ASSESSING COSTS AND EFFECTIVENESS OF SAFETY MEASURES FOR THE TRANSIT OF SMALL TYPE A PACKAGES THROUGH ROAD TUNNELS

ASSESSING COSTS AND EFFECTIVENESS OF SAFETY MEASURES FOR THE TRANSIT OF SMALL TYPE A PACKAGES THROUGH ROAD TUNNELS. The Mont Blanc Tunnel is situated under the highest mountain in Europe. Being 12 km long, it is also one of the longest road tunnels in the world. Local authorities have to state whether the general regulations for the road transportation of radioactive materials, as defined by the IAEA, apply, or whether additive measures need to be taken. Whereas an activity limit- A2 - applies only to the content of a Type A package containing dispersible materials, a derived Limit applying to the whole cargo of a truck has been in use in the tunnel and can be redefined. The present paper deals with the question of the choice of a proper figure for such a limit that might regulate the transit for technetium generators (Elumatic III from Oris France). The first step of the study is a risk assessment, with the truck content as an explicit parameter. The yearly traffic is of 150 trucks, carrying, on the average, 26 Ci of technetium-99 m in Elumatic generators at the time of the crossing. On a yearly basis about 5 X I 01 road accidents might be expected, while the expected radiological fatalities would amount to approximately 2 X I o-s and the expected monetary loss would be US $1 0. The second step is the implementation of decision aiding techniques based on the previous estimates. As the mathematical expectations of such risk indices were not dependent on the shipped activity, a classical approach, the cost effectiveness curve, did not lead to an optimum. Other approaches and other criteria were investigated, such as the comparison with other hazardous materials, the likelihood of lethal or morbidity effects and ground contamination. Should the latter criterion be considered pertinent, it would lead to a limit of 130 Ci of technetium at the time the truck crosses the tunnel.