Only a week ofter the Bunaco trip, we were set to take another one. This time, we headed out onto the Shimokita Peninsula to a town called Rokkasho. Sitting on the handle of the hatchet that is Shimokita, it is easily viewable from a distance because of its iconic wind turbines.
Shimokita is famous for it's remoteness. Some say it is one of the last truly rural parts of Japan. The low population makes it a perfect place to locate things that nobody wants to live next to. In this case, Rokkasho is home to an enormous energy industrial complex.
When I say energy, I mean a bunch of different conventional energy forms all in one place. As I mentioned before, the "hatchet handle" is dotted with hundreds of wind turbines, generating clean energy for the residents of Aomori using the strong winds that commonly gust through the narrow peninsula. Underneath the wind turbines sit solar panels that soak up the suns rays on those lucky sunny Aomori days. We stopped at a small observation deck to take a peek at the solar farm and to take pictures of the massive wind generators whirling rapidly in the strong winds.
On the drive through, we passed by a field of massive silos, each storing hundreds of thousands of gallons of crude oil in reserve in case of emergency. It's said that there is enough crude oil stored here to power Japan for 3 months in case something goes terribly wrong.
We spent a fair amount of time at a hot spring building out in the middle of nowhere. It was called Rocca-Pocca, and while it was a fairly normal large tourist and bathing building, they boasted the cutest set of mascot characters ever!
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| The Rocca-Pocca's six bathing cuddlies. |
Finally, the most important and outstanding facility is the nuclear waste storage and remediation facility. Getting inside required a large amount of security clearance, as would be expected from any facility handling highly radioactive material. They gave us a tour around the facilities, most of which we could only look at from a distance through windows.
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| Nuclear Recycling Facility |
The JNFL complex contains 6 facilities, 2 of which are still under
construction. They have a uranium enriching plant, used to make mined
uranium usable inside a reactor. The have a low-level waste disposal
center, that handles and stores drums of various contaminated items,
like safety equipment, tools, clothing, or liquids. There is a vitrified
waste storage center that keeps the nasty fission byproducts turned
into glass. There is a spent fuel storage facility, which keeps spent or
partially spent fuel rods underwater awaiting reprocessing or reuse
(this facility is currently filled to max capacity with fuel rods since
Japan shut down all their nuclear reactors). There is a reprocessing
plant (near completion), as mentioned before, which breaks apart used
fuel rods and extracts usable fissile material. Finally, the is a MOX
fuel fabrication plant (expected completion in 2017), where they plan to
produce experimental "Mixed Oxide Fuel" rods out of reprocessed uranium
and plutonium, which can be used similarly to standard uranium fuel
rods in light water reactors. For more detailed information, visit
http://www.jnfl.co.jp/. They have an English site too!
(and now for a lecture on nuclear energy production and safety)
Before we went inside the nuclear fuel reprocessing facility, one of the participants remarked, "wait, we're actually going inside there? Oh crud...," which is also when I realized that many of these participants, like most of the world's population, don't know how nuclear fission and radioactive decay work.
To understand how nuclear waste storage and remediation works, you must first understand what nuclear fission does and how to safely handle nuclear waste. Inside a nuclear power plant (light water reactors), there are enriched uranium ("fissile material") fuel rods. These fuel rods get blasted with neutrons, which have a chance to be absorbed by some of these fissile material atoms. If it is absorbed, the resulting atom becomes an unstable isotope. Most of the time, these unstable isotopes will undergo fission, where the heavy isotope splits into two smaller atoms (called "fission byproducts"), releasing kinetic energy, gamma rays (x-rays, essentially), beta particles (free electrons), and 2-3 more neutrons to get soaked up by other uranium or plutonium atoms and continue the fission chain reaction. It is the massive amount of kinetic energy released, turned into heat, that provides the majority of energy used to produce electricity.
After many years in operation, the fuel rods become lean in fissile material. It is at this time that the reactors are shut down and the "spent" fuel rods are replaced with fresh ones. But what should be done with these spent fuel rods? The main concern is, what exactly in left in the spent rods?
As I mentioned before, fissile materials turn into fission byproducts when they split apart. What exactly the fission byproducts are is entirely up to probability, as a fissile material can split into combination of byproducts as long as the resulting mass is the same. Basically, what's left inside the fuel rods is a smorgasbord of various metals and gases, most of which are unstable and undergoing radioactive decay. These materials are NASTY, and you definitely don't want them getting out into the environment. This is why all fuel rods are encased in a metal "cladding" that seals all the crud inside and doesn't let any of it get out.
So hey, the fission byproducts are sealed, so there's nothing to worry about, right? Wrong! There is the problem of RADIATION. Oooooh I used a scary word. But what is radiation? Visible light is radiation. Your microwave and toaster use radiation to cook your food. The radio in your car operates on radiation. What's so scary about radiation?
Radiation itself isn't necessarily harmful. The key word you should be concerned about is "ionizing radiation". This is radiation that will fundamentally alter the atoms and molecules inside your body, and can therefore cause cell and DNA damage, the scariest of which would lead to massive cell death or malignant cancer. You don't want ionizing radiation traveling through your body. This type of radiation comes in 3 forms: alpha particles, beta particles, and gamma rays.
Alpha particles, essentially a Helium nucleus with no electrons, can be pretty nasty because they go around stealing electrons from other atoms they come into contact with. We tend not to care much about them because they are large enough to collide into other matter and can't travel very far. If one of these particles did get far enough to hit you, it would stop before it even made it past your clothes or the layer of dead skin cells that surround your body. Since there's usually no contact with living tissue, alpha particles aren't dangerous unless an alpha particle emitter (such as Radon gas) is ingested or inhaled. The inside of your lungs don't have a protective layer of dead cells like your skin does, allowing alpha particles to bombard sensitive tissues.
