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Comment Re:Blimey (Score 1) 435 435

You're perfectly correct that MSRs don't actually run on Thorium. That's one of the reasons they'd be an effective nuclear waste burner.

The advantage that MSRs have over pellet/pebble/rod-based reactors is that when you throttle down, an excess of xenon-135 builds up. This is a neutron poison and damps down the reaction, making it hard to throttle up again until it's decayed (that takes a while. The Half-life is 9.2 hours). Attempting to push through the xenon poisoning by setting the power to 11 can be catastrophic - this is what took out Chernobyl. http://hyperphysics.phy-astr.g...

Because the fuel is not sealed into capsules in a MSR, the Xenon can be extracted into the thermal expansion headspace just before the circulation pump by sparging it (https://en.wikipedia.org/wiki/Sparging_(chemistry)). You need to do this to get helium and other gasses out anyway so it's not a big deal. The end result is that throttling is fully linear and because MSRs don't suffer from steam voids if you snap to full power, the reaction rate can track load at least as fast as a hydro plant and probably as fast as a OCGT plant.

I was going to write a lot more but given this is about space applications it's probably irrelevant. You'll need a thorium blankie for your U233 MSR reactor or you'll run out of fuel eventually. Having it soak up stray neutrons is a good thing in what would probably be a relatively confined space.

Comment Re:Country run by oil barons does nothing!!! (Score 1) 195 195

"Advances in uranium mining made it substantially cheaper to mine and refine fresh fuel than reprocess "spent" fuel."

Reprocessing fuel rods allows extraction of bomb-making materials. As such, it's a highly controlled process (political and military) and the USA + Russia both offer subsidised uranium as reactor fuel to try and discourage countries from developing their own reprocessing or enrichment systems.

Fun factoid: Iran has several hundred kilos of 40% (or more) enriched U235 squirreled away as reactor starter material. Even Mossad have reported that they don't believe they're working on bombs, as they'd have already demonstrated one if they were.

Comment Re:This is outrageous (Score 1) 267 267

"For that matter, the continued dominance of middleman organisations like movie studios, book publishers and record labels is arguably the biggest problem with the creative industries right now. "

It is those middlemen who are the ones lobbying for these laws. They freely rip off everyone in sight and feel themselves to be above the law.

The _entire_ Hollywood movie industry is worth less than Microsoft even in its diminished state. It's an idle fantasy, but one of the the things companies like Google could do to kill the relentless litigation is simply _buy_ the companies involved with money found down the back of the sofa.

Comment Re:This is outrageous (Score 1) 267 267

" But professional copyright infringement, where you're actively ripping off works for substantial profit, can be a criminal matter, punishable in criminal courts with fines and jail time. "

I look forward to seeing various music company executives in the dock. The well-documented systemic copyright abuse perpetrated by these companies against individuals, as well as standover tactics against "creatives" essentially forcing them to hand over their entire intellectual property portfolios with no or negligible recompense vastly dwarfs any other kind of copyright infringement that exists.

The reality, despite whatever you may _think_ it is, is that these laws are vastly disproportionate and mostly used by media companies to justify hiring City of London Police to go and kick in doors at the other end of the country in a blaze of publicity, with newspapers or TV illegally invited along - with charges quietly dropped a few days later when the Crown Prosecution Service points out the raids weren't legal, the charges won't stick and the recipient of the dawn raid probably has justification for substantial claims against the COLP and the companies which hired them, if he can afford a lawyer.

Comment Re:This is outrageous (Score 1) 267 267

"These penalties are the ones aimed at criminal copyright infringement. "

Which means whatever those prosecuting want it to mean.

The most blatant and widespread copyright violations are perpetuated by media companies against individuals in any case. Good luck getting a company officer jailed as a result.

Comment Re:This is outrageous (Score 2) 267 267

"Stop giving them any more wealth. Don't buy..."

This is happening in spades. Numbers are in constant decline.

Media companies try to paint this decline as proof that there is mass piracy going on, rather than admit they're not producing prodict that people want to buy - and the US + UK governments are falling for it, passing laws to prop up these companies, in the same way they tried to prop up their car industries rather than admit they were simply not producing what customers wanted.

Comment Re:This is outrageous (Score 1) 267 267

"Thus there's no place for actual creative people in this "industry" now. It's only for rentier who want to establish another aristocratic class."

Rent-seekers moved into the music and movie industries almost as soon as they were created.

What's happened since then is that they've become more blatent and more brazen about what they do and having exhausted all possible income streams from artists and buyers(*), faced with widespread consumer resistance, they are now doing everything they can to scare people into paying for product.

The real effect is more likely to be faced with a choice of paying for something they might have listened to but wouldn't pay for, most consumers will simply shrug their shoulders and walk away. The cartels will use the inevitable plummetting sales as further justification for claims that mass piracy must be taking place and push for even more draconian laws.

