Robot Squeezes Suspected Nuclear Fuel Debris in Fukushima Reactor (theverge.com)

A robot outfitted with remotely controlled pinchers poked at debris that's suspected to contain molten nuclear fuel at the bottom of one of Fukushima's nuclear reactors, World Nuclear News reports. From a report: The poking and prodding is part of the ongoing cleanup effort at Japan's Fukushima Daiichi power plant, the site of a major nuclear accident in 2011. The dextrous robot was dangled into the Unit 2 reactor on February 13th, according to a news release from the plant's operator, Tokyo Electric Power Company (TEPCO). Unit 2 is one of the reactors at the Fukushima Daiichi power plant that overheated after a massive earthquake and tsunami hit Japan in 2011, which caused the reactor core to melt. TEPCO suspects that radioactive fuel may have melted through the bottom of the reactor vessel to fall into the containment structure surrounding it. The company has to find the radioactive debris and figure out how to remove them, so TEPCO has been sending in a series of robots to scout out the reactors. It's a dangerous journey that some of the robots haven't survived.

Comments

Re:What a dumb headline

[dgatwood]

If you're suggesting they can induce criticality by poking debris with a claw, you're dumber than I give you credit for.

Of course you can induce criticality that way. You can hit a small chunk of uranium with a hammer and reach criticality, at least for a moment. U-235 can reach criticality with a mass as small as 780 g under the right circumstances. And the presence of water, potentially with some amount of uranium in solution, greatly raises the risk. Of course, it would only remain critical while compressed, and so such a small criticality event would likely be a risk only to the robots, because it would be small and self-contained.

Perhaps you meant that it cannot cause a nuclear explosion (which requires not just enough material and moderation to sustain a reaction, but also for it to increase exponentially and not burn itself out in a fraction of a second).

Re:whare are all the nuclear apologists?

[MrKaos]

I can live with paying an extra half cent per kWh to cover cleaning up after the occasional disaster every 25 years, in exchange for using a completely carbon-neutral power source which boasts the fewest deaths per amount of power generated. Why exactly are you opposed to it?

The first is that information related to this subject is heavily censored. The information you have provided is from organizations who are restricted in what they are allowed to publish.

Money isn't the main consideration. The impact of a single disaster is. Fukushima was four disasters at once and considering the amount of spent fuel rods stored on the site had the potential to be an extinction level event. It still does as the removal process has stalled with 566 rods remaining in a precarious position in the heavily damaged Unit 3 spent fuel pool. Tepco itself acknowledges this as the most potent risk for a much more serious disaster than the original.

At this point though it is worthwhile to point out that Tepco has removed approximately 1000 spent fuel rods - which is an enormous effort that should be commended, with gratitude to the workers and engineers that continue to risk their lives to eliminate this risk.