Forgot your password?
typodupeerror

Comment: Re:What else can they do? (Score 1) 155

by sillybilly (#47781945) Attached to: New NRC Rule Supports Indefinite Storage of Nuclear Waste

Also, just in case it's not clear, the necessity for multiple stages of different working fluids - which might seem like an overly complex mess guaranteed to fail - well the necessity for it is that you cannot use ultahighpressure steam boilers going all the way to 1500C, you might be able to push it to 500C (when atmospheric pressure boiling point of water is 100C), but the pressure you're dealing with are so humongous, that there are not structural materials able to hold your boiler together. Switching to another top working fluid, such as potassium is discussed in the literature, allows working at the high temperature with that working fluid under moderate pressure, able to use existing structural boiler materials. Then using the bottoming heat, the heat given off when, say the potassium-steam goes from vapor to liquid, at 1 atmosphere on the potassium side, at the boiling point of potassium (which can be lowered much below the atmospheric 774C if using a vacuum condenser, like a lot of 1960's steam locomotives started using), so suppose you're not running at one atmosphere on the potassium side, but 0.01 atmosphere, and the boiling temperature might be 500C, so on the other side of the heat exchanger you're able to raise steam at say 2000 psi pressure and 500C (i'm too lazy to look up the actual number right now, the principle is what matters), a nice high pressure that you can expand efficiently compared if you only raised steam at 200psi and 150C(whatever the number is), where the Carnot cycle efficiency is very low. Also in absence of the topping cycle, raising steam at 500C to begin with, and not using potassium vapor at say 2000 psi at 1100C, expanding to vaccuum of 0.01psi at 500C, you are discarding a lot of usable energy, sort of like you have a dam, of 100 yards height, and you let the water freely drop, as a waterfall to 25 yards, where you collect it, then you run a turbine on 25yards head pressure, as opposed to the full 100 yards pressure you could have in the first place. Sadi Carnot derived his efficiency of heat engines principles discussing how the heat fluid, that permeates the material, called caloric, falls from heights of high temperature to lower temperature, even if this day we abandoned the concept of caloric because it can be freely generated in a calorimeter by simple stirring about a spindle with flaps on it, friction generates heat from mechanical motion, therefore heat IS mechanical motion at the molecular level, in a different state of entropy, and not a conserved fluid or principle, as the existence of caloric would make you believe.

And by the way a good site for amusing overengineered compound locomotives to read is at
http://www.aqpl43.dsl.pipex.co...

So everything I said here may in the end not be justified, compared to the status quo, when nuclear fuel is so cheap, that wasting 99% of it in a LWR and dealing with the relatively small amount of waste (compared to, say CO2 emissions from coal power plants or cars) is the best economy. I just wrote all this stuff up to keep people informed, especially the researchers, as there is constant push in this field, such as the Russian lead-bismuth accidents, so just because the major power companies like simple to deal with LWR's, it does not mean that's the ultimate end of story, and in theory, higher efficiency is achievable through better technology, but you have to carefully watch the added complexity cost that brings all kinds of failure and safety issues with it. But as there are present places use liquid sodium, knowing the practicality of dealing with chemicals, I cannot anything but wholeheartedly recommend gallium, which is so mild, if cooled to human body temperature, it looks like liquid mercury, and you can almost sweep it around with your bare palms. But it's not fully researched, and the gotchas, if there are any, you'd only find out along the way of trying.

Comment: Re:What else can they do? (Score 1) 155

by sillybilly (#47781805) Attached to: New NRC Rule Supports Indefinite Storage of Nuclear Waste

