I have read about various plans and schemes to pay for the present or for expanded medical care, and they all will involve rationing by available money, time, doctors, or equipment. While you are reading this blog, try to imagine how you yourself would design a medical care plan, with the proviso that you must operate behind the "veil of ignorance" that John Rawls popularized in his book "A Theory of Justice". That is, you must design a medical plan that would seem fair to you before you know your position in this self-designed society. Will you be an affluent white male living in an expensive suburb, or will you be a poor pregnant non-white teenage girl with a single mother?
Right now, although many Americans declaim against "Socialized Medicine", I know of no Medicare patient who would not like Medicare to continue. (And why not, since they get back much more in medical services than they paid in Medicare premiums.) In addition, their middle-class children want Medicare to continue as well, so they can use their own savings to pay for their own children's college education rather than for their own parents' medical expenses. The tobacco companies briefly had an ad showing how cigarette smoking benefited the country on the bottom line: If a smoker dies before age 65, the government pockets all his/her Medicare premiums and pays out not one dime.
BTW former president Bush was economically unsound when he said that the Emergency Room was always available to patients without doctors. By law, the ER's must accept all comers, regardless of their insurance status. Now if you tell your family doctor you have a headache, he will make several suggestions and then tell you to come in one or two days if you are not feeling better. This all involves little expense. But if an unknown patient comes to the ER with a headache, he will usually get a set of blood tests, an EKG, a pregnancy test if female, a CT scan of the brain, possible a carotid Doppler study of his carotid arteries, and then a consult with a neurologist who in turn may order or do a brain MRI and/or a spinal tap. The ER does not know you the way your family doctor does, including facts not usually written in the medical record: are you an alarmist, a hypochondriac, a stoic, a cocaine user, etc. The fact remains that NO DOCTOR EVER GOT SUED FOR DOING A TEST or ordering a specialty consult, but only for not doing the test. So the best way for an ER doctor to minimize the chances of a malpractice suit is to do as many tests as can be thought of (including a temporal artery biopsy). An article in Archives in Internal Medicine several months ago which evaluated the cost of working up dizziness in the ER was over $20,000, and the cost in the family doctor's office was only a fraction of that. The jury doesn't ever want to hear the defense that the result of a test was unlikely to be useful if the patient died or was seriously damaged.
Let me give you some examples of the rationing of medical care in this and other countries. Medicare only pays psychiatrists 2/3 of the fee for an internist for the same amount of time in a visit---I guess they feel that if you are only a little crazy it doesn't count. Your friendly drug management company has a "preferred" list of drugs for various maladies, because they do bundle deals with the manufacturers, so one company may say that Nexium is the preferred stomach-acid blocking drug, while the other prefers Aciphex and a third prefers Prevacid. All three drugs have the same end point, but it is highly unlikely that the same patient will benefit equally well from all three. So the doctor has to spend a lot of time (= non-reimbursed monetary expense) explaining that in this patient Allegra works as an anti-histamine,and Claritin does not. The company either agrees (surprise and hooray!), or disagrees, whereupon the patient has to decide to pay the lesser price for the drug that does not work so well, or the higher price for the drug that does. Medicare also rations the number of visits to a physical therapist per month for a given musculoskeletal condition.
I have a good friend in Vancouver, Canada. He developed angina and needed CABG, or cardiac bypass surgery. Unfortunately, the hospital his doctor admitted to had an allotted ration of 150 open-heart surgeries per month. He had to wait from mid-January to Mid March for his open heart surgery. Fortunately he survived to have it. One year Canada decided to cap the annual salary (calculated by the number of patient visits) of all general practitioners. The result was that all GP's stopped practice by early or mid-November, because why should they work for free?
In England, the National Health Service does not pay for kidney transplants, or for chronic dialysis over the age of 55. So if you have kidney failure, you may end up flying to India to buy a kidney (for about $10,000) to be transplanted into you by an English-trained doctor. The National Health Service also does not admit certain legal drugs to be sold in the country, including some made by British firms, because they do not want to pay for it (such as the inhaled anti-viral that shortened the course of the flu).
