Overachieving makes for sleepless nights...but results in cool stop motion video!

This blog has made me totally rethink how to go about trying to explain complicated ideas to people.  Thinking back to the beginning of the semester, I have to laugh at how I almost wore it as a badge of honor that I could speak this language known as science.  What I learned this semester is that most of the world does not speak, nor do they want to speak this highly complicated and often intimidating language.  I know exactly how frustrating it can be when people talk to you in a language you don't speak.

I took violin lessons for 12 years, starting when I was 8 years old.  Many of those years were with one of the most inspirational figures I have ever met.  Her name was Korina, and she was part of the nationally renown Veronika String Quartet.  To make a long story short, the quartet was from Russia, and they were all very Russian.  Korina was trained under the disciplined lifestyle that the Soviets were renown for.  This needless to say caused some friction with American student because we didn't find it appropriate to practice the instrument 8 hours every day.  She was a wonderful teacher none the less.  Being from Russia though, her native language was Russian.  She was always good at explaining what needed to be done to me in English, but she was also good at switching to Russian when talking to the other quartet members about me.  I remain convinced to this day that they made a lot of jokes at my expense that I will never know about... My point is that speaking a different language is often speak around those they don't want to communicate with.  Korina wanted to talk about things she didn't want me to hear (probably the truth about how bad I was), but scientists often use their language to speak above the audience.  They get a weird kind of kick out of it, which I know because I have done it.  Nothing makes a nerd feel better than sounding smarter than somebody else, just like athletes like to show off their abilities on the field.  Just like with athletes though, nobody likes a ball hog.

Ok, so now I am on a tangent.  The reason that I am bringing this up to you is because the end of the semester is coming near.  A couple more posts and this blog project will be complete as far as the class goes.  I started out excited at the beginning of the semester.  Starting a blog, I though I would have the perfect way to just write out all the basics of nuclear power.  That would fix everything as people would read the facts and everybody would be educated on the basics of nuclear power...well as it turns out, when people don't care you aren't going to get them to read anything!  I just had a friend ask me to proof read a paper for a class and I couldn't even finish it because I didn't care.  It is an absolute truth.  Blogging has been an excellent medium for me to get the information I feel important out there so people can see it.  I even like to think that some of my posts have been mildly entertaining.  The fact that people have to put work into reading the blog post in the first place is very limiting to my ability to communicate.

I was very excited when we were given a chance in another one of my classes to do a public outreach project about nuclear power.  I have learned so much in this class about communicating scientific information that I wanted to apply to other mediums.  Reading a book called "Don't be Such a Scientists" by Randy Olsen particularly interested me in film.  When a friend in the class suggested that we do a stop motion film for the project, a flood of ideas came over us about communicating the basics of nuclear power.  I have to admit that this has been the most involved project of my life, but it is by far the school project that I am the most proud of.  The video is a little long, but we cover most of the basics about nuclear power in a relatively short period of time.  In essence, this video summarizes the technical information that I have tried to give up till now.  For those of you following my blog up till this point, I would love to hear if the video is better at conveying information than my writing.  Anyway, without any further adieu, I present to you a look at nuclear power in stop motion!  Enjoy!  Oh, by the way, turn your volume up nice and loud.  The levels are a little soft, but the song is awesome!

What I want to do when I grow up...

I mentioned before that I had a really interesting spring break this year as far as nuclear power goes.  You all know about Fukushima, but also during this time there were a series of public meetings being held in Pueblo, Colorado about building a nuclear power plant there.  This is where I grew up, and being in Pueblo over spring break, I naturally went to all the meetings. 

Going to these meetings as someone who has had some education in the nuclear industry was an interesting experience.  It was really interesting to hear about all the concerns people from the general public had about the nuclear power plant.  Some of the concerns were legitimate issues that needed to be tackled and some of them were issues that had no traction.  None the less, this was definitely a good experience when it comes to learning about what nuclear power faces when it comes to the public.  These issues were definitely exaggerated by the events simultaneously occurring in Fukushima, but it gave me a good understanding of how the public views nuclear power.

