Asia & Pacific

Meltdown Threat Rises at Japanese Nuclear Plant

Published March 14, 2011

| Associated Press

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SOMA, Japan (AP) -- Water levels dropped precipitously Monday inside a stricken Japanese nuclear reactor, twice leaving the uranium fuel rods completely exposed and raising the threat of a meltdown, hours after a hydrogen explosion tore through the building housing a different reactor.

Water levels were restored after the first decrease but the rods remained exposed late Monday night after the second episode, increasing the risk of the spread of radiation and the potential for an eventual meltdown.

The cascading troubles in the Fukushima Dai-ichi plant compounded the immense challenges faced by the Tokyo government, already struggling to send relief to hundreds of thousands of people along the country's quake- and tsunami-ravaged coast where at least 10,000 people are believed to have died.

Later, a top Japanese official said the fuel rods in all three of the most troubled nuclear reactors appeared to be melting.

Of all these troubles, the drop in water levels at Unit 2 had officials the most worried.

"Units 1 and 3 are at least somewhat stabilized for the time being," said Nuclear and Industrial Agency official Ryohei Shiomi "Unit 2 now requires all our effort and attention."

In some ways, the explosion at Unit 3 was not as dire as it might seem.

The blast actually lessened pressure building inside the troubled reactor, and officials said the all-important containment shell -- thick concrete armor around the reactor -- had not been damaged.

In addition, officials said radiation levels remained within legal limits, though anyone left within 12 miles of the scene was ordered to remain indoors.

"We have no evidence of harmful radiation exposure," deputy Cabinet secretary Noriyuki Shikata told reporters.

On Saturday, a similar hydrogen blast destroyed the housing around the complex's Unit 1 reactor, leaving the shell intact but resulting in the mass evacuation of more than 185,000 people from the area.

So the worst case scenario still hung over the complex, and officials were clearly struggling to keep ahead of the crisis.

Late Monday, the chief government spokesman said there were signs that the fuel rods were melting in all three reactors, all of which had lost their cooling systems in the wake of Friday's massive earthquake and tsunami

"Although we cannot directly check it, it's highly likely happening," Chief Cabinet Secretary Yukio Edano told reporters.

Some experts would consider that a partial meltdown. Others, though, reserve that term for times when nuclear fuel melts through a reactor's innermost chamber but not through the outer containment shell.

Officials held out the possibility that, too, may be happening.

"It's impossible to say whether there has or has not been damage" to the vessels, nuclear agency official Naoki Kumagai said.

If a complete reactor meltdown -- where the uranium core melts through the outer containment shell -- were to occur, a wave of radiation would be released, resulting in major, widespread health problems.

The Monday morning explosion at the Fukushima Dai-ichi plant's Unit 3 injured 11 workers and came as authorities were trying to use sea water to cool the complex's three reactors.

While four Japanese nuclear complexes were damaged in the wake of Friday's twin disasters, the Dai-ichi complex, which sits just off the Pacific coast and was badly hammered by the tsunami, has been the focus of most of the worries over Japan's deepening nuclear crisis. All three of the operational reactors at the complex now have faced severe troubles.

Operators knew the sea water flooding would cause a pressure buildup in the reactor containment vessels -- and potentially lead to an explosion -- but felt they had no choice if they wanted to avoid complete meltdowns. Eventually, hydrogen in the released steam mixed with oxygen in the atmosphere and set off the two blasts.

Official: Damaged Japan Nuclear Fuel Rods Were Fully Exposed

Published March 14, 2011

| Associated Press

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SOMA, Japan -- The second hydrogen explosion in three days rocked a Japanese nuclear plant Monday, sending a massive cloud of smoke into the air and injuring 11 workers. The blast was felt 25 miles away, but the plant's operator said the radiation levels at the affected unit were still within legal limits.

Later Monday, fuel rods at a separate reactor in the plant were fully exposed after it lost its ability to cool down, officials said. The exposure raises the risk of the unit overheating and adds to fears of a potential third explosion at the plant.

The morning blast occurred in Unit 3, which authorities have been trying to cool with sea water after a system failure in the wake of Friday's massive earthquake and tsunami, triggered an order for hundreds of people to stay indoors, said Chief Cabinet Secretary Yukio Edano. The two disasters left at least 10,000 people dead.

