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Posted on 02/11/2012 7:59:11 AM PST by Wonder Warthog
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Though most of today's nuclear reactors are cooled by water, we've long known that there are alternatives; in fact, the world's first nuclear-powered electricity in 1951 came from a reactor cooled by sodium. Reactors cooled by liquid metals such as sodium or lead have a unique set of abilities that may again make them significant players in the nuclear industry.
At the U.S. Department of Energy's (DOE) Argonne National Laboratory, a team led by senior nuclear engineer James Sienicki has designed a new small reactor cooled by lead—the Sustainable Proliferation-resistance Enhanced Refined Secure Transportable Autonomous Reactor, or SUPERSTAR for short.
Small modular reactors, or SMRs, are small-scale nuclear plants that are designed to be factory-manufactured and shipped as modules to be assembled at a site. They can be designed to operate without refueling for 15 to 30 years. The concept offers promising answers to many questions about nuclear power—including proliferation, waste, safety, and start-up costs.
SUPERSTAR is an example of a so-called "fast reactor," a type fundamentally different from the light-water reactors common today. Light-water reactors use water both as a coolant and as a moderator to slow down neutrons created in the fuel as it fissions. Instead, fast reactors use materials that don't slow down neutrons—often a liquid metal, such as sodium or lead.
Like all new generations of reactors, SUPERSTAR has "passive" safety systems—backup safety measures that kick in automatically, without human intervention, in case of accidents. For example, all reactors have control rods incorporating substances that absorb neutrons and stop nuclear chain reactions. SUPERSTAR's rods can be suspended above the reactor core held in place by electricity. If the plant loses power, the control rods will automatically drop into the core and stop the reaction.
In addition, SUPERSTAR's lead coolant is circulated around the core by a process called natural circulation. While existing plants use electrically-driven pumps to keep the water moving, SUPERSTAR exploits a law of physics to move the coolant.
"In any closed loop, with heat at the bottom and cooling on top, a flow will develop, with the heated stream rising to the top and cooled stream going down," explained Anton Moisseytsev, an Argonne nuclear engineer also working on the reactor design. "SUPERSTAR design takes advantage of this feature its lead coolant is circulated solely by natural circulation, with no pumps needed. And of course, having no pumps means no pump failures."
This means that if the plant loses power, as happened at the Fukushima Daiichi plant in Japan, the reactor does not need electricity to cool the core after shutdown.
Although the SMR concept has been around for decades, the idea has gained greater traction in recent years. Both President Obama and U.S. Department of Energy Secretary Steven Chu have extolled the virtues of SMRs; Secretary Chu said their development could give American manufacturers a "key competitive edge."
For example, the smaller size of SMRs gives them greater flexibility. "A small grid in a developing nation or a rural area may not need the 1,000 megawatts that a full-size reactor produces," Sienicki said. "In addition, SUPERSTAR can adjust its own power output according to demand from the grid."
Sienicki and his colleagues designed the reactor so that it could be shipped, disassembled, on a train. SMRs have been pinpointed for use in developing nations or outlying areas; these plants could be dropped off at a site and easily installed.
Because the plant runs for decades on a single installment of fuel—and operators need never directly interact with the fuel, which is sealed in the core—SMRs also address proliferation concerns. Reducing access to the fuel lowers all the risks associated with creating and changing fuel, such as uranium enrichment technology.
Finally, SMRs could also offer cost benefits. After major cost overruns on plants in the 1980s, investors have been wary of financing new nuclear plants. Small modular reactors reduce the risk in investing in new plants; the start-up cost would be less than those for full-size reactors. In addition, the parts for the reactors could be manufactured in assembly lines at factories, further diminishing the cost
"The most effective "slowing down" material is one that has a high percentage of hydrogen."
So a large quantity of diesel fuel or a big pile of coal would work pretty well? How about boron?
Just trying to figure out where to stand if a neutron bomb goes off in the vicinity. ;)
SMUD also went all-in on "efficiency" and "end use management". They learned that hard way that conservation only works if you have something to conserve in the first place.
Yes, SMUD did the same thing at their main office off of hwy 50. You can see them from the freeway. I’ve never seen any numbers on how much they produce or how much efficiency is lost as they get older. I think the rule of thumb is a solar cell loses 10% of its efficiency each year.
