Anyone who has the lightest familiarity with nuclear power knows that it is impossible to steal fuel from an operating reactor. Even assuming a terrorist knew how to shut it down, there is still the problem of very high level radiation within the reactor core that would be fatal in a matter of minutes for anyone who attempted to break in. (Our brave terrorist - pardon the oxymoron - would find this a very unpleasant way to enter paradise.)
The same goes for hijacking the spent-fuel truck or train on the way to the reprocessing plant. After storage for at least five years at the power plant site, the "spent" fuel is still highly radioactive and thermally quite hot. Hijacking 44,000-pound fuel containers - designed to smash into a concrete wall at 60 mph or fall onto a spike from thirty feet without rupturing - is a bit difficult to do surreptitiously.
This leaves us with raiding the reprocessing plant (bad idea) or stealing the fuel from shipments to the power plant (best bet). Assuming that the militants can make off with a huge truck, monitored as all valuable shipments are with global positioning electronics and probably guarded, and that no one notices this cargo with the huge radioactive symbols all over it, the hijackers must plan ahead to make sure their plutonium reclamation plant is near by. Typically the price tag on such a facility is in the hundreds of millions, or billions of dollars - and, of course, they've got to hide this construction from the prying eyes of swarms of government inspectors looking for something to inspect... or, even more difficult to avoid, the office-supply salesmen in the four surrounding counties.
Assuming the truck is hijacked and taken to the secret $100 million facility, the problems are just starting for our ill-intentioned thieves. Now they must cut up the fuel assemblies and dissolve them in nitric acid. After that, the chemical processes to separate the plutonium from the uranium are devilishly tricky - in part because an almost-certainly fatal criticality accident can occur quite easily when the plutonium is in a liquid form. But let's assume that our "clever" terrorists are successful in refining out the plutonium and have shaped it for a bomb. Two big problems:
The first is obtaining the explosive charges necessary to "implode" a sphere of plutonium in on itself - essentially taking a hollow globe and compressing it down to a golf or tennis-ball-sized solid... well, almost solid. Regular explosive won't work, as the charge must have different characteristics as it "burns" to maintain the shape of the shock wave that is doing the compressing. Then there is the matter of the initiator, or trigger - the device that produces a stream of neutrons to start the reaction inside a one-tenth microsecond envelope when they are needed. This was considered by the Manhattan Project team (approximately 130,000 personnel, including arguably the best physicists and engineers in the world) as one of the most difficult items to design. Polonium 210 and beryllium must be mixed thoroughly - but this must occur within the aforementioned 0.0000001-second time frame. But let's suppose they are able to do all this. Sorry, still no cigar.
For you see, problem two, the plutonium they liberated from the Imperialist Yankee Running Dogs is not suitable for making a decent bomb. Since BWR and PWR reactors "burn" fuel slowly, Pu239 is created not only from the U238, but also from the Pu240 isotope. While not a fissionable isotope (which wouldn't make much difference in small concentrations), it is a spontaneous neutron emitter, which bodes ill for aspiring bomb makers. Even a very small amount of Pu240 is sufficient to throw off the timing of the necessary bomb reaction by starting it before the implosion is complete - causing the bomb to fizzle. Oh, you'll get an explosion of sorts - perhaps sufficient to flatten a city block or two - but not as awful as what you could do with ammonium nitrate and a little fuel oil, a la Oklahoma City. (The 1947 Texas City blast - where 512 were killed - was also a fertilizer explosion, which didn't require any plutonium at all.)
Terrorists are, in my mind, among the most despicable of humankind. But this isn't to say they are stupid. If they want to kill people and spread fear, there are a lot of easier ways to do this, and they know it. Poisoning the water supply, blasting a hole in a dam, setting oil storage facilities afire when the wind is blowing toward a heavily populated area - the list goes on and on. But building a dud bomb from hijacked plutonium isn't one of them.
Showing posts with label uranium. Show all posts
Showing posts with label uranium. Show all posts
Tuesday, April 12, 2016
Monday, April 11, 2016
Where the Terrorists Have Already Won
In 1978, Jimmy Carter reneged on the opening of a reprocessing plant that was nearing completion in Barnwell, South Carolina. This facility was to take "spent" fuel rods from power reactors owned by the utilities, dissolve them in acid, then separate the uranium and plutonium from the contaminants that would "poison" and eventually stop the chain reaction. The highly radioactive progeny of the energy-producing reactions - amounting to some 1% or 2% of the volume - would be disposed of by any one of a number of perfectly safe methods. The fuel portion would then be reformed into uranium or "MOX" pellets for insertion into fuel assemblies.
Hold on. Could one infer from this that these "spent" fuel elements contain in excess of 90% of their intial fuel? Yes, one could. Is this what we plan to bury under Yucca Mountain? Precisely.
Does this make sense to you? It certainly doesn't to the English, French, Japanese, Russians, and others who think we are absolutely nuts for planning to bury unbelievable amounts of readily obtainable energy. But it made sense to the Carter administration, and even though Reagan reversed the decision, there were no corporate takers who were willing to risk their shareholders' money on a project that could be changed by the whim of a government with a history of caving in to the slightest pseudo-environmentalist pressure. And there would certainly be pressure - since, as we "know," all radiation is dangerous, since any gamma ray could cause cancer... even though the odds against it are 30 quadrillion to one.
What was the reason - excuse, really - that the Carter administration used to stop reprocessing? It was the threat of terrorism. Let's consider briefly the problems from the standpoint of terrorists who are planning a heist of plutonium, with which they intend to make a bomb.
Hold on. Could one infer from this that these "spent" fuel elements contain in excess of 90% of their intial fuel? Yes, one could. Is this what we plan to bury under Yucca Mountain? Precisely.
Does this make sense to you? It certainly doesn't to the English, French, Japanese, Russians, and others who think we are absolutely nuts for planning to bury unbelievable amounts of readily obtainable energy. But it made sense to the Carter administration, and even though Reagan reversed the decision, there were no corporate takers who were willing to risk their shareholders' money on a project that could be changed by the whim of a government with a history of caving in to the slightest pseudo-environmentalist pressure. And there would certainly be pressure - since, as we "know," all radiation is dangerous, since any gamma ray could cause cancer... even though the odds against it are 30 quadrillion to one.
