This is very important as you note Eric. Positive feedback operates in a manner which leads to an exponential rise in temperature with time in this case. It begins with some form of transient shock or noise in oscillator design and proceeds upward from that level.
If you gently reach the threshold then the process appears to start rising slowly. From what I have seen, one of the main time frame determining factors is the thermal mass of the device. The larger this factor is, the more time it takes to raise its temperature. A small low mass ECAT moves faster than a large one and thus the PWM period must be smaller to match. I am not too familiar with a nuclear reactor, but I suspect that the movement of the rods must be extremely careful and minor to keep it from getting dangerously out of control. It looks a lot like a nuclear bomb in slow motion. Dave -----Original Message----- From: Eric Walker <[email protected]> To: vortex-l <[email protected]> Sent: Mon, May 27, 2013 1:48 am Subject: Re: [Vo]: Constant temperature Operation of ECAT? On Sun, May 26, 2013 at 10:20 PM, David Roberson <[email protected]> wrote: My model suggests that his device is unstable once a threshold drive level is exceeded. Its temperature proceeds toward a dangerous level which might lead to device failure if not halted. The drive heat source is abruptly ended at a proper time which reverses the direction of the temperature movement. A relevant question is how fast the positive feedback takes over. If it proceeds quickly, then the reactor would just overheat and you'd get failure. If the feedback proceeds slowly enough to intervene, then presumably it can be pushed down before it gets too far. In the fission case of a fission reactor, I believe there is a short delay between when the reactor rods are moved and when the effect of the movement is fully realized in the new neutron flux that permits the use of a mechanical device for positioning the rods without the reactor becoming prompt critical. I'm thinking of the difference between the fast positive feedback of pointing a microphone at a speaker and a much slower version of it, where you could see that things are spinning out of control and then pull the microphone away before the sound gets really loud. Whatever that rate of change of the descent into positive feedback seems pertinent. Eric
