Tuesday, 15 March 2011

A Note on the Earthquake in Japan

I have been stunned and horrified to read of the devastation in Japan.

The tragic loss of life, and the destruction wrought is mind-bendingly awful.

Among the worst casualties is the truth.

Facts that I think we can all agree on:

1. Japan has nuclear power stations
2. These power plants were designed and built to withstand a massive earthquake.
3. The intensity of the earthquake that struck was greater than the design parameters.
4. The tsunami that followed the quake did additional damage, including to the disaster support facilities at the affected power stations.
5. Despite the magnitude of  the quake exceeding design parameters, there was little damage to the actual reactor vessels and containment systems due to the quake itself. This points to good design and good implementation.

I have read reports about the nuclear situation that range from "no radiation leakage" through "low level radiation released as part of pressure control" to "fuel rods exposed, we are all going to die!".

I just wish that there was a big red button on a device somewhere that would permanently disassociate the phrases "spectre of doom" and "nuclear power industry" in the human mind.

Please note that I am NOT saying that there is no reason for concern, but I do wish that I didn't have to filter out the "ZOMG!! We are all DOOOOOOMED!" from the news reports before I get to the truth.

From what I can glean (after said filtering),  it appears that there has been some radiation leakage - mostly attributed to steam released to reduce pressure in the reactor vessel, although there is speculation that the hydrogen explosions may have damaged the outer containment vessels.

As of this morning reports have said "the radiation levels are at 30 millisieverts between the No.2 and the No.3 reactors, 400 millisieverts near No.3 and 100 millisieverts near No.4". (cf. http://www.smh.com.au/environment/stay-indoors-japanese-pms-order-to-residents-beyond-nuclear-reactor--evacuation-zone-after-blast-20110315-1busf.html ). The guys that went in and measured that must be either braver than me, or somewhat more foolish.

BUT ... A sievert is a "dose equivalent" measure - it takes into account the varying effects of different radiation types with a "quality" factor to arrive at a number that can be used to compare different TOTAL EXPOSURES.  That means that any meaningful measure of radiation intensity using sieverts MUST include a time - for example 1 mSv per HOUR, is a MUCH higher intensity than 1 mSV per YEAR.

So, those figures above are useless.  Why do the press DO this?

A single dose of 1000 millisieverts - or one sievert - causes temporary radiation sickness such as nausea and vomiting. A dose of 5000 millisieverts would kill about half of those receiving it within a month (somewhat similar to LD50 in drug dosages this is called the LD50/30).

For reference, the worldwide average background dose for a human being is about 2.4 millisievert (mSv) per year. (cf http://en.wikipedia.org/wiki/Background_radiation). If you live in a brick house, or have a basement, your dosage will be higher.

I really wish the press would do their job: stop the editorialising and provide us with information.

Most of us can work out whether we need to be frightened all on our own.

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