High radiation readings at Fukushima’s No. 2 reactor complicate robot probe

http://www.japantimes.co.jp/news/2017/02/10/national/high-radiation-readings-at-fukushima-no-2-reactor

by sinalc0 • 9 years ago

79 46 9 years ago

japantimes.co.jp

So, what's the long game with Fukushima? This has been going on for so long and it's concerning that seemingly very little progress has been made.

Edit: added "seemingly"... as I can say for certain the degree of progress that has been made.

sudosushi• 9 years ago

It's always been a multi-decade cleanup project, but recently the estimates were pushed further into the future (~40 years). Also, the last article I'd read puts it at ~$180 billion. I can easily see that double before the end.

colordrops• 9 years ago

Is there a breakdown of the costs of the cleanup?

gozur88• 9 years ago

Every day they let it cool the job gets a little easier, so they're in no particular hurry.

Animats3• 9 years ago

Decommissioning a damaged reactor is insanely expensive and, in too many cases, not possible. Chernobyl is at best contained, not cleaned up. 30 years after the fire and meltdown, the giant curved roof built to cover it was moved into position last year. That will hold things for a few more decades. The next generation will have to work out the next steps.

The jammed AVR pebble bed reactor in Germany is contained, but there's no way to dismantle and dispose of it. Current plans are to wait 60 years and then try to figure out something.

Fukushima’s mess will also take decades. The site generated huge amounts of contaminated water, and there's now a processing plant to take most radioactive contaminants out of the water. The water still has tritium after processing. The half-life of tritium is 12 years, so that will cool off in a few decades. Meanwhile, huge farms of water tanks store the stuff. Lots of radioactive dirt has been dug up and buried deeper somewhere else. There's a refrigerated "ice wall" to try to stop leakage into the ocean. Not much has been done with the reactor vessels themselves. As today's story reports, they can't even get a robot close to the reactor vessel.

This makes one very discouraged about nuclear power.

pinpelipon• 9 years ago

Tritium & tritiated water can be somewhat easily separated from water. Just freeze the mixture, and it forms layers. However, there probably is quite a bit of tritiated water.

codecamper2• 9 years ago

Solar panels folks. Solar panels. Wind. Batteries. We can do it, no problem. Electricity costs a little more, but your car ends up costing less. Less maintenance on fewer parts - just swap out the battery which declines in cost each year.

Keep fossil fuels and wood for the things solar & wind will have trouble covering: airplanes, ocean shipping, winter heating.

kpil• 9 years ago

This makes one very discouraged about nuclear power.

Yes, I used to think it can be made safe, but we are just hoping that we will be able to handle the waste later. Then if there will be a 100.000 year accident every 10-15 years, it will be a rather depressing future...

I think that solar must be the way to do it. If we can't make do with solar, we won't be able to sustain the current population size.

coldtea• 9 years ago

So, what's the long game with Fukushima? This has been going on for so long and it's concerning that seemingly very little progress has been made.

Long? They are still, to this day, trying to bury and isolate Chernobyl's reactors.

static_noise2• 9 years ago

Somehow it seems strange that Japan, the motherland of robots, fails to build a robot.

Money can't be the reason. There has been an investment surge into radioactive cleanup technology starting with the damaged reactors six years ago.

Six years and billions of dollars later we get a robot that gets stuck and fails after just two hours. From what I've gathered they didn't even include a proper radiation sensor but used the camera noise in order to "guesstimate" the dosage after the fact. Did they not expect high radiation in that location?

Pica_soO3• 9 years ago

Electronics of the shelve get very unreliable in high dosage environments. The radiation rewrites your loaded programs, by flipping bits and causing rising edges where there shouldn't be some.

So the program running on your camera will dissolve above some radiation levels, locking it in a watchdog detects and reboot cycle. There are approaches to circumvent that in low to medium environment- one is to have redundant systems and select the "majority" vote on computation results.

But at this level, the only solution is to not have computation near the source and put up with long cable/fibre cable delay- which is tough with complex sensors (aka computers) like cameras.

It is probably some snail-eye setup- the camera a remote mini-drone on cable, retracted on black out.

static_noise2• 9 years ago

Does that mean you cannot use robots, nor can you use humans, to clean up this mess? What do you do then?

cnvogel2• 9 years ago

In my day-job, I (help) design electronics that is subjected to (much less) radiation, and we also irradiate our devices to check for long-term effects (and this is done with a comparable doserate in a facility for this purpose).

Damage to your electronics in practice is almost exclusively caused by Photons (convention is to call this γ-Radiation when caused by radioactive decay in the nucleus, X-Rays when created in an accelerator). β-radiation (fast electrons) is easily shielded by thin layers of metal, and α (He nuclei) can't penetrate sheets of paper.