In Germany, each doctor has a panel of patients, and is paid every three months for the number of patients plus the number of their visits. The state also pays for all drugs. But if the doctor's patients average drug cost is too high in one calendar quarter, the doctor's salary is cut the next quarter!
We are hard up against the fact that the demand for medical care can never be saturated, and that the technical cost of medical care is driving costs through the roof, not the doctor's fees. An artificial hip can cost $8500, before the surgeon's fee, the OR fee, the hospital room fee, etc. Technology costs money, but it works and saves lives. It also extends the useful working life of patients, but no economists calculates that if open-heart surgery cost $40,000, but the patient lived another 15 years and contributed $750,000 in income taxes the country gained. OTOH, try to flip the argument, and say that we could save $2B/year by banning open-heart surgery, and I don't think there would be any takers.
First we had Xrays, which saved lives, at a cost of approx. $100 each. Then we developed CT scans, which sees much more than Xrays and saves more lives, but because of all the computers involved costs approx. $250/scan. Now we have MRI's, which save even more lives again, but which costs approx. $750 because of the huge magnets involved. No one would want to do without these wonderful devices, but no one really wants to pay for them.
Until 10 years ago premature babies born with weights of less than 4 pounds generally did not survive. Now with neonatal intensive care units, etc, we can save babies weighing as little as one pound. They may spend three months in the NeoICU at a cost of $1M, but they survive.
Finally medical economists and budget planners think that we could save a ton of money if we got patients with chronic diseases to take better care of themselves. The problem is that 50% of these chronic diseases were caused by or made worse by the patients precisely because they don't care that much to take care of themselves. I have never, with all the backup help and clinics in the world, ever gotten a ,male diabetic to lose weight to improve his sugar control. People don't exercise as much as they should. (The exception to better diet and more exercise is any male who has a heart attack----they become rapid believers in healthy living.) Very few humans are willing to anticipate what may happen to their bodies more than 10 seconds in the future, so we don't worry about the current cigarette, or the unprotected sex, or driving without seatbelts, because none of these actions will cause a foreseeable problem in the next 10 seconds. Insofar as dietary changes are concerned, if you cannot get your two year old to eat spinach or your teen-age anorectic to eat at all, how do we get anyone to eat properly? Videos of children playing volleyball in camp show that overweight campers move less on the court than others, but we don't know which came first, the overweight or the decreased athletic activity. I am certain that each and every one of my readers can recall several unhealthy (if not illegal) activities that they themselves did.
So what is the answer? No one knows. What is the ideal percentage of our GNP that should be spent on medical care? No one knows. But everyone is certain that when it comes to their own health care or that of their families, then no expense is too great, and so once again we have the conflict of microbehavior vs. macrobehavior, which is precisely the problem with containing medical costs. (Recall that after the 2008 bank crashes, the government's desired microbehavior was for individuals to save, while the governments desired macrobehavior was for the country to spend its way out of the recession.) As a physician my professional commitment is 100% to my patient, and not to overall economic expense (even if malpractice suits did not exist). And expect no real help from Congress or your State Legislatures: They have voted themselves the finest medical plans that exist, all of which are cost-free to them in Congress and in most states (as are their pensions as well).
Thursday, April 21, 2011
Sunday, April 10, 2011
MMWR Recommendations for Adult Vaccinations in 2011
http://www.cdc.gov,
/mmwr/preview/mmwr.html/mm6004a10.htm
/mmwr/preview/mmwr.html/mm6004a10.htm
Sunday, April 3, 2011
Radiation, Radiation Poisoning, and Radiation Sickness
Two years ago I wrote a blog on some of the medical effects of radiation. In view of the recent problems with nuclear reactors in Japan, I thought I should add several comments, including a discussion of the lethality of different kinds of radiation, the half-life of a radioactive element, and possible means of protection. This blog will therefore discuss the chemistry, physics and medical effects of radioactivity. I have had some direct experience with this, since in the past I have worked at Oak Ridge National Labs as well as Columbia's Nevis Cyclotron, and I have done medical research for two summers in the radiation physics department of a teaching hospital. I also have had experience with patients exposed to radiation, but I am still not permitted to talk about it.
