What is Radiation?
The blast and heat effects of a nuclear explosion are very similar to those of
a conventional weapon, just multiplied many times in scale because a nuclear
explosion is so much more powerful than a conventional explosion. Even
the environmental effects are not qualitatively different, since extensive firebombing
of cities with conventional weapons would also push equivalent
amounts of soot into the atmosphere, potentially affecting global climate in
a similar way.
But nuclear weapons also produce short-term and long-term effects from
ionising radiation which are qualitatively different to any effect produced
by other types of weapon. These have huge importance in terms of the impact
of nuclear weapons beyond the immediate point of detonation, not only in
terms of spreading death and injury far and wide geographically, but also
spreading it across time to future generations.
The main forms of ionising radiation are alpha, beta and gamma rays,
and also neutrons. These are all produced in large quantities from a nuclear
explosion. All ionising radiations increase the chemical reactivity of the
materials they irradiate, by altering the electrical charge of (or ‘ionising’)
their atoms. In living things, these chemical effects can be very damaging.
Alpha radiation comes from helium ions (with two protons and two
neutrons) released during the decay of uranium and many of its decay products.
Alpha particles penetrate matter very poorly – a single sheet of paper can
provide effective shielding – so external exposure has very little effect on
health. But any alpha particles that are swallowed or inhaled can reach body
tissues where they can seriously damage cells in the immediate vicinity.
Beta rays are electrons formed during radioactive decay. They penetrate
more than alpha particles but are still most damaging if the radioactive
source materials are inhaled or swallowed.
The most penetrating and damaging external forms of ionising radiation
are the gamma rays. Gamma rays are a form of electromagnetic radiation.
They can behave either like waves or like particles (when they are referred
to as ‘high energy photons’). Unlike alpha particles and beta particles,
gamma rays will travel through metal, rocks and concrete. Depending on
the strength of the gamma rays, a certain thickness of any given material
will reduce the gamma rays by a certain percent. Six feet of concrete, for
instance, will reduce typical gamma rays by a factor of one billion, although
a small fraction of the rays will still get through.
When ionising radiation is absorbed by a given mass of material, the
received ‘dose’ can be measured in physical units called ‘Grays’ (Gy).1 But
the amount of biological damage varies widely according to the type of
radiation (alpha, beta or gamma), and the various organs affected, because
these all have different rates of sensitivity to radiation. A Gy of alpha rays
inside the body (for example from inhaled uranium or radon) is reckoned
to be 20 times more dangerous than the same dose of external gamma rays.
A different measurement, the ‘Sievert’ (Sv)2 is therefore used to indicate
the biological effect of a given radiation dose. One milli-Gray of gamma
rays, for instance, is ‘equivalent’ to 1 milli-Sievert, and one milli-Gray of
alpha rays is equivalent to 20 milli-Sieverts. For humans, the consequences
of most concern from even relatively low doses (below 0.1 Sv) are the
increased risks of cancer, and of inheritable changes affecting offspring.
Effects of radiation on the human body
Acute radiation poisoning can result from sudden exposure to doses of 1 Sv
or more – for example from the first flash of a nuclear detonation. The
clinical effects are predictable and depend on the dose and whether the
whole or only part of the body was exposed. As the main form of radiation
will be high-energy photons (gamma rays), shielding in the hollows of hills
(which occurred at Nagasaki) or inside buildings which remain standing
can be partially effective in reducing exposure.
All those receiving more than 8 Sv will die, and progressively higher
doses will kill more quickly. About half those exposed to 4 to 5 Sv will die
after a month or so. The symptoms are progressively of bone marrow failure
(anaemia and bleeding), severe diarrhoea and vomiting, to severe brain
damage at very high doses resulting in seizures, coma and rapid death.
Up to half the people exposed to between 1 and 2 Sv will develop
relatively mild nausea and slight headache after a few hours, lasting a day
or so; but after a week to a month their blood cell counts fall giving them
temporarily a tendency to bruise and bleed easily after mild injury, and to
get infections more readily. About five per cent may die of complications.
Doses of less than 1 Sv are likely to cause short-term hair-loss or long-term
Certain radioactive isotopes have particular effects on certain organs of
the body. Bone-marrow and lungs are particularly vulnerable to ionising
radiation, as are the reproductive organs and thyroid glands.
