I shall continue my story, even though my ad account remains at a pristine zero! After all, I think I'm writing for my own soul, to boost my serotonin levels!
When the Big Company fired up Darlington, something horrible happened. There were tremendous vibrations, and fuel bundles were coming out shattered. I looked at the photos of these things, and was amazed at the stresses that would be involved to do this. On some bundles, the serial number of the adjacent bundle was imprinted perfectly, implying almost explosive shock-like impact!
For some reason, I was enjoying one of my high cycles in the company, and was thrown into the investigation, because of my experience in dynamics, and they were fond of shit-disturbers! They thought there was some sort of resonance involved, and switched the main pumps from a 5 blade impeller, to 7 blades. This had the effect of a dramatic decrease in vibrations, and broken fuel bundles. The whole case was closed.
They attributed the whole thing to acoustic-type stub resonance, which is the amplification you get with the chamber of an acoustic guitar, perhaps a factor of 2. They actually called it organ pipe resonance, without understanding the physics of an organ pipe! After the pump change, vibrations continued to plague the station, and they fooled around with the end fittings to change the perceived stub resonance. As of this date, they've had to do modifications in the heat exchangers for the vibrations, and I fear the place is shaking apart!
The biggest mistake they made was attributing organ pipe amplification to passive resonance. In reality, there is a feedback mechanism with the air stream, which flows chaotically up against a knife edge. A tiny change in pressure makes the air stream flow into the pipe, compressing the air, while a change the other way, causes the air to flow outward, creating lower pressure. The air stream starts as white noise, and the organ tube selectively filters the resonant frequency. This sets up a wave train of acoustic waves going up and down the pipe. When a compression pulse hits the air stream, it pushes it out, creating low pressure, which adds to the open reflection pulse. This builds up into a tremendous sound!
The combination of the fuel bundles, the water flow, and the pressure tubes, created something much more powerful than an organ pipe, and we'll go into this next time, when I feel like it...