Safety and Health (NIOSH) issued 

Revision 0 of the SEC petition evaluation report (ER) for Petition 0088 on January 18, 2008 

(NIOSH 2008). During the meeting of the Advisory Board on Radiation and Worker Health 

(Advisory Board) held on April 7–9, 2008, in Tampa, Florida, the Advisory Board directed 

SC&A, Inc. to perform a review of the TCC SEC-0088 ER. That report was issued July 18, 

2008, and identified nine findings (SC&A 2008). 

During the May 8, 2009, Use of Surrogate Data Work Group meeting, NIOSH reported that a 

series of developments, including the discovery of new information, since the initial issue of the 

ER led to the need to revise the ER. Because of this, SC&A’s findings in the ER review were not 

addressed in detail in the Use of Surrogate Data Work Group meeting. 

NIOSH amended the ER on October 19, 2010 (NIOSH 2010). The amended ER modified the 

covered period to October 5, 1953, through September 30, 1955, based on newly discovered 

documentation. The amended ER also recommended granting the SEC based on an inability to 

bound radon dose with sufficient accuracy. On November 17, 2010, the Advisory Board voted to 

accept the NIOSH SEC class recommendation. The SEC class includes:

All Atomic Weapons Employer employees who worked at Texas City Chemicals, 

Inc., from October 5, 1953, through September 30, 1955, for a number of work 

days aggregating at least 250 work days, occurring either solely under this 

employment or in combination with work days within the parameters established 

for one or more other classes of employees included in the Special Exposure

Cohort. [NIOSH 2010, page 4]
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1.2 TEXAS CITY CHEMICALS TBD

NIOSH issued a technical basis document (TBD) for TCC, DCAS-TKBS-0011, Revision 00, 

Technical Basis Document for Texas City Chemicals, Inc. Texas City, Texas (2017; hereafter 

“TCC TBD”), to address exposures to workers for all cancers that are not covered by the SEC, 

and also for the residual period doses. In December 2017, the Advisory Board tasked SC&A 

with the review of the TCC TBD. This review addresses that tasking. 
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2 SC&A ORIGINAL FINDINGS FROM REVIEW OF 2008 SEC ER

In order to properly evaluate the TCC TBD, SC&A also reevaluated the related SEC findings 

from SC&A’s review (SC&A 2008) of NIOSH’s original ER (NIOSH 2008), in view of the 

revised NIOSH evaluation report (NIOSH 2010) and the recently released TCC TBD. The nine 

findings associated with the SC&A 2008 ER review have not been resolved and/or formally 

closed out. The revised ER and newly issued TCC TBD addressed many of the findings; 

however, the findings remain open or in progress. As part of this review, SC&A makes 

recommendations on paths forward for each of these original findings. 

Finding 1: The petitioners’ class definition needs to be re-examined to insure that 

the time period has been properly justified. 

The revised ER adequately addressed this finding. The revised ER changed the covered period to 

October 5, 1953, through September 1955. SC&A recommends this finding should be closed. 

Finding 2: The use of mean annual external exposures observed among 

phosphogypsum workers in Idaho does not appear to be a scientifically sound or 

claimant-favorable surrogate for pre-operational phosphate ore handlers at TCC. 

Consideration should be given to using the upper 95th percentile exposures for 

Florida phosphate rock workers as a more appropriate claimant-favorable 

surrogate. 

The current Atomic Weapons Employer (AWE) period does not include a pre-operational period. 

The SEC period, uranium recovery, plant operations, and residual periods have been redefined 

by the current SEC, the revised ER, and the TCC TBD; therefore, this finding is no longer 

applicable and SC&A recommends that this finding be closed. 

Finding 3: An alternative modeling approach based on reasonable assumptions 

derived from the available information suggests that external doses could be two 

orders of magnitude lower than those developed by NIOSH. NIOSH should 

reexamine its modeling approach to insure that its assumptions for calculating 

external doses are representative of plausible circumstances.

The use of approximately 400 pounds of uranium oxide for the external dose calculation would 

be more realistic and still be claimant favorable. NIOSH took this into account in the revised ER

and TCC TBD. SC&A recommends that this finding be closed.

Finding 4: NIOSH should consider data from FIPR 1998 as an alternative source 

of data for estimating internal exposures. 

Finding 4 refers to pre-operational internal exposures. The current AWE period does not include 

a pre-operational period. The SEC period, uranium recovery, plant operations, and residual 

periods have been redefined by the current SEC, the revised ER, and the TCC TBD; therefore, 

this finding is no longer applicable and SC&A recommends that this finding be closed. 
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Finding 5: The assumption that workers were exposed to yellowcake for 39 

months, while claimant favorable, is not consistent with the available data and 

may overstate the exposure by an order of magnitude. 

The revised ER adequately addressed this finding. Covered exposures from the uranium recovery 

building ended in March 1954, rather than the 39-month exposure period assumed by NIOSH in 

the original ER. Exposure to yellowcake dust beyond March 1954 could only have come from 

residual contamination. This is reflected in the TCC TBD and revised ER. SC&A recommends 

this finding be closed.

