APSN | Japan nuke crisis 'twice as bad'

Home > North-East Asia >> Japan

Japan nuke crisis 'twice as bad'

The Australian - June 8, 2011

Poll: Most Japanese distrust government on nuke crisis - Associated Press. May 30, 2011
Fukushima tsunami plan a single page - Associated Press. May 27, 2011
Ghost towns around Japan's crippled nuclear plant - Straits Times. May 20, 2011
New setbacks at Japan nuclear plant - Agence France Presse. May 12, 2011
Asbestos, Japan tsunami's other hidden danger - Associated Press. April 27, 2011

Rick Wallace, Tokyo – The Fukushima nuclear crisis led to more than twice as much radiation being emitted as previously thought, according to the latest government estimate.

Japan's Nuclear and Industrial Safety Agency has dramatically increased its estimate of the total radiation released to 770,000 terabecquerels of iodine-131 equivalent, up from 370,000 terabecquerels under its previous estimate.

In layman's terms, the first estimate represented about 7 per cent of what was emitted in the 1986 Chernobyl disaster, the only nuclear disaster to supersede Fukushima in severity. The updated estimate is about 15 per cent of the total Chernobyl release.

The comparisons are made by giving each type of particle emitted a weighting to convert them to equivalents of iodine-131, an isotope commonly produced in nuclear accidents that is associated with thyroid cancer when absorbed in large quantities.

The agency made the upgraded estimate after adding in radiation thought to have leaked from the No 2 reactor to the figure used in the initial estimate, based only on reactors No 1 and No 3.

The upgraded estimate is just the latest in a string of findings that show the effect of the explosions and steam venting at the Fukushima Daiichi plant in the days after the March 11 earthquake and tsunami has had a more pronounced impact than first thought.

Early last month, plant operator TEPCO was forced to admit severe melting of fuel rods occurred at reactor No 1 at Fukushima Daiichi and probably at reactors No 2 and No 3.

The base of the stainless steel pressure vessels of these reactors may have been damaged by the molten fuel. Although radiation levels almost everywhere in Japan, excluding the immediate vicinity of the plant, have returned to near-normal, some radiation "hot spots" were discovered this week well outside the 30km exclusion zone around Fukushima Daiichi.

Green tea and plums have become the latest foods to be contaminated with fallout.

Authorities were recently forced by parent anger to begin clearing radioactive topsoil from school playgrounds around the stricken nuclear plant and reinstate tough annual exposure limits for children that had been raised after the disaster.

Radioactive isotopes have been detected in sea and river water and the Japanese government yesterday announced it would begin making radiation checks in popular bathing spots over summer to protect people's health.

Most of the total radiation released under the revised estimate occurred in the first days after the tsunami amid efforts to vent stream that led to several hydrogen explosions that damaged the buildings at several reactors.

The situation at the plant has been temporarily stabilised and radiation emissions have been reduced to low levels, although "cold shutdown" of the overheating reactors remains at least six months away on most estimates.

The new assessment is expected to be reflected in Japan's report on the accident to be submitted to a nuclear safety ministerial meeting hosted by the International Atomic Energy Agency later in the month.