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.

Fireside Chat

I have to first apologize for my bad movie making skills, but here I present me, myself, and I in person to try and give a little perspective about safety in the nuclear industry.  This is an extremely important concept to understand especially as reports about the Fukushima reactors get worse by the day.  I hope not to disappoint any of you who were hoping that some dashingly charming and good looking fellow was behind the stream of rants coming out of this blog.  I never pretend to be any of those things!  And yes, I know that the blanket is awesome.  Before you ask, my mom made it for me.

This is just a quick little trivia piece about what passive safety can do, but the idea is very powerful.  Can a nuclear reactor be designed to be inherently safe?  Yes it can.  The designs for the Generation IV reactors are all inherently safe like the advanced fast reactor in Idaho.  Subjected to the worst case scenarios, they will shut down safely and use the laws of physics to keep them cool.  How awesome is that!  I will get more technical about passive safety systems in the future, but I just wanted you to realize that we can harness the power of the atom and do it safely.  Granted, these designs are somewhat different than what is currently in use, but hey, we haven't built a new reactor in more than 30 years.  All the more reason to get the industry going again.  It will actually be safer for the country if we replace the old reactors with new reactor technology.

Think Fast!!!

In my last article on the thorium fuel cycle I threw the bait out hoping that you might bite...now it is time for me to sink the hook.  I made a lot of statements about how using thorium would lower the risk of proliferation, would reduce the waste issues involved with current reactors, and would even make nuclear power more of a long term energy solution.  How would all this come into play simply from changing the fuel we use?  Well, I explained some of the basics in the last post, but many of the answers come from a reactor design that was taken off the table almost 30 years ago.

The fast breeder reactors were so exciting that it seems nuclear engineers were getting high over the idea of them back in the early 80s.  Let me first say that I wanted to find a cool picture to put with this post...my advice is that you should think before typing "breeding" into Google images.  I will spare you guys the cool images this time.  Anyway, some of you guys may have heard the term breeder reactor before and wondered what all the buzz was about.  You see, the idea of the breeder reactors made power generation of fission based nuclear reactors almost limitless.  Why?  Because when operating a breeder reactor, you create more fissile material than you use to run the reactor.  Not impressed?  Well, remember back to my first post on how a nuclear reactor works?  It is the fissile material that we need in the fuel so that we get heat out of it.  This is the material that will capture neutrons and spontaneously undergo fission.  When we take natural uranium out of the ground, less than 1% of it is fissile (actually about 0.71%).  When it comes out of the ground, we can't really use it to power a nuclear reactor.  Some of the non-fissile U-238 must be removed by refinement so as to raise the percentage of fissile U-235 in the fuel to between 3% and 5%.  Phew, tired of numbers yet?  My point is that the amount of fissile material we have on Earth is pretty small, and considering that this is what we need to run nuclear reactors, this is kind of a big deal.

Fortunately, this is not a killer blow to the nuclear industry.  You see, there are reactions which certain materials can undergo by which they become a fissile isotope.  What do I mean?  I mean that certain reactions create more fuel for our nuclear reactors.  This is going on in every nuclear reactor around the world as we speak.  The material is known as fertile, which just means that it can be "bred" to become fissile so that it will undergo fission and power the reactor.  Uranium-238 is one of these fertile substances.  Like a fissile material, it also has the ability to absorb a neutron.  When it absorbs a neutron though, it does not undergo fission but instead transforms into the infamous plutonium-239.  This is a fissile isotope and is the isotope well known as the material for nuclear weapons.  As you can probably see, we are now starting to run into the problem that they had with breeder reactors back in the 80s, but I will get to that in a second.  The plutonium-239 that is produced while the reactor is running is responsible for the fuel being able to last as long as it does in a nuclear reactor.

Unfortunately, current reactors are not very efficient for turning fertile materials into fissile materials.  This is a result of modern reactors being what are known as "thermal" reactors.  This simply refers to the energy at which the neutrons are causing fission.  Today's reactors largely depend on the fact that U-235 has a much higher probability of capturing lower energy neutrons.  This is what "thermal" refers to...the neutrons are at low energies meaning that they are moving slower.  Thus, we use materials in our reactors that slow down the neutrons so to make most of the neutrons in the reactor to be what are considered slow neutrons.

As it turns out, slower neutrons might be ideal for inducing fission which is great for making heat, but they don't take advantage of the large amounts of fertile material we have in the reactor.  You see, we can create more fissile material and thus more fuel if we speed up the neutrons and operate the reactor in what is known as the "fast" range.  Yeah, I know, really creative...  Anyway, with fast neutrons, the uranium-238 in the fuel has a better chance of capturing a neutron and turning into plutonium-239, which is fissile!  Just by operating reactors in the fast regime, we can create more fuel than we burn!  Amazed yet?  Well you shouldn't be because there is still a bit of a problem with this.

