December 18, 2007

Micro and small nuclear reactors

More than 50 new small and medium size reactor designs were developed and are being considered by research groups around the world in 2006.

There are a number of small and medium nuclear reactors that are in funded development.

Toshiba has designs for a micro nuclear reactor that generates 200 kw for 40 years

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. It has dimensions of 20 feet by 6 feet.

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

This reactor is a small-scale design developed by Toshiba Corporation in cooperation with Japan's Central Research Institute of Electric Power Industry (CRIEPI) and funded by the Japan Atomic Energy Research Institute (JAERI) [unified with the Japan Atomic Energy Agency in 2005]
It is the 5 MWt, 200 kWe Rapid-L, using lithium-6 (a liquid neutron poison) as a control medium. It would have 2700 fuel pins of 40-50% enriched uranium nitride with 2600°C melting point integrated into a disposable cartridge. The reactivity control system is passive, using lithium expansion modules (LEM) which give burnup compensation, partial load operation as well as negative reactivity feedback. As the reactor temperature rises, the lithium expands into the core, displacing an inert gas. Other kinds of lithium modules, also integrated into the fuel cartridge, shut down and start up the nuclear reactor. Cooling is by molten sodium, and with the LEM control system, reactor power is proportional to primary coolant flow rate. Refuelling would be every 10 years in an inert gas environment. Operation would require no skill, due to the inherent safety design features. The whole plant would be about 6.5 meters high and 2 meters in diameter.

This information is from Hore-Lacy, Ian (Lead Author); Cutler J. Cleveland (Topic Editor). 2006. "Small nuclear power reactors." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [Published in the Encyclopedia of Earth September 4, 2006; Retrieved December 19, 2007].

A 2001 article from the New Scientist discussed the Rapid-L

The Rapid-L reactor was conceived as a powerhouse for colonies on the Moon. Unlike normal nuclear reactors, the Rapid-L has no control rods to regulate the reaction. Instead, it uses reservoirs of molten lithium-6 - an isotope that is effective at absorbing neutrons. The reservoirs are connected to a vertical tube that runs through the reactor core.

During normal operation the tube contains an inert gas. But as the temperature of the reactor rises, the liquid lithium expands, compressing the inert gas and entering the core to absorb neutrons and slow down the reaction.

The lithium acts as a liquid control rod. And unlike solid control rods, which have to be inserted mechanically, the liquid expands naturally when the core gets warm.

The Rapid-L uses the same principle to start up and close down the reaction. The reactor would be cooled by molten sodium and run at about 530 °C. Mitsuru Kambe's, head of the research team at Japan's Central Research Institute of Electrical Power Industry (CRIEPI), main concern now is to test the fail-safe system's long-term durability.

How the lithium expands to control the reaction as heat rises.

The Rapid-L is not the same as the toshiba 4s reactor which has 50 times higher generation capacity.

Toshiba 4S reactor would generate 10 MW.
The actual reactor would be located in sealed, cylindrical vault 30 m (98 ft) underground, while the building above ground would be 22 x 16 x 11 m (72 × 52.5 x 36 ft) in size. The 4S uses neutron reflector panels around the perimeter to maintain neutron density. These reflector panels replace complicated control rods, yet keep the ability to shut down the nuclear reaction in case of an emergency. Additionally, the Toshiba 4S utilizes liquid sodium as a coolant, allowing the reactor to operate 200 degrees hotter than if it used water. This means that the reactor is depressurized, as water at this temperature would run at thousands of pounds per square inch.

The reactor is expected to provide electric energy for between 5 and 13 cents/kWh in Galena, Alaska, which factors in only operating costs. On paper, it has been determined that the reactor could run for 30 years without being refueled.

More details on the Toshiba 4S

The encyclopedia of earth article is largely the same as this Australian Uranium Association article. Either the same author or perhaps the encyclopedia copied the nuclear association article.

UPDATE NOTE: The japanese reactor has conceptual similarities to the uranium hydride reactor The Japanese reactor is using uranium nitride. The first could be completed in 2012 and a good design would use 50% of the uranium which is 25 to 70 times more efficient with uranium fuel than existing reactors.

The Fuji Molten salt reactor is a type of reactor which would have almost no long lived nuclear waste. It seems to be under development by a consortium of Japan and Russian groups. It would ideally run with thorium instead of uranium. The mini version is still 8 year away from completion under assumptions of completing a proposed schedule.

870 page report on the status small nuclear reactors without onsite refueling

A 17 page policy framework for micro nuclear reactors

IAEA nuclear technology report (102 pages) from 2004

IAEA nuclear technology report (135 pages) from 2006

IAEA nuclear technology report (141 pages) from 2007


Richard Kulisz said...
This comment has been removed by the author.
bw said...

Various sources confirm the existance of the Rapid-L research program.

Uranium Information Centre Ltd
A.B.N. 30 005 503 828
GPO Box 1649, Melbourne 3001, Australia
phone (03) 8616 0440

The Rapid-L as presented to the American Nuclear Society
See page 28 of the 42 page pdf.

