Just how Safe are Fossil Fuels, Wind, Solar and Nuclear Power?

This article I'm going to compare safety for different form of electric generation.  Lets start with the energy deathprints.

Energy’s Deathprint

Energy's deathprint is a rarely talked about measure of the number of deaths per unit of energy produced for different power sources.  Here are the results from two studies on it.

From page 168 Sustainable energy without the hot air

As you can see coal, oil and biomass are particularly bad.  This is because of small particles released while burning thing (i.e. ash or fly ash).   These don't agree with people very much.  Not only do these particles cause deaths, but they also cause other health problems.  Some countries do a better job of filtering them out then others.  With a bit of searching you can find info for a variety of similar studies.   Here is another one.  I thought this review of it was particularly insightful. 

Carbon Footprints

Global Warming is a serious issue.  One study projects that...

Worldwide, upward of 20,000 air-pollution-related deaths per year per degree Celsius may be due to this greenhouse gas.

That's rather extrema considering how long the temperature changes are projected to last.  Here is a graph that shows the carbon footprint for various forms of electric generation. 

From Carbon footprint of electricity generation by Stephanie Baldwin

 The units for the graph are gCO^2eq /kwh.

From page 8 of Carbon footprint of electric generation.  I suggest reading the whole PDF.  It's not very long, and definitely worth it. 

Ranges in each electricity generation technology are due to

1. Differences between individual plants – some older and/or less efficient
    
2. Different technologies – e.g. run-of-river vs. reservoir storage
    
3. Different LCA input (boundary definition) parameters
    
4. Different studies – some studies older, so had older data (2000 was cutoff date)

In regards to the difference for nuclear power.  From page 18 of Carbon footprint of electric generation.

 Issues: 

1. Nuclear also has a very small carbon footprint 
2. Most CO 2 emitted during uranium mining (40% of life cycle CO2) 
3. Global uranium reserves – lower grades may cause footprint to rise in future 
4. 3 studies: AEA ( to 6.8g), Öko ( to 30-60g), Storm van Leeuwin ( 60 to 120g)

I would like to add to this that there are two important issues for understand nuclear power's carbon footprint.  One is the method of fuel enrichment.  Some have a bigger carbon footprint than others.  The other is the type of reactor.  Some reactors are able to use much more of the natural uranium mined then other which reduces their carbon footprint.  I'm really hopping we will start making more breeder reactors so we can use all of it. 

Radioisotopes Released into the Environment

I'll just give a brief description for coal, natural gas and nuclear power that will hopefully give you some idea about the radioisotopes (i.e. the stuff that produces radiation) they release into the environment.   For your information sometimes when people in the news talk about radiation they are talking about radioisotopes and sometimes they are talking about ionizing radiation.  If you’re not familiar with these concepts you may wish to read my post Some Basic Information Useful for Understanding Nuclear Power Safety.

Radioisotopes and fossil fuels 

There are radioisotopes mixed into almost everything.  This includes fossil fuels.  When you burn the fossil fuels these radioisotopes become more concentrated (in the ash) then they are in the natural environment.   This can result in people having more radiation exposure then they would otherwise. 

Radioisotopes Released by Coal

The main radiation release from coal  is in the form of fly ash.  In order to give you some idea about what this entails let me start out with a few quotes.

From the USGS -  Radioactive Elements in Coal and Fly Ash: Abundance, Forms, and Environmental Significance

Introduction
Coal is largely composed of organic matter, but it is the inorganic matter in coal—minerals and trace elements— that have been cited as possible causes of health, environmental, and technological problems associated with the use of coal. Some trace elements in coal are naturally radioactive. These radioactive elements include uranium (U), thorium (Th), and their numerous decay products, including radium (Ra) and radon (Rn). Although these elements are less chemically toxic than other coal constituents such as arsenic, selenium, or mercury, questions have been raised concerning possible risk from radiation. In order to accurately address these questions and to predict the mobility of radioactive elements during the coal fuel-cycle, it is important to determine the concentration, distribution, and form of radioactive elements in coal and fly ash.

Emphasis Added

10-30 ppm uranium in fly ash

10-30 ppm thorium in fly ash

From the EPA - Coal Fly Ash, Bottom Ash and Boiler Slag

In 2012, 59 percent of the coal consumed by electric utilities and independent power producers in the United States resulted in the generation of about 68 million tons of fly ash, bottom ash and boiler slag. An additional 42 million tons of other residuals were generated from flue gas desulfurization and fluidized bed combustion.

Fly ash is carried up with hot flue gases and trapped by stack filters. It is the largest of the coal combustion residuals (about half) by weight.

Stack filtration devices, such as electrostatic precipitators, baghouses and scrubbers are routinely used to reduce the emission of fly ash. They are about 99 percent effective. Only about one percent is released into the air.

Emphasis Added 

Now lets do a little math with these numbers.

68,000,000 tons * 50%  * 1% = 340,000 tons

So, in 2012, 59 percent of the coal consumed by electric utilities resulted in 340,000 tons of fly ash being released into the air.

((340,000 tons * 10ppm) / 1,000,000) * 2,000 lb./tons = 6,800 pounds*

((340,000 tons * 30 ppm) / 1,000,000) * 2,000 lb./ton = 20,400 pounds*

*assuming tons is short tons and ppm is a mass fraction.

Extrapolating for the other 41% we get...

6,800 lb / .59 ≃ 12,000 pounds
20,400 lb / .59 ≃ 35,000 pounds

So in 2012, we had roughly between 12,000 and 35,000 pounds of radioactive uranium and roughly between 12,000 and 35,000 pounds of radioactive Thorium being released into the air by  electric utilities resulted. If it wasn’t for the consumption of coal in production electricity this Thorium and Uranium would have remained under ground where it couldn’t possibly hurt anyone. Instead it was released into the air in the form of small particles which often end up the the lungs of people and animals.

Now lets talk about Radon 

Radon is a colourless odorless gas that is responsible for a large part of people's yearly radiation dose from natural sources.  So let try and figure out how much radon is release from a years worth of coal.

