Japan Pictures Likely Show Melted Fukushima Fuel for First Time • Hacker News Board

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#121

Post by DrScump » Sun, Jul 23, 2017, 9:03 AM UTC

Fej wrote: post #103

jmhobbs wrote: post #98

Earlier quoted context omitted.

Underground coal fires like the Centralia mine fire are an interesting and not as well known problem as oil spills. > The fire is burning in underground coal mines at depths of up to 300 feet (90 m) over an 8-mile (13 km) stretch of 3,700 acres (15 km2). At its current rate, it could continue to burn for over 250 years.[2] https://en.wikipedia.org/wiki/Centralia_mine_fire

Is there no way to put it out? Starve it of oxygen? Tons of water?

Sequester CO2 there? Helps on two levels.

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#122

Post by Boothroid » Sun, Jul 23, 2017, 9:29 AM UTC

mikeash wrote: post #64

Boothroid wrote: post #43

A common response from defenders of nuclear when concerns are raised is to point to the impact of other energy sources, and say that nuclear is better in those terms. But I just cannot get away from the thought that whilst in aggregate those other forms of energy (fossil fuels, etc) might be provably worse than well managed nuclear within a particular analysis, humanity does not seem capable of this good management o…

The only reason fossil fuels don't have the same potential to go spectacularly bad is because humans don't consider enormous damage to be "spectacular" when it's spread out. Consider: coal alone kills about a million people a year. If those were all concentrated in a small area, we'd call it the greatest disaster the world has ever seen. But it's spread out over the whole world, so we just shrug our shoulders and say…

..you also need to consider that we still have no proven way of handling high level waste, and that nuclear accidents can render huge areas completely unusable for decades, and that clean up of nuclear sites can consume utterly huge amounts of money. The same is not true of fossil fuels. Also don't discount the utterly huge amounts of energy required to construct, operate, and decommission nuclear plants. Nuclear industry apologists often conveniently exclude these from their analyses.

I don't see that you have refuted my point - you just have to look at the record (thousands of nuclear incidents worldwide over decades) to see that humanity apparently is not capable of safely using nuclear, and I'm sceptical that the benefits in terms of reduced exigencies are as great as is often claimed. And personally I'd far rather have the damage spread out over a wide area if it means we don't have to every now and then throw away all the milk in Wales for years and distribute iodine tablets to thousands..

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#123

Post by mikeash » Sun, Jul 23, 2017, 2:20 PM UTC

Boothroid wrote: post #122

mikeash wrote: post #64

Earlier quoted context omitted.

The only reason fossil fuels don't have the same potential to go spectacularly bad is because humans don't consider enormous damage to be "spectacular" when it's spread out. Consider: coal alone kills about a million people a year. If those were all concentrated in a small area, we'd call it the greatest disaster the world has ever seen. But it's spread out over the whole world, so we just shrug our shoulders and say…

..you also need to consider that we still have no proven way of handling high level waste, and that nuclear accidents can render huge areas completely unusable for decades, and that clean up of nuclear sites can consume utterly huge amounts of money. The same is not true of fossil fuels. Also don't discount the utterly huge amounts of energy required to construct, operate, and decommission nuclear plants. Nuclear ind…

If you look at the record, you see that fossil power is vastly more dangerous.

Do you really prefer killing a million people a year, every year, to "every now and then" throwing away all the milk in Wales, just because the million deaths are spread out? I can't fathom this.

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#124

Post by nate_meurer » Sun, Jul 23, 2017, 3:51 PM UTC

frik wrote: post #118

nate_meurer wrote: post #81

Earlier quoted context omitted.

Honest question: do you really think they haven't thought of this? You think that none of these engineers and scientists have yet thought of your shielded fiber optics idea? I'm not trying to be mean, I'm really curious. Radiation shielding is a hard problem. For meaningful reduction of xray and gamma radiation in this environment, we're talking inches of lead cladding [0]. And even that won't ensure a useful lifespa…

* Fiber cables (that OP and I wrote) means a cable made out of glass - no problem at all for radiation. (face palm #1) * You can transfer light through such cables. This means you use one cable to send light into the scene and another cable to see to the scene. Please just look up how endoscopy works for many many many decades, long before computers were a thing. (face palm #2) You probably have a SPDIF connector at…

> "a cable made out of glass - no problem at all for radiation"

I don't know where you got that idea, but it's very wrong. Optical glasses of all kinds are quite vulnerable to darkening, clouding, and embrittlement by much lower levels of ionizing radiation than those at Fukushima [0].

