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Robotics Japan

A Robot Will Soon Try To Remove Melted Nuclear Fuel From Japan's Destroyed Fukushima Reactor (apnews.com) 56

Tokyo Electric Power Company Holdings (TEPCO) showcased a remote-controlled robot on Tuesday that will retrieve small pieces of melted fuel debris from the damaged Fukushima Daiichi nuclear power plant later this year. The robot, developed by Mitsubishi Heavy Industries, features an extendable pipe and tongs capable of picking up granule-sized debris. TEPCO plans to remove less than 3 grams of debris during the test at the No. 2 reactor, marking the first such operation since the 2011 meltdown caused by a magnitude 9.0 earthquake and tsunami. The removal of the estimated 880 tons of highly radioactive melted fuel from the three damaged reactors is crucial for the plant's decommissioning, which critics say may take longer than the government's 30-40 year target.
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A Robot Will Soon Try To Remove Melted Nuclear Fuel From Japan's Destroyed Fukushima Reactor

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  • 880 tons sounds like an awful lot of nuclear fuel. My understanding is that the amount of fuel used in reactors is much smaller. I wonder if that number is for radioactive debris.
    • Re:880 tons? (Score:5, Informative)

      by 93 Escort Wagon ( 326346 ) on Tuesday May 28, 2024 @02:58PM (#64506089)

      Given the fuel melted down, I'd expect there's a fair bit of fuel-contaminated material that will also need to be collected.

      On a side note - the headline sucks. It reads as if the robot is making autonomous decisions, when what's really happening is a dumb remote unit is being controlled by humans to perform work in a hostile environment.

      • by belmolis ( 702863 ) <billposer@@@alum...mit...edu> on Tuesday May 28, 2024 @03:05PM (#64506105) Homepage
        Exactly. So it isn't 880 tons of fuel - it is 880 tons of radioactive stuff, mostly other things contaminated by fuel.
      • Re: (Score:3, Interesting)

        by AmiMoJo ( 196126 )

        Yep, there are hundreds of tons of corium down there.

        It's an unsolved and massive problem. Trying to break it up risks spreading contaminated dust everywhere. It's bad enough already, when you consider that the robot has to put the waste in some kind of container, and that container then needs to be decontaminated with large amounts of water and chemical agents. They are having to invent new techniques as they go, because unlike Chernobyl they are not willing to just encase it and leave it indefinitely. Asi

        • by sfcat ( 872532 )
          Wrong again. A normal fuel load in a reactor is about 10 tonnes. The 800 tonnes figure comes from the weight of the entire reactor and containment vessel. Once the core is removed, the rest will decay to stable in about 10 years.
          • by AmiMoJo ( 196126 )

            The containment vessels failed. Units 1 and 2 are confirmed to have failed and the fuel melted down into the concrete below.

            The cores can't be removed because they are no longer in the vessel, and are now the shape of a melted lump of slag mixed with concrete and various other parts of the containment building.

      • On a side note - the headline sucks. It reads as if the robot is making autonomous decisions, when what's really happening is a dumb remote unit is being controlled by humans to perform work in a hostile environment.

        On that side note, I was left questioning if Japan was going to “succeed” like the Russians did with a robot at Chernobyl.

        It’s most definitely a dumb robot. Anyone reading more into that headline, has been hitting the AI bong a little too hard.

    • They may be including spent fuel in the cooling pools that evaporated off cooling water without sufficient coolant flow and partially melted, causing the hydrogen explosions.

      • Re:880 tons? (Score:5, Informative)

        by DamnOregonian ( 963763 ) on Tuesday May 28, 2024 @03:43PM (#64506205)
        They might be, but it doesn't sound like it.
        Reactors 1-3 contained 1496 fuel assemblies, at about 500kg each. That's 748t (metric) or 822t (US)
        It's not far from either, and the rest can probably be accounted for by the fact that those fuel assemblies turned into slag, and took the internals of the reactor with them.
        • by sfcat ( 872532 )
          None of that seemed off to you? What you did (just so you know) is include the fuel rods in the spent fuel pools in the calculation. Those did not meltdown. A normal reactor in the west has 157 fuel assemblies. A normal fuel load in a reactor is about 10 tonnes but can vary depending on how the reactor is engineered. This is a pretty old plant and design so it probably has more like 15 tonnes of fuel per reactor. The rest are in spent fuel ponds cooling normally.
          • is include the fuel rods in the spent fuel pools in the calculation.

