* Breaking news*  Fox and CNN are reporting #2 Reactor has exploded with possible breach to core containment shell…    #1 and #3 previously exploded but maintained containment shell.   Ongoing….  An explosion was heard Tuesday morning at the Japanese nuclear reactor that has been of greatest concern in the wake of the country’s devastating earthquake and tsunami, which damaged the Fukushima Dai-ichi nuclear plant.  (Read more)  TV reports are stating that half of the fuel rods remain exposed (without coolant), and at several times thoughout the prior days the pressure within the containment unit grew so large that coolant was unable to be pumped in to the chamber.    Link to FOX – Link to CNN    TOKYO — A Japanese utility says fuel rods at a troubled nuclear reactor were once again fully exposed hours after authorities were able to stabilize a similar emergency.  Tokyo Electric Power Co. says the exposure happened at Unit 2 of the Fukushima Dai-ichi plant because a steam vent wouldn’t open Monday, causing a sudden drop of water.  That reactor and two others at the plant are dangerously overheating and authorities are racing to prevent meltdown.

The cause of the explosion at Unit 2 and the conditions at the site weren’t immediately clear, but the news heightened anxiety over the precarious state of the facility.

The fuel rods in all three of the most troubled Japanese nuclear reactors — each of which lost its cooling system in Friday’s massive earthquake and tsunami — appear to be melting, the nation’s chief government spokesman said earlier Monday.

They keep insisting that everything is good, yet each reactor continues to fail…  They keep saying a “full” meltdown will not occur, yet it appears inevitable….

The second hydrogen explosion in three days rocked a Japanese nuclear plant Monday, devastating the structure housing one reactor and injuring 11 workers. Water levels dropped precipitously at another reactor, completely exposing the fuel rods and raising the threat of a meltdown.

The morning explosion in Unit 3 of the Fukushima Dai-ichi plant was felt 25 miles away, but the plant’s operator said radiation levels at the reactor remained within legal limits. Hours later, officials reported that fuel rods at Unit 2 were fully exposed at some point and may have been damaged.

Most attention, though, has been focused on Dai-ichi units 1 and 3, where operators have been funneling in sea water in a last-ditch measure to cool the reactors. A complete meltdown — the melting of the radioactive core — could release radioactive contaminants into the environment and pose major, widespread health risks.

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*Update* (via Fox News) KORIYAMA, Japan – Japanese officials warned of a possible second explosion at a nuclear plant crippled by the earthquake and tsunami as they raced to stave off multiple reactor meltdowns, but they provided few details about whether they were making progress.   More than 180,000 people have evacuated the area, and up to 160 may have been exposed to radiation.

Four nuclear plants in northeastern Japan have reported damage, but the danger appeared to be greatest at the Fukushima Dai-ichi nuclear complex, where one explosion occurred Saturday and a second was feared.   Operators have lost the ability to cool three reactors at Dai-ichi and three more at another nearby complex using usual procedures, after the quake knocked out power and the tsunami swamped backup generators.

Chief Cabinet Secretary Yukio Edano said Sunday that a hydrogen explosion could occur at Dai-ichi’s Unit 3, the latest reactor to face a possible meltdown. That would follow a hydrogen blast Saturday in the plant’s Unit 1.

“At the risk of raising further public concern, we cannot rule out the possibility of an explosion,” Edano said. “If there is an explosion, however, there would be no significant impact on human health.”

Operators have been dumping seawater into units 1 and 3 in a last-ditch measure to cool the reactors. They were getting water into the other four reactors with cooling problems without resorting to corrosive sea water, which likely makes the reactors unusable.

Edano said residents within about 12 miles (20 kilometers) of the Dai-ichi plant were ordered to evacuate as a precaution, and the radioactivity released into the environment so far was so small it didn’t pose any health threats.

Such statements, though, did little to ease public worries. (full article)

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(Sky News)  Around 200,000 people have been evacuated as officials work to prevent a meltdown at a nuclear power plant hit by Japan’s deadly eathquake and tsunami.  Authorities had played down fears of a meltdown after a building housing a reactor was destroyed in an explosion at the Fukushima plant on Saturday.  But concerns have now been raised about the condition of a second reactor at the plant after its cooling systems failed.