Finding 6: NIOSH should consider other data sources in addition to EPA 1978 to 

estimate internal exposures to workers outside the uranium recovery building, 

such as FIPR 1998. 

As recommended in SC&A’s finding, the revised ER and the TCC TBD included analyses of

data from other studies, such as from the Florida Institute of Phosphate Research (FIPR 1998), in 

evaluating internal exposures to workers outside the uranium recovery building (NIOSH 2010, 

pages 29–34). SC&A recommends this finding be closed. 

Finding 7: The approach used in the evaluation report to reconstruct internal 

exposures to uranium production operations appears to be unrealistically 

conservative with regard to exposure duration and exposure level. 

The revised ER states that covered exposures from the uranium recovery plant ended in March 

1954, rather than the 39-month exposure period assumed by NIOSH in the original ER. Exposure 

to yellowcake dust beyond March 1954 could only have come from residual contamination. This 

a more realistic exposure period. Therefore, SC&A recommends this finding be closed. 

Finding 8. The methodology used to estimate inadvertent ingestion should be 

revised. 

NIOSH used the procedures recommended in OCAS-TIB-009, Revision 0, Estimation of 

Ingestion Intakes (2004), in the SEC ERs and the TCC TBD. Since this finding by SC&A, the 

issues concerning ingestion have been addressed and resolved by the OCAS-TIB-009 Work 

Group and closed on February 5, 2013. Therefore, SC&A recommends this finding be closed. 

Finding 9: NIOSH should consider adjustments to the dataset used to calculate 

radon doses to fully reflect the available information. This would increase the 

dose from 0.112 WLM/year [working level month per year] to 0.56 WLM/year. 

Should NIOSH determine that the value they selected is, in fact, appropriate for 

the reasons discussed in the main body of this report, the rationale for this 

conclusion should be provided in the evaluation report. 

The Advisory Board, based on the inability to reconstruct radon doses during the operational 

period, granted the SEC class; therefore, this finding is no longer relevant. SC&A recommends 

this finding be closed.
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3 TCC INTERNAL DOSE RECONSTRUCTION

There are no internal monitoring data available for employees during any time at TCC. The TCC 

TBD assumed there were four possible internal dose pathways: development work for the AEC, 

phosphate plant operations, uranium recovery operations for the AEC, and the residual period. 

3.1 INTAKES FROM DEVELOPMENT WORK FOR THE AEC

Due to the nature of the research and development work performed by TCC, intakes from these 

activities were assumed lower than those from work in the production activities; therefore, 

research and development work was not assessed by NIOSH. After evaluating the available 

documentation, SC&A concurs that these activities would not result in intakes greater than either 

the phosphate operations or the uranium recovery operations. 

3.2 INTAKES FROM URANIUM RECOVERY OPERATIONS

During its short time of operations, TCC extracted approximately 400 pounds of uranium. This 

mass of uranium would fill less than half of a 55-gallon drum. To evaluate possible intake, 

NIOSH assumed 100 pounds per month production of material from October 1953 through 

March 1954. Although this assumption over predicts the material produced, NIOSH argues that, 

“it provides a reasonable assurance that the timeframe of production is accounted for and that 

reconstructed doses from uranium recovery are favorable” (TCC TBD, page 9). SC&A finds 

this argument acceptable, given the unknown production timetables at the site. This further 

breaks down to an estimated 25-pound batch per week.

3.2.1 Inhalation from Uranium Recovery Operations 

In the SEC ER (NIOSH 2010) and the TCC TBD, NIOSH assumed that the production process

at TCC was similar to that at the Blockson Chemical Company, as described in OCAS-TKBS0002, Revision 04, Technical Basis Document for Atomic Energy Operations at Blockson 

Chemical Company, Joliet, Illinois (2014). Each batch would have been in process for 2 days, 

which allowed time for filtering, drying, and packaging the materials. Drying and packaging are 

known to create a significant inhalation risk. NIOSH cites a Christofano and Harris 1960 study 

on industrial hygiene at uranium processing facilities as the basis for using an air concentration 

of 190 disintegration per minute per meter cubed (dpm/m3

). This value comes from Table 2 of 

that reference and represents the maximum of the daily average exposures, which ranged from 

90 to 190 dpm/m3, with an average value of 140 dpm/m3. NIOSH chose the upper limit 

(190 dpm/m3

) of these daily average exposures and converted this to a uranium-238 (U-238) 

exposure of 1,027 picocuries (pCi) per week, based on a breathing rate of 1.2 m3/h and 

2,500 hours per year (190 gross alpha dpm/m3 × 1.2 m3/h × 10 hours/workday × 1 pCi/2.22 dpm 

× 2 workdays/week × 0.5 U-238 dpm/gross alpha dpm = 1,027 U-238 pCi/week). The relative 

ratios of the other radionuclides for the uranium recovery work are provided in Table 1 of the 

TCC TBD.

