Review of Battelle-TIB-5000 

Default Assumptions and 

Methods for AWE Sites

Robert Anigstein, PhD, SC&A, Inc.

Advisory Board on Radiation and Worker Health, 

Subcommittee for Procedure Reviews 

February 15, 2022
2

Observation 1: TIB-5000 makes extensive use of 

an obsolete computer program, LOGNORM4

 LOGNORM4 was a freeware computer program:

– Developed before the issuance of TIB-5000 

– No longer publicly available

– A 16-bit computer code that cannot run on computers running Microsoft 

Windows 7 or later operating systems

 Options for NIOSH:

– Make a Windows 10-compatible version of the program available to the 

public, or

– Revise TIB-5000, substituting other calculational methods for LOGNORM4

 According to NIOSH: “This program is no longer used. Considering 

the ongoing CyberSecurity Modernization Initiative, developing a 

Windows 10 compatible version is not likely to occur.” 
3

Observation 2: There are more modern 

methods for treating censored data

 Censored data sets:

– Contain some results that are reported only as “greater than” or “less 

than” some value

– The only information retained is that a measurement was made and 

was part of a “high group” or a “low group”

 TIB-5000 prescribes a methodology for fitting lognormal 

distributions to data that contain “values [that] are reported as 

‘less-than’ some number or as zero.” This method has been 

called “regression on order statistics.”

 A function, ros, that implements such more modern methods 

can be found in the R package NADA.
4

Example of data reported in groups: Airborne 

uranium concentration measurements

Exposure

(mg/m3) 1948 1949 1950 1951 1952

0–0.1 9 13 38 33 55

0.1–0.5 13 14 62 55 48

0.5–2.5 44 31 — 30 22

>2.5 34 61 32 8 —

Source: “Exposure to Soluble Uranium Compounds,” reproduced from Eisenbud and Quigley 

(1956).
5

Observation 3: Inconsistent number of observations 

listed for U > 2.5 mg/m3 exposure group in 1949

 TIB-5000, section 2.1.4.1, states: “The first data point in 1949 

represents 13 of the 119 total observations; the second, 14; the 

third, 31, and the final point, 64.”

– Sum of listed observations = 122

 TIB-5000, table 2.4, lists the number of observations 

corresponding to each of the four data points in 1949 as 13, 

14, 31, and 61, respectively.

– Sum of the numbers of observations = 119

– 61 is most likely the correct number for the fourth data point
6

Description of mirror image method TIB-5000 

proposed to characterize zero or negative results

 According to TIB-5000, the mirror image method is a way to 

characterize zero or negative results, as follows:

– The analyst first deletes all data with values greater than zero (data 

with negative or zero values are unchanged). 

– For each negative or zero value, the analyst adds a new record equal 

to the absolute value of the negative or zero record. 

– The result is a symmetric distribution centered on zero, with the 

positive half being a mirror image of the negative half. 

– The analyst then computes the standard deviation of the new 

symmetric distribution and constructs a normal distribution with a mean 

of zero and the new standard deviation. 
7

TIB-5000 introduced the preserved mean and 

variance method 

 Characterize a normally-distributed measurement uncertainty and an underlying 

lognormally distributed measurand (true but unknown value of the specific 

quantity subject to measurement).

 “A more sophisticated alternative to the crude ‘mirror image’ technique” that is 

based on four assumptions:

1. “The observed probability density function (pdf) is the result of combining a normally- distributed measurement uncertainty with a lognormally-distributed measurand.” 

2. “The mean of the lognormal ‘true state of nature’ is equal to the mean of the 

observations.”

3. The mean of the uncertainty is zero. Therefore, the mean of the lognormal pdf is equal 

to the mean of the observations.

4. The variance of the sum, X + Y, is equal to the sum of the variance of X and the 

variance of Y, provided X and Y are uncorrelated. If there are enough data to estimate 

the variance of the uncertainty of the measurement procedure, say by repeated 

measurements of blank samples, then there remains only one parameter to be 

estimated: the variance of the lognormal dose distribution.
8

Observation 4: Mirror image and preserved mean 

and variance methods not supported by theory

 These two methods are not supported by any technical 

background in statistical theory of which SC&A is aware. 

