A diamond in Dogpatch: The 75th anniversary of the Graphite Reactor Part 1: The War Years The Graphite Reactor and its companion plutonium separations facility in Oak Ridge played an extraordinary role in the success of the Manhattan Project’s atomic bomb design and production effort. By Sherrell R. Greene ton Pile, the Graphite Reactor and its a humorously cynical allusion to the hill- companion radiochemical separations billy town made famous in Al Capp’s Li’l he old corrugated steel building building comprised the Manhattan Proj- Abner comic strip. As it turned out, Dog- sits quietly on Hillside Drive in ect’s plutonium Pilot Plant, or Clinton patch wasn’t remote enough. The decision Tthe very heart of Oak Ridge Na- Semi- works. (The formal name of the U.S. to move the Pilot Plant to Clinton was tional Laboratory’s (ORNL) original cam- World War II atomic bomb effort was, of accompanied by an even more disruptive pus. A modern day visitor to the lab can course, the Manhattan Engineer District. decision to move the planned plutonium easily miss Building 3001; most do. But Here we will employ Manhattan Project, production operations from the Clinton inside this old weathered building sits the the name adopted after World War II.) The Engineer Works to an even more remote Oak Ridge Graphite Reactor. Inside this Pilot Plant wasn’t even supposed to have site, soon to be identified as Hanford, in building, between November 4, 1943, and been built in what is now Oak Ridge. The Washington state. November 4, 1963, magic happened. The scientists at the University of Chicago’s As originally conceived, the Pilot Plant Graphite Reactor is one of the original and Metallurgical Laboratory (or Met Lab) had four objectives: (1) to serve as a tech- best preserved facilities of the Manhattan who conceived it in the summer of 1942 nology development and demonstration Project National Historical Park. Sitting assumed that the Pilot Plant would be platform for the much larger production alone in the operating gallery of the reac- built in the suburbs of Chicago. Howev- piles and plutonium separations facilities; tor on a rainy afternoon, you can almost er, as the potential risks of working with (2) to supply gram quantities of plutoni- hear the voices of Arthur Compton, En- atomic “piles” (a term coined because they um urgently needed to enable progress rico Fermi, Eugene Wigner, Alvin Wein- were quite literally carefully constructed in bomb design; (3) to serve as a training berg, and Glenn Seaborg. Today, as we piles of graphite blocks and uranium) and center for the staff of the larger produc- celebrate its 75th (diamond) anniversary, plutonium processing operations became tion facilities; and (4) to provide a devel- the Graphite Reactor remains a true time more widely understood, leaders of the opmental platform for the operating pro- capsule from the dawn of the nuclear age. Manhattan Project overrode the desires of cedures required for the plutonium pro- Originally known as the X- Pile, the Compton and his team at the Met Lab. duction facilities. Despite these sharply X- 10 Pile, and (more widely) the Clin- Within a few weeks of the appointment focused design objectives, the Pilot Plant in mid- November 1942 of E. I. DuPont and, in particular, the Graphite Reactor Sherrell R. Greene (<[email protected]>) to lead all Manhattan Project plutonium soon became the Swiss Army knife of is President of Advanced Technology Insights LLC production activities, the decision was the Manhattan Project. For almost two (ATI). Prior to founding ATI in 2012, he worked made to move the Pilot Plant to the Clin- decades after the Manhattan Project, the for 33 years at Oak Ridge National Laboratory, ton Engineer Works, a 59,000- acre site Graphite Reactor proved to be an unpar- where, during his last seven years, he served as near the small town of Clinton, Tenn., alleled multi- tool, whose utility for scien- Director of Nuclear Technology Programs and that had been selected by Gen. Leslie tific research, engineering development, Director of Research Reactor Development. This Groves, director of the Manhattan Proj- and radioisotope production far exceeded article is adapted from his forthcoming book on ect, the previous September as the site for anything envisioned by its developers. the history of the Oak Ridge Graphite Reactor, all Manhattan Project fissionable materi- Although created for military purposes, the birth of “Big Science,” and the making of the als production. The site, located about 17 it was at the Clinton Semi- works that the Atomic Age. miles west of Knoxville, was so remote (a art of harnessing the atom for peaceful Part 2: The Postwar Years will be published in long, overnight train ride from Chicago), purposes was largely pioneered. But that’s the December issue of Nuclear News. many had taken to calling it “Dogpatch,” getting ahead of our story. 