Radioactive strontium detected more than 30 km from Fukushima plant 13 Apr 2011 Minute amounts of radioactive strontium have been detected in soil and plants in Fukushima Prefecture beyond the 30-kilometer zone around the crippled Fukushima Daiichi Nuclear Power Station, the science ministry said Tuesday. It is the first time that radioactive strontium has been detected since the Fukushima plant began leaking radioactive substances after it was severely damaged by the March 11 earthquake and tsunami.