3. Advantages of IMBA Modularity

= Flexibility

> Can use modules in any order to perform different functions -e.g., calculate
intakes, doses, or deposition of multi-modal aerosols, or perform parameter
sensitivity analyses.

= Can be Incorporated into Existing Software

>» BNFL (UK) have incorporated IMBA modules into their in-house dose
assessment software - to preserve operator familiarity with, and functionality
of, their in-house user interface.

>» As “Add-in” to counter analysis packages - such as ORTECTMs
Renaissance® software.

» As “Add-in” to aerosol size analysis packages - such as JABASoftTM’s
IMPACTOR EXPERT software.

= Each Module Can be Written Independently
= Easier to Develop “Front End” Interfaces
= Aids Quality Assurance

4. Quality Assurance

= Modularity
>» Each module is easier to test since it is small - with well defined input/output.
» Same modules are used for al calculations (e.g., for different radionuclides
and biokinetic models) - therefore code is smalier.
» Can readily test each stage of a calculation.
» Once a module works - it works.

= Used Previously QA’d Code Whenever Possible

« Each Module Developed Twice - by Independent
Authors, with Different Programming Languages

s Multi-Institutional Comparisons
» With ICRP tabulations, plus (CRP CD-ROM.
>» With other existing codes, e.g., LUDEP and PLEIADES (NRPB’s code used
to calculate ICRP’s published dose coefficients).
» Used in internal dosimetry and bioassay intercomparison exercises.



Co-development Process for IMBA-based Software Products

Customer/End-User ACJ & Associates, Ine. NRPB

i
~

23

Acknowledgements

Naomi Jarvis (NRPB) is the principal programmer of the IMBA@ interface codes.

M. S. Peace (BNFL) carried out a substantial part of IMBA development and quality
assurance;

M.-D. Dorrian, J. W. Marsh and S. L. Thrift (NRPB) assisted with the implementation of
Ddiokinetic models;

A. W. Phipps and T. J. Silk (NRPB) provided the ICRP SEE data and ran many
calculations with PLEIADES;

R.K. Bull (AEAT) assisted with quality assurance;
A. E. Riddell (Westlakes) assisted with many parts of the IMBA project in its early stages;

Members of the UK Internal Radiation Dosimetry Group provided the original inspiration
for the IMBA project, and support and encouragement as the project progressed;

Financial support (to NRPB) was provided by BNFL, AEA Technology, AWE and.
DERA, and;

DERA have kindly permitted NRPB to describe and demonstrate IMBA-CALC.


7. Time Scales and Progress (contd.) - IMBA Applications

—

Currently Proposed Developments

= PHARMA-CALC
» Application of IMBA modules to dose assessment for radiopharmaceuticals.
» Software would facilitate user entry of specific biokinetic models - for a very
large number of radiopharmaceuticais.
» Under consideration for development by NRPB - with funding from
radiopharmaceutical industry

= IMBA Applications Outside of UK

» IMBA EXPERT USDOE-Edition being considered by USDOE Headquarters,
Office of Worker Protection Programs and Hazards Management (EH-52), in
collaboration with principal USDOE Laboratories and Field Sites.

» IMBA EXPERT Canadian-Edition being considered by Canadian Nuclear
Safety Commission (CNSC), in collaboration with potential user groups, ©.9.,
Ontario Power Generation,

» Interest in NRPB-developed application software in Nordic countries, and in
other parts of Europe.

8. Conclusions

« “IMBA“ has proved to be the way forward for internal
dosimetry in the UK - by facilitating a smooth transition to
implementing new ICRP models for dose assessment within the
framework of new Tonising Radiation Regulations.

= IMBA modules have been extensively QA'd - and the
methodology has been shown to work.

= Ongoing developments and enhancement of the IMBA modules
are currently funded in the UK, and are underway.

« Such fundamental developments and enhancements are likely to
receive continued support in the UK, and are likely to keep pace
with future developments of ICRP models and recommendations.

« The proposed development of an MBA EXPERT USDOE-Edition
tailored to meet the current and future technical requirements
of participating USDOE sites is timely - and has been welcomed
by the USDOE “community.”



Overview III - 1970/80s Evolution of Internal
Dosimetry and Regulation (contd.)