I don't really want to get into that now, but I want to talk about one key issue that was brought up.  The issue of transporting nuclear waste held a lot of traction with the local community.  People opposed to nuclear power brought in arguments that nuclear waste would be moved through their residential areas and near schools.  What if something happened?  Oh yes, the dreadful "what if?" the nuclear industry will face until the end of time.  Luckily in the transportation section, the nuclear industry has done a lot of thinking about "what if?" scenarios.

In fact, transportation of high level nuclear waste is one of the most engineered types of transportation out there.  This is both out of necessity as well as out of public outcry.  It is certain though that nuclear waste is special.  Unlike with other waste forms, we need to be careful of the geometries in which we move nuclear waste.  Under the right conditions, we could actually cause nuclear waste to start inducing a fission chain reaction, which would cause it to heat up.  So what is done about this?  Well, we know how to make the material go critical, and we know how to stop it from going critical.  Thus, we can design waste containers which keep nuclear waste from inducing fission reactions.

Most people are afraid of accidents happening on the road.  Nuclear waste is largely transported via truck in the United States.  It is true that sometimes trucks do have accidents.  Let me just say that the waste containers have been designed for this too.  Instead of me telling you though, let me just show you.  I recommend that you watch this whole video.  I got a really big kick out of it!

This is totally what I want to do when I grow up!  Sadly, I think they deemed these kinds of tests too dangerous back in the 1970s, so I never really had a chance.  But wrecking a rocket train!?  Every kids dream!

Anyway, I think this speaks for itself in saying what kind of damage that  nuclear waste transportation flasks can withstand.  If there was an accident on the road, you can remain confident that the radioactive material will be safely contained.  Take away point...I don't think that the transportation of nuclear waste is a good argument for halting nuclear power in the United States.

Earthquake, tsunami, tornado...what's next?

Mother nature has definitely been hard on nuclear power the last few weeks.  First a 9.0 magnitude earthquake followed by a 30 foot tsunami cripples the Fukushima Daiichi plant, and now a tornado shuts down a nuclear power plant in Virginia.  If you didn't hear about this, you can check it out here.  It doesn't seem that the major news networks covered this one too much in depth...not that I am complaining.

Last Saturday, a series of nasty storms went through the south eastern United States.  There were reports of several tornadoes from the storm, including one which managed to touch down in the middle of Virginia's Surry nuclear power plant.  It didn't hit either of the two reactors at the site, but it did manage to destroy the switchgear for the plant.  When I say switchgear, I am talking about those fenced off areas you see next to the road that look like a mad scientist should live there.  These are the places where power flow is controlled.  They are responsible for directing where power goes as well as for cutting off power when necessary.  In other words, when the switchgear was taken out at the Surry nuclear power plant, it cut off the outside power.

It seems that people got a little nervous hearing that Surry had lost external power.  I mean, we are still going to the effects of Fukushima Daiichi not being able to restore outside power.  There is a major difference though.  The backup generators at Surry were not washed away by a tsunami.  After the tornado took out the switchgear, the plant lost power and the reactors shut down as designed.  The backup generators then came online and kept the reactors cool.  This is how the safety systems are supposed to work.  There were designed this way.

Some are saying that we were lucky that the tornado didn't hit the reactor buildings themselves.  I think this again is just a product of nerves resulting from the recent incident.  We must remember that when the reactors were built, they were designed to withstand such natural occurrences.  A magnitude 9.0 earthquake and 30 foot tsunami wasn't really believed to be a possibility.  That was a mistake looking back in hindsight.  In Virginia though, the risk of tornado is believed to be a possibility.  Actually, the containment vessels are designed for much worse than even a tornado, such as an airplane crashing into it.  It would have most likely been a less significant nuclear accident had the tornado hit the reactor itself.  The switchgear is much more vulnerable, yet we still have safety systems to account for failure there.

Power has been restored to one of the reactors at Surry and the other reactor is expected to have power within another couple days.  After power has been fully restored, the plant will assume operating at full power again.  The take away message...A tornado hit one of the more vulnerable parts of a nuclear power plant and there was no disaster.  The plant shut down for about a week and then will continue to operate as normal.  If that is not a testament to the stability of nuclear power, I really don't know what is!

