In the thrall of a two-faced god

kw: book reviews, nonfiction, science, science and politics, history of science, radiation, short biographies

This post's title is taken from the last chapter of The Age of Radiance: The Epic Rise and Dramatic Fall of the Atomic Era by Craig Nelson. Nelson chronicles the discovery of radiation and radioisotopes, and development of various radioactive products, that began in the late 1800's. He carries through to the present day, in which more than 400 nuclear power stations produce about 1/7th of electricity worldwide, hundreds of radioactive isotopes are known and dozens are used for various medical and industrial purposes, yet several major power plant failures and the problem of accumulating waste from nuclear power plants has led to overweening public fear of anything related to the word "radiation".

Thus, I have observed that the "epic rise" and "dramatic fall" refer to public perception. Prior to 1945, radiation was extremely popular. Lying in a pool of radioactive water was supposed to be therapeutic. Even in 1960, when I was given a half-ounce of "yellowcake" (pure U₃O₈) powder in a gelatin capsule on a field trip to a Uranium processing plant, it was considered rather benign, and such "pills" were suitable gifts to a troop of Boy Scouts. Public hysteria had yet to set in. Trips to Las Vegas to see A-bomb tests were still popular, and would remain so until 1963. Even then, the end of air-blast testing was a result of a treaty with the USSR, not from public protest in America.

Nuclear waste became an issue primarily in America, because of a set of rather odd laws that prohibited reprocessing spent fuel from nuclear power plants. This is done as a matter of routine in Europe.

A side note for those who need it: Induced fission of Uranium or Plutonium results in "fission products". When a large nucleus is split because it has absorbed a neutron, it leaves behind two fragments (sometimes three) whose mass totals the original mass, minus the mass of two or more neutrons released during the fission event. It is kind of like a drop of water splitting into two smaller drops plus a few tiny droplets. These fission fragments are usually radioactive isotopes, typically with several excess neutrons, so they tend to decay quickly by beta decay, which converts neutrons to protons and balances the nucleus better. Several such decays will result in a stable nucleus. The trouble comes because some of the "quick" decays actually occur over months or years. These longer-lived isotopes accumulate in spent fuel from reactors, and as a result, it stays "hot" for thousands of years. Chemical processing can easily separate out these waste products, leaving purified Uranium or Plutonium, whichever "fuel" was first used. Purified Uranium is called "depleted Uranium" because the power-making isotope has been greatly reduced or eliminated. This stuff makes great bullets for snipers, being almost twice as dense as lead. Reprocessed Plutonium can be returned to the reactor as fresh fuel. Also note that reactors that use enriched Uranium are designed quite differently from those using Plutonium.

In the late 1970's there was a great debate going on about the safety of storing nuclear power plant waste. I was at a public event where a nuclear power industry representative described the materials. He said that the spent fuel from a certain kind of plant would be in a canister that looks a lot like a 50-gallon oil drum, but that it would initially be producing 10,000 watts of heat from the decay of fission fragments. This would decline to 5,000 watts over several hundred years, then be quite steady for thousands of years thereafter. I stood and asked, "May I obtain one or two to heat my crawl space in winter?"

Back to the book. The historical sketches and mini-biographies are invaluable. Dr. Roentgen, the Curies, Fermi, Oppenheimer and so many others are brought to life as rounded personalities in a way I have not read elsewhere. The glacially slow tragedies that prematurely ended the lives of nearly all early students of radioactivity are heartbreaking. It took much, much too long for scientists to realize that the energetic particles released by these isotopes were displacing electrons or atoms from their places throughout any material they passed through, including their own bodies. Such displacement did damage that frequently resulted in cancer or, at higher levels, radiation toxicity and even rather rapid death at the highest levels. A further note on isotopes:

An isotope is a form of an element characterized by a specific number of neutrons in the nucleus. Thus, all atoms of Oxygen have 8 protons in the nucleus, but the number of neutrons ranges from 4 to 18, giving them atomic masses of 12 to 26. The "usual" isotope of Oxygen, O-16, has 8 neutrons. Very small amounts of O-17 and O-18, with 9 and 10 neutrons, exist naturally. All other Oxygen isotopes are short-lived and only exist because of reactions in a nuclear reactor, and usually only when a scientist's purpose is to create them. The most stable of these reactor-created isotopes of Oxygen is O-15, with a half life of about 2 minutes.

