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Excessive Radiation Inside Fukushima Fries Clean-Up Robot (gizmodo.com)
"A remotely-controlled robot sent to inspect and clean a damaged reactor at Japan's Fukushima nuclear plant had to be pulled early when its onboard camera went dark, the result of excess radiation," reports Gizmodo. "The abbreviated mission suggests that radiation levels inside the reactor are even higher than was reported last week -- and that robots are going to have a hell of a time cleaning this mess up." From the report: Last week, Gizmodo reported that radiation levels inside the containment vessel of reactor No. 2 at Fukushima reached a jaw-dropping 530 sieverts per hour, a level high enough to kill a human within seconds. Some Japanese government officials questioned the reading because Tokyo Electric Power Company Holding (TEPCO) calculated it by looking at camera interference on the robot sent in to investigate, rather than measuring it directly with a geiger counter or dosimeter. It now appears that this initial estimate may have been too low. Either that, or TEPCO's robot is getting closer to the melted fuel -- which is very likely. High radiation readings near any of the used fuel are to be expected. Yesterday, that same remotely operated robot had to be pulled when its camera began to fail after just two hours of exposure to the radiation inside the damaged reactor. Accordingly, TEPCO has revised its estimate to about 650 sieverts per hour, which is 120 more sieverts than what was calculated late last month (although the new estimate comes with a 30 percent margin of error). The robot is designed to withstand about 1,000 accumulated sieverts, which given the failure after two hours, jibes well with the camera interference. This likely means that the melted fuel burned through its pressure vessel during the meltdown in March of 2011, and is sitting somewhere nearby.
In this case the "radiation" is the emission of high-energy neutron particles. Neutrons will run into anything *... and when they do, they transfer a ton of their energy into whatever they hit... causing "damage cascades" as atoms get tossed around (Wikipedia has a decent animation here: https://en.wikipedia.org/wiki/... ).
That atom-scale damage adds up after a while... causing material failure... regardless of the type of material.
For instance, inside of a reactor all of the steel holding all of the fuel in place is constantly bombarded... leading to all sorts of effects like radiation induced swelling and embrittlement.
In humans the primary issue is when those neutrons hit DNA / cells and damage them. It actually happens to us all day long from radiation around us... but our bodies can deal with a certain amount. Too much damage though... and your body can't cope any more.
In robots / electronics the issue is much the same. The neutrons run into _everything_ and degrade it. More sensitive pieces (like camera sensors) will degrade rather quickly while larger components (like structural steel) will most likely be fine for long periods of time.
* The probability that a neutron will hit a certain type of atom is called a "cross section" (XS) and is an _extremely_ well studied phenomenon. You can look at some here: https://www.nndc.bnl.gov/sigma... for instance, this is the probability for a neutron running into Hydrogen: https://www.nndc.bnl.gov/sigma...
At those intensities, measuring things becomes very hard. Geiger counters only work up to pretty low radiation rates. Dosimeters need exceptionally heavy shielding to not immediately go black in the conditions there. Actually seeing how long the camera lives may be the best currently available method that fits on a robot.
Humanity has basically no experience with radiation levels this high.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
Gamma rays break down the crystalline structure of things like the chips. Even low-level radiation will wash out a camera, but about 10-25Sv for "long" periods of time will have some effect, 650Sv pretty much instantly destroys everything, even things like the metal the robot is constructed out of will eventually become harder and more brittle as the atoms get knocked out of the structure (eg. if someone suggested pneumatics, plastic, rubber and metals would also deteriorate).
Custom electronics and digital signage for your business: www.evcircuits.com
https://en.m.wikipedia.org/wiki/Radiation_effects_on_optical_fibers
+1. What aircraft are exposed to are mostly gammas and a few heavy ions, not neutrons (alongside massive amounts of gammas as well). There's nothing close to neutrons in terms of causing damage, they'll penetrate almost anything and then activate it so you get the whole mix, alphas, betas, and gammas inside the sensitive devices that you're trying to protect. You can make electronics that's somewhat resistant to radiation, but it can't do much against neutrons. In any case all the rad-hard stuff is designed for space/military use, and that's gammas, not neutrons (and accompanying alpha, beta, and gamma).
There really isn't any easy way to do this. One approach I guess would be to have all the control electronics a long way from the robot and only basic actuators and sensors on the robot itself. However, video is still control electronics...
Strange to say, some older microprocessors are more resistant to radiation. The components in modern microprocessors are much more tightly packed and a gamma ray is more likely to hit something critical. This is why NASA uses special microprocessors that are less densely packed and thus more resistant to the radiation in deep space. Sounds to me that they might want to consult with NASA about how to deal with radiation.
The NASA special microprocessors are old 8086, 80386, etc and not so special. The drawback is computing speed and features. They still won't work close to a hot neutron source.
In other words Yes folks, the fuel is indeed outside of the reactor core.
Let's, for a moment, consider what words were spoken inside the TEPCO media relations meeting;
This is exactly the kind of slimy trick the Nuclear Industry PR would use to downplay evidence of fuel being outside of the reactor, maybe I've been napping however I've not seen the headline Evidence of Nuclear Fuel Found outside of Fukushima Reactor Core anywhere. I'm just supposed to be comfortable that it's inside the containment as if it's no big deal that it didn't melt *INSIDE* the reactor where it should be.
M: Susan, make sure the by-story runs that it is *inside* the containment, we need to make sure the fans have a counter argument. People, we're running with the robot broken down story and that we think it might have kinda possibly run into a tad bit of radio stuff,, we have to get on top of this before the mainstream get a hold of the news. Susan, where are those overalls!
This article from the Japanese daily contains the video feed from the robot. Above the hole you can see the base of the reactor pressure vessel. Your statement seems a trite summation considering the evidence discovered.
It's perfectly reasonable to be angry about the incompetence that led to this disaster, what's weird is trying to say it's no big deal. The international community who shares the coasts of the pacific ocean will suffer the consequences of this over a very long time. This is what a big deal is.
I don't see any justification for supporters of nuclear energy to play the same morally superior dogmatically skeptic attitude they have had over the last decade anymore, this is an INES7 scale accident. Information is available now, and people can read so what need is less downplaying so we can figure out the nature of the mess the nuclear industry has left us and where these 3 cores are.
Evidence of reactor fuel found outside of the Fukushima reactor is the information and the nuclear industry is very carefully avoiding any further criticism.
My ism, it's full of beliefs.
530 sieverts per hour is an insane level of radiation.
Since 1 Sv = 100 rem, we're talking about 53,000 REM per hour, a level that would indeed kill you dead in under a minute.
For scale and comparison, the average dental x-ray image exposes you to only about 2 or 3 millirem.
So....530 sieverts per hour is like getting ~26,500,000 dental x-rays in an hour.
Just cruising through this digital world at 33 1/3 rpm...
Your non-chalant attitude about radioactivity downplays the risks
It does not. It *compares* them. And nuclear power has been responsible for far less death and suffering even if we include Chernobyl. Without Chernobyl, we're deep into 'more people have been killed by pillow fights' territory.
A meltdown and loss of control can cause it to spread wide as it has with Fukushima.
And Fukushima has been a *financial* catastrophe. It has not been a public health one compared to the other risks we accept all the time with fossil fuels.
Radioactivity has toxicity properties in its own class
Just pure white noise. I understand that sentences like these (which are being posted by many people, not just you) are meant to be persuasive, but it's just a complete non-starter. I don't care if it's different. Toxic heavy metals can be terrifying enough, thanks. "Different" doesn't matter. Severity does. And the numbers I've seen show pretty convincingly that nuclear isn't nearly as bad.