Let's begin with a few simple facts: Every atom is composed of a nucleus containing neutrons and protons, surrounded by concentric shells of electrons. The chemistry of an atom depends on the number of electrons, and the physics of the atom depends on the number of neutrons and protons in the nucleus. In free space, a neutron will decay in less than 15 minutes into a proton, an electron, and an anti-neutrino, but inside the nucleus quantum rules often forbid this. The atomic number of an element is equal to the number of protons in the nucleus (and hence the number of external electrons), and the atomic weight is approximately equal to the number of protons plus the number of neutrons. An element, which by definition has a defined number of protons in the nucleus, can have various numbers of neutrons. The different nuclei with the same number of protons but differing numbers of neutrons are called isotopes of each other.
Some isotopes of elements are naturally radioactive, such as Carbon-14, or Oxygen 17. But since Carbon-12 (which comprises over 99.9% of natural carbon) and Carbon-14 both have the same number of electrons, they appear chemically identical to living biochemical systems and are chemically incorporated into their cells and tissues. Therefore every living animal with carbon has some natural radioactivity. We know the natural C14/C12 ratio in the world, and this, coupled with the known half-life of Carbon-14 of 5600 years, allows us to carbon-date ancient bones and tools. We can apply the same principles to date the age of rocks and the earth, using uranium/lead ratios, since all uranium eventually decays into lead. However, ALL isotopes of the elements above a certain atomic number are naturally radioactive, so that there is no harmless form of thorium,radium,uranium, plutonium, radon, etc., and if you are in close enough proximity to one of these elements for a sufficient length of time, it will be fatal.
Ordinary water contains two atoms of hydrogen, and one of oxygen: H2O. Heavy water contains two atoms of deuterium (a hydrogen isotope with one proton and one neutron in the nucleus) and one of oxygen: D2O. Although they are similar chemically, if you drink enough heavy water you will die, since water passes through cell membranes by a process called diffusion, which is physical, and not chemical. Because heavy water absorbs neutrons more efficiently than ordinary water, it is often used in a nuclear reactor.
There are three types of radiation that can harm you. The first is free electrons, also called beta rays (for historical reasons). Electrons have very little penetrating power because they are charged, and interact rapidly with your skin. Therefore usually the worst that beta rays can do to you is to give you a burn, and simple clothing will generally stop them. However, your thyroid gland takes up iodine avidly and rapidly, to make thyroid hormone. Most reactors will, if breached release radioactive iodine (I-131) into the atmosphere, such as happened at Chernobyl as well as Japan. Unfortunately, if I-131 falls on food and you ingest it, it will be concentrated in your thyroid gland. Although I-131 is a low-energy beta ray emitter, you can easily swallow enough to make you gradually hypothyroid, or, especially in children, cause the development of cancer of the thyroid in a few years. This is why we recommend daily doses of KI, or potassium iodide, to children who are exposed to such radioactivity, to block the uptake of I-131. (We first realized the danger of radiation to children's thyroid glands when children and adolescents who received radiation with gamma rays to treat their acne developed thyroid cancer 10 to 20 years later.) Similarly, breached reactors release radioactive strontium, which is chemically similar to calcium in that they are both divalent cations. Therefore, if there is radioactive strontium on the grass, and the cows eat it, it will chemically replace some of the calcium in the cow's milk, and when you drink this milk the radioactive strontium will be taken up and concentrated in your bones, and then it can damage your bone marrow, and/or cause leukemia.