In the Us 858,000,000 Short tons of coal a burnt each year.  There is around 1 to 3 parts per million uranium in Us coal.   So there is between 858 and 2574 tons of uranium in a years worth of coal.  

Assuming that the amount of uranium has stayed basically constant over the years, that none of the decay chain products have left the coal and that the decay products move through the chain at roughly the same speed (all fairly safe assumption to make), then the Radon produced each year by the coal equals the uranium 238 that decays each year.

So between...

  (9,600 Gd/sec   X  3.15569e7 sec. / 6.02214129×10²³) X 222 ≃ .11Grams
   decays a sec         in a year                 1 Mole                   mass Rn-222


  (29,000 Gd/sec  X  3.15569e7 sec. / 6.02214129×10²³ ) X 222 ≃ .23 Grams
     decays a sec       in  a year                  1 Mole                   mass Rn-222


So a years worth of coal in America creates around .11 to .23 grams or 590 to 1,800 TBq of radioactive gas. Of course this says nothing about where it's released, and it also says nothing about the addition Rn-222 that it will continue to released from the coal ash ponds for years to come.

So should we all panic and run for the hills? 

Probably not.

According to the first source.

The radiation hazard from airborne emissions of coal-fired power plants was evaluated in a series of studies conducted from 1975–1985. These studies concluded that the maximum radiation dose to an individual living within 1 km of a modern power plant is equivalent to a minor, perhaps 1 to 5 percent.

 From a more recent study.

McBride and his co-authors estimated that individuals living near coal-fired installations are exposed to a maximum of 1.9 millirems of fly ash radiation yearly. To put these numbers in perspective, the average person encounters 360 millirems of annual "background radiation" from natural and man-made sources, including substances in Earth's crust, cosmic rays, residue from nuclear tests and smoke detectors.

There are a lot of radioisotopes in the coal all the Us burns each year, but not all of it ever reaches the public (Most fly ash is captured and stored),  Radon-222 has a half life of only 3.8 days so it's unlikely to get to far plus it will quickly be diluted in as it spreads out from the plant and also the radio isotopes in coal aren't that concentrated to begin with although burning it makes them  somewhat more so. 

Radioisotopes Released by Natural Gas

I know what you're thinking.  They couldn't possible pump radioactive gas into our homes right?  Well...

It has been known for over 40 years that radon, a radioactive gas, is present in natural gas. Reports by R.H. Johnson 7 and C.V. Gogolak 8 calculate the health effects due to burning natural gas in kitchen stoves and space heaters. In an US Environmental Protection Agency report, Raymond Johnson calculate s the number of lung cancer deaths due to inhalation of radon in homes throughout the U.S. as 95 due to radon concentrations in the pipeline of 37 pCi/L.

Yikes. By the way that quote came from this study that estimates the problem is much worse in New York because of gas from the Marcellus shale.  It estimates that the gas from the Marcellus shale raises the death toll by 1,182 to 30,448 a year.  That is a significant number.  Here is a blog post contesting that study. Unfortunately neither the study or the blog post that contests it have actual measurements from the Marcellus shale well heads.  Something you would think someone would want to take.

While this all sounds scary it should be noted that there is controversy in regards to the effect of low level radiation. 

Radioisotopes Released by Nuclear Power

Here is an awesome graphic that explains it all.

Source http://xkcd.com/radiation/

Conclusion

There isn't one really.  I hope learned something and you enjoyed it.

I'm Going to go Tour Diablo Canyon Nuclear Power Plant Tomorrow

I'm going to go tour Diablo Canyon nuclear power plant tomorrow.   Looking up things about nuclear power I found out tours are available, and I thought it would be kind of cool to see a nuclear power plant with my own eyes.   When I get back I'll edit this post adding how it went... 

I had a lot of  fun. I got there a little early.  Waited about 20 minutes until it opened.  I started of at a visitor center called the  PG&E Energy Education Center.  I started by looking around at the exhibits.  Here is a replica fuel assembly that I thought was neat.

Unfortunately I'm not so great a photography.  After I looked around a little they had a lecture.  Most of it stuff I already know, but one interesting fact is that Fukushima was only 20 feet above sea level, while Diablo Canyon is 85 feet above sea level.  Quit the difference.  The lecture left me with a nifty souvenir.

Its a plastic replica fuel pellet.   On it is written that it is the equivalent of 149 gallons of oil, one ton of coal or 17,000 cubic feet of natural gas.  Rather nicely done I thought.

After that we drove to the plant.  They didn't let me take any pictures inside the plant, but I was allowed to take this one outside it.

Security was really tight.  I didn't know nuclear power plants had so much security.  Inside the plant was fairly normal looking for the most part.  I got the see the turbine rooms which was really impressive.  It was amazing to sit there and think about how much power is flowing through such a small area.  I also got to look into the control room through a small window in the door.  The dry cask waste storage was a lot smaller then I thought it would be.  I was impressed by the number of things they changed in response to Fukushima.

 Over all I would have to say I was very happy with the tour, and impressed by the whole operation. Also, it's nice to now be able say I've seen a nuclear power plant with my own eyes. 

Comment Donation Bank

A comment donation bank would be a website where people donate their comments with the understanding that other people will copy and past them various places on the Internet.

This is an idea I've been thinking about for a while.  There is a lot of work involved in responding to the repeated bad ideas put forth by people who choose to remain ignorant.  This website would exist to help reduce that work of fighting those bad ideas and misinformation by allowing people to keep repeating the same responses every time. 

How I picture it working

Anyone will be able to make comment pages.  Comment pages will have tags attached to them which help organize them.  Tags will be for what the comment can be used to respond to.  Some possible tags might be for things like nuclear waste, and nuclear proliferation threats, or responses to individual papers and websites.  People can make their own tags or use tags that other people made.  Comment pages will have their own comment section, a way to flag inappropriate or inaccurate comments, and a way to rate the usefulness of the comments to give feedback about how effective individual comments are in practice.   

Why I'm not Worried about Nuclear Power

Growing up in California left me with a negative impression of nuclear power without any real knowledge of it.  I remember being scared of it as a child. Especially the nuclear waste.  I used to think they should shoot it all into space.  Now such an idea seems ridiculous to me.  I can't imagine why you would need to go so far when the problem is easily manageable here on earth.   Nuclear power has moved way far down on the list of things to be afraid of.   With this article I'd like to explain why.

