b'P ROVING THE P RINCIPLEReactorLast Day of Name Acronym S t a r tuOperationp14. Engineering Test Reactor ETR 9-19-57 December When the Engineering Test Reactor started up at the TRAin 1957, it was the largest and most advanced1981materials test reactor in the world. The 175-megawatt reactor provided larger test spaces than the older MTR and provided a more intense neutron flux. The ETR evaluated fuel, coolant, and moderator materials under environments similar to those of power reactors.In 1972 the ETR was modified by the addition of a Sodium Loop Safety Facility into the reactor core. With this, the reactor played a new role supporting DOEs breeder reactor safety program. ETR test programs related to the core design and operation of breeder reactors. As testing progressed, the reactor was again modified with a new top closure accommodating the irradiation loop. Other additions included a helium coolant system and sodium-handling system. The ETR was the first complete reactor facility to be deactivated and documented immediately after shutdown.15. Engineering Test Reactor Critical Facility ETRC 5-20-57 1982ETRC was a full-scale, low-power nuclear facsimile of the ETR, similar in function to the ARMF and ATRC. It was used to determine in advance the nuclear characteristics of experiments planned for irradiation in ETR and the power distribution effects for a given ETR fuel and experiment loading. Since no two ETR loadings were identical, the ETRC allowed operators to predict the ETRs nuclear environment when completed experiments were removed or new ones added.This information was necessary to calculate the experiment irradiation and determine core life, control rod withdrawal sequences, reactivity worths, and core safety requirements.Proposed fuel and experiment loadings were first mocked up in ETRC and manipulated until a desired power distribution throughout the core was attained, satisfying pertinent safety requirements. The ETRCslow-power tests allowed the ETR to operate without interruption, saving time and money.16. Experimental Beryllium Oxide Reactor EBOR Never operatedModifications of a former ANPbuilding at TAN, the Shield Test Pool Facility, began in May 1963 to house the Experimental Beryllium Oxide Reactor (EBOR). The objective of the reactor was to develop beryllium oxide as a neutron moderator in high-temperature, gas-cooled reactors. The project was canceled in 1966 before construction was complete. Among the reasons for the cancellation was the encouraging progress achieved, concurrent with EBOR construction, in developing graphite as a moderator.This reduced the importance of developing beryllium oxide as an alternate.17. Experimental Breeder Reactor No. I EBR-I 8-24-51 12-30-63EBR-I, the first reactor built at INEEL, began operation in 1951. The reactor produced the first usable electricity from nuclear heat on December 20, 1951. It achieved full-power operation the next day. In 1953, the reactor confirmed that a nuclear reactor designed to operate in the high-energy neutron range is capable of creating more fuel than its operation consumes (breeding). The reactor, which used enriched uranium as fuel, was unmoderated. It used sodium-potassium alloy (NaK) ascoolant. Ablanket of uranium-238 around the core provided the fertile material in which breeding took place.The liquid-metal coolant permitted the neutron energies to be kept high, thus promoting fissionable-material breeding. The coolant also enabled high-temperature and low-pressure operation, both conducive to efficient power production.President Lyndon B. Johnson dedicated EBR-I as a National Historic Landmark on August 26, 1966. It was subsequently opened to the public for visits and tours.18. Experimental Breeder Reactor No. II EBR-II 9-30-61 9-30-94Part of the continuing investigation of fast neutron breeding reactors, the EBR-II, located at Argonne-West inside a containment shell, was built to demonstrate the feasibility of on-site fuel reprocessing as an adjunct 26 2'