NEW : Limit raised from 100 watts to 150 watts . TEPCO president apologizes . Nuclear official bursts into tears . Japanese officials have studied a plan to dump tons of sand and concrete on the plant to encase it , putting out any fires and preventing further radiation from escaping , Nishiyama said . U.N. nuclear tests : No harmful radiation is detected at any of 47 sites .
NEW : Limit raised from 100 watts to 150 watts . TEPCO president apologizes . Nuclear official bursts into tears . U.N. nuclear tests : No harmful radiation is detected at any of 47 sites .