From the NIMBY dept. A Toshiba product we can all love

[spicynacho]

Your own personal reactor. All I want to know is when can I get one?

Toshiba Builds 100x Smaller Micro Nuclear Reactor

Toshiba has developed a new class of micro size Nuclear Reactors that is designed to power individual apartment buildings or city blocks. The new reactor, which is only 20 feet by 6 feet, could change everything for small remote communities, small businesses or even a group of neighbors who are fed up with the power companies and want more control over their energy needs.

The 200 kilowatt Toshiba designed reactor is engineered to be fail-safe and totally automatic and will not overheat. Unlike traditional nuclear reactors the new micro reactor uses no control rods to initiate the reaction. The new revolutionary technology uses reservoirs of liquid lithium-6, an isotope that is effective at absorbing neutrons. The Lithium-6 reservoirs are connected to a vertical tube that fits into the reactor core. The whole whole process is self sustaining and can last for up to 40 years, producing electricity for only 5 cents per kilowatt hour, about half the cost of grid energy.

Toshiba expects to install the first reactor in Japan in 2008 and to begin marketing the new system in Europe and America in 2009.

http://www.nextenergynews.com/news1/...ar-12.17b.html

[zombie]

They have a hard enough time making HDM players that work properly and yet they're going to tackle making a nuclear reactor? Oh Lord, tell me I'm stuck in a nightmare!

[Downhere]

Originally Posted by nyg

They have a hard enough time making HDM players that work properly and yet they're going to tackle making a nuclear reactor? Oh Lord, tell me I'm stuck in a nightmare!

Mine works just fine thank you very much.

[Shadowself]

As someone who actually holds patents on systems using reactors in this class and co-developed the reactors going into them, I can say that we looked at liquid metal reactors and dropped the idea rather quickly. There are too many issues in today's environment (no pun intended).

Can a reactor of this type be viable? Yes. The issue becomes double capture on the Li-6 going to radioactive Li-8. Then what happens if this leaks? You have an activated liquid seeping into the surroundings. Early on in the reactor's life the fraction of double capture is very small, but that's also when leaks are very unlikely. Later in life when the double capture percentage becomes higher leaks are more likely.

A safer way to go is with a gas cooled reactor which has components in it that work on passive expansion of the materials. The hotter the system gets, the farther the fuel rods are pushed apart. The farther the pins are apart the lower the reaction rate. As the reaction rate goes down and the reactor cools the pins come closer together and the reaction picks up. Thus the reactor is self moderating. Sounds simple, but picking the exact materials that have very high CTE (coefficient of thermal expansion) and resistance to neutron embrittlement is a "non trivial" exercise. An additional benefit is you can pick gases that do not activate to any appreciable amount and thus a leak is not an issue.

Reactors like this are not a nuclear engineer's dream. More than one already exist.

While Toshiba's reactor is not ludicrous. With enough safeguards and robust enough containment systems they can be made safe.

However, just like HD DVD they did not do a good enough job in the design concept for my tastes.

[Banjo]

Err... a personal nuclear reactor?

I'll pass.

[theknub]

shadow, thanks for that. it makes sense.

how would the li-6 implementation be self-sustaining. i understand your gas cooling reactor example but not seeing it for liquid metal (unless in some way the idea / theory is the same).

[zombie]

Originally Posted by Downhere

Mine works just fine thank you very much.

Well good for you. I guess since yours worked fine all of them worked fine.

[Shadowself]

Originally Posted by theknub

shadow, thanks for that. it makes sense.

how would the li-6 implementation be self-sustaining. i understand your gas cooling reactor example but not seeing it for liquid metal (unless in some way the idea / theory is the same).

The Tosh system is self sustaining because the moderator (the fast neutrons from the fissions need to be slowed down) is not the Li-6 material. The Li-6 is the poisoning agent (in reactor terms) as it absorbs the neutrons to the extent of stopping the reaction when necessary (enough Li-6 in the reactor at any given moment and it absorbs enough neutrons to stop the chain reaction -- thus "poisoning" the system).

One issue is the primary coolant of the core. If this is like their other "small" reactors it is a liquid metal primary coolant. This provides both moderation and coolant. Additionally, their other "small" reactors use sodium as the primary liquid metal coolant. Sodium also activates (at a higher rate than even Li-6) so liquid metal leakage is a concern here to.

Russia launched several liquid metal cooled reactors into space (the US launched one). At least one of the Russian ones is leaking activated sodium right now.

It may be a personal bias, but I've never been 100% comfortable with liquid metal as the primary coolant. There are just too many loops and heat exchangers with too many diverse materials for my tastes.

[darinp2]

This might end up being a dumb question, but is having lots of little reactors around something terrorists would be excited about? Not sure if anything here could be used by terrorists, but if so, seems like having fewer places that need heavy security has its advantages.

--Darin

[jsteinhauer]

So you say the lithium is a moderator in these?

In my experience, metal cooled reactors are fast reactors (sodium, for instance, has a small cross section). The lithium cross section is big, an absorber, per se, but not so much a slower down, per se, like water or carbon. Maybe this is a carbon moderated reactor (like Chernobyl)?

