What actually happened at Fukushima?


Satellite image showing the cut out in the 35m cliffs

The earthquake and tsunami of March 2011 cut the nuclear reactors off from outside electrical power. The earthquake also triggered an automatic reactor shutdown, so no electricty was being generated by the nuclear plant. However, the reactor in shutdown mode still generates heat, and so does the spent fuel. So there were two levels of backup sources of electrical power onsite: diesel generators and batteries. Fukishima 1 and 2 are only 10kms apart, and both are on the sea shore. Fukushima 2 survived, but Fukushima 1 did not. This is because it was built into a cut out in the 35m high cliffs, creating a half bowl shape behind the plant. This was done to keep the plant design the same, and not incur extra costs. (The safer but more expensive option would have been to build the plant on higher ground, and install pumps to get the seawater up that level.)

So the tsunami went into this bowl, and instead of dispersing over the land as it did elsewhere, immediately washed back toward the sea, swamping the diesel generators. The batteries were therefore the last emergency power source available, and they lasted 8 hours, as they were designed to. Then there was no way to pump cooling water through the reactor and the spent fuel tanks, and the temperature slowly spiraled out of control. It reached the melting point of steel, melted the reactor vessel, and then became hot enough to melt its way through the concrete base. During this process, vast amounts of steam, dust and vapourised material were generated, including a large amount of radioactive caesium-137 (a soft metal which boils at 641°C), as well as traces of other radioactive material such as plutonium.

Fukushima released 170 more radiation than this

Some of this was intentionally released into the atmosphere to avoid an explosion, although eventually an explosion did happen. The superheated material released rose into the air, and was blown by the wind. Some of this rose into the jetstream and was spread all over the world, some hit mountain slopes to the Northwest, and some fell to the ground when it rained. The total amount of radiation released is far greater than Chernobyl, and is equivalent to about 170 nuclear bombs of the size used on Hiroshima in the second world war.

Unfortunately it did not stop there. Firstly the nuclear fission reaction continued inside the reactor, resulting in further releases over the following months. Secondly, during wet weather, some of the caesium on the ground was washed into gutters, stormwater drains, rivers, and dams, which concentrated the radiation in some areas, and also contaminated areas which had not been directly affected by the fallout. Thirdly, during dry weather, wind blew dust and soil into the air, again distributing radioactivity to other areas.

In Tokyo, over 200kms away, radiation levels of twice the normal background are measured regularly. One scientist I met predicted that in Tokyo Bay, radiation levels will peak about two years later, as the rivers slowly wash the caesium into the sea,

The Japanese government is claiming the nuclear disaster is ‘over’. If this was the case, it would minimise the central governments responsibility for evacuations, clean up operations, and providing alternative housing.

The reality is that it is far from over, as can be seen from the experience at Chernobyl, where less radioactive material was released. Twenty five years later, over 2000 kms from Chernobyl there are still over 200 000 sheep in the UK which are so radioactive that they are not allowed to be sold or moved. The Japanese need to face the fact that they will be living with the ongoing effects of the Fukushima nuclear disaster for generations to come.

First Europe, now Southeast Asia… how many continents will mankind contaminate with radiation before we realise nuclear power comes with unacceptable risks?

2 responses to “What actually happened at Fukushima?

  1. Pingback: Cleaning up Japan after the Fukushima Nuclear disaster | KOEBERG ALERT ALLIANCE

  2. Pingback: Radioactivity on Animals, Plants & Animals | WayCoolDogs.com

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