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Toshiba Pushes Safe, Small Nuclear Reactor Design
core plexus writes "This article describes a proposal from a Japanese corporation that wants to thrust the Interior Alaska community of Galena into international limelight by donating a new, unconventional electricity-generating plant that would light and heat the Yukon River village pollution-free for 30 years. There's a catch, of course. It's a nuclear reactor. Not a huge, Three Mile Island-type power plant but a new generation of small nuclear reactor about the size of a big spruce tree. Designers say the technology is safe, simple and cheap enough to replace diesel-fired generators as the primary energy source for villages across rural Alaska."
This was already done in remote parts of Soviet Russia. The problem is that the devices went without supervision and were subsequently plundered by scrap metal thieves. See http://archives.tcm.ie/breakingnews/2001/05/24/sto ry13735.asp for an article about the problem.
I have to say after reading the article, the reactor design does sound very safe. Here is a quick rundown of reactor advancement...
-Big hunk of uranium in a pool of water*. Water heats but is under pressure so it can't boil. The water (contaminated and radioactive) is then piped through fresh water (in sealed pipes) from a lake or river transferring heat so the fresh water will boil and turn turbines. Neutron absorbing control rods are raised or lowered into the big hunk of uranium to control the reaction. Problems can occour with pipes corroding and releasing contaminated water*, control rods can jam, leaks in the coolant water* can cause a loss of coolant leading to an overheated reactor.
-Little pellets of uranium in a pool of water*. Same principle as above, only there are no control rods. As the pellets heat up, the expand, increasing the distance between the pelets. This is much safer because there are no control rods to jam. Loss of coolant can still be a problem, but easily solved by simply moving the pellets further apart.
-And now, this reactor.. a Big Rod of Uranium is immersed in a pool of water*. The rod of uranium is sub-critical so it can't sustain a (large) heat producing reaction on its own. A sleve made of neutron reflecting material (google for nuclear bomb neutron reflector) slowly makes its way along the BRoU over the reactors 30-year lifespan. Only the uranium surrounded by the sleve can react. If the sleve moves too fast, then the reactors lifespan is simply shorted - it will never produce more heat than can be made via the reflector. If it moves too slow, the reactor simply produces less heat. Overall a very good design. If I were to have a reactor in my backyard, I definately would choose this style.
I've gotta hand it to the toshiba people.. I wouldn't have thought of this... pretty cool.
*Note: Water may not be water. Water is often used because of its high specific heat, but many other liquids have been used as coolant. In the toshiba reactor, liquid sodium is spec'd because its non-corrosive. A big plus in a maintenance-free environment.
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There weren't any meltdowns like Chernobyl or 3 Mile Island, but if you'll recall there was a big radiation leak at a Japanese plant 4 years ago.
It's been thought of. Google for "nuclear waste subduction". The problem is that subduction is a long, slow process, punctuated by violent activities like earthquakes and volcanoes.
You could accumulate a lot of waste in a given area that was slowly being pulled under, and then an volcano blows it all back up again. Or an earthquake cracks the seals and you've got contaminated groundwater or whatever.
The problems seem solvable with careful choice of site(s). There are places where the odds of such things are quite small. Pick someplace offshore, for one thing.
In reality, you'd have a greater risk of an accident in transporting the waste there than in any major incident happening.
PHEM - party like it's 1997-2003!
Frontline, a great PBS documentary series, had a show on this, called Nuclear Reaction. Highly recommended.
Perfect logic. He's not talking about C02. He's talking about the gaseous uranium compounds released by burning coal. It's about six million tons a year if I remember right. That's six million tons of uranium, not C02.
You can tell a great deal about the character of a man by observing those who hate him.
The only commonality between the reactor you mention and the one in the article is that they are both nuclear reactors. The toshiba reactor uses a subcritical mass of uranium, so that it is inherently stable. A neutron reflector is used to cause a sustaining reaction. The reflector is sized specifically to create the temperature that the reactor is designed for (plus a margin in case you need to run a little hot) it is specifically designed not to be able to go supercritical and create a self sustaining reaction. There are no control rods because none are needed. Technology has advance alot in the last 4 decades. I wouldnt want to drive a car from 1961 either because they were also designed inherently unsafely.
Here is a Good diagram of what happened in the Chernobyl-4 reactor, in case you don't believe me.