I'd just like to start by saying that radiation can be harmful. Everyone seems to agree with that.  What people can't always agree about is the finer details such as if harm was done, how much harm was done and how much harm could be done by any particular event or potential event.

Also, if you don't have a basic understand of radiation and radioisotopes you may wish to read this first.   

So, you may be wondering why I'm not particularly worried about nuclear power given that radiation can be harmful.  Well for starters radiation is all around us, and it always has been.

Radiation is all Around Us, and Always has Been

Radiation is constantly bombarding us from space.  It's in the oceans, the soil and the food we eat.  It's even in the air we breath.  It's a bit harder to be afraid of it when you realize it's all around us, and always has been.  The first ape that walked on two legs was being bombarded by radiation.  The first animal that crawled up out of the sea was being bombarded by radiation.  Even when the first cells came about and life as we know it began there was radiation everywhere. 

In fact even fission was happening on earth before humanity was a thing.  In the Oklo uranium deposit (located in the country of Gabon in equatorial Africa) it was discovered that a nuclear chain reaction caused by natural processes took place millions of years ago. Here is a time line.

The history of the Oklo fossil reactors spans almost the entire history of the earth. ‘Oklotime’ can be divided into four stages:

1. U mobilization phase: Commenced ~3500 million years ago.
2. U ore/reactor formation: Started ~2800 million years ago.
3. Reactor operation: Commenced 2000 million years ago (for about a million years).
4. Waste movement: The last 2000 million years.

Yet despite this nuclear reaction happening on earth uncontrolled by man, and unreported on by an media outlets, life on earth survived.  In fact there is not evidence that it was hampered in any way.  If that isn't enough for you there is something called spontaneous fission where heavy atoms undergo fission well... spontaneously.   Also, there a certain number of neutrons (around 14 neutrons/cm²/hour) constantly bombarding the earth as a result of  cosmic ray spallation.  When these neutrons encounter uranium they can induce fission just like in a nuclear reactor, but despite these two thing releasing small amounts of fission products directly into the environment since the earth began life goes on undeterred. 

Learning more About Science has Made me Less Afraid

I find learning more about science is a fun and rewarding activity.  Which is why it shocks me when I encounter articles like this one and realize that some people know almost nothing about science at all. 

All radioactivity is man-made (True/False)

Percent that got it right

It amazes me how many people don't even know about natural sources of radiation.  I'm not a scientist, I'm never going to be a scientist, but I've found certain basic information about science incredibly useful for understanding the world around me.  Without it I'm not sure how I would judge the endless barrage of claims that I encounter every day.  Let me share with you some of the things I've learned about science that have made me less afraid.

Half Lives

Half-life: Introduction to half-life

Half lives describes how long until half of any given type of radioisotope has decayed into something else.  This is important because it's during the decaying part where the radiation gets produced.   In terms of safety there are good and bad things about any half life length.  For example things with short half lives are more dangerous because they produce more radiation, but because they have short half lives they don't stick around as long which is good.  Things with long half lives stick around for a long time, but they are less dangerous because they don't produce as much radiation.  Learning about half lives made me realize that the really dangerous stuff will be gone before too long.   As for the longed lived stuff, the world is fulled of long lived radioisotopes (uranium, thorium, C-14 etc.).   It doesn't seem to hamper us much, if any.

Diffusion and Dilution 

Diffusion is a natural process where random collisions between particles in fluids or gasses cause them to travel around randomly becoming more intermingled within the medium. You can observe this process by placing a drop of red food coloring in a cup of water. Over time you can watch the red coloring spread out until the water is of uniform color. Here is a video that explains diffusion if you want to know more.



Radioisotopes mixed into air and water diffuse outward in all direction becoming diluted in the process. Picture the place where the radioisotopes starts out at as one side of the radius of a sphere and the distance they have diffused out to as the other side.  In order to better illustrate this Here is the volume of a sphere.

As you can see radius is taken to the third power.  As you can imagine this means that volume increases very quickly as radius gets bigger.  This is something called exponential growth. Exponential growth means the rate at which things grow also grows.  Here is a graph showing the growth of the volume of a sphere.

As you can see with exponential growth thing get large very quickly.  Even if things like the earth block some paths of diffusion it is still easy to see that the volume in which radioisotopes are diluted becomes large really fast, and dilution matters.  Things that are very dangerous in concentrated forums are basically harmless if diluted enough.  

You may be wondering about solid particles right now,  but if you are worried small particles like dust undergo diffusion as well although it's different than the diffusion for liquids and gasses. One difference is that dust consolidates on the ground which is two dimensional, but the area of a circle circle also grows exponentially.

Although things like wind also needs to be considered there are definitely limits to the concentration of small dust particles faraway from an accident.  As for larger particles I'm not sure what their means of locomotion would be. 

Conclusion 

This kind of thinking might not be much consolation to people close to a serious nuclear power incident where concentrations of radioisotopes are greater, but it definitely shows that there limits to the scope of nuclear accidents, and history has shown even residents close to serious nuclear power accidents don't die from radiation poisoning.    Radioisotopes with short half lives are dangerous in concentration, but diluted over a large volume they aren't that dangerous at all, and because they have a short half life what danger they do pose will soon pass. 

The World is full of Dangerous Stuff

Another reason why I'm not particularly worried is that that life is filled with harmful and potentially harmful things.  Heck, In 2014 761 people died on commercial airlines world wide while a staggering 33,783 people died in automotive accidents in the US alone.  For me nuclear power is pretty far down on the list of things to worry about.

One example of something potentially very hazardous is water.  If inhaled the content of a single swimming pool could kill hundred if not thousands of people.  Such a situation may seem ridiculous to you, but it's no more ridiculous than arguments that single nuclear reactor can kill us all (which ignores basic laws of physics like diffusion). 

