GE To Turn World's Biggest Civilian Plutonium Stockpile Into Electricity 241
First time accepted submitter ambermichelle writes "GE Hitachi Nuclear Energy has proposed to the U.K. government to build an advanced nuclear reactor that would consume the country's stockpile of radioactive plutonium. The technology called PRISM, or Power Reactor Innovative Small Module, would use the plutonium to generate low-carbon electricity. The U.K. has the world's largest civilian stockpile of plutonium. The size of the stockpile is 87 tons and growing. Nuclear reactors unlock energy by splitting atoms of the material stored in fuel rods. This process is called fission. For fission to be effective, neutrons – the nuclear particles that do the splitting and keep the reaction going – must maintain the right speed. Conventional reactors use water to cool and slow down neutrons, keeping fission effective. But water-cooled reactors leave some 95 percent of the fuel's potential energy untapped."
Re:Water-cooled reactors are only 5% efficient? (Score:2, Informative)
Save solar, wind and various methods of deriving hydroelectric power, all electric power generators boil down to the downright caveman primitive method of heating water into steam to drive turbines. No one has yet figured out anything better.
Re:Water-cooled reactors are only 5% efficient? (Score:5, Informative)
I am amazed that conventional water-cooled reactors are only 5% efficient. It sure casts the seemingly low efficiency factors of other alternative fuels(such as the cheapest solar panels) into a different light.
But you are talking about 5% of the energy from a fuel with an energy density which is about 1,000,000 times the energy density of coal
Re:Water-cooled reactors are only 5% efficient? (Score:3, Informative)
It's not 5% efficiency. Of the thermal energy they produce, in fact, more of it can be used than coal, since nuclear reactors can operate at higher temperatures than coal furnaces. However, if someone came up with a coal fuel cell, perhaps it could be even more efficient, since it wouldn't lose energy to thermalization. Muscles are not heat engines, they are like 95% efficient.
Only 5% of the nuclei that can be fissioned are. In a different reactor, more of the fuel could be fissioned; with current reactors, unburnt fuel is left piling up. Until, apparently, there's enough unburnt fuel to make that different reactor viable.
This is great news.
Re:Can you please explain what's an atom again? (Score:4, Informative)
kumquat:unit of kum
Re:Water-cooled reactors are only 5% efficient? (Score:5, Informative)
It's not that it's not that efficient, it's that it really doesn't need to be. The energy from fission is mostly captured (although you are dumping a lot of heat), but crucially it leaves high energy products behind in the fuel. It's what makes the spent fuel so hazardous to deal with, which is why it's crazy to suggest burying it in the ground!
Why bury something that has so much juicy energy still in it that we can extract with current technology? The answer is political, of course.
The other factor to consider is the sheer magnitude of the energy we're talking about here. E = mc^2 is not just a handy soundbite.
Re:radioactive plutonium (Score:5, Informative)
no. but the usual Pu-239 isn't very radioactive, just emits alphas slowly with a very long half life of 24,200 years. That radiation can't even penetrate your skin or go through a piece of paper. Pu-240 is artificial, usually decays by alpha but sometimes spontaneously fissions, it too has long half-life of more than 6500 years. Then there is Pu-238, emits huge amounts of alphas with its short half-life of 88 years, it's used in RTG batteries and also radioisotope heater units. A kilogram of the stuff gives off 500 watts.
Re:New power source? (Score:3, Informative)
All power sources are problematic. Energy has a way of making environments uninhabitable to humans... When you start storing large amounts of energy in small spaces things get more dangerous.
But don't let that fool you. Coal seam fires for instance: http://en.wikipedia.org/wiki/Centralia,_Pennsylvania can make an area uninhabitable for decades, centuries...
Hydro destroys ecosystems down stream; to some humans, this can destroy their livelihood. And when one damn fails it'll kill hundreds to thousands in a few minutes...
Nuclear is just scary because its a black box that "normal people" don't understand. When a dam fails, those thousand people die quickly in an easy to comprehend way. When a criticality event happens and people drop to a gamma burst, well, lets just say a wall of water is a lot less scary than nothing at all... And, in the end, all energy storage mediums have risks: to the environment, to people, and to economies...
