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Bill, You wrote: "See the "IATA Dangerous Goods Regulations - 2003 Edition," State Variation USG-10." - Could you please inform the page where you found your information? I can inform my IAEA reference: Radioactive material 1 - Material designated in national law or by a regulatory body as being subject to regulatory control because of its radioactivity; 2 - Any material containing radionuclides where both the activity concentration and the total activity in the consignment exceed the values specified in paras 401–406. (ST1) Because 2, countries who follow the IAEA ST1 should to consider that radioactive material requires that the material has both an activity concentration and total activity in the consignment which exceed the values listed in the A tables. This means you can have a material with an activity concentration greater than that listed, but less total activity in the consignment and are now considered non-radioactive.Because 1. If you have a shipment of Tc99, which under the ST1 has an activity concentration for exempt material of 10,000 Bq/g, you will still be regulated at 70 Bq/g (or 100 Bq/g) if your country has such figure to define radioactive material. Finally the reason for 2, were developed of transport-specific scenarios which reflected various exposure situations (exposure times, distances, source geometries, etc.). Based on these scenarios, both activity concentration and total activity values were calculated which would result in meeting the 10 microsievert per year value. These transport derived values were comparable to the exemption values in the BSS and resulted in recommended activity concentrations ranging from 1 to 106 Bq/g. Now as merely curiosity why the 70 Bq/g was selected? Jose Julio Rozental
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