NE Japan Earthquake Day 64: Meltdown: Water Leaks from a Cavity in Reactor 1’s Pressurized Container

NE Japan Earthquake Day 64: Meltdown: Water Leaks from a Cavity in Reactor 1’s Pressurized Container
Yomiuri Shimbun: 1号機は「メルトダウン」…底部の穴から漏水
Staff Report, May 13, 2011

On the 12th, Tokyo Power announced that most of the nuclear fuel inside Fukushima I Reactor No. 1 has melted, and the fuel’s high heat has damaged the bottom of the pressurized container; hence water is leaking out of the bottom of the container through a cavity that is several centimeters wide.

The melted fuel is thought to be gathering in the bottom of the container, and Tokyo Power confirmed that this situation is a “nuclear meltdown.”

Until now, Tokyo Power had only said that there was some fuel-related damage.

Tokyo Power says the possibility of causing further damage while trying to stabilize the temperature in the pressurized container at 100-120°C is low, but the possibility of water leaking from the next safety barrier, the outer container, is high, and if that container is filled with a “water crown” or “water casket,” then the disaster will become even more difficult to manage.

Junchi Matsumoto, acting head of the company’s Nuclear Power & Plant Siting Division, announced in the press conference that “the fuel is volatile, and the bottom of the pressurized container has been breached” and confirmed a meltdown.

According to Tokyo Power, in order to cool the fuel, eight tons of water are being pumped into the pressurized container per hour. Over 10,000 cubic meters of water have already been pumped inside, but according to a test on the 10th, the standing cold water level inside the container is at most 4 meters high. The company determined from the quantity of water leaked that there must be a hole centimeters wide in the container.

Fukushima Reactor 1 Meltdown

The State of Fukushima I Reactor No. 1
The blue dotted line was the expected water level.
The red line is the actual water level.
The outer gray shape is the outer container of the reactor, and the inner gray shape is the pressurized container.
The horizontal blue arrow is water being pumped into the reactor.
The pink lines are fuel rods.
The green lines are control rods.
The gray horizontal line above the red line is a support layer.
It’s possible that melted nuclear fuel is accumulating at the bottom of the tank.
Water is leaking through the cavity and the gaps in the welding into the outer container.

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