Startup Sequence of RAPID-L Fast Reactor for Lunar Base Power System, M.Kambe (CRIEPI-Japan), O. Sato, H. Tsunoda (Mitsubishi Research Institute Japan)

Toshiba may have a prototype in the process of being built which would be ready for 2008 or 2009.

There is no information other than the paper studies. It is not a very complicated as far as nuclear reactors go and is roughly equivalent to a potentially cheaper research reactor. There is no claim that I have seen that the reactor would be mass produced yet. The goal might be mass production but for now it looks like one off research reactors.

bw said...

I do not know for certain about any mass production plans or the status of actual hardware. I only know that are a lot of paper studies and research has been done for 6+ years. I think they probably should have a working full size research reactor. That would not take much. It does not make much sense to me to start mass production of the Rapid-L. I think there are better small reactors in the development pipeline that could help make a real difference for global energy. The fuji MSR or the hyperion simplified solid core are ones that I think look pretty good. The Fuji MSR because it leaves no long term waste and the Hyperion because it looks good to help lower the cost of oil from oil shale in Colorado.

The Rapid-L would work and look a lot better when thermoelectronics (see my articles on thermoelectric and the Freedomcar project) are more advanced by 2012-2015 and integrated into the design. Then the 5MWt could be converted to 1-2 MWe.

bw said...

On page 79 of this 210 page source there is another mention of the Rapid-L as a funded research program. the source is from 2003.

Anonymous said...

So the micro nuclear reactor.
Um, who came up with this? Seriously? And who in their right mind could think this is a good idead?

Oh it's fail safe. No it isn't. Nothing humans can make is fail safe. And if you are smart enough to make it fail, it will.

Is toshiba Alqida, because they will love this.

Micro Nuclear Reactor is a nuclear bomb with some modifacations.

I think anyone that sees this as a good idea is a threat.

The micro nuclear reacort will bring death!

bw said...


If you even glanced at the documents which were referenced you would see that many research groups (big universities and national labs) and companies in most of the developed countries of the world are working on micro and small reactors and think they are a good idea. There are several policy studies (several from MIT) that examine the issues around small reactors.

In regards to safety.
1) nuclear reactors are completely different from nuclear bombs. Why was there a twenty year gap between the development of the atomic bomb and commercial nuclear fission reactors for energy ? Because they are very different. Why after over sixty years is Iran and other countries still struggling (despite) a lot of resources to make their first atomic bomb ? Because they are complicated and difficult things to make. The N Korea test bomb only produced 1000 tons of TNT explosive equivalent (the recent culmination of a decade of research and effort. N Korea had a nuclear reactor for years). About 20 times more than the largest russian chemical bomb. Getting nanosecond timing is not a simple thing and does not happen by accident, you have to try really hard to design and build it deliberately.

2) Coal and oil and natural gas are still 85%+ of the energy used in the world. Outdoor air pollution kills 3 million people per year and indoor air pollution kills 1.5 million people per year.

12,300 people per day which is more than US Iraq war casualties + the deaths from 9/11 + the US afghanistan war casualties.

The US has about 60,000+ deaths per year from air pollution. 24,000+ deaths per year just from coal pollution.

In 23 years (by 2030), air pollution from fossil fuels will kill the equivalent of one third of the population of the USA. Equal to the population of the four largest states (California, New york, Texas and Florida).

Are you serious about saving lives? Nuclear power will save lives by being the fastest way to displace fossil fuel use and reduce air pollution. It will still take decades but it is 20 times more than wind and solar combined.

Humans have made fossil fuels into a key energy source too. What is your proposal to save those lives ?

Richard Kulisz said...

> In 23 years (by 2030), air pollution from fossil fuels will kill the equivalent of one third of the population of the USA.

Umm your arithmetic is way, way off. 60,000 x 23 is about 1.3 million. Which is about 0.3% af the population of the USA. A third of a percent doesn't sound like much though.

bw said...

My calculation is based on the world deaths from air pollution (4.5 million per year) as compared to US population levels. I know that the deaths are mostly happening in China and India. So are the deaths that happen outside the united states irrelevant ?

If we are to only discuss past deaths from a source that only happened in the USA then there have been no deaths from nuclear weapons in the USA (they all happened in Japan). If we are to discuss past deaths from nuclear reactors then they primarily happened in the Ukraine.

250,000 some deaths from air pollution each year in Europe.

1.3 million people (expected US air pollution deaths) is equal to the seventh largest city in the USA

If nuclear reactor related events at some point over the next 23 years killed everyone in San Antonio what would be the reaction of the US population ?

How about everyone in the cities of Boston and San Francisco ?

Either case is less than 1.3 million people.

So does it only matter if the deaths are from a more focused source ? A constant stream of increased cancer and heart disease deaths and coal mining deaths that result in the same death toll does not matter ?

bw said...

the city populations that I quoted for the incorporated cities and not the metro areas

bw said...

the city populations that I quoted for the incorporated cities and not the metro areas

Richard Kulisz said...