> Adult (male) worker.
> Dose coefficient - committed equivalent dose in organ T resulting from intake I:

Hy(t)= [PH y(t) dt ees (4)

H,(t)=Ih,(t) +25)

Ip = x dus, j SEE(T 38), sevesne (6)

SEE(T < S;t)= Me ZF ¥, wy AF(T <—S,E,, t), = (7)

Overview IV - 1970/80s Evolution of Internal
Dosimetry and Regulation (contd.)

ication 30 - “Limits for Intakes of Radionu

> Annual Limit on Intake (ALI) defined as largest value of J which satisfies:

Tw; Hoy $0.05 Sv .........(8) for stochastic effects
Tr

T Hz S05 SV ...144..(9)  fornonstochastic effects

» Derived Air Concentration (DAC) in Bq m” for any radionuclide is that
concentration in air which, if breathed by the Reference Man for a working year
under conditions of light activity, would result in the intake of one ALI:

eesseeeee (10)
eh fete, ft

ALI ALI

DAC = <> =
2000 X12m>h' —2400m*


5. Organisation of Effort (Phase I)
Independent Authorship of IMBA Modules

NRPB BNFL  Westlakes

Module Research
Institute
Deposition Vv Vv
Biokinetics v Vv
Fitting Vv Vv
Disintegrations Vv Vv
Dosimetry Vv Vv

5. Organisation of Effort (Phases 1 & Ill)

= Phase Il

» Completed April, 1999.
» Major technical contributions from NRPB, BNFL, AEAT, and AWE.
» Each organisation also contributed substantial funding.

= Phase Ill

» In progress, 2000 - 2001.

» Continuing developments and improvements of IMBA modules, e.g., the
bioassay data fitting module.

» Continuing development, implementation, and quality assurance of model
and radiation data files.



6. Methods of Application (contd.) - NRPB Developed
User-Friendly Software Package

jired a Simplified User Interface

For High Throughput, Regulatory Purposes, DERA Rt

7. Time Scales and Progress

IMBA Modules (Phases 1, 2 & 3) and MBA Applications

ao) Sawating TSaions
wool { worn 5 i ALARA 200
1998 1999 2000 i
phase 1
& p Munich Ontario
phase 2 yr
NSC
IMBA-CALC PHARMA-CALC

URANIUM version?
IMBA EXPERT (DOE ver)?



2. Description of IMBA Suite (contd.)
Deposition Module

IN IMBA_DEP | . OUT
AMAD “as D(ET,)
AMTD Deposition D(ET,)

Gy D(BB,) D(BB,)
Shape factor D(bb,) D(BB,)
Density D(Al)
Exposure Type

Subject

2. Description of IMBA Suite (contd.)
Bioassay Module

IN IMBA BIO OUT

Deposition (7) Bias =p

Solubility (5) ‘ng it Bioassay
Bioassay Type poe Quantity
Ret/Exc Function At each t,
Intake Regime (T,, T,)

Radioactive Decay,

f, tywroogy X, © (data)



Planned Capabilities of IMBA Expert USDOE-Edition

Phase I

= The software will deal with the following routes of intake:
>» Inhalation (Acute, Chronic);
> Ingestion;
> Injection (i.v.);
> Trans-dermal (Wound).

= The software output will include:
>» Equivalent doses to each organ;
Committed effective dose;
Organ retention at specified times;
Bioassay quantities over specified timescale;
Best estimate of intake.

v

vv

15

Planned Capabilities of IMBA Expert USDOE-Edition

Phase I

= The parameter fitting method will be based on the maximum
likelihood method, and the software will therefore be able to deal
with:
> More than one data point simultaneously;
» Data recorded as below a minimum level of detection;
> Positive data points with different errors on each measurement;
>» More than one intake regime simultaneously.

= Other features will include:
> Built-in database of all ICRP default parameters;
> Built-in database of all bioassay retention functions;
> Ability to enter user-specified retention functions;
» Ability to enter user-specified particle transport parameters;
> Built-in biokinetic models for each radionuclide considered.

eit


Overview VII - 1990s Evolution of Internal Dosimetry
and Regulation (contd.)

Radiological Protection”

» More realistic (mechanistic) than ICRP30 model for deposition, clearance and
dosimetry (target cells at risk).

» Designed for both dose limitation and dose assessment.

> Aerosol size range 0.0006- pm-AMTD through 100- ym-AMAD - including
“{nhalability.”

