Large Hardon Collider

[Eliseos]

I still stand by Physicists having the best names/acronyms.

Also, woe is me. I forgot one of my notebooks in lab on Wednesday night, and I'm probably never going to get that back. Gogo losing all of my notes for a class a few weeks before the final.

[Max™]

Well, I meant the water and coolant and shielding and shit too, so I just tossed all that in with the control rods.

You said they did something non-standard though, or was it lots of them?

It made it sound like they had something like a new inner shielding structure within the pile to deal with the center/bottom issues, or did I get that wrong?

[Kryssan]

Well, I meant the water and coolant and shielding and shit too, so I just tossed all that in with the control rods.

You said they did something non-standard though, or was it lots of them?

It made it sound like they had something like a new inner shielding structure within the pile to deal with the center/bottom issues, or did I get that wrong?

Ok, before I jump immediately to conclusions here, how do you imagine reactor construction? Right now I think you have a gross conceptual error about it that is skewing your viewpoint but I don't want to dive into an explanation if I'm just misreading the way you're presenting information again.

[Mizango]

I still stand by Physicists having the best names/acronyms.

Also, woe is me. I forgot one of my notebooks in lab on Wednesday night, and I'm probably never going to get that back. Gogo losing all of my notes for a class a few weeks before the final.

Ouch. QQ

[Eliseos]

Found it! My TA saw that I had left it in the lab, so he held on to it for me. I pretty much owe him since our final is cumulative.

[Woozie]

I still stand by Physicists having the best names/acronyms.

Also, woe is me. I forgot one of my notebooks in lab on Wednesday night, and I'm probably never going to get that back. Gogo losing all of my notes for a class a few weeks before the final.

I still stand by physicists having the worse. We always either don't bother giving something a proper name at all or give things names that make outsiders believe our theories were discovered by preschool kids.

[Max™]

http://en.wikipedia.org/wiki/File:LMFBR_schematics2.svg

The pile consisted of uranium pellets as a neutron–producing "core", separated from one another by graphite blocks to slow the neutrons. Fermi himself described the apparatus as "a crude pile of black bricks and wooden timbers." The controls consisted of cadmium-coated rods that absorbed neutrons. Withdrawing the rods would increase neutron activity in the pile, leading to a self-sustaining chain reaction. Re-inserting the rods would damp the reaction.

http://storage.lib.uchicago.edu/apf/...pf2-00502r.jpg

http://storage.lib.uchicago.edu/apf/...pf2-00501r.jpg

That is generally what I am thinking of, I know a bit about the breeder types too, with the water loop and such, though I am not nearly as up to date on the newest types as you are.

[Kryssan]

Something told me that the original pile reactor was what you were thinking about, but I wanted to be sure. That's also where the term for SCRAM came from: Safety Control Radioactive Axe Man. Because the rods in the pile were moved in and out with ropes, and if it went bad they had a guy on standby with an axe. I had the great fortune of actually meeting one of the guys on the Manhattan Project for some seminars back in college who actually worked with Fermi and the others and knew what they were working on.


Ok, so you're a few (several) decades out of date. This is a basic example of what the majority of reactors look like on the inside today:

Spoiler: show

http://blog.aethernavale.net/wp-cont...ff/reactor.jpg

This is an image of the R5 PULSTAR reactor where I was introduced to nuclear power. You can even see the example of Ĉerenkov radiation. This reactor is a research reactor, so it has a limited power output, and therefore no closure head. I don't know of any power reactor that is capable of being viewed whilst in operation; just being in the compartment while they're operating is enough to kill you within moments.


Modern reactors are built into a cage-like configuration. Since pictures are better than words, I'll use this really old college textbook of mine to show you stuff without potentially getting myself in trouble:

Spoiler: show

http://www.aethernavale.net/Media/images/reactor4.JPG

http://www.aethernavale.net/Media/images/reactor5.JPG

http://www.aethernavale.net/Media/images/reactor1.JPG

Thats the basic idea. Here's a bit more advanced:

Spoiler: show

http://www.aethernavale.net/Media/images/reactor3.JPG

http://www.aethernavale.net/Media/images/reactor8.JPG

This shows a PWR and BWR core, respectively. Almost every reactor in operation today is a thermal reactor, due to cost and construction issues. It is far better to use a fast reactor in long term costs, but it is cheaper currently to build a thermal one, and the materials didn't exist for the construction of a fast power reactor in the past. Fast reactors are most commonly known as breeder reactors, because they make their own fuel. The reactor will never run out of fuel for the life of the materials that built it, and this is the reactor most governments are scared of. The power plant you might possibly live near is not this type of reactor, I can almost guarantee it. You put in uranium, you get plutonium, which you can then make into weapons grade stuffs. The benefit of a fast reactor is how much more safe it is inherently over a thermal reactor, and the fact that you'll never refuel it.