Even if you shielded the fibers with centimeters of lead, the radiation received along the fiber's length would quickly render it useless for either imaging or lighting. And with that much shielding, good luck moving it around. How exactly do you think you'll get your low-tech thingy into place, maneuvering it hundreds of meters of abandoned building, ruble and industrial wreckage? Remember that you can't even be in the parking lot unless you're in a heavily shielded truck. How would you protect the optical assemblies at the working end of your cable, which cannot be shielded and are thus exposed to hundreds of Sv/hr? Do you know how Toshiba designed the optics on their Scorpion robot? How would you improve on their materials or lens arrangements? Have you considered the thermal effects of this much radiation, which is capable of heating the internal elements of your assembly to hundreds of degrees?

Read the links I gave, maybe do a bit of googling, and be assured that you have not actually outsmarted hundreds of nuclear physicists and robot experts with your super clever idea.

0: http://www.dtic.mil/dtic/tr/fulltext/u2/a013786.pdf

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#125

Post by frik » Sun, Jul 23, 2017, 5:13 PM UTC

nate_meurer wrote: post #124

frik wrote: post #118

Earlier quoted context omitted.

* Fiber cables (that OP and I wrote) means a cable made out of glass - no problem at all for radiation. (face palm #1) * You can transfer light through such cables. This means you use one cable to send light into the scene and another cable to see to the scene. Please just look up how endoscopy works for many many many decades, long before computers were a thing. (face palm #2) You probably have a SPDIF connector at…

> "a cable made out of glass - no problem at all for radiation" I don't know where you got that idea, but it's very wrong. Optical glasses of all kinds are quite vulnerable to darkening, clouding, and embrittlement by much lower levels of ionizing radiation than those at Fukushima [0]. Even if you shielded the fibers with centimeters of lead, the radiation received along the fiber's length would quickly render it use…

Look at the OP news article, they took a picture - so they have already a transparent material (type of glass or plastic). There you go. My comment was about a low tech bigger scale endoscope instead of error prone high-tech robotics.

And glass and probably types of plastics can be quite hardened against negative effects of radiation. Think of transparent windows where you can look at the reactor core of research reactors, NASA space missions with high precision optics that last for decades, etc.

The issue in Japan is their culture, their problem with "loss of face" which inevitably caused problems in the hours when the worst case scenario unleashed - and the whole world watched 24h live while they did little and USA proposed (and had them ready on the nearby ship) to send in helicopters with backup generators but Japan made no official request for help - lesson learned, in the end US should have crossed their border and fixed the generators because Japan hasn't acted rational at all. Even the years later, they could have learned from Russia how to fix it quickly by sending in human people. But again false bride, and "loss of face" gets in their way. They keep going on with business as usual, and the leaks aren't fixed or anything worth mentioning. Chinese and Japanese have a related culture, yet Chinese know what they are doing and are very successful.

"All optical fibers undergo some darkening depending on a number of factors that include: ionization type, optical fiber core glass composition, operating wavelength, dose rate, total accumulated dose, temperature and power propagating through the core. Since attenuation is composition dependent, it is observed that fibers having pure silica cores and fluorine down doped claddings are amongst the most radiation hard fibers. To minimize damage consequences, it is better to use a pure silica core fiber at higher operating wavelength, higher temperature (accelerated recovery) and higher signal power (photo-bleaching)." -- https://en.wikipedia.org/wiki/Radiation_effects_on_optical_f... -- (shortened snip)

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#126

Post by nate_meurer » Sun, Jul 23, 2017, 6:16 PM UTC

frik wrote: post #125

nate_meurer wrote: post #124

Earlier quoted context omitted.

