Posts Tagged‘reactor’

Not Your Typical Fusion Reactor: The Stellarator.

When you read news about fusion it’s likely to be about a tokamak type reactor. These large doughnut shaped devices have dominated fusion research for the past 3 decades mostly because of their relative ease of construction when compared to other designs. That’s not to say they’re not without their drawbacks, as the much delayed ITER project can attest to, however we owe much of the recent progress in this field to the tokamak design. However there are other contenders that, if they manage to perform at similar levels to tokamaks, could take over as the default design for future fusion reactors. One such design is called the stellarator and its latest incarnation could be the first reactor to achieve the dream: steady state fusion.

Wendelstein 7-X

Compared to a tokamak, which has an uniform shape, the stellarator’s containment vessel appears buckled and twisted. This is because of the fundamental design difference between the two reactor types. You see in order to contain the hot plasma, which reaches temperatures of 100 million degrees celsius, fusion reactors need to contain it with a magnetic field. Typically there are two types of fields, one that provides the pinch or compressing effect (poloidal field) and another field to keep the plasma from wobbling about and hitting the containment vessel (toroidal field). In a tokamak the poloidal field comes from within the plasma itself by running a large current through the plasma and the poloidal field from the large magnets that run the length of the vessel. A stellarator however provides both the toroidal and poloidal fields externally requiring no plasma current but necessitating a wild magnet and vessel design (pictured above). Those requirements are what have hindered stellarator design for some time however with the advent of computer aided design and construction they’re starting to become feasible.

The Wendelstein 7-X, the successor to the 7-AS, is a stellarator that’s been a long time in the making, originally scheduled to have been fully constructed by 2006. However due to the complexity and precision required of the stellarator design, which was only completed with the aid of supercomputer simulations, construction only completed last year. The device itself is a marvel of modern engineering with the vast majority of the construction being completed by robots, totalling some 1.1 million hours. The last year has seen it pass several critical validation tests, including containment vessel pressure tests and magnetic field verification. Where it really gets interesting though is where their future plans lead; to steady state power generation.

The initial experiment will be focused on short duration plasmas with the current microwave generators able to produce 10MW in 10 second bursts or 1MW for 50 seconds. This is dubbed Operational Phase 1 and will serve to validate the stellarator’s design and operating parameters. Then, after the completion of some additional construction work to include a water cooling transfer system, Operational Phase 2 will begin which will allow the microwave system to operate in a true steady state configuration, up to 30 minutes. Should Wendelstein 7-X be able to accomplish this it will be a tremendous leap forward for fusion research and could very well pave the way for the first generation of commercial reactors based on this design.

Of course we’re still a long way away from reaching that goal but this, coupled with the work being done at ITER, means that we’re far closer than we ever were to achieving the fusion dream. It might still be another 20 years away, as it always is, but never before have we had so many reactor designs in play at the scales we have today. We’ll soon have two (hopefully) validated designs done at scale that can achieve steady state plasma operations. Then it simply becomes a matter of economics and engineering, problems that are far easier to overcome. No matter how you look at it the clean, near limitless energy future we’ve long dream of is fast approaching us and that should give us all great hope for the future.

An Armchair Scientist’s Mission To Europa.

If there’s any place in our solar system that we’d want to start seriously looking for life it’d be Europa. The dust covered snowball of a moon likely contains a vast subsurface ocean, one that is kept liquid by the giant gravitational forces of its host planet Jupiter. This makes Europa a great candidate for life as we know it as once we find water it’s inevitable that we find life shortly thereafter. The challenge with Europa though is getting to that subsurface ocean to study it as it could be covered in several kilometers of water ice, not something you can simply puncture through. Whilst there are numerous people more qualified than me on this subject, many of them actually working in the aerospace industry, with NASA asking for ideas for a potential mission to Europa I figured I’d throw my 2 cents in.

Europa

So the total budget for the potential mission is a cool $1 billion and whilst that sounds like a lot of money projects that I’d consider simpler than my idea (like say Curiosity which was $2.5 billion) but I think there’s potential to build a platform that could fuel further missions. With that in mind this initial mission is likely only to be a scouting mission, one that will give us the most detailed picture of Europa possible so that the follow up mission can choose the perfect site to land on and commence the search for life in its vast underground ocean. My proposal then is to develop a compact nuclear reactor (not a RTG) to power a scouting craft laden with instruments to analyse the gravitic field and surface of Europa. This craft will be able to find the point at which the surface ice is the thinnest and identify potential landing sites for the second generation craft: a cryobot that will punch through to the ocean below.

