I don't understand how "each robot has to be custom built for each building" and "takes two years to build".
I mean, they don't need Atlas here. They just need a ruggedized remote control car with a camera and a ton of lead plate on it.
I mean, they don't need Atlas here. They just need a ruggedized remote control car with a camera and a ton of lead plate on it.
We do build mock facilities and we have recently started working on the Fukushima Daiichi inspections, and there is only so much I can actually say but I'll share what I can. I'll explain what caused the failure in this part and then I'll move onto the fun stuff in the next post (robots!).
In the past, the mock facilities we have made in the past were a quarter of a full scale reactor, rather than a quarter scale reactor, if that makes any sense at all.
Anyway back to Japan. I'm assuming people have a basic understanding of how fission reactors work (Boiling Water Reactors if you are interested in doing further reading).
To break the situation down, the cooling failed (believe it or not, diesel generators don't work too well on water!) on reactors 1, 2 and 3, causing a complete meltdown of the fuel rods. When cooling failed, all of the cooling water was turned into steam, which in turn reacted with the released radioactive isotopes creating hydrogen. I'm assuming people know mixing hydrogen with oxygen is basically a recipe for an explosion, and that is important for what happened next. They tried to vent the gases out to the atmosphere to prevent the pressure vessel from exploding, but the hydrogen went the wrong way and caused reactors 1 through to 3 to explode in various places. I can't remember correctly (I think its reactor 3?) but the explosion happened within the pressure vessel which is why there was a large contamination breach. Because of this complete loss of control of the reactors, and the meltdown currently happening, they flooded the whole system with sea water and pumped as much out into storage as they can, but they lose a lot of it out to the sea, hence the Americans whining about the radiation in the Pacific. Now, the reactors are stable (ish) and they are continuing to pump water in to stop them going critical again.
I'll move onto the robots when I get home in part two, but right now I need to go have an argument with a lawn mower as my hair is getting unruly. The video linked below explains more about the actual failure of the reactor:- https://www.youtube.com/watch?v=JMaEjEWL6PU
Brb.
AFAIK, fukushima was actually a very small "disaster", with negligigle human life loss (if I recall correctly, no life loss, except due to the evacuation panic)
Would you, in conscience, turn back on a series of nuclear reactors that had their emergency backup generators located in an area that can easily be flooded?
There are a lot of other human/social aspects involved as well.
It's better to apply the lessons learned from Fukushima to a safer type of reactor, built better, designed safer, and operated with a different set of procedures and by a different company (not TEPCO, for example).
1) in the past the mocks was just a subset portion of the reactor (ie the quarter that is relevant to operations)
Hopefully I didn't mangle your words, but this is how I understood your phrasing.
In terms of Fukushima, the manipulator we are developing will eventually have a testing rig built for it, however we have only just been involved on the project in the last month and as such haven't reached a stage where we need to build the rig yet. With the Japanese government funding though I imagine it will be a similar job with a scale rig.
So, ROVs.
We probably aren't going to use a ROV for our solution as it doesn't suit and they're a pain in the arse quite frankly.
To start, I'll address the issue with the 'wires' failing. An American company built a ROV that was heavily shielded and was driven via an umbilical. Wireless is hard to use and autonomy is too hard to use as the reactor conditions are unknown. The ROV was a good design and could survive the radiation for a reasonable amount of time, however for whatever reason they used PVC wire sheathes that break down under heavy radiation, and as a result the wires touched and shorted the electronics out, rendering the ROV useless and 'dead'.
In terms of why it takes so long and why we can't use an off the shelf version, basically radiation is a bitch. At the base of the reactor vessel, just above the corium, the radiation output is estimated to be around 3000 microsieverts per hour, that translates roughly to a human life expectancy of around 6 seconds, give or take. This amount of radiation causes electronics to fail (transistors commonly), and materials to break down. The breaking down of materials caused the American ROV to die, and another example would be that it can causes greases to harden, which stops motors working.
Reactors aren't big spacious areas either, so it's not like we can just deploy a lead (lead weighs a metric shit'tonne) shielded tank to have a look, it's just too big and cumbersome. We decided against using a ROV as it had to be 30kg or less, which is absolutely nothing once you bring in drilling packages and the likes.
Also quite often you will be deploying through a hole between the size of your fist up to just smaller than the diameter of your head, so that restricts you hugely as well.
You also have material compatability. If you get something stuck you have to be sure that it won't react and cause the reactor to become critical again, which could happen in one of the reactors (can't go into more detail sorry).
One last major consideration as too why it takes so long to build and test a ROV to suit. The reactors are under immense thermal stress, and metal likes to bend and warp when it's heating/cooling. You have to build your solution around the worst case scenario. An example would be we went into a boiler tube trying to plug a 1 inch hole from 18m above it using a manipulator arm. That's already hard on its own, but then we discovered the originally 7mm gap we were aiming for was actually now as small as 3.5mm. Trying to develop ROVs and remote solutions is really not easy, the best way I can put it is that this line of work is an art, not a science. That's why it will probably take the best part of a century I reckon to fix this problem.
That's why it will probably take the best part of a century I reckon to fix
this problem.
But a question -- you say you won't use a ROV. But you say wireless is hard and autonomy is too hard. So that leaves what?
And thanks for taking the time to share.
Also we are going to use a manipulator arm more than likely. Manipulator arms are cheaper and more widely used in our industry.
Your idea would be perfect if we were just doing an inspection, however we have other work we will need to do down there which will require various packages so it has to be somewhat bulkier.
3000 microsieverts (3 milisieverts) is most definitely not fatal, as it is similar to the yearly exposure.
Sorry?
It's a complex process. They can't risk creating a situation worse than before, and nuclear facilities are pretty sensitive.
They usually create 1/4 scale models of the buildings they'll be working with for testing, etc. - it's a big deal.
robots, which can swim under water and negotiate obstacles in damaged tunnels and piping to search for the melted fuel rods.
to find and remove the extremely dangerous blobs of melted fuel rods, weighing hundreds of tonnes
You don't need a hundred-tonne robot to find a fuel rod, so they can at least get that part sorted. Once they know where they are, build something super rugged (I'm thinking basically a remote controlled shielded fork lift) to do the lifting.
Certainly if the answer was actually as simple as "buy this off the shelf thing" then all the smart people over there would've figured that out at some point in the last 3 years.
The Fukushima reactor was built to withstand a huge amount of risk factors, they just all happened at the same time. The risk mitigation concept would be to say that you need to design a house to withstand a 10,000 year storm.
There are gases circulating around, free hydrogen gas, volatile gases that could explode if exposed to a spark - so the robot has to be built to not spark or have inert mechanisms for turning, moving, etc.
Parts are submerged, so this robot needs to be water tight to irradiated water and have some mechanism of moving when submerged (buoyancy control).
Radiation is the highest danger to electronics, it's said that all the wires degrade, all the parts of the robot steadily break down when trying to get inside. The chips and control circuitry needs to be radiation hardened, and I bet the "wires" the article refers to means servo control wires - which needs to be linked to servos that are on the limbs - so it's harder to shield. (whereas control chips, the cpu, etc can be shielded by lead plates in a central location)