[ikbradley]

Hopefully this will be put to good use. A lot of inaccessible areas need infrastructure and this is one way to assist.

[dialog_gvf]

From the NIMBY dept. A Toshiba product we can all love

Most NIMBY proposals aren't so literally intended to go in one's actual back yard.

[theknub]

Originally Posted by Shadowself

The Tosh system is self sustaining because the moderator (the fast neutrons from the fissions need to be slowed down) is not the Li-6 material. The Li-6 is the poisoning agent (in reactor terms) as it absorbs the neutrons to the extent of stopping the reaction when necessary (enough Li-6 in the reactor at any given moment and it absorbs enough neutrons to stop the chain reaction -- thus "poisoning" the system).

One issue is the primary coolant of the core. If this is like their other "small" reactors it is a liquid metal primary coolant. This provides both moderation and coolant. Additionally, their other "small" reactors use sodium as the primary liquid metal coolant. Sodium also activates (at a higher rate than even Li-6) so liquid metal leakage is a concern here to.

Russia launched several liquid metal cooled reactors into space (the US launched one). At least one of the Russian ones is leaking activated sodium right now.

It may be a personal bias, but I've never been 100% comfortable with liquid metal as the primary coolant. There are just too many loops and heat exchangers with too many diverse materials for my tastes.

thanks. i have to brush up my "mini-reactor" knowledge, but this is certainly interesting. been awhile since i hit the engage switch on the brain...

[gandley]

Hey, they way (sli) graphics cards and PC's are going im going to need one of these to power the dam thing soon

[Shadowself]

Originally Posted by jsteinhauer

So you say the lithium is a moderator in these?

In my experience, metal cooled reactors are fast reactors (sodium, for instance, has a small cross section). The lithium cross section is big, an absorber, per se, but not so much a slower down, per se, like water or carbon. Maybe this is a carbon moderated reactor (like Chernobyl)?

The lithium does not seem to be the moderator. Since it appears to be purely Li-6 at the start of usage, the Li-6 is a controlling agent (as I mentioned above what is typically called a poisoning agent). In this reactor it appears to take the role of cadmium rods in a stereotypical light water reactor.

You're correct, for sodium liquid metal cooled reactors the sodium is the primary but is only a secondary moderator. It has less to do with the cross section as with the nature of the collision of the neutrons with the sodium nuclei and the fraction of energy transferred. The primary moderator could be either beryllium or beryllium oxide. Either could work.

And yes, the neutron spectrum of a liquid metal cooled reactor is typically "faster" than that of a light water reactor as a smaller fraction of the neutrons causing fissions are thermalized.

I doubt very, very much that it is a carbon based (typically graphite in those reactors) moderator as they would not normally take the temperatures of a liquid metal cooled reactor. Water as a moderator is out of the question. It breaks down at the typical temperatures of a liquid metal cooled reactor.

[navychop]

Shadowself:

I must most strongly take issue with your comment. You said "Then what happens if this leaks?"
It ain't "if."

-U.S. Navy, retired
liquid sodium submarine reactor, anyone?

My nickel bet is on pebble bed reactors and helium.
Or very long range, helium-3 reactors.

[Shadowself]

Originally Posted by navychop

Shadowself:

I must most strongly take issue with your comment. You said "Then what happens if this leaks?"
It ain't "if."

-U.S. Navy, retired
liquid sodium submarine reactor, anyone?

My nickel bet is on pebble bed reactors and helium.
Or very long range, helium-3 reactors.

Yes, technically it's an if. The issue is if it leaks before the activity gets below an agreed to safe level. You can make liquid metal coolant systems that are 100% sealed with no moving parts (TEM pumps, etc.). To make them leak proof to the duration for which the reactor, activated components (including the liquid metal) and the reactor by products (including daughter products) has decayed to the point of being less radioactive than when the reactor was turned on is possible. It is extremely expensive to the point of being absolutely cost prohibitive, but it can be done -- multi-walled systems using exotics such as refractory metals and ceramics.

The point is not "when" it leaks but when it leaks is it a low enough activity. I once designed, built and worked in a lab many years ago where I (yes, me personally) was the most radioactive thing in the room. However, I would doubt if any of my friends or relatives are worried about me radioactively contaminating the environment if I cut myself and leaked blood.

Liquid metal submarine reactors? If you were a navy reactor officer you're probably aware of the various Russian reactors that were designed, tested and, in some cases, built. Enough said.

Pebble bed reactors... Ah, yes. Something I considered for a system in the 90s. Actually made the cut to the final two design concepts. Though we had considered a combination of Helium and Xenon for the coolant gas rather than just Helium as you mention -- better reaction through the turbines and compressors than Helium alone. We did not choose the pebble bed simply because the chosen alternative was a bit more mature and the NRC and DOE would not be quite as difficult.

I don't believe I'll live to see H-3 reactors. They, along with fusion reactors, have been "15-25 years away" for over 40 years. I would not be surprised if they were "25 years away" 25 years from now!