Japanese Prime Minister Naoto Kan attends a meeting on crisis of the Fukushima No. 1 nuclear power plant in Tokyo, Japan, March 15, 2011. Credit: Xinhua/Kyodo/Xinhua Press/Corbis
2 Reactor Vessels Now Reported Damaged
The crisis at Japan's nuclear reactors is still unfolding, and it can be hard to be sure of exactly what is going on (for example, the media incorrectly reported that the remaining 50 workers had been evacuated from the Fukushima plant -- more on that below). That's why I've tried to put together a timeline of the most important events and announcements from the past day.
The crisis at Japan's nuclear reactors is still unfolding, and it can be hard to be sure of exactly what is going on (for example, the media incorrectly reported that the remaining 50 workers had been evacuated from the Fukushima plant -- more on that below). That's why I've tried to put together a timeline of the most important events and announcements from the past day.
Credit Image: © Koichi Kamoshida/Jana Press/Zuma Press/Corbis
Yesterday, it was announced that the containment vessel of reactor #2 is cracked.
Today (Wednesday), it was announced that the containment vessel of reactor #3 may have been damaged, but that it was "unlikely to be severe", according to the Japanese authorities.
Status of the Fukushima plant reactors, by Wikipedia contributors (as usual, take Wikipedia material with a grain of salt, but it appears accurate because it is based on this chart by the Japanese Atomic Industrial Forum). Click for large version.
As you can see in the chart above (click on it for a larger version), only the buildings for reactors 5 & 6 are undamaged. That's because these reactors were not operational at the time of the Earthquake and Tsunami. But what matters most is that the containment buildings remain as intact as possible; the outer layers of most buildings seems to have been damaged when the workers vented pressure, but that doesn't necessarily mean that the containment structure itself has been breached.
A woman reads an extra of a newspaper about radiation released by the damaged reactors at Fukushima No. 1 nuclear power plant in Osaka, Japan, March 15, 2011. Credit: Xinhua/Kyodo/Xinhua Press/Corbis
Plans to dump water from helicopters on spent fuel cooling pool at unit 4 were aborted. There was a fire at that unit, but now smoke no longer visible according to reports. The helicopter mission was stopped because of radioactive steam coming out of the reactor #3.
Late yesterday there was a report that the 50 remaining workers had been evacuated, but that was apparently a mis-translation of a speech by Japan's chief cabinet secretary. Most workers have been evacuated, but the 50 remained, and were later joined by 50 others, for a total of 100 workers remaining at the Fukushima nuclear plant.
Reuters is reporting that water is now being poured on unit 5 & 6.
An overview of the Fukushima I nuclear plant in Japan, shortly before an explosion happened at a block of the plant, on 12 March 2011. Credit: EPA/STRINGER/Corbis
On radiation levels, the New York Times writes:
Radiation close to the reactors was reported to reach 400 millisieverts per hour on Tuesday after a blast inside reactor No. 2 and fire at reactor No. 4, but has since dropped back to as low as 0.6 millisieverts at the plant gate. Tokyo Electric and Japanese regulators have not released any statistics on radiation levels inside the containment buildings where engineers are desperately trying to fix electrical systems But nuclear experts said that indoor radiation levels were likely to be higher because the containment buildings were probably still preventing most radiation from leaving the plant.
Based on this radiation chart, these levels are still thankfully very low. But the workers on site might be exposed to higher levels if they have to go out of the heavily shielded control room to work closer to the reactors.
http://www.treehugger.com/files/2011/03/update-japan-nuclear-meltdown-fukushima-1-tsunami-earthquake-nukes.php?campaign=TH_rotatorMini-FAQ About Japan's Nuclear Power Plant Crisis
Update: 6 Important Questions About the Crisis at Japanese Nuclear Power Plants
Update 2: Update on Japan's Nuclear Crisis at Fukushima I
How Bad is Japan's Nuclear Problem?
