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

eye cataracts.


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

wider area.


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.