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Pressure drops inside vessel at Fukushima plant

February 13 earthquake could have exposed damaged part

February 22, 2021

Tokyo Electric Power Company has found that the pressure inside one of the reactor containment vessels at the Fukushima Daiichi nuclear plant has dropped.

The utility said the earthquake that hit the area on February 13 may have been to blame. TEPCO said no radioactive material has leaked.

The nuclear plant in Fukushima Prefecture in northeastern Japan is now undergoing decommissioning.

TEPCO said it confirmed at around 6 p.m. on Sunday that pressure inside the vessel of the No.1 reactor dropped to 0.9 kilopascals from the usual 1.2 kilopascals. Nitrogen is being added to the vessel to raise the pressure and reduce the risk of a hydrogen explosion.

TEPCO found that after the quake the level of water in the containment vessel had dropped.

It said the part damaged in the 2011 nuclear accident may have been exposed after the water level dropped, possibly causing an air leakage and the drop in pressure.

TEPCO said it is continuing to pump water into the vessel and there should be no safety problem.

It said there have been no abnormality in the measurements at radioactivity monitoring posts in the compound.

The utility said it will keep watching the data at the vessel and other facilities

February 25, 2021 Posted by | Fukushima 2021 | , , , | Leave a comment

Water levels at Fukushima reactor containers falling after quake

A Tepco employee wearing a protective suit and mask gives lectures in front of No. 3 reactor building at the tsunami-crippled Fukushima No. 1 nuclear power plant in Okuma, Fukushima Prefecture, in February 2019.

February 20, 2021

Tokyo Electric Power Co. Holdings Inc. has said that the water levels in the containment vessels for the No. 1 and No. 3 reactors at its disaster-crippled Fukushima No. 1 nuclear power plant have fallen by tens of centimeters.

The water levels are continuing to drop by several centimeters each day, Tepco said Friday.

The event has had no radiation impact outside of the plant’s premises, the company said, noting that the injection of water into the reactors, as well as operations to cool melted nuclear fuel debris at the bottom of the containment vessels, are continuing.

The plant was heavily damaged in the powerful March 2011 earthquake and tsunami.

On Feb. 13, an earthquake measuring a strong 6 — the second-highest level on the Japanese seismic intensity scale — rocked the Tohoku region, which includes Fukushima Prefecture. Existing damage to piping and other parts of the containment vessels may have expanded as a result of the temblor, Tepco officials said.

The utility is continuing to pump 3 tons of water per hour into the reactor containers to cool the fuel debris.

While water continues leaking to the reactor buildings through the damaged areas of the containment vessels, the water levels in the No. 1 and No. 3 reactor containers had been kept at some 1.9 meters and 6.3 meters from the bottom, respectively, before Saturday’s earthquake.

According to the officials, workers detected a fall in the water level in the No. 1 reactor container around 11 p.m. Thursday.

The water level is seen to have dropped by 40-70 centimeters in the No. 1 reactor container and by some 30 centimeters in the No. 3 reactor container, the officials said.

Drops in the water levels are believed to have started around Monday in the No. 1 reactor vessel and around Sunday in the No. 3 reactor vessel, they said.

The sizes of the falls in the water levels are almost the same as those observed during an experiment conducted last year to suspend water injection, the officials said.

The company will take measures, such as increasing water injection, as needed while continuing to monitor the water levels, the officials said.

Ramping up water injection will lead to an increase in the amount of radioactive water, possibly affecting the quantity of water that is kept in tanks at the premises of the nuclear power station after being treated to remove some radioactive substances.

February 21, 2021 Posted by | Fukushima 2021 | , , , , | Leave a comment

Water level drops at Daiichi Nuclear Power Plant Units 1 and 3

February 19, 2021

The Tokyo Electric Power Company (TEPCO) has announced that the water level inside the containment vessels of the Unit 1 and Unit 3 reactors at the Fukushima Daiichi Nuclear Power Plant, which are filled with water to cool down the melted down nuclear fuel, is dropping.
There is a possibility that a broken part of the containment vessel expanded after the earthquake on the 13th of this month, increasing the amount of water leaking out, but there has been no noticeable change in the values of monitoring posts, etc., and there is no impact on the outside.

According to the Tokyo Electric Power Company (TEPCO), at around 11:00 p.m. on the 18th, it was confirmed that the water level in the containment vessel of the Unit 1 reactor, which is used to cool down the melted down nuclear fuel, had dropped.
TEPCO confirmed the data and found that the water level has been declining since the 15th of this month in the Unit 1 reactor and since the 17th in the Unit 3 reactor.
The water level in the Unit 1 reactor is estimated to have dropped by 40 to 70 centimeters, and in the Unit 3 reactor by about 30 centimeters.
However, the thermometers installed at the bottom of the reactors do not show any rise in temperature, there is no noticeable change in the radiation level inside the containment vessel, and there is no abnormality in the values of the monitoring posts installed at the site boundary. There is no problem with the cooling of the nuclear fuel and no external impact.
The containment vessel was broken during the accident at the nuclear power plant, and a certain amount of cooling water that is poured into the vessel usually leaks out, but the earthquake on the 13th of this month may have widened the damaged area and increased the amount that leaked out.
In the towns of Okuma and Futaba, where the Fukushima Daiichi Nuclear Power Plant is located, a tremor of lower 6 on the Japanese intensity scale was observed.
If the water level continues to drop, TEPCO is considering increasing the water injection rate, which is currently set at 3 cubic meters per hour.

February 21, 2021 Posted by | Fukushima 2021 | , , , | Leave a comment