Japanese Researcher Says Reactor 3's Fuel Melted Twice, Dropped to Containment Vessel

From Asahi Shinbun (3:02AM JST 8/8/2011; not the literal translation):

Fumiya Tanabe, former head of the research at Japan Atomic Energy Agency, will present the result of his research on Reactor 3 at Fukushima I Nuclear Power Plant in the upcoming Atomic Energy Society of Japan's conference next month.

Tanabe thinks the fuel melted and dropped to the bottom of the Reactor Pressure Vessel of Reactor 3 by March 14's explosion; then the melted fuel stayed there, cooled by more than 300-tonnes/day water. However, the amount of water injected dropped to only 24 tonnes per day from March 21 to 23, and 69 tonnes per day on March 24, probably due to increased pressure within the RPV.

It caused the melted fuel to heat up again, and the fuel melted through the RPV and dropped onto the Containment Vessel (pedestal; see the diagram from Asahi).

According to Tanabe, the amount of water from March 21 to 24 was only about 11 to 32% of what was needed to remove the decay heat, and within one day the melted fuel would attain the melting temperature again.

Tanabe thinks this massive "re-melting" caused the release of a large amount of radioactive materials into the environment which caused a spike in air radiation in wide areas of Tohoku and Kanto including Tokyo, and most of the re-melted fuel dropped from the RPV to the Containment Vessel.

The article doesn't say what Tanabe thinks has happened to the melted fuel that dropped onto the Containment Vessel since.

But the article does say this:

東電は原子炉圧力容器底部の温度が低下した状態（冷温停止）を事故収束の目標としているが、炉心の大半が溶けて格納容器に落下しているなら、収束に向けた工程表に影響する可能性もある

TEPCO hopes to have a "cold shutdown" where the temperature at the bottom of the RPV is low [below 100 degrees Celsius] as the target for winding down the nuclear accident. But if the fuel core is mostly melted and has dropped down to the Containment Vessel, it may affect the "roadmap".

No kidding. Yes it may. Where have you been, Asahi, for all these months? Is this news to you?

Tanabe's chart (from Asahi article) plotting the air radiation level (in microsieverts/hour) shows a spike on March 21. It rained that day in Tokyo.

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Melt-Through Simulation Created by Japan's METI Well Before #Fukushima

This animation was created by the Japan Nuclear Energy Safety Organization, a government corporation under the Ministry of Economy, Trade and Industry (which regulates the nuclear industry), to train Senior Specialists for Nuclear Emergency Preparedness on the severe accident of loss of cooling, using a Mark-1 Boiling Water Reactor.

It was created before the Fukushima I Nuke Plant accident, though there is no information as to when it was created. (The Japan Nuclear Energy Safety Organization itself was created in 2003.)

The accident sequence in the animation:

1. Control rods are inserted, and the reactor stops.

2. A big pipe connected to the Reactor Pressure Vessel breaks, and all methods of cooling the reactor fails.

3. Water starts to leak. Water level in the RPV gets low, exposing the fuel core.

That's exactly what happened at Fukushima I Nuclear Power Plant.

They must have known all along that it was not even a meltdown but melt-through.

Core melts 30 minutes after the loss of coolant accident.

Corium drops to the bottom of the RPV after 1 hour of loss of coolant.

Corium melts through the 15-centimeter RPV bottom after 3 hours, drops to the concrete floor of the pedestal that supports the RPV.

Corium melts through the concrete floor of the pedestal and drops to the floor of the Containment Vessel.

Gas is generated by the corium melting the concrete, and the gas fills the Containment Vessel raising the pressure and the temperature.

Gas starts to leak at the franges of the Containment Vessel and fill the reactor building, necessitating the venting.

The animation has this reassuring message at the end:

"Even if it gets to the worst case scenario (that you've just seen), we are trying our best to learn and upgrade our skills in dealing with nuclear emergencies by training the nuclear emergency specialists, so that the residents near the nuclear power plants can feel safe and secure."

A Senior Specialists for Nuclear Emergency Preparedness is a METI (NISA) official stationed full-time in the area where a nuclear power plant is located.

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#Fukushima I Nuke Plant Reactor 3 Bldg Has Over 6,400 Tons of Contaminated Water

What a surprise.

Workers braved the high radiation (up to 100 millisievert/hour) in the Reactor 3 reactor building on June 9 and found water in the basement. TEPCO says it expected to find water there, but didn't bother to tell us until the water was actually found.

Have I seen this before? Yes, the Reactor 1.

To state the obvious, if there's water in the basement of the reactor building, that means 1) the Reactor Pressure Vessel (RPV) is broken; 2) the Containment Vessel is broken.

The only question is: Where's the corium?

From Asahi Shinbun (10:45PM JST 6/10/2011):

東京電力は１０日、福島第一原発３号機の原子炉建屋地下でたまり水を確認したと発表した。東電は原子炉を冷却する注水量などから、５月末現在で６４００トンの水がたまっていると推計していたが、実際に存在が確認された。

TEPCO announced on June 10 that they confirmed the presence of water in the basement of the Reactor 3 reactor building at Fukushima I Nuclear Power Plant. TEPCO had estimated that 6,400 tons of water would be in the basement as of the end of May, based on the amount of water injected into the RPV. Now its existence has been confirmed.

　東電によると、９日に作業員が原子炉建屋内に入り、１階から地下に行く階段を下りて、水がたまっているのを確認した。地下の床から５．８メートルのところまで水が来ていたという。量は東電の推計よりやや多い模様。水の近くの放射線量は毎時５１ミリシーベルトだった。

According to TEPCO, workers entered the reactor building and descended the stairs from the 1st floor to the basement, and saw the water. Depth of the water was 5.8 meters [19 feet] from the basement floor, and the amount of water looked to be slightly more than TEPCO's estimate. The radiation level near the surface of the water was 51 millisieverts/hour.

　１号機同様、炉心溶融によって原子炉圧力容器が破損し、水が外に漏れ出している可能性があるという。近く、水を採取して放射性物質を調べる。

According to TEPCO, it is possible that the RPV has been damaged by the core meltdown, leaking the water. TEPCO plans to test the water for radioactive materials.

　１階を確認したところ、計器盤の扉がゆがんだり、はしごが上層階から落下したりしていた。また、機器の一部がすすのようなもので黒くなっていた。東電によると、水素爆発の影響とみられるという。

Survey of the 1st floor found distorted doors of the instrument panel and a ladder dropped from the floor above. Part of the equipment was blackened with what looked like soot. TEPCO thinks they were caused by the hydrogen explosion.

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#Fukushima I Nuke Accident: Japanese Government Admits "Melt-Through" in Reactors 1, 2 and 3

It's so predictable how these politicians and bureaucrats behave: like they have behaved ever since the start of the accident.

Yomiuri Shinbun (original in Japanese; 6/7/2011) reports that the Japanese government will now admit in the report to IAEA that the "melt-through" may have taken place in the Reactors 1, 2 and 3 at Fukushima I Nuke Plant.

According to Yomiuri, "melt-through" happens when the melted fuel leaked from the Reactor Pressure Vessel and deposits at the bottom of the Containment Vessel, and is considered worse than "melt down".

Well, "fear-mongering" and "sensational" US Representative Ed Markey, D-Mass. was right then. He said back on April 6 that he'd received information that part of the reactor core had probably melted through the Reactor Pressure Vessel at the Reactor 2 at Fukushima. And the NRC said they didn't know for sure. Uh huh.

By the time the report is submitted and discussed at the IAEA, they will be talking about the corium out of the Containment Vessel, eating away the foundation.

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