I’ve mentioned in earlier posts that my next reactor will be remotely controlled, however I haven’t really gone in depth as to why. Well, it really all comes down to minimizing neutron dose. While the x-rays the reactor emits from the viewport are extremely easily shielded, the neutrons, which are emitted in all directions, are exceedingly hard to stop. Although the reactor currently operates at a measly 30,000 neutrons a second (total isotropic emission), I plan for this next reactor to be able to reach outputs of >= 1,000,000 neutrons/second TIER, and hopefully sustain those outputs for an extended period of time (~30 minutes). This will allow for a myriad of experiments to be performed. Now, at these levels, the radiation hazard becomes somewhat troublesome. With shielding the neutrons not being a truly viable option, I have no choice but to get away.
By my calculations, operating at 1,000,000 2.45MeV neutrons/sec while standing 2.5′ away would result in a dose rate of 1.71 mrem an hour. While this is not terribly high, it is still wise to keep dose rates as low as reasonably possible. However, at 25 feet away, the neutron dose rate plummets to a minuscule .017 mrem an hour. As a comparison, the average airline flight clocks in at .5 mrem an hour at cruising altitude.
So far I’ve only installed two switches, one to operate the diffusion pump heater, and the other to operate the diffusion pump cooling system. These switches just switch 120v 60hZ AC from to wall, and are mounted on the reactor itself, as they will not need to be operated while the reactor is producing radiation.
The rest of the reactor’s control system will be comprised of a remote control unit attached via a 25′ long 25 conductor cable to the reactor, and 25 conductor cable from the reactor to the 30kV power supply. The control unit will have the following capabilities: displaying reactor voltage, reactor current, power supply on/off, and a momentary DPDT (double pole, double throw) switch to adjust the position of the reactor’s main throttle valve.
The display of current and voltage will be achieved through the use of two analog panel meters, reading the voltage across pins on the power supply. The power supply on/off will be accomplished by a SPST (single pole, single throw) switch across the “common” and “HV enable” pins of the power supply.
The control of the main valve will be slightly trickier. A 120v to 8v transformer, and bridge rectifier will supply a 3 RPM motor with DC power. This motor will connect via a chain drive connecting it to the valve. This assembly will allow the valve to open and close at a rate of around 8 degrees/second. The DPDT switch in the control unit will be wired so that the DC motor can be driven in a forwards or reverse direction.
Additional information that will be available remotely will be the totalized neutron count, pressure in the chamber, and a remote view through the reactor’s viewport, although these still have to have the details worked out.