What was the reason - excuse, really - that the Carter administration used to stop reprocessing? It was the threat of terrorism. Let's consider briefly the problems from the standpoint of terrorists who are planning a heist of plutonium, with which they intend to make a bomb.
Friday, April 8, 2016
And Finally...
Many of us think in terms of our present energy situation and don't consider what benefits our world would have if the LNT did not cloud the minds of those who could do great works - if allowed to do so by the regulators. While the American Nuclear Society is still on the fence in regard to scrapping the LNT and recognizing the possibilities of hormesis, Gregg M. Taylor, the editor-in-chief of the organization's magazine - Nuclear News - wrote an absorbing editorial entitled, "We have met the solution, and it is us."
In this monograph, he noted that one of California's big problems - echoed in many countries around the world - is the availability of water for agricultural irrigation. Water from the Colorado River is coveted by all and is a constant source of political turmoil. But what if we built nuclear desalination plants, he asks, strategically located along the coast? They could be pollution free - with guppy rights properly observed.
One might wonder how this could dovetail into Dr. Cohen's extraction of uranium from the sea - surely there is a synergistic connection here as part of the desalination process could well be the initial step in obtaining the metal. How much more habitable - for people like you and me - would the Earth become if our deserts could be irrigated... at no cost except the premature use of the nuclear energy in uranium and thorium. They are going to lose their energy over time anyway - we're just appropriating it for our short-term use. Besides, a quarter of the uranium and two-thirds of the thorium would still have its energy when the sun flakes out on us in eight or ten billion years.
Editor Taylor also touches on another touchy subject: toxic wastes. Noting that most of us remember "disintegrators" from our sci-fi days, he observes that it takes only sufficient energy - which can be provided readily by clean nuclear sources - to reduce the most horrible kinds of toxic waste into its constituent atoms, which would totally lose their identity and could be recombined as the purest substances possible.
Let your mind roam free for a moment. What scourge of mankind might not be alleviated by sufficient energy availability?
***
If man is to advance to another higher plateau - past the industrial and information revolutions - it can be done only in conjunction with an unencumbered access to energy. Otherwise, we are dooming generations to untold misery and suffering.
In this monograph, he noted that one of California's big problems - echoed in many countries around the world - is the availability of water for agricultural irrigation. Water from the Colorado River is coveted by all and is a constant source of political turmoil. But what if we built nuclear desalination plants, he asks, strategically located along the coast? They could be pollution free - with guppy rights properly observed.
One might wonder how this could dovetail into Dr. Cohen's extraction of uranium from the sea - surely there is a synergistic connection here as part of the desalination process could well be the initial step in obtaining the metal. How much more habitable - for people like you and me - would the Earth become if our deserts could be irrigated... at no cost except the premature use of the nuclear energy in uranium and thorium. They are going to lose their energy over time anyway - we're just appropriating it for our short-term use. Besides, a quarter of the uranium and two-thirds of the thorium would still have its energy when the sun flakes out on us in eight or ten billion years.
Editor Taylor also touches on another touchy subject: toxic wastes. Noting that most of us remember "disintegrators" from our sci-fi days, he observes that it takes only sufficient energy - which can be provided readily by clean nuclear sources - to reduce the most horrible kinds of toxic waste into its constituent atoms, which would totally lose their identity and could be recombined as the purest substances possible.
Let your mind roam free for a moment. What scourge of mankind might not be alleviated by sufficient energy availability?
- Floods and hurricanes? Better materials requiring more energy, high dikes - both a function of available energy.
- Starvation? Hydroponics from desalinated water.
- Locusts? Airplanes, chemicals, huge nuclear flyswatters (just kidding).
***
If man is to advance to another higher plateau - past the industrial and information revolutions - it can be done only in conjunction with an unencumbered access to energy. Otherwise, we are dooming generations to untold misery and suffering.
Sunday, April 3, 2016
The Cornucopia of Nuclear Power
You will remember from chapter 21 that we have two neutrons, on average, emitted whenever a U235 atom undergoes fission - or "splitting." One of these is necessary to fission another atom to keep the chain reaction going. But what happens to all of those second neutrons? Some of them, as mentioned, are absorbed by the structure of the reactor or by the control rods, which slide in and out of the reactor to keep the reaction at - or just very slightly above - the critical point. But others smash into, and are captured by, the plentiful U238 atoms that make up from 95% to 96.5% of the fuel rod contents. When this happens, a truly miraculous thing takes place: This practically worthless material is transformed into one of the most concentrated sources of energy on Earth - or in the universe for that matter - plutonium 239, and element so evil that it was named for the god of the underworld. (Not really, but that's what some would have you believe.) [Plutonium was named in honor of the discovery of the planet Pluto, just as neptunium and uranium were named for Neptune and Uranus.]
This happens in every one of the world's 500 power reactors, plus thousands of research reactors, every day they are in operation. In fact, a sizable fraction (up to about 30%) of electrical energy generated by a power plant comes from this plutonium, which arises as a natural consequence of the uranium fission reaction - without any effort on our part - and supplements the scarce U235 fuel.
Some reactors, however, are designed to intentionally make plutonium. If it is to be used in bombs, it is normally made in a reactor with another modulator - such as the carbon-modulated reactor at Chernobyl. A reactor designed specifically to make only fuel-grade plutonium is called a breeder reactor, since new fuel is "bred" from an almost worthless byproduct of the refining cycle. [Breeder technology seems to be on hold for a couple of reasons: (1) in the prevailing anti-nuclear climate, few entrepreneurs or speculators are willing to make investments in nuclear power for fear of laws that can make their investment instantly worthless; and (2) at the present time there is a glut of plutonium available from the dismantlement of nuclear weapons.]
Are we speculating here on new technology like "fusion" power? Hardly.
The first reactor ever to produce electric power from nuclear energy was a "liquid metal fast breeder reactor" known as the EBR-I. (By the way, liquid metal means that the coolant was not our old friend water, but liquid sodium; fast means that it used "fast neutrons," not the slowed-down, moderated variety.) Designed by physicist Walter Zinn in 1944, his brainchild went critical at 11 am, December 20, 1951 - producing the first steam in history produced by man-made nuclear heat. Like the Manhattan reactor in Chicago and the SLOWPOKE reactor in Canada, EBR-I was not designed to produce electrical power but to prove the concept of fuel breeding (which it did along with its successor, EBR-II). [Declared a national landmark in 1966, the EBR-I is open to the public from mid June to mid September. Located eighteen miles southeast of Arco, Idaho, on Highway 26, visitors must be at least sixteen years old (too much neutron violence?) and U.S. citizens (fear of spies who might steal this technology?).]
