Temperature is in the news. Recently two large blizzards have struck Colorado, but of course, news about blizzards in Colorado do not constitute unusual events really. We all more or less expect snow in Colorado, which is, of course, the reason places like Aspen and Vail and Telluride are all so famous. It is more remarkable when it doesn't snow in Colorado. On some level it is reassuring that Jerry Ford's old haunt in Vail has had a white Christmas.
In many places around the world however where people expect snow however, it has not appeared, or if it has appeared, it has been fleeting. Where I live in New Jersey for instance, we have passed December and have seen not a single flake. Temperatures have been above freezing most of the time. Europe is experiencing similar events, and so are the Northern reaches of Canada, where recent news concerns the breakup of a massive ice shelf off of Ellsmere Island. Temperatures around the world have been so unusually high this year that even members of the faith based Republican Party - a party seldom troubled by facts or measurement - has been forced to concede that something most unusual is going on. Most rational people connect these events with the burning of fossil fuels.
But, that aside, what do we mean when we say "temperatures are rising?" Specifically, what is temperature?
Of course since preliterate times, humanity has had a sense of hot and cold connected with our primary senses, but for much of human history, the procedure for precisely measuring how hot or cold something was extraordinarily elusive. Part of the problem was the difficulty of knowing what "hot" and "cold" really meant. There seemed to be some kind of "stuff" called heat, and drawing on certain reference points, one could make a stab at identifying something about how it came and how it went, but the way it did so involved some mystery. Even the common reference points could be befuddling. It was not immediately clear, for instance, that water always boiled in the same way when one added heat to it. If one tried this in Switzerland, at relatively high altitudes, for instance, one would obtain different values for the amount of water that boiled away than if one added heat in Holland. For instance, if you took identical amounts of coal and burned them under pots of water exactly the same size and weight, more water would disappear in Zurich than would disappear in Amsterdam.
Some residue of the confusion remains ensconced in one common temperature scale used in the United States. Originally the Fahrenheit scale defined 100F as the normal temperature of the human body. (Zero was defined as the eutectic point of a water/salt solution - the temperature at which salt cannot prevent ice from forming.) Later when the Fahrenheit became attached to better calibration devices than human flesh - which is in any case variable - it was discovered that the average human body did not have a temperature of 100F, but rather 98.6F.
There you have it.
The first serious stabs at developing a more reliable measurement of how "hot" and "cold" relied on the isolation of pure gases, beginning of with the work of the husband and wife team of French Chemists, the great Lavoisiers - primarily credited to Antoine - the English Chemist Priestly, and the Swedish chemist Scheele. (As an aside, Lavoiser has the unhappy distinction of being one of the most important scientists ever to have been executed.)
Once relatively pure gases of known composition became available, it was found that the volume they occupied varied in a regular way as one compared them with other known markers of "hot" and "cold". The first thermometers didn't involve mercury. The first thermometers were gas thermometers. Their discovery was connected with the development of the hot air balloon in France. The law covering the relationship between temperature and volume is known as Charles's Law, which states that for a given gas, the temperature can be defined as a constant divided by the volume of the gas. Charles's law was one of the first systematic ways of defining temperature.
Still, it seemed that there was still something deeper involved in the concept of "temperature," and its relationship to the related, but clearly different concept of "heat." Full explanation of what temperature was and how it related to heat would wait nearly a century, for work by the Austrian physicist Ludwig Boltzmann, who was one of the most important developers of the idea that temperature is a statistical concept. (As an aside, Boltzmann has the unhappy distinction of being one of the most important scientists ever to have committed suicide.)
According to Boltzmann and others who developed the science now known as "statistical mechanics" temperature is a function of the average kinetic energy of molecules. The kinetic energy of molecules in turn, is related to the speed of molecules by taking half of the square of the velocity of molecules (here called "speed") and multiplying it by a constant we call "mass." Thus if one knows the mass of particular molecules, say, helium atoms, and one knows the energy of this molecule, one also knows what its speed it. The actual average speed of molecules depends on the chemical nature, physical state (gas, solid, or liquid) and the particular value of the constant we call "mass" of the molecules involved. Moreover it is important to note that not all molecules will be traveling at the same speed. Individual molecules might be going very much faster than average, or very much slower. In fact, properly put, temperature is a distribution of molecular speeds. If one knows the temperature of a particular gas, helium for instance, one will be able to make experimentally verifiable predictions about the fraction of molecules of helium that have a speed higher than the escape velocity of the earth.
