Japan Raises Fukushima to INES Level 7 — Matching Chernobyl

On April 12, 2011, Japan's Nuclear and Industrial Safety Agency (NISA) raised the Fukushima Daiichi accident rating to Level 7 on the International Nuclear Event Scale—the maximum level, shared only with the 1986 Chernobyl disaster. Japan estimated that 370,000–630,000 terabecquerels of radioactive iodine-131 equivalent had been released, compared to Chernobyl's estimated 5.2 million TBq. Authorities were careful to note the total release was approximately 10% of Chernobyl's, and that most Japanese radiation release went into the Pacific Ocean rather than over populated land.