At any rate here is some information about drowning:

Every day, about ten people die from unintentional drowning. Of these, two are children aged 14 or younger. Drowning ranks fifth among the leading causes of unintentional injury death in the United States

That's quite a few people.  Certainly more then die each day from nuclear energy.   I'm sure we could cut down this number by banned all the swimming pools and putting guards around all the rivers and lakes, but people aren't willing to do that because not only would it cost to much but swimming is fun.  I wonder why we are so rational when it comes to swimming but irrational when it comes to nuclear power.  After all affordable reliable energy is more than just fun, it a necessity of modern life.

To Much Fear and Hyperbole not Enough Facts

Of the two sides the anti nuclear side is by far the largest purveyor of bull crap. I've learned to take everything they say with a grain of salt.

Hey, I call it like I see it

I tend to believe that everyone has a little bit of bull crap in them, but the anti nuclear activists often take it to the extreme.  They are given to outrage with little in the way of facts, rampant  paranoia and dismissing anything that disagrees with their preconceived notions.    One example of anti nuclear bull crap can be seen below. 
.

Source

Maps like these are complete bull.  You could take a piss in the ocean and draw an equally scary map showing how your piss is slowly contaminating all the seas of the world, and it would about as meaningful as this map.  Let me give a quote that shows what they are talking about.

An estimated 538,100 terabecquerels (TBq) of iodine-131, caesium-134 and caesium-137 was released. 520,000 TBq was released into the atmosphere between 12 to 31 March 2011 and 18,100 TBq into the ocean from 26 March to 30 September 2011. 

Admittedly worse then urine, but not nearly as bad as they are making it out to be.   A think a good comparison for putting it into context would be to compare what has gone into the ocean to what was already in the ocean.

1. The oceans have Uranium in them. In the pacific ocean the radiation from Uranium is 22 EBq or 22,000,000 trillion becquerels.
2. The oceans have Potassium 40 in them. In the pacific ocean the radiation from Potassium 40 is 7,400 EBq or 7,400,000,000 trillion becquerels.
3. The oceans have Carbon 14 in them. In the pacific ocean the radiation from Carbon 14 is 3 EBq or 3,000,000 trillion becquerels.
4. The oceans have Rubidium 87 in them. In the pacific ocean the radiation from Rubidium 87 is 700 EBq or 700,000,000 trillion becquerels.
5. The oceans have Tritium in them. In the pacific ocean the radiation from Tritium is 370 PBq or 370,000 trillion becquerels.

So we have…
Uranium                      22,000,000 trillion becquerels
Potassium-40         7,400,000,000 trillion becquerels
Carbon-14                     3,000,000 trillion becquerels
Rubidium-87            700,000,000 trillion becquerels
Tritium                              370,000 trillion becquerels
Total            8,125,370,000 trillion becquerels

So we have 8,125,370,000 trillion becquerels of radiation in the pacific ocean from natural sources and the anti nuclear activists don’t seem to care, but when the fifth most powerful earthquake ever recorded results in 18,100 TBq of radiation being released into the oceans and they start drawing scary maps and acting like we are all doomed.    The logic in this position escapes me and it only gets worse...

Uranium 238 (99.284% of natural uranium) has a half life of 4.468 billion years, and uranium 235 (0.72% of natural uranium) has a half life of 703,800,000 years, so it's going to be producing those becquerels for a long long time.   If that still isn't enough for you rivers wash more uranium into the ocean at a rate of 32,000 tons (page 165) a year, and carbon-14 is only one of the radioisotope continuously showering us as a result of cosmic rays.   Still not enough for you... There's more.  Here is the decay chain for both naturally occurring forms of uranium.

source

That is an awful large number of radioisotopes continuously being produced in the oceans naturally, but anti nuclear activists don't seem to know or care at all. They seem only to care about radiation has to do with their agenda against safe clean nuclear power. This has made me lose a lot of trust in them.

Conclusion

There  are some people who think that Fukushima should mean the end of nuclear power, but their fears seem way overblown to me.  As I learned more about the different types of energy I've come to favour nuclear power strongly.  None of the other energy sources can do what it can.  Wind and solar are intermittent, have lower power density and scaling.  Fossil fuels are increasing hard to get at, and of course there is climate change to worry about.  Nuclear power gives me hope for the future which is why I think it's worth defending

Some Basic Information Useful for Understanding Nuclear Power Safety

When people talk about nuclear power safety they often don't explain certain basic information that you need to know in order to really understand the the subject.  This is probably for the best because repeating the same information over and over again would grow old really fast, but unfortunately this leaves people new to the subject unable to fully understand the arguments.  The goal of this article is to hopefully be helpful to anyone who doesn't understand the basics. Basically I tried to write something that I think would have been helpful to me when I was starting out. 

The Very Basic

Lithium atom model

Lets start with the very basic, all the stuff on earth is made up of tiny building blocks called atoms (you can see all types on the periodic table of the elements).  Atoms are made up of three things.  Those three things are electrons, protons and neutrons.  Protons and neutron exist in the middle of the atom clumped together in what is called the nucleus.  The electrons exist around that. Atoms can form molecules (i.e. groups of atoms) by sharing electrons. 

The type of atom (i.e. the element) is determined by the number of protons in it's nucleus.  For example atoms that have one proton are hydrogen atoms, and atoms that have 92 protons are uranium atoms.

Unlike protons and neutrons, the number of electrons an atom has can change fairly easily.  The default position for atoms is having the same number of electrons as protons.  When atoms don't have an equal numbers of protons and electrons they are called ions.  Knowing what ion you're dealing is important because different ions (even of the same element) behave very differently chemically which is why they came up with Equivalent notations for writing it down.

Example of Equivalent Notations

Every proton is +1, and every electron is -1, simple subtraction tells you what ion you've got.  For example iron (Symbol Fe) has 26 protons.  If an atom of Iron has 24 electrons then its ionic state is 2+ (26 - 24 = +2), and if it has 28 electrons its ionic state 2- (26 - 28 = -2).

The number of neutrons an atom has determines what type of isotope it is.  All atoms are some type of isotope even though it's not usually that important because different isotopes of the same element (i.e. type of atom) behave the same chemically for most intents purposes and thus it is often not mentioned or thought about.