(Click Here for Interactive Map) Operator Tokyo Electric Power Company (TEPCO) said it was preparing to release some steam to relieve pressure in the No3 reactor at the plant – 150 miles north of Tokyo.  This plan would release a small amount of radiation.  “We can stabilise the reactor if we take the air out and pump water in the vessel properly,” Japan’s Chief Cabinet Minister Yukio Edano said.   “And as I have mentioned in the past, this will be a controlled release, and in the air will contain radio active substance.   “However this will not affect the health of humans, and we will do this in order to stabilise the reactor in a controlled manner.”

The government has insisted radiation levels are low following Saturday’s explosion, saying the blast had not affected the reactor core container.   Nine people have showed signs of possible exposure to radiation at the Fukushima plant.  And officials from the Japan Nuclear and Industrial Safety Agency told a news conference that up to 160 people may have suffered radiation exposure.  A 12-mile radius has been imposed on the Fukushima Daiichi plant with an estimated 170,000 people already evacuated.

A six-mile exclusion zone is also in place around the nearby Fukushima Daini station, with an estimated 30,000 people told to vacate the area.  Sky News correspondent Holly Williams, in Japan, said: “The Government is saying they are prepared for any eventuality. “But it seems like the authorities themselves are not entirely sure what happened.” (more)

HOW BAD COULD IT GET ? – A COMPARATIVE
(SkyNews)Nuclear experts have warned the next few days will be crucial in determining exactly how bad the fallout from the Fukushima Number 1 power plant disaster could be. Advanced Japanese engineering at the 40-year-old plant will avoid a Chernobyl style disaster, but any radiation leak could have disastrous long term consequences.

The 1986 explosion of Reactor Number Four at Ukraine’s Chernobyl plant was the world’s worst nuclear incident, immediately contaminating 200 people and killing 32 within three months.  Hundreds of thousands of people are thought to have suffered the after effects of the leak.  The accident was only revealed after a giant radioactive cloud was registered moving across northern Europe.  It was marked at the maximum level seven on the international atomic agency’s scale of nuclear accidents.

Further contamination was reported from Chernobyl in 1995 during the removal of fuel from one of the plant’s reactors.  Professor Robin Grimes, from the Centre for Nuclear Engineering, told Sky News that the Chernobyl plant was an old Russian design which had a completely different structure to Fukushima.  “The plants in Japan are light water reactors so they work on a very different principle,” he said.  “The type of problems that one might anticipate will be quite different to Chernobyl.”

He added that the Fukushima incident could be more on the scale of the 1979 accident at Three Mile Island, in Pennsylvania.  Then, 140,000 people were evacuated after the reactor’s core suffered a partial meltdown. Although there was contamination within the plant, there was none outside and no casualties.  The accident registered five on the scale.  Other incidents have included a leak from a plant in Tennessee in 1979, which contaminated some 1,000 people and an explosion at a secret reprocessing plant in Tomsk-7, western Siberia. The number of casualties there is still unclear.

Japan has experienced the only two deadly nuclear accidents since Chernobyl – one in Tokaimura in 1999 which killed two workers and another in Mihama in 2004 which caused four fatalities.   Tokaimura is Japan’s worst nuclear accident to date, and exposed more than 600 people to radiation.  Professor Grimes explained that any damage from Fukushima should be limited because the plant shut down as soon as the earthquake hit.

The explosion at the plant occurred 24 hours after it shut down – unlike Chernobyl, which was active when the leak occurred.  Nuclear expert Malcolm Grimston explained that the actual nuclear core had not become uncovered at Fukushima, diverting a potentially disastrous meltdown.  He told Sky News: “We know this is not a nuclear explosion, this looks like the sort of thing that happens when you demolish a block of flats it’s about that level.  “It could be caused by a build up of pressure – it could be fractured pipes.”

He warned that it was essential to keep the plant cool over the next hours and days to avoid the incident worsening.  Reports coming from the country have indicated Japanese officials are planning to write off the plant rather than repair it.  Mr Grimston said it now seemed likely workers would flood the reactor building with sea water and boric acid – a good nutrient absorber.  “My reading of that is that they are going to write this plant off, because with sea water in there, that will cause corrosion, and the boric acid will be practically impossible to remove,” he said.  Japan generates around 30% of its power from about 50 nuclear plants.  (full article)