SC&A found that the TCC TBD and revised ER presented lower intake values per calendar day 

than the original ER. Although the revised intake values still appear large for the relatively small 

volume of material processed at TCC compared to the other facilities used in the Christofano and 
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Harris 1960 study, the few workers who did perform the uranium recovery operations at TCC 

were potentially exposed to comparable inhalation intakes at the time. 

3.2.2 Ingestion from Uranium Recovery Operations

NIOSH used the procedures recommended in OCAS-TIB-009 in the ERs and the TCC TBD to 

derive intake by ingestion during the uranium recovery period. Intake by ingestion issues have 

been addressed by the OCAS-TIB-009 Work Group and resolved. A summary of the 

recommended inhalation and ingestion intakes for the uranium recovery period (October 5, 1953, 

through March 31, 1954) is provided in Table 7 of the TCC TBD. SC&A has verified the values 

in this table.

Although the revised ingestion values may appears large for the relatively small volume of 

material processed at TCC compared to the other facilities used in the Christofano and Harris 

1960 study, the few workers who did perform the uranium recovery operations at TCC were 

potentially exposed to comparable ingestion intakes at the time.

3.2.3 Radon Exposure from Uranium Recovery Operations 

Radon exposures were possible during the uranium recovery operations. However, NIOSH has 

concluded, and the Secretary of Health and Human Services has concurred, that radon exposures 

cannot be estimated with sufficient accuracy from October 5, 1953, through September 30, 1955. 

Therefore, a class of TCC workers has been added to the TCC SEC for that period. 

3.3 INTAKES FROM PHOSPHATE PLANT OPERATIONS

The intakes for phosphate plant workers at TCC is based on a limiting phosphate dust 

concentration of 50.4 mg/m3

. This value is the maximum measured dust concentration at the 

Idaho plant from a survey by the U.S. Environmental Protection Agency (EPA). The EPA 

performed a thorough study of dust-loading and radionuclide concentrations in air throughout the 

phosphate ore process at an Idaho phosphate facility (EPA 1978). The facility used the wetprocess method to process phosphate rock, a process comparable to that used at TCC. Various air 

samples were taken at locations throughout the Idaho plant. The samples were analyzed for total 

dust-loading, and airborne radioactivity concentrations were reported. To obtain this dust loading 

(50.4 mg/m3), NIOSH used the mass of dust collected (0.2742 gram from Table 12) during the 

flow of 5.44 m3 of air through a particulate sampler (EPA 1978). According to NIOSH, that 

concentration provides an upper bound average particulate concentration to which an employee 

would have been exposed. 

During its SEC ER review, SC&A suggested NIOSH consider other data, such as FIPR 1998 

(SC&A’s Finding 6). The revised ER did consider this, as well as FIPR 1995. NIOSH concluded 

that those studies are less applicable because of modern engineering techniques that reduced the 

dust generation at the plant. 

SC&A has examined another approach to the issue of developing a claimant-favorable approach

to air concentrations and intakes that would complement the use of the distribution developed by 

NIOSH. A paper by Wesley R. Van Pelt Associates (Van Pelt 2005) was commissioned by 
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SC&A in 2005. That paper performed an evaluation of air dust concentrations in industrial 

settings. Its conclusion was as follows:

While it is impossible to predict the maximum likely dust concentration to which a 

worker would be exposed in an industrial setting, it is possible to construct some 

likely bounds on the largest dust concentration likely to occur. ...it is my opinion 

that the maximum likely dust concentration in the breathing zone of a worker 

without a respirator would be about 30 mg/m3 for exposures lasting many hours 

per day and about 300 mg/m3 for exposures lasting only 5 or 10 minutes or less.

[pages 3–4]

NIOSH’s model assumes a dust loading of 50.4 mg/m3, whereas the Wesley R. Van Pelt 

Associates study concluded 30 mg/m3 as being reasonably bounding, which is similar to the 

second highest values of 33.9 mg/m3 derived from Table 14 (0.3998 g ÷ 11.8 m3 × 1,000 mg/g = 

33.9 mg/m3) of the EPA study (EPA 1978). Based on this information, it would appear that 

NIOSH selected the more conservative upper value of 50.4 mg/m3. 

SC&A finds this approach reasonable and claimant favorable. 

3.3.1 Inhalation from Phosphate Plant Operations

NIOSH assumed that, with a bounding air dust loading of 50.4 mg/m3, a 2,500-hour work year 

and a breathing rate of 1.2 m3/h 

50.4 mg/m3 × 1.2 m3/h × 2,500 hours/year = 151,200 mg/year = 151.2 g/year inhaled. 

This is converted to activity based on the bounding radionuclide concentrations presented in 

Table 5-6 of the SEC ER (NIOSH 2010). SC&A verified the concentrations recommended in 

Table 5-6. Although it is possible that some radionuclides could temporarily be present in higher 

concentrations than presented, continuous exposure to the concentrations used provides a 

bounding source term for internal exposure. 