For good reason, people were afraid of operating types of reactors that bred plutonium-239.  We are again running into the idea of nuclear proliferation, and here in a very big way.  The thermal reactors that we are running today operate off lowly enriched fuel you see.  This means that only about 5% of the fuel is fissile.  In order for a reactor to run under the fast conditions that I talked about above, they need to have fuel that is enriched so that about 20% of the fuel is fissile.  So now we are talking about 20% of the reactor fuel being plutonium-239.  How easy do we want to make it for people to get their hands on nuclear weapons material?  Not very would be the right answer, so the industry was forced to abandon this idea.  Now though, the idea is coming back in a big, big way!

Remember back to that thorium stuff I was talking about at the beginning of all this?  Well, it seems to hold the key to making nuclear a long term energy solution.  Thorium in its natural state does not actually contain any fissile material at all.  That means that we must enrich it, meaning we must add fissile material to it before we can even think about putting the stuff in a nuclear reactor.  As it turns out though, the natural isotope of thorium (Th-232) is a fertile material.  Now is when your eyebrows should be raising and that smile of complete amazement should be starting to creep across your face.  When Th-232 captures a neutron, it becomes uranium-233, which is fissile!  And even better, it isn't a weapons material!  Hallelujah!  We are saved!

The bottom line is that by putting thorium-232 into a breeding type reactor, we would create more fissile material than would be consumed by the reactor.  Another method of creating fissile material is by simply created a sort of blanket made of thorium-232 which would just be placed over the reactor.  The fast neutrons escaping the operating reactor would be sent into the blanket where they would be captured by the thorium-232 and turned into fissile fuel.  Doing this, reactors would basically be able to power themselves indefinitely.

What limits our current power production from our fuel is the amount of fissile material present.  Currently, the fuel is being run in the reactors until the amount of fissile material gets too small to keep the chain reaction going.  The fertile material is not being used, meaning that we are throwing away more than 95% of the energy left in the fuel when we consider the fuel "spent."  Breeder reactors would change this.  All the material in the fuel could be caused to undergo fission!  This is a powerful idea in the way that it gives us the ability to access virtually limitless energy as thorium is quite abundant in the Earth's crust.  About 5 times more abundant than even uranium.  This should be more than enough fuel to power us until the time where monkeys give birth to another race smarter than ourselves who can solve the problem of fusion power.  I might be missing the concept of evolution here...anybody?

So is the energy crisis solved?  Well, not quite.  There are several industries which need to be better developed before we are ready to launch into breeder type reactors.  First is that we will need to reprocess the fuel as to remove the fission fragments from the fuel.  This is just part of the process, but currently reprocessing of nuclear fuel is not allowed in the United States.  The tide seems to be changing on that though.  I mean with much lower risk of proliferation, there is really no reason not to reprocess the fuel.

The idea of geological storage must also be solved.  Currently we don't have a place to put the high level waste, and though the amount of high level waste coming from breeder reactors is much lower than that from our current reactors, there is still waste that we must store.  I will talk more about this in the future, but I just want you to see some of the issues that must be confronted before we can really depend on this energy source.  Are these challenges worth overcoming?  I would argue that if we want a viable energy solution in the near future, we must overcome these challenges.  Believe it or not, we are a lot closer than one might think to solving all of these problems.  It is largely a matter of politics now, but I am going to venture to guess that nuclear power just might become the first viable renewable energy resource.  Nuclear power is going to solve the energy crisis like anybody would want to solve a problem: by breeding!  Sorry, couldn't resist.  And yes, I said renewable.

What the heck is Thorium?

Quick!  When I say uranium, what do you think of?  If I say plutonium?  Being the psychic that I am, I know that images of yellow radiation triangles are flashing across your mind with flashing lights and alarms going off.  Your mind starts flashing danger warnings to you as visions of mushroom clouds start dancing in the back of your head.  Am I close?  These elements are perceived now as two of the most dangerous elements on Earth, and because of this, it is no mystery as to why people are so adverse to nuclear power.  The raw materials themselves which the industry has been built around are the most dangerous things known to man kind!

This isn't really true as you could probably tell from the loud rolling of my eyes seen between the lines of my comments.  Why would people be lead to believe such statements?  Well, the truth is that the industry did it to itself.  You see, the nuclear power industry has always had kind of a free ride as far as development goes.  This stems from the world governments having such a large interest in the power of the atom:  not in nuclear power per say, but in nuclear weapons.  The research needed to be done to learn the fundamentals of nuclear fission reactions was all geared toward weapons research.  Much of the nuclear research done to this day is paid for by the department of defense.  It is a horrible history and a fact that the industry will be haunted by for a long time, but weapons research is why we have nuclear power.