38 • Nuclear News • November 2018 www.ans.org/nn Safety Rod Graphite Thermal Column 7-Foot-Thick Concrete Shield Channel Scanning Device Bridge Tubes Airflow Baffle Experimental Hole Fuel Loading Channels Through Shield Control Rod Location Loading Elevator Air Exhaust Uranium-Graphite Lattice Air Inlet Drawing: DOE Graphite Reactor design features The Pilot Plant The Graphite Reactor and its compan- ion radiochemical processing facility were the first progeny of a shotgun wed- ding between the Met Lab and DuPont. The Met Lab was a combative bride. DuPont was a reluctant groom. General Groves held the gun. After initially refus- ing to have any responsibility for the Pilot Plant, DuPont eventually surrendered to Groves’s relentless prodding, agreeing by January 1943 to assume responsibility for the design and construction of both the Pilot Plant and the plutonium produc- tion facilities. DuPont, however, would not agree to operate the Pilot Plant. After initially refusing to operate anything in Dogpatch, the Met Lab and the University of Chicago finally agreed to assume oper- ational responsibility for the Pilot Plant. The division of design responsibilities between the Met Lab and DuPont for the Pilot Plant was a masterpiece of obscu- rity and a testament to General Groves’s matchmaking skills. DuPont would “de- sign” the Pilot Plant, and the Met Lab would “check the design and be respon- sible for the adequacy of the information on physics and chemistry.” It was clear, however, that DuPont was in charge. The Graphite Reactor design that emerged from the DuPont/Met Lab design Photo: DOE team (and that of its companion radio- The Graphite Reactor and its control room November 2018 • Nuclear News • 39 water- rich barytes- haydite concrete. The outer dimensions of the shield—the visi- ble boundaries of the reactor—were about 47 feet long, 38 feet wide, and 32 feet high. Perhaps the most prescient design feature of the pile (located in Building 105, now 3001) was the access provided through the shield into the reactor’s core for instruments and experiments. There were dozens of openings of various sizes (up to 5 feet square) in the pile’s shield on all sides and the top, the intent being to provide access to the diverse nuclear and thermal environments afforded by the reactor’s power level and physical size. Among the more interesting pile access design features were the two “animal tun- nels” in the top face of the shield. These openings hosted an ingeniously designed carriage and gate device that allowed spe- Photo: ORNL cially machined graphite trays containing Mouse irradiation tray rabbits, mice, or other small creatures to be inserted and withdrawn during pile chemical processing facility) was elegantly surized accumulator system to shut down operation for the study of radiation effects simple, yet amazingly flexible. Wigner and the reactor in case of an emergency. Con- on mammals. Weinberg at the Met Lab were responsible trol rods entered the pile at right angles to The Separations Facility (Building 205, for the nuclear design of the 1- MWt reac- the fuel channels. Two horizontal borated- now subsumed in Building 3019), the de- tor. (Wigner, in later years, would credit steel regulating rods could be operated sign of which lagged that of the reactor Weinberg with having “singlehandedly” manually or automatically to provide fine by a few months, was the world’s first ra- created the nuclear design of the reactor.) control of reactor power. Four borated- diochemical processing “hot cell” build- The thermal design of the reactor seems steel “shim” rods (so called because they ing. Most of the basic design features of to have been shared between the Met Lab were normally only partially inserted into modern radiochemical processing and and DuPont’s design team in Wilmington, the core) could be automatically insert- nuclear fuel reprocessing facilities were Del., with DuPont leading the mechanical ed to shut down the reactor, or manual- first employed in Building 205. The facili- design and the two groups checking each ly inserted to compensate for reactivity ty utilized a hybrid plutonium separations other’s work. changes that the regulating rods could not “flowsheet” in which bismuth phosphate The reactor was a 24- foot cube con- accommodate. The reactor was surround- served as the carrier in the plutonium ex- sisting of 675 tons of graphite moderator ed on all sides by a 7- foot- thick laminated- traction steps, and lanthanum fluoride as blocks arranged in 73 layers. The blocks concrete radiation shield made up of the carrier in the concentration and iso- were machined on- site at Clinton. Thirty- layers of standard concrete and a special lation steps.[1] It contained six processing six rows of diamond- shaped, hollow fuel channels (a total of 1,248) on 8- inch centers traversed the pile from front to rear.