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Meltdown Likely Under Way At Japan Nuclear Reactor


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Explosion heard at Fukushima No2. reactor

Japan's Nuclear and Industrial Safety Agency says an explosion was heard early Tuesday morning at the No.2 reactor of the disaster-hit Fukushima No.1 nuclear power plant.

Agency officials told reporters that the blast was heard at 6:10 AM local time on Tuesday.

Chief Cabinet Secretary Yukio Edano earlier told a news conference that a reactor facility, called the suppression pool, has been damaged.

But agency officials said they have no detailed information yet about the report.

They said that depending on where the damage is done, either liquid or air could leak out of the suppression pool.

The suppression pool is linked to the reactor containment vessel and is designed to prevent radioactive material from leaking outside.

Experts say a breach to this crucial facility has raised the possibility of a radioactive leak.

The Nuclear and Industrial Safety Agency also said that nuclear fuel rods inside the No.2 reactor are exposed above water by about 2.7 meters. That's about half the length of the fuel rods.

Agency officials said that radiation levels around the nuclear power plant reached 965.5 microsieverts following the explosive sound.

They say the figure later dropped slightly to 882 microsieverts.

The officials said they believe the rise in radiation level is due to the breach in the suppression pool, but that they cannot say for sure. They said they are monitoring the situation closely.

The officials added that the monitored level of radiation would not immediately pose a health threat.

Tokyo Electric Power Company that operates the power station briefly evacuated workers from the facility following the sound of the blast.

Tuesday, March 15, 2011 09:26 +0900 (JST)

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This is bad, by far the worst numbers thus far in this crisis... And this number is at the plant gate...farther away from the reactors themselves.

TEPCO: 8,200 microsieverts recorded at plant

Tokyo Electric Power Company says radiation levels reached 8,217 microsieverts per hour near the front gate of the Fukushima No.1 nuclear power station at 8:31 AM Tuesday.

Anyone in this kind of environment would be exposed to more than 3 years' worth of naturally occurring radiation within a single hour.

Tuesday, March 15, 2011 09:29 +0900 (JST)

http://www3.nhk.or.j...lish/15_17.html

post-53787-0-05041500-1300151796_thumb.j

Edited by jfchandler
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This a report from earlier today...prior to the latest explosion

TEPCO: Nuclear fuel may be melting

The Tokyo Electric Power Company says there is a possibility of fuel rods melting in the Number Two reactor at its Fukushima Number One plant.

A company official said at a news conference on Tuesday that the level of cooling water is now too low to measure.

He indicated that the fuel rods may have overheated and begun melting.

Tuesday, March 15, 2011 04:27 +0900 (JST)

http://www3.nhk.or.jp/daily/english/15_06.html

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Source was mentioned in first post, NHK World.

I am still very doubtful about the radiation levels being thrown around, translators seems to regularly miss a decimal point here and there.

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BULLETIN: Container damaged, radioactive materials feared to leak at Fukushima plant

TOKYO, March 15, Kyodo News

Radiation is feared to have leaked after the container vessel was damaged at the No. 2 reactor of the Fukushima nuke plant Tuesday morning, Tokyo Electric Power Co. said.

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Blast heard at Fukushima's No.2 reactor, radiation shoots up

TOKYO, March 15, Kyodo News

Radiation is feared to have leaked after the container vessel suffered damage at the No. 2 reactor of the quake-hit Fukushima No. 1 nuclear power plant Tuesday morning, Tokyo Electric Power Co. said.

The utility also admitted that a critical situation called ''meltdown'' in which fuel rods melt and are destroyed is possible at the plant where three reactor cores are believed to have partially melted following Friday's magnitude 9.0 earthquake that hit northeastern and eastern Japan.

An explosion was heard early Tuesday morning at the reactor and the radiation level temporarily shot up later, the firm said as it continued efforts to prevent overheating of exposed fuel rods.

Shortly after the apparent blast at 6:10 a.m., which appears to have damaged the reactor's pressure-suppression system, the radiation level exceeded the legal limit to reach 965.5 micro sievert per hour before jumping to 8,217 micro sievert at 8:31 p.m., it said.

The maximum level is more than eight times the 1,000 micro sievert level to which people can be exposed in one year.

The utility said it is evacuating workers from the plant, except for those necessary for work to cool the reactor.

The reactor's fuel rods were fully exposed for around two and a half hours Monday evening after water levels rapidly fell, and again late Monday night although seawater was being injected, prompting the utility to open some steam valves at 1:10 a.m. Tuesday in order to resume pumping seawater.