 The examples given in TIB-5000 are just that: examples, not 

proofs.

 Conclusions are based on the specific data sets used in the 

analyses but are not necessarily applicable to other data sets.
9

TIB-5000 discussion of uncertainty in biokinetic 

models

 As reported by TIB-5000:

The National Council on Radiation Protection and Measurements 

(NCRP) used an expert group of internal dosimetrists to create a 

subjective quantification of the reliability of ICRP Publication 30 

biokinetic and dosimetric models . . . . While IMBA uses the newer 

ICRP Publication 66 respiratory tract model and newer biokinetic 

models, the results of these models may not be that much better than 

the ICRP 30 models for some radionuclides in cases where f1

[fractional absorption in the gastrointestinal tract] is the dominant 

uncertainty.
10

Observation 5: The NCRP assessment of 

ICRP 30 models does not apply to ICRP 66

 TIB-5000 lacks a sound basis for speculating that the ICRP 66 

respiratory tract and biokinetic models are not “that much better 

than the ICRP 30 models for some radionuclides in cases where f1 

is the dominant uncertainty,” and that the NCRP evaluation of the 

reliability of the ICRP 30 models is applicable to the ICRP 66 

models. 

 TIB-5000 cited an email communication from Bihl et al. to support 

the use of a lognormal distribution with GSD = 3 and claimed this “is 

reasonably consistent with the [NCRP] findings.” This email is not 

available; consequently, SC&A cannot determine if this document 

supports the use of a GSD of 3 for the uncertainty in internal dose.
11

Observation 6: GSD = 10 is excessive for a 

sitewide assessment of an individual worker 

 TIB-5000 stated that “the current default assumption when no information 

is available on uncertainty in aerosol measurements is that they are 

lognormally-distributed with a GSD of 5 for a single process or activity, 

and 10 for an entire site, plant, or factory.” 

 The assumption regarding the GSD for a single process is based on an 

analysis of 108 sets of aerosol concentration data or worker exposures 

tabulated by Christofano and Harris (1960), who listed measured and 

calculated data for a number of processes at seven uranium refining 

plants.

 SC&A disagrees with the inclusion of data from single processes that 

would be responsible for episodic exposures of one or more workers and 

do not represent the chronic exposures used in dose reconstructions. 
12

Determining a lognormal distribution from 

daily weighted average data 

 Christofano and Harris (1960) listed 33 instances of daily weighted average or simply “weighted 

average” concentrations that represent the chronic exposures of workers from a given process.

 In each case, the range of concentrations was listed, along with the average. 

 SC&A calculated σ = ln(GSD) by applying TIB-5000, Equation 10, reproduced here:

= arithmetic mean of x

xmin = minimum value of x

xmax = maximum value of x 

 In four cases, the quantity under the square root sign was negative, indicating that the data did not 

fit a lognormal distribution. 

 In 29 cases, 1.07 ≤ GSD ≤ 4.57. SC&A thus concurs that GSD = 5 is a plausible upper bound for 

the exposures of a single worker at a uranium refining plant. 
13

SC&A’s fit of a lognormal distribution to 136 

average aerosol concentrations 

 SC&A fitted a lognormal distribution to the average aerosol concentrations for 

the 136 processes tabulated by Christofano and Harris (1960). 

 GSD = 9.05. 

 The 136 data points represent a mixture of short-term measurements of 

individual processes and weighted averages of worker exposures at seven 

uranium refining plants. 

 These individual processes are included in the weighted averages.

 Inclusion of both types of data is redundant and biases the analysis by 

exaggerating the effect of highly variable short-term exposures.
14

Radon air sample data for “BZ removing 

covers” at Lake Ontario Ordinance Works

Date

Time Concentration

Start Stop At minutes (a) × 100 pCi/L

5/8 2:55p 2:56.5p 1.5 16.7

5/8 2:58p 3:02p 4.0 1.1

5/9 12:50p — <.5 2,370

5/9 12:51p — <.5 4.5

5/9 12:53p — <.5 450

5/9 12:55p — <.5 580

Source: Excerpted from Heatherton (1951, table II). 

