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doogle (Member Profile)

AsapSCIENCE - 3D Printing will Change Everything

visionep says...

You can print plastic or bio matter, but printing hardened materials like steel or even carbon fiber is not even on the radar yet.

Thinking that you would be able to print anything you need if you only had the materials is likely impossible.

It is like dreaming that everyone could have their own nuclear reactor in their house so that they wouldn't have to pay the electric company for power anymore.

Yes, that was a thing in the 60's when no-one understood much about nuclear energy. Just like that technology, something better and safer will likely come around that will supplant the need for that crazy idea.

James Hansen on Nuclear power and Climate Change

ghark says...

Reactors don't produce weapons grade plutonium? Then where is weapons grade plutonium made? I think you'll find that it's made in exactly the same reactors as there is no real distinction between a reactor used for power generation and weapons generation other than in name.

"Uranium ore contains only about 0.7% of the fissile isotope U235. In order to be suitable for use as a nuclear fuel for generating electricity it must be processed (by separation) to contain about 3% of U235 (this form is called Low Enriched Uranium - LEU). Weapons grade uranium has to be enriched to 90% of U235 (Highly Enriched Uranium or HEU), which can be done using the same enrichment equipment. There are about 38 working enrichment facilities in 16 countries"
http://www.cnduk.org/get-involved/parliamentary/item/579-the-links-between-nuclear-power-and-nuclear-weapons

The point is that continuation of current tech makes it a lot more economical to produce weapons tech, whether that be weapons grade plutonium or depleted uranium (DU). Reactors can cost upwards of ten billion dollars to build, why would a weapons manufacturer want to pay for one of those out of their own pocket when they can have the taxpayer's pay for nuclear power plants that can produce what they need?

"Every known route to bombs involves either nuclear power or materials and technology which are available, which exist in commerce, as a direct and essential consequence of nuclear power"
- Dr. Amory Lovins (from NEIS)

In terms of renewables:, the 'new' renewables only account for about 3% of total energy use, so if that's what he meant then he's not far off. Stats from IEA, however, state that wind has had an average growth rate of 25% over the past five years, while solar has averaged an annual growth rate of over 50% in the same period. So their impact is increasing fairly rapidly. So I'm not sure why he's so pessimistic about them when the IEA is not.

Have environmental groups specifically spoken out against the type of nuclear reactors he is talking about? Which ones?

GeeSussFreeK said:

I think that you will find reactors don't produce weapons grade plutonium, rather, they produce a grade of plutonium known as reactor grade. Weapons grade plutonium is upwards of 95% Pu239. Reactor grade plutonium is what is known as weapons usable, not weapons ready. This is because of the high contamination factor of Pu240, Pu241, and Pu242. These heavier breads of Pu have both high spontaneous fission rates (bad for your fission weapon), and considerable heat, enough so to make weapons fabrication a problem (is it bad when your closed weapons device needs ventilation to not melt itself). While these problems are addressable in advanced weapons platforms, outside of well established nuclear weapons programs, making weapons from them is very challenging.

The main trouble, however, I think is economics, and nuclear is forced to internalize many of their impacts where as other solutions, mainly fossil fuels, do not. That is a pretty key competitive disadvantage.

Also note that electricity is only a fraction of total power, total power includes many non-electrical uses, most notably motor vehicles via liquid fuels. When you look at solar in this light, it represents a sub-fraction of a percent. So 5% of annual solar electrical generation is only a small part of a larger energy picture, and picture which also needs to be weighted against the rest of the world for which solar provides very little power. This isn't an attack on solar, it is a bringing to light of how vast the gulf is to address climate issues with any one technology.

So I think you will find that he isn't off by orders of magnitude, rather, he was being pretty generous to the total amount of energy produced by solar and wind world wide, and climate issues and emissions are world issues.

Key World Energy STATISTICS IEA:

http://www.iea.org/publications/freepublications/publication/kwes.pdf

(I trust the IEA's numbers)

But I share the sentiment that we need to reduce coal and gas to address climate concerns. The fact that German emissions have risen for 2 years in a row is troubling to say the least. I consider France and Sweden to be better models, lower CO2 per capita and electrical prices in both cases compared to Germany, and both heavy nuclear users...with Sweden using a fair deal more hydro power than France. Nuclear and hydro are the proven heavy lifters in the area of CO2 reductions, which is why I think his criticism of environmental groups in addressing climate issues is justified as they generally oppose both.

CLIMATE CHANGE AND NUCLEAR POWER 2012 IAEA:

http://www.iaea.org/OurWork/ST/NE/Pess/assets/12-44581_ccnp2012_web.pdf

US Army's Top Secret "Camp Century" Underground Arctic City

siftbot says...

Tags for this video have been changed from 'secret, camp century, military, arctic' to 'secret, camp century, military, arctic, nuclear reactor' - edited by calvados

Israel attack on Syria again.

bcglorf says...

