Review of the A1 and A2 values: development, progress and outcomes

International audienceThe A1 and A2 values of the Q System described in the advisory material SSG-26 have been de-veloped to provide maximum allowable contents in packages not designed to withstand accidents, with the objective to limit the accidental exposure of persons below an effective dose of 50 mSv and a skin equivalent dose of 500 mSv. Current values were determined in 1996 according to spe-cific scenarios for five exposure pathways. Since then, the ICRP has published revised radiologi-cal data. In addition, progress in computer hardware and software allow the implementation of new methods of calculation, which are more complete and accurate. In September 2013, it was decided between NRA, PHE, GRS and IRSN to create an international working group to discuss the improvement of calculation methods described in the Q System. The first findings and results were presented during the PATRAM 2016 conference. The main items considered are the following:1.Using new data from the latest ICRP publications for emission spectra and external dose coef-ficients. 2.Using Monte-Carlo methods to take into account contributions from all radiations. 3.Selecting the irradiation field geometry.4.Selecting the calculation model for beta radiation and neutron emission from (α,n) reactions.5.Developing a specific irradiation scenario to the eye lens and the associated reference dose.6.Dealing with the progeny radionuclides. 7.Reviewing QC (inhalation) and QD (ingestion) values with the updated ICRP intake dose coeffi-cients that introduced new particle sizes and chemical forms.8.Reviewing QD (contamination) and QE (submersion) using Monte-Carlo methods.9.Considering the multi-path cumulative dose principle where simultaneous exposures may oc-cur. The review of items 1 to 4 has been completed; items 5 to 9 are in progress and discussion is pending on further work to be completed in the future.This paper will indicate the status of work that has been performed since 2016, explain the main changes in the calculation methods as well as the tools that have been developed to evaluate the Q values for any radionuclide, show results and describe the actions that are not yet completed. The WG expects the updated A values to be presented to the TRANSSC by 2021