(a) The meaning of “At” is unclear, but the data in the column are equal to the sampling duration.
15

TIB-5000 approach to evaluating radon 

exposure of tower workers

 According to TIB-5000:

The 6 individual results for “removing covers from drums” . . . are 

clearly not from the same population: 3 were in the range of 1.1 to 

17 [× 100 pCi/L] and 3 were in the range 450 to 2,370 [× 100 pCi/L]. 

Separating the two data triplets, plausible GSDs were found for each 

. . . by simply finding the average and standard deviations of the 

natural logs of each result. Allocating 12 minutes exposure time to 

each of the two lognormal distributions derived for “removing covers 

from drums,” . . . a mean TWA [time-weighted average] was 

computed from 10,000 Monte Carlo trials. 
16

Observation 7: Dividing a 24-minute operation into two 

12-minute operations is not claimant favorable

 SC&A does not agree with the TIB-5000 conclusion nor with its 

proposed solution. 

– The first two samples, with relatively low radon concentrations, were 

collected on May 8, 1951, in rapid succession. 

– The other four samples were collected the next day, also over a brief 

period. Three of them had high values—450–2,370 × 100 pCi/L—and 

one a much lower value—4.5 × 100 pCi/L. 

– Since the four samples were taken within the same brief time span, 

there is no basis for assigning them to two distinct populations.

 One simple approach to this problem is described on the next 

slide. 
17

SC&A’s alternate analysis of radon exposure 

of tower workers’ removing covers at LOOW 

 SC&A approach: Fit the six values to a lognormal distribution, weighted by each sample 

duration. 

 Results:

– Median = 5.65 × 100 pCi/L 

– GSD = 31

– 95th percentile = 1,612 × 100 pCi/L

– Square of the correlation coefficient r2 = 0.944 (indicates a good fit to a lognormal distribution)

– 95th percentile can be entered into IREP as a fixed value

 The preceding discussion presents an example of how the data for the drum cover 

removal can be used to assign radon exposures to workers performing this operation. 

Other solutions, using later methods than the one discussed here, are possible. 

However, SC&A believes that dividing this operation into two 12-minute periods is 

arbitrary and not claimant favorable.
18

Observation 8: Assessment of inadvertent ingestion 

for AWE site residual periods has been updated

 TIB-5000 stated that intakes by inadvertent ingestion for AWE sites are determined 

according to OCAS-TIB-009, rev. 0.

 That guidance is still used for assessing ingested intakes during the operational 

period at AWE sites. 

 For residual periods, the procedure of calculating intakes from inadvertent ingestion 

was addressed by the SCPR during meetings on November 1, 2012, and 

February 5, 2013. 

 It was agreed that NIOSH underestimated the ingestion rate during the residual 

periods at some sites by estimating it to be equal to 20% of the airborne activity from 

resuspension of the surficial contamination levels during the residual periods. 

 SCPR concurred with the NIOSH proposal that the ingestion rate at the start of the 

residual period be set equal to that at the end of the operational period and then 

reduced by annual depletion factors recommended in ORAUT-OTIB-0070, rev. 01. 
19

Observation 9: TIB-5000 refers to occupational 

medical dose guidance that has been revised

 Section 3.12, “Occupational Medical Doses,” states, “The default 

assumptions in OTIB-0006 [rev. 03] will be used if no other information is 

available.” The referenced document has been supplanted by ORAUTOTIB-0006, rev. 05, which constitutes a total rewrite of the earlier versions 

of this document. In particular, revision 05 states:

Because PFG [photofluorography] was primarily a mass screening 

technique most suitable to large populations, and therefore unlikely to 

have occurred on a mass scale at AWE sites, PFG should not be 

assumed to have occurred at AWE sites unless there is evidence to 

the contrary. 
20

Observation 10: Protocol for assigning missed 

doses is inconsistent with current guidance 

 TIB-5000 prescribed the procedures in OCAS-IG-001, rev. 1, and ORAUTOTIB-0020, rev. 01, for assigning external doses to normally monitored 

workers whose doses were not reported or recorded for one or more time 

periods. 

 Both documents have been revised since the release of TIB-5000, being 

replaced by OCAS-IG-001, rev. 3, and ORAUT-OTIB-0020, rev. 03, 

respectively. 

