Posts Tagged ‘Nuclear and Industrial Safety Agency’

Fukushima Dai-ichi nuclear plant: Reactor vessel integrity may be compromised

March 26, 2011

Leakage of water with high levels of radioactivity  raise the possibility that there may be cracks in the reactor containment vessels of Reactors #1,2 and 3.  One saving grace is that the pressure in the vessels remains high and would argue against a breach. However cracks below the water level that permit some water seepage  cannot be ruled out. It is also possible that the leakage of radioactive water is not from the vessel itself but from some of the surrounding valves or piping.

The Guardian:

A suspected break in the core of a nuclear reactor could have been responsible for a leak of large amounts of radioactive contamination at the Fukushima Daiichi power plant, Japanese nuclear safety officials said on Friday, in another setback to efforts to avert disaster at the stricken facility.

In the latest developments, officials have said seawater outside one of the units has registered 1,250 the normal level of radiation, while efforts are under way to pump radioactive water that has pooled around the reactor turbines into safe storage. The BBC has reported that short-term radioactive iodine has been detected at very high levels in the Pacific Ocean near the plant.

US naval barges have started rushing in supplies of fresh water amid concerns the seawater being used to cool down the reactors might be causing corrosion. …

On Thursday three workers were exposed to unusually high levels of radiation after stepping in contaminated water in the turbine building of the crippled No. 3 reactor, which they were trying to cool.

Two received possible beta ray burns to their legs. All three have been transferred to a special radiation treatment facility. Kyodo news reported that the two more seriously injured workers could have suffered internal radiation exposure.

“The contaminated water had 10,000 times the amount of radiation as would be found in water circulating from a normally operating reactor,” said Hidehiko Nishiyama, a spokesman for Japan’s nuclear safety agency.

Nishiyama said it was unlikely that the reactor had cracked, but conceded that the unusually high levels of radiation appeared to have originated from its core. “It is possible there may be damage somewhere in the reactor,” he said, adding that a leak in the plumbing or the vents could also be to blame.

GE BWR cutaway : image

NHK World reports:

A high level of radioactive iodine has been detected in seawater near Japan’s troubled Fukushima Daiichi nuclear power plant. The facility was hit by the March 11th earthquake and tsunami.

The Nuclear and Industrial Safety Agency said on Saturday that iodine 131 in excess of 1,250 times regulated standards was found in seawater collected 330 meters south of a plant water outlet at 8:30 AM on Friday.

The agency says there is no immediate threat to people within the 20-kilometer evacuation zone. The agency adds that as seawater is dispersed by ocean currents the contamination level will decline.

Iodine 131 at146.9 times regulated standards was detected in seawater in the area on Wednesday.

Saturday, March 26, 2011 12:44 +0900 (JST)

Kyodo News:

TEPCO, is currently injecting fresh water into the No. 2 reactor core to prevent crystallized salt from seawater already injected from forming a crust on the fuel rods and hampering the smooth circulation of water, thus diminishing the cooling effect. It has begun injecting fresh water into the No. 1 and No. 3 reactor cores.

At the same time, the firm is trying to remove pools of water containing highly concentrated radioactive substances that may have seeped from either the reactor cores or the spent fuel pools, while also trying to restore power at the No. 2 reactor.

On Thursday, three workers were exposed to water containing radioactive materials 10,000 times the normal level at the turbine building connected to the No. 3 reactor building. On Friday, a pool of water with similarly highly concentrated radioactive materials was found in the No. 1 reactor’s turbine building, causing some restoration work to be suspended.

Similar pools of water were also found in the turbine buildings of the No. 2 and No. 4 reactors, measuring up to 1 meter and 80 centimeters deep, respectively. Those near the No. 1 and No. 3 reactors were up to 40 cm and 1.5 meters deep. ..

The U.S. Department of Energy said in its radiological assessment released Friday that by comparing aerial measurement data from Thursday with previous measurements, the data indicate peak exposure rates in the western side of the Fukushima plant are lower.


Fukushima Dai-ichi plant: Work stopped as steam rises from reactors # 2 and 3

March 21, 2011

Work to connect power cables to the No. 3 and No. 4 reactors was halted Monday at the crisis-hit Fukushima Daiichi nuclear power plant, after smoke rose from the buildings housing the No. 2 and No. 3 reactors, the plant operator said.

TEPCO said it had briefly evacuated its workers after grayish and blackish smoke was spotted at the southeast of the No. 3 reactor building around 3:55 p.m. above a pool storing spent nuclear fuel, though a blast was not heard.

The smoke stopped after 6 p.m., but TEPCO subsequently found that white smoke was rising through a crack in the roof of the building that houses the No. 2 reactor at around 6:20 p.m. The utility said later the smoke is believed to be steam, not from the reactor’s fuel pool. As the No. 3 reactor remains without power, smoke was not apparently triggered by an electricity leak or short-circuiting.

The government’s Nuclear and Industrial Safety Agency said no injuries were confirmed in the incidents and that there have been no major changes in the radiation levels at the site.

Before the smoke was detected, external power had reached the power-receiving facilities of the No. 2 and No. 5 reactors on Sunday, clearing the way for the plant operator to restore systems to monitor radiation levels and other data, light the control rooms and cool down the reactors and their spent-fuel storage pools. On Monday, TEPCO finished laying cables to transmit electricity to the No. 4 reactor, as a step toward resuscitating the power systems at the No. 3 and No. 4 reactors, according to the utility and the nuclear agency.

International Atomic Energy Agency Director General Yukiya Amano told a special meeting of its board of governors that the situation at the Fukushima plant ”remains serious, but we are starting to see some positive developments.”

Tokyo Electric Power Co. said it will resume the operation on Tuesday after observing the situation at the site.



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