25 Décembre 2013
December 25, 2013
An estimated 225 tons of radioactive rainwater likely leaked from cracks in the barriers surrounding storage tanks at the crippled Fukushima No. 1 nuclear power plant, seeping into the surrounding soil, Tokyo Electric Power Co. said Dec. 24.
The utility said this appears to be the largest amount of radioactive rainwater escaping to date from the barriers around tanks holding contaminated water.
TEPCO plans to apply nonpermeable resin on the inside of the barriers to block future leaks.
The company said water levels inside the barriers of the H4 and H4-East storage areas dropped over four days through Dec. 24.
The water level at the H4-East area fell from 12 centimeters to 1 cm, suggesting a leak of 109 tons. The level at the H4 area dropped from 12 cm to 5 cm, indicating a leak of up to 116 tons.
A reading of 440 becquerels of radioactive strontium per liter was detected Dec. 20 in water in the barriers at the H4-East area. The reading at the H4 area was 20 becquerels per liter. Both figures exceeded TEPCO’s provisional limit of less than 10 becquerels for releasing contaminated water.
The figures indicate that the rainwater has been contaminated by absorbing radioactive substances from the surface of the soil.
Additional leaks of radioactive water at the crippled Fukushima No. 1 Nuclear Power Plant have been revealed following earlier leaks on Dec. 21 and 22.
On Dec. 24, plant operator Tokyo Electric Power Co. (TEPCO) announced that it had found lowered water levels within concrete boundaries set up around radioactive water-containing storage tanks in two areas. The zones were separate from two areas where water leaks occurred on Dec. 21 and 22.
Around 225 tons are suspected to have leaked in the latest incident, but the areas around the concrete boundaries were not wet. "The water may have seeped into the ground. We will investigate," a TEPCO representative said.
According to TEPCO, in one of the bounded areas contaminated water was around 12 centimeters deep on Dec. 20 but was reduced to around 5 centimeters on Dec. 24. In the other area, the water level fell from around 12 centimeters on Dec. 20 to around 1 centimeter on Dec. 24. The radioactive water contained concentrations of radioactive Strontium-90 that were as high as 440 becquerels per liter. TEPCO's temporary limit for the release of radioactive water from the concrete boundaries is that it contains less than 10 becquerels of Strontium-90 per liter.
Some 3.4 tons leaked on Dec. 21 and 22 and contained concentrations of up to 1,000 becquerels per liter of beta-ray releasing radioactive materials like Strontium-90. Possible reasons for those leaks given by TEPCO include a weakening of resin at the connection points of parts of the concrete boundaries and the opening of cracks in the concrete.
December 24, 2013
Falling water levels within barriers hint at leaks
The operator of the crippled Fukushima Daiichi nuclear power plant says water levels have dropped sharply inside another 2 barriers surrounding contaminated water tanks.
Tokyo Electric Power Company says its workers discovered the phenomenon on Tuesday at 2 barriers near the number 4 reactor building. The water levels in question were last checked on Friday.
TEPCO officials say the water levels dropped 11 centimeters from Friday inside one barrier, and 7 centimeters in the other.
They say nothing suggests that the water leaked into the surrounding ground. And they have noticed no changes in water levels in tanks in the area.
TEPCO officials say the water within the barriers contains up to 440 becquerels per liter of radioactive strontium---44 times the government limit for radioactive water to be released from the barrier.
The officials suspect that the water might have gradually seeped into the soil beneath the tank lots.
They plan to drain the water within the barriers and find out what caused the water levels to fall. The utility suspects cracks in the concrete barriers.
Contaminated water leaks from similar lots have already been discovered at 4 different locations over the weekend.