This is as outrageous and unjustified as Israel's last attack in September 2007 in Syria. You remember, the one Syria denied even happened for several months. The one the UN IAEA inspectors confirmed in 2011 almost certainly did destroy a nuclear reactor under construction there.

Israel considered it within it's rights to stop North Korean weaponry being delivered to Syria then, and today, stopping Iranian weapons reaching Hezbollah.

Can you honestly say Israel has no legitimate right to concern over Syrian arms shipments to Hezbollah? Do you honestly believe that Israel should be expected to simply take on faith and trust that Assad, or elements in his military, won't ship chemical weapons to Hezbollah?

Kofi said:

Israel is completely within its rights to attack another sovereign nation because....

*Insert any other nation* is completely within its rights to attack another sovereign nation because...

How to Photograph the Earth from Space

charliem says...

They stay that way in all proceeding pictures? Or just the long exposure ones?

I would assume the latter, cosmic rays slow down and lose quite a bit of their energy by the time they hit us down here on the ground....exposure to one in space though will certainly kill a pixel for good.

Saturation of light sensitive photodiodes (ill call them PD's henceforth) (essentially what the CCD is PACKED with) causes damage over time. You can just over-saturate the PD, to the point of damage (usually around 3dBm above its rated saturation point), and it will bounce back ok. The sensitivity of the pixel will be harmed dependant on the time and the level above saturation it was exposed at.

You can see a similar phenomenon in video footage of nuclear reactor survey footage from drones, or....stupid people that are way too close....where the reactors have a nasty event.

deathcow said:

Charlie I get those on my CCD on Earth. The trick is that I expose my camera for usually 10 minutes at a time (under the stars.) Even so, only 1 out of 50 gets a good solid cosmic ray hit.

NASA: We Found Water On Mercury and How it was Found

GeeSussFreeK says...

O by the by, neutrons decay in free-space, in other words, free neutrons are radioactive. With a decay time of less than 15 mins, it means 2 things: slow neutrons will be less detectable at distance because they decay, you still need to be relatively close to the source of neutrons to detect them regardless of speed. Neutrons are also the only form of radiation that will make things radioactive, meaning if you get to close and the bombardment is to intense , you can cause damage to your equipment via internal radiation of beta and gamma rays.

This is also why they use water in nuclear reactors, hydrogen, and in particular deuterium (hydrogen with a neutron) slow neutrons better than anything. Water is mostly hydrogen by mole, so it is a very good moderator, both light water (regular water) and heavy water (deuterium water).

What is happening in this particular case is known as nuclear spallation. When a high energy proton hits something like carbon or nitrogen, it will at times knock a proton or neutron loose. Those neutrons are moving at relativistic speeds in most cases, so on the flip side, when those neutrons bounce their way out back to space, if there is water in the way they get slowed way down...enough that they decay before they reach the detector.

This is the same exact effect that allows for carbon dating, sometimes, the high energy neutrons that come out via spallation will in turn knock out a proton from a nitrogen atom, it then becomes mildly radioactive carbon. This happens at a relatively predictable rate, and since the decay of carbon 14 is also predictable, dating is possible.

Science rant over

Seconds From Disaster : Meltdown at Chernobyl

radx says...

@GeeSussFreeK

I tried to stay way from issues specific to the use of nuclear technology for a reason. There's very little in your reply that I can respond to, simply for a lack of expertise. So bear with me if I once again attempt to generalize and abstract some points. And I'll try to keep it shorter this time.

You mentioned how construction times and costs are pushed up by the constant evolution of compliance codes. A problem not exclusive to the construction of power plants, but maybe more pronounced in these cases. No matter.

What buggers me, however, is what you can currently observe in real time at the EPR construction sites in Olkiluoto and Flamanville.
For instance, the former is reported to have more than 4000 workers from over 60 nations, involving more than 1500 sub-contractors. It's basically the Tower of Babylon, and the quality of work might be similar as well. Workers say, they were ordered to just pour concrete over inadequate weld seams to get things done in time, just to name an example. They are three years over plan as of now, and it'll be at least 2-3 more before completion.
And Flamanville... here's some of what the French Nuclear Safety Authority had to say about the construction site: "concrete supports look like Swiss cheese", "walls with gaping holes", "brittle spots without a trace of cement".

Again, this is not exclusive to the construction of NPPs. Almost every large scale construction site in Europe these days looks like this, except for whatever the Swiss are doing: kudos to them, wonderful work indeed. But if they mess up the construction of a train station, they don't run a risk of ruining the ground water and irradiating what little living space we have in Europe as it is.

Then you explain the advantages of small scale, modular reactors. Again, no argument from my side on the feasability of this, I have to take your word on it. But looking at how the Russians dispose of their old nuclear reactors (bottom of the Barents Sea) and how Germany disposes of its nuclear waste (dropped down a hole), I don't fancy the idea of having even more reactors around.