Isotopes are identified by their atomic mass.  The atomic mass includes both protons and neutrons (electrons are very light so they don't count).  So for example there are three naturally occurring isotopes of carbon on earth.  They are called carbon-12, carbon-13 and Carbon-14.  Carbon has 6 protons so Carbon-12 has 6 neutrons (12 - 6 = 6), Carbon-13 has 7 neutrons (13 - 6 = 7) and Carbon-14 has has 8 neutrons (14 - 6 = 8).


Ionizing Radiation and Radioisotopes


Not all isotopes are stable.  Unstable isotopes eventually decay into different types of atoms releasing radiation in the process.  For example Carbon-12 and Carbon-13 are stable while Cabron-14 eventually decays into Nitrogen-14 (which is stable).

The unstable isotopes are called radioisotopes (also known as radionuclide, radioactive nuclide, or radioactive isotopes), and the radiation released is know as ionizing radiation although most people just call it radiation.

When an unstable isotope decays is random while the probability of it decaying over any period time is fixed.  This probability is understood through something called a half-life.  A half-life is the time it takes for half of a given amount of a radioisotope to transmute (i.e. decay) into something else

It's a bit like rolling a dice. Every time you roll a dice the chance of getting a one is the same.  If you replace "time you roll a dice" with "fixed period of time" and "getting a one" with "a type radioisotope decaying" it's exactly the same. 

You can also use the dice analogy to understand half-lives.  Picture that you were rolling a group of six sided dice.  Every time you rolled them you remove any dice that lands on a one.  The half life of these dice would be three rolls because after three rolls half the dice should be gone.  You might be thinking to yourself that half lives aren't very precise because of the random element, but you have to remember that atoms come in large numbers.   There are something like 78,000,000,000,000,000,000 atoms in a grain of sand.  If you rolled six dice then at the end maybe half would be gone or maybe not, but if you are rolling trillions of dice pretty darn close to half of them would be gone. 

In fact half lives are so precise that people use it for dating stuff.   There is something called Radiocarbon dating that uses the half life of Carbon-14 in order to tell how old things are.  Carbon-14 is constantly being created in the earth's atmosphere by nitrogen being bombarded by cosmic radiation.  Because it's being created at a constant rate it's also being absorbed by plants at a constant rate and from plants it moves to animals.  When something dies it stop taking in Carbon-14 so by using it's half life researches can tell how long ago something died based off the amount of carbon-14 left in it's remains.   

Some radioisotopes decay into other radioisotopes.  When that happens you have what is called a decay chain.  The decay chain is used to describe how radioisotopes decay until they eventually reach a stable state.  Here is the decay chain for Thorium a common naturally occurring radioisotope. 

You may be wondering at this point where all the radioisotopes on earth come from.   Well some (34 types) are primordial (i.e. they came about before the earth was formed).  This includes Uranium, Thorium and Potassium-40.  Some of them are caused by cosmic radiation such as Carbon-14.  A small minority are created as a result of human activity, the most common of these activities involves the breaking down of larger radioisotopes into smaller radioisotopes in order to produce energy.  Here is a really good link about radioactivity in the environment if you're interested in learning more about it.


Types of Radiation 


The types of radiation produced by radioisotopes include both Electromagnetic radiation and Particle radiation.  Electromagnetic radiation plays a big part in our lives.  Depending on the frequency it has many different applications and also names.  The most familiar form is the visitable spectrum, or more commonly just called light.  It's also useful for microwaves ovens, cell phones, radio, x-rays etc.

But for our purposes we are only interested in electromagnetic radiation that is ionizing radiation. Ionizing radiation is radiation that has enough energy to knock electrons off atoms (or molecules) thus ionizing them.   This is important because as we talked about before different ions behave much differently chemically.  This can cause problems.  In most cases a few atoms (or molecules) being ionized doesn't matter much, but in some cases it does.  For example ionizing radiation can cause harm to living tissue.  You've probably noticed such harm yourself if you've ever spent too much time in the sun and got sunburned.  

Some atoms (and molecules) hold their electrons better than others so what types of radiation are ionizing isn't so clear cut, but really what we care most about is the effect of ionizing on human beings so I would say ultraviolet (sun burn) rang and higher (higher frequency that is, the higher the frequency the more energetic the more able to knock of electrons) is ionizing radiation.

Usually when we are talking about radioisotopes decaying we are talking about gamma rays (i.e. y-rays), not X-rays or ultraviolet. Lower wave length ionizing radiation can be created as secondary radiation (i.e. ionizing radiation created by other ionizing radiation) though. 

Particle radiation is simply particles that are moving very quickly.  The two types of particles that matter for what we are talking about are Alpha particles and Beta particles.

Alpha particles are helium-4 atoms without any electron.  The ones created by radioactive decay have a strong ability to ionize things, but they have little ability to penetrate shielding and can be stopped by a piece of paper or the thin layer of dead skin all of us have. 

Beta particles are electrons or sometimes positrons.  Positrons are the antimatter equivalent of electrons.  When electrons and positrons meat they destroy each other releasing some gamma rays in the process.


Metric Prefixes


Now that we've covered what radiation is and where it comes from lets talk about how it's measured.  Well before that we have to talk about something call metric prefixes.  If you spend time reading about this subject you're going to encounter these things a lot.

For Micro it's usually abbreviated μ or mc

Metric prefixes are used for writing really large or really small numbers without having to write all the zeros.  It's very similar to scientific notations in that regards.  The prefix goes before the unit abbreviation.  For example with 10 cm the c is the metric prefix (centi) and the m is the abbreviated unit types (meter). 

It's fairly easy to convert a number to a different prefix or know the number in it's entirety (i.e. what the number is without prefixes). Look at the table above to the left of prefix you want to convert from.  The number to the right of the 10 is the one we're interested in.  Take that number and subtract the number next to the 10 of the prefix you want to convert to.  If you want to convert to no prefixes then subtract zero.    If the number you get is negative move the decimal point that many spaces to left, if it's positive move the decimal point that many places to the right. 

For example 1,000 nm (-9 - (-6) = -3) = 1 µm ,  1,000 µm (-6 - (-3) = -3) = 1 mm, 1,000 mm (-3 - 0 = -3) = 1 m, and 1,000 m (0 - 3 = -3 ) = 1 km.  Where m stands for meters.


