Fukushima Daiichi two weeks on

Friday, 25 March 2011

ORIGINALLY PUBLISHED: 3.55pm GMT

UPDATE 1: 4.08pm GMT, Addition of box on thyroid tests

  

Tokyo Electric Power Company has been criticised over yesterday's exposure to workers operating in ankle-deep water, but continues to make progress towards stabilising the site two weeks after the natural disasters of 11 March.

 

The Nuclear and Industrial Safety Agency has told the company to improve its radiation monitoring and the controls protecting workers that are bringing systems back online at Fukushima Daiichi.

 

 

Thyroid examinations   Japanese authorities have reported to the IAEA after examining the thyroid glands of 66 children, including 14 infants. The results 'had no big difference from the level of background and was at the level of no problem in the view of the Nuclear Safety Commission.'   Releases of iodine-131 pose a potential threat to young people and children because the iodine is drawn to the thyroid where its radioactivity can lead to cancer. To avoid this possibility, potassium-iodide pills were distributed, and the order given to take them made on 16 March. The saturation of the thyroid with stable iodine prevents uptake of the radioactive form should a person ingest it.

It is of course understandable that the lower part of the turbine building of unit 3, in which three workers were installing cables, had not been fully checked. But it is thought that contractors ignored alarms from their dosimeters, while ankle-deep in contaminated water for about three hours. They received doses of 170-180 millisieverts and seem to have suffered shallow burns to their skin from beta radiation.

 

 

The International Atomic Energy Agency said that 17 personnel have now received radiation doses of over 100 millisieverts. This level remains below an international standard of 500 millisieverts for emergencies, as well as a temporary limit of 250 millisieverts allowed by authorities in the current situation.

 

Investigations are now underway into the unexpectedly high level of contamination in the water, particularly as the basement of the turbine building is not a recognised radiation area. One theory is that there is a leak from the reactor circuit, but pressures in the reactor vessel indicate this must be elsewhere in the loop.

 

Despite this disappointment, steady progress continues to be made on site. Instrumentation is being recovered at units 1, 2 and 4 and lights are on in the control rooms of units 1 and 3. Power connections have reached all the units and checks are underway before normal systems can be re-energised. The shared pond for used fuel pond has now been reconnected.

 

 

A situation summary from the World Health Organisation put the death toll from the 11 March earthquake and tsunami at over 8800 confirmed dead with more than 12,600 still missing. More recent reports now put the cost at over 10,000 lives.   In total almost 320,000 people have been evacuated, with over 130,000 of these from Fukushima prefecture for reasons of both the tsunami and the nuclear emergency.   Over 220,000 homes are still without access to electricity, notwithstanding the non-operation of nuclear and fossil power plants. Gas supplies are disrupted to almost 440,000 homes. Some 1700 roads are damaged with many of these closed. More than 50 bridges are down.

Freshwater is replacing seawater for injection to the reactor systems of units 1 and 3. This is to prevent salt accumulation and damage to main pumps, which Tepco hope to bring back into operation once checks are complete. Preparations are underway to use freshwater at unit 2 as well with all the supplies coming from Sakashita Dam.

 

 

Water injection work has continued to the fuel ponds of units 2 and 4 using the pool cleaning and filtering systems, while unit 3 was sprayed by fire trucks. Tepco is maintaining a watch on all the fuel ponds and will continue to spray and inject as necessary.

 

The residual heat removal system of cold shutdown unit 5 is now back in operation after a trip two days ago, although the loss of this did not threaten the reactor's cold shutdown status. External power for units 5 and 6 comes from diesel generators brought back into service.

 

Researched and written

by World Nuclear News