“Step by step, the reactors in the Fukushima Daiichi power plant are moving
toward stability,” Prime Minister Naoto Kan told a press conference on Tuesday.
According to Japan’s nuclear safety authority, Nisa, the decision to raise the threat level reflects the total release of radiation since last month’s earthquake and tsunami, and its “widespread impact” on the air, food produce, tap water and the ocean.
Level seven on the International Nuclear and Radiological Event Scale (Ines) signifies a major accident with significant effects on public health and the environment. The Fukushima crisis was previously rated at level five, the same as the Three Mile Island disaster in the US.
Nisa says that far less radiation has so far been released from Fukushima than from the Chernobyl nuclear plant in 1986: only around 10 per cent, according to current estimates.
However, the levels could continue to rise. On Tuesday, traces of the highly radioactive element strontium were found in soil and plants near the Fukushima plant, the government confirmed.
Japan has “no plans” to stop operating nuclear reactors in the wake of the crisis, said Prime Minister Kan, though he acknowledged that safety had to be improved.
Energy company Kyushu Electric Power announced on Tuesday it would suspend plans to build a new reactor at its Kagoshima plant, after the local governor told the company that the expansion was not “warranted”.