3.3.2 Ingestion from Phosphate Plant Operations

NIOSH used the procedures recommended in OCAS-TIB-009 in the SEC ERs and the TCC TBD 

to derive intake by ingestion during the phosphate operational period. A summary of the 

recommended inhalation and ingestion intakes for the phosphate operational period (April 1, 

1954, through September 30, 1955) is provided in Table 7 of the TCC TBD. SC&A has verified 

the values in this table.

3.3.3 Radon Exposure from Phosphate Plant Operations

Radon exposures were possible from the radium in the phosphate ores and in the 

phosphogypsum waste. However, NIOSH has concluded, and the Secretary of Health and 

Human Services has concurred, that radon exposures cannot be estimated with sufficient 

accuracy from October 5, 1953, through September 30, 1955. Therefore, a class of TCC workers 

has been added to the TCC SEC for that period. 
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3.4 COMBINED URANIUM RECOVERY AND PLANT OPERATIONS INTAKES

The TCC TBD provides 1953 through 1977 recommended annual intakes in Table 8 for 

inhalation and in Table 9 for ingestion.

Observation 1 – Combined Intakes

As written, SC&A finds that TCC TBD Tables 8 and 9 have the potential to be incorrectly 

interpreted, leading to unintentional underestimates of dose during the operational years. 

Calendar-day intakes are intended to be applied over an entire year, even when employment does 

not cover the entire calendar year. For example, the 1953 U-238 pCi/calendar day intake in 

Table 8 is presented as 41.3 pCi/day, and the covered period at the site begins October 5, 1953. 

Intuitively, this would result in an intake of 41.3 pCi for 87 days, or 3,593 pCi of U-238; 

however, this is incorrect. Instead, the table intends for the dose reconstructor to multiply 

41.3 pCi by 365 days, despite the covered period beginning on October 5. The table notes seem 

to suggest the proper way to calculate annual dose; however, they have ambiguities, and note 1 

references a nonexistent note 3. SC&A would suggest intake per calendar day be converted to 

true annual intakes or further clarification added to the table to prevent misinterpretation. 

3.5 INTAKES DURING THE RESIDUAL PERIOD

The residual contamination period was October 1, 1955, through December 31. 1977. The 

following outlines NIOSH’s recommended procedure to derive the associated inhalation and 

ingestion intakes during this period. 

3.5.1 Inhalation from Residual Period

For the residual period (as outlined on pages 10 and 11 of the TCC TBD), NIOSH used the 

average source term depletion rate from ORAUT-OTIB-0070, Revision 01, Dose Reconstruction 

during Residual Radioactivity Periods at Atomic Weapons Employer Facilities (2012), and a 

resuspension factor of 1×10-5 per meter. NIOSH used a 2,500-hour work-year and a 1.2 m3/h

breathing rate to estimate the surface contamination resulting from the settling of 190 dpm/m3

airborne uranium, the bounding concentration assumed for uranium recovery. Suspended 

particulates were assumed to have settled out of the air for 30 days with a settling velocity of 

7.5×10-4 m/s. NIOSH assumed 190 dpm/m3 for 30 days, resulting in a total uranium 

contamination of 3.69×105 dpm/m2. NIOSH applied a resuspension factor of 1×10-5/m to the 

contamination level to determine a total uranium airborne concentration of 3.69 dpm/m3

; half of 

the uranium intake was assigned to U-238. NIOSH assumed a 2,500 hour work-year and a 

1.2 m3

/h breathing rate. The resulting U-238 intake rate was 6.84 pCi per calendar day starting 

April 1, 1954. The depletion factors for the residual period are listed in TBD Table 5. These 

depletion factors were based on a deletion rate of 0.00067/d as recommend in ORAUT-OTIB0070. 

However, during the AWE operational period (through September 1955), intakes estimates for 

phosphate plant work were higher. Therefore, residual intakes from uranium recovery work were 

not assigned until the beginning of the residual contamination period, October 1, 1955. 
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NIOSH used depletion factors, which are based on a given rate of source depletion at 1-year 

intervals, from ORAUT-OTIB-070, starting with an initial factor of 1.0 for the first year (1955). 

For the TCC TBD calculations, the 1.0 depletion factor was applied for April 1, 1954, through 

the end of 1955. 

The factors applicable to each year are provided in Table 5 for the period 1955 through 1977. 

The resulting U-238 intake values in TBD Tables 8 (inhalation) and 9 (ingestion) for 1955 

through 1977 were derived from multiplying the annual intake value of 6.84 pCi per calendar 

day by the depletion factor in Table 5. The 1955 intake values in Tables 8 and 9 are a 

combination of phosphate plant operations and the residual period intakes, as stated in the 

footnotes to the tables. 

3.5.2 Ingestion from Residual Period

NIOSH used the procedures recommended in OCAS-TIB-009, the TCC SEC ERs, and the TCC 

TBD to derive intake by ingestion during the residual period. According to the TCC TBD, pages 

10 and 11, this consisted of applying a factor of 0.2 to the air concentration as a function of time 

to estimate daily ingestion. A summary of the recommended ingestion intakes for the residual 

period (1955 through 1977) is provided in Table 9 of the TCC TBD. SC&A has verified the 

values in Table 9. 