FUD ALERT! Check your facts please...Google is my friend. MOD THE PARENT DOWN!
.01 seconds, causing the plate-type fule to melt. The molten fuel interacted with the water in the vessel, producing an explosive formation of steam that caused the water above the core to rise with such force that when it hit the lid of the pressure vessel, the vessel itself rose 3m in the air before dropping back down (Derived from DOE and US Army records)"
http://www.radiationworks.com/sl1reactor.htm
"A small, 3MW experimental BWR called SL-1 (Stationary Low-Power Plant No. 1) in Idaho was destroyed on January 3, 1961, when a control rod was removed manually."
snip
"A careful examination of the remains of the core and the vessel concluded that the control rod was manually withdrawn by about 50cm (40cm would have been enough to make the reactor critical), largely increasing the reactivity. The resulting power surge caused the reactor power to reach 20,000MW in about
1) 3MW not 200kW - Makes a difference
2) It did "melt down" - effectivly anyway
3) It did contain water (presurized or not I dunno)
4) It was caused by human error
5) It was probably a lot larger fuel block
Silly FUD's, google will always win!
Apple free since 1990!
With a gift of essentially free energy for a couple of decades, I'm sure some of 2+ million (700000 gallons at $3+ per gallon) they spend on gas (for generators) annually could be spend bringing in security personelle.
A million plus dollars buys a security force more than able to gaurd the perimeter around a complex not larger than a school building. Security is then essentially free for these people, and in fact they are still saving a lot of money per year in energy costs. Plus they are paying for a service in their community to people that will be living in their community. And those security people will spend money somewhere.
This solution may not be fesible when there are cheaper fuel alternatives, but out there it seems to make a lot of sense.
Why, o why must the sky fall when I've learned to fly?
Chernobyl was caused by _engineers_ testing removal of cores, they took all the cores out and couldn't get them back in.
What will cause more fear is idiots like you under selling the risks.
Pot. Kettle. Black.
First, by cores, you mean control rods. But you're still somewhat off track.
Second, Chernobyl was an unstable, bad design, without a containment building. It's design, RMBK 1000, was such that if things went bad, the nuclear reaction would continue, instead of shutting down.
In addition to the uranium, a nuclear reactor needs two things- a moderator (which actually promotes the fission chain reaction) and a thermal transfer mechanism, to take heat away and make electricity with it. This is beyond the control rods, which are used to shut down the plant.
In every plant in the US, water acts as both the moderator, and the heat transfer mechanism. Lose the water, and the chain reaction is unsustainable. You can't take away heat anymore, but the fission chain reaction slows down dramatically. This is what happened at Three Mile Island (TMI)- they lost the water. They melted parts of their core, but that was the extent of the meltdown. The reactor vessel did it's job and physically contained the uranium. The containment building did it's job, along with all the auxillary systems, and no appreciable radiation was released to the public. TMI proved that we can handle a disaster without endangering the public.
Back to chernobyl. The RMBK 1000 reactor used water as a heat transfer mechanism, and graphite as a moderator. So when they lost water cooling, the reaction actually increased in power, and this raised power output lead to a rapid spike in temperature and pressure, blowing the lid off the reactor core and destroying the building.
Moreover, if they attempt to sustain low power levels (20% of capacity), the system is unstable. Because the core was huge, it was possible to have pockets of reactivity that couldn't be well controlled. When the power level is low, the cooling water/heat transport flow is reduced, to keep proper operating temperatures. But because they had pockets of reactivity that could be greater than average, there could be local areas where the flow was inadequate, boiling off the water prematurely, and getting us back the increasing reactivity with water loss that I mentioned earlier. Hence, they where supposed to operate below 20% power.
As for the people, despite earlier problems at different plants, they were not aware of the aforementioned technical problems. The Soviet bueacracy prevented any useful exchanges on such subjects. This is not to excuse them from not knowing more about their plant, just to paint a picture.
The cause of this was ironically a safety experiment. When a nuke plant is shut down, it still produces a significant amount of heat that must be removed. Normally the power required to run the pumps to remove this heat comes off the grid from other power plants, but if the plant is disconnected from the grid, a diesel generator is used instead. It took them three minutes to start the diesels (as opposed to a ten second standard in the US), so the engineers thought that they could bridge this three minute gap by extracting power from the turbine while it was in the process of coasting to a stop.