            Incorrect.
            I grabbed the number of active fuel assemblines in each reactor, which was separate from the spent.
            All 3 reactors were fully loaded at the time of meltdown.
            Reactor 1 holds 400 fuel assembles, reactors 2 and 3 hold 548.

            A normal fuel load in a reactor is about 10 tonnes but can vary depending on how the reactor is engineered.

            Reactor 1 holds 69t (metric) of uranium, Reactors 2 and 3 hold 94t.
            However, that's just the uranium. The total weight of each assembly is about 500kg. Since the uranium and the fuel assembly melt into a single blob of corium, when they're referring to fuel, they're referring to t

    • A single BWR usually contains about 127 tons of nuclear fuel.
      It's "a lot less", but it's still a fucking shitload.
      I'm guessing the 880 comes from the fact that when fuel melts down, it's also hotter than *everything* around it, and everything melts into it (Corium)
      • Also- keep in mind we're talking 3 reactors, so ~400t of melted fuel, without including anything it may have collected as it melted down.
      • Further revision- it appears these had significantly more fuel in them than is normally stated as "normal" (or more likely, there are strong caveats to normal).
        880 is actually pretty damn close to what would be expected for the fuel assemblies of all 3 reactors, and some extra goodies (reactor internals) that are now not physically separable from the fuel.
    • It is and it isn't. Remember that nuclear fuel is super dense/heavy. It weighs a lot but is significantly less volume-wise than you imagine. For example, 880 tons of Uranium is only 46.2 cubic meters in volume.

  • The video shows a really amateuristic grabber which dangles over the debris like a grabber in an arcade hall. Is that what they came up with for millions of dollars?
    • I'd imagine the biggest challenge is building things that can survive that level of radiation.

      • by PPH ( 736903 )

        ShopVac

      • Yeah, the video shows two similar grasping actuators mounted to two different carriers, one hanging vertically and the other a diagonal beam-like shaft. I'm assuming that it is really hard to make an actuator that won't just fail from radiation within minutes of getting close enough to pick up corium. It looks like there is a light and a camera, and the actuator must need to be almost entirely mechanical (no motors). It looks like the whole thing might be pneumatic. Also it might be that the small size
        • What makes you think anything about radiation will harm a motor? A motor is nothing but ball bearings, iron and copper windings.

          It would certainly harm an electronic commutator, but fortunately there's an ancient technology called a brushed commutator that doesn't have that problem.
          • by necro81 ( 917438 )

            It would certainly harm an electronic commutator, but fortunately there's an ancient technology called a brushed commutator that doesn't have that problem.

            A motor spinning without any sort of position/velocity feedback is pretty worthless for robotics.

            • Then GP should've said "servo." For angular or linear position feedback, one may use an LVDT, or a simple limit switch. Or go with stepper motors and trust that it won't slip a step, which works quite adequately if you don't need high speed. All the while, the electronics can hide inside their lead shielding brick.

              Just because we're accustomed to all the sensors and drivers being electronified, doesn't mean it wasn't possible to make things happen before every possible sensor and actuator device had its
        • Actually, I think the camera is the first thing to go. Here is one reference. https://www.cbc.ca/radio/quirk... [www.cbc.ca] Another reference https://www.theguardian.com/wo... [theguardian.com] mentions the rad level in at least part of the plant is 650 sieverts/hr, apparently deadly to people in about 1 minute.
    • 'The video shows a really amateuristic grabber which dangles over the debris like a grabber in an arcade hall. Is that what they came up with for millions of dollars?'

      It can't be expensive, otherwise they would have to raise the price of electricity for their customers. :-)

  • by CaptainDork ( 3678879 ) on Tuesday May 28, 2024 @03:29PM (#64506159)

    A nickel weighs 5 grams. So, removing 880 tons of highly radioactive melted fuel at a rate of 3 grams every 5 minutes would take approximately 2,790 years.

    I pulled the 3 grams every 5 minutes out of my ass, but they need to scale up.

