b'C H A P T E R 17S C I E N C E I N T H E D E S E R TIdaho Falls. It was one of those linger - the center loop were almost as effectiveIf we placed water between theTR Aing twilight evenings, still quite light. fuel and the sample, the fast neutrons as a circle. It soon became obvious thatOn that straight stretch of Highway 20 would leak into the water and collide by placing a beryllium reflector proper -across the desert, with its sage brush with hydrogen. This would slow them ly we could gain four more attractiveand the frequent lava flow patches, down and they would pile up to create loop locations.there wasnt much to distract us.a high slow-neutron flux. This is the so-called flux trap, which I didnt The more we looked at that strangeI started to describe a novel way to invent. arrangement, the better it looked.look at the problem before us. I thought Possible new locations for control ele -of breeder reactors, where the effort is I reached over across the front seat of ments became apparent. Byron was soto minimize the leakage of neutrons. I the car and with my finger drew four excited he volunteered to lay out thetried to think how we might make the circles for test loops, and then a snake-configuration. He didnt get much sleepneutrons leak in the direction of the like fuel line partially around each that night, but what he produced wassample, where we wanted to maximizeloop. Immediately, I saw that we could remarkable. His plan view showed thatthe number of neutrons absorbed into place another loop at the very center the entire serpentine fuel arrangementthe Navys samples. because the four arcs that surrounded could be produced with only one type offuel element. The number of test loopsgrew from the original four to nine.6The next several days brought the usualquestions from devils advocates. Asalways with a rich design, each nega-tive, when resolved, revealed new capa-bility. They sensed they had a winner.We quickly loaded the ETR CriticalFacility, said deBoisblanc, to modelthe serpentine geometry. The stunningsuccess of that program is another storyin itself. The mockup was really theclincher. 7Arranging the core into multiple differ-ent flux-trap regionsin which thepower level could be different in eachsimultaneouslywas something thatdeBoisblanc did invent. Satisfied, theAEC and the Navy selected the ATRcloverleaf design. Native ingenuity atthe NRTS had influenced the destiny ofthe lab one more time. 8This schematic drawing of the ATR core in cross section shows the arrangement of the nine test holes, the Now the ATR was under constructionserpentine arrangement of the fuel assemblies, and the sixteen control cylinders. Note the hafnium lining on just two hundred yards away from thethe cylinders. The hafnium-lined portion of the cylinder could be turned toward or away from the test hole, MTR. At the groundbreaking in 1961,depending on the desired neutron flux. Governor Smylie had said that the $40161'