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Technical issues related to the ERICA Tool (on Facilia website)

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Posted: 14/11/2011

Calculating Environmental Media Concentration Limits?

From:
Hildegarde Vandenhove
SCK•CEN
Belgium

Question:

Can you calculate Environmental Media Concentration Limits (EMCL) values as used in the ERICA Tool?

Answer:

You can estimate EMCL values using Tier 3 of the ERICA Tool. You need CR values with associated probability distribution functions (pdfs) for the radionuclide you are interested in (and kd values together with associated pdfs if considering an aquatic ecosystem). You need to make predictions for all reference organism assuming 1 Bq per unit media concentration; note for aquatic ecosystems you need to determine both a water and sediment EMCL separately. The EMCL is calculated from the highest 95th percentile dose rate predicted for any organism. To estimate the EMCL value divide your screening level dose rate (10 μGy/h default in the ERICA Tool).

The process of determining the EMCL using Tier 3 of the ERICA Tool is as follows:

• Suggest entering only 1 radionuclide at a time if including all the referernce organisms (otherwise there may too much data to 'run' the assessesment with sufficient simulations).
• Enter your mean concentration ratio (CR) and associated standard deviation (SD) values for each reference organism using the 'Edit distribution' tab chosing the appropriate distribution function (generally select 'lognormal' if n>1 and 'exponential' if n=1, leaving the 'lower' and 'upper cut off' as their default if you have no information).
• Check all Occupancy Factors are those which would result in maximual exposure for a particular reference organism.
• On the following screen enter a value of 1 into the media concentration cell. Note for aquatic ecosytems you will need to run water and sediment as separate assessments (when you estimate the water EMCL enter a value of 1 into the water activity concentration and leave the sediment blank; when estimating the sediment EMCL enter a value of 1 into the sediment activity concentration and leave the water blank).
• On the following screen select all the simulation parameters displayed and enter at least 1000 as the number of simulations.
• The statistics associated with the total dose rate are now available for each reference organism separately.
• From the 95th percentile total absorbed dose rate predictions identlfy the most exposed organism (i.e. select the highest 95th percentile)
• The 5th percentile EMCL is then be calculated by dividing the highest 95th percentile value by your screening dose rate.

The ERICA default EMCL values were calculated outside of the Tool using a Monte Carlo approach.

More infomation can be found in the ERICA Tool help file and Brown, J.E., Alfonso, B., Avila, R., Beresford, N.A., Copplestone, D., Pröhl, G., Ulanovsky A. 2008. The ERICA Tool. J. Environ. Radioact., 99, 1371-1383.

Answered by Cath Barnett14/11/2011

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Posted: 17/12/2010

How can you differentiate between dose from sediment and that from water?

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