There is a lot that is being said and written about Japan's earthquake-damaged nuclear power plants right now. Sadly, unless there's a big catastrophe, few people care to learn about nuclear power, so when things go wrong, people aren't sure what is going on and this can lead to panic. I'm no nuclear expert myself, but in this post I will share what I've learned about this situation and answer the most pressing questions that people might have ("Can it blow up? Is it another Chernobyl") to the best of my knowledge.
Can Japan's nuclear power plants explode like a nuclear bomb?
Thankfully, it is physically impossible for a nuclear power plant to explode like a nuclear bomb. It simply doesn't have the right kinds of materials: A fission bomb uses highly enriched uranium or plutonium (90%+ of U-235 or Pu-239), while a nuclear power station generally uses Uranium that is only enriched to around 5% (sometimes up to 20% in smaller research reactors). A nuclear power station also lacks all the other mechanisms that are necessary to create a nuclear explosion (like for example the implosion or gun-type assembly configurations that allow supercritical mass to be reached).What is a 'meltdown'?
When you get right down to it, a nuclear power plant is very sophisticated way to boil water. Controlled fission in the core generates heat, which creates steam that spins turbines. When a big earthquake hits, nuclear power plants are programmed to automatically shut down. But even after the fission reaction in the core is stopped, it takes a certain time for the radioactive byproducts to decay and cool down. If something - in this case a huge earthquake and tsunami double hit - prevents the cooling system from pumping water to the core and the emergency cooling system is prevented from kicking in, it can get hot enough to melt. In the very worst cases, part of the containment building, which envelops the reactor vessel which itself contains the fuel rods (it's like a russian doll of buildings), can partially melt, but containment buildings are designed to withstand the high pressures and high temperatures that occur in a meltdown, so in principle they should hold and allow the fuel rods to cool down safely over the next days.Is a repeat of what happened at Chernobyl likely?
It appears extremely unlikely because the Japanese nuclear power plants, as well as all nuclear power plants now in operation around the world, are designed very differently from the plant that exploded in Ukraine in 1986. The crucial difference is that the soviet reactor was not inside any kind of hard containment vessel. This means that when it failed, the high pressure couldn't be contained, which caused steam explosions that destroyed the reactor building and caused fires that sent a plume of radioactive fallout into the atmosphere. Chernobyl didn't explode like a nuclear bomb, it was closer to a "dirty bomb", which is a conventional bomb that spreads radioactive material around. The Japanese nukes have containment buildings and some seem to already have been vented to reduce the pressure inside.What kind of radiation exposure can be expected, and what are the potential health effects?
Matt just did a post about this very thing, so I suggest you go check it out. The good news is that potential exposure seems extremely low even for people who are close and likely to remain so.
6 Important Questions About the Crisis at Japanese Nuclear Power Plants
Update: Update on Japan's Nuclear Crisis at Fukushima I
Panicking Doesn't Help, We Need Facts
The crisis at the Japanese nuclear power plants continues, and if you've been paying attention to the media, things seems to be getting progressively worse. But it's hard to know exactly what is going on, as there are many slightly contradictory reports, and a lot of speculation and fuzzy language (for example, a radiation level "thousands of times higher than normal" might not be very dangerous if the normal level is very low). I'm no expert on nuclear meltdowns, but I know a little bit, just enough to compile a list of the questions that I think are most important to answer right now. Read on for the list and my tentative answers.
For basic questions like "Can a nuclear power plant explode like a nuclear weapon?", check out my mini-FAQ About Japan's Nuclear Power Plant Crisis.
What is the cooling situation in the reactor cores and storage pond? Is water still being pumped in, even if at a reduced rate?
This is a very important question because the cores are cooling down by themselves over time, but until they become cool enough to not melt through the reactor vessel, water needs to be used to dissipate that heat. The latest reports are that seawater is still being pumped, but it is a "struggle" and they are using "temporary fire pumps", so that's definitely not optimal.What kind of radioactive materials/isotopes have been released so far? Where? In what quantities?