As for prices, I have to raise my hands in surrender once again. Not my area of expertise, my knowledge is limited to whatever analysis hits the mainstream press every now and then. Here's my take on it, regarding just the German market: the development, construction, tax exemption, insurance exemption, fuel transport and waste disposal of the nuclear industry was paid for primarly by taxes. Conservative government estimates were in the neighbourhood of €300B since the sixties, in addition to the costs of waste disposal and plant deconstruction that the companies can't pay for. And that's if nothing happens to any of the plants, no flood, no fire, nothing.

That's not cheap. E.ON and RWE dropped out of the bid on construction permits for new NPPs in GB, simply because it's not profitable. RWE CEO Terium mentioned ~100€/MWh as the minimum base price to make new NPPs profitable, 75.80€/MWh for gas-powered plants. Right now, the base (peak) price is at 46€/MWh (54€/MWh) in Germany. France generates ~75% of its power through NPPs, while Germany is getting plastered with highly subsidized wind turbines and solar panels, yet the market price for energy is lower in Germany.

Yes, the conditions are vastly different in the US, and yes, the next generation of NPPs might be significantly cheaper and safer to construct and run. I'm all for research in these areas. But on the field of commercial energy generation, nuclear energy just doesn't seem to cut it right now.

So let's hop over to safety/dangers. Again, priorities might differ significantly and I can only argue from a central European perspective. As cold-hearted as it may sound, the number of direct casualties is not the issue. Toxicity and radiation is, as far as I'm concerned. All our NPPs are built on rivers and the entire country is rather densely populated. A crashing plane might kill 500 people, but there will be no long term damage, particularly not to the water table. The picture of an experimental waste storage site is disturbing enough as it is, and it wasn't even "by accident" that some of these chambers are now flooded by ground water.

Apologies if I ripped anything out of context. I tried to avoid the technicalities as best as I could in a desperate attempt not to make a fool of myself. Again.

And sorry for not linking any sources in many cases. Most of it was taken from German/Swiss/Austrian/French articles.

Seconds From Disaster : Meltdown at Chernobyl

GeeSussFreeK says...

@radx No problem on the short comment, I do the exact same thing

I find your question hard to address directly because it is a series of things I find kind of complexly contradictory. IE, market forces causing undesirable things, and the lack of market forces because of centralization causing undesirable things. Not to say you are believing in contradictions, but rather it is a complex set of issues that have to be addressed, In that, I was thinking all day how to address these, and decided on an a round about way, talking about neither, but rather the history and evolution as to why it is viewed the way you see it, and if those things are necessarily bad. This might be a bit long in the tooth, and I apologize up front for that.

Firstly, reactors are the second invention of nuclear. While a reactor type creation were the first demonstration of fission by humans (turns out there are natural fission reactors: Oklo in Gabon, Africa ), the first objective was, of course, weapons. Most of the early tech that was researched was aimed at "how to make a bomb, and fast". As a result, after the war was all said and done, those pieces of technology could most quickly be transitioned to reactor tech, even if more qualified pieces of technology were better suited. As a result, nearly all of Americas 104 (or so) reactors are based on light water pressure vessels, the result of mostly Admiral Rickover's decision to use them in the nuclear navy. This technological lock in made the big players bigger in the nuclear field, as they didn't have to do any heavy lifting on R&D, just sell lucrative fuel contracts.

This had some very toxic effects on the overall development of reactor technology. As a result of this lock-in, the NRC is predisposed to only approving technology the resembles 50 year old reactor technology. Most of the fleet is very old, and all might as well be called Rickover Reactors. Reactors which use solid fuel rods, control rods, water under pressure, ect, are approved; even though there are some other very good candidates for reactor R&D and deployment, it simply is beyond the NRCs desire to make those kinds of changes. These barriers to entry can't be understated, only the very rich could ever afford to attempt to approve a new reactor technology, like mutli-billionaire, and still might not get approved it it smells funny (thorium, what the hell is thorium!)! The result is current reactors use mostly the same innards but have larger requirements. Those requirements also change without notice and they are required to comply with more hast than any industry. So if you built a reactor to code, and the wire mesh standards changed mid construction, you have to comply, so tear down the wall and start over unless you can figure out some way to comply. This has had a multiplication effect on costs and construction times. So many times, complications can arise not because it was "over engineered", but that they have had to go super ad-hawk to make it all work due to changes mid construction. Frankly, it is pretty amazing what they have done with reactor technology to stretch it out this long. Even with the setbacks you mention, these rube goldbergian devices still manage to compete with coal in terms of its cost per Kwh, and blow away things like solar and wind on the carbon free front.