If there were a way to coat ruthenium or niobium in magnesium oxide and fluoride, that would be immune to zn attack for reduction, or gallium attack for metal-alloy dissolution. Calcium alloying might be better, as calcium boils off only at 1484, and if there is some minimal controlled amount of oxygen present in the reactor phase, even as gallium oxide, it may continuously form a surface coating of calcium oxide on attacking a calcium/niobium alloy plus metallic gallium. However at such high temperatures the diffusion coefficients are so high, that you cannot say calcium-niobium alloy, because the calcium simply goes everywhere all at once, inside the gallium metal and the structural material, and there is no surface coating formed, which requires a diffusion limited process, and a meeting point, controlled reaction zone, at the surface. Barium and strontium are even worse on temperature than calcium, and this trio forms the top most-oxygen hogging elements in the world. However you don't have to go all that extreme, and something with a lower diffusion coefficient but better oxygen affinity than zinc vapor, such as zirconium oxide, or even niobium oxide and molybdenum oxide on the surface of fairly noble ruthenium, might be a good (liquid-gallium-metal-alloying-) corrosion protecting coating, that continuously forms if the diffusion coefficient of zirconium metal inside niobium is low, and it does not dissolve into the liquid gallium, but it's fast enough to react to surface oxygen coatings. Yttria stabilized zirconia is a oxygen sensor material, a ceramic best able to withstand temperature fluctuations, and yttrium metal also has low cross section, with a 1523C mp. Same arguments exactly go for fluoride in all cases. It's probably not possible to form a ceramic material, and say glue it to the reactor vessel surface, and expect it to stay there and not to crack, but there are such things as room temperature glass coated reactors, and if one can find a glassy oxide coating amongst these ca-zr-y-ga oxides/fluorides (or even isotopically pure borates and silicates, or, better, germanates and stannates, anything that's a good thermal stress crack resistant surface adhering glass at the proper temperatures), and control the oxygen content in the reactor, you might be able to create just such a glassy corrosion protective surface coating against liquid gallium alloying dissolution attack on a metal.

Comment: Re:What else can they do? (Score 1) 155

by sillybilly (#47781727) Attached to: New NRC Rule Supports Indefinite Storage of Nuclear Waste

Chromium is also an interesting structural material candidate, as it does have a decent cross section, not as good as niobium, or even iron, but it melts higher than iron, and carbon content in the niobium, molybdenum, ruthenium set of metals might drop the melting point and high temperature properties just like carbon does in case of cast iron, but if chromium has a high affinity for carbon, a Widia (tungsten carbide/cobalt matrix) -like cermet could be made from say ruthenium/chromium carbide. Or even ruthenium/molybdenum carbide. I don't know if this area has been fully researched and how niobium, for instance, forms cermets with chromium carbide or it itself hogs the carbon and has a eutectic, cast-iron-like. With oxides things might be simpler, except that zinc probably reduces ruthenium oxide and fluoride and completely destroys it, and magnesium or sodium are even worse in this reducing agent aspect. Silicon and boron might have certain isotopes responsible for the high cross section, while the other ones might be awesome, So isotopically pure silicide and boride, also high temperature materials, besides carbides, might lie as an option on the table when protecting ruthenium from alloy-dissolution attack by 1500C molten gallium. I use 1500C as an exaggeration, as even 1000C operating temperature would be great. Or even 500C with sulfur as top stage and steam as bottom stage, 2 stage, compared to the strictly water boiler reactors we have these days, that blow much of the heat energy out into the sky as a cloud plume.

Comment: Re:What else can they do? (Score 1) 155

by sillybilly (#47781669) Attached to: New NRC Rule Supports Indefinite Storage of Nuclear Waste

http://periodictable.com/Prope...

Shows that bismuth excels at neutron economy, while having a 271C mp/1560C bp. In case you can enclose the whole reactor into an electric oven, it may be an economic option, but all I can say is that it's not possible to do manual labor maintenance on 271C pipes and fittings that have been plugged and freshly thawed, but gallium melting at 30C, as a eutectic with zinc (or perhaps magnesium, or perhaps, but much more worse with sodium and potassium) even lower, so even pure cadmium is a joy to work with as far a maintenance personnel applying steam heat to thaw a frozen pipe goes, compared to all the other fast neutron breeder coolant options of sodium, lead, bismuth, NaK, and the like. The only question is whether neutron bombardment of cadmium generates serial neutron poisons, as neutron bombardment of sodium gives magnesium and aluminum, all low cross section, so cadmium giving germanium and arsenic, also low cross section, is that the case?

