Reference, Questions and Help > Nuke Q&A

Blue Fuel Cells

(1/4) > >>

sefrick:
OK, I was not the strongest on nuclear physics, I was more like to grunt that knew how to rig the main condenser manhole cover off in less than 10 minutes or turn the cooldown knocker valves the fastest, but anyway, Beer Court had me look at some pictures posted on this site. I'm curious what causes the fuel cells to glow blue. Also I'm wonding about outages. I know, from what Beer Court posted that cell replacement is frequent, but what about decay heat, exposure etc. I decommissioned my first boat which required removing the fuel cells. I don't remember what the mechanism was called that lifted the cells out, but I remember that it took about 3 hours per fuel cell and the basics on how it worked. I'm wondering how it is done in a commercial plant and where the "spent" cells are transported or stored. And how the heck where those pictures taken???

Sorry guys, even though I was the M-Div grunt, I always wanted to know EVERYTHING.

Already Gone:
Okay, let's start with the blue color.  It is the result of something called the Cerenkov Effect.  It's been a long time since I've studied this, so I can't be very technical.  Essentially, the blue light is the emitted radiation from Beta particles rapidly slowing to sub-light velocity.  The speed of light in water is much slower than the speed of light in air or in a vacuum (c, as in E=mc2, is speed of light in a vacuum).  Anyway, this means that it is possible for a particle to exceed the speed of light in water.  As the particle loses kinetic energy, part of that energy is converted to visible light.  Due to the wavelength of the light, it is always the same color of blue.
The longer a bundle has been in the core, it will accumulate more beta-emitting fission products.  As the bundle sits in the fuel pool for a long time, the fission products decay away, as does the intensity of the blue glow.

Now, if you look at more of those pictures, you will notice that the reactor head is removed.  The flange at the top of the vessel is at the botom of a cavity which is flooded with water.  The bridge which travels over the cavity has a manipulator crane that lifts the assemblies out of the vessel and transports them to the Spent Fuel Pool.  In a PWR, this takes two cranes and a shuttle, which moves the bundle through a tube that connects the reactor cavity ant the SFP.  In a BWR, the SFP and cavity are next to each other, and it only takes one manipulator to move the fuel between them.

It takes and average af around 10 to 30 minutes to complete a move of one bundle.  If all the machinery is working well, and the bundles are cooperating, it is closer to 10 than 30.  It is also faster to shuffle a bundle from one place in the core than it is to remove one and replace it.  The average refuelling outage requires the replacement of around 100 bundles.  But, sometimes all the fuel has to be totally offloaded and then reloaded, depanding on what maintenance and inspections are being done.

The fuel is visible because the water in the cavity is about 25 feet deep.  The SFP is about 40 feet deep, with at least 25 feet to the top of the fuel.  You don't want to see one of those out of the water, you'd never live to talk about it.

Due to decay heat, the bundles have to stay in the Spent Fuel Pool for about ten years, before they can be loaded into shipping containers for final storage.  Due to political reasons, they have to wait until the second coming of Christ before there is going to be a place to put them for final storage.  Lots of sites have temporary facilities to store the casks until that happens.

sefrick:
That' s heavy, I knew you would be the one to reply. I became very curious after I peeked at the pictures on this site. The cells appeared to be dry and I was wondeing how on earth that was possible, that was my main question. I'll try to look up some info on the Cerenkov Effect.Thanks

sefrick:
OK, I've convinced that you can find anything on the net these days...the following was found as a result of a web search for cerenkov effect; good stuff.

http://www.nightscribe.com/Science_Technology/Nuclear/db_rx_cerenkov1.htm

...and I thought the blue water in K-19 was hollywood hype!

Tina:
 :) OK Beer Court...

Maybe I missed something in your explination, but I have a question now  ;)

I've seen fuel rod manipulations in progress and watched the pretty blue glow and crane work here at Clinton Power Station...  :) I've seen the long boxes that fuel rods come in for delivery and shippments.  :) So I guess my question is How do the fuel rod bundles get pulled and placed in these boxes for shippment I thought they stayed in the cool pool like you previously said for an awful long time.  ::)  but for the sake of argument... lets say it their time to be shipped  now how dose a fuel rod bundle get from being lifted by crane through the water and placed in a box/cask  ::) I do realize that they are bundles of fuel rods , not just single rods being transfered... ;)

I luv it when an intellegent speaks  ;)
 : 8)

Navigation

[0] Message Index

[#] Next page