Operators knew the sea water flooding would cause a pressure buildup in the reactor containment vessel -- and potentially lead to an explosion -- but felt they had no choice if they wanted to avoid a complete meltdown. In the end, the hydrogen in the released steam mixed with oxygen in the atmosphere and set off the blast.

The inner containment shell surrounding the Unit 3 reactor was intact, Edano said, allaying some fears of the risk to the environment and public. But the outer building around the reactor appeared to have been devastated, with only a skeletal frame remaining.

Tokyo Electric Power Co., which operates the plant, said radiation levels at Unit 3 were well under the levels where a nuclear operator must file a report to the government.

A similar explosion occurred Saturday at the plant's Unit 1, injuring four workers, causing mass evacuations and destroying much of the outer building.

Shortly after Monday's explosion, Tokyo Electric warned it had lost the ability to cool Unit 2. Hours later, the company said fuel rods in that unit were fully exposed, at least temporarily.

The company was trying to channel sea water into the reactor to cover the rods, cool them down and prevent another explosion at the stricken plant.

More than 180,000 people have evacuated the area in recent days, and up to 160 may have been exposed to radiation -- pouring misery onto those already devastated by the twin disasters.
Japan's meteorological agency reported the prevailing wind in the area of the stricken nuclear plant was heading east -- to the Pacific.

Meltdown threat rises at Japanese nuclear plant

By ERIC TALMADGE and MARI YAMAGUCHI, Associated Press

Monday, March 14, 2011

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Residents evacuated from areas surrounding the Fukushima nuclear facilities damaged in Friday's massive earthquake, are checked for radiation contamination, Sunday, March 13, 2011, in Koriyama city, Fukushima prefecture, Japan.

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(03-14) 09:30 PDT SOMA, Japan (AP) --
Water levels dropped precipitously Monday inside a stricken Japanese nuclear reactor, twice leaving the uranium fuel rods completely exposed and raising the threat of a meltdown, hours after a hydrogen explosion tore through the building housing a different reactor.
Water levels were restored after the first decrease but the rods remained exposed late Monday night after the second episode, increasing the risk of the spread of radiation and the potential for an eventual meltdown.
The cascading troubles in the Fukushima Dai-ichi plant compounded the immense challenges faced by the Tokyo government, already struggling to send relief to hundreds of thousands of people along the country's quake- and tsunami-ravaged coast where at least 10,000 people are believed to have died.
Later, a top Japanese official said the fuel rods in all three of the most troubled nuclear reactors appeared to be melting.
Of all these troubles, the drop in water levels at Unit 2 had officials the most worried.
"Units 1 and 3 are at least somewhat stabilized for the time being," said Nuclear and Industrial Agency official Ryohei Shiomi "Unit 2 now requires all our effort and attention."
In some ways, the explosion at Unit 3 was not as dire as it might seem.
The blast actually lessened pressure building inside the troubled reactor, and officials said the all-important containment shell — thick concrete armor around the reactor — had not been damaged. In addition, officials said radiation levels remained within legal limits, though anyone left within 12 miles (20 kilometers) of the scene was ordered to remain indoors.
"We have no evidence of harmful radiation exposure," deputy Cabinet secretary Noriyuki Shikata told reporters.
On Saturday, a similar hydrogen blast destroyed the housing around the complex's Unit 1 reactor, leaving the shell intact but resulting in the mass evacuation of more than 185,000 people from the area.
So the worst case scenario still hung over the complex, and officials were clearly struggling to keep ahead of the crisis.
Late Monday, the chief government spokesman said there were signs that the fuel rods were melting in all three reactors, all of which had lost their cooling systems in the wake of Friday's massive earthquake and tsunami
"Although we cannot directly check it, it's highly likely happening," Chief Cabinet Secretary Yukio Edano told reporters.

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/n/a/2011/03/14/international/i090226D17.DTL#ixzz1Gaxz75cO

Are they telling us the truth about it just being a "hydrogen explosion"? This is the first portion of my research...
excerpt from an academic paper..
"Moving forward

A 2004 evaluation by the Japan Atomic Energy Agency (JAEA) has indicated that by 2010 it expects to confirm the safety of high-temperature reactors and establish operational technology for an IS plant to make hydrogen thermochemically. In April 2004, a coolant outlet temperature of 950°C was achieved in its High-Temperature Engineering Test Reactor (HTTR)—a world first, opening the door for direct thermochemical hydrogen production.