That's another important question, because there are different types of radiation (some are stopped by a piece of paper or surface skin, other types can go through thicker materials) and different types of radioactive isotopes; some have a very short half-life, which means that they decay very rapidly into lighter atoms, while others take a lot longer to decay. There's a trade off . Radioactive isotopes with a very short half-life are usually more radioactive, but they become safe much faster, while long-lived radioactive isotopes can stay radioactive for a lot longer, but they are less dangerous.According to the International Atomic Energy Agency (IAEA):
on 15 March a dose rate of 11.9 millisieverts (mSv) per hour was observed. Six hours later, at 06:00 UTC on 15 March a dose rate of 0.6 millisieverts (mSv) per hour was observed. These observations indicate that the level of radioactivity has been decreasing at the site.So while it isn't yet clear what isotopes have been released, they probably came out when steam was vented to reduce pressure inside the containment vessel, and the dosage appears to be relatively low so far (10 mSv is the equivalent of a CT scan) and you would have to be right there to get these dosages (the power plant's control room is heavily shielded from radiation).
As reported earlier, a 400 millisieverts (mSv) per hour radiation dose observed at Fukushima Daiichi occurred between units 3 and 4. This is a high dose-level value, but it is a local value at a single location and at a certain point in time.
Check out this radiation chart for toxicity levels.
What kind of radiation do they emit?
Once again, I'm no expert. But I do know that there are many kinds of ionizing radiation, and it would be important to know what type the people near the nuclear power plants are at risk of being exposed to. As you can see in the image above, alpha radiation is easily stopped and does go very far ("In general, external alpha radiation is not harmful since alpha particles are effectively shielded by a few centimeters of air, a piece of paper, or the thin layer of dead skin cells. Even touching an alpha source is usually not harmful"), but gamma rays are harder to avoid ("Gamma rays and neutrons are more penetrating, causing diffuse damage throughout the body (e.g. radiation sickness), increasing incidence of cancer rather than burns."). See Matt's post for more on this.If the reactor vessel melts down, how likely is it that the molten core could get through the containment building's floor? And if it did, what would happen?
If the molten core stays hot enough for long enough to melt through the reactor vessel (which has 6.7-inch-thick steel walls and 8.4-inch-thick steel for its roof and floor) and into the containment building, what then? My understanding is that the radioactive fuel and fission byproducts would still be shielded from the outside, but would this make it much harder to keep cooling them down and to vent steam to reduce pressure? Would it increase the radiation that could escape through vented steam and gases?How fast are the fission byproducts cooling down?
That's another important variable. How long until the cores are cool enough that they can't melt through the containment layers anymore? Days? Weeks?Are the explosions that we've seen so far all been caused by venting to release pressure, or are some of those uncontrolled explosions?
At high temperatures, water can split into hydrogen and oxygen, which can cause explosions, especially when the high pressure gases and steam are vented to the outside. Are the explosions we've seen so far all of that type (like the one at Fukushima Daiichi 2 this morning)?How Much Radiation Exposure Do You Normally Get Every Year?
If you've even been half paying attention to the news this morning on the situation of the nuclear reactors damaged by the Japanese earthquake it'd be hard to miss all the talk about exposure to radiation--at the plant and in the vicinity, a US navy vessel moving away after detecting higher than normal radiation levels, people in Finland stocking up on iodine tablets fearing a spreading radiation cloud, talk of a cloud spreading across the Pacific to reach the United States.
Like many people I wasn't up on what normal levels of radiation exposure are, but some quick digging gave some very illuminating answers. So, here's what you're exposed to on an annual basis:
You Receive ~620 Millirem Per Year
According to stats from the US Nuclear Regulatory Commission average yearly exposure is roughly 620 millirem--half of which comes from natural sources (cosmic radiation, from the soil, radon, etc) and half comes from manmade sources. Note that geography can play a big part in that. In Colorado, for example, natural radiation exposure can be 1000 mrem per year due to higher altitude.
Some perspective: NRC limits "occupational radiation exposure to adults working with radioactive material to 5,000 mrem per year" and anything below 10,000 mrem is considered a low dose of radiation. In the Chernobyl disaster the 134 people working in the plant to put out the fire received 80,000-1,600,000 mrem--28 of them died within three months of exposure.