Comment: Re:What else can they do? (Score 1) 155

by sillybilly (#47781577) Attached to: New NRC Rule Supports Indefinite Storage of Nuclear Waste

Also graphite lubricated tubes - not a good idea, as graphite is a moderator, and mess ups in slight thickness may throw the whole reactor into uncertain territory, where moderation speeds up the nondepleted U235 reaction - a good idea would be to have only depleted uranium and thorium, and no U235 fuel.

So an ideal high temperature lubricant then is obviously MoS2, molybdenum disulfide, which does not moderate, from that standpoint, but at 1500C high temperature might be too much and might degrade, compared to graphite that only absorbs into the metal as carbide, but then it might glue and cement the rods to the tube walls via cementation. If both the fuel rods and the tube material have a lot of molybdenum content, MoS2 might be stable and not degrade to monosulfide, unless that one has lubrication properties too. It's very important to be able to slide long fuel rods in and out easily without them being stuck from thermal expansion and distortion and the like, for SCRAM shutdown purposes.

So maybe gallium on the other side could be the "heat sink thermal grease" to conduct heat between the fuel rod and the metal wall, assuming the structural material is already designed to resist gallium metal corrosion anyway on the other side. Also with liquid gallium you could have a huge gap between the tube wall and the actual fuel rod, also encapsulated into the structural material, to where huge thermal expansions and deformations can be tolerated, and the fuel rod does not get stuck, or even if it does, the other ones don't get stuck, and meltdown runaways are easy to shut down by fast removal of fuel to widely spaced distnaces - i.e. remove one rod just outside the reactor, remove another 10 yards away, etc. spread them all over the plant floor and air space widely separated from each other, preferably in a silicon or silicate like concrete neutron shield between them. This wide separation if left in free air mandatory, so critical mass is not attained, as inside the reactor the 2.9x cross section of liquid gallium does kill a lot of neutrons compared to free air, and if there is a total gallium loss, it should be replaced by having enough inventory of (cadmium no good because it's vapor at 1500C), or silicon(no good, it melts at 1410 leaving only) or boron (mp 2300C) control rods with maybe gadolinium as option (no good, melts at 1310, but might be a good option suddenly flood and kill the reactor with gadolinum balls (in case temp under 1310 melting point) shortstop, while the fuel rods get wiggled out, giving plenty of time to think, even weeks, then have the electric oven heat the reactor to above melting of 1310 and the gadolinium pumped out.) In case there is a leak that caused the gallium loss, and would cause a similar loss in gadolinium liquid, boron balls might not leak so fast, unless the gaping hole is too huge, in which case gaseous cadmium or halogens might help, but it's better if there is a way to insert iridium plates between sections of fuel rods, which does not melt at very high temperature, it's safe in air oxygen at high temperature, and has a decently high neutron cross section of 425, compared to 2450 for Cd and 755 for boron, as even boron might ignite and melt as boron oxide. Some kind of standard way or suddenly ripping apart the whole reactor assembly under total loss of gallum coolant, and separating it into say 3 or 4 or more guaranteed subcritical sections suspended in mid air with iridium plates inserted between them, or if in open air anyway, thick (silicon neutron absorbent containing) concrete plates might be a good idea, as inserting anything into a half meltdown reactor, such as a control rod, when the path and hole for it is deformed from the thermal meltdown, is not guaranteed to work, but if it has engineered weak spots for sudden ripping apart and separating the whole thing into small pieces, that might be easier to guarantee to work.
Of course nothing beats proper containment, and you're talking huge containment backing up huge containment, box in a box in a box, with cooling and neutron absorption capacity available to where seawater or lake water or river does not have to be used close to the radiactive zones, but the containment heat conducting buffer is able to take the heat away, without boiling off. A gallium pool shines again, as it's highly thermally conductive being a metal, but tin is cheaper, and lead might be a cheap option too, but lead boils lower than tin. Adding cadmium to the pool might be an option even if it boils off, as by boiling it cools, and it does not travel far away from the site to pollute the environment, but precipitates back out as metal, or oxide. Having a controlled meltdown that's able to sit at say 1000C and efficiently transfer heat through a gallium pool conduction, even directly to the atmosphere under such 1000C-room temperature gradients, would allow not having to use ocean water as a coolant like they had to at Fukushima. I just thought of it though, the issue with gallium is that it oxidizes in air to gallium oxide, and you cannot guarantee a nitrogen blanket atmosphere under conditions of a catastrophe, where things are blown away, whether from a tsunami or whatever reason. So the high conducting liquid cannot be a material that reacts with air, and then the cheapest option is silver micro-balls mixed in different particle sizes so better space filling and contact, as the other options - gold being too expensive as a coolant pool, and platinum palladium and the like too high a melting point, also expensive - that react with oxygen air and stay as metallic heat conductors, are too expensive.