» Mechanistic treatment of particle clearance - competition between “mechanical”
clearance processes and material “dissolution/absorption” fo blood.

» fue “solubility classifications” (D, W and Y) replaced by “absorption types”

, Mand S).

> Ability to represent absorption behavior of specific materials,

» New dosimetry of alveolar-interstitial (AD), bronchiolar (bb), bronchial (BB),
thoracic lymph nodes (LNTH), and extrathoracic tissues (ET ,, ET2, and LNET).

» Extrathoracic tissues recognized as potentially “at risk.”

> Lung tissue weighting factor (W jung = 0.12) sub-divided into fractions: 0.333 for
Al; 0.333 for bb; 0.333 for BB, and 0.001 for LNTH.

9

Overview VIII - 1990s Evolution of Internal
Dosimetry and Regulation (contd.)

= 1995 - ICRP Publication 70 - “Basic Anatomical and
Physiological Data for Use in Radiological Protection: The
Skeleton.”

= 1994 - ICRP Publication 68 - “Dose Coefficients for Intakes of
Radionuclides by Workers.”

" 1997 -ICRP Publication 78 - “Individual Monitoring for Internal
Exposure of Workers: Replacement of ICRP Publication 54
(1988).”

= 1999 - EPA issued Federal Guidance Report #13 adopting ICRP
Publication 60 risk factors and current ICRP respiratory tract and
biokinetic models. it



Overview V - 1970/80s Evolution of Internal
Dosimetry and Regulation (contd.)

a -It lication - “Limit
Radionuclides by Workers”- Metabolic Models

> Simple, linear first-order equations describe translocation of material (from
Tespiratory tract and body organ “compartments”).

> Contents of compartments mix in instantaneous, uniform manner.

> Organ deposition from transfer compartment (blood) oceurs rapidly.
> Removal from each organ governed by specific retention times.

» Direct excretion occurs from the organs and tissues after deposition.

» Metabolic properties of a nuclide are described by a set of rate constants that are
fixed for the 50-year integration period.

» Daughter atoms bom in the body following deposition of the parent are metabolized
with the properties of the parent.

> Limitation of Models - All ICRP30 models designed for dose limitation - not for
individual dose assessment (bioassay). ‘el

Overview VI - 1990s Evolution of Internal
Dosimetry and Regulation

> Revised overall radiation risk estimates - added consideration of “radiation
detriment.”

> Revised tissue weighting factors, w; - including more organs and “accounting” rules
for “remainder tissues” and “rest of body.”

> Lowered dose limits,

"1 = re ic “Biokinetic” Mc
> ICRP Publication 67 (1993) - including transuranics,

» ICRP Publication 69 (1995) - including uranium,


2. Description of IMBA Suite (contd.)

Summary of Key Functions

« Estimates intakes from bioassay data - and predicts committed doses.

- By running modules in specific order, it is possible to perform many different
types of calculation.

~ Modules are run from user-friendly “interface” which can be customised to
user's specific requirements.

« Ability can be incorporated in design of interface for user fo vary
environmental and other parameters of models.

« IMBA system is designed to analyse simultaneously muttiple intake
regimes - which can include different acute and chronic intakes, by
different pathways (e.g., inhalation, ingestion, or direct uptake to blood).

« All types of bioassay data can be analysed, e.g., whole body or organ
counts, urinary or faecal excretion - and IMBA incorporates sophisticated
fitting methods, ¢.g., unbiassed treatment of observations < MDA,
varying MDAs, and different error types for individual data points.

2. Description of IMBA Suite (contd.)

Radionuclides

= Phase | Development (completed)
. 238py 131) 234yy B7C5, 3H

= Phase I| Development (completed)

. Bg gy, C9, 108Ru, 241 am, 27 Ao,
241 by 238py, M4Ce, 21055

= Phase II! Development (in progress)

- Various



Deliverables Schedule for IMBA Expert USDOE-
Edition

—

= Phase I - “alpha version” Sep, 2001
® Phase I - “beta version” Dec, 2001
= Phase I - final version with documentation § Mar, 2002

= Phase II - “alpha version” Jul, 2002
= Phase II - “beta version” Sep, 2002
® Phase II - final version with documentation Dec, 2002

Spiel Nit

13

Aims of IMBA Expert USDOE-Edition Project

Provide USDOE Sites With Standardized Methods for
Dealing With Bioassay Measurements - More Powerful And
Flexible Than Existing Software

= Develop user-friendly, quality-assured software to
enable USDOE sites to use IMBA modules
automatically for intake and dose assessment.