More? Listing of Common Radiation Exposures & EPA: Sources of Radiation Exposure
New York Times has a good rundown of the danger posed by various radioactive isotopes that may or may not have been released, or may yet be released.
Back to what's going on in Japan: LA Times reports that the aircraft carrier that moved in response to detecting elevated radiation levels experienced exposure equal to what a person might receive in one month from natural sources, so perhaps 26 mrem, and that the contamination was "easily removed with soap and water."
Yesterday, TreeHugger reported that exposure in Japan was equal to about one year of natural radiation (Christine explained that this was about 35-40 chest x-rays)--so perhaps 310 mrem.
UPDATE: Newer reports of radiation levels at the front gate of the Fukushima power plant place them significantly higher than earlier information--at that location radiation equivalent to three years of normal exposure in one hour have been detected.
UPDATE 2: BBC News reports that "radiation dosages of up to 400 millisieverts per hour were recorded at the site" and notes "A single dose of 1,000 millisieverts causes temporary radiation sickness such as nausea and vomiting."
On differing units used in measuring radiation
Though the USNRC uses millirems and variants in discussing radiation exposure, the current internationally preferred unit is the sievert and its subdivisions of millisievert and microsievert. For conversion: 1 millisievert = 100 mrem.
Common Radiation Exposures
Building Materials (average annual dose)- Brick - 7 millirem
- Concrete - 7 millirem
- Masonry - 13 millirem
- Stone - 10 millirem
- Wood - 4 millirem
- Airport luggage inspection systems - 0.0003 millirem
- Burning coal as fuel - 0.03 to 0.3 millirem
- Cardiac Pacemaker user - 100 millirem
- Cardiac Pacemaker spouse - 7.5 millirem
- Dental Prostheses - 0.01 millirem
- Gas mantle usage (indoor residential) - 4 millirem
- Gas mantle usage (camping) - 6 millirem
- Highway and road construction materials - 0.08 millirem
- Mining and agricultural products - less than 1 millirem
- Natural gas cooking ranges - 0.2 millirem
- Natural gas heaters - 0.1 millirem
- Opthalmic glass (eye dose from eyepieces) - less than 0.33 millirem (up to 4,000 millirem to the cornea of maximially-exposed)
- Opthalmic glass (instruments) - less than 0.1 millirem
- Radioluminescent watches and clocks - 0.001 to 0.005 millirem
- Smoke detector use - 0.009 millirem
- Television receivers - much less than 1 millirem
- Tobacco products - 1,300 millirem
- Tungsten welding rod usage - 0.02 millirem
- Video display terminals - much less than 1 millirem
- Skin Dose - 200 to 230 mrad per hour
- Contact Gamma Dose - 4 to 7 mR per hour
- Ambient Gamma Dose - Trivial
- Brazil nuts (0.5 pound) - 0.5 millirem
- Gatorade™ (quart/week) - 0.2 millirem
- Domestic water supplies - 1 to 6 millirem per year
- Accelerator facilities - 0.0001 millirem
- Aluminum reduction plants (kidney dose) - 1.2 millirem
- Copper smelters (lung dose) - 0.2 millirem
- Department of Energy facilities - 50 millirem
- Lead smelters (lung dose) - 5 millirem
- Manufacturers - 0.2 millirem
- Radiopharmaceutical suppliers (thyroid dose) - 0.3 millirem
- Research and test reactors - 1 millirem
- U. S. Navy shipyards - 0.02 millirem
- Zinc smelters (bone surface dose) - 0.02 millirem
- Cosmic radiation - 27 mrem
- Cosmogenic radionuclides - 1 millirem
- Inhaled radioactivity - 200 millirem
- Radioactivity in the body - 40 millirem
- Terrestrial radiation - 28 mrem
- Boiling water reactor operations - 0.1 millirem
- Fuel fabrication - 0.7 millirem
- Low-level waste storage - less than 1 millirem
