A steam explosion in one of the reactors at the nuclear power stations in Fukushima Prefecture hit by Friday’s devastating earthquake could see radiation spreading as far as Tokyo, a designer of the plant said Sunday.
Speaking at a press conference in Tokyo, Masashi Goto gave reporters a clear explanation of what he believes happened in the reactors at the Fukushima Daiichi (No.1) plant.
‘The problem was with the cooling system,’ said Goto, a former Toshiba employee specializing in containment vessel design. ‘Because this didn’t work, the temperature began to rise, and the water level began to drop. This exposed the upper parts of fuel rods and they started to melt.
‘The pressure in the containment vessel rose to about 1.5 times the level it was designed to withstand. The temperature in the pressure pool began to rise to over 100 degrees Celsius and pure water couldn’t be used to cool the system. People there tried to bring in (sea) water to cool the system.’
Goto said this was a difficult decision for officials as using sea water means there’s no guarantee the reactor can be used again, and, due to aftershocks, there is no guarantee that sea water can settle the reactor.
‘You need water, a pump and electricity to pump in water,’ he said. ‘Yet the entire site had no access to electricity, and two emergency diesel generators didn’t start up at the No. 1 reactor.
‘The build-up of pressure meant there was a real possibility of an explosion, which is why officials released a vent. By releasing radioactive materials into the air, you are defeating the purpose, but they had no choice.’
Goto believes the worst case scenario would be a steam explosion.
‘If water pumped into the system mixes with waste products, a steam explosion can occur,’ he said. ‘This is a physical explosion similar to magma from a volcano falling into water. This is very dangerous…This power plant has several reactors and if one goes off it could affect the others.’
Goto said this was a possibility and (depending on wind direction) could result in radiation reaching the Tokyo area, although he added: ‘No-one knows the exact situation inside the vessel.’
When asked whether the French government was right to recommend its citizens leave the Kanto area for a few days due to the risk of further large earthquakes and uncertainty over the nuclear plants, Goto responded: ‘It’s hard to say. People need all the information available to make informed decisions. We need data and we need to understand risks.’
Goto was appearing with members of the Citizens' Nuclear Information Centre (CNIC), an anti- nuclear public interest group. He will be speaking at the Foreign Correspondents’ Club of Japan again today to give an update.
Meanwhile, Prime Minister Naoto Kan announced Sunday that nine prefectures around Tokyo will be subject to rolling three-hour power outages in a bid to prevent the electricity grid breaking down. The enforced blackouts will be the first in Japanese history.
The blog below gives English language details of where and when the outages will take place, and also lists some foreign language news sources.