Ok, so with all that aside, this particular prototype has some advanced designs incorporated into the material they put around the fuel. It doesn't use the pellet assembly like you see in these pictures, but the roll method, where the fuel is actual an integral part of the fuel assembly and isn't added or removed in a pellet like form. It is a part of the reactor material construction. They used different materials for this one, and they believe that might be contributing to the difference, but like I said, at this point they're not really sure.

[Max™]

Fascinating, I knew about those as well, but the pictures didn't show up, and I haven't studied them in great detail because I knew the ignorant ass public opinion hindered what is actually a perfectly safe (when properly respected) power source.

[Lhyet]

Really interesting stuff, Krys, but why are governments most scared of fast power reactors?

I remember going to a small place in England once which had a tea room overlooking a nuclear power plant which I commented as being an amazing piece of engineering, to which some of my friends commented about not wanting to live near one because of how 'unsafe' they are, using 'that place in Russia' as an example. I facepalmed.

Its disappointing how misinformed people are. I don't claim to know much of anything about these sorts of things bit at least I'm not completely ignorant.

[oldoldman]

Really interesting stuff, Krys, but why are governments most scared of fast power reactors?

Because they end up making weapons grade plutonium.

[Lhyet]

Oh right. I misread it as meaning that the normal ones made the weapons grade waste.

[Kryssan]

Fascinating, I knew about those as well, but the pictures didn't show up, and I haven't studied them in great detail because I knew the ignorant ass public opinion hindered what is actually a perfectly safe (when properly respected) power source.

My pictures aren't showing up for you?

Oh right. I misread it as meaning that the normal ones made the weapons grade waste.

Yeah, fast reactors are breeders and they make several isotopes of plutonium, its the easiest way to get the stuff. Its not weapons grade at that point, still has to be refined/enriched, but its not as if they have plutonium mines - it exists naturally only in extremely minute quantities. I'm fairly certain somewhere in this thread I posted two of the decay chains that go into explaining the 'makes its own fuel' bit... might have to dig for it though.

[Lhyet]

I see... makes sense that govenments aren't eager to get lots of those produced, then.

What sort of waste, and how much, comes from conventianal nuclear plants? I'm under the impression that it's very little, but a reply from someone in the field is far more interesting~

[Kryssan]

The 'waste' from a reactor is just the fuel rods and their assemblies. I know everyone thinks its some goo that gets put into a 55 gallon drum and dropped into the earth, but it is far more complicated than that. With good zoning axially and radially you don't achieve maximum fuel burnout, there is a lot of fuel leftover (40~60% local depletions) that does get reprocessed, though currently there are some regulations in place for using that reprocessed fuel.


As for what they do with it, for the most part if they're not reprocessing (and most of those facilities are not operating anymore, pretty much just used for longterm storage at the moment due to the nuclear power plant construction holds we've only just recently started to come out of) it gets buried in an MPC. The entire spent fuel assemblies are removed and placed in a canister, which then is placed in a storage cask, then into a transport cask, and finally a disposal cask (which it is then buried in). MPC casks come in two varieties, the 75 ton and 125 ton. They're all 18 ft tall, 8 feet in diameter, with steel walls 15" thick around the waist and 12" thick at top and bottom; contained in a double seal system.

To give you an idea of what those casks go through, they are tested to ensure integrity with 4 separate tests. Free drop (cask is dropped from 30 feet onto a flat, unyielding, horizontal surface so that it strikes its weakest point), Puncture (cask is dropped from 40 inches onto a steel bar 8 inches high and 6 inches thick at a point where damage is most likely to occur), Thermal (entire cask is kept for 30 minutes in a jet fuel fire burning at a temperature of no less than 1475F), Water immersion (cask is totally submersed 3 feet under water for a period of no less than 8 hours, and again submersed at 50 feet for a period of no less than 8 hours). They've also done other tests, such as placing them on tractor trailers and then rammed them at 60mph into a concrete barrier. These casks have never failed. Would it be bad for the environment if they did fail and some of the spent fuel got out... interesting question. The answer is really yes and no: see once again the Oklo Reactors of Africa. Nature's been burning Uranium fuel for centuries before the humans got around to it with no real damage to the environment. The silly humans are currently still trying to figure out how mother Gaia has managed to pull off this feat.

A lot of the misconception about 'waste' comes really from chemical waste. In order to maintain the integrity of the plant materials, a lot of different chemicals which are hazardous to humans and the environment are used. They become even nastier of course when they're irradiated. In addition to that from earlier times there are some radioactive materials left over from either experiments or reactor accidents that have had to be disposed of. People are quick to harp on Chernobyl, but Chernobyl-4 was the safest reactor plant in Russia before the accident. And besides, the rest of the world has plenty of past history as well - for the US that's mainly a place called Idaho Falls (btw, the USA has blown up no less than 4 reactors, 2 of which were just as spectacular as Chernobyl, merely on a smaller scale). This is the crap in the 55 gallon drums that has caused so much trouble for the community in the past. Still isn't the glowing green goo though. Whilst regulations do need to be in place to prevent this sort of thing from occurring, the people who vie against nuclear energy often either confuse these two issues or simply negate that they're separate issues, letting people's fear of the atomic bombs just fill in the blanks they leave in their lofty speaches and campaigning.