Sprouted grain and nuclear power

I am not going to lie...I spend a lot of time talking and thinking about energy production.  I have to blame some of this on my brother.  You see, he is also a Mines student.  A junior electrical engineering major focusing on power generation.  Between that, me going to school for nuclear engineering, and the fact that we live together, I spend a lot of time discussing the issues.  The other day though, my brother pointed me to an interesting article on the true economic costs of using coal to produce electricity.

The article was interesting based on its scientific merit alone, but I found it very interesting thanks to an interesting analogy it made.  Personally, I had never thought of coal-fired power plants as being like junk food.  This I think is the perfect way to describe them though!  Junk food is cheap, it tastes good, and makes up a large percentage of the food that most Americans (at least college students) consume.  The bad part about junk food is that it is not good for you.  It is unhealthy and it most likely will have greater cost down the road in the form of heart attacks and what not. 

Coal is cheap and it makes the electricity bill easy for the consumer to withstand.  Aka, coal "tastes good" to the normal person.  It is also dirty and hard on the environment.  It causes thousands of early deaths each year in the United States and the emissions of coal-fired power plants are putting things into the atmosphere that we don't really want there.  Using coal is kind of gearing us up for a planetary heart attack just like junk food does to our body.

You see, I have been trying to avert away from the college diet myself, so this analogy is especially interesting.  I have recently become a fruitaholic and I have even become that crazy guy in the grocery store reading all the labels.  Why you might ask?  Well, because I am interested in my general health.  Do you see where I am going yet?

The article didn't really finish the analogy you see.  While there is junk food, there are also food out there that are good for you.  Incidentally, there are also energy forms out there that are good for us.  This is where the industry is so interested in going nowadays.  Renewable energies are the albeit more expensive forms of energies, but they are the types of energies that are ultimately more healthy for our environment.

Many people use the argument that nuclear power is simply too expensive to implement.  Those of you who have been following me for a while know my opinion on this, but right now it is true that nuclear power has a high capitol cost compared to coal-fired power plants.  Have you ever gone into a grocer store and bought foods that were healthy for you?  Well, when you do you will notice your grocery bill sky rocket.  It is a general fact that higher quality products demand a higher cost.  For our well being, it is just a price we choose to cope with.  To ensure that we are nicer to our environment, we need to be willing to spend more money.  There is such a thing as electricity being too cheap when it is promoting the use of unhealthy power producing practices.  Junk food is too cheap, and that is why college kids have such unhealthy diets. 

Economics still must play a role though.  We must choose the method that provides the reasonable benefits we need without being too expensive.  Is it always worth buying the most expensive health food when trying to eat healthily?  Not really, considering we can gain the same health benefits by eating reasonably healthy.  We shouldn't go overboard and put all our resources toward an energy form that will accomplish the same thing as an energy form that has much less over all cost.  Solar and wind power are both more expensive than nuclear power in dollar cost as well as in the impact cost.  They require huge tracks of land (yes, I said that on purpose)  and are not up to optimal efficiency at this point.  Nuclear also has issues associated with it as far as waste and safety go.  My point?  We don't have an energy solution yet.  What we do know is that we need to try and change our diet.  Our long term health depends upon it.

What do Sheldon, zebras, and nuclear power all have in common?

In my last post, I tried to give you a little technical insight into how a nuclear power plant can be made passively safe.  These safety systems are not the coolest passive safety systms incorporated into modern day plants though.  Some of you had your ear caught by the idea of a nuclear power plant that was stable, even when all cooling systems were removed during operation.  This is by far the worst case scenario that a nuclear reactor could face.  Designing a reactor that will not allow itself to heat up enough to meltdown despite the loss of all cooling is kind of like genetically breeding a cat to clean its own litterbox and feed itself.  It fixes a lot of the problems of having one.

Any reactor that could be built in the United States now has to have what is known as a negative feedback coefficient.  I am sure that nuclear engineers refer to this as a NFC to go along with the other 10,000 acronyms that they have...ok, I made that up.  Anyway, the negative feedback coefficient means that any kind of power increase in the reactor (which is responsible for the reactor getting hotter) causes the reactor to automatically begin to shut itself down until it obtains the original power level.  Old reactors, and many research reactors do not do this.  Many of them actually have positive feedback coefficients, meaning that the power level in the reactor increases as a result of a power increase.  This is not good when it comes to the safety of a commercial reactor.

