At Fukushima Daiichi in Japan, nuclear reactor Unit 1 is being prepared for 'cold shutdown,' which requires flooding the reactor's containment structure with cold water to stop steam production.
Kim Kyung-Hoon / Reuters / File
If that happened, it would be a major shift from the nuclear plant's current status, which the International Atomic Energy Agency still lists as "very serious." Cold shutdown means bringing the temperature inside the reactor down below the boiling point of water, so no steam pressure is being produced – a significant step if it happens, US experts said.
Before the temperature can be reduced, the building must be vented of radioactive air to allow operators to approach the reactor. In addition, American and British scientists have expressed concerns about the proposed step and newly discovered evidence of an ongoing radiation leak into the Pacific Ocean.
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