Because of this, the funds geared toward nuclear research has been spent learning about the materials suitable for weapons production.  As you might guess, it is uranium-235, uranium-238, and plutonium-239 that got a lot of the attention.  Labs like the one in Los Alamos, New Mexico characterized the fission behaviors of these elements really really well.  It would have been illogical for the nuclear industry to ignore the data being handed to them on the performance of such fuels.  Thus, the private industry was enticed into designing the civilian reactors around what we knew:  U-235, U-238, and Pu-239.  The nuclear power industry became a parasite of the weapons program since that is where the funding was going.  At this point, the industry was just asking for proliferation issues, but I will get to that later.

Currently, the nuclear power industry faces many challenges which all trace their beginnings back to the weapons legacy of the system.  Fortunately for the industry, it turns out that uranium is not the only option for usable fuel cycles in the reactors.  In fact, uranium isn't even the best type of fuel for commercial power production!  This might be the bit of good news that the nuclear power industry needs to get back over the hump of public skepticism.

It is not a magic bullet to the issues facing nuclear power, but the thorium fuel cycle is the way the the industry will separate itself from its weapons legacy.  You see, the weapons program that the government was funding did not care what materials were optimum for power production, but only those that were optimal for building the "big stick" that the country was founding its defense strategies upon.  Now though, the ball is in a different court.  We aren't so much facing a nuclear holocaust anymore so much as the world becoming a giant human oven.  Nuclear power is seen as the forerunner for mitigating the human effects on global warming.  What does this mean?  Well, I hope that it means that funding will be sent back toward developing a nuclear fuel cycle optimized for power production, but I guess only time will tell.

So what is better about thorium?  That is probably the question that is on your mind at this point, or at least it is now since I just made it so.  Many of you probably have never even heard of thorium or the thorium fuel cycle which I only know because I had never heard of it before reaching graduate level classes in nuclear engineering.  As it turns out, it is a pretty well kept secret and it should definitely not be.  If you go back and dust of that old periodic table that you have from the chemistry class you took in high school, you can find thorium two spaces to the left of uranium in that infamous f-block of the table.  Yes, there it is, a naturally occurring substance that nobody ever concerned themselves with.  This is the element that could be the solution of the world's energy problems for thousands and thousands of years.

The biggest selling point of designing reactors for thorium fuel...the abundance of it here on Earth!  In fact, thorium is between 3 and 4 times more common in nature than uranium.  If you have been following me for a while, you have heard my rantings on how much uranium we have in reserve.  Thorium being this much more abundant means that solar and wind power would not have to be developed for use any time soon.  In fact, there is enough thorium now to have powered mankind at current demand since the first man was born out of a monkey.  Not that I believe this is how mankind came about, but you get my point.  We have a lot of power available with a thorium fuel cycle.  Of course, we have enough uranium to power us into the quite distant future as well, so why the heck would we want to spend so much on research to redevelop the technology?

There are many many reasons that thorium is a much better fuel cycle and I hope to address more of them in future posts in more detail, but I am going to hit a few of the basics here.  First of all, like I stated above, the thorium cycle will take us away from the ties the industry has to nuclear weapons.  This is not only true by taking uranium out of the picture, but also by putting up major barriers to nuclear proliferation.  Unlike uranium, thorium contains no natural isotopes which are fissile.  By this, I mean that unlike uranium, thorium will not undergo nuclear fission in its natural state.  This by itself means that thorium cannot be processed or used to create a weapon.

Thorium is found completely in nature as thorium-232.  In a reactor, very very small amounts of material that can be used to create a weapon are generated.  Beyond this, many of the fission daughter products which result from nuclear fission in the reactor have very short half lives.  This means, in the case of thorium, that what comes out of the reactor is a very strong gamma-ray emitter.  This provides two types of protections as far as nuclear proliferation goes.  It makes the waste very easy to detect if it were ever to be stolen, and it makes the waste very hard to work with.  In order to create a weapon from what comes out of the thorium cycle, one would need special facilities to do it as getting near the waste to process would kill them.  All management of the spent fuel is done remotely, including the reprocessing of it for reusing the fuel.  Take away message, steeling the fuel and creating weapons from the spent fuel is pretty much impossible eliminating the fears we have of this with the uranium fuel cycle.

Another major benefit is the much shorter lifespan of the waste from the thorium fuel cycle.  Like I said above, the half lives of the wastes from the thorium fuel cycle are much much shorter.  Instead of looking at half lives on the order of tens of thousands of years, we are looking now at half lives on the order of less than 100 years.  The waste storage issues are made much simpler with the thorium cycle, which a much needed boost to nuclear power.

There are many more advantages to the thorium cycle, but I will defer discussing them to a later time because I feel that I have hit you over the head with enough technical information for one day.  If you are really curious though and want a technical explanation of the thorium cycle, check out this report.  It is long and technical, but it is very informative.  I wouldn't read it if I were you though...It is spring time and you should be thinking about going outside at this point instead.