Comment: Re:what could possibly go wrong? (Score 1) 253

by Greyfox (#47781373) Attached to: DoT Proposes Mandating Vehicle-To-Vehicle Communications
Yes, in that case they'll probably be at-fault, which really isn't much consolation when you have to stop everything you were planning on doing to deal with your damaged-ass car. And if you're seriously injured or killed in the accident, that will further ruin your day. And if you're really unlucky, the other driver will not be carrying insurance. The only time I've ever been in an accident that involved another driver, the other driver wasn't. And yes, it was required by law in that state. And yes, my insurance was pretty good about paying for my damages while they were suing the bejesus out of them. Took a month to put my car back together, and the body shop really didn't do a very good job of it. So in general if you can avoid an accident, it's really better to do so, no matter whose fault it's going to turn out to be.

Comment: Re:What else can they do? (Score 1) 155

by sillybilly (#47781331) Attached to: New NRC Rule Supports Indefinite Storage of Nuclear Waste

The issue with gas coolant is the low thermal capacity and conductivity and requiring fast flows - just think of your car radiator, what it looks like, and why it needs a fan. And with fast flows you can get uneven velocity distribution, and pockets of local overheating or local meltdown - something that does not happen in a car radiator because you have a maximum highest incoming temperature, but in a gas cooled reactor, such as stacked balls, temperatures can get locally very high to where the whole stack shifts and moves and makes flow distribution even worse. Such a shift in an advanced gas reactor was what prompted the Germans to completely cancel their nuclear research. Now there might be ways to help the issue, I just thought of it yesterday. Instead of a pyramid of stack balls dependent on all others to be in place, and not move, you could have heat exchanger like tube-banks or fuel rod banks that are securely fastened at the two ends, fighting any kind of shift of the whole mass, even if one bar individually overheats a lot, it does not push the other ones out of their position, even if it melts, because of the clearance gap between them being large enough to allow a lot of flexure. Now as something overheats locally, because of uneven flow and heat exhcange rate, it should have lower density, but when you're dealing with light helium (which is not an idea coolant for breeder or fast neutron reactors because it moderates), the variation in density, and buoyant force from that density is very low. So you need something that's very high molecular weight yet has good neutron cross section, for both non-moderation reasons and for buoyancy reasons. For the available options on neutron cross section, see
http://periodictable.com/Prope...
http://periodictable.com/Prope...
and also the note, the picture on how U235 cross section varies with neutron temperature or velocity, and fast neutronss are not as effective at splitting it as moderated slow neutrons, cross section depends on velocity, for reasons that we do not understand, or at least I don't. These cross section numbers are all experimental because we don't have a good understanding of the atomic nucleus, for instance there is probably no theory of the atomic nucleus that would explain why (gadolinium, promethium, samarium) cadmium, boron, silicon and hafnium would have a high cross section, but oxygen, beryllium, magnesium, bismuth, lead, zirconium(best construction material if hafnium free), aluminum and iron have low or decent cross section.
In this respect CO2 looks like an ideal candidate, however it's a molecule, a combination of elemental atoms, not just atoms, and when you get a fast neutron coming at it at high velocity, it may form CO + O, and C + O2, and it may char, however if the temperature is high enough, say over 800C in the reaction zone, this would automatically combust back to CO2, so it might take the beating. However the C at 12 molecular weight is still a moderator, somewhat, not as good as helium 4 or water with hydrogen at 1, but better than sodium coolant for instance. For a fast neutron breeder reactor you want a really bad moderator, that keeps the neutrons unmoderated, and fast, able to attack and breed from fertile but otherwise nonfissile materials, like depleted U238, or thorium(which is realtively abundant and cheap.) Not too