The second "radiation" that can cause damage is generally not thought of as radiation, but it is released in large numbers and high energies in runaway reactors, and that is neutrons. They are electrically neutral, so they have incredible penetrating power. They are preferentially absorbed and give up their energy to hydrogen atoms, which is why water is a doubly useful substance for cooling reactors. Cadmium is also an excellent neutron absorber, and cadmium rods can be used to SCRAM a runaway reactor. Unfortunately, over 60% of our body is water, and our brains are especially sensitive. There is no portable way to measure neutrons, (such as a Geiger counter for gamma rays), and there is no way to measure or detect how much damage the neutrons have done to your body, or what your total neutron exposure was. When I worked at the cyclotron lab, we all had radiation badges to measure our monthly exposure to gamma rays. But there was only a long string of yellow plastic rope stretching from one side of the cyclotron to the lab wall, with a floor sign underneath:"Do Not Approach Closer Than 10 Feet When the Cyclotron is in Operation".We all respected that sign.
The third radiation, and usually the most lethal, is gamma rays. These are photons, or "pieces of light". Their individual energy has a huge range, and the shorter the wavelength, the greater the energy. Thus radiowaves with wavelengths of kilometers are harmless, microwaves can be used to heat water, infrared waves can be used to heat rooms, ultraviolet rays will give you a sunburn or worse, and shorter wavelength rays such as X-rays can be lethal or give you radiation poisoning (which is probably why the dentist or hospital X-ray technician goes into the other room when he/she takes your x-rays---they don't want the exposure), and you aren't even given a radiation badge to measure the exposure to gamma rays you just received.
We have no way to measure the amount of radiation your body absorbed, or how much energy particular tissues (heart, brain, bone marrow) absorbed. We can only guess, since we just don't know. We think we know the safety limits for hospital radiation treatment of cancer, and we know that the old treatment of polycythemia vera with oral radioactive phosphorus caused bone marrow cancers and leukemias later, but we don't know precise doses. We really don't even know if radiation exposure increases your risk of getting cancer linearly, in that each exposure adds to the risk of the previous one, or of there is a threshold dose of radiation below which there is no risk. We do know that in acute radiation exposure you can die in 48 hours or 48 weeks. We do know that the most rapidly dividing cells are preferentially killed by gamma rays, so that the bone marrow and the lining of your gut are especially sensitive. We do know that there can be delayed burn-scar tissue results, such as fibrosis of the lungs, or constrictive pericarditis (of the heart).We know that radiation sickness can affect every organ system of the body, but we can't reverse or treat it, except to support the patient's vital signs, and hope that death from overwhelming infection or cancer does not ensue. We also know that developing embryos are exquisitely sensitive to the damaging effects of radiation.
Now as to radioactivity and reactors themselves. The natural radioactivity of the trans-thorium elements provides the heat in the earth that keeps the core liquid and the earth's surface warm. Without natural radioactivity, the energy from sunlight would not be enough to keep us from freezing to death. Now since uranium emits heat when it radioactively decays, it needs to be constantly cooled in a reactor, which is why the naked exposure of uranium-embedded zirconium rods created so much heat that it boiled the surrounding water, energized the freeing of hydrogen from water, and then exploded the free hydrogen which then burned in the presence of the free oxygen also liberated. So a naked core is an extreme heat emergency, as well as a radioactive one.
You can design a nuclear reactor that can never go critical. This is the type that is installed in nuclear subs. In a reactor, free neutrons are allowed to bombard uranium atoms. These then fission,. releasing on the average 2.5 neutrons per uranium atoms struck. If each neutron then splits a uranium atom, then two more atoms are split, and 5 more neutrons released. If this happens rapidly enough, it is a self-sustaining generator of energy (and then converted to heat via giant water boilers)., and we say that the reactor has "gone critical", and we have a chain reaction. We adjust the depth of cadmium rods in the reactor to control the rate of reaction, and if the reaction goes supercritical, we rapidly lower the cadmium rods into the rector to dampen it. I should mention that this reaction occurred naturally at least once in the past, about 2,000,000,000 years ago in Oklo, Gabon, West Africa, where the uranium isotope ratios demonstrate that there was a critical mass of uranium that started to run away, and was stopped only by its own production of radioactive xenon, which is a excellent neutron absorber.
