The operator of the crippled Fukushima Daiichi nuclear power plant said Thursday that a groundwater sample taken from a well at the site in July last year contained a record-high 5 million becquerels per liter of radioactive strontium-90.The operator of the crippled Fukushima Daiichi nuclear power plant said Thursday that a groundwater sample taken from a well at the site in July last year contained a record-high 5 million becquerels per liter of radioactive strontium-90.