Observation 2 – Apparent Inconsistence in Ingestion Method Used During Residual Period

While NIOSH followed the procedure in OCAS-TIB-009 for deriving ingestion intakes during 

the TCC residual period, a different procedure was used in NIOSH’s SEC-00236 ER during the 

residual period for the Metals and Control Corporation (NIOSH 2017). According the SEC00236 ER, page 29, the ingestion intake (in units of dpm/hour) was derived by applying a factor 

of 1×10-4 m2

/hour to the surface contamination levels (in units of dpm/m2) as a function of time. 

The TCC and the Metals and Control Corporation residual situations appear to be similar;

therefore, it is not apparent why different methods were used to derive ingestion intake values 

during the residual period.

3.5.3 Radon Exposure from Residual Period

There were radon flux monitoring results available for the phosphogypsum stacks at TCC taken 

from February 1983 through September 1984. The highest reading was 0.42 pCi/l. NIOSH 

assumed that the radon flux was five times greater during the residual period due to lack of crust 

on the piles. The highest radon reading would have been 2.1 pCi/l and was assumed to the 

bounding exposure during the residual period. As outlined on pages 41 and 42 of the revised 

SEC ER (NIOSH 2010), the percentage of AEC-related radon exposure was estimated to be 

approximately 18% of the total in 1955 (the beginning of the AEC residual period) and remained 

at 18% through the phosphate plant dormant period of 1956 and 1957. Then, during the 

phosphate plant’s activity operational period of 1958 through 1971, the relative amount from 

AEC-related work decreased each year of phosphate plant operations to 0.4% in 1971. 

Multiplying the appropriate AEC-related fraction by 2.1 pCi/l resulted in the AEC radon 

exposure as listed in Column 2 of Table 6 of the TCC TBD. Assuming a 0.4 equilibrium factor, 
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100 pCi/l per working level, and 2,500 hours worked per year, resulted in the AEC-related radon 

WLM values as listed in Column 3 of Table 6. 

Although it is possible that the uranium recovery operations may not have added any additional

materials to the piles, it appears that NIOSH has considered phosphate ore that was processed to 

recover uranium as additional material in the piles concerning radon intake during the residual 

period. SC&A would like NIOSH to confirm that this was their intent in the TCC TBD.

3.6 SC&A’S EVALUATION OF TCC INTERNAL DOSE ASSESSMENTS

SC&A evaluated NIOSH’s recommendations for internal dose assessment in the TCC TBD. 

Because there were no radiological measurements performed during the operations of the 

facility, surrogate data from other similar facilities must be relied upon. There is a wide range 

and variety of such facilities. SC&A found that, for the most part, NIOSH selected parameters to 

provide plausible but upper-bound intake values, which are claimant favorable.
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4 TCC EXTERNAL DOSE RECONTRUCTION

4.1 EXTERNAL DOSIMETRY

There are no dosimetry data or radiation measurements available for TCC. Therefore, NIOSH 

considered worker external doses using source-term information and measured doses of 

phosphate plant workers according to OCAS-IG-004, Revision 0, The Use of Data from Other 

Facilities in the Completion of Dose Reconstructions Under the Energy Employees Occupational 

Illness Compensation Program Act (2008). The values NIOSH used provided an upper bound 

and are therefore to be assigned as constants in the dose reconstruction process.

4.2 EXTERNAL EXPOSURE FROM DEVELOPMENT WORK FOR THE AEC

NIOSH found that doses from the AEC research with small quantities of phosphate ores were 

presumed lower than from work in the uranium recovery or production areas; therefore, dose 

from the development work was not assessed. After evaluating the available documentation, 

SC&A concurs that these activities would not result in exposures greater than either the uranium 

recovery operations or the phosphate operations. 

4.3 EXTERNAL EXPOSURES FROM URANIUM RECOVERY OPERATIONS

The applicable dates that these external doses are to be applied are October 5, 1953, through 

March 31, 1954. 

4.3.1 Penetrating Dose from Uranium Recovery Operations

NIOSH used the Monte Carlo N-Particle Transport Code eXtended (MCNPX) (version 2.7b) to 

determine the dose rate per curie of U-238 in a drum. A density of 2 g/cm3 was chosen to provide 

a claimant-favorable geometry. Photon flux was evaluated at 30 cm and 100 cm from the edge of 

the drum at a height of 77.9 cm above the floor. Factors from ICRP Publication 74 (1996) were 

used to convert the photon flux to units of air kerma. Results are provided in Table 10 of the 

TCC TBD. 