As to reactor size LWRs had to be big in the day because of various reasons, mostly licencing. Currently, there are no real ways to do small reactors because all licencing and regulatory framework assumes it is a 1GW power station. All the huge fees and regulatory framework established by these well engineered at the time, but now ancient marvels. So you need an evacuation plan that is X miles wide ( I think it is 10), even if your reactor is fractionally as large. In other words, there is nothing technically keeping reactors large. I actually would like to see them go more modular, self regulating, and at the point of need. This would simplify transmission greatly and build in a redundancy into the system. It would also potentially open up a huge market to a variety of different small, modular reactors. Currently, though, this is a pipe dream...but a dream well worth having and pushing for.

Also, reactors in the west are pretty safe, if you look at deaths per KWH, even figuring in the worst estimates of Chernobyl, nuclear is one of the best (Chernobyl isn't a western reactor). Even so, safety ratcheting in nuclear safety happens all the time, driving costs and complexity on very old systems up and up with only nominal gains. For instance, there are no computer control systems in a reactor. Each and every gauge is a specific type that is mandated by NRC edict or similar ones abroad (usually very archaic) . This creates a potential for counterfeiter parts and other actions considered foul by many. These edicts do little for safety, most safety comes from proper reactor design, and skillful operation of the plant managers. With plants so expensive, and general costs of power still very competitive, Managers would never want to damage the money output of nuclear reactors. They would very much like to make plant operations a combination of safe, smooth, and affordable. When one of those edges out the other, it tends to find abuses in the real world. If something gets to needlessly costly, managers start looking around for alternatives. Like the DHS, much of nuclear safety is nuclear safety theater...so to a certain extent, some of the abuses don't account for any real significant increase in risk. This isn't always the case, but it has to be evaluated case by case, and for the layperson, this isn't usually something that will be done.

This combination of unwillingness to invest in new reactor technology, higher demands from reactors in general, and a single minded focus on safety, (several NRC chairmen have been decidedly anti-nuclear, that is like having the internet czar hate broadband) have stilted true growth in nuclear technology. For instance, cars are not 100% safe. It is likely you will know someone that will die in a car wreak in the course of your life. This, however, doesn't cause cars to escalate that drastically in safety features or costs to implement features to drop the death rate to 0. Even though in the US, 10s of thousands die each year in cars, you will not see well meaning people call for arresting foam injection or titanium platted unobtanium body frames, mainly because safety isn't the only point of a car. A car, or a plane, or anything really, has a complicated set of benefits and defects that we have to make hard choices on...choices that don't necessarily have a correct answer. There is a benefit curve where excessive costs don't actually improve safety that much more. If everyone in the USA had to spend 10K more on a car for form injection systems that saved 100 lives in the course of a year, is that worth it? I don't have an answer there as a matter of fact, only opinion. And as the same matter of opinion on reactors, most of their cost, complication, and centralization have to do with the special way in which we treat reactors, not the technology itself. If there was a better regulatory framework, you would see (as we kind of are slowly in the industry despite these things) cheaper, easier to fabricate reactors which are safer by default. Designs that start on a fresh sheet of paper, with the latest and greatest in computer modeling (most current reactors were designed before computer simulations on the internals or externals was even a thing) and materials science. I am routing for the molten salt, thorium reactors, but there are a bunch of other generation4 reactors that are just begging to be built.

Right now, getting the NRC to approve a new reactor design takes millions of dollars, ensuring the big boy will stay around for awhile longer yet. And the regularly framework also ensures whatever reactor gets built, it is big, and that it will use solid fuel, and water coolant, and specific dials and gauges...ect. It would be like the FCC saying the exact innards of what a cellphone should be, it would be kind of maddening to cellphone manufacturers..and you most likely wouldn't have an iPhone in the way we have it today. NRC needs to change for any of the problems you mentioned to be resolved. That is a big obstacle, I am not going to lie, it is unlikely to change anytime soon. But I think the promise of carbon free energy with reliable base-load abilities can't be ignored in this green minded future we want to create.

Any rate, thanks for your feedback, hopefully, that wasn't overkill

Seconds From Disaster : Meltdown at Chernobyl

radx says...

Heading back to school for nuclear engineering myself in the next year or so, hopefully to make reactors completely self regulating.

Since no source is mentioned, I assume this to be your comment and therefore applaud and envy you. Most of my passion for a couple of things died somewhere along the way.

Questions, comments or concerns on nuclear or energy in this thread are always welcome (and encouraged!)

Meaningful questions would require a level of knowledge I do not possess, so I'll stick to the layman's reaction: a comment.

Two issues that are not exclusive to the use of nuclear technology make me a strong opponent of nuclear energy in general, aside from technology-specific problems. It's the involvement of people in every stage of the process and centralisation.