Meanwhile, a pilot plant test project producing hydrogen at 30 m³/hr from helium heated with 400 kW is underway to test the engineering feasibility of the IS process. After 2010, an IS plant producing 1000 m³/hr (90 kg/hr, 2t/day) of hydrogen should be linked to the HTTR to confirm the performance of an integrated production system, envisaged for the 2020s.

JAEA plans a 600 MW GTHTR300C unit for hydrogen cogeneration using a direct cycle gas turbine for electricity production and the IS process for hydrogen production, deploying the first units after 2020. This could produce hydrogen at 60,000 m³/hr (130 t/day)—"enough for about a million fuel cell vehicles" (at 1 t/day for 7700 cars).

The economics of thermochemical hydrogen production seem sound. General Atomics projects US$1.53/kg based on a 2400 MWt HTGR operating at 850°C, with 42% ovrall efficiency, and $1.42/kg at 950°C and 52% efficiency (both 10.5% discount rate). At 2003 prices, steam reforming of natural gas yields hydrogen at US$1.40/kg, and sequestration of the CO₂ would push this to $1.60/kg. Such a plant could produce 800 tonnes of hydrogen per day—"enough for 1.5 million fuel cell cars" (at 1 t/day for 1800 cars).

In the meantime, hydrogen can be produced by electrolysis of water, using electricity from any source. Non-fossil sources, including intermittent ones such as wind energy and solar energy, are important possibilities (thereby solving a problem of not being able to store the electricity from those sources). However, the greater efficiency of electrolysis at high temperatures favors a nuclear source for both heat and electricity."

Nuclear contamination: The options

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by Anne Chaon – Sun Mar 13, 3:09 pm ET

PARIS (AFP) – Evacuation, temporary shelter and iodine pills are the chief weapons for protecting civilians against nuclear fallout, experts say.

A blast on Saturday that wrecked the concrete shell surrounding the No. 1 reactor at Japan's Fukushima nuclear plant released radioactive vapour but not at levels dangerous for human health, according to Japanese officials.

Specialists say the authorities have a several-pronged strategy for shielding civilians if there is an explosive breach of the reactor, as in the April 26 1986 Chernobyl disaster.

In that event, a cloud of radioactive dust spread over parts of Ukraine and Belarus, triggering a surge in cancer and birth defects. The death toll ranges from a UN 2005 estimate of 4,000 to tens or even hundreds of thousands, proposed by non-governmental groups.

"There are three weapons against contamination -- evacuation, confinement and iodine," said Patrick Gourmelon, director of radioprotection at a French nuclear watchdog, the Institute for Radioprotection and Nuclear Safety (IRSN).

About 200,000 people have already been evacuated from residential areas around Fukushima, located 250 kilometres (120 miles) north of Tokyo.

Confinement is a highly effective tool pending evacuation to a safer area.

It consists of taking shelter in an enclosed space, preferably a basement room, whose doors and windows are then sealed tight with plastic sheets and adhesive tape.

"The point is to prevent radioactive dust from entering the lungs and the digestive tract," said Gourmelon.

"You take a good shower to remove any contact between the fallout and the skin, but you shouldn't scrub, because this helps particles to penetrate," he said. Nail-biting, smoking and sucking or licking one's fingers are also out.

In a nuclear alert, the authorities also hand out iodine pills to prevent cancers of the thyroid, which is a particular risk for babies, young children, teenagers and expectant or breast-feeding mothers.

The goal is to saturate the thyroid with "healthy iodine," shielding it from radioactive iodine, said Gourmelon.

Timing, though, is essential. Preferably, the iodine is taken an hour before a known fallout incident. Japanese guidelines say the pills should be distributed when the likely absorbed dose of radioactivity is 100 milligray, a unit named after a British physicist.

"You can also take it in the following 24 hours after the incident," he said. "It does work but the protection is reduced to 25 percent."http://news.yahoo.com/s/afp/20110313/hl_afp/japanquakenuclearhealth_20110313190935

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