Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?

Comment Re:High vs Low (Score 2) 301

because the fast neutrons eventually destroy every known material used as the plasma-facing "first" wall. That's something the ITER fanboys are not telling you (for obvious reasons).

That's weird, I've been aware for a decade or more now that ITER is working on assorted possible first-wall technologies and the JET in Culham, England is being repurposed as a wall material testbed. Maybe they didn't tell you but they've been telling everyone else.

The walls are going to be sacrificial, needing to be replaced using remote handling equipment. It's part of the "E" in the acronym "ITER", standing for "Experimental". Lithium, converted into tritiurm and deuterium by neutron bombardment is one possibility for walls as its product is a fuel source for further fusion. Other tougher materials might last longer, possibly decades or more before needing replacement though. ITER is a testbed for such research.

Comment Re:I can understand small first batches (Score 2) 109

Looks like there are a lot of people that have completely different uses for their Pies than mine

I'm waiting to get my hands on a Pi Zero. I don't need networking, wired or wireless, I don't need external storage or lots of RAM, it's for a single purpose task using a USB port and its video output to sit between a microscope webcam and a junkbox TFT display. Five dollars is a bargain, a regular Pi with all the extra bells and whistles is a waste of money for this project (basic image processing for automated inspection purposes).

The Pi Zero has use cases. They're really not suitable for folks with connectivity requirements, external storage or elaborate interfacing but as a blobject for glueing some bits together they can't be beaten at that price.

Comment Re:The problem is lackadaisical battery manufactur (Score 1) 333

If they were investing into the R&D to keep up with Intel and Moore's law... doubling their capacity every 18 months as well...

Li-technology batteries hold about 25% of the energy of a similar mass of TNT explosive at the moment. If the manufacturers kept up with Moore's Law as you would like then within three years or so they'd be equivalent to TNT in energy density. Wouldn't that be fun?

Comment Re: How much would it help? (Score 1) 262

If it got them down the mountain a second faster than the other person quite a few of them would drink mercury. Consider the doping and blood transfusions and all the other efforts to gain an edge on the competition while accepting that everyone else are pulling the same tricks in pretty much every sport. Cyclists have died at the roadside from the effects of doping and it didn't even cause a blip in the efforts of the rest of the field to gain that podium place by better chemistry.

At that level winning is everything -- "Winning isn't a matter of life and death, it's more important than that" is a famous quote by a football manager.

Comment Re:Doubling the number of nuclear reactors works. (Score 1) 143

As far as I know there have not yet been any completed sales of the ACPR1000 reactor (now known as the Hualong One) outside mainland China. There has been a push by the Chinese nuclear industry for export orders and several "expressions of interest" but at the moment no-one is breaking ground on a Chinese-model reactor construction project outside China itself. I don't know of any possible buyers that have even completed the licencing process needed before starting actual construction.

Comment Re:Doubling the number of nuclear reactors works. (Score 3, Interesting) 143

Question -- when you say the Chinese have installed "installed 17 to 22GW of solar power" in 2015 does that mean the installations will produce an average of 17 to 22GW of power or do you mean the solar plants have that maximum capacity but will only deliver a fraction of that amount of electricity over the period of a year, day and night?

The nuclear reactors China is building and planning to build will operate with an uptime of about 90% or so, so the six (by my count) 1GW reactors they brought into operation in 2015 will produce an average of 5.5GW day and night, rain and shine. The twenty or so reactors under construction will add another 15GW or so of similarly reliable power over the next few years.

The bad news is that the Chinese are going to keep building new coal power plants, more efficient and less polluting than the older plants being decommissioned or retrofitted because they need hundreds of gigawatts of new electricity capacity to meet demand and coal is cheap and readily available (China mines about half the world's total output of coal annually) and no-one cares enough about the ongoing pollution disaster and its health effects for them to stop burning coal.