many things are gaseous at high temperature, yet have a huge molecular weight, and noble gases pretty much top the cake at gaseousness, inertness, and high molecular or atomic weight and nonmoderation. But the heavier gases like Krypton and Xenon, also have a bad high cross section, but Argon, silimar in molecular weight to sodium, is similar to cross section to sodium, and it's relatively abundant and cheap. Sulfur hexafluoride might be even better, as the sulfur is about the same as sodium and argon, but the fluoride is really awesome, however you get the moderation from fluorine then, not the sulfur or sulfur hexafluoride. In a sense what is the lowest atomic weight element in your coolant gas that you can afford that's still a gas in the compound at operating temperature, but does not have a high neutron cross section. So oxides and fluorides are preferably out, but sulfur might be OK, as long as the fuel rods are sulfides(with mechanical strength and integrity issues there), and it may be preferable to phosphorous, which is hell like sodium when it leaks, and highly toxic in the solid white form. None of the higher halogens are usable, neither is mercury vapor, but zinc vapor might be OK. Not that these boiling points of sulfur 445C, (phosphorous 280C), and zinc 907 are extremely high, there would have to be a secondary circuit heat exchanger and heat engine maintained at that very high temperature so that the stuff does not solidify and plug up, before a bottoming cycle based on say sodium or mercury (which is OK outside the high neutron density reactor), which also have a bottoming cycle with steam. You would basically create a nuclear pile of sulfide rods fastened at the end with sufficient gap between them to allow for thermal flexing and expansion, filled with solid or glassy amorphous sulfur, and wait for the sulfur to boil off at 445C throughout the mix, and start up your "sulfur gas steam" going to your high temperature heat engine piston, or turbine. Localized melt down would not affect the whole pile - hopefully :) - if your rods are fastened well, are mechanically strong, and the molten sulfur+gas sulfur is sufficiently conductive. Zinc might be too high a boiling point for available material strength and corrosion resistance to zinc, at 900C, but would get awesome thermal conductivity in the solid and molten phase, to kill local meltdowns.
In case we talk about a non-gas reactor, just regular fast neutron coolant liquid, I think the russians, with their lead-bismuth eutectic missed out on gallium big time, also on tin, and gallium-tin eutectics, each of which have decent cross section, bad, but not that bad, and safety concerns that beat liquid sodium, and melting points and toxicity safety concerns that beat lead and bismuth (I don't really know gallium toxicity, if there is any.) Gallium has a melting point under the temperature of a human body, room temperature, and it stays liquid to 2400 C, so it seems like a super-ideal material in fast neutron breeder type nuclear applications, because it can be used to keep the fastened at both ends nuclear fuel rods safely from localized meltdown at super high temperatures, it's easy to thaw frozen lines, if it spills on the operators as a room temperature liquid they can just shake it off, it's not that toxic, and its neutron absorption probably gives germanium, which is also good on cross section - but the actual isotopes created may not be, and gallium that does absorb neutrons might create some germanium and arsenic isotopes that are actually neutron poisons, even if both germanium and arsenic natural isotopes are not. I wonder if this area has been researched. But to look for available options on coolant, go to http://www.science.co.il/PTele... sort the table by melting point, scroll down to near the area of mercury, gallium, potassium and sodium, and scroll up from there, while checking the candidates at http://periodictable.com/Prope.... It is important to have a low melting point of any coolant, that in worst case scenario has to be heated with an external torch in sections where there is no nuclear heat generated. So here is an idea of a thorium/uranium238/plutonium breeder/fast neutron combustor:

Make long fuel rods similar to heat exchanger tube banks, that are fastened at ends, and also have intermediate pillar fasteners that let the rods slide a bit, just like it's common in heat exchanger design, except you're dealing with solid rods not tubes that leak.