The half-life of a radioactive isotope is the amount of time it takes half of a given number of radioactive isotopes to decay (and, hopefully into a non-radioactive product, which is the case for Carbon-14, but not for Uranium-235, Uranium -238, or Plutonium-239). I should mention that radioactive cesium, which has a very long half life and is used in hospitals as a source of radiation, as also produced by runaway reactors. The half-life is not related to the radiation danger of the isotope, but the number of radioactive daughter products certainly is, like the production of the radioactive gas radon from the decay of uranium. BTW, did you know that all marble is naturally slightly radioactive?
I think that you can see that the only safe act is total avoidance, and perhaps the carrying of personal radiation badges, to be checked once a month.If you suspect a radioactive fallout, get rid of your clothes, and shower immediately, and carefully wash all food before eating. I would assume that all government warnings minimize the danger, just as they told the terminal cancer patients in 1947 in whom they injected radioactive phosphorous and other substances that it would cause them no danger (since they were dying anyway, and then the government autopsied their bodies to find out what it could about the deposition in and effects of radiation on the body). Or when they permitted sailors to stand on the decks of their ships and have radioactive debris be showered on them after the H-bomb test at Bikini and Einewetok atolls.
BTW, a reactor is scrammed by releasing the clamps holding cadmium rods out of the nuclear core of the reactor, and let gravity pull the rods in as rapidly as possible. For one midwest reactor, the blueprints were distributed upside down, and because of atomic secrecy, the workmen knew very little of the ultimate purpose of their construction. Luckily, before the reactor was run up to full power to test the SCRAM operation, someone noticed that the cadmium rods were inserted from the bottom!
But at least we are avoiding 4 stupidities caused by insufficient knowledge of the dangers of radiation:
a) we no longer handle radioactive samples with our bare hands
b) we no longer use radioactive thorium salts to remove hair in the armpits
c) we no longer paint the numbers on watches that glow in the dark with radium-based paint, and have the painters moisten and sharpen the brush tips with their lips and thereby deposit radium salts into their mouths
d) we no longer rush over as children to the shoe store fluoroscope to stand and put our feet in the xray-fluoroscope to see how well our feet fit into our shoes
How much natural or man-made radioactive exposure is safe? No one really knows. We can sometimes, for a given energy level of gamma rays, estimate the LD50, which is the total time exposure after which 50% of exposed humans will die. But this is only an estimate, and only for one energy level. We also have no way of predicting how much exposure to Xrays and natural radioactivity is necessary to increase your risk of cancer in a given organ by 1%. There are estimates of the risk of inducing breast cancer after 30 years of annual mammograms, but these are only estimates, as is the stated "safe" level of radon, a radioactive gas. In fact all radioactive safety levels are guesstimates arrived at by compromise by a committee, and have never been verified, except for accidental exposure to a runaway chain reaction, such as happened to one scientist in Los Alamos who was working with two clumps of a radioactive element and let them approach each other too closely.
In case you think any of the above is an exaggeration, let me tell you about one incident. Shortly after 9/11, many of the upscale shopping malls were equipped with radiation detectors at their entrances. Several years ago, a male cardiac patient had a (radioactive) stress-thallium test, which involves injecting a small dose of radioactive thallium into your bloodstream when you are near peak exercise, and then scanning you with a radiation detector to see the distribution of blood to your heart when you are exercising. You then sit there for four hours, and they re-scan you to see the distribution of blood to your heart when you are at rest. An hour after this test was finished, so we are talking about what happened 5 hours after then man was injected, he went to meet his wife at the shopping mall in Short Hills, New Jersey. The residual radiation in his body triggered the radiation detectors, and the entire mall was shut down and evacuated, and everyone examined with a hand-held Geiger counter, which is how the authorities discovered what had happened.