= Extend the use and applicability of the IMBA modules.

= Customize use of IMBA modules for specific USDOE-
site regulatory purposes. a

“4


NIOSH OCAS Meeting Report
Presentation and Discussion with ACJ & Associates
on
The Integrated Modules for Bioassay Analysis Software (IMBA)

Date/Location of Meeting: May 8", 2001 / Hamilton conference room A

Attendees (Affiliation):
Larry Elliott, Ted Katz, Greg Lotz, Jim Neton, Mary Schubauer-Berigan, Randy Smith, Henry
Spitz (NIOSH)

Alan Birchall and Tony James (ACJ & Associates)

Objective: To learn about the capabilities and status of ACJ & Associates IMBA software for
performing intake and internal dose assessments using the revised ICRP lung and biokinetic
models.

Meeting summary: After a brief introduction of OCAS staff by Larry Elliott, Tony James
provided an historical overview of internal dosimetry models / techniques and computer based
analysis software. This was followed with a presentation by Alan Birchall who described the
history of IMBA development. After this a brief computer demonstration of the software
package was held, which was followed by a general discussion on how IMBA could be modified
to meet OCAS’ specific needs under EEOICPA. A copy of the overheads used for these
presentations is attached.

It was concluded that IMBA had the desired capabilities, but some modification would be
required to meet to meet our needs. Jim Neton agreed to develop a list of those features that
would be absolutely essential for OCAS to use the IMBA program. ACJ & Associates would
then respond with an estimate of the time and funding requirements necessary to implement these
changes.

Page 1 of 1


Planned Capabilities of IMBA Expert USDOE-Edition

Phase IL

= Other additional features:

> Ability for user to over-ride program’s best estimate;

» Download graphical output to spreadsheets;

> Evaluate uncertainty on the estimate of intake;

> Estimate intakes of “'Pu from measured “Am;

> Ability to use tissue weighting factors from 10 CFR 835;

» Ability to extrapolate fitted bioassay function to enable
user to design future monitoring program;

> Inclusion of Jones and Durbin excretion models for
plutonium;

> Ability to deal with chelated intakes.

Planned Capabilities of IMBA Expert USDOE-Edition

Radionuclides Required by Contributing USDOE Sites

idea is a
z= cI
r3
Can me?
rane 2 viet
ca a Sire
Sy te epee
7 -
am z
oe
Zz ry Ca
*
rca
7

dtd felebol obo -f af

sist fs} | | Heisistel

fs i

RTT I TH
Isictsis} i

iI is

is] Is

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SISISISE INiRisiieieiniciss

20


Planned Capabilities of IMBA Expert USDOE-Edition

Phase I

TM Other features (continued):

» On-screen graphical and statistical output;

> Ability to download data to spreadsheets;

> Ability to deal simultaneously with doses ftom combinations of
tadionuclides;

» Ability to use both ICRP 26 and ICRP 60 weighting factors;

» Built-in nuclear decay database, and ability to display it on-screen;

» Ability to exclude individual data points;

> Ability to deal with large data sets (hundreds of points);

» Ability to change error assumptions (normal or lognormal);

> Ability to change all aerosol parameters ( ¢.g., including particle density,
shape factor;

> Recommend one single best estimate;

» Ability for user to enter specific absorption parameters;

> Ability to toggle units between pCi and Bg;

» Ability to dump output as ASCII file;

> Ability to toggle between date and days. pepe Sit

Planned Capabilities of IMBA Expert USDOE-Edition

Phase IT

= This will enhance the power of the Phase I software significantly,

while retaining its flexibilty and ease of use. The main

enhancements will be:

> Extension of the fitting routine to enable the user to fit more
than one data set simultaneously, e.g., the ability to determine -
the best estimate of an intake from both lung counts and urine
samples;

>» Extension of the fitting routine to enable the user to take into
account previous measurement history of other individuals
(group members) using a Bayesian approach;

> Ability to deal with bioasssay data taken over different periods
of time;

> Inclusion of an IMBA module dealing with tritium;

» Resolution of any user problems with, and suggested

enhancements to, the Phase I software; rma
» Extension to additional radionuclides. Aided



Use of ICRP’s New Respiratory Tract Dosimetry and
Biokinetic Modelling Concepts in Radiation Litigation

Dr. James has applied ICRP’s current modelling concepts
for expert dose assessments in 11 litigated cases (to date)

=In UK - Since 1989 in Rae and Hope vs. BNFL
(English High Court).

