Transport Index (TI)
Published: Oct 22, 2023
The transport index (TI) is a special number applied to the labels of Type A and Type B radioactive packages for transport (as specified by the ADR legislation and IAEA - "Regulations for the Safe Transport of Radioactive Material", 2018, SSR-6). The formal way of determining the TI is to measure the dose rate at 1m from the package, (from all sides that are reasonably accessible to obtain the highest value), in mSv/h. This value is then multiplied by 100 and rounded up to the first decimal place. Example: The maximum dose rate at 1m from a package is found to be 0.0127 mSv/h. This is multiplied by 100 to give 1.27, and this is then rounded up to give a TI of 1.3.
An alternative method is to measure the dose rate in micro Sv/h and then divide this value by 10 and then round up as before. Example. The maximum dose rate at 1m from a package is found to be 12.7 micro Sv/h. This value is then divided by10 to give 1.27, and this is then rounded up to give a TI of 1.3 (as above).
The TI should be made up of the sum of all radiations present, which in the main will be gamma radiation but could also include neutrons (in the case of an AmBe source or a radionuclide such as Cf-252). Where possible the neutron dose rate should be measured with a neutron monitor, a TI calculated, and then summed with the gamma TI to provide the full transport TI. However, it is often common practice to infer the neutron dose rate from a known ratio of neutron to gamma dose rates (this having being determined by the source supplier or by the user where both gamma and neutron monitors are available periodically).