Let's begin with a few simple facts: Every atom is composed of a nucleus containing neutrons and protons, surrounded by concentric shells of electrons. The chemistry of an atom depends on the number of electrons, and the physics of the atom depends on the number of neutrons and protons in the nucleus. In free space, a neutron will decay in less than 15 minutes into a proton, an electron, and an anti-neutrino, but inside the nucleus quantum rules often forbid this. The atomic number of an element is equal to the number of protons in the nucleus (and hence the number of external electrons), and the atomic weight is approximately equal to the number of protons plus the number of neutrons. An element, which by definition has a defined number of protons in the nucleus, can have various numbers of neutrons. The different nuclei with the same number of protons but differing numbers of neutrons are called isotopes of each other.
Some isotopes of elements are naturally radioactive, such as Carbon-14, or Oxygen 17. But since Carbon-12 (which comprises over 99.9% of natural carbon) and Carbon-14 both have the same number of electrons, they appear chemically identical to living biochemical systems and are chemically incorporated into their cells and tissues. Therefore every living animal with carbon has some natural radioactivity. We know the natural C14/C12 ratio in the world, and this, coupled with the known half-life of Carbon-14 of 5600 years, allows us to carbon-date ancient bones and tools. We can apply the same principles to date the age of rocks and the earth, using uranium/lead ratios, since all uranium eventually decays into lead. However, ALL isotopes of the elements above a certain atomic number are naturally radioactive, so that there is no harmless form of thorium,radium,uranium, plutonium, radon, etc., and if you are in close enough proximity to one of these elements for a sufficient length of time, it will be fatal.
Ordinary water contains two atoms of hydrogen, and one of oxygen: H2O. Heavy water contains two atoms of deuterium (a hydrogen isotope with one proton and one neutron in the nucleus) and one of oxygen: D2O. Although they are similar chemically, if you drink enough heavy water you will die, since water passes through cell membranes by a process called diffusion, which is physical, and not chemical. Because heavy water absorbs neutrons more efficiently than ordinary water, it is often used in a nuclear reactor.
There are three types of radiation that can harm you. The first is free electrons, also called beta rays (for historical reasons). Electrons have very little penetrating power because they are charged, and interact rapidly with your skin. Therefore usually the worst that beta rays can do to you is to give you a burn, and simple clothing will generally stop them. However, your thyroid gland takes up iodine avidly and rapidly, to make thyroid hormone. Most reactors will, if breached release radioactive iodine (I-131) into the atmosphere, such as happened at Chernobyl as well as Japan. Unfortunately, if I-131 falls on food and you ingest it, it will be concentrated in your thyroid gland. Although I-131 is a low-energy beta ray emitter, you can easily swallow enough to make you gradually hypothyroid, or, especially in children, cause the development of cancer of the thyroid in a few years. This is why we recommend daily doses of KI, or potassium iodide, to children who are exposed to such radioactivity, to block the uptake of I-131. (We first realized the danger of radiation to children's thyroid glands when children and adolescents who received radiation with gamma rays to treat their acne developed thyroid cancer 10 to 20 years later.) Similarly, breached reactors release radioactive strontium, which is chemically similar to calcium in that they are both divalent cations. Therefore, if there is radioactive strontium on the grass, and the cows eat it, it will chemically replace some of the calcium in the cow's milk, and when you drink this milk the radioactive strontium will be taken up and concentrated in your bones, and then it can damage your bone marrow, and/or cause leukemia.
