b'P ROVING THE P RINCIPLEBecause the MTR itself was an experi- research was calling for test holes and At the same time, demands for low-fluxment, Phillips tested how well the loops for thicker and longer elements, irradiation in the MTRs graphite zoneMTRs own components were holding more exotic metal alloys, and fuel that were in less and less demand. That partup. Had the high flux of neutrons would be cooled by gas or air, not only of the reactor was becoming obsolete.caused any structural weakness in the liquid metal or water. These items were By the end of the 1950s, these zonesmaterials within the core area? Using simply not going to fit into the MTR. were used mainly as a place to parkits findings on this and other accumu- Also, it was difficult in the MTR, if not cobalt and other isotopes requested forlated experience, Phillips was ready to impossible, to expose the entire length medical uses, a function that reactorsdesign the next generation test reactor. 21 of longer samples to a uniform flux. elsewhere in the country could performas well as the MTR. 22Phillips wanted the nextreactor building to have Thus in 1954, the Phillipsmore room on the reac- team was developing thetors operating floor. The next test reactor, named theMTR work area was Engineering Test Reactorcrowded with gear, equip- (ETR). After the AECment for experiments, and approved Phillipsconcept,blocks of extra shielding. Kaiser Engineers finishedOffice space was in short the design and built it.supply, and people set up General Electric designeddesks and work space the reactor core and its con-squatter-like in odd cor- trols. From design to com-ners, hallways, and at the pletion, the project tookedges of precious assem- only two years. Like thebly space. The next reac- MTR, the ETR reactor wastor would have a more water-cooled. Unlike thegenerous floor plan. MTR, its control rods weredriven through the coreAs for the reactor itself, from below the reactor, nottwo of the MTRs chief from above. This arrange-featuresthe power level ment left the area above theand the test spacewere reactor available for experi-too small. The power level ments. 23of forty megawatts wastoo low, unable to produce Aside from its higherthe concentrated neutron INEEL 56-4149 power level of 175flux required by the mili- ETR reactor vessel being raised to vertical position megawatts, the big changetary, which was typically on an acceler- during construction in 1956. with the ETR was that the samplesated schedule. Proposed military could be placed directly into the core ofapplications were pointing in the direc- the reactor, not just next to it, as withtion of fuel elements much larger in the MTR. The MTR operating experi-diameter than the early ones. The test ence had indicated that this would beholes in the MTR were no larger than safe and effective.one inch in diameter. Advanced1 1 4'