Plant operator Tepco reveals meltdown and breach of pressure vessel, with Greenpeace warning against pumping water in.
Greenpeace has urged Tepco to abandon plans to flood the container with water, given the likelihood that melted fuel had damaged it. Shaun Burnie, nuclear adviser to Greenpeace Germany, said: "Flooding a reactor that has fuel [that has fallen] through the pressure vessel is not a good idea."
Outlining a worst-case scenario, Burnie said very large amounts of cold water hitting the melted fuel could cause an explosion, trigger susbstantial damage to the reactor and create a "high risk of atmospheric release running for days, if not weeks." He added: "I think [the flooding option] will now be scrapped.
Greenpeace said the situation could escalate rapidly if the fuel melted through the reactor vessel. "As the fuel rods were fully exposed and subsequently melted, it is highly likely that the core's integrity is compromised and that there is larger amount of melted fuel at the bottom of the reactor pressure vessel."John Large, an independent nuclear engineering consultant in London, said Tepco's plan to flood the reactor was riddled with "potential risks". It appeared not to have factored in the extent of damage to the fuel rods and the structural state of the containment vessel, including whether it was watertnight. "It seems to be poorly thought through," he said, adding that the firm had not demonstrated that the strategy could work. "Should it fail, there is and cannot be a contingency plan."
Tepco's Matsumoto ruled out a possible explosion but said: "We have to revise the flooding method. We can't deny the possibility that a hole in the pressure vessel caused water to leak."
The use of water to keep the reactors cool has led to the build-up of about 70,000 tons of contaminated water at Fukushima Daiichi. Tepco is pumping the water into a nearby storage building while it sets up a decontamination system.
Cooling water has leaked from the cores of reactors 2 and 3. One other unit at Fukushima Daiichi did not contain fuel rods at the time of the earthquake, while another two have achieved "cold shutdown" – their cooling water is below boiling point.
The permanent or temporary shutdown of reactors at Fukushima Daiichi and other nuclear plants could leave only a third of Japan's 54 reactors in operation by the end of the month, NHK has reported.
The public broadcaster said the disaster had prompted the suspension of 14 reactors, while 19 others were offline for inspections. Two reactors at Hamaoka nuclear plant in central Japan are to be shut while a tsunami wall is built.
Plan to flood Fukushima reactor could cause new blast, experts warn | World news | guardian.co.uk
Greenpeace has urged Tepco to abandon plans to flood the container with water, given the likelihood that melted fuel had damaged it. Shaun Burnie, nuclear adviser to Greenpeace Germany, said: "Flooding a reactor that has fuel [that has fallen] through the pressure vessel is not a good idea."
Outlining a worst-case scenario, Burnie said very large amounts of cold water hitting the melted fuel could cause an explosion, trigger susbstantial damage to the reactor and create a "high risk of atmospheric release running for days, if not weeks." He added: "I think [the flooding option] will now be scrapped.
Greenpeace said the situation could escalate rapidly if the fuel melted through the reactor vessel. "As the fuel rods were fully exposed and subsequently melted, it is highly likely that the core's integrity is compromised and that there is larger amount of melted fuel at the bottom of the reactor pressure vessel."John Large, an independent nuclear engineering consultant in London, said Tepco's plan to flood the reactor was riddled with "potential risks". It appeared not to have factored in the extent of damage to the fuel rods and the structural state of the containment vessel, including whether it was watertnight. "It seems to be poorly thought through," he said, adding that the firm had not demonstrated that the strategy could work. "Should it fail, there is and cannot be a contingency plan."
Tepco's Matsumoto ruled out a possible explosion but said: "We have to revise the flooding method. We can't deny the possibility that a hole in the pressure vessel caused water to leak."
The use of water to keep the reactors cool has led to the build-up of about 70,000 tons of contaminated water at Fukushima Daiichi. Tepco is pumping the water into a nearby storage building while it sets up a decontamination system.
Cooling water has leaked from the cores of reactors 2 and 3. One other unit at Fukushima Daiichi did not contain fuel rods at the time of the earthquake, while another two have achieved "cold shutdown" – their cooling water is below boiling point.
The permanent or temporary shutdown of reactors at Fukushima Daiichi and other nuclear plants could leave only a third of Japan's 54 reactors in operation by the end of the month, NHK has reported.
The public broadcaster said the disaster had prompted the suspension of 14 reactors, while 19 others were offline for inspections. Two reactors at Hamaoka nuclear plant in central Japan are to be shut while a tsunami wall is built.
Plan to flood Fukushima reactor could cause new blast, experts warn | World news | guardian.co.uk