Most gases, fortunately including nitrogen and oxygen, do not have, at earth's current temperature, a noticeable fraction of molecules traveling at speeds that exceed the escape velocity of earth. They have too much mass. On the other hand, as I just alluded, the fraction of helium atoms, which have relatively little mass, exceeding earth's escape velocity is rather large, amounting to a few percent. Normally they just don't make a bee line for outer space, because they bump into other molecules, often slowing down, but at high altitudes where the air is thin sometimes avoid such collisions and do leave the planet. Helium, while it is the second most common element in the universe as a whole, is a relatively uncommon element on earth. This is because when helium leaks out of a party balloon or is released in some other way, it remains in earth's atmosphere for a relatively short amount of time. Eventually it boils off into space, with the "hottest" (fastest) gas molecules traveling so fast that they are moving faster than rocket ships and earth's gravity cannot hold them.
(Oh by the way: People don't talk about it much, but the world is running out of helium - a problem that will have major technological consequences in the future. Almost all of the helium now found on earth comes from a few natural gas wells in Kansas, where it has been trapped in rock formations that have experienced significant amounts of radioactive decay over many hundreds of millions of years. These wells will go dry soon. One might be able to get some helium from the decay of plutonium-238 and curium-242, but not very much.)
Returning to the more prosaic case of atoms that remain on earth, we generally do not notice these distinctions about molecular speeds because molecules are so small and there are so many of them. We are concerned with their average behavior, which we have learned to call "temperature." An oxygen atom traveling at the speed of a jet plane will not hurt us, because it is very small, and is balanced by oxygen atoms that are hardly moving at all.
Now we are approaching the true subject of almost all NNadir diary entries on DKos, nuclear power and its risks. Today I want to talk about the risks of radioactivity, focusing on a particular radioactive substance, tritium.
Tritium is an isotope of hydrogen, meaning that it mostly behaves like the hydrogen found in ordinary water and in living things. Because tritium is about three times as heavy as the average hydrogen atom, there are a few differences in the way tritium behaves compared to hydrogen, but mostly these differences are minor. Once tritium gets out into the world, it goes wherever hydrogen goes, usually ending up as tritiated water that is mixed with all the water on the earth. Tritium can be found in rain, in lakes, in oceans, plants and in human and animal flesh. Tritium is also radioactive. Maybe this will frighten you and maybe it won't, but I assure you that, irrespective of your emotional reaction, as you are reading this, somewhere in your flesh right now, there are radioactive tritium atoms pretending to be ordinary hydrogen atoms.
What does it mean to be radioactive? Radioactivity, like temperature, is transformation that is thought to be very regular and measurable, but in fact, on an atomic level it is a statistical concept, just as temperature is a statistical concept. Suppose one could isolate a particular atom of tritium and contemplate it continuously. One would expect that eventually it would emit an electron from its nucleus, gain a proton, and be transmuted into another element, helium, in this case the uncommon light isotope of helium, He-3. One would have no way of predicting the precise moment this transformation would occur. It could occur within the first 30 seconds that one is looking. On the other hand, one's whole life could pass, and nothing would happen. However, if one has a great many tritium atoms, one will understand that the rate of tritium decay will seem relatively constant and regular. If for instance, one had 100 trillion tritium atoms - something that is relatively easy to do - one would expect that after 12.33 years, one would have about 50 trillion tritium atoms left, and would have accumulated 50 trillion new atoms of helium-3. Thus 12.33 years is the "half-life" of tritium.
Follow this link to find a picture of a device you can buy on line that contains more than 50 quadrillion atoms of radioactive tritium.