> "a cable made out of glass - no problem at all for radiation" I don't know where you got that idea, but it's very wrong. Optical glasses of all kinds are quite vulnerable to darkening, clouding, and embrittlement by much lower levels of ionizing radiation than those at Fukushima [0]. Even if you shielded the fibers with centimeters of lead, the radiation received along the fiber's length would quickly render it use…

Look at the OP news article, they took a picture - so they have already a transparent material (type of glass or plastic). There you go. My comment was about a low tech bigger scale endoscope instead of error prone high-tech robotics. And glass and probably types of plastics can be quite hardened against negative effects of radiation. Think of transparent windows where you can look at the reactor core of research rea…

LOL, please show me an example of a "window where you can look at a reactor core". Show me a window protecting someone from thousands of rads/hr from an active reactor core. Please :) And no, the radiation seen in space exploration is not comparable to the levels at Fukushima. Not anywhere close.

Have you ever actually seen an endoscope? Do you have any idea how complicated they are, how many optical elements they have and how precise the tolerances must be?

Did your study of wikipedia reveal the extent of transmission loss in rad-hard optical materials after exposure to levels of radiation near those at Fukushima? Because the link I gave you does. Read that and tell me how long you expect your fiber optics to last down there. I'll give you a hint: not very long.

Tell you what, just make a sketch of your "low-tech" endoscope that withstands hundreds of Sv/hr, deals with hundreds of degrees of internal heating, is waterproof of course, and is robust to extreme physical abuse. And then come up with a way to remotely maneuver it into place through hundreds of meters of industrial wreckage, without using a robot.

Then get ready to be famous, for your brilliant low-tech solution will be lauded by the international team of scientists and engineers working on Fukushima who simply hadn't thought of it for over 6 years.

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#127

Post by nate_meurer » Sun, Jul 23, 2017, 6:30 PM UTC

marze wrote: post #112

nate_meurer wrote: post #100

Earlier quoted context omitted.

Where'd you get that idea? :) You absolutely would need cladding on a light pipe, and lots of it. All kinds of optical materials are subject to darkening, clouding, and embrittlement by much lower levels of ionizing radiation than exist in the reactor [0]. Again, here we're talking about tremendous amounts of radiation over much of the pipe's length, so even small amounts of damage per unit length are going to quickl…

I see the problem, you are misunderstanding the proposal. I suggested using optics for imaging, and fiber to bring in illumination. You'd have a telescope-like camera at the far end. No image transmission through a fiber bundle. You would need refractive elements that would work in the high radiation environment. As for the illumination, collimated light down a polish steel tube would obviously work, but a rod of gla…

Yes but illumination is not the problem here. The robots have no problem with lighting.

Imaging is a problem. Your search for "refractive elements that would work in the high radiation environment" would likely lead you to something like the optics that Toshiba has developed for these robots. Remember to also account for the thermal effects; radiation of this magnitude is capable of heating the internal elements of your assembly by hundreds of degrees, and your telescope-like camera must maintain its tolerances very precisely to produce a usable image. And perhaps the hardest problem of all: how to maneuver all of this stuff into place through hundreds of meters of industrial hell, where humans can't even stay long in the parking lot outside of a shielded truck. Tackle these problems using no robotics, and you'll be famous, I guarantee it :)

Re: Japan Pictures Likely Show Melted Fukushima Fuel for First Time

#128

Post by Boothroid » Tue, Jul 25, 2017, 4:13 PM UTC

mikeash wrote: post #123

Boothroid wrote: post #122

Earlier quoted context omitted.

..you also need to consider that we still have no proven way of handling high level waste, and that nuclear accidents can render huge areas completely unusable for decades, and that clean up of nuclear sites can consume utterly huge amounts of money. The same is not true of fossil fuels. Also don't discount the utterly huge amounts of energy required to construct, operate, and decommission nuclear plants. Nuclear ind…

If you look at the record, you see that fossil power is vastly more dangerous. Do you really prefer killing a million people a year, every year, to "every now and then" throwing away all the milk in Wales, just because the million deaths are spread out? I can't fathom this.

By some analyses the C02 output of nuclear is on a par with fossil fuels once the whole cycle is taken into account. Let's not forget that uranium has to be dug out of the ground, processed etc., power plants built which generally uses a lot of concrete, big holes dug in the ground to put the waste into (since we have no good way of reprocessing much of this waste). None of this comes cheap in C02 terms. I get it, you love nuclear, but supporters of nuclear often conveniently ignore.