Date: Sunday, June 05, 2011 10:50 +0900 (JST)
Tokyo Electric Power Company has found that pressure inside the Number 1 reactor at its Fukushima Daiichi power plant has dropped to close to the outside atmospheric pressure. It reaffirms that the reactor has been damaged.
The reactor is believed to have suffered a meltdown after the March 11th disaster. The meltdown apparently created holes in the pressure vessel and damaged the containment vessel, letting highly radioactive water flow below ground in the reactor building.
Pressure inside an operating reactor is normally around 70 atmospheres. But after the disaster, the pressure indicator showed 6 atmospheres in the Number 1 reactor, raising questions about data reliability.
On Friday, the utility replaced the gauge with a new one and made measurements again.
The reading was 1.26 atmospheres as of 11 AM on Saturday, almost equal to normal air pressure. The company says this proves that air inside the reactor is escaping outside.
But the utility estimates that the lack of a big hole in the reactor is keeping steam inside, leading to the slightly higher interior pressure.
TEPCO is also planning to install new pressure gauges at the Number 2 and 3 reactors to assess the situation accurately.
Note on above article: It is good to get new measuring equipment in to the reactor, but the MEXT (Ministry of Education, Culture, Sports, Science and Technology) data from the chart below shows that the pressure in reactor 1 is already known to be low at least since May 13, 2011 (which is the earliest value in this data set). It is not exactly news that the reactor pressure has been near 1.2 atmospheres. 1 MPa (megapascal) is approximately 10 atmospheres so multiplying the readings below by 10 gives a fairly close result based on atmospheres.
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