> So does it only matter if the deaths are from a more focused source ? A constant stream of increased cancer and heart disease deaths and coal mining deaths that result in the same death toll does not matter ?

Apparently. That really does tell you that human beings aren't rational, doesn't it?

Anonymous said...

So micro nuclear reacots can't turn into a nuclear bomb, no matter how well someome modifies them? I know it can be fail safe, as they said it was, since it is impossible for anything to be fail safe. What ever can go wrong will go wrong. Murphy's law.

So if this thing is safe, If you were to open it some how while it was running, there would be no radiation at all, right? Doesnt deal with atoms and such?

Anonymous said...

sorry for the typo's

Joffan said...

Put it this way, anonymous; can the local park be turned into a nuclear bomb? All the elements are there, so what's to stop someone from extracting all those lovely raw materials, processing them, fabricating precision machined components and detonating the resulting bomb? The process is no easier starting with a micro reactor.

However, I expect you are being elastic, to put it politely, with your definition of nuclear bomb. Studies of potential radioactive dispersal ("dirty") conventional bombs show that they are much less effective in hurting people than (say) biological/chemical weapons of a similar degree of difficulty. However the weapon of the terrorist is fear, whether rational or not. It's therefore your duty as an interested party to make sure that you do not spread irrational fear about the spread of radioactive material; after all many thousands of radioactive people go safely home from hospital every day.

Anonymous said...

So basically a nuclear reactor uses totally different principles then a nuclear bomb.

I guess maybe if it was that easy to make a nuclear bomb, we would have something like in "the sum of all fears" where they had a nuclear bomb in a vending machine.

But still, to say these things are fail safe is in fact a big lie, because nothing is ever fail safe.

jk said...

I know it's not possible to make a chain-reaction nuclear bomb out of reactor material, but it should be possible to get a meltdown of the reactor core. Is it so that you just need to leak the Lithium-6 for that?

Chris said...

nothing that cannot be solved with a solid moderator emergency backup, or other safety systems that would be required by most sensible governments. multiple redundant systems are as standard installed in all nuclear plants, and with those all failing there should be a bed of Borides, or other moderator granules (powder/dust, hell, even porous bricks of the stuff) to prevent the meltdown from contaminating the watertable and entering the enviroment... andeven more safety's preventing gaseous waste from entering the atmosphere.

i'm guessing your from an anti-nuclear group Anonymous, otherwise you would have looked these up prior to posting a flawed arguement.

SoundOff said...

Actually, sorry to spoil your fun, but the Micro Nuclear Reactor was just a hoax.
read the bottom.

It would have been cool, but sadly it's fake.

bw said...

I believe the hoax part is that Toshiba was going to actually manufacture the rapid-L, which I did say seemed doubtful. The Rapid-L research was real.

Cyril R. said...

I think anonymous does have a good point here. Hundreds of thousands or even millions of tiny reactors are impossible to control in terms of material diversion for dirty bombs - at least not at an affordable cost. A group with reasonable resources would not have much difficulty with succesful malignant action. Just pick one out of all the hundreds of thousands or even millions that is least well protected.

Centralized big nuclear power is great. This idea just isn't.

bw said...

In terms of incremental risk from small reactors, is it easier to get the nuclear material for a dirty bomb from these new reactors or from some other existing source ? Medical supplies, digging up radioactive material etc...

If it is a lot harder to get and use the material from any new small reactors then there is no incremental risk.

There are a million ATMs for providing money but they are rarely robbed. Because it is easier to mug someone or perform non-violent identity theft or some other scam to get the money.

ATMs have GPS tracking etc...

Smaller nuclear reactors can be made more secure than ATMs and as secure as bank vaults.
GPS tracking and other monitoring and security devices and cameras.

Plus initial siting can be on already secured grounds of existing reactors as when uprating has reached limits. I am not suggesting that small reactors get placed in malls, but in more secure locations. There are plenty of places that are already more secure.

Then the people who crack a small reactor have to do something with the material. Some nuclear material is "self-sealing" in that someone has to protect themselves from being killed as they open up the reactor.

Cyril R. said...

Suicide terrorists don't appear to care much about surviving the attack. Getting a ratiation suit is not a big deal, nor are the power tools to open the reactor.

I think security issues are manageable, but not at reasonable financial cost, especially not when you build millions of the things all over the world - that's what we have to do to nake a big impact on global energy. Why bother with it anyway if it can't supply a significant fraction of world energy needs?

Here's a newsflash for you: ATM's get robbed a lot, often not succesful but because there are so many of them around the world, the absolute number of succesful thefts is actually quite high.

A few thousand bucks stolen is a manageable and acceptable risk. Diversion of dirty bomb material isn't.

This is not a fear mongering attempt. Rather, I advise not getting ourselves into actions that become inevitably and utterly unmanageable with scale-up. Especially because centralised nukes work just fine. They don't have to be GW size, a few tens of MW might be suitable and have acceptable security overhead.

Also, material use of micro nukes would be high compared to similar capacity centralised nukes, so it's not a good idea from a resource viewpoint either.