The EBR-II had "on the spot reprocessing," which reprocessed 35,000 fuel elements between 1965 and 1969. But the facility was not without problems: the fence around it kept out the coyotes, causing the rabbit population to outbreed the reactor.
Does the ERB-II sound a little familiar? It should since it has another name we used in chapter 21 - the Integral Fast Reactor (IFR).
While many U.S. politicians have never heard of breeder technology, Europeans have. Sadly, "Green" activists there have been successful in shutting them down or keeping them from ever starting up.
This happens in every one of the world's 500 power reactors, plus thousands of research reactors, every day they are in operation. In fact, a sizable fraction (up to about 30%) of electrical energy generated by a power plant comes from this plutonium, which arises as a natural consequence of the uranium fission reaction - without any effort on our part - and supplements the scarce U235 fuel.
Some reactors, however, are designed to intentionally make plutonium. If it is to be used in bombs, it is normally made in a reactor with another modulator - such as the carbon-modulated reactor at Chernobyl. A reactor designed specifically to make only fuel-grade plutonium is called a breeder reactor, since new fuel is "bred" from an almost worthless byproduct of the refining cycle. [Breeder technology seems to be on hold for a couple of reasons: (1) in the prevailing anti-nuclear climate, few entrepreneurs or speculators are willing to make investments in nuclear power for fear of laws that can make their investment instantly worthless; and (2) at the present time there is a glut of plutonium available from the dismantlement of nuclear weapons.]
Are we speculating here on new technology like "fusion" power? Hardly.
The first reactor ever to produce electric power from nuclear energy was a "liquid metal fast breeder reactor" known as the EBR-I. (By the way, liquid metal means that the coolant was not our old friend water, but liquid sodium; fast means that it used "fast neutrons," not the slowed-down, moderated variety.) Designed by physicist Walter Zinn in 1944, his brainchild went critical at 11 am, December 20, 1951 - producing the first steam in history produced by man-made nuclear heat. Like the Manhattan reactor in Chicago and the SLOWPOKE reactor in Canada, EBR-I was not designed to produce electrical power but to prove the concept of fuel breeding (which it did along with its successor, EBR-II). [Declared a national landmark in 1966, the EBR-I is open to the public from mid June to mid September. Located eighteen miles southeast of Arco, Idaho, on Highway 26, visitors must be at least sixteen years old (too much neutron violence?) and U.S. citizens (fear of spies who might steal this technology?).]
The EBR-II had "on the spot reprocessing," which reprocessed 35,000 fuel elements between 1965 and 1969. But the facility was not without problems: the fence around it kept out the coyotes, causing the rabbit population to outbreed the reactor.
Does the ERB-II sound a little familiar? It should since it has another name we used in chapter 21 - the Integral Fast Reactor (IFR).
While many U.S. politicians have never heard of breeder technology, Europeans have. Sadly, "Green" activists there have been successful in shutting them down or keeping them from ever starting up.
Sunday, March 27, 2016
Enter the Atom
Let's return for a short graduate course from Hormesis U. about "splitting the atom."
We've already seen that U238 is an isotope of uranium with a half-life of 4.5 billion years. [I realize I said I was going to refer to isotopes in the form of 238U or uranium 238. But U235 and U238 are such commonly used abbreviations to denote these isotopes that I will be using them in this chapter.]
With a lump of this element and the proper instruments, you would find there is another isotope, U235, which amounts to only 0.7% of the total mass. Yet it is this tiny fraction that makes uranium the tremendous source of safe and reliable energy - not to mention the fearful master - that it has become.
U235, like its more plentiful sibling, is an alpha emitter - but has a considerably shorter half-life... a mere 3,800,000 years, meaning that it was considerably more plentiful a billion or so years ago. [U235 is sometimes referred to as "actinium" or "uranoactinium."] It, along with plutonium 239 and U233, are the only isotopes that are fissionable - a phenomenon described below.
Under normal conditions, we can expect to see a U235 atom occasionally decay into an isotope of thorium and a helium nucleus (an alpha particle) similar to all radioactive isotopes experiencing alpha decay. ["Occasionally" takes on a new meaning in the atomic world. Our roughly penny-sized gram of U235 would experience approximately 80,000 nuclear disintegrations per second.]
But let us suppose that a stray neutron smacks into the nucleus of an unsuspecting U235 atom. If the energy of the neutron is within a certain range, our U235 target atom fissions, that is, breaks into pieces. [This was first observed by an unbelieving Lise Meitner in December 1938. She had observed barium, with an atomic number of 56, arising when she bombarded "actinium" with neutrons.]
It usually splits into two roughly equal parts, and most important, ejects about two neutrons. Obviously no atom could eject or emit about two neutrons, but, on average, that is what a fissioning U235 atom sends out of its nucleus.
Imagine, then, one of these neutrons hitting another U235 atom, which emits two neutrons with at least one of these splitting another atom... and so on, and so on. As you have no doubt already figured out, this is what is known as a chain reaction. When the ratio of fissioned atoms in successive generations is equal to one - that is, when one splitting atom causes exactly one more to split - the reaction is said to go critical. What happens to the other neutrons? They either escape from the volume of uranium, or they are absorbed - either unintentionally by structural material, or purposely by control rods made of boron, aluminum, cadmium, or several other neutron-absorbing materials - in order to keep the reaction under control (that is, to keep it from going super-critical). Does a super-critical reaction cause a bomb-like explosion? Not at all; if it did, bomb development by the Manhattan project would have been relatively simple rather than requiring the best theoretical physics minds on two continents. But super-criticality is no picnic. It causes rapid rises in fission reactions, leading to very high temperatures that cause structural damage, torrents of neutrons, and "steam explosions." Bad, yes, but still light years away from the mushroom-shaped cloud.
Let's look at a few different types of reactors, with an eye for those that might allow decentralization of electric power generation.