Different substances have different half-lives, of course. The half-life of potassium-40, for instance, which is also found in your flesh, and which is also radioactive, is 1.3 billion years. The half-life of the radon gas you may have in your basement if you have a basement and live in certain parts of the country, is 3.82 days. In every case, the "half-life" is a measurement of a statistical probability. All of the potassium-40 atoms in your body could go off in the next ten minutes, or they might never go off, but if you are average, only some of them will go off. It is easy to show that if you weigh about 70 kg, about 4000 will go off in an average second.
We say that an average human being weighing 70 kg and not experiencing a potassium deficiency has 4000 "bequerels" of radioactivity from potassium, where a "bequerel" is a unit of measurement that counts decays on an atomic level. Another unit of radioactivity that is common is the "curie," abbreviated "Ci." This unit is based on how many decays statistically occur in an average second in one gram of the element radium, which was one of the first highly radioactive materials isolated. The number of decays was long thought to be about 37 billion decays per gram, and later refinements in measurement showed that this was a little off for radium, but we continued to define one curie as 37 billion bequerels. Thus a 70 kg human being contains about 0.11 microcuries, or 110 nanocuries of radioactive potassium.
Let's get back to tritium. Tritium's half life is so short that it would disappear if it wasn't constantly being made. Tiny amounts of it are in fact made in the upper atmosphere because of certain radiation from the sun and other parts of space, but none of the tritium so made is isolated for human use. Humans use tritium not only for luminescent watch dials like the ones to which I have linked, but they also use it to make things that are much more dramatic, like hydrogen bombs for instance. The "hydrogen" in "hydrogen bombs" is often tritium. Tritium is also used in certain kinds of scientific research and for treatment of certain types of cancer and other diseases. Some people, not necessarily me, put a lot of hope in faith in the idea that it will some day be possible to build "fusion reactors" that will produce unlimited energy. These reactors, if developed and built, would also require tritium.
None of the tritium produced for any of these technological purposes occurs naturally. All of the tritium used by humans, no matter what their purpose, is made in nuclear fission reactors. (A caveat - some hydrogen bombs are designed to make tritium in situ. - if they are not so designed - it is necessary to continually replace the tritium in their cores.) This does not mean that nuclear reactors make tritium because we want it. Some reactors are designed to make more tritium than others to serve military or commercial or research needs, but most often tritium is made under circumstances that are not deliberate or are even problematic. It is not possible to operate a nuclear fission reactor without making tritium.
I am going to briefly discuss and then leave aside for a moment the types of reactors where tritium is made for deliberate purposes. In general these reactors are not involved in energy production for the most part. Some, though not all, of reactors that are designed to make tritium are in the nuclear weapons complexes of the major powers. For the record, I oppose all nuclear weapons, and I want all of them dismantled. I do not want anyone to build new nuclear weapons either. I am proud to say that I am a pacifist more or less. I think war, including nuclear war, is always wrong.
That said, I am not in favor of banning tritium, because I am not in favor of banning nuclear energy. On the contrary, I think we should make more tritium since we should use more nuclear energy. It's not that I'm fond of tritium either. I just accept it as a byproduct of the production of nuclear energy.
How does tritium form in nuclear reactors that are used for the generation of useful commercial energy? It happens in two ways. First off, when uranium is broken apart, occasionally, albeit rarely, it will break apart in such a way that an atom of tritium is formed. This is called "ternary fission," and for a normal type of nuclear reactor of the type we use in the United States that is fueled with uranium-235, 1.44 fissions in every 10,000 will produce an atom of tritium. If you want to know more about ternary fission, you can click on this sentence. A 3000 MW(th) nuclear reactor - a typical nuclear power reactor - will fission about 0.04 grams of uranium each second it operates at full power. At the same time it will produce about 60 billionths of a gram of tritium. Of course, at the same time this tritium is being formed, some of it is decaying to give helium-3. Eventually, as tritium accumulates, it reaches equilibrium, where it is decaying at the same rate at which it is being formed. The second way that nuclear reactors can form tritium is that ordinary hydrogen, with which most nuclear reactors are bathed in the form of water, can capture neutrons and be transformed into tritium. This process is not very important in ordinary "light water" nuclear reactors which do not contain very much of the normal heavy non-radioactive isotope of hydrogen called "deuterium." However it is a significant issue in the types of reactors that are used in Canada, which are "heavy water" reactors, often called "CANDU" reactors. As it happens most of the world's supply of tritium is found in Canada, where it is isolated from the coolant/moderator of CANDU reactors. Of course, Canada does not build hydrogen bombs, and most people do not lay awake at night wondering what Canada will do with its tritium.
