MODARIA II WG4: Working Group 4 Transfer processes and data for - PowerPoint PPT Presentation

MODARIA II WG4: Working Group 4 – Transfer processes and data for radiological impact assessment

WG4 report status • First full draft available for the meeting – Prioritising data gaps – Kd – soils, freshwater (marine) – Transfer to animal products – Transfer to wild game in Japan • Discuss key messages of each section • Critically evaluate text

Assessing the radiological impact from radioactivity in the environment We need to adequately quantify the key transfer processes and recognise their limitations in radiological assessments • improve understanding of key processes • explore limitations of the models and uncertainty in model results. The transfer processes and related data will vary depending on the situation considered; • planned, existing and emergency exposure situations • characteristics of the environment (terrestrial, freshwater, marine)

Extended remit • MODARIA WG4 focus was on temperate climates and conditions in developed countries. • Important to consider what differences there are in the assessment methodology when considering tropical, semi ‐ tropical or arid environments.

WG4: Objectives • To identify key transfer processes for radioactivity in the environment, in the context of the situation under consideration, for use in radiological impact assessment and to provide analysis of key relevant data. • To consider the impact of the accidental release from the Fukushima Dai ‐ ichi site in Japan in 2011 and the applicability of existing models and data to the Japanese situation. • To provide advice on the applicability of assessment models to tropical, semi ‐ tropical and arid environments.

Relevance to regulatory goals of IAEA Human and environmental radiological protection in situations of regular operational activities and in accidental scenarios. W G4 is working toward: • Strengthening evaluation of the radiological impact by improving the data underpinning the models developed for assessing the transfer of RNs in the environment and therefore the radiological impact • To more appropriately assess exposure levels of the public and in the environment to ensure an appropriate level of protection from the effects of ionizing radiation, associated with radionuclide releases and from existing radionuclides in the environment

Development of a (smart) database for sorption distribution coefficients, K d (from MODARIA to MODARIA II) MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

K d variability It is obvious that:  for a given radionuclide, there is not a single K d value  values may vary within 5 ‐ 6 orders of magnitude range for a specific radionuclide! MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

K d variability Characteristics of the solid and liquid phases Methodological approach (factors governing sorption mechanisms and radionuclide speciation) (e.g., sorption; desorption; in situ) (e.g., pH; Eh; texture; organic matter content; water column/soil solution composition; particle size) K d variability  The relative weight of each variability source is radionuclide ‐ dependent! MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

Refining K d best estimates derived from datasets Sensitivity analyses show that K d values are one of the most important source of uncertainty in some risk calculations:  Need to refine K d best estimates to derive them on the basis of site ‐ specific information based on mechanisms and factors governing radionuclide interaction  Need to describe K d variability of a dataset (use of density functions, PDF/CDF) From a simple dataset to a smart database MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

Starting point: datasets for soils and freshwater systems IAEA EMRAS Programme (Environmental Modelling for Radiation Safety; 2003 ‐ 2007): WG1 ‐ Revision of “Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments, TRS 364”. TRS 472 Dataset Description Best estimates: PDF/CDF Factors to group K d to derive Responsible GM (GSD; (Min ‐ derived best estimates based on site ‐ Max) specific information Soil 2900 records ‐ Yes No Texture + organic matter; pH; Vidal et al. (UB; 67 elements soil solution cationic SCK ‐ CEN) composition; radiocaesium interception potential; etc. Freshwater 2900 records – Yes Yes Methodology; suspended Ciffroy et al. 15 elements matter concentration; contact (EDF; CEREGE) (single values for time; pH; solid ‐ to ‐ liquid ratio; additional 10 E h elements) MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

Update of datasets: MODARIA programme  IAEA MODARIA Programme (Modelling and Data for Radiological Impact Assessments; 2012 ‐ 2015): WG 4 ‐ Analysis of radioecological data in IAEA Technical Reports Series publications to identify key radionuclides and associated parameter values for human and wildlife assessment (led by B. Howard, CEH). TECDOC in progress.  Creation of critically reviewed K d datasets of soil and aquatic systems:  Soil dataset (responsible: Vidal et al., UB)  Freshwater dataset (responsible: Boyer et al., IRSN) MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

Main outputs from MODARIA programme  Agreed criteria to accept / reject data (environmental solid matrices; experimental approaches related to short/long term assessments; requirements for data from stable isotopes; treatment of replicates; etc.).  > 12,000 K d entries for more than 80 elements: • Soil dataset : > 5000 entries for > 80 elements (plus > 2000 entries for 75 elements from other geological materials, such as subsoils, till and gyttja). • Freshwater dataset : > 5000 entries for > 40 elements MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

Main outputs from MODARIA programme  Developed examples to show how to derive K d best estimates (and density functions) for a given radionuclide from data grouped according to the values of key properties governing radionuclide interaction: • For a few radionuclides, K d could be predicted from linear multivariate correlations based on key properties • Various K d best estimates for a given radionuclide depending on the available quantitative information on key properties • PDF/CDF possible for datasets with enough entries • Percentile ranges remove extraordinarily low or high K d values to decrease variability (if required)  Developed path forward to filling data gaps (e.g., chemical and environmental solid matrix analogues). MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

MODARIA programme: key messages  Work in progress .  Datasets updates have benefited from inputs by member states .  Only “informed” K d are now accepted (excepting when no data is available).  Significant improvement possible in best estimates K d values: site ‐ specific data improve assessments!  K d will be reported for each element : not overall summary in big tables for all elements anymore MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

K d smart database: so what is it?  It should include practical guidance to address variability and limitations of K d approach  The end ‐ user may obtain a K d best estimate (and associated variability description) from the database by introducing as much site ‐ specific information as possible, especially dealing with factors governing radionuclide interaction: • Environmental scenario (terrestrial? freshwater? marine?) • Type of solid matrix (soil?; deposited sediment?; suspended sediment?) • Short ‐ term assessment? Long ‐ term assessment? (sorption, desorption or in situ ‐ field data?) • Properties: pH? organic matter content? particle size? contact solution composition?  The smart database would calculate the related K d best estimate and variability (e.g., in terms of CDF and percentile ranges) MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

MODARIA II: Future challenges to create the smart database  Welcome other participants and datasets  Continue efforts to identifying key factors to group K d data for other radionuclides (on the basis of easy ‐ to ‐ obtain information!).  Fill data gaps for prioritized radionuclides and scenarios, and develop procedures and make recommendations for missing data.  Include marine K d data (IAEA’s MARiS) and complete critical review of marine datasets.  Select the appropriate software for the smart database , and move towards a common structure for soil/freshwater/marine systems and export soil/freshwater/marine datasets into the agreed database common structure. MODARIA II Programme . First technical meeting. IAEA Headquarters, Vienna Oct ‐ Nov 2016

WG4 sub ‐ group Collation of environmental transfer parameters after the Fukushima accident (Fukushima parameters) Open data sources (Radiation monitoring data, food monitoring data, institute reports) and papers published in journals (peer review) will be used to provide parameters after the Fukushima accident