Strontium-90 is taken up selectively by bones as strontium is chemically
very similar to calcium. This has a half-life of 28.8 years and emits beta
particles which, being more penetrating than alpha particles, can reach the
blood-cell forming tissues of the bone marrow. A large-scale study of baby
teeth in the us in the 1960s found that children born in 1963 had 50 times
as much strontium-90 in their teeth than children born in 1950. This was
attributed to the atmospheric nuclear testing which took place during the
late ’50s and early ’60s.3
Following the Partial Test Ban Treaty of 1963, which ended most
atmospheric testing, the levels of Strontium-90 began to drop. Children
born in 1968 thus had 50 per cent less strontium-90 in their teeth than
those born in 1963. Although further studies of baby teeth have not been
conducted since, they should continue to show a steady decline in levels of
strontium-90 as it continues its radioactive decay.
What has been studied more recently is the incidence of cancer among
adults whose baby teeth had varying levels of strontium-90 in the 1960s.
Those who later died of cancer before reaching the age of 50 were found
to have had twice the level of strontium-90 in their baby teeth at an early
age as compared to those who had not died of cancer by the same age. This
suggests that the strontium-90 from nuclear fallout in the 1950s that had
found its way into children’s teeth in the 1960s had also increased their
likelihood of getting cancer by the 2010s.4
Iodine-131 (half-life eight days) gets into milk from cows grazing on
contaminated land, and represents a thyroid cancer risk to children
drinking it. Adults appear to be at much lower risk. Administering normal
(non-radioactive) iodine can provide some protection but has to be given
very early. Ironically, a standard treatment for thyroid cancer is high-dose
Caesium is chemically very similar to potassium, so its radioactive
isotope caesium-137 – half-life 30 years – is also of biological and clinical
significance. Most of it decays by beta emission but it also emits gamma rays.
It gets deposited on the soil and taken up by plants and crops, entering the
human food chain. Potassium and caesium are widely distributed through
the body and are integral minerals essential for all cells. They get washed out
of the body in a matter of days but can still cause a great deal of damage to
cells in that time.
Other radioactive isotopes produced by nuclear fission include
uranium-237, neptunian-239, sodium-24, manganese-56, silicon-31,
disarming the nuclear argument: the truth about nuclear weapons
aluminium-28 and chlorine-38. Tritium (H-3) has a half-life of 12.3 years
and is produced in very large quantities by the fusion process used in
modern nuclear weapons.
Airburst and groundburst
The bombs dropped on Hiroshima and Nagasaki were both detonated at
an altitude of about 1,500 feet above the ground. As was mentioned in the
last chapter, this is known as an ‘airburst’ and it causes the maximum death
and destruction over the widest possible area. If the bomb is left to reach
the ground (or nearly reach the ground) before exploding, more or less
half the impact goes into the ground rather than being spread out across a
If the target is a city and the aim is to cause maximum damage, the
weapon is most likely to be exploded above ground as an airburst. A large
amount of initial radiation is released by an airburst explosion, but the
amount of radioactive fallout downwind of the explosion is much less than
for a groundburst explosion, because less earth and other materials from the
ground are consumed by the nuclear fireball.
A groundburst detonation means that large quantities of earth and
whatever else happens to be on the earth (ie buildings, people, etc) are
engulfed in the nuclear fireball and become irradiated. This additional
matter creates many more radioactive particles of many more types and
these are carried up into the mushroom cloud where they are dispersed
with the wind and eventually come down as radioactive fallout.
While a nuclear strike against a city is likely to be an airburst and thus
have comparatively less radioactive fallout, a nuclear strike against a military
target such as a hardened nuclear missile silo or command bunker is likely to
be a groundburst and thus involve much higher levels of fallout.
Radiation effects from a 100 KT groundburst
Anyone within 1,500 metres of a 100 kt nuclear detonation is likely to
receive an immediate dose of radiation well in excess of 100 Sv as a result
of the ‘initial’ radiation effects of the nuclear explosion.5 This is much more
than a lethal dose of radiation but anyone that near will have been killed
already from the heat and blast of the explosion. Within a radius of 2,500
metres, the instant dose of radiation is still in excess of 3 Sv, but this then
falls off quickly to levels of 0.3 Sv at 3,000 metres. This is the initial, or
‘instant’ dose of radiation.
At distances further than 1,500 metres from the fireball, the accumulated
dose of radiation starts to have the greater effect on human health. A dose of
3 Sv in one hour may not be fatal, but over a 4-hour period, the continued
exposure to that level of radiation, even though it is rapidly diminishing in
strength, almost certainly will be fatal. A dose of 0.3 Sv at a further distance
may not be fatal, but again, if the dose is sustained over 24-hours or even
longer, it can nonetheless prove deadly.