So how do we design a reactor to have a negative feedback coefficient?  Well, there are several mechanisms that cause negative feedback in the reactor, but I want to talk about my favorite one.  It is something known as doppler broadening.  Yes, it is related to doppler effect that you all know and love, especially if you watch the Big Bang Theory.

The doppler broadening effect in nuclear engineering has nothing to do with a shift in frequency though.  The effect is actually quite complicated as I found out when I wanted to do a presentation on it for an undergraduate nuclear physics class.  I wish I knew of another place to point you to learn more about the subject, but all I can point you to is engineering textbooks for more information.  Sorry about that!  On the other hand, you are about to get a lesson in something that few outside of nuclear engineers know much about.  Don't worry, I don't claim to know that much about it either, but I never the less will tell you what I have deciphered.

In nuclear engineering, a quantity known as the microscopic cross section is one of the most important properties for nuclear materials.  It is basically telling us the probability of a neutron interacting with our nuclear fuel.  For fissile materials, it is this quantity that tells us the liklihood of a fission reaction occuring given a certain neutron.  It is kind of like playing darts.  The microscopic cross section gives us the probability of hitting the dart board.  The bigger the dart board, the more likely I will be to hit it (believe me, I need a big dart board).  In other words, the microscopic cross sectin is kind of like the area of the dart board.  The bigger the cross section, the more likely a neutron will interact with the fuel.

Nuclear materials have what are known as resonances when it comes to reacting with neutrons.  You see, not all the neutrons in a nuclear reactor are the same energy.  In fact, there is pretty much a continuous distribution of neutron energies in the reactor core.  The microscopic cross section though is energy dependent, meaning that it changes depeding on how much energy the neutrong has (how fast the neutron is moving).  The nuclear material is more likely to react with neutrons of some energies than others, meaning that the microscopic cross section is higher for neutrons of certain energies than they are for most.  This gives rise to resonances in the cross section that look like the graph.  At a certain energy, there is a peak in the cross section.

Fissile material is not the only type of material that reacts with neutrons although.  U-238 captures neutrons of certain energies to become Pu-239, which happens to be fissile.  My point is that U-238 also has a cross section for neutrons in a reactor, not just U-235.  Under operating conditions, the resonant peaks for which U-235 and U-238 react with neutrons occur a different neutron energies.  In other words, normally they are not stealing each others neutrons.  U-235 has a high affinity for neutrons of one energy, while U-238 reacts with neutrons of another energy.  They are like two kids that have their own set of toys.  They are off in their own little corners playing their own game.  They are not concerned with what the other is doing.

But the story doesn't remain so friendly.  You see, as it turns out the microscopic cross section is also temperature dependent.  This means that changes in temperature in the reactor affect the cross section, and it does so in a very intriguing way.  It causes the resonant peaks, like the one in the picture above, to kind of melt.  Thus, at the resonant neutron energy, the cross section actually becomes smaller.  This is not what induces the negative feedback though.  Here is a picture that depicts what is going on as the temperature in the core increases.

This is the reaction cross section at a resonance peak for three different temperatures.  The tallest peak is at the lowest temperature.  That thing that is more of a hill than a peak is what the cross section resonance looks like when the temperature gets significantly higher.  I already noted that the height of the peak will shrink, and it does.  The interesting part though is that the peak gets fatter.  It widens to cover more neutrons energies.  Hence the term "doppler broadening."  As temperature rises, the resonant peaks which describe what energy neutrons the nuclear material will react with becomes wider.  This means that as the temperature increases, the nuclear material will actually react with more energies of neutrons.  There are now more "fish in the sea" to borrow a popular cliche.

You are probably thinking, "Aaron, you are nuts...this will cause the reactor to increase in power because there will now be more fissions occurring in the fuel!"  Well, actually quite the opposite happens.  You see, the resonant peaks at which U-238 and U-235 react with neutrons are not that far apart from each other in terms of energy.  As the resonant peaks get fatter due to doppler broadening, the resonant peaks of the two materials begin to overlap.  Now, they are starting to play with eachother's toys.  They are no longer the two kids in opposite corners contently playing with their own toys.  Now one has become a bully and has come over to steal the toys from the other kid.

