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.
I stuck an RO-7 underwater probe into the Cherenkov glow from a freshly removed bundle and got a reading of just over 400,000 R/hr (I cannot vouch for the calibration of the probe, but it was still very impressive) around 6 inches from contact with the bundle — under water, of course. Beer Court had the numbers about right — it varies from half a million R/hr to about 4 Million R/hr estimated dose.
It is estimated that if you put a fresh bundle (right out of the core after its effective lifespan) on the 50 yard line of a football field and you came out from behind a ‘perfect’ shield at the goal line and ran toward the bundle as fast as you could, you would be dead by the time you hit the 30 yard line. If you drove past the bundle on a motorcycle at 60 mph you would not reach the opposite goal line alive. No volunteers for the test run as yet.
As for the fuel storage issue, several plants have built dry storage facilities (Calvert Cliffs has one that is fairly large) and some plants have toyed with storing other plants’ fuel, but I think so far no one is doing it. Imagine how entertaining it would be in the room with the corporate lawyers when that subject comes up…
