Potential Energy

I’ve been looking into the effects of radiation on the human body and have found that radiation is measured in three different ways- the becquerel, the gray and the sievert.

The Becquerel measures how much activity there is in a quantity of radioactive material. A measurement of one becquerel means that in a particular quantitity of material one nucleus is decaying per second.

The Gray measures the physical effects of radiation or how much energy is absorbed per unit mass of matter. One gray is equal to one joule of energy deposited in one kilogram of matter.

The Sievert measures the amount of damage radiation does to biological tissue. As one gray of different types of radiation can have more or less effect on the human body, the sievert is used as a ‘dose equivalent’.

It’s taken me a while to get my head around all of this and even longer to try and figure out how to explain it, until I thought about the differences between punches delivered by either Kylie Minogue or Mike Tyson.

So the becquerel would be equivalent to the number of punches being thrown. The gray would be the amount of energy that has been delivered by those punches. And the sievert would be the damage caused by those punches.

The number of times Kylie or Tyson punched you (the becquerel) could be equal but that number doesn’t explain how hard either of them hit your or whether or not those punches did any actual damage.

You can easily imagine that the difference between the energy delivered in a punch from Kylie compared to a punch from Tyson (the gray) will be very different. But it doesn’t tell you anything about the difference between damage caused by 100 little Kylie punches directly to your lip and one Tyson punch to your stomach.

One Tyson punch to the stomach may send you flying and make you lose your breath, whereas 100 Kylie punches to your lip may actually split your lip and cause you to need stitches. The sievert in this case, very, very basically, measures the likelihood of damage being caused by a particular ‘punch’ taking into account the number of ‘punches’, the energy delivered in each ‘punch’ and the area of the body that ‘punch’ is being delivered.

To get an idea of what a sievert means I will give some examples of the sievert measurement and the likely damage caused.

A dose of more than 80 sieverts (Sv) or 80,000 millisieverts (mSv) is expected to cause immediate death.

50- 80 sieverts (50,000-80,000 millisieverts) death happens after a few hours.

10-50 Sv (10,000-80,000 mSv) causes acute radiation poisoning and is likely to cause within 7 days. The highest radiation dose at Chernobyl was 20,000 millisieverts which caused the deaths of 28
people within the first four months after the accident and 19 subsequently.

6-10 Sv (6,000-10,000 mSv) causes acute radiation poisoning and death is expected to happen within 14 days.

4-6 Sv (4,000-6,000 mSv) causes acute radiation poisoning with 60% fatality after 30 days.

3-4 Sv (3,000-4,000 mSv) causes severe radiation poisoning with 50% fatality after 30 days.

2-3 Sv (2,000-3,000 mSv) causes severe radiation poisoning with 35% fatality after 30 days. Nausea and vomiting is common. 50% chance of losing all of your hair with a 3 Sv dose. General illness and fatigue is very likely. Recovery can take up to several months.

1-2 Sv (1,000-2,000 mSv) causes light radiation poisoning. 50% chance of mild or moderate nausea, general illness and fatigue and with a 2 Sv dose.

0.5-1 Sv (500-1000 mSv) causes mild radiation sickness. Headache and increased risk of infection due to the disruption of the immune system.

0.2-0.5 Sv (200-500 mSv) causes no noticeable effects. Red blood cell count my temporarily decrease.

0.05-0.2 Sv (50-200 mSv) causes no symptoms.

The average annual radiation dose in the UK is 0.0027 Sv (2.7 mSv). 84% of that or 0.00216 Sv (2.16 mSv) is naturally occurring radiation from radon, cosmic rays, gamma radiation from buildings or even our food. Of the rest, 15% of the average annual total radiation dose, or 0.000405 Sv (0.405 mSv), is medical in origin. 99% of our radiation comes from natural or medical sources. The remainder of the artificial sources of radiation, 0.000027 Sv (0.002 mSv) comes from occupational exposure, discharges (from nuclear, phosphate, oil and gas industries) consumer products and nuclear fallout from nuclear testing. You get half that radiation dose on a flight from the UK to Spain.

A dose of 1 mSv of radiation is, according to DEFRA, the Department for Environment, Food and Rural Affairs, “equivalent to an average risk of about 1 in 20,000 of fatal cancer. Cancer from all causes accounts for about 1 in 4 deaths in the UK.”

Finally, I will point out that if you live in Cornwall, your average annual dose of radiation from all sources is a bit higher than average. It’s 0.008 Sv or 8 mSv per year due to the higher naturally occurring radon levels.

So, once and for all, can we all agree that the radiation risks posed to us from the nuclear industry are completely and absolutely minimal? If anyone is interested, however, I’m thinking of starting a campaign to have Cornwall shut down because of its obvious danger to public health…