The exposure time for external dose during uranium recovery was based on the assumptions of 

intermittent work. During the period of operation of the uranium recovery plant, it is assumed the 

intermittent uranium extraction work was a 2-day-per-week process and that a worker spent 20% 

of the time over those 2 days at a distance of 30 cm (1 foot) from a drum of product. For an 

assumed 10-hour work day, a worker would spend 4 hours per week at a distance of 30 cm from 

the drum. This exposure scenario also allowed for work in close proximity to uranium 

concentrates in other locations in the building, such as working with filter presses or manually 

transferring the material. Assuming a 50-hour work week, a worker could have been working in 

the building for an additional 46 hours at a lower exposure rate doing tasks that did not involve 

direct handling of uranium concentrate. Exposure during that time was modeled by assuming a 

general area dose rate that is equivalent to the dose rate at 100 cm (3 feet) from the drum of 

material. Thus the weekly external whole-body photon dose is calculated by assuming 4 hours 

exposure at 30 cm and 46 hours exposure at 100 cm from the drum of material. Applying the 

dose rates from Table 10 of the TCC TBD to the assumed hours results in a weekly dose of 
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0.0397 rad (air kerma), or 0.0057 rad per calendar day. The dose is to be applied as 50% 30–

250 kiloelectron volt (keV) photons and 50% >250 keV photons. The derivation of this dose is 

outlined on pages 16 and 17 and summarized in Table 11 of the TCC TBD. 

4.3.2 Shallow Dose from Uranium Recovery Operations

For nonpenetrating beta dose from the recovered uranium concentrates at TCC, NIOSH used the 

estimated dose rates at 30 cm from the surface of yellowcake, adjusted for additional 

radionuclides at TCC. The resulting dose rate was 3.6 millirem (mrem)/h. Dose was modeled 

based on a 50-hour work week. It was assumed workers were exposed to uranium concentrates 

for 20 hours per week at 3.6 mrem/h during the period of intermittent uranium recovery work, 

resulting in 72 mrem/week. For the remaining 30 hours per week, beta exposure from phosphates 

was assumed at a rate of 0.028 mrem per hour, resulting in an additional 0.84 mrem. This 

resulted in a weekly beta dose of 0.073 rem, or 0.010 rem/calendar day. Doses are to be applied 

as electrons >15 keV. The derivation of this dose is outlined on page 18 and summarized in 

Table 11 of the TCC TBD. 

4.3.3 Shallow Dose from Contaminated Clothing from Uranium Recovery Operations

NIOSH used the average shallow dose rates from contaminated clothing at Mallinckrodt of 

1.5 mrem/h (AEC 1958). The Mallinckrodt dose rate was used as a bounding condition for TCC 

because Mallinckrodt handled materials of similar radiological constituents, but in larger 

quantities and with a higher radioactive material content. NIOSH assumed that, during uranium 

recovery at TCC, the workers were exposed to that level for 10 hours per week, which is 

considered an upper-bound condition. This results in a dose to the skin of 15 mrem/week, or 

0.0021 rem/calendar day. Doses are to be applied as electrons > 15keV. The derivation of this 

dose is outlined on page 18 and summarized in Table 11 of the TCC TBD. 

4.3.4 Hand and Forearm Dose from Uranium Recovery Operations

Extremity dose was considered for operators and maintenance workers who may have had direct 

contact with the uranium concentrates during uranium recovery. NIOSH made an estimate of 

shallow dose to the hands and forearms based on direct contact with yellowcake. Surface dose 

rates on yellowcake have been reported to be approximately 203 millirad (mrad) per hour (DOE 

2000). The reported dose rates were modified to reflect exposure conditions at the TCC during 

uranium recovery. A factor of 1.8 was applied to the 203 mrad/h dose rate from yellowcake to 

allow for additional radionuclides assumed to be present in the uranium concentrates at TCC, 

resulting in a beta dose rate of 365 mrad/h. Extremity dose modeling during the period of 

intermittent operation of the uranium recovery plant was based on 1 hour of contact with the 

recovered uranium concentrate per week (1 hour × 365 mrad/h), and an additional 5 hours per 

week of contact with phosphates in other buildings (5 hours × 2.8 mrad/h = 14 mrad). This 

results in a weekly extremity dose of 379 mrad, or 0.054 mrem/calendar day. This dose is to be 

applied to the hands and forearms of operators and maintenance worker as electrons >15 keV. 

The derivation of this dose is outlined on page 19 and summarized in Table 11 of the TCC TBD. 
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4.4 EXTERNAL EXPOSURES FROM PHOSPHATE PLANT OPERATIONS 

The applicable dates that these external doses are to be applied are April 1, 1954, through 

September 30, 1955. 

4.4.1 Penetrating Dose from Plant Operations

NIOSH used the highest annual dose value of 210 mrem from the FIPR 1998 study of phosphate 

processing plants. This equates to 0.00060 rem per calendar day and is to be assigned as 50% 

30–250 keV and 50% >250 keV photons. The derivation of this dose is outlined on page 16 and 

summarized in Table 11 of the TCC TBD. 

4.4.2 Shallow Dose from Plant Operations

NIOSH used the estimated nonpenetrating beta dose at 30 cm from the surface of yellowcake for 

phosphate materials, adjusted for additional radionuclides and uranium concentration, as 

specified in the TCC ER, Section 7.3.4.1 (NIOSH 2010). The resulting dose rate was 

0.028 mrem/h. For a 2,500 hour work year, this results in an annual beta dose of 0.070 rem, or a 

dose of 0.00020 rem per calendar day. This dose is to be assigned as >15 keV electrons. The 

derivation of this dose is outlined on page 18 and summarized in Table 11 of the TCC TBD. 