Fukushima Update and a Few Final Words on the Issue

Contrary to what intuition might tell you, the reports of the amount of radiation being detected around Fukushima are actually quite calming to those in the industry.  It seems that everyone is once again starting to breathe normally instead of seeing my professors walk around with that big vain popping out of their forehead and their eyes slightly bulging.  The stress is subsiding, and it is noticeable when looking at how those in the industry are behaving.

There are of course reports of large amounts of radiation being released into the ocean and into the area immediately surrounding the power plant.  Some places are reporting levels upwards of 5 million times greater than the regulatory limit.  A good article on the situation is given here if you are interested.  There is contaminated water all over the sight, and I would venture to guess that some of it is leaking.  I mean, if you have been paying attention to how much water they have been dumping over the reactors as well as to the methods they are using to do it, one would be crazy to think that there was not going to be any contaminated water hanging around when all was said and done.

Why would this in any way be relaxing?  Well, it is indicating that the worst is over.  I would think of it this way:  we have started to worry about the secondary issues that a few weeks ago we did not even care about.  They knew that there would be left behind material that would be contaminated due to the efforts to cool the reactor, but at the time, it was what had to be done.  We gladly went with the efforts because they were what was necessary to get the situation under control.  It is kind of like in the movies when the hero has to use force to get the villain under control.  At that moment, they aren't worried about the well being of the walls in the house or the furniture in the living room when they are in mortal combat.  In the end though, if somebody wants to continue to use the space where the violent rumble took place, it must be eventually cleaned up.  They knew that dumping that much water over the reactor like that would make a mess, but it was necessary.  Now they need to clean it up.

Like it says in the article above, the releases of contaminated water into the ocean so far have been controlled releases of low level radioactivity.  Why would they do this?  Well, as the article points out, they are finding some highly contaminated water at the sight.  At the moment, it is not known where it came from or if there is more coming.  It could be due to a leak in a valve somewhere, maybe the spent fuel storage pools, or even be coming from a breach in the reactor containment vessel itself.  The truth is that nobody knows.  As an aside, it is now not such a big worry if the containment vessel has been breached since cooling has been restored to the cores.  Anyway, the reason the low level waste is being pumped to sea is to make room in the storage tanks to store the contaminated with the higher level of radiation.  It is not a dire type situation though, which is signaled by the fact that they are containing it.  If the situation was so bad that this stuff was going to leak out and contaminate all the water in the area, they would have already started pumping the highly radioactive water out to sea.  In the long run, it is much less dangerous out there than it would be at the Fukushima sight.  After all, we aren't going to form a Godzilla from the stuff.

Talking to Dr. King (the nuclear engineering department head here at CSM), he seems to think that the biggest priority still to be attended to is fully restoring the cooling systems to the spent fuel pools.  Though he seemed to think that if something was going to happen to the pools, it would have happened there already.  This is very calming as it means the worst is confirmed to be done with.  To me, it seems that they are now transitioning from disaster containment mode at the sight to starting to worry about cleaning up the sight.  For those of us that have been closely following the events, this is the moment where we can finally start to relax.

There were reports as well as plutonium being found in the soil near the power plant.  I don't want to dwell here, but let me tell you that it was an extremely small amount.  The levels being detected were less than 1 Bq per kilogram of soil.  I know, again with the weird units, but let me explain.  1 Bq is an extremely small unit of activity.  1 Bq means that there is one radioactive event going on per second in that kilogram of soil.  To be of any concern, we would need to see levels hundreds of thousands of times higher than the levels being detected.  The levels being detected are roughly equivalent to filling your nalgene water bottle one one-thousandth of the way with food coloring and trying to use this to color nearly 400,000 Olympic size swimming pools (h/t to Dr. King again for this one).  You are more likely to have negative effects from radiation due to somebody peeing in the pool than from the trace amounts of uranium being detected.  In other words, we are very good at detecting radiation and sometimes this causes alarm.  We can't detect any other types of contaminants with these low of levels.

I have devoted a lot of time over the last few weeks toward educated and learning about what is happening at FukushimaFukushima incident for a while as I think dwelling on it too long just causes me to rant, and nobody wants that.  I do encourage any who have questions about what is happening to feel free to ask.  I will be happy to tell you what I know and find out what I don't know.  For those of you who are really hooked and want to really keep a close watch on the situation there, I reference you again to Dr. King's facebook page on Fukushima.  I do have to thank you guys for listening to what I had to say about the situation.  It was probably way more therapeutic for me than it was informative for you guys!  Time for therapy is over now though, so lets get back and do some more learning.  I think it is time for me to support all the statements I have been making the last few weeks, so here we go!