At even further distances, there is the ‘delayed’ radiation which travels
with the wind and comes down as rain or snow at some distance from the
nuclear fireball. In the case of a groundburst explosion, the radiation from
this fallout can still be at lethal levels even hundreds of miles from the
explosion. During one of the largest nuclear tests in the Pacific, islanders
330 miles from the detonation of a 15 mt hydrogen bomb received
accumulated doses of radiation that caused birth defects, leukaemias and
other fatal cancers.6
Then there is the global radioactive fallout resulting from the smallest of
radioactive particles making their way into the upper atmosphere where
they may traverse the globe for years before coming back down to earth.
By this time, the levels of radioactivity are much lower, but alpha particles
of very long-lasting isotopes can still get into the food chain and be ingested
into the human body.
Some 26 years after the Chernobyl nuclear accident in 1986, more than
250,000 sheep in Wales and northern England, more than 1,000 miles
away from where the accident happened, were still considered unfit for
human consumption because of the levels of Caesium-137 they contained.7
Caesium-137 contamination is now a major problem in the areas of Japan
affected by the Fukishima accident in 2011.
Impact of small doses of radiation
The main risk from lower doses of radiation, which may have no immediately
apparent effects, is the delayed onset of leukaemia (especially in children and
occurring up to ten years after exposure); or of cancers (the onset of which
starts after about five years but the risks are life-long). Even very elderly
survivors have an increased risk of cancer, a prospect which may have
haunted them throughout their lives. The psychological
effects of knowingly being exposed even to relatively low doses of ionising radiation can be
profound – and are rarely taken into consideration.
While it is impossible to predict whether an individual person will get
cancer or other complications as a result of sudden exposure to a dose of
0.1 Sv, more people within a given population exposed to 0.1 Sv will get
cancer than in a similar population not exposed to 0.1 Sv. This implies that
any increase in exposure to radiation will increase the likelihood of cancer
and other diseases.
According to one study, as many as 2.4 million people could eventually
die worldwide from cancers and leukaemias as a result of the atmospheric
testing in the ’50s and ’60s – ten times as many as died from the bombs on
Hiroshima and Nagasaki themselves.8 That is a hugely controversial figure
if it is true. It would mean that the numbers killed from cancers and leukaemias
as a result of the normal radioactive discharges from civil nuclear power
stations would also be correspondingly large and create huge insurance
problems for the nuclear industry.
What we do know is that the cancer rates in Hiroshima and Nagasaki
are higher than the average for Japan as a whole even today, 70 years after
the bombs fell and long after both cities have been re-built into the thriving
cities they are today.9
Nuclear weapons are not just very large conventional weapons. They
produce effects which no other type of weapon has ever produced. It is the
ionising radiation that potentially causes the most serious and long lasting
effects of a nuclear explosion. This is especially the case if it is a groundburst
explosion aimed at a hardened military or government target.
Mild radiation poisoning destroys blood cells and damages the genetic
material in human cells. More severe forms of radiation poisoning destroy
the linings of stomach and intestines, cause internal haemorrhages, loss of
electrolyte balance, and heart failure. Death from radiation poisoning can take
from a few days to several weeks, and beyond a certain dose of radiation,
even the most modern medical treatments are unlikely to be effective.
Groundburst nuclear explosions produce large amounts of radioactive
fallout which can travel hundreds of miles downwind. The smallest radioactive
particles rise up into the upper atmosphere and are dispersed across
the entire globe. These small radioactive particles can still be fatal if they
enter the food chain and are ingested by humans.
Radioactive isotopes produced by atmospheric nuclear testing in the
Pacific in the 1950s were found in the teeth of children as far away as the
usa. There are no definitive scientific conclusions on the effects of relatively
small doses of radiation, however some medical professionals have suggested
that as many as 2.4 million worldwide will have died from leukaemia and
other cancers as a direct result of radiation from those nuclear tests.
This means that if nuclear weapons were ever used as a weapon of war,
they would not only cause cruel and unnecessary suffering to those immediately
affected by high doses of radioactivity near to, and downwind of, the
explosions. They would also, especially if used as a groundburst weapon to
target hardened command and control bunkers, cause large amounts of radioactive
materials to enter the earth’s upper atmosphere and cause leukaemias
and other cancers to people hundreds and thousands of miles away.