The book's 17 chapters are in 4 sections. The first covers the early years up to 1938 or '39, and the second, the development of induced fission and the Manhattan Project that led to both Uranium and Plutonium bombs. One of each was dropped on Japan in 1945, and I can't help wondering if this was as much for experimental reasons as military. The third section covers the cold war, and the fourth, the early spread and more recent fallback of nuclear power generation and the power plant disasters that led to its fall from grace.

I was surprised to find out (I should not have been) that the meltdown at Chernobyl was only one of at least 10 or 12, and became known because it was close enough to international borders that its fallout plume was easily detected in other countries. The others had been successfully kept secret, even though one or two may have exceeded Chernobyl in total radioactive materials released and environmental damage.

The most difficult chapter to read through was the one on Fukushima ("Blessed Island" in Japanese). It is the best documented of the "big three" of the world's imagination, the other two being Chernobyl and Three Mile Island. The narrative exposes the monumental stupidity of the "designers" and "engineers" (they do not truly deserve those titles), who chose a reactor design known to be flawed; who chose to put it on a coastline prone to tsunamis and against clear warnings by geologists, and also in one of the more earthquake-prone parts of Japan—which is more earthquake-prone as a country than almost any other—; who chose to place the backup generators for the cooling system in basements that were at or below sea level; and then the host of errors that were made in operational safety measures during the weeks and months prior to the disaster. Actually, this was a series of linked disasters that played out over half a year's time, and in some measure they are still being played out.

But just as I was sure the author would inveigh against continuing use of nuclear power, he produced a string of facts such as:

• The total death toll from nuclear power plant meltdowns, so far as is known, is 33,000 or less. This compares with 15,000 deaths over 30 years in the coal mining industry worldwide, and 20,000 in the petroleum industry.
• The atomic bombs dropped on Japan killed roughly 200,000-250,000 within the first half year (half of those in the first minutes). An equal number were killed by the tsunami of 2004 in the Indian Ocean. Roughly twice this many die yearly in America alone from smoking-related cancer and heart disease.
• A dam failure in China in 1975 killed 171,000.
• On a per-megawatt-hour basis, fossil fuels are 18 times as deadly as nuclear fuels.

This is why Nelson calls "Radiance", the totality of industries and products of radioactive elements and isotopes, the two-faced god, like Janus. To moderns, the apt analogy is a two-edged sword. One daren't touch it anywhere but the handle! Yet public opinion is so strong, and the ignorance of scientific principles so profound in both public and political spheres, that atomic energy is effectively dead in America and a number of other "developed" countries, at least for the next generation or two.

Here is some final food for thought I came across as I considered this post:

This illustration went around and around the Web after it was published late in 2011. It shows the excess radiation exposure people are expected to receive by living in the various Japanese prefectures. The red-toned one is Fukushima Prefecture, and the exposure is 0.25-0.50 µSv/h. That unit needs explaining:

Unit: µSv/h - micro-Sieverts/hour. Radiation toxicity begins to make itself evident above a total dose of about 500 mSv (500,000 µSv), or half a Sievert, and more severe affects appear after 1 Sievert. About one person in 18 is expected to develop cancer if exposed to 1 Sv total over an extended period—for example, 115 µSv/h for one year.

It is hardly risky to spend much time even in Fukushima Prefecture. Lifetime exposure under an excess dose of 0.50 µSv/h would be about 2/3 of a Sievert. However, there are a few focal areas near the destroyed power plant in which you'd be very sick after spending no more than a few hours. If you want the thrill of visiting a nuclear wilderness, though, nothing beats taking a "nuclear tourism" tour of the Chernobyl area, where one can look into lands that are said to be too radioactive for people to live, but where wildlife flourishes without human interference, and one can even take a short walk over ground that cannot, by law, be built upon for at least 10,000 years.

