Findings and future work of the International Working Group on review of A1 and A2 values

The A1 and A2 values described in the advisory material SSG-26 have been developed to provide the maximum allowable contents in packages not designed to survive accidents, with the objective of limiting the exposure of individuals to an effective dose of less than 50 mSv and a skin dose equivalent of less than 500 mSv.Current A1 and A2 values were determined in 1996. Since then, the ICRP has published revised radiological data. In addition, progress in computer hardware and software allows the implementation of new methods of calculation, which are more complete and more precise.In September 2013, NRA, PHE, GRS and IRSN agreed to exchange findings and proposals about methods of calculation of A1 and A2 and to create an international working group. The review of following issues 1 and 2 had been completed when the abstract was submitted; discussion of issues 3 to 8 is pending on further work to be completed in the future.1. Use of new data in new ICRP publications (ICRP 107, ICRP 116) for radionuclide emission spectra and dose coefficients.2. Use of calculation models based on Monte-Carlo (MC) methods (probabilistic approach for a sampling of particle histories) in order to take into account the new radiations not explicitly considered in the current Q system (beta particles of more than 400 keV, or spontaneous fission neutrons).3. Selection of the irradiation field geometry.4. Selection of the calculation model for beta radiation.5. Selection of the method of calculation of progeny radionuclides.6. Development of a specific irradiation scenario for the lens of the eyes and the associated dose objective.7. Reviewing QC (inhalation) and QD (contamination) values: firstly to take into account new ICRP inhalation dose coefficients that are presently in the process of publication; secondly to check the possible significant influence on QD from ingestion. Tritium scenarios should also be reviewed.8. Finally, methods to aggregate the different contributions to effective dose or to skin equivalent dose are to be confirmed, as well as the multi-path cumulative dose principle where simultaneous exposures may occur, for instance by direct external irradiation and internal contamination (inhalation, ingestion) in the evaluation of Q eff or by direct external irradiation and contamination in the evaluation of Q skin.This paper will indicate the status of work that has been performed, explain the main changes in the calculation methods, show the preliminary results and describe the actions that are not yet completed.