    • by AmiMoJo ( 196126 )

      They will probably just remove the high level waste from around the reactor, and then look at encasing the rest forever. Unless someone invents new technology to break up and remove the hundreds of tons of melted cores safely somehow, only to bury them somewhere else forever, there isn't really any other option.

      • by sfcat ( 872532 )
        Why do you post on topics you know nothing about. Once the core material is removed, the rest decays to stable in about 10 years. This is because almost all isotopes and all of the isotopes of metals used in a nuclear reactor have half-lives measured in less than a year. You know you can look this stuff up yourself right. The only thing keeping the (non-core parts of the) reactor radioactive right now is the neutron flux the core is causing.
        • by AmiMoJo ( 196126 )

          They can't remove the core material. It melted down, left the containment vessel, and mixed with parts of the containment building. It's all just a huge pile of corium now.

        • The melted fuel debris at the Fukushima Daiichi nuclear plant contains a mixture of various radioactive isotopes with different half-lives. Here are some of the major isotopes and their respective half-lives:

          Cesium-137 (Cs-137): Half-life of around 30 years
          Strontium-90 (Sr-90): Half-life of around 29 years
          Plutonium-239 (Pu-239): Half-life of 24,100 years
          Plutonium-240 (Pu-240): Half-life of 6,561 years
          Uranium-235 (U-235): Half-life of 703.8 million years
          Uranium-238 (U-238): Half-life of 4.47 billion years

          The

  • I know these items are dense. But couldn't they seal off the area and pump air in one side and vacuum it up the other to collect the tiny particles ? Picking them up with tongs sounds like it would irradiate a lot of sensitive electronics.

    • A good bit of the really REALLY nasty stuff is gone already. That's not saying there aren't still dangerously high levels, but the levels will be dropping every unit of time from the accident on. That's why the elephants foot can now be approached by robot, and if I recall correctly brief human exposure is allowable near the corner it is around. That said, the dust would be, and IS a massive concern. As it would all be radioactive to at least some extent, and would easily get into lungs of anyone downwind.

  • by Required Snark ( 1702878 ) on Tuesday May 28, 2024 @06:13PM (#64506503)
    Or how much it will cost. Or how they will really do it. They're just making things up while they kick the can down the road.

    It's on the same path as the Hanford Site cleanup. [wikipedia.org] That was started in 1988 and was supposed to take thirty years. In 2008 it was supposed to be done in 2040.

    They still haven't moved all the waste into secure storage. Both the old original single wall and new double walled tanks keep springing leaks. The fact that some material hasn't been moved from the old tanks since the 1990's is staggering.

    The plan was to encapsulate the high level waste in vitreous logs. So far no high level waste has been processed at all, and they only have a limited ability to vitrify low level waste. High level waste consolidation has no current viable plan and not even a target start date. The single shell (original) tanks have a supposed closing date of 2043(!) and newer double shell tanks have a close date of 2069(!!), over 80 years after the project started. [crosscut.com]

    So moving 3 grams of non-radioactive material at a test location and claiming it's real progress is totally normal for nuclear melt-down cleanup efforts.

    • I used to do service work at Hanford (Westinghouse Hanford Co back then) and everything to do with nuclear materials takes a long time to do. It would take those guys an hour and a half to watch "60 Minutes". ;)

      Seriously though, all the SWP (special work procedures) stuff takes forever to go through the 3-step "prepare, perform, and put-away" process.

      Prepping (for exposure) and performing (the work) could take a while for sure, but the put-away phase is where the hours and days can disappear into a black ho

      • My point is that if they tell you "20 or 30 years", expect it to never be done- they're just kicking that radioactive can down the road as slowly as possible, hoping to hit retirement before the glowing waste-poop hits the rapidly-spinning impeller. Ask me how I know...

        Because this is how your generation dealt with CO2 emissions, which are actually much more harmful than that radioactive can?

        • Sorry if the facts make your tummy hurt, but your generation is doing the exact same thing with a slew of problems- problems that your generation could be solving, but that you're obviously choose not to. Why is that, why aren't you doing anything?

          Maybe if your generation wasn't so lazy you could put down your avocado toast for a moment and start solving the world's problems, how about that? Stop being a slacker, get out there and solve those problems.

          (See how easy it is to blame an entire generation for s

          • None of the people of the generation which you are currently deriding are in any office that could change anything. The average age of US rep is 58. The average age of US citizen is 38.
            • None of the people of the generation which you are currently deriding are in any office that could change anything.