Anything run by private entities has to generate a profit. Therefore corners will be cut, regulations will be circumvented. Mistakes will be made, design flaws covered up. The cheapest material will be used by the least paid worker, supervised by a guy on his second job who just wants to go home to his family.

Case in point would be the reactors in Germany, one of the most stricly regulated and controlled markets in the world. Absurd levels of negligence and coverup after coverup have become public over the years, and that's before cost cutting measures became en vogue.

Or take the EPR Olkiluoto 3 in Finland. The reports on the construction process would be hysterically funny if it wasn't a bloody nuclear reactor they're working on.

Google some pictures of "Schachtanlage Asse" to see the reality of "due dilligence" in these matters. If people are involved, bean counters and politicians will run the show, fuck-ups and bad calls are inevitable.

Even if engineers call the shots, they'll overengineer it, they'll make it incompatible with real life conditions. We've seen it time and time again. I could tell you stories about the ICE train, for instance, that'll make your head spin. Incidently, the same company is also involved in the construction of nuclear power plants.

As for centralisation: if energy generation is focused on large scale power plants, it creates monopolies/oligopolies. If a handful corporations, or regionally even just a single corporation, controls the market for something as fundamental as energy, it turns all concepts of a market into a farce. Look at France where EDF basically owns every single plant. Or Germany, where Vattenfall, E.ON, RWE and EnBW control the grid, control the power plants, control the market, control the price, control the politics. It's madness.

Edit: Blimey! This was supposed to be a short comment, yet it turned into another incoherent rant. Sorry.

Perpetual Motion Machine

GeeSussFreeK says...

>> ^Kalle:

One serious question that bothers me is.. why isnt it possible to use gravity as an energy source?
Would such a machine be a perpetual motion machine?


Gravity is REALLY weak. Like 36 orders of magnitude less than the electromagnetic force. 36 orders of magnitude is massive...larger the the total number of stars in the known universe. For instance, a fridge magnet is defeating the ENTIRE gravitational force of the earth AND the sun. Gravity makes for a great way to bind the macro-universe together, but it is shit as an energy source.

Also, gravity has only one polarity...and it doesn't turn off. So for the EM force, we have 2 poles that can be switched around via electrical current to make lots of different energy related things. But for gravity, you just have one ground state, and once you are there you need to input energy to get away from that ground state...no way around that. However, what has been done and is done in certain areas is to have a closed system where you apply energy at certain time and store that energy for later. The example most commonly used is in dams, where the will pump a large volume of water back up stream (potential energy) and store it (a gravity battery if you will) and release it as a later time when demand is high. This is always a loss based way to make energy; your going to spend more pumping it back up (heat loss and other losses including evaporation) than you will when you get it back...so it is just a way to cause demand shifting towards other hours with additional entropy.

You have 4 fundamental forces to draw energy from; and 3 of those are the only practical ones. Strong (nuclear) force, the EM force, and the gravitational force (the weak force is actually the force that powers the earths core, but isn't useful to use in power generation for a similar reason gravity isn't).

The EM force is what we use in internal combustion engines and electrical motors. Chemical reactions are rearrangements of the electron structures of molecules, which makes gasoline engines possible via liquid to gas expansion pressures. Generators deal with EM fields, polarity and current which is what drives thermal reactors like coal or can drive a car with a motor via conversation of stored electrical energy(just a backwards generator). Nuclear reactors deal with the strong (nuclear) force, and combine that with kinetic/thermodynamic forces of same flavor as coal and other thermal plants.

Even gravity isn't perpetual, the orbits of ALL celestial bodies are unstable. Gravity is thought and reasonably well satisfied to travel in waves. These waves cause turbulence in what would seem calm orbits, slowly breaking them down over time...drawing them closer and closer together. Eventually, all orbits will cause ejection or collision.


As to what energy is best, I personally believe in the power of the strong force, as does the sun . When you are talking about the 4 forces and their ability to make energy for us, the strong force is 6 orders of magnitude greater than other chemical reactions we can make. The EM force is not to much weaker than the strong force, but the practical application of chemical reactions limits us to the electron cloud, making fuels for chemical reactions less energetic by a million to a billion times vs strong force fuels. Now, only fission has been shown to work for energy production currently, but I doubt that will be true forever. If you want LOTS of energy without much waste, you want strong force energy, period. That and the weak force are the 2 prime movers of sustained life on this planet. While the chemistry is what is hard at work DOING life, the strong and weak force provide the energy to sustain that chemistry. Without it, there are no winds, there is no heat in the sky nor from the core, no EM shield from that core. Just a cold, lifeless hunk of metals and gases floating in the weak gravitational force.

Sorry for the rant, energy is my most favorite current subject



(edit, corrected some typos and bad grammar)

ReverendTed (Member Profile)

GeeSussFreeK says...

Safe nuclear refers to many different new gen4 reactor units that rely on passive safety instead of engineered safety. The real difference comes with a slight bit of understanding of how nuclear tech works now, and why that isn't optimal.

