BSFusion wrote:I want to know more about this oscillation problem. Where should I look?
The problem arises even with large, ordinary reactors, where the total amount of "lattice units" (fuel + moderator) is many times the minimum for criticality.
But it is much less severe and readily managed, because the solid fuel is segregated from the moderator, which tends to dampen combined flux-thermohydraulic effects -- in contrast to MSRs, where things may be more intimately mixed (especially types without graphite or other solid moderator, or external moderation only).
Also, the risk is magnified with extreme aspect ratio -- both because the total amount of fuel salt is well above minimum for criticality (as compared to low aspect ratio cylinder or sphere), and because such configurations provide a nice resonance chamber for oscillation (think of an organ pipe and acoustic oscillations).
Another way to magnify the risk is by increasing compressibility of the fluid, for example with the presence of bubbles of fission product gases and vapors like Krypton, Xenon and Tritium, as well as Helium introduced on purpose to scavenge the FP gases.
The most extreme case would of course be a gaseous or vapor core reactor with extreme aspect ratio: In the 1950's there was in fact a concept for a strongly oscillating reactor that would extract electric energy by magneto-hydrodynamic means, as a shockwave passed several times per second from one end to the other, while interacting with coils wrapped around the cylinder.
The oscillation was of course driven by compression and fission power bursts at each end of the long cylinder, as the shockwave hit the end wall.
In commercial nuclear power, issues like neutron flux oscillations are generally handled by teams of reactor physics analysts working for the Company that designs and builds the plants.
So most of it is proprietary IP.
Not sure if you could find any textbooks or graduate-level courses that deal with the matter.
On a simpler level, there is much publicly available material on the subject of power-driven acoustic oscillation in fossil fuel burning furnaces, and also in rocket engines (rocket engines designed without careful attention to acoustic oscillation will explode within seconds of ignition...).