Severity is hard to quantify, the numbers are really all over the place. It’s impossible to know exactly how much radiation is released in these events but the numbers tend to go something like this. Fukushima was 5-10 times less severe than Chernobyl, and Chernobyl was 50-100 times less severe than the nuclear weapons testing era. There are so many complexities involved with measuring radiation releases that the numbers can be skewed all over the place. Regardless, the biggest anthropogenic releases were definitely during the nuclear testing era.
A worst case scenario at reactor 4 fuel pond could potentially be a bigger problem than what fukushima started with. The fuel is still in the early stages of cool down and capable of melting if not activly cooled. The fuel pond is located on the reactor service floor several stories above ground level. If the fuel melted it could potentially compromise the pools integrity making it impossible to fill with water. Another earthquake or catastrophic event could also initiate this scenario. I don’t really see how they could possibly control the situation if the pool was to become significantly damaged, this would basically be a zero containment scenario. Very different than having control of the release (albeit limited control) like in fukushimas original situation. The fuel would likely make way down into the reactor building and eventually settle like it did in Chernobyl, fire would likely ensue minus the explosions because we aren’t dealing with a pressure vessel in this situation. However at least two of the neighboring reactors need active cooling to remain in cold shut down status, if these systems were affected by a catastrophe in reactor 4 who really knows how bad the situation could get… That particular pool receives the most attention and hopefully they can sit on it for 5 yrs or so until it cools down a bit. I don’t personally see them being able to remove the fuel before then.
With that said, the fukushima catastrophe means something different for Japan than it does for the rest of the world.. When you look at the numbers and don’t really understand them it is easy to get alarmed, the media tends to report radiation contamination numbers in a way that does not always paint an accurate picture of the risks. When a release happens the radiation is highly concentrated at the point of origin but in reality it dilutes to concentrations that aren’t readily traceable thereafter.
An average Americans lifetime radiation dose looks something like this
You encounter radiation every day, you inhale radon, you ingest foods with natural radioactivity, you receive radiation dose from standard medical procedures, smoking, and even if you somehow avoid all of that you can’t escape the cosmic radiation zipping through your body every day and even right now as you read this post. Anthropogenic (manmade) radiation releases like nuclear accidents and atomic weapons testing only account for about 0.167% of your lifetime radiation dose. You live on a very radioactive planet powered by a very radioactive Sun.
The people most affected by nuclear disasters are the first responders and people in the immediate area of the disaster. Radiation emanation follows the inverse square law, basically this means that if you double your distance from the radiation source you decrease your exposure by 4 times. And If you quadruple your distance from the source the exposure decreases by 16 times and so on…
The ICRP model for stochastic risk assessment states that a dose of 1 Sv (Sievert) = 5% chance of developing a cancer.
Looking at some random numbers to grasp dose:
Highest exposure to an individual at fukushima was approximately 650 mSv
0.650 Sv * 5% = 3.25% chance of developing a cancer from the exposure.
Average fukushima emergency worker dose was approximately 100 mSv
0.100 Sv * 5% = 0.5% chance of developing cancer from the exposure
Highest exposure at Chernobyl was approximately 16 Sv (16,000 mSv)
16 Sv * 5% = 80% chance of cancer. Many of the individuals with doses this high suffered from radiation sickness and died in the years following the event.
Average CT Scan of the abdomen is approx. 8 mSv
0.008 Sv * 5% = 0.04% chance of developing a cancer from the exposure.
Annual dose from background radiation is approximately 3.5 mSv
0.0035 Sv * 5% = 0.0175% chance annually.
The recent fish caught at fukushima that was over 7000 times the safe food limit had about 740,000 Bq/kg of Cesium contamination, which equates to approximately 100 mSv/kg for cesium gamma.
0.100 Sv * 5% = 0.5% of cancer per kilogram of fish
A few fish caught off the coast of California were said to have 5 times the normal amount of radiation activity from cesium contamination. This was about 5 Bq/kg which equates to approximately 0.000676 mSv
6.75X10^-7 Sv * 5% = 0.0000034% chance of cancer… These numbers are so low they are meaningless, and frankly way beyond the intended use of the ICRP model to begin with. Yet it still gets reported… This type of miscommunication happens all the time, just because radiation is detectable does not mean it’s dangerous.
The calculations above follow the simplest form of the linear no threshold model and are based on numbers I could conveniently find or remember. All I am really trying to do is paint a picture of general observations as a function of dose. Primarily you can see that the worst of the Chernobyl exposures were much more severe than the worst of the fukushima exposures.
Let’s take the most exposed fukushima worker with a 3.25% risk and compare it to normal background radiation risk of 0.0175%. The difference appears monumental, but does it tell us anything tangible? The media headline would read something like “fukushima workers now 185 times more likely to develop cancer”. Say that the fukushima worker shows up to a clinic with cancer in 20yrs, was it caused by the radiation exposure? Maybe he was a smoker (~30% chance of causing cancer). Maybe he ate copious amounts of red meat every day, or had a woodworking hobby and worked with solvents.. These might be crappy examples but the overall point is that it is very difficult to say whether or not a cancer was induced by a small to moderate radiation exposure because there are far more potent carcinogens that people readily expose themselves to.
I’m not trying to downplay the fukushima tragedy, it was a very unfortunate event that displaced hundreds of thousands of people. But on the global scale, even if there were a second incident, life would continue normally for the vast majority of the world population. Fukushima will mostly remain a localized problem despite what you may read in the paper..
Re: Japan nuclear agency upgrades Fukushima alert level
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