4.4.3 Shallow Dose from Contaminated Clothing from Plant Operations

According to page 18 of the TCC TBD, electron dose from work clothing in the phosphate plant 

was considered insignificant due to the relatively low concentration of radionuclides. 

4.4.4 Hand and Forearm Dose from Plant Operations 

NIOSH considered extremity dose for operators and maintenance workers who may have had 

direct contact with phosphate materials in the plant. Surface dose rates on yellowcake have been 

reported to be about 203 mrad per hour (DOE 2000). For the phosphate plant, the 203 mrad/h 

dose rate was multiplied by a factor of 4.3 to allow for radionuclides associated with the uranium 

at TCC, then divided by 312 to adjust for the much lower concentration of uranium. The 

resulting dose rate is 2.8 mrad/h. NIOSH assumed 6 hours per week of direct contact at the rate 

of 2.8 mrad/h, resulting in a weekly dose of 17 mrad, or 0.0024 rem/calendar day. This dose is 

to be applied to the hands and forearms (operators and maintenance workers) as electrons 

>15 keV. The derivation of this dose is outlined on page 19 and summarized in Table 11 of the 

TCC TBD.

4.5 EXTERNAL EXPOSURES DURING THE RESIDUAL PERIOD

The applicable dates that these external doses are to be applied are October 1, 1955, through 

December 31, 1977. 

4.5.1 Penetrating Dose during the Residual Period

NIOSH considered external dose from residual contamination in the uranium recovery building. 

Measured dose rates from contamination in the Blockson Chemical Company uranium recovery 
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facility were used to bound dose from residual contamination at TCC. Blockson’s uranium 

recovery plant was in production for over 7 years with essentially the same source term. Dose 

rates on surfaces in that facility provided a bounding estimate for TCC during the residual 

period. Based on information in Section 5.0 of the Blockson TBD, OCAS-TKBS-0002, the dose 

from residual contamination at TCC was assumed to be 0.06 roentgen (R)/year, or 

0.00016 R/calendar day. The derivation of this dose is outlined on page 19 and summarized in 

Table 11 of the TCC TBD. 

4.5.2 Nonpenetrating Dose during the Residual Period

NIOSH did not consider nonpenetrating (beta) dose from residual contamination separately 

because the 0.060 R/year dose rate estimates provided for Blockson was based on dose rate 

measurements taken with an instrument that was sensitive to both photon and beta radiation 

(DOE 1983). 

4.6 OCCUPATIONAL MEDICAL X-RAY EXAMINATIONS

Neither SC&A nor NIOSH located any specific information on required medical X-rays during 

the AWE operational period. The contract between the AEC and TCC had a provision requiring 

TCC “to conform to all minimum health and safety regulations and requirements of the 

Commission” (AEC 1953). NIOSH instructs dose reconstructors to assume an annual chest X-ray 

examination to have been required during the AEC covered period of 1953 through 1955 and 

instructs dose reconstructors to follow the guidance in ORAUT-OTIB-0006, Revision 04, Dose 

Reconstruction from Occupational Medical X-ray Procedures (2011). 

4.7 SC&A’S EVALUATION OF TCC EXTERNAL DOSE ASSESSMENTS

SC&A evaluated NIOSH’s recommendations for external dose assessment in the TCC TBD. 

Because there were no exposure measurements performed during the operation of the facility, 

surrogate data from other similar facilities must be relied upon. There is a wide range and variety 

of such facilities. SC&A found that, for the most part, NIOSH selected parameters to provide 

plausible but upper-bound exposure values, which are claimant favorable. The doses are to be 

assigned as constants because the doses are considered to be upper bounds. 

SC&A had no findings or observations concerning occupation external exposures. 
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5 SUMMARY AND CONCLUSIONS

5.1 ORIGINAL SEC ER FINDINGS

SC&A analyzed the original findings from SC&A’s 2008 review of the 2008 SEC ER in view of 

NIOSH’s revised 2010 SEC ER and the recent TCC TBD. SC&A found that the original findings 

from SC&A’s evaluation of the 2008 SEC ER have all been addressed and resolved by the 

revised 2010 SEC ER and the TCC TBD. SC&A recommends closure of the original SEC

findings. 

5.2 EVALUATION OF TCC TBD

SC&A evaluated the TCC TBD and did not identify any findings associated with the methods 

and procedures NIOSH used in the TCC TBD to reconstruct dose for TCC claimants. SC&A 

found NIOSH’s recommendations were generally based on claimant-favorable assumptions, and 

SC&A did not identify any technical errors in the TCC TBD. SC&A did have two observations 

concerning the TCC TBD: 

• Observation 1 – Combined Intakes: As written, SC&A finds that the TCC TBD Tables 

8 and 9 have the potential to be incorrectly interpreted, leading to unintentional 

underestimates of dose during the operational years.