- Open pit uranium mining - 26 millirem
- Pressurized water reactor operations - 0.6 millirem
- Underground uranium mining - 61 millirem
- Brain (Tc-99m DTPA) - 650 millirem
- Brain (O-15 water) - 170 millirem
- Brain (Tc-99m HMPAO) - 690 millirem
- Hepatobiliary (Tc-99m SCO) - 370 millirem
- Bone (Tc-99m MDP) - 440 millirem
- Lung Perfusion/Ventilation (Tc-99m MAA and Xe-133) - 150 millirem
- Kidney (Tc-99m DTPA) - 310 millirem
- Kidney (Tc-99m MAG3) - 520 millirem
- Tumor (Ga-67) - 1,220 millirem
- Heart (Tc-99m sestimibi) - 890 millirem
- Heart (Tc-99m pertechnetate) - 1,440 millirem
- Heart (Tl-201 chloride) - 1,700 millirem
- PET procedures (F-18 FDG) - 700 millirem
- External dose - 75 microrem
- Internal dose - 177 (committed dose through the year 2000)
- Barium enema (10 images) - 700 millirem
- Chest - 10 millirem
- CT (scout scan) - 111 millirem
- CT (body scan) - 1,000 to 4,000 millirem
- CT (head scan) - 4,000 to 6,000 millirem
- Dental x-ray - 9 millirad
- Extremities (arms, legs) - 1 millirem
- Hip - 83 millirem
- Intravenous Pyelogram - 158 millirem
- Lumbar spine - 127 millirem
- Skull - 22 millirem
- Upper GI series - 244 millirem
- Air (pilots) - 0.07 millirem (excluding cosmic exposure component)
- Air (attendants) - 3.5 millirem (excluding cosmic exposure component)
- Air (passengers) - 0.23 millirem (excluding cosmic exposure component)
- Highway - 70 millirem (hourly dose at 3 ft from the package)
- Other (unspecified) - 24 millirem (hourly dose at 3 ft from the package)
- Rail - 74 millirem (hourly dose at 3 ft from the package)
- Skull (PA or AP) - 3 millirem
- Skull (lateral) - 1 millirem
- Chest (PA) - 2 millirem
- chest (lateral) - 4 millirem
- chest (PA and lateral) - 6 millirem
- Thoracic spine (AP) - 40 millirem
- Thoracic spine (lateral) - 30 millirem
- Lumbar spine (AP) - 70 millirem
- Lumbar spine (lateral) - 30 millirem
- Abdomen - 70 millirem
- Pelvis (AP) - 70 millirem
- Bitewing dental film - 0.4 millirem
- Limbs and joints - 6 millirem
- Intravenous Pyelogram (kidneys, 6 films) - 250 millirem
- Barium swallow (24 images) - 150 millirem
- Intravenous Pyelogram (kidneys, 6 films) - 250 millirem
- Barium swallow (24 images) - 150 millirem
- CT, head - 200 millirem
- CT, chest - 800 millirem
- CT, abdomen - 1,000 millirem
- CT, pelvis - 1,000 millirem
- PTCA (heart study) - 750 to 5,700 millirem
- Coronary angiogram - 460 to 1,580 millirem
- Mammogram - 13 millirem
- Lumbar spine series - 180 millirem
- Thoracic spine series - 140 millirem
- Cervical spin series - 27 millirem
Its Everywhere!
Is radioactivity unique?
The earth has always been radioactive. Everyone and everything that has ever lived has been radioactive. In fact, the natural radioactivity in the environment is just about the same today as it was at the beginning of the Neolithic Age, more than 10,000 years ago.
What is radiation?
Radiation is energy in the form of particles or rays given off by atoms as they go from an unstable to a stable state. Some radioactive atoms exist naturally; others are made artificially.
Is there radioactivity in our bodies?
Yes. During our lifetime, our bodies harbor more than 200 billion billion radioactive atoms. About half of the radioactivity in our bodies comes from Potassium-40, a naturally-occurring radioactive form of potassium. Potassium is a vital nutrient and is especially important for the brain and muscles. Most of the rest of our bodies' radioactivity is from Carbon-14 and tritium, a radioactive form of hydrogen. These naturally-occurring radioactive substances expose our bodies to about 25 "millirem" per year, abbreviated as "mrem/yr".