Putting a nuclear reactor into space might sound like the plan of a crazed sci-fi nerd but there’s actually been dozens of small prototype reactors launched into space with all of them proving to be safe and reliable. The power capabilities of such a reactor are far beyond that of what a small satellite would usually require however attempting to melt through kilometers of ice will require power of that scale. Thus it would make sense to fund research into developing the power supply first and then validating it on the scouting craft. Then, once that mission is successful, the reactor can be scaled to the appropriate dimensions for the cryobot mission and even used in other deep space programs.

Having such a generous amount of power available also opens up the opportunity to using instruments on the scouting craft which would not be feasible, typically. Things like high-power antennas (which could function as a relay for the follow up mission), radar imagers or bigger and better versions of other instruments. My knowledge on the power requirements of various instruments is limited but I know that even the most advanced RTGs, like the one in Curiosity, produce a measly 125W. Being able to draw on several kilowatts, an order of magnitude more power, seems like it would open up many opportunities that just weren’t possible previously.

I’m probably vastly underestimating how much it would cost to develop such technology, especially in today’s nuclear hostile political environment, but if we’re serious about actually digging under Europa’s surface I don’t see what our other options would be. Melting through giant sheets of ice is no small task and one that has requirements that far surpass anything we have currently. Using that $1 billion mission to set ourselves up for future exploration seems like the best bet especially considering how many other applications a safe, small nuclear reactor would have.

It’s Pronounced “Nuclear”.

I can’t help but feel that there are some technologies out there that just get hit with a bad name once and are then driven underground because of it. Cold fusion was a great example of this since the scientists who were experimenting with it first didn’t follow proper scientific method but now any serious research into this area is immediately hit with disdain, even though there are some results that require further investigation. This becomes all the more painful when something that is proven to work gets the same sort of reaction. I am of course referring to nuclear power, or fission reactors.

Now what’s the first thing that comes to mind when someone mentions nuclear power to you? Is it a clean source of energy or do you get images of Chernobyl, Three Mile Island and nuclear weaponry? It seems the majority of the world is stuck in the latter mindset, only remembering the horrors that nuclear power brings to the world. The truth of the matter is that not only is nuclear power completely safe, it’s also a lot more friendly to the environment than any other fossil fuel based means of generating power.

The first round of questions I usually get concerning nuclear power is “Doesn’t it produce highly radioactive and toxic waste?” and the answer is yes, it does. However, per kilowatt of power produced a coal plant will release around 100 times more radiation into the surrounding environment. Additionally most of the waste produced by a nuclear plant that comes out radioactive means it’s still usable as fuel for a reactor, it just requires some more handling. This is done using breeder reactors which I do admit carry with them a small risk of proliferation. This can be easily offset by modifying the breeder to render the weapons grade stuff unusable, keeping the risk well within acceptable levels.

One country that has been listening to people like me is France, producing well over 85% of their electricity from nuclear sources. They’ve also only had 2 incidents arising from their use of nuclear power and breeding reactors, giving them an amazing track record for safety. You would think that if there was such a high risk in using nuclear power that the French would have had a multitude of accidents, but they haven’t. Clearly nuclear power is a lot safer than what the general public believes.

To give you an idea of just how bad public opinion is here’s a graph showing the number of nuclear reactors over time:

794px-Nuclear_Power_HistoryImage used under the The Creative Commons Attribution-NonCommercial-ShareAlike License Version 2.5 from Global Warming Art.

The Three Mile Island incident was a pretty minor affair technically and nuclear power continued to grow afterwards. However Chernobyl tarnished the world’s view of nuclear power and it hasn’t really recovered since. The fact of the matter is the reactor responsible for that disaster was known at the time to be an unsafe design and modern reactors are quite capable of shutting themselves down before such a disaster can occur.

It’s the old saying of once bitten, twice shy. The world suffered through a major accident with nuclear power and from then on anyone peddling it as the solution to the world’s energy problems has to work past lobbyists, politicians and the society at large. It’s hard to convince everyone that the risks are far lower than what they used to be, and for some reason the mythical idea of a clean coal power plant seems like a better idea than proven nuclear technologies. Australia as a nation, who’s uranium reserves are the largest in the world, is well positioned to take advantage of this technology. With so much unarable land available there’s no reason for us not to set up large reactors away from major population centres, keeping the “risks” to the population even smaller still.

So hopefully the next time you talk to someone about nuclear power you won’t see the green glowing boogey man that seems so ingrained in everyone’s heads. One day nuclear will be one of our few options left, and it is my hope that we begin working on implementing a nuclear based power infrastructure before its our last option.