Let us first consider this, even with current nuclear technology, the amount of people that have died as a direct and indirect result of nuclear is very low per unit energy produced. The only rival is big hydro, even wind and solar have a great deal of risk compared to nuclear as we do it and have done it for years. The main difference is when a nuclear plant fails, everyone hears about it...but when a oil pipeline explodes and kills dozens, or solar panel installers fall off a roof or get electrocuted and dies...it just isn't as interesting.

Pound per pound nuclear is already statistically very safe, but that isn't really what we are talking about, we are talking about what makes them more unsafe compared to new nuclear techs. Well, that has to do with how normal nukes work. So, firstly, normal reactor tech uses solid fuel rods. It isn't a "metal" either, it is uranium dioxide, has the same physical characteristics as ceramic pots you buy in a store. When the fuel fissions, the uranium is transmuted into other, lighter, elements some of which are gases. Over time, these non-fissile elements damage the fuel rod to the point where it can no longer sustain fission and need to be replaced. At this point, they have only burned about 4% of the uranium content, but they are all "used up". So while there are some highly radioactive fission products contained in the fuel rods, the vast majority is just normal uranium, and that isn't very radioactive (you could eat it and not really suffer any radiation effects, now chemical toxicity is a different matter). The vast majority of nuclear waste, as a result of this way of burning uranium, generates huge volumes of waste products that aren't really waste products, just normal uranium.

But this isn't what makes light water reactors unsafe compared to other designs. It is all about the water. Normal reactors use water to both cool the core, extract the heat, and moderate the neutrons to sustain the fission reaction. Water boils at 100c which is far to low a temperature to run a thermal reactor on, you need much higher temps to get power. As a result, nuclear reactors use highly pressurized water to keep it liquid. The pressure is an amazingly high 2200psi or so! This is where the real problem comes in. If pressure is lost catastrophically, the chance to release radioactivity into the environment increases. This is further complicated by the lack of water then cooling the core. Without water, the fission chain reaction that generates the main source of heat in the reactor shuts down, however, the radioactive fission products contained in the fuel rods are very unstable and generate lots of heat. So much heat over time, they end up causing the rods to melt if they aren't supplied with water. This is the "melt down" you always hear about. If you start then spraying water on them after they melt down, it caries away some of those highly radioactive fission products with the steam. This is what happened in Chernobyl, there was also a human element that overdid all their safety equipment, but that just goes to show you the worst case.

The same thing didn't happen in Fukushima. What happened in Fukushima is that coolant was lost to the core and they started to melt down. The tubes which contain the uranium are made from zirconium. At high temps, water and zirconium react to form hydrogen gas. Now modern reactor buildings are designed to trap gases, usually steam, in the event of a reactor breach. In the case of hydrogen, that gas builds up till a spark of some kind happens and causes an explosion. These are the explosions that occurred at Fukushima. Both of the major failures and dangers of current reactors deal with the high pressure water; but water isn't needed to make a reactor run, just this type of reactor.

The fact that reactors have radioactive materials in them isn't really unsafe itself. What is unsafe is reactor designs that create a pressure to push that radioactivity into other areas. A electroplating plant, for example, uses concentrated acids along with high voltage electricity in their fabrication processes. It "sounds" dangerous, and it is in a certain sense, but it is a manageable danger that will most likely only have very localized effects in the event of a catastrophic event. This is due mainly to the fact that there are no forces driving those toxic chemical elements into the surrounding areas...they are just acid baths. The same goes for nuclear materials, they aren't more or less dangerus than gasoline (gas go boom!), if handled properly.

I think one of the best reactor designs in terms of both safety and efficiency are the molten salt reactors. They don't use water as a coolant, and as a result operate at normal preasures. The fuel and coolant is a liquid lithium, fluoride, and beryllium salt instead of water, and the initial fuel is thorium instead of uranium. Since it is a liquid instead of a solid, you can do all sorts of neat things with it, most notably, in case of an emergency, you can just dump all the fuel into a storage tank that is passively cooled then pump it back to the reactor once the issue is resolved. It is a safety feature that doesn't require much engineering, you are just using the ever constant force of gravity. This is what is known as passive safety, it isn't something you have to do, it is something that happens automatically. So in many cases, what they designed is a freeze plug that is being cooled. If that fails for any reason, and you desire a shutdown, the freeze plug melts and the entire contents of the reactor are drained into the tanks and fission stops (fission needs a certain geometry to happen).

So while the reactor will still be as dangerous as any other industrial machine would be...like a blast furnace, it wouldn't pose any threat to the surrounding area. This is boosted by the fact that even if you lost containment AND you had a ruptured emergency storage tank, these liquid salts solidify at temps below 400c, so while they are liquid in the reactor, they quickly solidify outside of it. And another great benefit is they are remarkably stable. Air and water don't really leach anything from them, fluoride and lithium are just so happy binding with things, they don't let go!