We've already seen that U238 is an isotope of uranium with a half-life of 4.5 billion years. [I realize I said I was going to refer to isotopes in the form of 238U or uranium 238. But U235 and U238 are such commonly used abbreviations to denote these isotopes that I will be using them in this chapter.]
With a lump of this element and the proper instruments, you would find there is another isotope, U235, which amounts to only 0.7% of the total mass. Yet it is this tiny fraction that makes uranium the tremendous source of safe and reliable energy - not to mention the fearful master - that it has become.
U235, like its more plentiful sibling, is an alpha emitter - but has a considerably shorter half-life... a mere 3,800,000 years, meaning that it was considerably more plentiful a billion or so years ago. [U235 is sometimes referred to as "actinium" or "uranoactinium."] It, along with plutonium 239 and U233, are the only isotopes that are fissionable - a phenomenon described below.
Under normal conditions, we can expect to see a U235 atom occasionally decay into an isotope of thorium and a helium nucleus (an alpha particle) similar to all radioactive isotopes experiencing alpha decay. ["Occasionally" takes on a new meaning in the atomic world. Our roughly penny-sized gram of U235 would experience approximately 80,000 nuclear disintegrations per second.]
But let us suppose that a stray neutron smacks into the nucleus of an unsuspecting U235 atom. If the energy of the neutron is within a certain range, our U235 target atom fissions, that is, breaks into pieces. [This was first observed by an unbelieving Lise Meitner in December 1938. She had observed barium, with an atomic number of 56, arising when she bombarded "actinium" with neutrons.]
It usually splits into two roughly equal parts, and most important, ejects about two neutrons. Obviously no atom could eject or emit about two neutrons, but, on average, that is what a fissioning U235 atom sends out of its nucleus.
Imagine, then, one of these neutrons hitting another U235 atom, which emits two neutrons with at least one of these splitting another atom... and so on, and so on. As you have no doubt already figured out, this is what is known as a chain reaction. When the ratio of fissioned atoms in successive generations is equal to one - that is, when one splitting atom causes exactly one more to split - the reaction is said to go critical. What happens to the other neutrons? They either escape from the volume of uranium, or they are absorbed - either unintentionally by structural material, or purposely by control rods made of boron, aluminum, cadmium, or several other neutron-absorbing materials - in order to keep the reaction under control (that is, to keep it from going super-critical). Does a super-critical reaction cause a bomb-like explosion? Not at all; if it did, bomb development by the Manhattan project would have been relatively simple rather than requiring the best theoretical physics minds on two continents. But super-criticality is no picnic. It causes rapid rises in fission reactions, leading to very high temperatures that cause structural damage, torrents of neutrons, and "steam explosions." Bad, yes, but still light years away from the mushroom-shaped cloud.
Let's look at a few different types of reactors, with an eye for those that might allow decentralization of electric power generation.
Saturday, February 6, 2016
Radon: Scourge or Blessing for Mankind?
Government was tightening industrial radioactive emission standards to ridiculously low levels, while demanding that homeowners modify their homes to the point where radon doses to the average citizen were hundreds of times greater than the levels dictated to nuclear workers.
Radon is the heaviest of the "noble gases," so named because it - like its cousins neon, argon, krypton, and xenon - does not react with other elements to form compounds. It is radon's "nobility" that minimizes its effects on the body, since it is mostly a transient that is breathed in and then expelled without any chemical reaction taking place. When radon decays in the body, however, it spawns a series of short half-life progeny that are not only chemically reactive with tissue, but are - as we would suspect from their half-lives - also highly radioactive.
[When uranium decays (which isn't very often with a half-life of 4.5 billion years), the products of the decay go through four more stages (taking a couple of million years) until radium is formed. With a half-life of 1,600 years, radium 226 decays into radon gas with a half-life of 3.8 days. The daughters of radon are polonium 218, lead 214, bismuth 214, polonium 214 - and a couple of others. The aforementioned have very short half-lives and are therefore highly radioactive.]
Hazard to Miners?
For years, radon has been thought to be a hazard to miners, and a special confusing unit of activity - the Working Level (WL) - was derived to measure the danger. [One WL is the activity of air containing 100 pCi (3.7 Bq) of radon in equilibrium with its daughters (which, by the way, virtually never happens in the real world) per liter of air. For an approximation, a Working Level Month (WLM) is equivalent to a one-time whole body dose of about 300 mrem (0.3 cGy).]
Recently, however, as evidence of radiation hormesis has emerged, the jury is back out to deliberate a reconsideration of radon's guilt. It is now recognized that other carcinogens - in particular, the particulates suspended in the air of all mines and, more recently, the fumes from diesel engines - were present, but never considered. Radon was assumed to be the carcinogenic culprit, a theory that appears now to be based on flimsy circumstantial and anecdotal evidence.
A related re-evaluation of lung cancer in the Joachimsthal mining community [a famous mine in Czechoslovakia] noted that victims were invariably "pensioners," i.e. miners (not their unexposed, above-ground cohorts) who had made it to a retirement age, which was about ten years longer than their life expectancy. One might easily speculate that the cancer was caused by microscopic dust lodged in the lungs, and the miners' long lives a beneficial product of radon gas. [One of Europe's most famous health spas is Bad Gastein near Salzburg, Austria, which advertises "air with the highest radon content in Europe." The activity of its water is noted in Table 6, in this blog's entry on Monday, January 25, "Specific Activities."]
There has also been a piece of the puzzle right under our noses.
Radon gives its dose of mixed radiation primarily to the bronchial epithelium (fancy scientific words for "windpipe"), hence one would expect cancers caused by radon to be concentrated in this area. Au contraire! The miners' cancers are deep in the lungs [Nobel Laureate Rosalyn Yalow, Radiation and Society, Interdisciplinary Science Reviews, 16, 4, 1991], similar to the cancers caused by the South African amphibole-type asbestos [not to be confused with the common, domestic serpentine type of asbestos, which has not been shown to cause disease], used in ships because of its resistance to brine, acids, and oils.
It is difficult not to see the parallel between non-degradable asbestos fibers in the lungs and non-soluble silica particulates found in most mining environments.
Radon is the heaviest of the "noble gases," so named because it - like its cousins neon, argon, krypton, and xenon - does not react with other elements to form compounds. It is radon's "nobility" that minimizes its effects on the body, since it is mostly a transient that is breathed in and then expelled without any chemical reaction taking place. When radon decays in the body, however, it spawns a series of short half-life progeny that are not only chemically reactive with tissue, but are - as we would suspect from their half-lives - also highly radioactive.
