More Fuel Rods Melted in Japan

Tuesday, May 24, 2011 @ 02:05 PM gHale

News from Japan seems to get worse and not better as nuclear fuel rods in two more reactors at the damaged Fukushima Daiichi nuclear power plant in Japan melted during the first week of the nuclear crisis, Tokyo Electric Power Co. (TEPCO) officials said Tuesday.

A “major part” of the fuel rods in reactor No. 2 may have melted and fallen to the bottom of the pressure vessel 101 hours after the earthquake and tsunami that crippled the plant, TEPCO said.

The same thing happened within the first 60 hours at reactor No. 3, the company said, releasing a worst-case scenario analysis.

Right now officials feel the fuel is sitting at the bottom of the pressure vessel in each reactor building.

Tokyo Electric also released a second possible scenario for reactors 2 and 3, one that estimates a full meltdown did not occur. In that scenario, the water inside the reactors stayed at a higher level. TEPCO estimated the fuel rods may have also broken in this second scenario, but may not have completely melted.

Temperature data shows the two reactors have cooled sufficiently in the more than two months since the incident, TEPCO said.

The March 11 earthquake and tsunami knocked out cooling systems at Fukushima Daiichi, causing the three operating reactors to overheat. That compounded a natural disaster by spewing vast quantities of radioactive material into the atmosphere.

TEPCO reported that damage to the No. 1 reactor was more extensive than previously believed. The company said the fuel rods at the heart of the reactor melted almost completely in the first 16 hours after the disaster struck, the remnants of that core are now sitting in the bottom of the reactor pressure vessel at the heart of the unit and officials fear that vessel is now leaking.

Tokyo Electric has avoided using the term “meltdown,” and said it is keeping the remnants of the core cool.

A massive hydrogen explosion — a symptom of the reactor’s overheating — blew the roof off the No. 1 reactor unit the day after the earthquake, and another hydrogen blast ripped apart the No. 3 reactor building two days later. A suspected hydrogen detonation within the No. 2 reactor damaged that unit on May 15, officials said.

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