 The procedures in the revised documents should be followed for assigning 

missed dose. 

 Guidance to “substitute a value for each dosimeter reading . . . assign a 

triangular distribution with minimum = 0, mode = 0.5×LOD, and 

maximum = LOD” is no longer recommended.
21

Observation 11: Ingestion should be added to 

the pathways of environmental doses

 In Section 3.16, “Environmental Dose,” TIB-5000 listed five 

components of environmental dose but did not discuss these 

pathways. 

 The ingestion pathway was omitted altogether.
22

Equilibrium factors for radon isotopes

 If the concentrations of a radon isotope—Rn-220 (thoron) or Rn-222 

(radon)—in ambient air are known, but the actual concentrations of 

its short-lived progeny are unknown, the working level (a unit of 

potential alpha-energy concentration (PAEC), used to assess the 

effect of exposure to radon isotopes) can, in principle, be estimated 

by assigning equilibrium factors.

– An equilibrium factor is defined “as the ratio of the actual . . . PAEC . . . to the 

PAEC that would prevail if all the decay products in each series were in 

equilibrium with the parent radon or thoron, as the case may be” (United 

Nations, 2009).

 According to TIB-5000, lognormal distributions are assumed for 

equilibrium factors with mean values of 0.4 for radon and 0.02 for 

thoron. 
23

A bounding, site-specific thoron equilibrium factor 

should be derived as needed from available data

 UNSCEAR 2006 report to the General Assembly (United Nations, 2009) 

states:

More caution should be exercised in assuming the average values of the 

equilibrium factor for dose assessment from inhalation of thoron decay products. An 

objection to the use of thoron gas measurements for dosimetric purposes is that 

thoron may not be well mixed in the indoor air because of its short half-life. . . . Only 

where a room fan is used would thoron be well mixed and a large variation of the 

thoron concentration in the room not be found. . . .

Thus the use of an equilibrium factor for thoron should be limited to situations 

where large spatial variation is not found.

 More recently, Harley et al. (2010) derived an equilibrium factor “for both 

outdoor and indoor [thoron] environments (0.004±0.001 outdoors and 

0.04±0.01 indoors).” 
24

Observation 12: TIB-5000 assumes a 

questionable equilibrium factor for thoron

 Representing an equilibrium factor for thoron by a lognormal 

distribution with mean = 0.02 is questionable. 
25

TIB-5000 assumption about air sample 

distributions

 TIB-5000 assumed that, on average and in the absence of 

evidence to the contrary, an air sample distribution is unbiased. 

 Thus, the uncertainty distribution due to lack of 

representativeness must be unbiased, that is, have an 

arithmetic mean of 1.
26

Observation 13: Questionable uncertainty of 

representativeness of lognormal distribution

 In the opinion of SC&A, even if the true underlying distribution 

of concentrations were lognormal, there is no real reason to 

assume that the distribution of the uncertainty of the 

representativeness parameter is also lognormal. 
27

Questions?
28

References

Christofano, E., & Harris, W. B. (1960). The industrial hygiene of uranium refining. Archives 

of Environmental Health, 1(5), 438–460. https://doi.org/10.1080/00039896.1960.10662719

Eisenbud, M., & Quigley, J. A. (1956). Industrial hygiene of uranium processing. 

AMA.Arch.Ind.Health 14(1):12–22.

Harley, N., Chittaporn, P., Medora, R., & Merrill, R. (2010). Measurement of the indoor and 

outdoor 220Rn (thoron) equilibrium factor: Application to lung dose. Radiation Protection 

Dosimetry, 141(4), 357–362. https://doi.org/10.1093/rpd/ncq228

Heatherton, R. C. (1951, 18 May). Air radon survey at LOOW [Memorandum]. SRDB Ref. 

ID 008921, PDF pp. 10–13.

United Nations. (2009). Effects of ionizing radiation: United Nations Scientific Committee on 

the Effects of Atomic Radiation: UNSCEAR 2006 report to the General Assembly with 

scientific annexes: Vol. II, Annex E. Sources-to-effects assessment for radon in homes and 

workplaces. https://www.unscear.org/docs/publications/2006/UNSCEAR_2006_Annex-ECORR.pdf