[When uranium decays (which isn't very often with a half-life of 4.5 billion years), the products of the decay go through four more stages (taking a couple of million years) until radium is formed. With a half-life of 1,600 years, radium 226 decays into radon gas with a half-life of 3.8 days. The daughters of radon are polonium 218, lead 214, bismuth 214, polonium 214 - and a couple of others. The aforementioned have very short half-lives and are therefore highly radioactive.]
Hazard to Miners?
For years, radon has been thought to be a hazard to miners, and a special confusing unit of activity - the Working Level (WL) - was derived to measure the danger. [One WL is the activity of air containing 100 pCi (3.7 Bq) of radon in equilibrium with its daughters (which, by the way, virtually never happens in the real world) per liter of air. For an approximation, a Working Level Month (WLM) is equivalent to a one-time whole body dose of about 300 mrem (0.3 cGy).]
Recently, however, as evidence of radiation hormesis has emerged, the jury is back out to deliberate a reconsideration of radon's guilt. It is now recognized that other carcinogens - in particular, the particulates suspended in the air of all mines and, more recently, the fumes from diesel engines - were present, but never considered. Radon was assumed to be the carcinogenic culprit, a theory that appears now to be based on flimsy circumstantial and anecdotal evidence.
A related re-evaluation of lung cancer in the Joachimsthal mining community [a famous mine in Czechoslovakia] noted that victims were invariably "pensioners," i.e. miners (not their unexposed, above-ground cohorts) who had made it to a retirement age, which was about ten years longer than their life expectancy. One might easily speculate that the cancer was caused by microscopic dust lodged in the lungs, and the miners' long lives a beneficial product of radon gas. [One of Europe's most famous health spas is Bad Gastein near Salzburg, Austria, which advertises "air with the highest radon content in Europe." The activity of its water is noted in Table 6, in this blog's entry on Monday, January 25, "Specific Activities."]
There has also been a piece of the puzzle right under our noses.
Radon gives its dose of mixed radiation primarily to the bronchial epithelium (fancy scientific words for "windpipe"), hence one would expect cancers caused by radon to be concentrated in this area. Au contraire! The miners' cancers are deep in the lungs [Nobel Laureate Rosalyn Yalow, Radiation and Society, Interdisciplinary Science Reviews, 16, 4, 1991], similar to the cancers caused by the South African amphibole-type asbestos [not to be confused with the common, domestic serpentine type of asbestos, which has not been shown to cause disease], used in ships because of its resistance to brine, acids, and oils.
It is difficult not to see the parallel between non-degradable asbestos fibers in the lungs and non-soluble silica particulates found in most mining environments.
Sunday, January 31, 2016
A Very Short History of Radiation Hormesis
The extremely tall people on Niue Island (averaging height 6'6") receive 10 times more radiation from the soil than the world average. [Eugaster, Subradiation experiments concerning the concept of the natural radiation background, Aerospace Medicine, 35, 524, 1964.]
Why, you might logically ask, was the hormesis phenomenon not discovered until some eighty years after Roentgen, Becquerel, and the Curies made their contributions to radiation science? Why was there not an earlier Professor Luckey? [Professor Luckey is credited with coining the term "Radiation Hormesis" from his 1981 book Hormesis with Ionizing Radiation.]
Actually there was of sorts, and he, oddly enough, was also a professor at the University of Missouri. In 1896, Professor W. Shrader inoculated guinea pigs with the diphtheria bacillus. [Shrader, W. Experiments with X-rays upon germs. Electrical Engineering, 22, 170, 1896.]
The group exposed to X-rays prior to inoculation survived; the unexposed cohort died within twenty-four hours. Shrader, in the same series of experiments, was apparently the first person to discover that "Roentgen Rays" could be used to kill germs.
During the early twentieth century, radiation was used for a variety of experimental therapies, but the doses were generally far above hormetic levels and may well have caused more harm than good. Patent medicines such as "Radithor" (more on this in chapter 24) were popular, with single doses having nearly a million times the daily radium intake allowed by current government regulators. Hundreds of thousands of vials of elixirs were consumed without any widespread harm occurring and with a sizable number of "miracle cures" being reported. Few controls, however, were employed to scientifically assess the actual worth of the treatments leaving one to believe that most of these "cures" may have been either the product of advertising hype or a placebo effect.
Medical research wasn't the big draw for world-class physicists. We might remember that in the early days of radiation experimentation important discoveries were being made almost daily, while health considerations - except, possibly, for the annoying, minor and superficial skin "beta burns" - were considered to be of no consequence. The doses of radiation these unprotected experimenters received are estimated to exceed by thousands of times the maximums under which today's nuclear industry workers are allowed to continue on the job.
Madame Curie, discoverer of both polonium and radium, offers a good example of the "non-standards" of the day. [In 1516, a silver lode was discovered in St. Joachim's Dale (Joachimsthal), which was - naturally - confiscated by the government of Count von Schlick. Coins minted from this mine were known as Joachimsthalers, which (for obvious reasons) came to be known as thalers - in English, dollars. It was from this mine that the Curies obtained pitchblende - an ore rich in uranium and its daughters, radium and polonium.]
It is anecdotal that whenever Marie Sklodowska [in case you were curious why she named her first discovery for Poland] Curie walked into a room, electroscopes immediately discharged. [Gold is so malleable that it can be pressed into leaves less than 1/10,000 of an inch thick. If you hang two pieces of leaf in an air-filled jar, with provision to charge both - you have an electroscope. Charging the leaves with the same polarity causes them to "push apart" and, because they are so light, the electrostatic "pushing" force exceeds the gravitational force that would cause them to "droop" into a vertical position. Such devices were used to assay the content of uranium ores - not from the non-penetrating alpha radiation of the uranium, but from the accumulated daughters of which the gamma ray emitting radium was a significant component. Air, when ionized, is a conductor that discharged the electroscope at a rate proportional to the amount of ionizing radiation present.]
It is almost certain that she had an enormous lung burden of radium - the element she was extracting from uranium ore - which took quite a bit of patience, since there are only about 0.003 grams of radium per ton of ore. Madam Curie died almost certainly from the effects of long-term and extremely high doses of radiation. Yet, at age sixty-six, she still exceeded by ten years the life expectancy of her day.