Countering the China syndrome

kw: book reviews, nonfiction, radiation, radioactivity

A couple of years ago, in answer to fears expressed by friends and relatives, I posted Uranium 101, to explain what we should fear and what we should not fear, about Uranium and the possible release of radiation in Japan after the earthquake and tsunami.

I am gratified to read a comprehensive summary and explanation of these matters in Radiaton: What it is, What You Need to Know, by Robert Peter Gale, M.D., and Eric Lax. The authors discuss the sources of background radiation, and the things we do that add extra radiation exposure, such as getting X-rays and CT scans, flying, and smoking. That's right, smoking increases exposure to radiation. Tobacco plants do not take up uranium from the soil, but the "daughter elements" radium (4 million times as radioactive as uranium) and polonium (5,000 times as radioactive as radium) do get into the tobacco leaves, and into cigarettes. If this really worries you, but you can't stop smoking, do this: the half life of polonium is 138 days, so just stockpile your smoking materials, write dates of purchase on the packages, and don't use them for 4 years. Then the polonium content will be less than 1/1000 of what it was when you bought it.

OK, back from digression. Americans living at sea level are exposed to 3-4 mSv (millisieverts) of radiation yearly. Higher elevations take us above some of the protective atmosphere, so nationwide, the average is about 6 mSv. When you fly in a jet plane at 36,000 ft, you are above 3/4 of the atmosphere, so more space radiation reaches you. However, now you are shielded from most of the radiation coming upward from the ground. Still, you receive a lot more radiation during each hour of flight than you get from the X-ray backscatter scanner at the airport. Better news: many airports are replacing the X-ray scanners with T-ray scanners, which cannot cause harm.

Many people are afraid of all kinds of radiant energy. The electromagnetic spectrum is very, very wide, and only about half of it (in logarithmic terms) is harmful. Too see how wide, we need to talk units. Two sets of units are used, wavelength and energy per photon. Wavelength is used for the longer, less energetic photons, and energy is used to discuss the higher energy, very short-wave photons. The "center" of the spectrum is visible light, and in this region, both units are used depending on the reason for discussing them. So let's start with visible light, and the near-visible regions of near infrared and near ultraviolet.

The limits of normal vision are considered to be at wavelengths of 400 nm at the blue end, and 700 nm at the red end. Actual visual response at these limits is about 0.4% of the response to yellow light near 580 nm. The unit nm is the nanometer, or a billionth of a meter. To convert to energy, the proportionality constant is 1,293.7 eV-nm, and we divide this number by the wavelength to get energy. So blue-limit light's energy per photon is 1,239.7/400 = 3.1 eV, and at the red limit, it is 1,239.7/700 = 1.77 eV. The eV is the electron-volt, the energy an electron has when accelerated by a 1-volt potential. Old CRT type TV sets used an electron gun with about 30,000 volts, so the electrons were hitting the front plate with an energy of 30,000 eV, usually shown as 30 KeV, for Kilo-eV. We'll get back to this.

Near-infrared (NIR) is typically considered to range from 700 to 5,000 nm, AKA 0.7-5 µ (microns; the "consistent" term micrometer hasn't really caught on). Near-ultraviolet (NUV) ranges from 400 to 280 nm, the range of UV that can easily pass through the atmosphere. It has two components, UVA and UVB, with a cutover at 315 nm. UVC that you may have read about is the germicidal UV used in hospitals, ranging down to about 240 nm, where the atmosphere blocks it even over short distances, such as across a room. The UVA-UVB cutoff has an energy of 3.94 eV. Organic chemical bonds have energies in this range, which makes UVA and UVB risky for our skin. The thinner ozone layer is letting through a little UVC from the Sun, also, which is why sunblock is needed more now than in the past. The energy of UVC is at least 4.43 eV per photon, and it can damage exposed skin quickly.

