Tag Archives: Japan

Nuclear Reactors 101

This week, Japan raised its nuclear reactor accident to a level 7, the highest stage on the nuclear incident scale created by the U.N.’s International Atomic Energy Agency. That is the same level as the 1986 Chernobyl disaster in Ukraine.

One thing is certain to come out of the reactor trouble in Japan – an international dialogue on nuclear energy generation. Both Japan and the U.S. depend on nuclear energy for approximately 20% of their national energy needs. Both countries have a long history of safe nuclear energy production with a few notable exceptions.

There are 436 nuclear reactors in the world at last count, possibly 433 now. These account for 15% of the world’s electricity production. The U.S., France and Japan alone account for more than half of the electricity generated by the world’s nuclear reactors.

What is a nuclear reactor, anyway? It’s a device used to control a sustained nuclear reaction (as if that helps).

Let’s start with the fuel. Uranium is a naturally occurring element found in bedrock in certain areas, like gold or diamonds. It’s dug up in mines where it occurs as a mixture of several kinds of uranium. Uranium 235 is the stuff used in nuclear reactors, and it’s about 1% of the uranium in the world. It’s a dwindling resource – we’re slowly running out because being radioactive, it burns itself up. The half-life is 700 million years, so don’t hold your breath.

For use in a reactor, uranium is concentrated (enriched) to a mixture of 20% U235. Continuing this enrichment to an 85% concentration of U235 would give you weapons-grade uranium.

Advanced Test Reactor core, Idaho National Laboratoryphoto © 2009 Argonne National Laboratory | more info (via: Wylio)

U235 is radioactive or unstable. What does that mean? It means it’s continually throwing off little high-energy particles (neutrons). It just sits there and cooks. Some of these particles hit other U235 atoms and more neutrons are released. Picture a pool table. Line up the balls so one hits two, and each of these hits two more. That is called a chain reaction. The other name is nuclear fission. As you can guess, it increases rather quickly – exponentially, the physicists would tell you.

U235 makes reactors go. It doesn’t need to be lit with a match or a spark plug. It’s constantly throwing off neutrons and releasing energy all on its own. The trick is to keep it from going too fast.

For use in a nuclear reactor, U235 is put in hollow tubes called fuel rods. These rods are placed in a reactor so they are close enough to cause a chain reaction. These tubes are surrounded by another material that can be adjusted to capture some of those neutrons to slow down the chain reaction. These are control rods. Simply speaking, if more neutrons hit other U235 atoms, the chain reaction speeds up. If the control rod captures more neutrons, the reaction slows down. U235 wants to release more and more energy, and the control rods slow it down. Conceptually it’s a glorified motorcycle throttle. The thing that makes a nuclear reactor work is controlling that chain reaction.

So we have U235 releasing a lot of heat and energy in the center of the reactor. The reactor coolant, usually water, circulates through the reactor where it absorbs energy and heat and turns to high pressure steam. This steam spins an electrical generator called a turbine. The steam cools back to water and is pumped through the reactor again. So, the water or reactor coolant does two things: it absorbs heat to cool the reactor, and it produces electricity. Pretty nifty.

The nuclear reactor will get too hot if the coolant stops circulating. The U235 can get so hot it melts through the bottom of the nuclear reactor. That is called a “meltdown.” That releases radiation, and that’s bad. The coolant absolutely needs to keep circulating.

Pound for pound, U235 will produce three million times the energy of the same amount of coal.

When the fuel rods have used up most of the U235, they are removed. Old fuel rods are still very radioactive and are stored in water to soak up those flying neutrons. We don’t want a chain reaction in an empty swimming pool. They need to stay completely submerged.

Nuclear reactors are designed with back-up systems for their back-up systems…for their back-up systems. Think many layers of redundancy. They are designed and built to never stop circulating coolant through the reactor. Very smart people spend a great deal of time trying to think up things that can go wrong – and preventing them.

Unfortunately, the Japanese nuclear plant was hit by a combination of natural forces the designers did not plan for. The unthinkable literally happened, and coolant stopped circulating.

So they are spraying water on the reactors with fire trucks, and trying to keep them cool. They are also filling the old fuel-rod pools from a distance. If it appears a bit unscripted and hazardous, it is.

But the result will not be Chernobyl 2, 3 and 4. These reactors are in containment buildings. There will be a local mess, but more so along the lines of the BP oil spill, not a radioactive wasteland.

