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.

Comments

Re:Hard Numbers

[gweihir]

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.

Re:Radiation wrecks robots?

[guruevi]

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).