Energetic as these wavelengths may be, they are not ionizing radiation. That takes a lot more energy per photon. Although the C-C bonds in organic materials can be broken by UVC, that produces free radicals, not ions. True ionization needs at least 10 eV/photon, or a wavelength shorter than 124 nm. This is the boundary between Far UV and "soft" X-rays. The X-rays used by your dentist are generated by an electron beam hitting a tungsten anode at 70,000 volts. They have a range of energies peaking at about 40 KeV. These are called medium X-rays, while hard X-rays are in the range above 100 KeV. Such X-rays are used by industrial inspection X-ray machines.

Remember the CRT TV? It produces small amounts of rather soft X-rays at about 20-25 KeV. That's why parents used to tell their children to stay farther from the TV set. Today's flat-screen TV's, whether Plasma, LCD or LED, do not produce any X-rays.

Now, how about your cell phone? Can it cause cancer? While you are talking (not listening), the phone is signaling to the tower using about 1 watt of microwave radio. While "microwave" may sound scary, that just means it is at a wavelength shorter than the UHF band used for analog TV signals (channels 13-65), in the pre-cable days. Microwaves have wavelengths over a wide range, from 1 m to 1 mm. Let's convert the shortest wavelength (most energetic) to nm and check the eV formula: 1mm = 1 million nm, so 1,239.7/1,000,000 = 0.0012 eV per photon. This is much less energetic than visible light. You'd suffer more damage by shining a flashlight into the side of your head! By the way, T-ray scanners use a wavelength near 1 mm.

Other kinds of radio use even longer wavelengths, and their tiny photon energies are why this unit is not used in this range. The longest common frequency to which we are exposed is the 60Hz signal from AC power transmission, which has a wavelength of 5,000 km. Thus the range of non-ionizing radiation is between 5,000 km and about 500 nm, a range of 1 quadrillion to 1. Now let's look at higher energies than X-ray.

There is a big gap in the spectrum of natural radiation to which we are exposed, because of blocking by the atmosphere, and because common radioactive elements produce energetic particles starting at a rather high point, though typically at a low level. Three elements form the foundation of natural radiation in Earth materials, mostly rocks: Uranium, Thorium and Potassium.

First and foremost, we cannot avoid Potassium (symbol K). The human body contains 0.25% K. Thus, I weigh 200 lbs (91 kg), so my body contains half a pound of potassium, or about 0.23 kg. The radioactive isotope of potassium is K-40, and makes up 0.0118% of the total, or 0.027 g; just over 1/40th of a gram. That isn't much, and K-40 is weakly radioactive, with a half life of 1.28 billion years. But that 40th of a gram is about 4x10²⁰ atoms, of which nearly 7,000 decay each second. Now we get to energy. K-40 decays by the beta process, ejecting an electron or positron (it can do either, to become either Ca-40 or Ar-40, both of which are stable). The ejected particle has an energy of 1.3 or 1.5 MeV (million eV), some 1,000 times as energetic as a hard X-ray. It also produces energetic photons with an energy of 0.5 or 1.5 MeV. The beta particle stays in the body, while the gamma photon can exit, meaning that during a hug (or sleeping together) we receive some gamma radiation from our partner!

K-40 gamma radiation is near the low end of the range of natural radioactivity, but is not the lowest. Uranium and Thorium in the soil, particularly in areas with a lot of granite, produce energetic alpha particles, but these are absorbed by almost anything, such as a sheet of paper. A typical room with gypsum sheetrock contains a tenth of a gram of U and half as much Th, but their alpha radiation is stopped by the paper and the paint on the wall. Not so their gamma photons, which are actually in the hard X-ray region, at 48 KeV and 59 KeV respectively. Also, they have long half lives, 1.41 billion years for Th-232 and 4.51 billion years for U-238.

What about Radon? When U-238 emits an alpha particle, it becomes Th-234. That emits a beta particle (24 day half life) to become Pa-234 (Protactinium), and the chain continues. After a few more decays, Radium (Ra-226) is produced, which has a half life of 1,600 years. After an alpha emission, the next daughter element is Radon, specifically Rn-222, with a half life of 3.8 days. This is a gas, and is a concern everywhere there are soils derived from granitic rock (most of the U.S.). Radon is the primary cause of lung cancer in nonsmokers. Although it produces gamma radiation, with an energy of 500 KeV, it is the 5 MeV alpha particle, with nothing to stop it, that damages the lung. In sum, the ionizing range of radiations goes from about 10 eV to about 10 MeV, and there are cosmic rays with much higher energies. This is about a million-to-one range, a much smaller part of the entire spectrum than the non-ionizing range.