Take care,

Dr. B

Radiation, Cancer and Medicine

Lately everybody is talking about the Japanese nuclear accident, radiation and the risk of cancer. In the midst of one of these conversations, I was asked, “If radiation causes cancer, how come cancer is treated with radiation?” Another version is, “Since radiation breaks down DNA, which can cause cancer, how come we give radiation to treat cancer? Doesn’t it just break down more DNA?” That actually is a pretty good question.

Radiation therapy is commonly used to treat cancer. It is pretty effective for cancers that are localized (in one place). It is also very effective at treating more widespread cancers like Hodgkin’s Lymphoma.

For localized disease, it’s all in the focus. Radiation therapy can be focused like a laser flashlight beam. Very high levels of radiation are put in the area of the tumor and not much anywhere else. So any damage from radiation therapy is limited to the tumor – not exactly, of course, but pretty closely. Damaging tumor cells is the point, and we hardly need to worry about tumor cells becoming cancerous.

Some radiation treatments expose much more of the body to radiation. Treatments for Lymphoma are one example of this. People are given what would be concerning amounts of radiation if they got it working in a Japanese damaged nuclear facility. Here’s the interesting part: cancer cells and normal cells react differently to radiation. The way radiation damages cells is by causing breaks in DNA, the blueprint of life. It turns out that cancer cells are not very good at repairing their DNA. Normal cells are much better at successfully repairing the damaged DNA. So the damaged cancer cells die, and most of the damaged normal cells don’t.

If this sounds a bit imprecise, it is. Usually the difference between the cancer cell and the normal cell isn’t 100%. Most cancer cells don’t survive high-dose radiation, and most normal cells survive, repair themselves or die a clean death – just as long as they don’t turn into cancer.

This actually is the basis of cancer treatment of any kind. An important difference between the cancer and normal cells needs to be found and capitalized on.

But radiation is radiation. It damages DNA, and occasionally DNA is repaired badly – sometimes so badly it acquires something unpleasant like uncontrolled growth.

Studies do suggest to an increased risk of disease 20 or 30 years after radiation treatment. Cancer usually occurs in the middle years and later so many patients are cured of their cancer and are at the end of their natural life span before enough years have gone by to see any ill effects from the radiation treatment.

But ultimately, we worry about today and let tomorrow take care of itself. The prospect of not treating today’s cancer is so bleak that a future risk seems a small price to pay. Radiation, like so many other things in life, has its pros and cons.

Take care,

Dr. B

Dr. Bucklin: Radiation and Your Health on FOX Phoenix

This morning, our own Dr. Donald Bucklin appeared on KSAZ-TV (FOX Phoenix) to talk about radiation’s effects on health.

Check out his interview here

Radiation and Food – Are You What You Eat?

Just when we thought the Japanese nuclear disaster could get no worse, they announce the radioactive contamination of produce, milk and water. Is it not bad enough already?

There has indeed been some low level radioactive contamination of locally produced food, milk and water in Japan. The major radioactive isotopes involved are identified as Iodine 131 (I 131) and Caesium 137 (C 137).

First, how could such a thing happen? There has been persistent, low-level leakage of the products of nuclear fission since the disaster started. This could be from emergency venting of the reactors to avoid rupture or due to fire involving waste fuel rods. Conceivably, there might even be damage to the reactors. These are heavy elements, and they are unlikely to go very far from the nuclear plant.

Unlike Chernobyl, the amount of release has been quite small, and there have not been any raging fires to blow these things up into the stratosphere. Nevertheless, we have a bit of measurable radiation in water, spinach and milk very close to the plant.

cute little milkphoto © 2006 hobvias sudoneighm | more info (via: Wylio)

I-131 is the better known of the two radionucletides. It is a radioactive form of the element iodine. We buy iodinated salt to get the small amount of iodine we need to make thyroid hormone. Making thyroid hormone is basically the only use your body has for iodine. If there is I-131 in the environment, and you happen to eat food contaminated with it, it will head straight to the thyroid gland (the body thinks it is normal iodine). While the thyroid gland is busy making thyroid hormone out of it, it is quietly irradiating your thyroid. This can cause some genetic damage, and many years later it is possible this could lead to thyroid cancer. For the record: thyroid cancer is one of the most curable cancers out there.

The problem with I-131 is what doctors call “self limiting.” The half life of I-131 is only 8 days. That means 50% remains 8 days from now and 25% 16 days from now. By 5 half lives (40 days), the stuff is practically gone.

No discussion of I-131 is complete without discussing KI (potassium iodide) – the wonder pill. For all you hear about this stuff, it should be $100 a pill and a government secret. Alas, it’s just an easily-made type of iodine. If you are on supplemental iodine, the thyroid will be filled up and won’t hold on to any I-131 it comes across, which is helpful only when you are around I-131 (which we’re not).