• Observation 2 – Apparent Inconsistence in Ingestion Method Used during Residual 

Period: While NIOSH followed the procedure in OCAS-TIB-009 for deriving ingestion 

intakes during the TCC residual period, a different procedure was used in NIOSH’s SEC00236 ER during the residual period for the Metals and Control Corporation (NIOSH 

2017). 
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6 REFERENCES

AEC 1953. Contract No. AT(49-1)-647, U.S. Atomic Energy Commission, Washington, DC. 

May 12, 1953. [SRDB Ref. ID 16646, PDF pages 49–67]

AEC 1958. Symposium on Occupational Health Experience and Practices in the Uranium 

Industry, U.S. Atomic Energy Commission, held in New York City. October 15–17, 1958. 

[SRDB Ref. ID 7886]

EPA 1978. Radiological Surveys of Idaho Phosphate Ore Processing—The Wet Process Plant, 

Technical Note ORP/LV-78-1, U. S. Environmental Protection Agency, Las Vegas, NV.

April 1978. [SRDB Ref. ID 30886]

Christofano and Harris 1960. Emil Christofano and William B. Harris, “The Industrial Hygiene 

of Uranium Refining,” Environmental Health, Vol. 1, No. 5. November 1960. [SRDB Ref. 

ID 15774]

DCAS-TKBS-0011. 2017. Technical Basis Document for Texas City Chemicals, Inc. Texas City, 

Texas, Revision 00, National Institute for Occupational Safety and Health, Cincinnati, OH. 

November 2, 2017.

DOE 1983. Formerly Utilized MED/AEC Sites Remedial Action Program Radiological Survey of 

Chemicals Group, Olin Corporation (formerly Blockson Chemical Company) Joliet, Illinois, 

March 27-November 28, 1978, DOE/EV-0005/35, Argonne National Laboratory for U.S. 

Department of Energy, Washington, DC. May 1983. [SRDB Ref. ID 23615]

DOE 2000. DOE Standard, Guide of Good Practices for Occupational Radiological Protection 

in Uranium Facilities, DOE-STD-1136-2000, U. S. Department of Energy, Washington, DC. 

August 2000. [SRDB Ref. ID 4617]

FIPR 1995. Microbiology and Radiochemistry of Phosphogypsum, Publication No. 05-035-115, 

Florida Institute of Phosphate Research. May 1995. [SRDB Ref. ID: 30136]

FIPR 1998. Evaluation of Exposure to Technologically Enhanced Naturally Occurring 

Radioactive Materials (TENORM) in the Phosphate Industry, Publication No. 05-046-155, 

Florida Institute of Phosphate Research. July 1998. [SRDB Ref. ID 18076]

ICRP 1996. Conversion Coefficients for Use in Radiological Protection against External 

Radiation, International Commission on Radiological Protection, ICRP Publication 74,

Ann. ICRP 26 (3-4). 1996.

NIOSH 2008. SEC Petition Evaluation Report Petition SEC-00088, Revision 0, National 

Institute for Occupational Safety and Health, Cincinnati, OH. January 18, 2008.

NIOSH 2010. SEC Petition Evaluation Report Petition SEC-00088, Revision 1, National 

Institute for Occupational Safety and Health, Cincinnati, OH. October 18, 2010.
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NIOSH 2017. SEC Petition Evaluation Report Petition SEC-00236, Revision 0, National 

Institute for Occupational Safety and Health, Cincinnati, OH. April 5, 2017.

OCAS-TKBS-0002. 2014. Technical Basis Document for Atomic Energy Operations at Blockson 

Chemical Company, Joliet, Illinois, Revision 04, National Institute for Occupational Safety and 

Health, Cincinnati, OH. May 19, 2014.

OCAS-IG-004. 2008. The Use of Data from Other Facilities in the Completion of Dose 

Reconstructions Under the Energy Employees Occupational Illness Compensation Program Act, 

Revision 0, National Institute for Occupational Safety and Health, Cincinnati, OH. August 21, 

2008.

OCAS-TIB-009. 2004. Estimation of Ingestion Intakes, Revision 0, National Institute for 

Occupational Safety and Health, Cincinnati, OH. April 13, 2004.

ORAUT-OTIB-0006. 2011. Dose Reconstruction from Occupational Medical X-ray Procedures,

Revision 04, National Institute for Occupational Safety and Health, Cincinnati, OH. June 20, 

2011. 

ORAUT-OTIB-0070. 2012. Dose Reconstruction during Residual Radioactivity Periods at 

Atomic Weapons Employer Facilities, Revision 01, National Institute for Occupational Safety 

and Health, Cincinnati, OH. March 5, 2012.

SC&A 2008. A Focused Review of the NIOSH Evaluation Report for the Texas City Chemical 

Company SEC Petition, SCA-SEC-TASK5-0063, Revision 0 – Draft, SC&A, Inc., Vienna, VA. 

July 18, 2008.

Van Pelt 2005. Maximum Likely Dust Cloud, Wesley R. Van Pelt Associates, Inc. Paramus, NJ.

January 30, 2005. [SRDB Ref. ID 172015]