Nuclear Engineering Issues

The Japan Times - June 21, 2011

Tokyo Electric Power Co. continued struggling Monday to restart a newly installed water treatment system at its crippled Fukushima No. 1 nuclear plant, aiming to resume full operations Tuesday.

The treatment system is designed to remove highly radioactive materials from the massive amounts of water accumulating at the plant, thus its full operation is vital for efforts to contain the three-month-old nuclear crisis, because Tepco hopes to eventually recycle the water to cool the plant's damaged reactors.

But the new system was halted at 12:54 a.m. Saturday, after becoming fully operational at 8 p.m. Friday, because the radiation level of a component to absorb cesium had reached its limit and required replacement much earlier than expected, Tepco officials said.

Tepco has been trying to ascertain why the component didn't work as hoped and is probing ways to solve the problem, company officials said.

Tepco meanwhile said Monday it fully opened the doors of the reactor 2 building to lower the humidity inside so workers can enter the site, and denied this would have a negative impact on the environment.

The Yomiuri Shimbun - Daily Yomiuri Online - Associated Press - June 9, 2011

In a report submitted to the International Atomic Energy Agency, the government has called for a drastic revision of nuclear reactor design standards, including the development of air-cooling devices and a reconsideration of the location of temporary storage pools for spent nuclear fuel rods.

The report concerning the accident at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant following the March 11 earthquake and tsunami was submitted to the IAEA on Tuesday.

The report included 28 proposals to strengthen the safety of nuclear plants, drawing on lessons from this year's earthquake-triggered nuclear crisis.

The Economy, Trade and Industry Ministry's Nuclear and Industrial Safety Agency (NISA) the same day instructed electrical utility companies that operate nuclear power plants to take emergency measures to prevent hydrogen explosions and secure sufficient equipment to measure radiation levels.

The report may significantly affect the operations of about 50 nuclear reactors in the nation, observers said.

In this May 27, 2011 photo released by the International Atomic Energy Agency, or IAEA, members of the IAEA fact-finding team in Japan visit the Fukushima Dai-ichi nuclear plant in Okuma, Fukushima prefecture, northern Japan. (AP Photo/IAEA)

Reuters - June 1, 2011

TOKYO, June 1 (Reuters) - Japan underestimated the risk of tsunamis and needs to closely monitor public and workers' health after the crisis at the Fukushima Daiichi nuclear plant, a team of international safety inspectors said in a preliminary review of the world's worst nuclear disaster since Chernobyl.

The report, from an International Atomic Energy Agency (IAEA) team led by Britain's top nuclear safety official Mike Weightman, highlighted some of the well-documented weaknesses that contributed to the crisis at Fukushima when the plant, 240 km (150 miles) north of Tokyo, was hit by a massive earthquake and then a tsunami in quick succession on March 11.

Those start with a failure to plan for a tsunami that would overrun the 5.7-metre (19 ft) break wall at Fukushima and knock out back-up electric generators to four reactors, despite multiple forecasts from a government agency and operator Tokyo Electric Power Co's own scientists that such a risk was looming.

World Health Organization - Fact sheet N° 303 - April 2006

Background

On 26 April 1986, explosions at reactor number four of the nuclear power plant at Chernobyl in Ukraine, a Republic of the former Soviet Union at that time, led to huge releases of radioactive materials into the atmosphere. These materials were deposited mainly over countries in Europe, but especially over large areas of Belarus, the Russian Federation and Ukraine.

An estimated 350 000 clean-up workers or "liquidators" from the army, power plant staff, local police and fire services were initially involved in containing and cleaning up the radioactive debris during 1986-1987. About 240 000 liquidators received the highest radiation doses while conducting major mitigation activities within the 30 km zone around the reactor. Later, the number of registered liquidators rose to 600 000, although only a small fraction of these were exposed to high levels of radiation.

In the spring and summer of 1986, 116 000 people were evacuated from the area surrounding the Chernobyl reactor to non-contaminated areas. Another 230 000 people were relocated in subsequent years.