=In US - Since 1993 in Billingsley vs. Dow
Chemical et al. (Colorado Industrial
Compensation Court).

i

Current Status of ACJ & Associates, Inc./NRPB
Co-development Projects for [MBA-based Bioassay
Application Software

= Defence Evaluation Research Agency (DERA), UK -
IMBA-URAN project commenced.

«DOE, EH-52 (US) - awaiting contract for IMBA
Expert USDOE-Edition project (Phase I).

= Canadian Nuclear Safety Commission (CNSC) -
negotiating contract for IMBA-CANDU.

= IMBA Expert Uranium-Edition - mining and nuclear
industry clients “in waiting.”


6. Methods of Applying IMBA Modules
(For Contributing Organisations in the UK)

= Distribution of IMBA Modules Themselves

» British Nuclear Fuels Limited (BNFL), Atomic Weapons Establishment
(AWE), and Atomic Energy Authority Technology (AEAT) have incorporated
IMBA modules into their own “in-house” software for bioassay analysis,
intemal dose assessment and reporting.

= NRPB Development of User-Friendly Software for
Automatically implementing the IMBA Modules

> This method of applying the IMBA modules and methodologies was
preferred by the Defence Evaluation Research Agency (DERA) - and other
UK Approved Dosimetry Services (ADS).

6. Methods of Application (contd.) - “In-House”
Incorporation of Modules

Required Functional Structure

IMBA suite

Integrated Modules for Bioassay Analysis.



Overview I - Early Evolution of the Quantitative
Regulation of Internal Dose

» Introduced concept of calculating dose to individual body organ from radionuclide activity
uniformly distributed within that organ.

> Used “effective radius” of organ to calculate absorbed dose for ‘y-emitters.

» Used simple compartmental clearance rate-constants to calculate retention and number of
disintegrations in body organ.

» Recommended values of “permissible” doses accumulated over specified time periods for
several “critical” body organs, e.g., D = 5x(N-18) rem for blood forming organs, gonads,
and lens of the eye.

» Recommended values of “maximum permissible concentration” in air (MPC,) and water
(MPC,,) for list of “important” radionuclides - corresponding to accumulation of the
specified “permissible” dose in most highly irradiated organ.

» Recommended “maximum permissible body burden” for each radionuclide -corresponding
to accumulation of respective “maximum permissible [organ] dose.”

» Simple “by-hand” calculations. tent

Overview II - 1970/80's Evolution of Internal

Dosimetry and Regulation
C uk . bli ati r iP ion” . i

» Established dose limitation system designed to prevent “non-stochastic” effects and to
limit “stochastic” effects.

> Non-stochastic limits based on the 50-year organ doses (Hep).

Fast [in gray (Gy), or rad}.........()

H, = Yi, Dr, [insievert(Sv),orrem| 2... (2)
R

D,=

» Stochastic limits depend on fotal effects of organ doses on whole body.

E=)\w, H, [insievert(Sv),or rem]... Q)
T


IMBA: Concepts & Capabilities

by
Dr A Birchall and Dr A C James

Meeting with the Internal Dosimetry Working Group,
Canadian Nuclear Safety Commission (CNSC)
CNSC Headquarters
280 Slater Street
Ottawa, Ontario

October 3%, 2000

NRPB

IMBA: Concepts & Capabilities

Contents

Introduction

Description of IMBA Suite
Advantages of Modularity

Quality Assurance

Organisation of Effort

Methods of Applying IMBA Modules
Time Scales and Progress
Conclusions

PNOARONS=



1. Introduction (contd.)

Introduction of the “IMBA” Methodology in
the UK Has Eased the Practical Transition
From Old to New ICRP Models - and to
Implementation of New Ionising Radiation

———r y y y
1995 199619971998 1999-2000

Admiration for (CRP

2. Description of Modular IMBA Suite

The IMBA Suite Consists of Six Independent Code Modules Which
Communicate via ASCII Data Files -and Can be Run in Any Order