All this, a combination of salient facts from the book plus things I knew or dug out of the literature, set the stage. When you put everything together, people worldwide experience a background radiation level of 2.5-8 mSv. That is a combination of exposure to K, U and Th in soils and rock, to Rn in the air, to Ra in some rocks, and a contribution from solar radiation more-or-less blocked by the atmosphere and depending mainly on the elevation above sea level. That unit, milliSieverts, is a complex measure of the potential damage from ionizing radiation. The radiation of your cell phone is ZERO mSv, because it is not ionizing. A dental X-ray is in the range of 0.005 mSv, or about 0.1 mSv for a set of 18 over your full mouth. If you live in Florida, with little granite, and your background exposure is 3 mSv, you'd have to get 30 sets of dental full-mouth X-rays in one year to double your dose. Of course, that is skewed because most of it would be to your head, particularly if the dental technician puts a lead shield on you like mine does.

CT scans are another situation entirely. A chest-abdomen spiral scan totals 50-60 mSv, equal to 5-10 years of background radiation for most of us. This is the greatest radiation exposure most of us will ever have. When your doctor orders a CT scan, make sure it is for a good reason!

The authors of Radiation dwell much on what was learned from the casualties and survivors of the Hiroshima and Nagasaki nuclear explosions. This sets another baseline, the high end of survivable exposure. The LD50 (lethal dose for 50% of victims) for whole-body radiation dosage is 5 Sv or 5,000 mSv. That's only about 100 CT scans! However, that is a single-event dose; little is yet known about doses spread over years or decades. It seems the body can repair radiation damage up to a point.

The authors stress several times, when a doctor prescribes any kind of radiation beyond a simple X-ray, you need to ask what the exposure is, as compared to background (stated in mSv or in milli-Grays, which is equivalent). If the doctor can't state that, or won't, you need a different doctor! The doctor also should be able to explain the expected benefit and how it outweighs the risk of the radiation dose, whether from a CT scan, radiation applied to a cancer, or an ingested or injected radioisotope for some therapeutic or test purpose. This is a general rule, but is particularly important regarding such therapies and tests: if your doctor can't or won't explain, get a new doctor!

Finally, I have to tout nuclear power generation. The authors make it clear that we are much more likely to get radiation-induced cancer from coal burning power plants than from nuclear power plants. There are radioactive elements in coal, and they go right into the air when coal is burned. Also, the slag remaining from burnt coal contains heavy metals and other toxins, and these don't have a half-life like U or Ra, so they are toxic forever and ever. A nuclear power plant produces a few tons of high-level radioactive waste per year. A coal fired power plant produces hundreds or thousands of tons of toxic waste per year. The waste dump for a single coal plant could be used to store all the output from all U.S. nuclear plants for decades or centuries, and not run out of room. Just put the canisters on pallets on the ground, fence it off, and guard the stuff.

Really, we ought to be recycling spent uranium. 95% of its energy is still in there, just "poisoned" by the fission products. The problem isn't scientific; the science and technology are well known and safe. The problem is political. Even better, we ought to be using breeder reactors, to turn U-238, which won't "fizz", into Pu-239, which will. There's 140 times as much U-238 as there is U-235, the usual fuel. I suggest having the U.S. Navy oversee the design, construction and operation of nuclear power plants. They've been running aircraft carriers and submarines with nuclear power for more than half a century, and they seem to be able to do it without meltdowns or other accidents.

OK, I really like this book, and got quite inspired as you can see above. Without minimizing or distorting the risks, the authors make it clear that current fears about radiation are unfounded. Knowledge is the enemy of unwarranted fear. This book belongs on everybody's reading list.