OSU Reactor Cooling
In the late 1980's there was an initiative by the Federal Government to remove Uranium 235 (which could easily be made into a gun type nuclear weapon) from relatively unguarded research reactors around the country. Ohio State University was one such reactor and concurrently the operators there decided to make a power upgrade they had been considering for a while.
The issue was, if they upgraded the power of the reactor to 500 Kw they would have to implement an active cooling system since gravity flow would no longer keep the fuel rods cool enough. In addition, if a situation arose that necessitated the shut down of the reactor, such as a failed cooling pump, enough flow would have to be maintained that the residual heat would still be dissipated. In a traditional active cooling system the fuel rods would have been enclosed, removing the possibility for gravity flow.
For a while it appeared, that in order for both contingencies to be covered, that a class 1E fail-safe system would have to be installed. Such a system comprised of multiple pumps, back up generators, and additional containment tanks, would have cost millions of dollars that the university simply did not have. We looked at their problem and ended up designing an active cooling system that took water out the side, and used directed flow over the top of the fuel assembly to create a reactor that would; have active cooling while the reactor ran at full power, retain full gravity flow while the reactor was at minimum power, allow the operators access without a lot of disassembly of components, and used only one pump; saving the university a massive amount of money in the process.