IMBA_DEP ; IMBA_BIO > IMBA_FIT

‘| deposition biokinetics fitfing | -
IMBA_EFF IMBA DOs f IMBA_DIS :

eff dose 4 Foigon dose disints



IMBA: The UK’s Integrated Modules for Bioassay
Analysis - Development Strategies for “Expert”
Software Applications

Presentation to HHS/CDC/NIOSH Office of Compensation Analysis
and Services (OCAS) Staff on Software Needs for Implementing
US. Legislation Related to DOE Worker Compensation

May 8, 2001

Anthony C. James, Ph.D.
ACI & Associates, Inc.
129 Patton Street
Richland, WA 99352-1618, USA

And
Alan Birchall, Ph.D. 1
Ni PB National Radiological Protection Board
Chilton, Didcot, OXON OX11 ORQ, UK Ge, g

aD,

Scope of Presentation and Meeting - OCAS,
May 8, 2001

» James - Overview of the evolution of ICRP internal dosimetry and
dose assessment methodologies.

> Birchall - Development of NRPB’s “Integrated Modules for
. Bioassay Analysis” (IMBA).

> Birchall - Demonstration of IMBA methodology and capabilities.

> James - Strategy for developing “IMBA Expert” software
applications tailored to users’ specific requirements.

>» James - IMBA Expert USDOE-Edition - content and timescale.
> Meeting - Discussion on how IMBA methodology could best be

applied to meet the regulatory needs of OCAS/DOE
Worker Compensation. im


Agenda
ACJ & Associates Internal Dosimetry Meeting ~
Conference Room B
May 8"
9:00 A.M.

9:00 Introductions and brief discussion of EEOICPA and NIOSH’s role (OCAS Staff)

9:20 Overview of internal dosimetry techniques and computer based

analysis software (ACJ)
9:50 Interactive demonstration of Integrated Modules for Bioassay

Analysis (ACJ)
10:50 Discussion of IMBA/DOE (ACY)
11:20 Discussion of NIOSH’s specific needs under EEOICPA (ALL)
12:00 Lunch

1:00 Review of specific exposure scenarios and potential
IMBA modifications ° (OCAS tech.team)

2:45 Adjourn


Development Plan for IMBA-based Software
Products - Canada and the United States

The NRPB has appointed ACJ & Associates, Inc. to serve as
"AUTHORISED NRPB SOFTWARE CO-DEVELOPER AND
DISTRIBUTOR" for North & South America and the Pacific Rim
Countries

® AC] & Associates, Inc. will co-develop and license to “end-users”
software products utilizing NRPB’s proprietary IMBA ° modules
and methodology for application to bioassay analysis and dose
assessment.

21

Summary of the Roles of ACJ & Associates, Inc. and NRPB in
Co-developing IMBA-based Software Products

Territory of North & South America and Pacific Rim Countries
ACJ & Associates, Inc, :
© Marketing and identification of customer requirements.
® Liaison with customer to develop detailed technical specification of
software function and user-interfaces, and documentation requirements.
Liaison with NRPB to cost any necessary coding development, and
provision of quotation for cost and delivery to customer.

© Documentation and testing of software product against technical
specification, delivery of software and user-license(s) to customer.

® Provide customer with appropriate technical support.
NRPB:

© Develop and quality assure any necessay new software coding to interface
with IMBA® modules.
" Provide scientific oversight of new methodologies or applications.

= Maintain close links with ICRP Dose Calculations Task Group (DOCAL) and
developments in ICRP Committees and other Task Groups.

22


a —

1. Introduction to IMBA Project

"When? - started in 1997.

=Why? - ICRP has revised many of its biokinetic models, including that for the

respiratory tract.

- Use of new models required by UK regulations (January, 2000).

- Although corresponding dose coefficients are published by ICRP,
UK Approved Dosimetry Services need to implement new models to
interpret monitoring data, and calculate doses under non-standard
conditions.

~ Appropriate user-friendly software not currently available.

= What? - IMBA modular system (integrated Modules for Bioassay Analysis)
was developed jointly by NRPB and the UK Nuclear Industry to
provide well QA’d code modules and methodologies to implement
new ICRP models for estimation of intakes and doses.

1. Introduction (contd.)

Publication Sequence
of New ICRP Models,
Recommended Dose
Coefficients, and
Practical Guidance on
Bioassay Led to
Confusion

Confusion with ICRP

t T T T T
1995 1996 1997 1998 1999-2000