Caesium 137 is another radioactive isotope that is in the area of the reactors. This is a much more troublesome substance. If being radioactive is not enough, it is also chemically poisonous, water soluble and tends to settle in bones. C137 has a half life of 30 years, so it takes 150 years (5 half lives) for the radiation to be manageable. No one is allowed near Chernobyl because of still highly radioactive Caesium 137 in the soil.

If C-137 gets into your body, the biologic half life is 70 days, rather than 30 years. So you will be effectively rid of it in just about one year (350 days). That’s at least one year too long for most people.

Food can get contaminated by radioactive dust falling on spinach leaves. Radioactive dust can contaminate grass and be eaten by dairy cows, producing radioactive milk. Now before we give ourselves osteoporosis from avoiding milk and anemia from avoiding spinach, we need too remember two things: 1) the damaged reactors are in Japan, not California, and 2) the radioactive contamination is so minor, there is no danger.

How much milk from next to the Japanese reactor do you think gets exported to the United States? Zero. Same goes for spinach. These are locally grown products that are consumed locally, and not even there these days. Even if the radiation was not in question, it would cost a ridiculous amount to fly milk and spinach around the world.

But you can bet that you are protected by more than just distance and the law of supply and demand. Export of Japanese agricultural products, few that they are, are carefully inspected for the least trace of radiation before being accepted in this country.

Radiation identified in the food chain is certainly dramatic news. It was a predictable and expected consequence of the Japanese nuclear reactor trouble. Thankfully, we are safely on the opposite side of the planet.

Take care,

Dr. B

Little to Fear in the U.S. As Radiation Concerns Abound

It’s easy to be afraid and nervous regarding the recent news from Japan when it’s described in such ominous terms. There is no question that the earthquake and resulting loss of life and property has been tragic and sudden.

The nature of news reporting often dwells on the negative and inflammatory. The repetition also sets an ominous and foreboding tone; however, closer examination of the facts is necessary to understand the implications to the rest of the global community and to each of us as individuals. The dread of something catastrophic over which you have no control serves to increase our fear and anxiety about the circumstances.

Radiation is one of those perils that is invisible and something that most people understand only through science fiction movies. Typically when it comes to the unknown, the average person is prone to be suspicious, confused, anxious and distrustful. The reality is the science of radiation, its capabilities and risks are well understood. The radiation released from a nuclear power accident is different than that of a nuclear bomb. Even allowing for the explosions that have occurred at Japanese nuclear reactors there is a vast difference in the type of radiation released. It is nothing like a nuclear bomb as seen on footage from testing in the Nevada desert or the old films of World War II.

Within 10 to 50 miles of the disaster, important risks both short- and long-term exist. Fortunately, we are some 5,000 miles away. For decades, a very good network throughout the U.S. monitors every day in real time the amount of radiation in the atmosphere. This was very effective in understanding the risks of the 1986 Chernobyl disaster and several other international nuclear power plant accidents. This is being supplemented by portable monitors along areas of the U.S. West Coast. Fear simply need not be part of the conversation.

What do you need to know and understand? The amount of radiation that is likely to reach the United States is very small compared to the amount of background radiation to which we are already exposed on a daily basis. No one needs to take any specific actions at this time. It is unlikely that anything will need to be done in the U.S. to protect ourselves as there is no particular risk from the events in Japan.

Of note is the distribution by the Japanese health officials of potassium iodide to individuals in local areas of possible contamination. Potassium iodide has limited usefulness for protection against thyroid cancer from exposure to radioactive iodide, a dangerous isotope commonly released in a nuclear power accident. Timing and dosing are critical. It should only be used by those most at risk, which include infants, children and young adults. It is not 100% effective and does not protect against other types of cancer. There are potential side effects even though it is sold without a prescription. The Center for Disease Control does not recommend any action of this kind at all for anyone in the U.S. nor do they anticipate this being necessary from the current disaster in Japan. Do not be fooled or misinformed on this point.

Events are still ongoing with a final chapter yet to come, however, considering the distance from the source of radiation in Japan to the U.S., there is little concern at this point. The dilution and scattering of radiation over long distances keeps the amount in the atmosphere rather low. Is any extra radiation to be avoided? Of course it is, however, there are more significant risks, which are actually trivial, much closer to home. As my colleagues have so aptly pointed out, there is greater risk from environmental radiation in Denver than in Tokyo, which is less than 150 miles from the disaster site.

Being mindful about disasters in the world while understanding the facts is the best thing you can do. If you have further questions or concerns, consult your primary healthcare provider or local health department for information. The Center for Disease Control remains a reliable resource for good current advice.

