Idaho National Laboratory Cultural Resource Management Plan

in the materials within the core area? Using its findings on this and other accumulated experience, Phillips
designed the next test reactor. 107
The Engineering Test Reactor. By 1957, higher neutron fluxes than what the MTR could provide
were in demand all over the country. Higher fluxes meant that an experiment could be carried out in a
shorter period of time. Lower fluxes, such as those provided in the MTR low-flux graphite zone, were no
longer in demand except as a “mine” for isotope production.
In addition, test requirements were growing more sophisticated. Using MTR beam holes involved
complicated and time-consuming handling problems. Also, in situations where it was important to have a
uniform rate of flux, it was hard to supply this to the sample. Many experiments needed more room in
order to be in the proper test environment and not impact the MTR operation. Phillips designed the
Engineering Test Reactor to solve these problems. It provided large spaces in the highest flux zone in the
core. Further, the flux was uniform along the entire 36-inch length of the fuel elements. 108
After the AEC approved Phillips' conceptual design, it hired Kaiser Engineers to design and build the
ETR. Kaiser had General Electric design the reactor core and its controls. From design to completion, the
project took two years. The reactor was a standard tank design except that its control rods were driven
through the core from below the reactor, not from above. This left the area above the reactor available for
experimentation. 109
Siting the ETR—Phillips situated the airtight ETR building about 420 ft south of the MTR (center to
center) so that it could share the MTR auxiliary facilities while positioning its cooling towers to the east.
Here it would be convenient to the MTR operational centers (such as the Hot Cell, Hot Plug Storage, and
Reactor Services Building) and yet be free of the facilities and services associated solely with MTR
operations. Many of the shared facilities—raw water, electrical and steam distribution, fuel oil, sewer,
standby power, waste disposal—then were extended or enlarged. This arrangement still left space
available for even further expansion of both ETR and MTR facilities. 110
The single-most critical design driver for the reactor building was the size of the reactor vessel. When
that was determined in October 1955, the rest of the planning continued. (The vessel is 35 ft long, with a
diameter ranging between twelve and eight feet. It had to withstand a pressure of 250 pounds per square
inch at a temperature of 200F.) Building height had to account for the bridge crane that would
manipulate and place the vessel. 111
Other design features of the complex were based on experience with the MTR. The MTR had
provided insufficient office space for both visitors and resident technical personnel. Desks cluttered the
reactor floor, balconies, and any free space near the experimental equipment. To address this, three-level
“lean-to” extensions were added to the ETR building on the east and west sides to prevent similar
frustrations. Partitioning of the reactor floor was avoided, leaving the entire area free for experimental
equipment. 112
107. IDO-16297, p. 5.
108. “Test Reactors—The Larger View,” Nucleonics (March 1957), p. 55.
109. Philip D. Bush, “ETR: More Space for Radiation Tests,” Nucleonics (March 1957), p. 41-42. The extra depth required for the
control rods meant that a portion of the foundation had to be blasted through lava rock. See also R. M. Jones, An Engineering Test
Reactor for the MTR Site (A Preliminary Study) (Idaho Falls: Phillips Petroleum Report No. IDO-16197, 1954), p. 7.
110. R. M. Jones, An Engineering Test Reactor for the MTR Site (A Preliminary Study (Idaho Falls: Phillips Petroleum Report No.
IDO-16197, 1954), p. 7.
111. R. H. Dempsey, “ETR: Core and Facilities,” Nucleonics (March 1957), p. 54; and Kaiser Engineers, Engineering Test Reactor
Project, Part I
112. R. M. Jones, An Engineering Test Reactor for the MTR Site (A Preliminary Study) (Idaho Falls: Phillips Petroleum Report No.
IDO-16197, 1954).
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