The second "radiation" that can cause damage is generally not thought of as radiation, but it is released in large numbers and high energies in runaway reactors, and that is neutrons. They are electrically neutral, so they have incredible penetrating power. They are preferentially absorbed and give up their energy to hydrogen atoms, which is why water is a doubly useful substance for cooling reactors. Cadmium is also an excellent neutron absorber, and cadmium rods can be used to SCRAM a runaway reactor. Unfortunately, over 60% of our body is water, and our brains are especially sensitive. There is no portable way to measure neutrons, (such as a Geiger counter for gamma rays), and there is no way to measure or detect how much damage the neutrons have done to your body, or what your total neutron exposure was. When I worked at the cyclotron lab, we all had radiation badges to measure our monthly exposure to gamma rays. But there was only a long string of yellow plastic rope stretching from one side of the cyclotron to the lab wall, with a floor sign underneath:"Do Not Approach Closer Than 10 Feet When the Cyclotron is in Operation".We all respected that sign.
The third radiation, and usually the most lethal, is gamma rays. These are photons, or "pieces of light". Their individual energy has a huge range, and the shorter the wavelength, the greater the energy. Thus radiowaves with wavelengths of kilometers are harmless, microwaves can be used to heat water, infrared waves can be used to heat rooms, ultraviolet rays will give you a sunburn or worse, and shorter wavelength rays such as X-rays can be lethal or give you radiation poisoning (which is probably why the dentist or hospital X-ray technician goes into the other room when he/she takes your x-rays---they don't want the exposure), and you aren't even given a radiation badge to measure the exposure to gamma rays you just received.
We have no way to measure the amount of radiation your body absorbed, or how much energy particular tissues (heart, brain, bone marrow) absorbed. We can only guess, since we just don't know. We think we know the safety limits for hospital radiation treatment of cancer, and we know that the old treatment of polycythemia vera with oral radioactive phosphorus caused bone marrow cancers and leukemias later, but we don't know precise doses. We really don't even know if radiation exposure increases your risk of getting cancer linearly, in that each exposure adds to the risk of the previous one, or of there is a threshold dose of radiation below which there is no risk. We do know that in acute radiation exposure you can die in 48 hours or 48 weeks. We do know that the most rapidly dividing cells are preferentially killed by gamma rays, so that the bone marrow and the lining of your gut are especially sensitive. We do know that there can be delayed burn-scar tissue results, such as fibrosis of the lungs, or constrictive pericarditis (of the heart).We know that radiation sickness can affect every organ system of the body, but we can't reverse or treat it, except to support the patient's vital signs, and hope that death from overwhelming infection or cancer does not ensue. We also know that developing embryos are exquisitely sensitive to the damaging effects of radiation.
Now as to radioactivity and reactors themselves. The natural radioactivity of the trans-thorium elements provides the heat in the earth that keeps the core liquid and the earth's surface warm. Without natural radioactivity, the energy from sunlight would not be enough to keep us from freezing to death. Now since uranium emits heat when it radioactively decays, it needs to be constantly cooled in a reactor, which is why the naked exposure of uranium-embedded zirconium rods created so much heat that it boiled the surrounding water, energized the freeing of hydrogen from water, and then exploded the free hydrogen which then burned in the presence of the free oxygen also liberated. So a naked core is an extreme heat emergency, as well as a radioactive one.
You can design a nuclear reactor that can never go critical. This is the type that is installed in nuclear subs. In a reactor, free neutrons are allowed to bombard uranium atoms. These then fission,. releasing on the average 2.5 neutrons per uranium atoms struck. If each neutron then splits a uranium atom, then two more atoms are split, and 5 more neutrons released. If this happens rapidly enough, it is a self-sustaining generator of energy (and then converted to heat via giant water boilers)., and we say that the reactor has "gone critical", and we have a chain reaction. We adjust the depth of cadmium rods in the reactor to control the rate of reaction, and if the reaction goes supercritical, we rapidly lower the cadmium rods into the rector to dampen it. I should mention that this reaction occurred naturally at least once in the past, about 2,000,000,000 years ago in Oklo, Gabon, West Africa, where the uranium isotope ratios demonstrate that there was a critical mass of uranium that started to run away, and was stopped only by its own production of radioactive xenon, which is a excellent neutron absorber.