In order to test this theory, they deactivated every single safety system the plant had, and brought the power levels down to 6%. I've already talked about why this was bad.
At the end of their 'safety test', they inserted the control rods successfully, and in a hurry, because they could tell they were losing control of the plant. Because of the horrible design, though, these control rods where insufficient to kill the chain reaction, and instead only displaced water, which brought the power levels up to 100 times normal. Kaboom. The 'successful' insertion of the control rods was the final event in an idiotic string of actions.
They had no understanding of the safety i
Alcohol, Tobacco and Firearms should be the name of a store, not a government agency.
General thoughts, in no specific order...
/. would have to be implemented using little peices of paper, fine point pens, and hundreds of thousands of really, really tired carrier pigeons.
A) the "dirty bomb" (a current favorite among hte fear mongering media) made out of radioactive materials is generally NOTHING like the multiple-megaton weapons that make the big fancy mushroom clouda. These are bombs that expode conventionally, and through said explosion, scatter radioactive materials around an area, creating a hot zone that will possibly kill, probably sicken, some people right near the area, but mainly just go to scare the millions of people into knee-jerk reactions though non-understanding.
B) Making a cheap and nasty little dirty bomb can be easily done by stealing the Cesium 137 out of a few hospitals (canisters of it are used in x-ray machines - i think its an xray machine). The added benefit of this is that the material is a very fine powder that can get spread widely by the wind.
One of these canisters got loose in Brazil once. Resulted in killing four and made a few people sick. THe cleanup was a tad nasty. People heard about it, and thousands of them showed up at hospitals to get checked out for possible contamination. This was after local officials told them "Look, you were in the immediate area, youre going to be fine." People still stood on line at hospitals, choking hospital resources and generally fucking up their ability to take care of those that were really hurt.
[If you get a chance, find that Dirty Bomb special NOVA did a while back. This is the ref for that cesium info above]
Stealing a fat hunk of reactor core would involve about a million times work, and unless they wannt rub the thing against a cheese grater for a while, they're left with one solid hunk of radioactive material, which is fairly easy to handle, contain, and bury somewhere.
[again, go read that NOVA site.]
C) Your average goober (read: 98% of the population) is completely unaware of that fact that we're constantly being bombarded with "background radiation" every second of every day. They're also unaware that our skin does a pretty good job of fending that low-level shit off.
D) Imagine if mass media existed at today's level in Edison's time. Getting people to accept the fact that electricity was not going to jump out of an unused outlet (or a wire) and kill you [in everyday non-dubmass use] would be next to impossible, and
E) People Die. Its something we all do, and ya can't avoid it, so stop fucking scaring yourselves into non-action. You can only hope its not going to be horrible. Generally, not being a stupidass - and keeping yourself aware of (AWARE, not SCARED) the other stupidasses around you - will go a long way in accomplishing this.
s'wut i sed.
Its impressive b/c, unlike reactors aboard SSN/SSBN/CVNs, there won't be an ocean of water around it to pull water in from, and it won't be moving fast enough to create the convection currents that allow (at least submarine) reactors to function without pumps.
Binkleyz, ET2(SS), USN, Ret.
We're talking about northern Alaska... For periods of time (which happen to be the coldest) there's little or no light...
Not to flame the prior poster, I just can't resist the chance to clarify some common misconceptions about nuclear reactors. # 1 - A critical reactor is bad; A critical reactor is a stable reactor. K effective is the ratio of neutrons in the current generation vs neutrons in the last generation. A critical reactor is when K effective is equal to one. That is the number of neutrons is not changing. ( that is the reactor power is stable) A sub critical reactor is when K effective is less than one ( The reactor power is going down.) A supercritical reactor is when K effective is greater than one( the reactor power is going up) A nuclear reactor goes through all three of the above states during normal operation. I've taken a reactor critical hundreds of times and most of my time spent operating a nuclear reactor is to maintain criticallity at a stable power. Obviously going up in power too fast is a bad thing thing. Fallacy 2 - A nuclear reactor blow up like a nuclear weapon. Nuclear reactors don't work in such a way as to support a nuclear explosion. There are several good posts about Chernobyl. This was just about a worst case accident, but is was a steam explosion.