Later in the century, the subject of hormesis would have doubtlessly been trifling compared to other matters. From August 1939 - when a letter from Albert Einstein was delivered to Franklin Roosevelt recommending the development of an atomic bomb - until the end of World War II, the focus of virtually the entire nulcear physics community became the Manhattan project. (This venture, equivalent in size to the total automotive industry at that time, is described in fascinating detail in The Making of the Atomic Bomb [Richard Rhodes, Simon & Schuster, New York, 1986].)
Certainly the scientists were aware of potential dangers from radiation - especially the highly penetrating neutrons from "atomic piles" - but these risks were minimal, compared with the reality of thousands of deaths from the war every day. Concerns about low-level radiation - either harmful or beneficial - weren't even on the radar scope.
Interestingly, the only health physics experiment I've ever come across that occurred during the Manhattan project was indicative of radiation hormesis:
"In 1943, a group of [radiation scientists] on the Manhattan District Project were worried about the unknown toxicity of uranium. They grew a colony of rats in an atmosphere laden with sufficient uranium dust to kill them fast (the Manhattan Project didn't have time for fancy radiobiologists). As a control, a similar colony breathed clean air. After several months, nothing happened, but eventually the rats lived out their natural lifespans, with one surprise: the first health physics experiment demonstrated that rats who breathed uranium dust lived longer and were happier (i.e., had a better reproductive history) than normal rats. Not a tumor in the bunch." [From a letter by Marshall Brucer, M.D. to Time magazine (from the files of Petr Beckmann).]
During this period there are reports of relatively minor medical experimentation to determine the effect of ionizing radiation on the healing of wounds. The exposure levels, however, were high (1 Gy or 100 rem) - suggesting its use as a bactericide. The availability of antibiotics in 1942, and the post-Hiroshima bombing concerns over high-level dangers, caused a loss of interest in research of this nature by the end of World War II.
After the war, the Japanese cities of Hiroshima and Nagasaki became laboratories for research on the effects of radiation on humans. But the focal point was on the high-dose subjects - in particular on their excess cancers and the possible mutational effects on children. When low-dose victims showed beneficial health effects, the data were ignored as being anomalies (a fancy scientific words for "it doesn't fit in with what we're expecting").
Luckey addresses this subject:
"Statistical analysis of observed data was missing in many reports of experiments involving low doses of ionizing radiation. Most of the reports simply indicated that an unexpected phenomenon had been observed, but the researchers failed to pursue it systematically... Any unexpected result was rejected by the 95% rule: One experiment in each twenty was accepted as a variant. Closer inspection showed this was a consistent result; it usually occurred in the group exposed to the least radiation, the only one in the hormetic range. Hormetic data were ignored because they did not fit the models of the zero thesis." [Radiation Hormesis, p. 45.]
When someone really writes a history of radiation hormesis, the first "official" recognition of the phenomenon will go to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in a 1994 report "Adaptive Responses to Radiation in Cells and Organisms":
"Manifestations of the adaptation described in mammals after exposure to low doses of radiation include accelerated growth rate in the young, increase in reproductive ability, extended life-span, stimulatory effects on the immune system, and a lower than expected incidence of spontaneous tumors."
You might want to read that again.
Why, you might logically ask, was the hormesis phenomenon not discovered until some eighty years after Roentgen, Becquerel, and the Curies made their contributions to radiation science? Why was there not an earlier Professor Luckey? [Professor Luckey is credited with coining the term "Radiation Hormesis" from his 1981 book Hormesis with Ionizing Radiation.]
Actually there was of sorts, and he, oddly enough, was also a professor at the University of Missouri. In 1896, Professor W. Shrader inoculated guinea pigs with the diphtheria bacillus. [Shrader, W. Experiments with X-rays upon germs. Electrical Engineering, 22, 170, 1896.]
The group exposed to X-rays prior to inoculation survived; the unexposed cohort died within twenty-four hours. Shrader, in the same series of experiments, was apparently the first person to discover that "Roentgen Rays" could be used to kill germs.
During the early twentieth century, radiation was used for a variety of experimental therapies, but the doses were generally far above hormetic levels and may well have caused more harm than good. Patent medicines such as "Radithor" (more on this in chapter 24) were popular, with single doses having nearly a million times the daily radium intake allowed by current government regulators. Hundreds of thousands of vials of elixirs were consumed without any widespread harm occurring and with a sizable number of "miracle cures" being reported. Few controls, however, were employed to scientifically assess the actual worth of the treatments leaving one to believe that most of these "cures" may have been either the product of advertising hype or a placebo effect.
Medical research wasn't the big draw for world-class physicists. We might remember that in the early days of radiation experimentation important discoveries were being made almost daily, while health considerations - except, possibly, for the annoying, minor and superficial skin "beta burns" - were considered to be of no consequence. The doses of radiation these unprotected experimenters received are estimated to exceed by thousands of times the maximums under which today's nuclear industry workers are allowed to continue on the job.
Madame Curie, discoverer of both polonium and radium, offers a good example of the "non-standards" of the day. [In 1516, a silver lode was discovered in St. Joachim's Dale (Joachimsthal), which was - naturally - confiscated by the government of Count von Schlick. Coins minted from this mine were known as Joachimsthalers, which (for obvious reasons) came to be known as thalers - in English, dollars. It was from this mine that the Curies obtained pitchblende - an ore rich in uranium and its daughters, radium and polonium.]
It is anecdotal that whenever Marie Sklodowska [in case you were curious why she named her first discovery for Poland] Curie walked into a room, electroscopes immediately discharged. [Gold is so malleable that it can be pressed into leaves less than 1/10,000 of an inch thick. If you hang two pieces of leaf in an air-filled jar, with provision to charge both - you have an electroscope. Charging the leaves with the same polarity causes them to "push apart" and, because they are so light, the electrostatic "pushing" force exceeds the gravitational force that would cause them to "droop" into a vertical position. Such devices were used to assay the content of uranium ores - not from the non-penetrating alpha radiation of the uranium, but from the accumulated daughters of which the gamma ray emitting radium was a significant component. Air, when ionized, is a conductor that discharged the electroscope at a rate proportional to the amount of ionizing radiation present.]
