MODARIA WG5: TOWARDS A PRACTICAL GUIDANCE FOR INCLUDING UNCERTAINTIES IN THE RESULTS OF DOSE ASSESSMENT OF ROUTINE RELEASES

Abstract

MODARIA (Modelling and Data for Radiological Impact Assessments) project was launched in 2012 with the aim
of improving the capabilities in radiation dose assessment by means of acquisition of improved data for model
testing, model testing and comparison, reaching consensus on modelling philosophies, approaches and parameter
values, development of improved methods and exchange of information. The project focuses on areas where
uncertainties remain in the predictive capability of environmental models, emphasizing in reducing associated
uncertainties or developing new approaches to strengthen the evaluation of the radiological impact.
Within MODARIA, four main areas were defined, one of them devoted to Uncertainty and Variability. In this area
four working groups were included, Working Group 5 dealing with the “uncertainty and variability analysis for
assessments of radiological impacts arising from routine discharges of radionuclides”. Whether doses are estimated
by using measurement data, by applying models, or through a combination of measurements and calculations, the
variability and uncertainty contribute to a distribution of possible values. The degree of variability and uncertainty
is represented by the shape and extent of that distribution.
The main objective of WG5 is to explore how to consider uncertainties and variabilities in the results of assessment
of doses in planned situations for controlling the impact of routine releases from radioactive and nuclear
installations to the environment. The final aim is to produce guidance for the calculation of uncertainties in these
exposure situations and for the presentation of such results to the different stakeholders.
To achieve that objective the main tasks identified were: to findtools and methods for uncertainty and variability
analysis applicable to dose assessments in routine radioactive discharges, to define scenarios where information on
uncertainty and variability of parameters is available for the testing of methodologies, to discuss the distributions of
parameters and data applicable, to carry out assessments in those scenarios performing an intercomparison of
different methods and to find how the results of this kind of calculations could be presented and interpreted by
decision makers. This work will present the advances achieved in the group.