Re:New power source? (Score:5, Informative)
You can't get supercriticality/runaway fiisson like happened at Chernobyl
Fast reactors are somewhat notorious for being trickier to control than (well-designed) thermal ones. It's very difficult to avoid a positive void coefficient, and fairly small changes in the fuel geometry can lead to large changes in reactivity. There was a meltdown in an early FBR caused by thermal expansion causing the fuel to bow inwards, increasing the reactivity. Phenix in France also had unexplained loss of reactivity incidents.
Re:New power source? (Score:4, Informative)
I would hate to see a scaled up Solar Thermal power plant. The largest one that I know of is the SEGS plant in California. As I remember it has a peak power output of ~350MW. But if your talking about 24/7 operation that drops to a small 75MW of output.
To get that 75MW of base load capacity, they have to use 6.5KM^2(I had to look that up ^^) of land. If this technology was scaled up to the size of a nuclear plant that has a base load capacity of 1GW you would be talking about using(some people would say destroying) 90KM^2 land.
Actually, looking at the Invanpah plant which is currently under construction, it's a 392MW(Peak Power) plant that is going to be using ~16KM^2 of land. So the newer plant is even worse on land usage... While it's technically possible to build large solar thermal plants, I don't think your going to find the land to do it. Invanpah was scaled down from initial plans because of land use issues...
I am not so sure about the cost difference either. Invanpah is a 2.2 billion dollar project. When you compute $ per KW of capacity, your looking at about $5,600 per KW. It's hard to find accurate Nuclear plant numbers since so none have been built in the US in 30 years. Looking online I found two numbers on $per/KW a pro nuclear site quoted ~$2000-2500/KW and a anti-nuclear site said ~5000-6000/KW. I am not sure which to believe but even if it's the high number, it lines up with Invanpah cost almost exactly. But the problem is that this is comparing the Peak Power $/KW price of Invanpah vs Nuclear. I looked all over the place and I couldn't the planned capacity factor... but if Invanpah can only generate a base load of ~100-130MW then the cost of Invanpah would be 3-4 times that of the "High" figure vs Nuclear.
Honestly after looking at these numbers I am shocked at just how bad Solar Thermal power really is for baseload generation costs. I didn't think it was good but I never would have thought it was this bad.
Re:New power source? (Score:3, Informative)
No event in any nuclear reactor that has ever happened can happen in one.
WTF. Where did you get this from? Twenty seconds of research shows the Monju Nuclear Power incident [wikipedia.org] which was a fire caused by a liquid sodium leak. That can obviously repeat in any sodium cooled reactor.
Re:Not quite like that (Score:4, Informative)
That's half true. There's a number of properties that make sodium very attractive as a coolant:
-It is much less corrosive to many steel alloys than is water. Some alloys don't corrode at all.
-It allows for a high power density
-High thermal conductivity
-The reactor need not be pressurised
-Low neutron capture cross section
-Modest melting point
-It only forms short lived radio-isotopes when irradiated
-High operating temperature ( as compared to water )
From a safety perspective a properly designed sodium cooled reactor is very unlikely to suffer a LOCA due to the low pressure, natural circulation allows for sufficient heat transport even during a total loss of power, the higher thermal conductivity enables fast thermal feedbacks and the higher thermal efficiency ( due to higher temperatures ) means somewhat less decay heat has to be transported away.
It can completely fission the actinides you feed it, and the waste it produces decay to safe levels within 300 years, as opposed to 100.000 for the original wastes. Plutonium that has been recycled through it would also be almost useless for nuclear weapons since the isotopic composition after 1 or two passes is even worse than reactor grade plutonium. The reason it only consumes a small portion of nuclear waste is because it needs almost 100 times less fuel than a conventional reactor ( thanks to a positive breeding gain ) , which conversely means that if you consider all the waste we have, there's enough fuel for a thousand years or so.
Now there are alternative breeder designs to sodium coolant. Lead, molten salt, helium or supercritical water could all work. They all have their respective advantages and disadvantages.