Submission + - Last operating Magnox nuclear reactor closes

nojayuk writes: The world's last operating Magnox nuclear reactor, Wylfa 1 in Anglesey, Wales was closed yesterday after providing carbon-free power for over 40 years. Wylfa1 was originally scheduled to shut in 2012 along with the adjacent Wylfa 2 reactor but it was kept operating for another three years with the innovative use of partially-burnt fuel from Wylfa 2 and remaining stocks of fresh Magnox fuel. The reactor will be defuelled and move into its decommissioning phase over the next year.

The Magnox design used gas-cooling and a carbon moderator with the capability to produce weapons-grade plutonium depending on how it was fuelled and operated. Its design fed into the next-generation AGRs which provide about 6GW of Britain's electricity supply today.

Comment Re:Probably safe (Score 3, Interesting) 70

the bulk metal is difficult to ignite.

Magnesium alloys are very good heat conductors so applying flame to one area of a large solid piece of magnesium alloy won't ignite it, any more than, say, aluminium alloy materials as the heat is ducted away from to contact point. On the other hand magnesium powder, thin ribbon or wire will burn without too much effort.

Acquaintances of mine who put some magnesium-alloy aircraft wheel hubs in a bonfire were somewhat disappointed by the lack of performance until one of them rigged up a feed of pure oxygen into the bonfire at which point they lit off quite nicely.

Comment Re:Wonder if this can be used for some more items (Score 3, Interesting) 129

Most if not all of the Soviet-era lighthouse RTGs used Sr-90, an isotope of strontium rather than Pu-238 as a heat source. It required heavier shielding than a Pu-238 RTG but in land-based generators the extra mass of the case didn't affect its capabilities the way an RTG to be mounted on a spacecraft would.

Sr-90 can be sourced from spent fuel from power plants and the Soviets had a fuel reprocessing capability to produce Sr-90 in quantity. The Russian government is looking to upgrade and expand their existing fuel reprocessing operations, in part to supply their next-generation series of fast reactors like the BN-800 with recycled spent fuel.

Comment Re:Payload around 500 Kg (Score 1) 29

They aren't strap-on boosters, they're liquid tanks for the vectoring system for the solid-fuel core first stage. It works by injecting a strontium-based liquid into the nozzle to change the burn characteristics. It's crude by the standard of other solid-fuel launchers like Vega and Epsilon which use nozzle deflection systems but it works and it's cheap.

The solid-fuel strap-ons are considerably larger than the liquid tanks. You can see a diagram of what they look like on the Wikipedia page about the PSLV.

Engineering-wise the PSLV is a bit of a dog's breakfast -- the first stage and third stage are solid-fuel as are the strap-ons (if flown), the second and fourth stages use UDMH and N2O4, old Cold-War missile hypergolic fuels that have generally fallen out of favour with other launcher builders. The one advantage they have is storability with no cryogenic handling required on the pad, not even LOX.

ISRO have another launcher, the GSLV which is more advanced in design with a nozzle-vectoring solid-fuel core and solid strap-ons but it's got a UDMH/N2O4 second stage and a new fully-cryogenic upper stage. Interestingly enough they flew a prototype crew capsule with it on a suborbital mission last year.

Comment Re:I own NiCad, NiMH, lIon, liPoly (Score 1) 151

I've got some NiMH AA batteries (Sanyo Eneloop) I bought in 2007 that I still use regularly. They've been through a couple of hundred charge cycles or so in cheap non-intelligent chargers of various kinds. I don't know what capacity losses they've suffered but they still do the job in flashlights and a digital camera. They're the low-self-discharge type that holds a charge for long periods and they're still doing that part of the job too, even after nearly a decade. I expect I'll still be using them for another few years.

Lithium batteries don't last that long from my experience. They need careful charging and balancing, they can't be deeply discharged without suffering degradation and they can catch fire if things go wrong. Their capacity in terms of volume and weight is impressive but it comes with a lot of extra baggage.

The battery tech that impresses me is nickel-iron. NiFe cells can be deep-discharged repeatedly without effect and they last in service for decades with some basic maintenance. They're not compact or light though and for some unknown reason they are incredibly expensive.

Slashdot Top Deals

Machines that have broken down will work perfectly when the repairman arrives.