Measuring Radiation


There are a lot of different ways of measuring radiation.  I'll try and go over the most common ones.

Activity (A)

Activity measures the number of nucleus decays.  It's calculated using amounts of radioisotopes and knowledge of there half lives.  The two main units for this are Becquerel, and Curie. 

The becquerel (symbol Bq) it is the SI derived unit of radioactivity.  One Bq is defined as the activity of a quantity of radioactive material (i.e. radioisotopes) in which one nucleus decays per second. Basically it's a unit used to describe the amount of radiation produced by some amount of radioisotopes.

The curie (symbol Ci) is a non-SI unit of radioactivity, named after Marie and Pierre Curie. It is defined as 1 Ci = 3.7 × 10¹⁰ decays per second.

Conversion factors:

1 GBq = 0.027 Ci

Absorbed dose (D)

Absorbed dose measures the energy (from ionizing radiation) absorbed by a mass.  This is important because it takes energy to ionize things so knowing how much energy is going towards ionizing things help you know how much stuff is getting ionized.  This in turn can help give you some idea of the effect.  Most Geiger counters measure this. The two main unit types for this are Rad and Grey.

The SI unit for absorbed dose is the gray (Gy).  One gray is the absorption of one joule of energy, in the form of ionizing radiation, per kilogram of matter.

The other unit is called the Rad.  The rad is a non-SI CGS unit that is sometimes also used, predominantly in the USA.

Conversion factor:

1 rad = 0.01 Gy 

Dose equivalent (H)

Dose equivalent is a measure of the health effect of low levels of ionizing radiation on the human body.   The two main unit types for this are Roentgen and Sievert.  Quantities that are measured in roentgens or sieverts are intended to represent the stochastic health risk, which for radiation dose assessment is defined as the probability of cancer induction and genetic damage.  There is no way to directly measure equivalent dose.  Instead other measurements are used to arrive at equivalent dose using various conventions.  For example with X-rays and gamma rays the gray is numerically the same value when expressed as the sievert (Sv), but for alpha particles one gray is equivalent to twenty sieverts because of the radiation weighting factor that is applied.

Conversion factor:

1 rem = 0.01 Sv

Radiation Inside the Body


Internal doses can be worse than external one's (depends on amounts and other factors).   For example alpha particles can be stopped by a thin layer of dead skin making them fairly harmless outside the body, but more dangerous than other types of radiation inside it.  In fact a large part of people's average annual doses comes from alpha particles produced by the decay of Radon (symbol Rn).  Radon is an odourless, colourless, gas that exists in small amounts all around us.  Radon is constantly being created as part of the decay chain of all the naturally occurring isotopes of uranium and thorium.

At any rate predicting internal doses is important.  An important thing to remember when internal doses are concerned is that different isotopes behave the same chemically.  This can be both a good thing and a bad thing.  For example Iodine-131 is a radioactive isotope of iodine that is produced a lot in nuclear reactors.  It has a half life of about 8 days.   Like all iodine it's utilized by the thyroid which means if it gets released into the environment it can be a problem.   Luckily by taking potassium-iodide pill you can flood your body with non radioactive iodine so Iodine-131 wont get absorbed, and because it's half life is so short it will be gone in short order.  Because they behave the same chemically radioisotopes also have many beneficial uses such as Radiopharmacology a branch of medicine which uses radioisotopes for medical imaging and in therapy for many diseases (for example, brachytherapy).  Ironically Iodine-131 is also one of the radioisotope used in medicine.

Internal Dosimetry 

Internal dosimetry is the science and art of internal ionizing radiation dose assessment due to radioisotopes incorporated inside the human body.  Radioisotopes deposited within a body will irradiate tissues and organs and give rise to committed dose until they are excreted from the body or the radionuclide is completely decayed.  The internal doses for workers or members of the public exposed to the intake of radioactive particulates can be estimated using bioassay data such as lung and body counter measurements, urine or faecal radioisotope concentration, etc.


Man-Made Radiation Exposure Breakdown 

This kind of depends on what you think of as man made exposure.  For example is Radon pumped into people's houses along with natural gas man made or natural exposure?  At any rate, not counting stuff like Radon most man made radiation exposure is a result of various medical procedures (such as x-ray).  This accounts for around 20% of exposure worldwide and up to 50% of exposure in  industrialized countries.  Here is a pie chart.

Harm

Linear no threshold model

The most widely accepted model for determining harm for low doses is known as the Linear no threshold model  (LNT).  For this model it doesn't matter how much radiation you receive.  All radiation can cause harm, all radiation has an equal chance of causing harm.  Here is a nifty online calculator for it applying it. 

Organizations That Support LNT

 United States National Research Council

"The assumption that any stimulatory hormetic effects from low doses of ionizing radiation will have a significant health benefit to humans that exceeds potential detrimental effects from the radiation exposure is unwarranted at this time."

United States National Academies

"The scientific research base shows that there is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless or beneficial."

 National Council on Radiation Protection and Measurements

United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)

Until the [...] uncertainties on low-dose response are resolved, the Committee believes that an increase in the risk of tumour induction proportionate to the radiation dose is consistent with developing knowledge and that it remains, accordingly, the most scientifically defensible approximation of low-dose response. However, a strictly linear dose response should not be expected in all circumstances

The Controversy

Radiation can be harmful. Everyone seems to agree with that.  What people can't always agree about is the effect of very small doses of radiation.  Anyway Here is a page that does a good job of describing the controversy.  If you want to understand this subject better this is worth reading. 

Living things evolved in a world full of radiation.  Various biological defence mechanisms have come about in order to protect organisms from it and other sources of harm.  Here is a list of some of our bodies defences. 

1. Defences against the metabolically induced reactive oxygen species (i.e. defence against things that have been ionized),  
2. DNA repair, and  
3. Elimination of damaged cells. 

The big disagreement is low levels of radiation, where it is difficult to show statistically what is going on.  There are several different models that describe the effects of radiation at low doses. 

Another model is the threshold model

This model says that only radiation over a certain dose is harmful.

