03 April 2011
Two workers missing since the natural disasters of 11 March have now been found dead in the turbine building of Fukushima Daiichi unit 4.
Kazuhito Kokubo and Yoshiki Terashima, aged 24 and 21 respectively, were found in the '-1' level of unit 4's turbine hall. The chairman of Tokyo Electric Power Company, Tsunehisa Katsumata, said they had been "working to protect the safety of the Fukushima power station after the earthquake and tsunami." Similar basement levels of other reactors on the site have been found to be flooded, possibly by tsunami water flowing through cabling trenches close to the seafront.
One worker also died at Fukushina Daini after suffering serious injuries and becoming trapped in the crane operating console of the exhaust stack of one of the units during the earthquake.
Like many coastal zones in northeastern Japan, the area near the nuclear power plant was utterly devastated. See image.
These three are the only deaths at nuclear power plants from the earthquake, tsunami and subsequent nuclear emergency. No effects on health or significant contamination cases have been identified among the general public evacuated from the area. The tsunami travelled up to five kilometres inland in Fukushima prefecture, causing a 1113 deaths with 4626 more people still missing. The totals for Japan as a whole are 12,087 dead and 15,552 missing as of today.
Among the 370 workers working to bring stability to the damaged reactor units of the Daiichi plant, 21 have so far experienced radiation doses of over 100 millisieverts.
Normally nuclear workers are allowed to receive a dose of 20 millisieverts over a whole year, although in practice they often receive very much less. If that limit is exceeded in any year, the worker cannot undertake nuclear duties for the remainder.
In emergency circumstances safety regulators allow workers to receive up to 100 millisieverts with the same conditions applying, that they must leave the site should that limit be reached. The 100 millisievert level is roughly the point at which health effects from radiation become more likely. Below this it is statistically difficult to connect radiation dose to cancer rates, but above this the relationship starts to become apparent when looking at a large group.
Japanese authorities have authorised exposures of up to 250 millisieverts in the efforts to bring the Fukushima situation under full control. So far no-one has been exposed to these levels.
Researched and written by World Nuclear News