The fuel burn up is also really great. You burn up 90% of what you put in, and if you try hard, you can burn up to 99%. So, comparing them to "clean coal" doesn't really give new reactor tech its fair shake. The tech we use was actually sort of denounced by the person who made them, Alvin Weinberg, and he advocated the molten salt reactor instead. I could babble on about this for ages, but I think Kirk Sorensen explains that better than I could...hell most likely the bulk of what I said is said better by him



http://www.youtube.com/watch?v=N2vzotsvvkw

But the real question is why. Why use nuclear and not solar, for instance?

http://en.wikipedia.org/wiki/Energy_density

This is the answer. The power of the atom is a MILLION times more dense that fossil fuels...a million! It is a number that is beyond what we can normal grasp as people. Right now, current reactors harness less that 1% of that power because of their reactor design and fuel choice.

And unfortunately, renewables just cost to darn much for how much energy they contribute. In that, they also use WAY more resources to make per unit energy produced. So wind, for example, uses 10x more steal per unit energy contributed than other technologies. It is because renewables is more like energy farming.

http://videosift.com/video/TEDxWarwick-Physics-Constrain-Sustainable-Energy-Options


This is a really great video on that maths behind what makes renewables less than attractive for many countries. But to rap it up, finally, the real benefit is that cheap, clean power is what helps makes nations great. There is an inexorable link with access to energy and financial well being. Poor nations burn coal to try and bridge that gap, but that has a huge health toll. Renewables are way to costly for them per unit energy, they really need other answers. New nuclear could be just that, because it can be made nearly completely safe, very cheap to operate, and easier to manufacture (this means very cheap compared to today's reactors as they are basically huge pressure vessels). If you watch a couple of videos from Kirk and have more questions or problems, let me know, as you can see, I love talking about this stuff Sorry if I gabbed your ear off, but this is the stuff I am going back to school for because I do believe it will change the world. It is the closest thing to free energy we are going to get in the next 20 years.

In reply to this comment by ReverendTed:
Just stumbled onto your profile page and noticed an exchange you had with dag a few months back.
What constitutes "safe nuclear"? Is that a specific type or category of nuclear power?
Without context (which I'm sure I could obtain elsewise with a simple Google search, but I'd rather just ask), it sounds like "clean coal".

Bill Gates on Nuclear and renewables

Yogi says...

>> ^GeeSussFreeK:

>> ^Yogi:
>> ^GeeSussFreeK:
At any rate, don't take my word for it, there is lots of data out there to look over.


No there isn't because we haven't had enough reactors for a long period of time to get a large enough date sample. The only reason Chernoble wasn't as bad as it could be here was because it wasn't placed in Downtown LA. Look I get it, it's cleaner than coal...it's not safe, don't try to make it sound safe. Japan proved it's not safe...lets put a few in tornado alley and see what happens...or maybe some on the San Andreas Fault.
Whatever data that's out there it's not a big enough sample size...it's like asking 100 people to represent that nations opinions. No Nuclear Power until we at least kill half the population.

I don't think you realize how much power nuclear provides. At over 61,032 MW, and nearly 450 plants, there is a ton of data on how safe and clean they are. Japan proved that even in a case of a nuclear meltdown from a Tsunami that killed over 10k people, 3 explosions, and flooding...and only ONE person died (from a heart attack), that nuclear reactors are one of the great engineering examples in the world today. Not only that, but that reactor is over 40 years old, a gen 1 reactor. Many modern reactors not longer use regular water, or water at all as a coolant, so are much much safer. But even then, more people have died falling off roof tops installing solar panels than even in Fukushima. I think you have made up your mind already, but I challenge you to examine your opinion and see if it hasn't been formed by fear factor media hype instead of facts and evidence. I know I had similar to your opinion not to long ago. The evidence is pretty clear, nuclear power has the best track record of any power source in the history of man in terms of production and safety. There are still some bad reactors out there, but take that into consideration, there are 1000 different ways to do nuclear energy, just because one or 2 reactors designs are bad doesn't make the whole lot bad. That is like saying since Ford made a bad car once, not only are all Fords bad, but all cars, it is a reaction that is based more in emotion than evidence, and the evidence is that pound for pound, fission is the safest and cleanest energy around, even in spite of running on 50 year old tech ( you should see the stuff we have now). Think of how different cars and planes have gotten in 50 years, how much safer, how much more reliable!?


I'll be honest...I don't give a shit I just want you to shut up.

Bill Gates on Nuclear and renewables

GeeSussFreeK says...

>> ^Yogi:

>> ^GeeSussFreeK:
At any rate, don't take my word for it, there is lots of data out there to look over.


