There's an election going on here in Ontario. I know that because they're putting up the signs today. You won't hear much about nuclear power for a while, since OPG will stay low until the shooting stops.
In a Candu plant, they put all these compressible fuel bundles into a long pressure tube, and there's a whole bunch (I can't remember how many!) of these in a reactor (lots of sites explain the Candu system).
You can see the fuel bundle fits very snuggly into the pressure tube. Through this, they squirt a lot of heavy water. As they approach a critical water velocity, the compressed fuel pellet tubes start to bulge.
Here's when the fun comes. Any slight pressure pulse in the water hits the first fuel bundle and compressed it a little bit more, which causes resistance to the flow. A compression wave starts down the fuel bundle chain, driven by the water flow. When it hits the bottom, it reflects back as tensile pulse (that's what waves do!). A bit of tension has less resistance to the flow.
We have now set up our water laser! The fuel bundles pump up any little chop in the water flow. They will keep pumping up to tremendous levels! The amazing thing about this arrangement is that it tunes to the input, much like the unstable air flow in an organ pipe. Around the fuel bundles are many sections of pipe (headers and feeders) that would love to resonate at certain frequencies, as well as the primary pump itself. The tubes are probably happiest at their fundamental frequency (everything pumping up and down at the lowest frequency), but higher frequencies are possible.
It is this 'positive feedback' mechanism with the tubes that allows the water laser to pump up to such high energies. Now, once on Wikipedia, everybody poo-pooed this, as being totally useless. They said that the simple 2 cent rotary water chopper in a water pressure cleaner, did the same thing! They obviously didn't appreciate the magnificence of a multi-million dollar setup doing the same as a 2 cent part!
The water laser can be tuned to different frequencies! It produces a perfect sinusoid water pulse, instead of square waves! It can be used to destroy fuel bundles! Such a sad waste that this magnificent discovery will forever go unacknowledged, until they make another one in the next Candu plant!