The half-life of a radioactive isotope is the amount of time it takes half of a given number of radioactive isotopes to decay (and, hopefully into a non-radioactive product, which is the case for Carbon-14, but not for Uranium-235, Uranium -238, or Plutonium-239). I should mention that radioactive cesium, which has a very long half life and is used in hospitals as a source of radiation, as also produced by runaway reactors. The half-life is not related to the radiation danger of the isotope, but the number of radioactive daughter products certainly is, like the production of the radioactive gas radon from the decay of uranium. BTW, did you know that all marble is naturally slightly radioactive?
I think that you can see that the only safe act is total avoidance, and perhaps the carrying of personal radiation badges, to be checked once a month.If you suspect a radioactive fallout, get rid of your clothes, and shower immediately, and carefully wash all food before eating. I would assume that all government warnings minimize the danger, just as they told the terminal cancer patients in 1947 in whom they injected radioactive phosphorous and other substances that it would cause them no danger (since they were dying anyway, and then the government autopsied their bodies to find out what it could about the deposition in and effects of radiation on the body). Or when they permitted sailors to stand on the decks of their ships and have radioactive debris be showered on them after the H-bomb test at Bikini and Einewetok atolls.
BTW, a reactor is scrammed by releasing the clamps holding cadmium rods out of the nuclear core of the reactor, and let gravity pull the rods in as rapidly as possible. For one midwest reactor, the blueprints were distributed upside down, and because of atomic secrecy, the workmen knew very little of the ultimate purpose of their construction. Luckily, before the reactor was run up to full power to test the SCRAM operation, someone noticed that the cadmium rods were inserted from the bottom!
But at least we are avoiding 4 stupidities caused by insufficient knowledge of the dangers of radiation:
a) we no longer handle radioactive samples with our bare hands
b) we no longer use radioactive thorium salts to remove hair in the armpits
c) we no longer paint the numbers on watches that glow in the dark with radium-based paint, and have the painters moisten and sharpen the brush tips with their lips and thereby deposit radium salts into their mouths
d) we no longer rush over as children to the shoe store fluoroscope to stand and put our feet in the xray-fluoroscope to see how well our feet fit into our shoes
How much natural or man-made radioactive exposure is safe? No one really knows. We can sometimes, for a given energy level of gamma rays, estimate the LD50, which is the total time exposure after which 50% of exposed humans will die. But this is only an estimate, and only for one energy level. We also have no way of predicting how much exposure to Xrays and natural radioactivity is necessary to increase your risk of cancer in a given organ by 1%. There are estimates of the risk of inducing breast cancer after 30 years of annual mammograms, but these are only estimates, as is the stated "safe" level of radon, a radioactive gas. In fact all radioactive safety levels are guesstimates arrived at by compromise by a committee, and have never been verified, except for accidental exposure to a runaway chain reaction, such as happened to one scientist in Los Alamos who was working with two clumps of a radioactive element and let them approach each other too closely.
In case you think any of the above is an exaggeration, let me tell you about one incident. Shortly after 9/11, many of the upscale shopping malls were equipped with radiation detectors at their entrances. Several years ago, a male cardiac patient had a (radioactive) stress-thallium test, which involves injecting a small dose of radioactive thallium into your bloodstream when you are near peak exercise, and then scanning you with a radiation detector to see the distribution of blood to your heart when you are exercising. You then sit there for four hours, and they re-scan you to see the distribution of blood to your heart when you are at rest. An hour after this test was finished, so we are talking about what happened 5 hours after then man was injected, he went to meet his wife at the shopping mall in Short Hills, New Jersey. The residual radiation in his body triggered the radiation detectors, and the entire mall was shut down and evacuated, and everyone examined with a hand-held Geiger counter, which is how the authorities discovered what had happened.
Saturday, April 2, 2011
Recommended Books Page Two
Here are a few books that I have found on Amazon that I think merit your review.
Recommended Books Page One
Here are a few books that I have found on Amazon that I think merit your
review.
review.
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