As to your waste question: Thermal reactors don't really die because they run out of fuel, they die because they become xenon precluded. Where the poisons produced by running the reactor become so great that after a shutdown of the plant it is impossible to achieve criticality again without a significant drop in temperature or simply waiting for the poison to decay away. Waiting for the decay only works up to a certain point though; basically the point at which you can't withdraw your neutron absorbers any farther to make up for the negative reactivity the poison is adding. Hence why you can drop temperature, try to use that to make up for the difference, but it can also only make up for so much and there are temperature requirements (both by procedural operations and as well due to simple laws of thermodynamics) for how cold you're allowed to operate and still be capable of producing steam to make power.


Sorry to disappoint, there are no glowing barrels of bright green goo. Although sometimes the prankster chemists have been known to show up in their yellow duck suits with some chem-light gel and test radiacs to try and freak out unsuspecting and ignorant persons.

[Eliseos]

Testing those casks has got to be one of the funnest jobs: "Let's design a new way to try to blow these things up!"

[Lhyet]

Thanks alot for that, Krys. It's really interesting to hear things explained like that by someone in the field (which is what's great about this thread. An expert in almost every field~)

So in your opinion, what's the best way forward for power these days? And what sort of problems are being faced? (I sound like a journalist >.>)

[Kryssan]

The short term (next 1-2 decades) future outlook is the Gen IV reactors, which are all ultra-safe passive control/defense reactor systems. Most of them are also fast reactors. My personal preference is for the Brayton cycle gas turbine fast reactor designs such as the GT-MHR. Brayton cycles are much more efficient than their Rankine brethren.

These reactor designs also have the benefit of being modular, which will allow them to be easily deployed as complete and integral units to other countries, instead of having to build a plant from the ground up. This would also allow expansion of power plants in segments. You build two units at a power plant, a few years later power grid needs change and you need more units. Well, they're modular, so basically you build the 'plug' and get a new unit and 'play'. Granted, this isn't true for all the designs, the liquid metal and PIUS designs aren't modular in any shape or form.

Some of these designs don't even require containments, and the fast reactor designs also don't have refueling needs. This could potentially drastically reduce their costs of construction and operations and totally eliminates the need for taking a plant down for a lengthy refuel operation every few months. Of course the public will still demand containments even if the plant doesn't require it, so the big ugly concrete buildings won't be going away - and they're damn expensive and take forever to build.



The long term development will most likely be fusion power. Clean power, no radioactive waste materials (Well, assuming DD fusion and not DT which we currently use), no control rods or other tertiary means of power control necessary, and a great deal more power than their fission counterparts. The energy released from fission is only ~2MeV per reaction, whereas a fusion event yields ~17MeV per reaction. With technology advancing, perhaps we can get the intense power needs of the tokamaks down. JET achieved breakeven power already, so ITER will almost certainly actually make power. Now that the community has gotten down with the political handwringing of where they'll build it (years wasted on this utter bs), construction has finally gotten underway. In addition to ITER, the US has also been constructing NIF (also heavily delayed in construction by completely retarded events the nuclear community had no control over), which should be going online sometime within the next few years. These plants are magnetic and interial confinement fusion designs, respectively.

MCF (magnetic confinement) is the tokamak design that most people are familiar with. The big donut that makes a plasma field in the center with huge magnets and high accelerations and then feeds fuel in tangentially from the outer walls. ICF (interial confinement) is a much newer idea, and that's the large ball that uses multiple lasers to compress fuel to a fusion event in fractions of a second pulses.

However even if one of these designs does get power production (and only one of NIFs goals is that, there is a lot of other research going on with that design), we're probably still talking 3-5 decades afterwards before the first commercial fusion plants would rollout.




Of course, whose to say what will actually happen over the next few decades? Perhaps someone will define a new power production method that is completely aside from our current trends.







And on the trend of sharing news: NNSA announces important milestone in the National Ignition Campaign. Sorry for being so late with it, this article is a month old now.

[Max™]

I meant my pictures of other types didn't show up.


I wish they'd get the Fusion shit fast-tracked already, politics holding stuff like that up is disgusting.

[Lhyet]

I wish they'd get the Fusion shit fast-tracked already, politics holding stuff like that up is disgusting.

Aye... do you ever feel like you were born a few decades too early? I know technology has come along with leaps and bounds over the last 100 years but it just feels that by the end of our lives, some really cool stuff will be beginning.

Thanks again Krys. I'm glad you touched on fusion power a little as it does seem such an interesting topic.
Shame it's still so far away really. I also bet there's far too many people out there who watched Spiderman 2 and think that anything shown about fusion is fact and it'll kill us all.