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Distributed "Nuclear Batteries" the New Infrastructure Answer?
thepacketmaster writes "The Star reports about a new power generation model using smaller distributed power generators located closer to the consumer. This saves money on power generation lines and creates an infrastructure that can be more easily expanded with smaller incremental steps, compared to bigger centralized power generation projects. The generators in line for this are green sources, but Hyperion Power Generation, NuScale, Adams Atomic Engines (and some other companies) are offering small nuclear reactors to plug into this type of infrastructure. The generator from Hyperion is about the size of a garden shed, and uses older technology that is not capable of creating nuclear warheads, and supposedly self-regulating so it won't go critical. They envision burying reactors near the consumers for 5-10 years, digging them back up and recycling them. Since they are so low maintenance and self-contained, they are calling them nuclear batteries."
why bring back the risk of meltdown/contamination. This can be achieved using solar and wind. same distributed concept. Just instead of a power cell you have a house covered with solar panels or a wind generator.
Yes this wont' work everywhere but it is viable in many high demand locations ergo Southern California.
Most reactors are built in such a way that automatically prevents them from going over critical (critical is where you want to be, as someone already pointed out). The very nature of their design, assuming something doesn't mess up, keeps them safe.
The thing is, even though reactors are built with countless safety features, something could still go wrong. That's why you have professionals constantly (or at least daily) monitoring everything. Now, if you go and produce millions of mini-reactors, put them in the backyards of regular citizens, give them nothing but automated monitoring, and leave them going for awhile, something is eventually going to go wrong. It still might work on a one-community-at-a-time basis, though. As long as appropriate precautions are taken, nuclear power is extremely effective and clean (compared to coal).
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Summary is incorrect. The "nuclear battery" (incorrect name) would have a 99.5% chance of "going critical". After all, that's what nuclear power plants do. What they mean is that the plant would have an infinitesimally small chance of achieving super-criticality. Super-criticality would be a very bad thing, but even that can be mitigated with enough cement. End result? The reactor will be as safe or safer than installing a Diesel Generator in the same location. But it will be more powerful, economical, and environmentally friendly.
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"The generator from Hyperion is about the size of a garden shed, and uses older technology that is not capable of creating nuclear warheads, and supposedly self-regulating so it won't go critical."
This statement is incorrect, a reactor has to be critical to produce power.
Criticality refers to the rate at which the chain reaction of fission is occurring. If the reactor is sub-critical, then more neutrons are absorbed then causing new fissions. In this state, the reactor power exponentially decreases to zero. When the reactor is critical, exactly 1 fission is caused on average for each neutron released, which means the reactor is at a constant power. Super-critical means the reactor is increasing in power. A special case of criticality related to nuclear bombs is called prompt-super-critical. For more info, see the wiki article.
I am not sure of the details of these designs, but I bet they use a fuel type similar to university research reactors. This fuel is a uranium-hydride mixture. The moderation for the neutrons is built into the fuel itself, but it has an extremely strong negative temperature coefficient. This means that any increase in power, and thus temperature, reduces the reactivity, which lowers the power back to the equilibrium level. It is physically impossible for the reactor to overpower.
For a neat demonstration of this effect, see this youtube video. It is the research reactor at Penn State performing a pulse. Basically, a control rod is hydraulically ejected from the core, causing the power to spike to thousands of times the rated power, but only for a microsecond. The power just as quickly goes back down to normal by itself, because of the intrinsic safety of the fuel design.
Summary is incorrect. The "nuclear battery" (incorrect name) would have a 99.5% chance of "going critical". After all, that's what nuclear power plants do. What they mean is that the plant would have an infinitesimally small chance of achieving super-criticality. Super-criticality would be a very bad thing, but even that can be mitigated with enough cement.
Even plain-ol criticality (or sub- for that matter) can be bad if it's producing too much heat for the system to take out. Say for example because whatever fluid is being used to extract said heat for power generation purposes stops flowing. Then you have a meltdown, i.e. the nuclear core melting. TFA says it's meltdown, not criticality, that is virtually impossible, so score another one for bad /. summaries.
The modern way to prevent this is with naturally self-regulating reactors (as opposed to say relying on control rods to cool the reactor down). Pebble bed reactors do it by having the uranium in the center of the pebbles so that at the right temperatures they are at the right density for a critical reaction. When they get hotter, they expand, and the reaction slows down. Natural, physical self-regulation. No machine to fail, no control logic to have a bug, it's the laws of physics saving your ass. I like that.
Here's the paragraph on how this one works: "When uranium hydride gets too hot, above 550 degrees Celsius, it will shed hydrogen atoms. The hydrogen flows out of the core and is stored in special storage trays within the reactor. As the fuel loses hydrogen atoms it begins to naturally cool. As it cools, it will retrieve the hydrogen atoms from the trays."
So again, self-regulating based on temperature, sounds pretty cool. The only thing I don't like is that it still relies on a fluid flow, so if somehow the storage trays were collapsed in a way that didn't let the hydrogen to escape, I would think that the increased pressure would mean the uranium hydride would hold onto its hydrogen at higher temperatures. But I'm anything but a chemist or nuclear physicist.
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And the followup studies found the correlation to be with the herbacides used to clear the vegitation around the power lines, and not the power lines themselves.
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You say nuclear power's problems have been mitigated by learning from our mistakes, why would the same not be true for solar?
The use of nasty chemicals in solar manufacturing is not a "mistake", it's an intentional and necessary part of the process. I won't say it's impossible not to, but that would be the discovery of a fantastic new manufacturing technique, not learning from a mistake.
Whereas Chernobyl was a mistake that we have learned from.
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