Right now Canada has almost 20 kg of tritium on hand.
If it is your misfortune to chat with Greenpeace types - something that almost always makes me cranky and unpleasant - they will carry on at length about tritium and nuclear power reactors. They love to breathlessly report about how tritium has been "found" in "groundwater" near nuclear power plants. They will not be lying when they say this, by the way. Tritium has been found in groundwater near nuclear power plants. NNadir, nuclear power advocate, is here to state that nuclear power plants can and do release tritium. Moreover I am going to tell you another truth about tritium that Greenpeace types will often cite. You're stuck with it. If your well contains tritiated water there is absolutely nothing you can do about it. If tritium makes you really, really, really upset, the only way you can avoid drinking tritium is to stop using the well. According to Greenpeace, you are supposed to get all worked up about this, and agitate for "an end" to this "threat" from nuclear power stations. After all, Greenpeace will state, once more evoking the truth, once tritium gets in groundwater there is really no physical way to remove it.
It happens that tritium "contamination" is found throughout the world and is readily measurable. The concentration of tritium is regularly monitored since the early 1950s and has been monitored continuously since before nuclear power plants, beginning in the late 1960's, became the fairly common approach to the generation of electricity that they are now. A special unit has even been devised for these measurements: It is called the "tritium unit." A tritium unit is equal to 0.118 bequerels per liter of water, meaning that if you wanted to be sure to have a statistical average of one decay per second, you would need to have eight and half liters of water having "one tritium unit" of contamination. With this monitoring in mind, it is relatively easy to determine whether or not the operation of nuclear power plants has lead to an increase in tritium "contamination" throughout the world. So has the world become increasingly contaminated with tritium since nuclear power plants have become commonplace? The answer can be found here:
Measurement of Tritium Contamination Around the World.
Surprise. The world contamination with tritium has been falling dramatically since 1963. In 1963 the world's tritium concentration in the environment peaked. In many places on earth the level of contamination was over 5000 "tritium units," whereas by 1995 it was well under 20 "tritium units" in most places in the world.
Here is some data for Eastern Hungary, not all that far from those nasty French nuclear power plants.
It is now possible using data contained in these links, if we add this link as well, to estimate how many cancers were caused by tritium throughout the world as a result of tritium from all sources including both nuclear weapons test, the natural creation of tritium in the upper atmosphere, and those awful nuclear power plants that I advocate and support.
According to the last link I provided, every time a person drinks 1 picocurie of tritium (one trillionth of a curie) his or her risk of cancer increases by 4.4 one hundred trillionths. (See the box on the bottom.) It can be shown that 1 "tritium unit" is the equivalent of 3.2 pCi per liter. Multiplying 3.2 pCi per liter by 5000 by the cancer risk we find that the risk from tritium of drinking a liter of water in 1963 was about 1 in 1.4 billion. World population in 1963 was about 3.2 billion. If we assume that the average person drank 2 liters of water per day each day of the year, it is easy to estimate that the number of cancers induced amounted to about 1600 people.
Today the number of tritium units found is about 20, which corresponds to a risk per liter of around 1 in 360 billion per liter of water. World population is much higher, about 6.6 billion. It follows that the number of people who die this year from tritium, again assuming two liters per day of water, will be a little over 13.
They won't remark on this over at Greenpeace, but the number of people killed in the Sago coal mine disaster in West Virginia was also thirteen. Of course the number of people who have died from air pollution this year is vastly larger than the number of people who have were killed from tritium, even including the ridiculous, immoral, and unnecessary tritium released by the testing of nuclear weapons, but they won't tell you that at Greenpeace either.
Once again, nuclear energy is not risk free. No form of energy is risk free. I am absolutely convinced that each year tritium from nuclear power plants actually causes a few deaths around the world. However in comparison to the deaths caused by not using nuclear power, the matter is more or less trivial.