It is almost certain that she had an enormous lung burden of radium - the element she was extracting from uranium ore - which took quite a bit of patience, since there are only about 0.003 grams of radium per ton of ore. Madam Curie died almost certainly from the effects of long-term and extremely high doses of radiation. Yet, at age sixty-six, she still exceeded by ten years the life expectancy of her day.
Later in the century, the subject of hormesis would have doubtlessly been trifling compared to other matters. From August 1939 - when a letter from Albert Einstein was delivered to Franklin Roosevelt recommending the development of an atomic bomb - until the end of World War II, the focus of virtually the entire nulcear physics community became the Manhattan project. (This venture, equivalent in size to the total automotive industry at that time, is described in fascinating detail in The Making of the Atomic Bomb [Richard Rhodes, Simon & Schuster, New York, 1986].)
Certainly the scientists were aware of potential dangers from radiation - especially the highly penetrating neutrons from "atomic piles" - but these risks were minimal, compared with the reality of thousands of deaths from the war every day. Concerns about low-level radiation - either harmful or beneficial - weren't even on the radar scope.
Interestingly, the only health physics experiment I've ever come across that occurred during the Manhattan project was indicative of radiation hormesis:
"In 1943, a group of [radiation scientists] on the Manhattan District Project were worried about the unknown toxicity of uranium. They grew a colony of rats in an atmosphere laden with sufficient uranium dust to kill them fast (the Manhattan Project didn't have time for fancy radiobiologists). As a control, a similar colony breathed clean air. After several months, nothing happened, but eventually the rats lived out their natural lifespans, with one surprise: the first health physics experiment demonstrated that rats who breathed uranium dust lived longer and were happier (i.e., had a better reproductive history) than normal rats. Not a tumor in the bunch." [From a letter by Marshall Brucer, M.D. to Time magazine (from the files of Petr Beckmann).]
During this period there are reports of relatively minor medical experimentation to determine the effect of ionizing radiation on the healing of wounds. The exposure levels, however, were high (1 Gy or 100 rem) - suggesting its use as a bactericide. The availability of antibiotics in 1942, and the post-Hiroshima bombing concerns over high-level dangers, caused a loss of interest in research of this nature by the end of World War II.
After the war, the Japanese cities of Hiroshima and Nagasaki became laboratories for research on the effects of radiation on humans. But the focal point was on the high-dose subjects - in particular on their excess cancers and the possible mutational effects on children. When low-dose victims showed beneficial health effects, the data were ignored as being anomalies (a fancy scientific words for "it doesn't fit in with what we're expecting").
Luckey addresses this subject:
"Statistical analysis of observed data was missing in many reports of experiments involving low doses of ionizing radiation. Most of the reports simply indicated that an unexpected phenomenon had been observed, but the researchers failed to pursue it systematically... Any unexpected result was rejected by the 95% rule: One experiment in each twenty was accepted as a variant. Closer inspection showed this was a consistent result; it usually occurred in the group exposed to the least radiation, the only one in the hormetic range. Hormetic data were ignored because they did not fit the models of the zero thesis." [Radiation Hormesis, p. 45.]
When someone really writes a history of radiation hormesis, the first "official" recognition of the phenomenon will go to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in a 1994 report "Adaptive Responses to Radiation in Cells and Organisms":
"Manifestations of the adaptation described in mammals after exposure to low doses of radiation include accelerated growth rate in the young, increase in reproductive ability, extended life-span, stimulatory effects on the immune system, and a lower than expected incidence of spontaneous tumors."
You might want to read that again.
Sunday, January 24, 2016
100 Picocuries - That's a Lot! (Or is it?)
Since most Americans have no idea what danger might lurk in a glass of water with 200 picocuries per liter, we are at the mercy of those who might use this lack of knowledge to their political advantage.
Imagine sitting in a chair three feet away from a gram of an unknown radioactive metal, about the size of a penny, on the floor in front of you. Should you be concerned? I know I would be - at least until I knew more about what it was. Obviously we would be interested in what type of radiation was being emitted. It if were alpha or beta particles, there would be no problem as the 3 feet of air would stop any significant amount. But what if it were gamma rays? Then we would want to know just how "active" the source was - with the activity of a radioactive source being measured in the number of atoms that disintegrate every second.
Let's suppose our one gram of material is radium, specifically 226Ra. Would you care to guess the number of disintegrations per second? A mere 37,000,000,000 (37 billion)! This, by the way, is the number of disintegrations defined as 1 curie, or 1 Ci, since the curie is defined as the activity of one gram of radium. You needn't run away, but you might not want to hang around. If it were one gram of cesium 134, a quick exit would be advisable. [Cesium 134 is a gamma and beta emitter that has about fifteen times the activity of the Goian cesium 137, which is only a beta emitter.]
The curie, a United States (USA) unit, is still in common use but is gradually being replaced by the International Standard (SI) becquerel or Bq, which is defined as one disintegration per second. Obviously, then, 1 curie is equal to 37 billion Bq - not exactly the easiest conversion constant to work with, especially when you have to go the other way: 1 Bq = 2.7 x 10^-11 Ci = 27 pCi.
A few elements of interest and their specific activities - that is, their activity per gram - are given in Table 5.
Note that the half-life of the low activity 238U is very long - 4.5 billion years, while one-half the very active 131I isotope is gone in 8.04 days. We would expect this, since there are a finite number of atoms in a gram of any substance, and if the rate of decay (i.e., the activity) is high, it will take less time for the substance to lose its radioactivity. This is verified by the very low relative activity of the primordial radionuclides such as thorium, uranium and potassium, which have extremely long half-lives since these were presumably created at the same time as the Earth - estimated by most cosmologists as some 4.6 billion years ago. The shorter half-life isotopes - say a mere few million years or so - are long gone, although some are being replaced by decay products of the low activity elements.
Imagine sitting in a chair three feet away from a gram of an unknown radioactive metal, about the size of a penny, on the floor in front of you. Should you be concerned? I know I would be - at least until I knew more about what it was. Obviously we would be interested in what type of radiation was being emitted. It if were alpha or beta particles, there would be no problem as the 3 feet of air would stop any significant amount. But what if it were gamma rays? Then we would want to know just how "active" the source was - with the activity of a radioactive source being measured in the number of atoms that disintegrate every second.