No there isn't because we haven't had enough reactors for a long period of time to get a large enough date sample. The only reason Chernoble wasn't as bad as it could be here was because it wasn't placed in Downtown LA. Look I get it, it's cleaner than coal...it's not safe, don't try to make it sound safe. Japan proved it's not safe...lets put a few in tornado alley and see what happens...or maybe some on the San Andreas Fault.
Whatever data that's out there it's not a big enough sample size...it's like asking 100 people to represent that nations opinions. No Nuclear Power until we at least kill half the population.


I don't think you realize how much power nuclear provides. At over 61,032 MW, and nearly 450 plants, there is a ton of data on how safe and clean they are. Japan proved that even in a case of a nuclear meltdown from a Tsunami that killed over 10k people, 3 explosions, and flooding...and only ONE person died (from a heart attack), that nuclear reactors are one of the great engineering examples in the world today. Not only that, but that reactor is over 40 years old, a gen 1 reactor. Many modern reactors not longer use regular water, or water at all as a coolant, so are much much safer. But even then, more people have died falling off roof tops installing solar panels than even in Fukushima. I think you have made up your mind already, but I challenge you to examine your opinion and see if it hasn't been formed by fear factor media hype instead of facts and evidence. I know I had similar to your opinion not to long ago. The evidence is pretty clear, nuclear power has the best track record of any power source in the history of man in terms of production and safety. There are still some bad reactors out there, but take that into consideration, there are 1000 different ways to do nuclear energy, just because one or 2 reactors designs are bad doesn't make the whole lot bad. That is like saying since Ford made a bad car once, not only are all Fords bad, but all cars, it is a reaction that is based more in emotion than evidence, and the evidence is that pound for pound, fission is the safest and cleanest energy around, even in spite of running on 50 year old tech ( you should see the stuff we have now). Think of how different cars and planes have gotten in 50 years, how much safer, how much more reliable!?

Bill Gates on Nuclear and renewables

GeeSussFreeK says...

What about reactors that can't melt down? What about Ford Pintos that exploded when you hit them from the rear, that isn't a story of why all cars are dangerous, only Ford Pintos. What about a plane lands on a city and kills thousands, or the super dome and 10s of thousands? What if what if what if. 50 million people is a little showing of being irrationality scared. Even in the worst designed reactor incident in history, it wasn't as bad as that. If you looked closely, as well, the chart shows that nuclear has historically been safer that solar and wind (and hydro if you include the Banqiao Dam incident).

With that said, I do wish to see old light water reactor technology phased out and new, walk away safe reactors phased in. Engineered safety is less preferred than intrinsic safety that many of the new reactors have. Also, lets not forget, most of the navy is nuclear...meaning they feel safe enough to be in war time situations with current reactors, so engineered safety can indeed be very safe.

I have irrational fears as well, I hate to fly even though I know statistically it is safer than driving. I would suggest that your fear of nuclear is of the same nature. The only way you can kill millions of people with current or future nuclear technology is with bombs, not reactors. The only way reactors can "explode" is from a steam explosion or a hydrogen explosion...so about as bad as a fuel plant exploding, most likely several orders of magnitude less. IE, reactors explode chemically, not via fission, making no more or less dangerous that that other kinds of tech, with the exception of the fission byproducts. The good thing about most of the new nuclear tech is the fuel burn up rates are very very high, meaning there is less fuel involved in most cases.

At any rate, don't take my word for it, there is lots of data out there to look over. For my part, I think nuclear is the cleanest, safest bet for energy needs. I submit that nuclear is only scary because of it was first developed as a fearsome weapon. But the even more fearsome weapon are thermonuclear weapons, which are actually fusion/fission hybrid bombs. I would imagine for whatever reason you aren't super scared of fusion, and would wager that if thermonuclear bombs were called fusion bombs, the world at large would have a different mindset towards it...irrationally.

But I leave you with the facts, nuclear has been the leading sources of clean power which has also caused the least amount of deaths than other technologies. There are many factors in that, including massively engineered safety that continues to improve, as well as highly trained crews that watch over them. Coal miners die all the time, pipelines explode, oil platforms explode, people fall off roofs, or fall off wind farm towers, or get electrocuted...but none of these deaths cause the downfall of those technologies. Nuclear still has more drama in our minds, so plays out much differently when something goes wrong, which isn't very often ( 6 fatal occurrences since 1961) .

>> ^Yogi:

>> ^GeeSussFreeK:
http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html


I'm sorry are you comparing death rates between Coal and Nuclear Reactors? What if there's a meltdown or a terrorist attack and suddenly there's 50,000,000 people dead? It only takes one reactor outside of LA to do catastrophic damage you cannot compare the two NOW when we don't have a Fuckton of Reactors near population centers.
Comparing the two at this point in time is just ridiculous, the numbers are so skewed it's not even funny.



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