Organizations that support this model

French Academy of Sciences (Académie des Sciences) and the National Academy of Medicine (Académie nationale de Médecine).

In conclusion, this report raises doubts on the validity of using LNT for evaluating the carcinogenic risk of low doses (< 100 mSv) and even more for very low doses (< 10 mSv). The LNT concept can be a useful pragmatic tool for assessing rules in radioprotection for doses above 10 mSv; however since it is not based on biological concepts of our current knowledge, it should not be used without precaution for assessing by extrapolation the risks associated with low and even more so, with very low doses (< 10 mSv), especially for benefit-risk assessments imposed on radiologists by the European directive 97-43.

Hormesis Model

Another model is the  is the hormesis model which postulates that a certain amount of radiation actually decreases your chance of getting cancer a little because it stimulates your body's natural defences.

What People agree About

At any rate pretty much everyone agree about larger doses so Here are a few facts I think anyone would agree with. 

• 100 rem received in a short time can cause observable health effects from which your body will likely recover, and will increase your chances of getting cancer.
• 1,000 rem in a short or long period of time will cause immediately observable health effects and is likely to cause death.

Conclusion 


As for conclusions there isn't one really.  Hope this was helpful to someone.

Update:  I've made a lot of changes in order to make it more complete.  Also, changes some things to make it more balanced.

Comparing Aviation and Nuclear Power's Safety Record for 2014

It often seems like people zero in on the dangers of certain things while largely ignoring the dangers of others.  For example commercial airlines.  People are often more afraid of flying then they are of driving, and if they've been watching the news this year they would probably feel justified in their fears as this year has seen news story after news story about downed and missing airliners, but things are not always as they appear to be.   In 2014 761 people died on commercial airlines world wide while a staggering 33,783 people died in automotive accidents in the US alone.  Things can look a lot different when you compare statistic than they do when you just go by gut feeling, or what makes the news more often.  Often people consider nuclear power to be dangerous.  Far more dangerous then flying, but I wonder if that's really the case.  That's why I'd like to try and compare Aviation and Nuclear Power safety record for 2014.

Accidental Deaths 

The first comparison is talking about the number of people directly killed as a result of the different activities.  This comparison doesn't deal with radiation.  That's up next. 

Aviation
Well we got 761 death for commercial aviation.

Nuclear Power
Three people died in and industrial accident while constructing a nuclear reactor.  They most likely died of asphyxiation from breath pure nitrogen gas.  Nitrogen gas is sometimes used in construction. 

Conclusion 
761 is much larger then 3.  Point 1 goes to nuclear.

Radiation Exposure 

This section is for comparing radiation exposures between the two activities.  Some useful information: 1,000 nSv = 1 µSv,  1,000 µSv = 1 mSv, and 1,000 mSv = 1Sv.  Sv stands for Sievert which is a unit used to measure the effect of low levels of ionizing radiation on the human body

Aviation
Lets start with commercial aviation.  On commercial airlines people are exposed to higher the normal levels of ionizing radiation because of their altitude.  Basically there's ionizing radiation coming from space (i.e. cosmic radiation).  A lot of it gets blocked by our atmosphere, but not all of it, and when you higher you receive large doses (also being closer to the equator gets you higher dosages).  So lets try and calculating how much radiation exposure results from air traffic.

According to the FAA Revenue Passenger Miles (An RPM represents one paying passenger travelling one mile) where 815 billion in 2011 and expected to be 1.57 trillion in 2032.  That's as close as I could get to 2014 with my Google skills, but It probably hasn't changed that much in three years so I'll just go with it. I couldn’t find information on total hours passenger spent travelled so but a commercial jet travels between 500 to 900 km/hr.  With that and a little math we get 1.46 to 2.62 billion total hours flown by paying customers in 2011, and a projected 2.81 to 5.05 billion total hours flown by paying customers in 2032. 

That is a lot of hours. Next lets look at what people are exposed to during those hours. The amount of radiation people are exposed to during flight depends on both altitude and latitude, so in order to get a better idea of the rate of exposure people can reasonably expect during commercial flights lets look at some data taken from Xinjiang Airlines.

Feng YJ, Chen WR, Sun TP, Duan SY, Jia BS, Zhang HL. Estimated cosmic radiation doses for flight personnel. Space Med Med Eng 15(4):265–269; 2002.

• The average effective dose rate of all flights of Xinjiang Airlines from 1997 to 1999 was 2.38 µSv h^-1.
• The average annual cosmic radiation dose for flight personnel was 2.19 mSv.
• Annual individual doses of all monitored flight personnel are well below the limit of 20 mSv y^-1 recommended by the International Commission on Radiological Protection (ICRP).

Now we need to know the average world wide natural background radiation so we know how much more people get while flying.  Using Wikipedia I got this 0.27 µSv/h (Derived from 2.4 mSv a year) So with a bit of subtraction I get 2.11µSv/h (2.38 - 0.27 = 2.11) more radiation from flying.  Using this we have 1.46 Gh to 2.62 Gh times 2.11 µSv which equals 3,100 Sv (3,080,600,000 µSv) to 5,500 Sv (5,528,200,000 µSv).  If you applied Linear No-Threshold Model to that it would equal 155 to 275 extra cases of cancer for one year of commercial flight, projected to almost double by 2032.  To put that number in perspective this study estimates a total of 130 fatal cancers as a result of the Fukushima nuclear accident.  Though some people contest the validity of applying the Linear No-Threshold Model to low levels of exposure. 

I looked for information about military aviation exposure, but couldn't find anything so I'll leave that out.  I'm also leaving out commercial pilots.  They fly aircraft for other reasons, such as charter flights, rescue operations, firefighting, aerial photography, and aerial application, also known as crop dusting.  I have no clue what kinds of does they get.  For things like crop dusting I'm guessing not a lot. 

For information about flight attendants and pilot.  I was able to get some employment numbers.  There were  84,800 jobs for flight attendants, and for airline pilots there were  66,760 (104,100 - 37,340 = 66,760) job.  From the study quoted above we get 2.19 mSv does for flight personnel each year so that adds another 330 Sv (331916.4 mSv = 2.19 mSv (66760+84800)). 