Find vessel materials able with high mechanical strength, low neutron cross section, able to withstand liquid gallium+zinc eutectic at above boiling point, say at say 1500 C zinc vapor temperature. Zirconium is pretty much the only option, with the exception of zirconium/magnesium oxide, zirconium/zirconium oxide, zirconium/zirconium carbide, zirconium/zirconium fluoride composites and surface coatings left behind after the etch that might help not dissolve zirconium into the gallium as an alloy. This nuclear metal steam boiler structural material constraint is the strongest, zirconium being the main choice at x0.184 cross section, and 1852C melting which is low, as none of the other hight temperature good stuff, like rhenium(x90), or tungsten(x18.4), able to take high neutron doses, with the exception of Niobium x1.15/2468C, Molybdenum x2.6/2617C, Ruthenium x2.6/2250C, which probably should be used, as carbide, oxide, fluoride cermets that are able to withstand corrosion from liquid gallium and zinc vapor at 1500C and high "metal steam" pressure.

Have a high 1500C temperature Carnot cycle heat engine (piston or turbine) enclosed in an electric oven that guarantees that temperatures never fall under the boiling point of zinc 907C, but definitely not under the 420C melting point, the heat engine materials made out of gallium/zinc corrosion resistant materials, and if you're away from the high neutron flux regions, your options of structural materials for pistons and turbine blades widen, including tungsten, rhenium, tantalum and osmium and the like, carbides, etc. The choice for zinc is that it is low boiling metal with a low neutron cross section, better than sodium, potassium and magnesium (each of which boil lower) when it comes to safety of explosions and leaks onto the backs of operators (of course you can still have zinc fires, and molten zinc can kill too, but once things settle down and you have a puddle of solid zinc and zinc oxide after a catastrophy, you can pick it up with bare hands, unlike sodium and potassium, hydroxide, magnesium is also good (especially on the neutron cross section aspect), touch the metal and the oxide it with bare hands, but it's an extreme fire hazard even in a solid block form compared to zinc, so as long as you can afford a huge reactor with acceptable neutron economics due the the zinc cross section absorption, zinc is preferable to magnesium on safety, melting point and boiling point, but if your neutron economics dictate you might have to switch to magnesium vapor instead (639C mp, 1090C bp), which however is very corrosive to things like molybdenum oxide or fluoride cermets, compared to zinc(420C mp/907C bp), but it would leave the carbides alone. Once you have to deal with magnesium vapor though, you might as well put up with sodium and potassium, which beat even zinc on melting point and boiling point, but leaks are hell, including the cleanup of caustic leftovers after a catastrophe.

This high temperature cycle should bottom out with another high boiling stuff, able to "raise steam" under 907 C, and this includes choices like mercury -39C mp/357C bp (toxic and not very abundant so very expensive, and you cannot afford leaks and explosions, though safety wise during an accident it beats a liquid sodium or potassium spray), sulfur 113C mp/445C bp, which with the 113 mp that's close to steam, might be a good choice, but the bp difference between 445 and 907 requires huge "sulfur-steam" boiler operating pressures, and something like potassium might be a lot milder on material constraints. Note that no organic materials like liquids or gases are usable above 600C in any application as they universally char to graphite, except methane, and the like, which however don't have a decent near room temperature liquid phase, as room temperature is the lowest available heat rejection temperature to the environment, and your final bottoming cycle working fluid, like steam, has to be liquid at room temperature, and all the other topping cycles have to be liquid at room temperature to very well above it, near the top of their cycle where they are performing a bottoming to another even higher temperature cycle, the closer the boiling point the lower the required operating pressure.

So as a summary, a good nuclear reactor design able to do breeding/fast neutrons by absence of moderators:
:
1. Molybdenum/Niobium metal+carbide/oxide/fluoride cermet structural material reactor.

