b'P ROVING THE P RINCIPLEWe had already surveyed to see if we reactorholes, every place that was We found many places where the designhad any heavy leaks. For that we useddesigned to give access into the reactorwas a little bit inadequate. I turnedseveral kinds of metersGM meters, core. We used a lot of duct tape.over this data to the engineers, andcutie pies, and something we called a they designed better, more efficientrudolf. The barytes concrete in the Then we ran the reactor at low power plugs. But we still had to add extrashield, which had been packed in therewith the reactor holes closed up tight. shielding against some of the biggerpretty well to eliminate bubbles, did a Any radiation coming through the openings. We stacked boxes of paraffinpretty good job. Still, neutrons can openings would produce an image on and sheets of cadmium, which absorb-squirt around corners and come out thethe film, black rings or dots, or whatev neutrons, and then blocks of lead andholes, so we had to check those very er the shape of the leak. It took monthsconcrete in front of that. That was a lotcarefully. of the physicists playing around with of weight, and it had to be moved awaythe reactor to give all of the film an whenever it was time to load or unloadI plastered that reactor. We marked it equal amount of time. They were mak - 8the experiments.off and pasted these films all over the ing their own tests of reactor fluxes inthe different parts of the reactor, so on Paraffin itself was a hazard. Someoneany given day, one side of the reactor occasionally left a box near a hot watermight get more neutron flux than the pipe, where it would get too warm andothers. combust. Word of one too many paraf-Reactor Po w e r !P ower is the time rate at which ener- outpace the ability of the coolant togy is converted from one form to carry away heat. Therefore, it is notanother; it is commonly measured desirable to allow the neutrons to mul-in watts. Reactor power is the rate at tiply at an ever-smaller doubling time.which work can be done by the heatthat the reactor generates. It is mea- A reactor operator is concerned withINEEL 13405 sured in thermal watts. If the reactor three basic measurements of neutronRadiochemist loads an irradiated MTR flux wire into produces steam to drive generators, the flux: the doubling period, the watera scanner. The machine will count how many of output is measured in electric watts. temperature, and the water flow. Thethe wires atoms absorbed neutrons while in the reactor is set to shut itself down auto-reactor. A related concept is the reactor peri- matically if any of these reaches cer-od, once called the doubling period. tain previously established values.This is the amount of time it takes forthe neutron flux to double (approxi- Someone coined the dainty termmately). The art of reactor start-up and excursion to describe a sudden andcontrol is to keep the chain reaction unplanned rapid rise in the powerfrom doubling at too rapid a rate. The level. Many experiments at the Site operator adroitly moves regulating involved deliberately planned excur-(control) rods in and out of the core to sions, one purpose of which was tomaintain a constant power level. If the learn the safe operating limits ofneutrons multiply too fast, they will nuclear reactors.6 8'