              Bullshit.

              There are loads of people in that age range who can do something, but like you, they won't get off their asses. (Pretty much the same thing you said about "my" generation, huh?)

              That's right buttercup, the world sucks. Why don't you stop whining and do something about it instead of blaming everyone who came before you? Or would that cut into your Bumble/Hinge/TikTok time?

              • Why don't you stop whining and do something about it instead of blaming everyone who came before you?

                1/ I am doing something about it. More than the average person of your or my generation.
                2/ This is not mutually exclusive with looking back at the past, and see which behaviors caused the most harm. Learning from the past is a good way to make the future better.

                I’m deeply sorry if looking at the past makes it seem like we’re blaming your generation for most of the current harm. Actually, no, I’m not sorry at all.

                In other words, grow a pair and own up to your mistakes.

                • In other words, grow a pair and own up to your mistakes.

                  I can't wait until some young person blaming "your generation" for various things (that you had nothing to do with) admonishes you to do the same....regardless of how big a saint you've been, Mr "I'm doing more than the average person of your or my generation".

                  It'll be so sweet that I'll probably have to start an insulin drip.

                  • I can't wait until some young person blaming "your generation" for various things (that you had nothing to do with) admonishes you to do the same..

                    Already happened, and I can point out several significant mistakes made by my generation, and I have no problem acknowledging them. In fact, I think it's crucial to highlight these mistakes so that future generations can learn from them.

                    I also understand the importance of distinguishing between my personal actions, which may be irrelevant in the grand scheme of things, and the actions of my generation as a whole. That's why I usually don't take criticism of my generation as personal attacks. Similarly, my i

          • It seems my comment may have upset you. Perhaps there's an underlying sense of guilt that you haven't acknowledged (yet)?

            I may have misunderstood your initial statement, but it appeared to me that you were proud of "kicking the radioactive can down the road as slowly as possible" (that's how I interpreted your "ask me how I know" comment, though I might have jumped to conclusions).

            If that is indeed the case, it's ironic that you're calling my generation (and me) lazy, especially since I didn't give you any

            • I may have misunderstood your initial statement, but it appeared to me that you were proud of "kicking the radioactive can down the road as slowly as possible"

              You did. I neither had nor have anything to do with the pace of cleanup at Hanford or anywhere else.

              How you morphed "Ask me how I know" into "I'm proud of delaying nuclear waste clean up" is fucking baffling, frankly.

              But listen up: you're in the same exact trap as me, pal, and don't think for a second you're not. A generation or two from now when you start getting blamed for things "your generation" did, then you'll understand. You'll have a weird sense of deja vu about it, but this time you'll be the Bad G

              • A generation or two from now when you start getting blamed for things "your generation" did, then you'll understand.

                My generation is a mess too—I never claimed otherwise. If you read my previous comments, you'll see that I said, "I didn't give you any reason to think so," which isn't the same thing. I'm quite careful with my choice of words. However, this doesn't absolve your generation from its share of the blame. For example, opposition to nuclear energy, which could have mitigated climate change, primarily comes from the generations before mine. Usually, this opposition comes from the same people who believe tha

    • It’s ironic that your post here, was also serving as an answer to your sigs question.

  • Why build a nuclear power plant on top of an earthquake zone?
    • Why build a nuclear power plant on top of an earthquake zone?

      Because Profitable Demand lives within monopoly invoice distance?

      Maybe stop asking questions with obvious answers in a world dominated by Greed N. Corruption.

    • Re: (Score:3, Insightful)

      by MacMann ( 7518492 )

      Why build a nuclear power plant on top of an earthquake zone?

      Because people live in an earthquake zone and they need power.

      The reactors at Fukushima were built to withstand some pretty powerful earthquakes and they went into automatic shutdown once an earthquake was detected. The problem was the tsunami was far beyond what anyone expected to see and so the water tore out power lines and flooded the fuel tanks for the diesel generators. These were old reactors, not built with the same "walk away safe" safety mechanisms of reactors built since the 1980s or so. They

      • I can't imagine spending 25 minutes writing a long winded opinionated dissertation about how you're the only person capable of scaling nuclear power, that literally no one is going to read, ever. But it takes all kinds I guess.

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