Is there radioactivity in food and water?
Yes. Most radioactive substances enter our bodies as part of food, water or air. Our bodies use the radioactive as well as the nonradioactive forms of vital nutrients such as iodine and sodium. Radioactivity can be found at every step of the food chain. It is even in our drinking water. In a few areas of the United States, the naturally-occurring radioactivity in the drinking water can result in a dose of more than 1,000 millirem in one year.
What kinds of radioactivity are in food?
In general, the foods we eat contain varying concentrations of radium-226, thorium-232, potassium-40, carbon-14, and hydrogen-3, also known as tritium.
How much of these radionuclides are in foods?
Well, it depends, of course, on the food item. The U. S. Department of Energy gives the following concentrations as examples: Salad Oil 4,900 pCi/l; Milk 1,400 pCi/l; Whiskey 1,200 pCi/l; Beer 390 pCi/l; Tap Water 20 pCi/l; Brazil Nuts 14.00 pCi/g; Bananas 3.00 pCi/g; Tea 0.40 pCi/g; Flour 0.14 pCi/g; and Peanuts and Peanut butter 0.12 pCi/g.
Is there radiation in outer space?
Yes. Another type of natural radiation is cosmic radiation from the sun and outer space. Because the earth's atmosphere absorbs some of this radiation, locations at higher altitudes receive a greater exposure than those at lower altitudes. In Ohio, for example, the average resident receives a dose of about 40 millirem in one year from cosmic radiation. In Colorado, it is about 180 millirem in one year. Generally, for each 100-foot increase in altitude, there is an increased dose of one millirem per year.
Flying in an airplane increases our exposure to cosmic radiation. A coast-to-coast round trip gives us a dose of about four millirem.
The rocks and soils around us are radioactive.
In Ohio, radiation in soil and rocks contributes about 60 millirem in one year to our exposure. In Colorado, it is about 105 millirem per year. In Kerala, India, this radioactivity from soil and rocks can be 3,000 millirem per year, and at a beach in Guarapari, Brazil, it is over 5 millirem in a single hour -- but only a few residents who use that beach receive doses in excess of 500 millirem per year.
Is there radioactivity in our homes?
As a matter of fact, there is. If you live in a wood house, the natural radioactivity in the building materials gives you a dose of 30 to 50 millirem per year. In a brick house, it is 50 to 100 millirem per year. And, if your home is so tightly sealed that there is little ventilation, natural radioactive gases (radon) can be trapped for a longer period of time and thus increase your dose.
Is is true that we can't escape from radioactivity?
Yes, its quite true. Each person with whom we spend eight hours a day gives us a dose of about 0.1 millirem in a year.
Using a gas stove can increase the dose by about two millirem per year because of radioactive materials in the natural gas.
A person who smokes two packs of cigarettes a day receives a radiation dose of about 1,300 millrem per year. This is because polonium (a radioactive element) is part of the smoke and when inhaled, it gets trapped in the lungs.
So, its everywhere, right?
Radiation really is everywhere. We are exposed to a constant stream of radiation from the sun and outer space. Radioactivity is in the ground, the air, the buildings we live in, the food we eat, the water we drink, and the products we use. The average person in the United States receives a dose of about 360 millirem per year from these natural sources of radioactivity as well as from typical medical radiation exposures.
To put these radiation doses into perspective, although theoretically the risk increases with increased exposure to radioactivity, no effects have ever been observed at levels below 5,000 millirem delivered over a one year period. In fact, effects seen when humans are exposed to 100,000 millirem over a short time period are temporary and reversible. It takes a short-term dose of more than 500,000 millirem to cause a fatality.
Is it true that we can't live without it?
Yes, our bodies are radioactive. Its a simple fact of nature. But there is no cause for alarm. These very small but detectable levels of radioactivity are natural . . . as natural as life itself
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