The water level recovered somewhat later in the morning to cover about 1.2 meters of the fuel rods, about one-third of their height, the firm said.

Prime Minister Naoto Kan said earlier in the morning that the government and TEPCO will set up an integrated headquarters, headed by himself, to address issues at the Fukushima No. 1 plant.

With radiation levels around the facility up, TEPCO suspects the core of the No. 2 reactor has partially melted, a critical nuclear safety situation.

The development follows hydrogen blasts at both of the plant's two other reactors whose cores are also believed to have partially melted, occurring Saturday at the No. 1 reactor and Monday at the No. 3 reactor.

''A worrisome situation remains but I hope to take the lead in overcoming this crisis,'' Kan said of the nuclear power plant. ''I will take all measures so that damage will not expand.''

At the headquarters set up at the TEPCO head office, with TEPCO president and the economy, trade and industry minister serving as its deputy chiefs, Kan confronted TEPCO officials about their delay in reporting the initial blast.

Japan has asked the United States to provide more cooling equipment to help stabilize the plant, Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission, said in Washington. The NRC has already sent two technological experts and is fully supporting Japanese efforts, he said.

The No. 2 reactor automatically shut down after the magnitude 9.0 earthquake hit the region on Friday. Its reactor cooling function was lost on Monday and water levels rapidly dropped, fully exposing fuel rods for around two and a half hours from 6:30 p.m.

Seawater was injected and water levels were increased temporarily but late Monday night they started dropping, leading to full exposure of the rods again.

At 1:10 a.m. Tuesday, TEPCO opened some steam valves and resumed work to pump seawater and was considering opening more valves, according to the company.

http://english.kyodo...1/03/78021.html

Edited by jfchandler
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NHK reporting winds blowing southward from plant area at about 15 Km per hour, at least thru midday Japan time.

Radiation levels reported at about 2400 mSv about five minutes after this morning's reactor explosion and peak readings above 8000 mSv then.

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Japanese officials acknowledged that the fuel rods appear to be melting inside all three of the reactors at the Fukashima plant. "Although we cannot directly check it, it's highly likely happening," Chief Cabinet Secretary Yukio Edano told the Associated Press.

Well, one silver lining in these reports, is it will put the brakes on Thailand's (EGAT's) nuclear ambitions. I don't say it will snuff out EGAT's dreams for a nuclear Thailand, but it will dampen them. And today's Post has a feature article mentioning PM Abhisit is also against Thailand going nuclear.

All this talk about hydrogen mixing with oxygen and causing explosions. I'm not a chemist, but last time I checked, H + O = water. As for breaching the containment vessel to release pressure, why not have a tank shoot an off-center shot?

This could also put additional worry on countries, particularly in the Middle East, who have nuke plants. A plant in Iraq was bombed by Israeli jets a number of years ago. We all know that all those countries have enemies, and what better way to screw your enemy than to cause a radioactive explosion in their midst? Along with all the other manifold safety measures already required for N plants, there will be a need to add a ring of anti-aircraft and anti-missile defenses to the equation.

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Radiation levels reported at about 2400 mSv about five minutes after this morning's reactor explosion and peak readings above 8000 mSv then.

Let's change that to 2,400μSv and 8,000μSv

Radiation level reporting has been very inconsistent, but let's try to keep the units right.

Sievert (Sv), Millisievert (mSv), Microsievert (μSv)

Edit: Since your previous post gives doses in milliSievert, this is equivalent to 2.4mSv and 8mSv.

Edited by Jdietz
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So the peak readings this morning from the plant of 8000+ microSievert are, I believe, equal to 8 milliSievert... That's how they're getting the figure of that one hour exposure at that level being equal to three years worth... See comparisons below

An assortment of typical radiation doses (in milliSievert) (mSv)

Used to destroy the bone marrow in preparation for a marrow transplant (given over several days) 10,000

Approximate lethal dose ("LD50") if no treatment and given to the entire body in a short period 4,500

Causes radiation sickness (when absorbed in a short period) >1,000

Increase in lifetime dose to most heavily exposed people living near Chernobyl 430

Average annual dose (excluding natural background) for medical X-ray technicians 3.2

Maximum permissible annual dose (excluding natural background and medical exposure) to general public 1.7

Natural background, Boston, MA, USA (per year)(excluding radon) 1.02

Natural background, Denver, CO, USA (per year)(excluding radon) 1.8

Dose from a single full-body computed tomography (CT) scan 45

http://users.rcn.com.../Radiation.html

Edited by jfchandler
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