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."

Comments

Reactors evolution

[SeanTobin]

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.

Re:SL-1 Reactor, Idaho Falls

[Remlik]

FUD ALERT! Check your facts please...Google is my friend. MOD THE PARENT DOWN!

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 .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)"

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!