Watts Up With That? (Antony Watts)
Fear of Nuclear
First, a few definitions.
The energy associated with electromagnetic radiation, or more
specifically with each quantum of radiation, is proportional to its
If the frequency is high enough, and here we are talking of X-rays and
gamma rays, the associated energy will be sufficient to strip
electrons from atoms when the radiation interacts with matter.
Such radiation is known for obvious reasons as ionizing radiation.
Lower energy radiation, such as visible light and microwaves, has
insufficient energy to strip electrons and is known as non-ionizing
Stripping electrons from complex organic molecules will presumably
disrupt those molecules in some fashion, so it is reasonable to expect
biological effects from exposure to ionizing radiation.
Ionizing radiation exposure is measured in units of sieverts, named
after the Swedish medical physicist Rolf Sievert.
More specifically, the sievert is based upon the effect that ionizing
radiation will have on human bodies.
One seivert represents a very large dose, so exposure levels are
usually expressed in millisieverts (mSv).
There are two schools of thought on ionizing radiation.
The first is that the human species has evolved in a background of
ionizing radiation, and is well adapted to it.
Sources of natural background radiation include cosmic radiation,
radioactive elements in the Earth's crust, radon gas in the atmosphere,
and radioactive isotopes in our food.
The average dose we receive, on a worldwide basis, is 2.4 mSv per year,
although this can vary significantly from place to place.
Humans, according to this school of thought, are insensitive to
radiation doses of this magnitude.
Only when radiation levels are a couple of orders of magnitude or more
higher do we have any cause for concern.
The second school of thought holds that all ionizing radiation is
harmful, and that any exposure to it, down to the smallest detectable
amount, carries a risk of cancer with it.
This is the viewpoint espoused by the US National Academies' seventh
report on the biological effects of ionizing radiation, commonly
known as BEIR VII
Beir VII: Health Risks from Exposure to Low Levels of Ionizing
However, in my opinion there are some serious problems with this
report, which I shall deal with in a later essay.
Its overall finding that "the risk of cancer proceeds in a linear
fashion at lower doses without a threshold and that the smallest dose
has the potential to cause a small increase in risk to humans" is not
altogether credible, considering the evolutionary background of the
Radiation levels near Nuclear Plants
Nuclear power stations contain large amounts of radioactive material,
and it would be unrealistic to expect that there would not be at least
some detectable radiation near them.
A typical figure for the additional exposure caused by living near a
normally-operating nuclear power station is 0.02 mSv/year
Is radiation exposure from a nuclear power plant always fatal?],
which is roughly 1% of the natural background radiation dose.
Living near a nuclear power station for a year is equivalent to
living in Denver (altitude 5000 feet) for two days, or taking a
single US coast-to-coast flight, since higher altitude results in less
shielding from cosmic rays.
A study published by the Canadian Nuclear Safety Commission in 2013
concluded that there was no evidence of increased cancer rates due to
radiation effects on populations living within 25 km of Ontario's
Pickering, Darlington and Bruce nuclear power plants
Radiation and Incidence of Cancer Around Ontario Nuclear Power Plants
From 1990 to 2008 ].
The study found that while some cancer rates were higher than the
general population, others were lower, without any consistent pattern,
which is perhaps as good a definition of statistical variation as any.
While radiation levels from normally-operating nuclear plants are
negligible, what would be the result of a major accident in a
nuclear power station?
To answer this question we can look at three such accidents, at
Three Mile Island, Fukushima, and Chernobyl
Three Mile Island
In 1979 a meltdown occurred in one of the reactors at Three Mile Island
Very little radiation was released.
The average dose from the incident was less than one per cent of the
natural background radiation.
To quote the US Senate report on the accident:
"The Special Investigation ... found no persuasive evidence that
releases during the accident resulted in adverse near-term physical
health effects or will result in statistically significant
long-term physical health effects" .
A variety of epidemiology studies, e.g. , have since
concluded that the accident had no observable long term health
In March 2011 the Fukushima nuclear power station was hit by two
major natural disasters in quick succession, first a massive earthquake,
then a huge tsunami.
As a result, over the next several days three of the six reactors at
the site started overheating and went into meltdown.
While there were about 18,000 fatalities directly attributable to the
earthquake and tsunami,
there were no fatalities linked to shortterm overexposure to radiation
at Fukushima, nor are any long-term health effects expected.
The United Nations Scientific Committee on the Effects of Atomic
Radiation (UNSCEAR) published a report in 2013 on radiation effects
from the accident . The Committee found that:
• "The doses to the general public, both those incurred during
the first year and estimated for their lifetimes, are generally low
or very low.
No discernible increased incidence of radiation-related health
effects are expected among exposed members of the public or their
• "No acute health effects (i.e. acute radiation syndrome or other
deterministic effects) had been observed among the workers and the
general public that could be attributed to radiation exposure from
With regard to nuclear workers, the report goes on to say that 170
workers at the site received doses in excess of 100 mSv, averaging
about 140 mSv.
"No discernible increase in cancer in this group is expected, because
its magnitude would be small in comparison with normal statistical
Correlation of these predictions with actual long-term observed health
effects will have to wait for many years yet, since the accident
happened only a few years ago.
However, data in this respect exists with regard to the Chernobyl
accident, which is discussed below.
Over-reaction by authorities who initiated unnecessary mass
evacuations may have resulted in some deaths.
According to one report, "The psychological trauma of evacuation was a
bigger health risk for most than any likely exposure from early return
to homes" .
The Chernobyl accident in 1986 was the largest non-military
radiological event ever to have occurred.
The Soviet reactors in use at the time were designed without much
thought for safety.
The catastrophe occurred because some tests being conducted on a
reactor went out of control; descriptions of the way the operators
made ad hoc changes and overrode automatic safety features during the
tests are hair-raising .
According to a 1992 International Atomic Energy Agency report,
"The accident can be said to have flowed from a deficient safety
culture, not only at the Chernobyl plant, but throughout the Soviet
design, operating and regulatory organizations for nuclear power that
existed at that time" .
Deaths from massive radiation exposure can occur in a major nuclear
accident, but this is no different in principle from any other major
Chernobyl caused less than 50 such deaths;
for comparison, the 2009 Sayano-Shushenskaya hydroelectric accident in
Russia caused 75 deaths ,
and the Bhopal disaster caused several thousand .