Beta particles, on the other hand, are just free flying electrons and are much smaller than alpha particles. They are able to travel much further through matter, usually making it through several meters of air or tens of mm through human flesh. These little electrons fly through the empty space of atoms' electron clouds and slowly lose energy when it collides with nuclei. It'll eventually settle and ionize an atom, leading to fundamental changes in that atom's properties. Beta particles are a bit more scary because they can travel several meters through air. If you're standing next to a beta particle emitter (like most fission byproducts), those beta particles are showering upon you in all their carcinogenic glory several centimeters beneath your skin. However, several millimeters of aluminum is enough to stop almost all beta particles, so wearing an aluminum foil hat would actually be fairly effective at protecting your brain. The main concern again would be if you inhale or ingest a beta particle emitter. Your internal organs would be getting showered with electrons, which leads to serious microscopic (nanoscopic?) internal destruction.
Gamma rays (also called x-rays), finally, are the most dangerous of the ionizing radiation family. They have no mass and travel as pure energy, and so are even more difficult to stop than beta particles. Half of emitted gamma rays will travel through 150 meters of air or 6 cm of concrete. Lead (or plumbium) is by far the best gamma blocking substance, taking only a cm to stop half of emitted gamma rays. That's why the dentist lays a heavy lead apron on your body before taking an x-ray image. This kind of radiation is what we are terrified of, despite the fact that gamma radiation is common in normal daily life, such as medical screenings, normal cosmic radiation, emissions from the ground, and emissions from potassium (like in a banana). Yes, eating a banana irradiates you.
So now that we know what ionizing radiation is and why it's dangerous, how dangerous are spent fuel rods? Well, alpha particles weren't much of a concern to begin with because you could essentially bathe in an ocean on alpha particles with no ill effects (actually it would probably kill you, but not through radiation-caused cancer). Meanwhile, beta particles won't make it further than several meters from the fission byproducts, assuming it even gets past the cladding. The gamma rays are the things we have to worry about.
Fission byproducts, being mostly unstable elements undergoing radioactive decay, release lots of beta and gamma radiation. Nuclear safety controllers first need to ensure that the source emitting the radiation (the fission byproducts) doesn't get spread around. That's why they have cladding. Since all the nasties are contained within the fuel rods, the next step is to prevent the radiation that inevitably comes out of these fission byproducts from actually hitting anyone.
That is where the nuclear waste storage and remediation facility comes into play. First, as I said before, the fuel rods aren't EMPTY. They are simply "lean" in fissile material (uranium and plutonium). Reprocessing the fuel rods involves chopping the rods open and chemically separating the cladding, nasty fission byproducts, and still useable fissile material from each other. The reprocessed fissile material is then reused in new fuel rods, while the nasty fission byproducts become "high level nuclear waste", which spew beta and gamma radiation all over the place.
So what do they do with the high level nuclear waste? They turn it into glass! It's called "vitrification", and it reduces the volume of the nuclear waste tremendously. This allows them to pack the waste into tall steel canisters and slide them 9 high into 10m deep holes in the ground. The canisters emit a massive amount of radiation (enough to be fatal with just 10 seconds of direct exposure), so the burial ensures that any beta or gamma radiation gets soaked up by the concrete. Remember, just 60 cm of concrete is enough to reduce gamma radiation to less than 0.1%. The glass contains boron compounds as well, so any rogue neutrons get soaked up immediately. Some say that nuclear waste is a huge environmental problem, but all of the world's high level nuclear waster can be vitrified and stored safely in a facility the size of a Walmart. I'm fairly certain standard garbage landfills are much more of a concern than nuclear waste.
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| Vitrified waste |
ブナコの観光の一週間後、下北半島の六ヶ所町に行きました。遠くから、ならではの風力タービンが見えます。
六ヶ所はとても田舎です。人が少ないのでコンビナートを建てるのにぴったりです。ここにむつ小川原工業基地があります。
いろいろなエネルギー関係の物が建ててあります。ここに風が強くて風力タービンに丁度いい所です。風力タービンのしたにソーラーパネルがあり、太陽熱発電もされたいます。
施設を通るとたくさんのものでかいサイロも見えます。これは国家石油備蓄基地です。緊急の時、ここに全国が３ヶ月使える原油が溜められているそうです。
次、森の中の観光と温泉のビルがあります。「ろっかぽっか」といいますが、その所のゆるキャラはとてもかわいい！
最後に、一番大事な目立つ所は日本原燃原子燃料サイクル施設でした。セキュリティーが大事なので入るだけでもなかなか難しかったです。バスに乗って色々な施設のツアーをしました。残念だったけどほとんどの観光は遠い所の窓の後ろからでした。
日本原燃原子燃料サイクル施設の中に６つの特別の施設があります。ウラン濃縮工場で原子燃料を作るために天然ウランのU-235を多くします。汚れた道具、服などのあまり危険じゃない放射性廃棄物は低レベル放射性廃棄物埋設センターに入っています。使われた原子燃料の中のもった危険なものがガラスにされて高レベル放射性廃棄物貯蔵管理センターに入っています。使用済燃料受入貯蔵施設でまだ使える燃料が貯蔵されている。まだ未完成な工場が二つあります。再処理工場（２０１４年１０月竣工予定）で使われた燃料ロッドを切り壊してまだ使える物をリサイクルする。その残したものをMOX燃料工場（２０１７年竣工予定）で新しい燃料ロッドを作ることできます。
機械工学の専攻の僕にこの経験がとても特別でした。一生に一回だけ経験できることだったかもしねらいはらとても感謝しています。
（ほかの内容は訳せないので、できれば英語で読んでいただければどうぞお願いします）
