Japanese automakers, their production stuttering after the tsunami and consequent nuclear reactor problems, now faces a whole new issue - nuclear radiation.With the Fukushima Daiichi nuclear reaction severely damaged, engineers at various vehilce assembly plants and ports of dispatch are assessing whether certain parts (or entire cars) ready for export could potentially be radioactive.WRAPPED AND WASHEDAlthough the likelihood of radioactive cars being exported are low (finished units are plastic-wrapped for export, then washed at their final destination), the current concern is whether parts produced since Japan’s nuclear disaster could be contaminated and accumulated into the future production stream.The manufacturers closest to the issue are Honda and Nissan.Nissan’s Iwaki powertrain plant is 45km from the severely damaged Fukushima Daiichi nuclear power plant. Honda draws engine components from a facility in Tochigi (where Nissan also has an assembly plant), slightly within the 160km radius of Fukushima’s damaged reactors. The auto industry, one of Japan’s most important, is trying desperately to co-ordinate production timetables and balance capacity among its global network of assembly facilities to offset the disastrous state of affairs back home. NOT A FRINGE ISSUEAt this stage industrial engineers are working overtime to calculate the effect on inventory and factor in the status of various smaller component suppliers in the wake of the tsunami. Radiation, though, is not a fringe issue. The airline industry, as an example, is taking no chances. Fears of radioactive fall-out prompted several air carriers to cancel flights to Narita airport, which services Tokyo. Lufthansa, KLM and Air China cancelled flights after a small spike in radiation levels was detected in Tokyo after the reactor fire at the Fukushima.Truth be told, even the best nuclear physicists are not sure about the state of play since the tsunami damage to Fukushima Daiichi’s reactor. The levels of radiation required to contaminate (and fuse) with the metallurgy and blend of polymers and composite materials present in a modern vehicle are very hard to ascertain.So, it's a very uncomfortable waiting game as scientists try to make sense of Japan's worst nuclear disaster since the Second World War.