Fortunately for us, remember that U-238 makes up most of the fuel in a reactor.  U-238 does not undergo fission when it absorbs a neutron, unlike U-235.  Thus, U-238 does not release heat when it captures a neutron.  But because it makes up about 97% of the reactor core, it can absorb much more neutrons than the fissile U-235.  Thus, when the reactor begins to heat up, the U-238 begins to infringe on the U-235 and begins to stifle the U-235.  U-238 absorbs more of the neutrons in the range that the U-235 is reacting with neutrons, meaning that there is less neutrons available for fission reactions.  This is directly related to the power of the reactor.  Thus, as the temperature of the reactor gets hotter, fission in the reactor actually begins to shut itself down!

This is one part of the negative feedback coefficient in modern reactors.  You see what I mean when I say that modern reactors can be inherently safe?  We can take advantage of such mechanisms to make reactors inherently safe!  I don't know about you, but this just makes me get hot all over!  Just kidding...

Safety at the hands of Physics

I have to say that I was really impressed at the response I got to my video.  The idea of passively safe nuclear power seems to strike a chord with a lot of people, especially given the current situation in Japan.  Knowing that if the Fukushima Diiachi nuclear power plant had been built with modern Generation III technology what we have seen happen over there would not be possible is a very intriguing notion.  I have been claiming for the last few weeks that the Fukushima incident couldn't have happened if it was a modern reactor, and I bet by now you are sick of me saying this without giving you proof.  So here we go...a little proof.

As it turns out, passive safety systems are both numerous and complex in design.  It took me quite a while to pour through texts talking about passive safety systems and decipher whatever code they were using.  It seems that nuclear engineers are as keen on using acronyms as the military is, which will be interesting being that I will be a nuclear engineer in the Navy.  Anyway, I am going to give you a warning that passive safety systems are extremely complex, often depending on multiple valve systems and thermal properties of materials that can be hard to follow.  My eyes are still crossed from reading about them, but I think I have boiled it down to several key ideas.  This, and I am blaring the Mumford and Sons right now to get my mind in the right place, which I highly recommend to everyone.  Maybe they can help us weave through this just a little to understand the premise, to help us gain the proof we are looking for.

As I mentioned above, there are many types of passive safety.  The one I talked about in the video was something known as a negative feedback mechanism.  Such mechanisms are designed to stop the reactor from continuing to heat up as it gets hotter.  Doppler broadening is one such mechanism.  The reactor I talked about in my video used the high heat capacitance of liquid metals to pull heat away from the reactor.  These systems are designed to keep the reactor from running away,  so that they operate at a safe temperature even when all cooling is lost.  They really interesting in themselves, but I will defer taking about these as I want to talk about the type of passive safety currently at hand; the type that would have prevented the disaster at Fukushima.

You probably heard people referring to something called decay heat when they were talking about Fukushima.  You see, the decay heat was the cause of the problem when it came to keeping the reactors under control.  What is decay heat?  Well, after fission takes place, daughter products from the fission reaction are left over.  These are just the split halves of the nucleus that underwent fission.  The daughter products are often extremely unstable themselves causing them to decay further.  Unlike the fissile material in the reactor (the nuclear fuel), the daughter products don't need neutrons around to decay.  So even when the reactor is shut down, the daughter products are decaying and releasing heat.  This is why the reactor must be cooled even after the reactor has been shutdown.  It is this cooling that failed in Fukushima.  There were many redundant systems in place to ensure that cooling would always be working, but apparently engineering redundant systems is not enough to insure against the improbable.

This is where passive safety steps into play.  So what exactly do I mean when I call something passively safe?  I mean that the system does not rely upon outside sources to operate it.  It does not need a back up generator or batteries, or even power at all.  They rely simply on the never failing laws of physics.  And if those fail, we have bigger problems to face than a nuclear power plant if you catch my drift. 

There are many types of passive safety systems that are designed to ensure that decay heat is pulled away from the reactor once it has been shutdown.  They all work off the same basic ideas though, so I will avoid the metric ton of technical information it would take to fully explain these and talk just about the basic design that they all share (in general).  If you really want to read about them though, I say more power to you and point you to this article.  For the rest of us, lets just stay here on Earth while discussing this.

