|Back to Home||Back to Nuclear Tourist||Back to Travel|
B reactor Control roomIf the loading face is the heart of the reactor, then the control room is it's brain. This is the place where the reactor is monitored, and adjustments are made to maintain peak production. It is also the place where panicked men might make the decision to initiate an emergency shut down. Still, there was more to the control room than making certain that the reactor remained critical and did not blow up or melt down. Production had to be maximized.
Careful measurements were constantly taken and recorded of all reactor operating parameters. These were used by the physicists to determine how long the reactor should stay up, and even how long individual fuel slugs should remain in the reactor. In some ways, this reminds me of farming. You plant your seeds, and then depending upon the amount of rain, condition of the soil, heat and temperature, you harvest your crop at a certain time, when it is ripe. If you wait too long, the crop can spoil, out in the field. If you harvest too soon, the crop will not develop it's full yield. The crop, in this case, is Plutonium 239.
In theory, the longer you leave the slugs in the reactor, the large the amount of Uranium 238 that will be eventually transmuted to Plutonium 239. Unfortunately, in a reactor, Plutonium 239 can transmute into Plutonium 240, and Plutonium 241. P241 is useless, because of its high rate of spontaneous fission. P240 is even worse because, in addition to a high rate of fission and radioactivity, it transmutes into Americium, which is exceptionally toxic, as well as radioactive. So physicists would attempt to calculate the best time to discharge fuel for processing - largest amount of desirable P239, least amount of undesirable isotopes - according to recorded reactor activity. But it gets even more complicated. The activity of the reactor, called the reactor flux, is not the same everywhere in the core. It is more pronounced towards the center of the core, and towards the middle of the various channels. Using the crop analogy again, some parts of the farm get more rain, and more sunshine than others, so the crops grow faster. Of course, with more rain and more sunshine, they will also rot faster once ripe.
As experience was gained, operators developed the knack of fine tuning the control rods to attempt and minimize the differences in reactor flux. The painstaking and constantly revised measurements helped. A look at some of the photos below should give an indication of just how intricate these measurements were. Even with the best efforts, only about a quarter of the reactor fuel was generally ripe for discharge at any given discharge cycle.