b'A P P E N D I X BFifty Years of Reactors at the INEELA fter the first reactor at the National Reactor Testing Station(Experimental Breeder Reactor-I) went critical in 1951, scientists built and operated dozens more reactors in the next fivedecades. Since the 1970s, it has become accepted that 52 reactors operated at the Site.But counting reactors at a reactor research facility is not as straightforward as it might seem, nor is accumulating vital statis-tics about each reactor. While considering the reactors that operated on the Idaho desert, the following thoughts might bekept in mind.First, scientists in different programs did not seem to follow the same rules when it came to naming reactors. For example,the Aircraft Nuclear Propulsion (ANP) program modified the core of the reactor it called HTRE-1 and named it HTRE-2.These were subsequently known as two reactors. In another program, experimenters changed the core of the OrganicModerated Reactor more than once, but the reactor retained the same name and was counted as one reactor. When theExperimental Breeder Reactor-II operated as a prototype of the Integral Fast Reactor, the name did not change. Thus, any listof reactors very definitely understates and under-represents the actual complexity of reactor development at the Site.Second, the list-maker must decide what to commemorate in a list of reactors. Should reactors that never went critical begiven a place? If so, the list will include the Experimental Organic Cooled Reactor. No uranium fuel ever was loaded into thereactor and it never operated or went critical before the program was canceled. It was a reactor, but never an operatingreactor. This was true as well for the Experimental Beryllium Oxide Reactor.This list does not include simulated reactors such as Semiscale, which was part of the reactor safety testing program. Theomission of facilities like this is another way in which a list can understate the variety and complexity of the INEELsnuclear reactor history.Finally, not all the information one might desire about the history of a reactor is easily found. For example, one goal for thislist was to identify the day, month, and year of initial criticality for each reactorand the date of its final shutdown. But theINEEL Technical Librarys vast collection of archived reports did not yield this information for each reactor. Some reportwriters were content to report that a reactor went critical in the summer of a certain year and leave it at that. The samewriters may have considered other milestones, such as its first operation at full power, to be more meaningful in theprogress of their particular reactor.This alphabetical list of reactors contains the names of 52 reactors (the fifty that operated and the two that did not) as theyhave been known traditionally, their acronyms, selected milestone dates, and descriptive information about each reactor. Allreferences to megawatts are thermal megawatts. Readers who examine this list are invited to contribute additional mile-stone dates and other vital statistics about the reactors so that future lists might be made more complete and more accurate.25 9'