The first source that powers passive safety systems is good old gravity itself.  Modern light water reactor (most commercial reactors around the world are light water reactors) make use of gravity to deliver water to the reactor if the cooling system fails.  Fukushima relies upon pumps to deliver water to the reactor, but once the pumps no longer work, they are just kind of left up a creek without a paddle.  When modern systems loose cooling abilities, water can still be delivered by water storage tanks that are placed above the reactors.  Modern reactors have to have a water source located above the reactor so that water can gravity feed to keep the core cool.  It is kind of like using a water tower to store water.  Even when the power goes out, the town will still be supplied water thanks to gravity!

Some reactors used tanks that are pressurized.  When a loss of coolant is detected, water automatically is injected into the reactor through valves which open based on pressure differences.  When a reactor looses coolant, there is a pressure drop in the reactor vessel which causes the valve to open and water to be delivered to the core.  Note that this does not take any "intelligent" input.  It relies on physics alone.

So, this is great...we have water delivered to the core, but last time I checked, water can't pull that much heat away from the core if it is just sitting around the core.  The water must have the heat removed from it as well.  This is done by circulating the water through a device known as a heat exchanger, where the heat in stored in the core water is transferred to a medium that can cool to the atmosphere.  This is necessary as we only want limited amounts of water to contact the core, and we want to keep this water contained in a closed loop.  We can't just dump the water that has been through core into the cooling ponds.  Besides the safety reasons, I get the feeling the NRC just wouldn't like this.  Anyway, the problem is that we need to circulate the cooling water through the heat exchanger without the use of outside power.  Sound impossible?  It's not.

I grew up in a house that had a ranch behind it.  There were no houses for miles behind where I grew up.  In fact, you couldn't see any houses behind my house when I was young.  You could only see Pikes Peak.  I freaked me out when I got up early one summer morning and there were all the sudden houses back there in the distance.  Did somebody build them overnight?  Not exactly...  You see, there was a hill somewhere between where I lived and the houses that were back there.  Thanks to the hill, you couldn't see the houses most of the time, but on that morning when the air was cool and the sun was strong, the heat from the houses actually appeared to make them rise from out of nowhere.  My point:  heat rises!

Ok, that was a long winded and perhaps pointless story to just get that across, but I had to do something to break up the monotony.  Anyway, heat rises!  Passive safety takes advantage of this.  It turns out that we can use this fact as well as gravity to circulate the water through the reactor.  The hot water or steam rises up through a heat exchanger which cools the water.  After cooling, the water uses gravity to return back to the reactor.  This is done using several different techniques, but I will spare you explanation of the methods.  The cool part is that natural convection and gravity can circulate the water without having to use powered pumps!  Nature has allowed us to build a pump that needs no electricity!  The only downside to this part of the passive safety system is that a person must manually initiate this process.  Physics does not automatically turn this one on for us, but at least we will know that it will always work.  It doesn't need those backup generators that have been washed away by the tsunami!

There has been a lot of discussion lately about whether we can safely harness the power of the nucleus.  Some tend to view it as we are simply trying to play with the power of God by taking on such endeavors.  I think that the safety part of the industry is just an engineering challenge though.  We can do it, though we might make a few mistakes along the way.  In general though, I think we can build nuclear reactors to be as safe as anything else in this world.

Ok, I tried, but I can't hold it any longer

I know that I said I was going to leave Fukushima and discuss other things for a while, but I think it is appropriate to give just a little attention to it due to recent happenings.  I know the question in floating around in everybody's head right now is "Is Fukushima another Chernobyl?"  Before I get to that though, let me address a few other issues.

I must first do a little pulling of my own foot out of my mouth.  Recent reports are indicating that the problems at the Fukushima Diiachi plant seem to have released much more radiation than I ever thought they would.  Reading reports about the contamination levels near the plant itself show some areas that have fairly high levels of radiation.  It looks as if there will be some areas that some people will not be able to go back to and there will definitely be some areas which will need to be decontaminated before people can live there again.  At this point, it is looking like cesium-137 will be the largest factor for contamination as radioiodide (radioactive iodine) will have decayed away within a month or so.  I just want to be upfront and say that there is contamination from the incident at Fukushima.