That’s a good reason to use the boiling oil (or whatever they use) down in Eastern, Southern California. The reflectors track the sun and direct their light onto a boiler, it’s this hot fluid that drives the turbines. I’ve never seen a comparison of its efficiency VS a solar cell. The plant is ugly but who cares? It’s in the middle of the desert. But, I could be convinced to put one next to Jerry Brown’s house.
More recently, the Japanese tech firm Toshiba is developing these distributed nuclear generation units, designed so that they can be lit up, buried, and ignored for the next fifty years or so.
Fukushima Reactor 1 was designed by GE, built by TEPCO, and began service in 1971. I don’t think that qualifies as “modern,” but opinions may vary.
This experiment in using nuclear power to boil water started in 1942 only for creating and exacting the by-product plutonium, for bomb making. It was billed later as unlimited source of electric power generation as a cover when other countries wanted to join the ‘Mutual Assured Destruction’ (MAD) nuclear race.
Once you start a nuclear reaction, you can’t stop it. The fission may end but decay of parent material into daughter material continues indefinitely (in our time frame).
If you expose a recent spent fuel assembly to air, heat from decaying material reactions will cause it to catch on fire in 15 minutes or less releasing its radioactive contamination. Takes five to ten years for the fuel assembly’s decay reactions to diminish enough to even think about exposing it to air and still you need circulating air to carry off residual heating.
This is why nuclear fuel sits in pools next to the reactors as it must be transferred (moved) and stored underwater at all times, for years. Plus, constant cooling (removal of heat) from the storage pool water or the water will heat up beginning to steam and boil away.
BWR are only about 30% efficient as the quest for more efficient designs are elusive when it comes to overall costs. Water and other moderators slow down the bouncing neutrons to cause or give a better chance of them striking the nuclear fuel pellets inside the fuel rods that makeup fuel assemblies. The more strikes the better as they cause more heating due to the reactions (fission). Without a moderator, neutrons move to fast to be effective.
Heat exchangers are vulnerable points as high temperatures meet cold temperatures during heat transfer usually through relatively thin metal tubes. (Not so recently, San Onofe i.e. Original heat exchanges were meant to last the life of the plant’s operation, were recently replaced due to wear and the replacements are failing after only a few years.)
The more efficient a design, the less daughter by-products would remain, meaning any reactions would give off their heat at once leaving little or no nuclear byproducts...like a perpetual motion machine, ain’t going to happen.
More like natural gas.
Most often used materials are simply things like paraffin wax and various C-H polymers (polyethylene,polypropylene). Cheap, easy to obtain, easy to fabricate and many other advantages. A layer of that covered by some lead (to soak up the resulting X and gamma radiation), and you're good.
Boron you don't want around at all.....it soaks up neutrons like a sponge and will stop your chain reaction dead in it's tracks. For that reason it is used on control rods, and as the "control of last resort".....flooding the reactor with water loaded with sodium borate.
Maybe he is, maybe he isn’t. Either way, the future of Nuclear is LENR.
I hope you’re right.
And that is still light years away from being a usable weapons charge... not only in material processing, but there are many other factors involved...
"Almost" pure pellets are completely useless in a bomb and it would take untold amounts of resources to convert them. Few nations have the money and expertise to do it, let alone an individual or small group.
Hmmm. I had one out a few months ago for about an hour and a half, it had just been running in the core for a few months a couple of days earlier. No overheating, no fire. The exposure rate was a few R/hr at the distance we were inspecting it, but otherwise it was fine.
Those solar thermal plants are monstrosities in terms of land use, and while they are always quoted at their installed capacity, the best you’re going to do is about 40% capacity factor, and even that is somewhat variable. Modern grid control just isn’t set up to deal with significant generating assets coming on and dropping off in unpredictable and capricious manners. Believe me, it is a power dispatcher’s worst nightmare, trying to juggle variable sources in a time of high demand.
Must not have been a spent fuel rod huh?
You can handle an new and unused fuel rod safely with your bare hands if you like.
I think you over estimate what it would take to revert Uranium Oxide ceramic pellets back to Uranium metal.
It should be no problem for a bright high school chemistry student with some stainless steel drums and commonly available industrial chemicals.
If this was irradiated fuel that would be another story.
And the point of your link is precisely what??
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