Next lets talk about space.  Do to the lack of atmosphere astronauts get higher dosage than most professions do.  So lets try and calculate that.  The international space station has six crew spots and they've been filled all year round.  I've found this information about their doses.

The green line is the one that matters to us.

The number on the left are for annual mSv.  The number one the bottoms describe aluminium shielding with 0 being zero shielding and 100 being the most shielding.  Looking at the green line, at solar minimum it looks like they get up to 225 mSv  unshielded, and down to around 75 mSv shielded by aluminium.  I'm just going to assume they're shielded most of the time and call it 100 mSv a year.  There are 6 people on the station all year round so we end up with 600 mSv.

All together for aviation 2014 we get between 3,430.6 Sv to 5,830.6 Sv.  There are a lot of things I've left out like solar particle events, but given my limited resources and waning patience this will have to do.

Nuclear Power  
When you think nuclear and radiation the first thing on a lot of people's minds these days seems to be Fukushima.   So I did some searching and found one map that shows up to date radiation readings, and the other map shows the current evacuated areas.  Here are the two maps side by side at roughly the same scale (I think).

I find these maps rather interesting in light of what I've learned about aviation.   Consider 2.38 µSv/h the the average does for airlines that I used above.   If I wrote this like the radiation readings map it would be 2,380 nSv/h, and would be accompanied by an ominous red dot.  It becomes even more interesting when you consider that 2.38 is just an average. Depending on the type of flight exposure can be much higher.  From an earlier link. 

Friedberg W, Copeland K, Duke FE, O'Brien K 3^rd, Darden EB Jr. Radiation exposure during air travel: Guidance provided by the FAA for air carrier crews. Health Phys 79(5):591–595; 2000.

• Seattle to Portland: 0.03 mSv per 100 block hours
• New York to Chicago: 0.39 mSv per 100 block hours
• Los Angeles to Honolulu: 0.26 mSv per 100 block hours
• London to New York: 0.51 mSv per 100 block hours
• Athens to New York: 0.63 mSv per 100 block hours
• Tokyo to New York: 0.55 mSv per 100 block hours

On the first map a flight from Athens to New York would be listed as 6,300 nSv/h. Furthermore the space station data from Nasa would get purple dots with the heights level of shielding getting 8,560 nSv/h, and no shielding getting 25,700(much higher than anything on the Fukushima map). I find it ironic that people can get on a plane and travel halfway around the world, or even go to space, while thousands of Japanese people aren't even allowed to travel the handful of miles needed to see their own homes.

Unfortunately while this investigation was interesting to me it didn't really give me an idea of what doses people are getting because of Fukushima. I was starting to worry that I would ever get the information I need but luckily Wikipedia came to my rescue again (The same page even). From that article I got an average of 0.0002 mSv a year exposure worldwide. Knowing that there are around 7.3 billion people on earth we can do a little math and get 1,460 Sv ((7,300,000,000 * .0002)/1000 = 1,460) a year exposure from nuclear power.

Conclusion

With between between 3,430.6 Sv to 5,830.6 Sv. from aviation  and 1,460 Sv from nuclear power.  Point 2 goes to nuclear. What an upset victory! 

Terrorist Threat

Terrorist threats are on a lot of people minds these day.  People keep worrying about what they might be up to next. So the question this time is what is more vulnerable to terrorist attacks.  Nuclear power plants or aviation.  Something like this is really hard to put a number on.  Luckily Wikipedia came to my rescue again with the List of terrorist incidents in 2014.  I'm just going to add up all the ones that had to do with nuclear power or aviation.  The one that gets the least wins.

Aviation
Aviation has a bit of history of terrorism with the whole Twin Towers thing.  Lets see how it fared this year. 

Date	Type	Dead	Injured	Location	Details	Perpetrator
Feb. 13	Car bomb	7	19	Mogadishu, Somalia	A remote control car bomb exploded near the international airport in Mogadishu as a convoy of U.N vehicles traveled by, damaging one of the U.N vehicles, killing seven Somali civilians and injuring 15 civilians and four security guards. No U.N. Somali or International staff were injured or killed in the terrorist attack.[68][69]	Al Shabab
June 8	Attack	14 (+10 terrorists)	14	Karachi, Pakistan	Gunmen stormed Jinnah International Airport, killing 24 people and injuring 14 others.[160]	Tehrik-i-Taliban Pakistan
June 21	Attack	0	0	Jalalabad, Afghanistan	Taliban fighters fired eight rockets at a Jalalabad NATO air base. No casualties or property damage were reported.[181]	Taliban
June 26	Suicide bombing, shootout, raid	13	n/a	Seiyun, Yemen	Assailants conducted a series of attacks in the Seiyun, Yemen. In one attack a suicide bomber drove an explosive-laden vehicle into the entrance of an army base, killing four soldiers. In another attack, non-state militants attempted to raid Seiyun's airport, killing two soldiers. The government killed four militants in order to regain control of the airport. In another attack, a civilian woman was killed by an agricultural plant.[19	Al-Qaeda in the Arabian Peninsula

Nuclear Power

There wasn't any.

Conclusion

Nuclear wins again.  There are a lot of things about airports that make them good targets.  For example lots of people going in and out leaving holes in security.  Also, they often exist in places that have a lot of terrorists making them conveniently located targets for them to lash out at the 'evil' foreigners.  

The Dangers of War   

I'm not really sure that this is comparison is really needed, but people often argue that nuclear power is a nuclear weapons proliferation threat so I figured I better at least mention it.  My own view is that technical advancement of any kind is a nuclear proliferation threat.  If you want to keep someone from getting nuclear weapons you have to basically keep them down so that they can not make anything that can threaten you.  Such a practice is unethical in my opinion, and counter productive because poor miserable people are more likely to be violent.  Really instead of holding some people down I think we should bring everyone up so that we can all enjoy the fruits of technological progress together.  Then I think the world would be a much safer friendlier place.  In the end I declare this category a tie because I can not quantify this in any way that I find meaningful.

Final Conclusion

 
Nuclear wins!

Whether or not this article changes your mind about anything I hope you enjoyed it, and it at least made you think.