Tuesday, March 3, 2015

Bryan Leyland: “Things you know that ain't so” - nuclear radiation

As the American humorist Will Rogers said: “It’s not what we don’t know that gives us trouble, it’s what we know that ain’t so.” 

Low levels of nuclear radiation are dangerous.

Explanatory note: The normal background level of radiation is 2.4 mSv (millisieverts) per year. A single X-ray is about 1 mSv and radiation treatment for cancer exposes surrounding healthy tissue to several thousand mSv.

There is a widely held belief that nuclear radiation is dangerous, no matter how small the dose. The grounds for this are the “The linear no-threshold hypothesis” that says that all levels of radiation are dangerous and if the radiation level doubles, so does the risk. This hypothesis is used as the basis for estimating the risk of cancer from low levels of radiation from nuclear power stations. It was dreamed up in the 1950s when nuclear testing was in full swing because it supported the arguments of those who opposed atmospheric nuclear tests. But it has never been tested against the evidence.

Since then evidence that low levels of radiation are not dangerous has been gathered from the survival rates of people who were exposed but not killed at Hiroshima, from the survival rates of people exposed at Chernobyl and the fact that, in Ramsar in Iran the population has been exposed to natural levels of radiation that, according to the hypothesis, should have caused increased lung cancer. Yet they have been living there for hundreds of years and there is no indication of any harmful effect.

Research on the survival of Hiroshima victims beyond 1950 has revealed that radiation levels need to be about 100 times greater than the normal yearly background level before there is a measurable increased risk. Beyond that it rises steeply and there is a significant risk of additional cancer deaths at 1000 times the normal yearly background level.

The Chernobyl nuclear accident was well researched and provides even better data that shows that levels less than about 100 times background radiation (~240 mSv) cause no measurable harm. The risk of harm increases slowly up to about 1000 times natural radiation and much faster after that. At about 3000 times natural radiation most people will die.

People are generally terrified of low levels of nuclear radiation but, if cancer is detected, most willingly accept levels of radiation that can be as high as 30,000 years of background radiation. The radiation is aimed at the tumour but the nearby healthy tissue survives in spite of being exposed to 10,000 times background radiation.

At Fukushima the United Nations Committee on the Effects of Nuclear Radiation has stated that nobody has, or will, die of radiation from the accident. But thousands of people died as result of forced evacuations from regions with safe levels of radiation and from heat exhaustion in Tokyo as a result of the power cuts that followed closing down of other undamaged nuclear reactors.

For further reading I suggest Prof Wade Allison’s website radiationandreason.com. He is an expert in radiation physics (he reviewed and edited this article) and believes that the safety level for radiation exposure should be increased by as much as a factor of a thousand. If this was done the fear of nuclear power would be much reduced and there would be a substantial reduction in cost. Also, one would hope, the strident opposition to using nuclear radiation against Campylobacter and insects in imported fruit and vegetables would end thus sparing many people of acute illness and reducing the chance of the arrival of unwanted insects.

1 comment:

Anonymous said...
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Yet still the melon-heads resist the cheap, clean generation of electricity by nuclear power. They'd far rather the inhabitants of this earth reverted to primitive cave-dwellers. They think that the human race is a blot on the earth's surface.
Aunty Podes

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