Full text

www-ns.iaea.org/projects/modaria/
MODARIA WG5: TOWARDS A PRACTICAL GUIDANCE FOR INCLUDING UNCERTAINTIES IN THE RESULTS
OF DOSE ASSESSMENT OF ROUTINE RELEASES
Juan C. Mora1, Diego Tellería2, Ahmed Al Neaimi3, Anna Mª Blixt Buhr4, Iurii Bonchuk5, Sohan Chouhan6, Pavol Chylý7, Adriana R. Curti8, Dejanira da Costa9, Juraj Duran10, Dan Galeriu11, Ann-Christin Hägg12, Rudie Heling†13, Goran Ivanis14, Mikhail Iosjpe15, Pawel M. Krajewski16, Charlotte La ger12, Laura
Marang17, Christophe Mourlon18, Fabricio F. Perez19, Jige Shen14, Fabien Vermorel17, Andrew Woodruffe20, Benjamin Zorko21.
1CIEMAT, 2IAEA, 3ENEC - UAE, 4Vattenfall AB - Sweden, 5RPI - Ukraine, 6AECL - Canada, 7SE-VYZ - Slovakia, 8ARN - Argentina, 9IRD - Brasil, 10VÚJE Inc - Slovakia, 11IFIN-HH - Romania, 12SSM – Sweden, 13NRG - Netherlands, 14Ecometrix – Canada, 15NRPA – Norway, 16CLOR - Poland, 17EdF – France,18IRSN – France,
19SCK – Belgium, 20FANR - UAE and 21Jozef Stefan Institute-Slovenia.
INTRODUCTION
MATERIALS AND METHODS
RESULTS
CONCLUSIONS
MODARIA (Modelling and Data for Radiological Impact Assessments) is a four years project launched in 2012 by the International Atomic Energy Agency
(IAEA) with the aim of improving the capabilities in radiation dose assessment by means of acquisition of improved data for model testing, model testing and
comparison, reaching consensus on modelling philosophies, approaches and parameter values, development of improved methods and exchange of
information. Within MODARIA, four main areas were defined, one of them devoted to Uncertainty and Variability. In this area four working groups were
created, including Working Group 5 (WG5) which deals with the “uncertainty and variability analysis for assessments of radiological impacts arising from
routine discharges of radionuclides”.
Whether doses are estimated by using measurement data, by applying models, or through a combination of measurements and calculations, the variability
and uncertainty contribute to a distribution of possible values represented by the shape and extent of that distribution.
WG5 explores how uncertainties and variabilities should be considered in the results of assessment of doses in planned situations for controlling the impact
of routine releases from radioactive and nuclear installations to the environment.
Prospective Retrospective
Deterministic •Source term: fixed hypothetical
•Parameters: best estimates
•Habit data: Average value for the more
highly exposed group or95th percentile
for the major contributor (best estimate
the rest) from national or regional survey
•Dose coefficients: fixed
•Environmental concentrations: based on
measurements and/or estimations
•Source term: derived from measurements
•Parameters: measured and/or best estimates
•Habit data: Preferably local survey (focused in
the representative person). Fixed
•Dose coefficients: fixed
Probabilistic •Source term: fixed hypothetical
•Parameters: pdfs
•Habit data: fixed (not variability)
•Dose coefficients: fixed
•Environmental concentrations: based on
measurements and/or estimations
•Source term: derived from measurements
•Parameters: Preferably pdfs
•Habit data: Local survey (focused in the
representative person). Fixed
•Dose coefficients: fixed
To achieve the objective of this group several tasks were identified:
1. Tools and methods uncertainty and variability analysis applicable to dose assessments in
routine radioactive discharges,
2. Scenarios information on uncertainty and variability of parameters available for testing
methodologies,
3. Distributions of parameters and data applicable,
4. Sensitivity analysis necessity and methods,
5. Where and how correlation factors should be included,
6. How measured values < Ld should be considered,
7. Carry out assessments in defined scenarios and
8. Presentation and interpretation of such results.
Including uncertainties in the dose assessments: a structured and comprehensive
methodology has been drafted (the needs of each case is presented in the table).
Codes: specific codes already identified: CAP88, CROM, CSA-DRL code, ESTE, GENII,
IMPACT, SU_MMC and SYMBIOSE. Other codes, as Crystal Ball, were recognized to be
appropriate.
Testing scenarios: Two sets of data have been chosen: Real data from French NPP
(Chinon NPP in the figure) and Hypothetical data from EMRAS II project.
Other: Sources of uncertainties, sensitivity analysis, distributions of the parameters to
be used, correlation factors to be used, treatment of environmental monitoring data,
or the communication of the results including uncertainties are under discussion .
Acomprehensive review of the existing capabilities of including uncertainties in the
dose assessments of routine releases is being carried out, including the
communication of these results.
Guidance on the issue will be provided at the end of the MODARIA’s project for this
particular problem.
Additionally, some issues identified in the group as the different treatment of the
detection limits in prospective dose assessments or the degree of conservatism of
the models is being studied.
REFERENCES
•International Commission on Radiological Protection. The 2007 Recommendations of the International Commission on
Radiological Protection. ICRP Publication 103. 2007.
•International Commission on Radiological Protection. Assessing Dose of the Representative Person for the Purpose of
Radiation Protection of the Public and the Optimisation of Radiological Protection: Broadening the Process. ICRP publication
101. 2006.
•International Atomic Energy Agency. Handbook of parameter values for the prediction of radionuclide transfer in terrestrial
and freshwater environments. TRS 472. Vienna. 2010.
•Covalschi, Valentina - Risk communication The key of the policy success - S.N. Nuclearelectrica S.A., Bucharest, Romania.
2005.
ACKNOWLEDGEMENTS: We would like to thank the IAEA for the support
of the work performed in the Working Group 5, as well as to the Ciemat,
Slovenské elektrárne a.s., ABmerit and to the Almaraz NPP and Mochovce
NPP and the workersinvolved in the visits.