Individual photons can't really deposit much energy at a single location in your semiconductor, so they aren't able to generate enough charge to "flip bits" instantly. Flash still uses a lot of charge/bit, so it's relatively stable, DRAM is constantly refreshed and SRAM would need a jolt of high current to flip, so that does not really happen, either.

What radiation does, however, is to slowly damage the Silicon and change its crystal structure (introducing defects) which increases leakage and moves the analog threshold voltages of circuits around in a funny way. So, what we often see is flash becoming un-programmable on a more global scale (rather than individual stuck bits), and most importantly the analog aspects (voltage references, brownout-protection circuits, voltage regulators) cease to function.

This is all very variable, but we normally observe effects starting at "a few 100 Gy" when testing more complicated modules. We don't research individual components, though.

One especially nasty type or radiation are neutrons, though. When being "moderated" (slowly decelerated by successive interactions with material) they tend to have a high likelihood of merging with some other nucleus (being captured), and the energy resulting from this capture effect can be huge and concentrated on a single spot. This can be enough to flip bits, and this indeed may be an issue near the funny isotope mixture present in Fokushima at various places. Having a strong neutron emitter is very uncommon, though.

Unfortunately these damages are not specific to digital electronics, and especially optical components (parent refers to long fibre cables) tend to be rather sensitive due to their large structures, so "keeping the computers out" may not help much overall.

throwanem4• 9 years ago

Radiation-hardening electronics is not simple, and this robot was rated for 1000Sv cumulative, which is something of an accomplishment even if it wasn't enough for the environment here.

The article also absurdly understates what an activity level like 650Sv/h actually means. It "could kill a person quickly", the article says, as though the question were open - the truth of the matter is that such heavy irradiation will kill an unprotected human in a matter of seconds, a few minutes at most. As for protected humans, good luck wearing thick enough and dense enough armor to make a meaningful difference under that kind of bombardment - and if you do manage to find it and wear it, good luck not suffocating or being crushed outright under its weight.

This should, I hope, put in some more accurate perspective the fact that the robot lasted a couple of hours. It doesn't sound like much, and isn't - but it's vastly better than anything else we've got.

It should also, I hope, put paid to a sibling commenter's rather hideous suggestion of using Chernobyl-style "bio-robot" "liquidators" to deal with the aftermath. The only way that might possibly work would be by insulating the active slag under a thick layer of quite dead and half-cooked human bodies - a very Soviet suggestion, perhaps, but nothing to be seriously suggested by anyone who values even the pretense of civilized humanity.

pdkl95• 9 years ago

Chernobyl-style "bio-robot" "liquidators"

Anybody that isn't familiar with the "liquidators" should watch Chernobyl 3828, a Ukrainian documentary about the cleanup of the worst part of the roof with comments by the people currently working their two-minute shifts as a "bio-robot".

http://www.telecon.kiev.ua/eng/projects/chernobyl_3828.html

https://www.youtube.com/watch?v=FfDa8tR25dk

codecamper2• 9 years ago

Could a future earthquake jolt the reactor back into danger mode?

u_wot_m8• 9 years ago

It's still in danger mode, still leaking massive amounts of radiation into the pacific ocean. Based on what I've read of dying ocean life it's probably one of the worst environmental disasters in history

dabeeeenster• 9 years ago

Do you have a source?

e40• 9 years ago

Not according to the recent Nova I watched on the subject.

tptacek3• 9 years ago

Reprising:

There are 187000000000000 million gallons of water in the Pacific Ocean, meaning that "radioactive waste" is 2.1 x 10^-10% of the body of water itself. The waste takes the form of HTO, tritiated water, which has extremely low bioavailability and has already been introduced in abundance to the ocean by other events. There are things to be alarmed about, but this isn't one of them.

choonway2• 9 years ago

Are there any startup robotic companies that are doing robots that can deal with hard radiation? It seems that they are trying to wash off some melted gunk that is blocking their way into the area beneath the vessel where the core is suspected to be.

Will building a robot capable of completing such a task under such an environment attract any funding? Anywhere to apply?

dottedmag• 9 years ago

One can arguably find the engineers who created robots used in Chernobyl, which were oblivious to radiation by using pneumatic tubing for control.

amelius• 9 years ago

I'm wondering, can't they use the radiation as an alternative to light (photons), in that environment? I'm guessing the radiation would scatter in a way comparable to light, so you would be able to get a similar kind of "imaging". Not sure how one would implement a radiation detector in silicon, but at least you could shield it by some layer of metal to get out of the range of overload and into the range of sensitivity.

the8472• 9 years ago

High energy photons are quite different compared to visible light. They scatter instead of being reflected. They have a low cross-section which means you can't make tiny pixels. No reflection or diffraction means no optics.

High radiation readings at Fukushima’s No. 2 reactor complicate robot probe

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