The B reactor at Hanford has been declared a national historic monument!
This has some personal significance for me. When I worked at PNNL, I was able to tour the decommissioned reactor. That tour helped me connect with nuclear history.
The B reactor wasn’t created for electrical generation purposes. It was the first “production” nuclear reactor - ever. And, it produced one thing: plutonium-239 for Trinity and Fat Man.
The construction wasn’t complex, fancy, or particularly daring. The United States was at war. The reactor was effectively a scaled up version of the Chicago Pile (which has its own fascinating story) with concrete walls put around it. And, the physics determining the construction was simple:
It was a three story high cylinder of graphite riddled with hollowed out tubes. In those tubes were slugs of uranium separated by many more slugs of lead. When that much radioactive uranium is placed together, the neutrons emanating will a start a supercritical reaction.
You don’t want that to happen.
But, the graphite and lead buffer neutrons - moderating the reaction. And, the intense heat was mitigated by pumping thousands of gallons of water, straight from the Columbia river, through the tubes. The water came out contaminated and was then placed in the storage pools dotting the Hanford reservation.
Those storage pools weren’t very watertight. And, the cleanup continues to this day.
That’s it. The uranium will change into plutonium. When a slug is ready, you push it out of the tube. The plutonium falls into a pool of water with conveyor belts at the bottom. Rinse, wait for it to cool, and you’ve got bomb making materials.
Notably, the B reactor still has
Soviet Russian detectors from Cold War treaties. They check the flow of water from the Columbia. No water, no reactor.