Let's suppose our one gram of material is radium, specifically 226Ra. Would you care to guess the number of disintegrations per second? A mere 37,000,000,000 (37 billion)! This, by the way, is the number of disintegrations defined as 1 curie, or 1 Ci, since the curie is defined as the activity of one gram of radium. You needn't run away, but you might not want to hang around. If it were one gram of cesium 134, a quick exit would be advisable. [Cesium 134 is a gamma and beta emitter that has about fifteen times the activity of the Goian cesium 137, which is only a beta emitter.]
The curie, a United States (USA) unit, is still in common use but is gradually being replaced by the International Standard (SI) becquerel or Bq, which is defined as one disintegration per second. Obviously, then, 1 curie is equal to 37 billion Bq - not exactly the easiest conversion constant to work with, especially when you have to go the other way: 1 Bq = 2.7 x 10^-11 Ci = 27 pCi.
A few elements of interest and their specific activities - that is, their activity per gram - are given in Table 5.
Table
5 – Specific Activities of Selected Elements
|
|||
Element
|
Curies
|
Becquerels
|
Half-Life
|
Thorium 232
|
0.000000166
|
4,316
|
14.05 billion years
|
Uranium 238
|
0.000000333
|
12,300
|
4.47 billion years
|
Potassium 40
|
0.00000722
|
267,200
|
1.27 billion years
|
Radium 226
|
1
|
37 billion
|
1,620 years
|
Strontium 90
|
139
|
5,143 billion
|
28.8 years
|
Cesium 134
|
1,290
|
47,900 billion
|
2.06 years
|
Iodine 131
|
124,000
|
4,588 trillion
|
8.04 days
|
Tellurium 133
|
113,000,000
|
4,200,000 trillion
|
12.4 minutes
|
Note that the half-life of the low activity 238U is very long - 4.5 billion years, while one-half the very active 131I isotope is gone in 8.04 days. We would expect this, since there are a finite number of atoms in a gram of any substance, and if the rate of decay (i.e., the activity) is high, it will take less time for the substance to lose its radioactivity. This is verified by the very low relative activity of the primordial radionuclides such as thorium, uranium and potassium, which have extremely long half-lives since these were presumably created at the same time as the Earth - estimated by most cosmologists as some 4.6 billion years ago. The shorter half-life isotopes - say a mere few million years or so - are long gone, although some are being replaced by decay products of the low activity elements.
Friday, January 22, 2016
Waste 'n' Time
Uh, oh. I'm afraid I've kind of painted myself into a corner here by minimizing the "problem" of nuclear wastes. If I give it short shrift, it will appear that I'm avoiding the subject. On the other hand, while the matter of nuclear wastes is somewhat afield from our general topic, there is a connection that might be of interest.
The only danger even attributed to nuclear wastes is that of causing cancer in future generations that are too stupid not to bit into a glassified chunk of power-plant waste. As we shall see, there is a threshold below which - even for those future glass munchers - there is no fear of increased cancer risk. But even if there weren't such a threshold, there are a number of issues regarding nuclear wastes that have been ignored in the media's misreporting of the subject that you should know about.
Why then, you may ask, are there hundreds or thousands of government- (read "taxpayer-") supported scientists busy writing reports on Yucca Mountain? I suggest there may be three reasons: (1) they don't know - or, more than likely, don't care - that low-level radiation is not harmful; (2) it beats having to get a real job; or (3) grants to study the mating habits of the Zambian sweat bee have already been taken.
The only danger even attributed to nuclear wastes is that of causing cancer in future generations that are too stupid not to bit into a glassified chunk of power-plant waste. As we shall see, there is a threshold below which - even for those future glass munchers - there is no fear of increased cancer risk. But even if there weren't such a threshold, there are a number of issues regarding nuclear wastes that have been ignored in the media's misreporting of the subject that you should know about.
- More than 95% of the long half-life "waste" in nuclear fuel is not waste at all, but uranium and plutonium that may be reprocessed into fresh fuel assemblies. Most other industrialized nations do just this, as our government promised the utilities, but the Carter administration reneged on the agreement. (More about this later.)
- Among the "wastes" that anti-nuclear activists are eager to bury are valuable medical radionuclides that are produced at high cost in specialty reactors. As in the case of the reprocessable fuel, the baby is being thrown out with the bath water.
- The most sensible way to eliminate the unusable wastes from reprocessed fuel (which about to about 1% of their volume) is to dilute it a few millionfold and pour it down the drain, or to dump it into ocean abysses where there is no biological activity. Man's puny efforts at creating radionuclide wastes are dwarfed by the enormous amounts existing in nature. There are, for example, 36 billion curies of rubidium 87 and 380 billion curies of potassium 40 in the oceans, almost all of which will still be there when the few million curies of man's wastes have long since decayed to undetectable amounts.
Why then, you may ask, are there hundreds or thousands of government- (read "taxpayer-") supported scientists busy writing reports on Yucca Mountain? I suggest there may be three reasons: (1) they don't know - or, more than likely, don't care - that low-level radiation is not harmful; (2) it beats having to get a real job; or (3) grants to study the mating habits of the Zambian sweat bee have already been taken.
Tuesday, January 19, 2016
Radioactive Isotopes
****
Table 2 - Some Common Radioactive Isotopes
3H = Tritium = Luminous watch dials
14C = Carbon 14 = Radioactive dating
60Co = Cobalt 60 = Food irradiation
40K = Potassium 40 = Biological tracer
99Tc = Technetium 99 = Medical diagnosis
131I = Iodine 131 = Thyroid-function diagnosis and treatment
238Pu = Plutonium 238 = Spacecraft power supplies, pacemakers
241Am = Americium 241 = Smoke alarms
****
All of the elements heavier than lead in the periodic table have multiple isotopes, and all are naturally radioactive; most of them decay into one of the stable lead isotopes. Uranium and thorium have the greatest number of isotopes - uranium with 22 isotopes and thorium with 28 - though most of these are not naturally occurring. As a rule of thumb, elements are happiest when they have about the same number of protons and neutrons. When there is a sizable difference, they tend to decay until there isn't.
So, what about this radioactive business? How does it work? How dangerous is it? And for how long?
A very interesting subject: Don't miss the next chapter.
Subscribe to:
Posts (Atom)