2. Suitable nuclear fuel rods (metal with carbide, oxide or fluoride cermets as rods might work, or individual encapsulation into the structural material - in fact you could have graphite lubricated tubes where you can insert and pull the fuel, and the structural material holds back the working fluid, so direct contact may not be necessary, also allowing for SCRAM shutdowns by quick removal of the fuel rods) of great length fastened and suspended in a tube-bank heat exchanger fashion, with pillars in between, able to take localized thermal meltdown and deformation without affecting the whole nuclear pile and it's heat exchanging abilities - unlike a pebble bed reactor that shifts and collapses and melts in localized zones.

3. Use a gallium liquid drench for all the fuel rods, out of which boils the top temperature working fluid, zinc being preferred, but magnesium and sodium considered as options.

4. Enclose top cycle heat engine (piston or turbine) in an electric oven that can be guaranteed to keep everything at above 907 for zinc. (Sort of like an external torch that does work, unlike the jerry-rigged portable ones the russians are stuck using on their submarines.) Use a bottoming fluid like sulfur or potassium for the 2nd stage.

5. Enclose 2nd stage in a similar electric box guaranteeing 445C for sulfur, or 100C for potassium.

6. Use ultra high pressure steam raising at 445C as 3rd and final stage, or insert yet another working fluid for 4 stages between steam and sulfur (and the options, including organic materials become greater.)

Under such circumstances, the theoretical Carnot cycle efficiency numbers would be 1-T2/T1, in Kelvins, so for 1500C zinc vapor pressures that would be 1- (100C+273C steam)/(1500C+273C zinc)=1-373/1773=1-0.21=0.79%, compared to the present 10% with steam only, using less than 1% of the total uranium 235, and throwing away the 99% usable U238 waste, that a huge scale breeder reactor would be able to burn and utilize. Of course that 80% is theoretical, and you may end up with 45% which would be an amazingly good number, but the higher the efficiency, the less the waste cooling capacity required also, and if you could get 100% efficiency, you could not tell a nuclear power plant from a distance because there would be no external heat exchange, and no cloud plume rising into the sky. Every time you see that cloud plume from a nuclear power plant, that's waste heat, and the higher you are able to push your top operating temperature though material selection like molybdenum and niobium cermets, the less the waste heat.

Comment: Re:central storage or n^x security guard costs / s (Score 1) 155

by sillybilly (#47780559) Attached to: New NRC Rule Supports Indefinite Storage of Nuclear Waste

Dandelions, or Taraxacum officinale, has a white sap, and it taste bitter, but it's not that toxic. They have a modification, a breed, where they make rubber out of the milky latex, as the regular wild type has low latex content. They are gonna make tires of it, just like from the white sap that exudes from rubber trees, natural rubber latex. Natural rubber is mostly inert, it passes through you, not that toxic - just chew and swallow a latex glove which is processed natural latex into a solid form - though some people are allergic to it. I bet there are tons of things where the sap is clear and are toxic, as clarity is dependent on the suspension of insolubles, mostly latex-like rubber particles, and if the toxin is soluble, then it can be deadly yet the sap clear. True that a lot of toxins in nature are extremely complex, and mostly insoluble in water - snake poison for instance is white too. But it all depends on the makeup, and if it has enough hydrophilic groups, it may be soluble at very high molecular weight.

Comment: Well Lessee (Score 1) 337

by Greyfox (#47779373) Attached to: Ask Slashdot: What Are the Best Games To Have In Your Collection?
Cards against humanity if you're having friends over. Unless they're Mormons. Then, cards against humanity with all the expansion packs.

I've probably put 80+ hours into dwarf fortress. And I haven't even started doing megaprojects yet. I did have a king set up residence once, before everyone died.

Comment: Re:R.I.P. Mozilla (Score 1) 150

by Khyber (#47778285) Attached to: Mozilla Rolls Out Sponsored Tiles To Firefox Nightly's New Tab Page

"Well they have full control and all they have to say is you want this spot, you can have for this much but you have no control over anything that happens to the browser."

As if drive-by malware embedded in ads hasn't happened before. Yea, you might want to have a seat, I got some things to tell you.

If all the world's economists were laid end to end, we wouldn't reach a conclusion. -- William Baumol

Working...