So is this another Chernobyl?  Many people, including the media in general, seem to be thinking that the answer to this question has become a definitive yes since the nuclear accident level was raised to a 7, the highest level when it comes to nuclear accidents.  Since Chernobyl has been the only nuclear accident to reach this scale in the past, it is logical to assume that Fukushima has become another Chernobyl.  In reality though, that is not really how the rating scale works.  Though they are both rated a 7 now, they are still in totally different categories.

As the nuclear industry is quickly learning, maybe the current rating system does not have enough resolution to distinguish between such incidents.  It is kind of like trying to separate the world into two types of people, say males and females.  That doesn't really describe different types of people that well you see.  There isn't enough resolution.  From the current reports, it looks like the amount of contamination estimated to be released by the nuclear power plant at Fukushima is about 10 times less than what was released during Chernobyl.  So why are they both classified the same?  Well, the rating system is quantitative, meaning that when a power plant releases so much contamination it is automatically given the corresponding rating.  Fukushima has reached that level and is thus given a 7 rating.

We also need to keep in mind that not all emissions of radioactivity are equal.  For the rating system, the radioactive emissions are measured in Becquerels, which is a unit of one radioactive event.  The higher the amount of Becquerels released, the higher the activity of the contaminated area.  Being that this is just a description of the radioactive decays per second, it doesn't really tell about the level of contamination.  You see, what has mainly been released due to Fukushima is cesium-137 and iodine-129.  The iodine has a fairly short half-life, meaning that most of the iodine-129 released is all ready gone.  The cesium has a longer half-life, so the will be dealing with that for a years to come, but it will all be gone within a reasonable time frame.  It is also not as big as a threat to human health as some radioactive substances.  Chernobyl on the other hand had quite different releases.  Because the reactor actually exploded, parts of the reactor core itself was spread all over the countryside as well as into the atmosphere.  This includes substances such as uranium-235, uranium-238, and plutonium-239 as well as other fission daughter products such as cobalt-60.  These all are much more hazardous to human health than cesium-137 and have much longer half-lives.  Though the Fukushima plant's releases are estimated to be about 10% of what was released in Chernobyl, the danger that the releases pose to human health is no where near what was seen  by Chernobyl.  Can we call the Fukushima incident another Chernobyl?  I still don't think so...

And what about the fact that we have not seen any direct deaths from Fukushima?  I mean even the worst that the workers have seen is some minor skin burns, which is much different than what was seen at Chernobyl.  There were 56 direct deaths from the events at Chernobyl.  There have been none from Fukushima.  In this way, Chernobyl was a much different animal than Fukushima.  Also keep in mind that the Japanese don't have the iodine deficiency in their diets that the Russians did near Chernobyl.  Because of this, the thyroids of the Japanese will not absorb the radioactive iodine like the Russian's thyroids did, and therefore they don't have as high of chance for developing cancer. 

With the upgrading of the incident rating to 7, many people as well as some of the mass media are led to believe that the situation is getting worse there.  This just simply is not true.  This rating is based on what has already happened, and probably due to the happenings of the first couple days after the earthquake.  The rating system is based on releases and harm to the surrounding area.  It is not a measure of the threat level of the current situation.  Currently, the reactors are under control and the cleanup process is beginning.  There is still concern about one of the spent fuel pools, but there is no longer the threat of a reactor meltdown. 

I want to conclude with an interesting phenomenon I am observing.  It seems that some people are realizing that a worst case scenario at a nuclear power plant is not as bad as what Hollywood or Greenpeace led them to believe.  There will not be any mutant Godzillas attacking Japan and there is no massive death toll from the incident.  In fact there is no death toll accompanying what happened there.  Does nuclear power have risk associated with it?  Of course it does!  But the point is that so does everything else we do.  Energy is not a clean business, no matter what type you are talking about (and yes that includes solar power).  Just maybe the Fukushima incident will show the world that our fears about a nuclear incident are a little bit romanticized.  I would even call them exaggerated.  But again, people are less afraid of what they have experienced.  After all, the world didn't end over the last month.

As a quick aside, I have to partially attribute the explanation I have put together here to discussions that Dr. King and Dr. Kozak have held in my classes.  Dr. King is an expert in nuclear energy and Dr. Kozak is an expert in radiation risk and health assessment.  Some of what I have mentioned here is a product of their opinions and discussions.  I hope that I passed a little of their expertise in the field to you.