Is Nuclear Meltdown Inevitable at Japan's Crippled Nuclear Plant?

Dangerous radiation levels in damaged reactor 3 at Fukushima Daiichi nuclear plant forced Tokyo Electric Power Company to suspend operations Wednesday morning. Operations resumed once radiation levels subsided. All except 50 workers had been sent home Tuesday due to the increasing radiation threat. Those 50 workers face a constantly-evolving prospect of nuclear meltdown at multiple Fukushima reactors.

According to NHK, Japan has increased by a factor of 2.5 the acceptable radiation exposure for nuclear plant workers. The new threshold, applicable to emergency operations, is 250 millisieverts.

Latest Developments

• * Reactor no. 3 is believed to be damaged, responsible for leaking highly-radioactive steam Wednesday, Chief Cabinet Secretary Eukio Edano announced. The radiation spurt was short-lived but topped 1000 millisieverts before dropping, according to CBS News.
• * The housing around unit 4 has two holes in it, and the water surrounding the fuel rods may be boiling. One of the holes is 8 meters square.
• * Reactor 4 was on fire early Wednesday and workers could not get close enough to determine for certain whether the fire was successfully extinguished. The same reactor was on fire Tuesday, a fire that possibly was never fully put out and renewed itself Wednesday.
• * Reactor units 5 and 6 are also in trouble, with the temperature rising in the pools that cool the spent fuel rods and the water surrounding the rods possibly boiling.
• * Authorities believe 70 percent of the fuel rods in reactor 1 and 33 percent in reactor 2 are damaged. The fuel rods in both reactors were exposed to air, and coolant levels were low.
• * Japan's computer system that measures the spread of radioactivity, called SPEEDI, is inoperable due to malfunctioning monitors at Fukushima. The government is unable to predict when SPEEDI will be fixed.
• * Japan's Health and Labor Ministry said it does not know whether the new radiation threshold for workers conducting emergency shutdown operations exposes them to health damage. The international threshold is 500 millisieverts. The Ministry said its own new limit, though unsupported by data, was necessary to prevent nuclear disaster.

Complete Nuclear Meltdown Near-at- Hand?

Japan is in uncharted territory, where it may face multiple nuclear reactor meltdowns simultaneously. Nuclear experts have said previously that water boiling away in the cooling pools could trigger complete meltdown. If the water evaporates, the temperature of the rods will increase. As the rods melt, the molten material will likely penetrate the reactor floor and leak beyond the containment vessel, emitting radioactive clouds into the atmosphere.

Alternatively, exposure to air as the water levels decrease could set the rods on fire, causing the dispersion of radioactive smoke. This is likely what started the fire in reactor 4.

Japan's Desperate Measures to Stabilize Fukushima Reactors

Saturday, nuclear expert Robert Alvarez described Japan's desperate decision to try to cool the reactors by pumping in seawater a "Hail Mary pass." Hail Mary has transformed into a full-fledged novena with Wednesday's planning: TEPCO considered an aerial spray-down of reactor 4, directing boron-laced water into the hole in the roof and hoping to aim it toward the the storage pool some distance away. TEPCO reconsidered, deciding that the helicopter's limited carrying capacity and the maneuver's difficulty would likely doom it to failure. TEPCO is desperately crafting alternatives including the possibility of trying a similar maneuver from the ground using fire engines.

The Japanese government issued an urgent plea to the International Atomic Energy Agency Monday to send in nuclear accident experts. IAEA Director General Yukiya Amano promised Wednesday to dispatch experts in environmental monitoring and assistance coordination.

South Korea's state-run power company is shipping its own boron reserves to Japan. Japan's supply was used up in its battle to prevent nuclear meltdown. Boron curtails nuclear fission reactions.