(*)recording sales were already declining when CDs came along, bubbled for a while as people rebuilt their libraries in new format and were already falling away again before fileswapping mp3s was common

Comment Re:Confused (Score 1) 267 267

"I agree that artists deserve some kind of compensation"

In the current environment, about 1 in 1 million artists do. The rest end up being burned and in debt.

Recording labels hate the Internet and the fact that it's forced them to bring their back-catalogs online. That's far less profitable than selling umpteen million copies of the latest formulaic pap, along with a few tried-and-true classics to pad out the shelves.

Comment Re:Just a thought (Score 1) 267 267

"For instance, you copy a CD that retails for $19.95, you get fined $39.40 which goes to the injured party"

When artists are writing newspaper stories pointing out that labels make money and artists end up with nothing more often in not, in major debt), who is the more injured party?

Comment Re:Country run by oil barons does nothing!!! (Score 1) 195 195

"And we still need the lithium-7 to 99.99% purity (they are doing it in China, but the COLEX process is not legal here and we don't have an alternate). "

Do you though? For reference, Li7 is normally 92-5% of natural Lithium.

In the reaction process Li6 gets fissioned to tritium (which is a useful material for civil purposes) and you end up with free fluorine plus tritium gasses (easily extractable in the pump void space via sparging as is already done for xenon and helium removal) plus possibly some free uranium/thorium flouride materials which need to be separated out (bearing in mind that fissile fuel is only 1% of the salt load, the vast majority of fissioned Lithium doesn't alter the overall burn ratio). This can be dealt with by simple chemical separation and the result is that the lithium in the system is effectively self-purifying.

As you already have to cater to free flourine in the loops (it will be released by radiolysis whenever the fuel is cooled below freeze point) this doesn't really require extra materials engineering to handle it, although it does mean you need to have a vapor separator in the secondary loop to cater to (much lower levels of) lithium fissioning - but you need that anyway.

One of the good things about MSRs is that they do tend to lend themselves to "bucket chemistry" more readily than other designs. Using natural lithium will lower initial efficiency slightly, but you end up with a useful byproduct to go along with a number of other useful byproducts (all those noble gases have uses, even if you need to let the xenon sit around for a decade before selling it. Helium shortage? What Helium shortage?).

I'd be more worried about core design than lithium isotopes, and about beryllium toxicity from the current salt designs - which are a good reason alone to avoid LiFBe compounds.

The fact that a graphite core is eroded away over a 8-10 year period, requiring drain/rebuild is bad enough. The fact that you'll need to inert the atmosphere to prevent a fire inside the reactor vessel if you ever SCRAM the thing is far worse - the target should be _zero_ flammables - bear in mind that Chernoybl was so bad because it was a graphite moderator fire and the Windscale military reactor fire would have been worse than that if it wasn't for the insistence on "unnecessary" filtration devices fitted to the chimney (again, it was a graphite moderator fire)

On the bright side, the graphite problem appears to have been solved in a manner which also halves the physical size of the core. I can't find the cite at the moment, but at least one outfit has come up with a design based on zirconium ceramics which is erosion resistant.

Comment Re:Country run by oil barons does nothing!!! (Score 1) 195 195

MSRs weren't even on the drawing board when we built light water reactors.

The fact remains that they were proved viable and practical in the 1960s, but Nixon canned them on political/military grounds.

Political: Jobs for the old boys.

Military: Not just that the light water cycle lends itself to being a plutonium source when the rods are reprocessed, but that the enriching process is an essential component of making fusion bombs.

My earlier comment: "More than 1/3 of the mined uranium metal is tossed as useless" is not quite accurate. Purified U238 is used as the "tamper" (ie, outer shell) of thermonuclear weapons (Teller-Ulam designs, also known as H-bombs, although technically they're a fission-started, fusion-boosted, fission weapon(*)) and any U235 contamination in that shell prevents it working effectively.

I had been wondering why the US military are the ones enriching uranium for civil reactors until I realised the link.

Alvin Weinberg's treatment by the US nuclear establishment is nothing short of inexcusable. The man not only developed the current technology we use (pressurised LWRs) but came up with an alternative which he felt was far safer, yet he got ostracised for his views about LWR safety - views which have proven 100% correct.

(*) An "H bomb" is a fusion bomb inside a fission bomb, wrapped in a fission bomb (U238 shell). The initial fission bomb sets off the fusion bomb aided by neutron reflection off the inside of the U238 shell. The fusion bomb in turn provides enough energy to make the U238 fission. A "neutron bomb" substitutes Tungsten or other neutron-reflecting metal for the U238 outer shell.

Comment Re:Concorde 2.0 (Score 1) 238 238

" Doing something about the sonic boom would be useful "

Concorde's boom wasn't particularly loud. Noticeable yes. Annoyingly so, no. Not enough to break windows, etc. Much quieter than a passing Harley, as a f'instance.

US overland experiments on boom were conducted using the Valkerie and that was extremely loud, being an old design which predated area rule discoveries and had to be modified during design accordingly.

It was those results which were used to justify banning overland SSTs but the actual reason for the ban was political pressure from USA aircraft makers who didn't have a SST of their own.

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