– Dr. Kaler

Dr. Bucklin Offers Insight on Radiation Exposure to CNBC, Wall Street Journal

In the wake of the nuclear disaster in Japan, U.S. HealthWorks’ Medical Review Officer Dr. Donald Bucklin appeared on CNBC‘s “Squawk on the Street” this morning to discuss what health effects, if any, there might be following the explosions. Check out his interview here, as well as his thoughts in the Wall Street Journal and Bloomberg.

Radiation Exposure in the Real World

Japan’s nuclear threats have us all thinking about radiation exposure; and I have an added interest since I was the medical director for 10 years at the Palo Verde Nuclear Generating Station, the largest nuclear plant in the nation.

But my first introduction to the hazards of radiation was as an elementary student. We, like all children around the U.S., were instructed to hide under our desks in the event of nuclear war. That seems a bit naive in retrospect.

Radiation is everywhere. The sun emits radiation, as does the earth, and probably the moon. The stars definitely do. Medical procedures like X-rays and CT scans involve radiation, as do TSA scanners. There is even a little radiation in the food we eat and the air we breathe. Like so many other things, radiation is all about dose.

Radiation is counted in millisievert (mSv), a word which keeps the non-PhDs like myself out of their field. Normally we are exposed to a background radiation total of 2.40 mSv per year. This is an additive scale. It’s like getting less than a penny’s worth of radiation per day and end up with $2.40 at the end of the year. This comes from solar radiation predominantly, and a small amount from man-made sources. Man-made sources range from the luminous hands on your watch, a chest X-ray, or nuclear testing from 60 years ago.

Some locations have higher normal background radiation due to more radioactive materials in the bedrock or simply high elevation like Denver. The normal range of background radiation is from 1 to 100, so a hundred-fold increase could still be in the normal range.

So why worry about radiation?

Radiation is bad because it can cause breaks in your DNA – the chain of life so to speak. You don’t go far with a broken chain. The body attempts to repair these breaks and is pretty successful, but nothing is 100%. Those few poorly repaired DNA chains may self-destruct and cause no mischief, or can code for unfriendly cells, like cancer.

Scientists have studied radiation exposure and calculated that normal background radiation will cause 1 person out of 100 to get cancer in his or her lifetime. Additional radiation exposure increases the risk.

There is also danger from large exposures to radiation that occur acutely, as opposed to 20 years of exposure. This is called radiation sickness. Here we are talking about nuclear accidents. Radiation sickness causes the most active cells to die first. The lining of your stomach and intestine are usually affected first, causing nausea, vomiting and bloody diarrhea. This might take 24 hours to develop in exposures of 3,500 mSv or 1 hour in more extreme exposures of 5,500 mSv. At 8,000 mSv acute exposure, the mortality rate is 50%. The cardiovascular system breaks down in high-level radiation exposure. If you survive those, the blood system is the next likely victim. Radiation can kill your blood-making cells. You would miss them.

These are the kind of dangers emergency workers who stayed at the damaged nuclear plant face.

What about people in Tokyo or the world?

“Dilution is the solution to pollution” was my organic chemistry’s professor’s favorite expression. The closer you are to the source, the higher the radiation exposure. Radiation goes down with distance. This assumes the radiation source doesn’t move.

The levels measured at the plant in recent days are high enough to cause radiation sickness. These are potentially dangerous in the short term as well as the long term. The levels measured 120 miles away in Tokyo are 10 times higher than normal, but you would get just as much radiation moving to Denver. Moving to Denver with its higher level of solar radiation (due to elevation) doesn’t seem like a particularly foolhardy thing to do.

But life gets more complicated if the radiation source moves around. Radioactive elements are rather dense and don’t move around too easily. All solids can be made liquid or gas, just like water. The fuel rods in the reactor are solids. They release huge amounts of heat energy because they are radioactive. If not cooled, this heat can build up to the point of making the uranium rods melt and become a liquid. This liquid is so dense and hot, it can melt though almost anything (picture trying to keep lava in a container).

The next step is going from liquid to gas. Uranium can be vaporized by explosion or intense heat. Now we have a cloud of highly radioactive material floating about. That is exactly what happened at Chernobyl 20 years ago. One of the radioactive elements to spread was radioactive iodine. Potassium iodide keeps your thyroid full and stops you from absorbing the radioactive variety. This helps prevent thyroid cancer, but nothing else.

So this triple (quadruple) meltdown is unprecedented in history, but the science is very well understood. Simply keeping distance between you and trouble, like so many other times in life, is all it takes. Today, you will get more radiation in Denver than in Tokyo.

Take care,

Dr. B