Idaho National Laboratory Cultural Resource Management Plan

abnormally, while the Safety Test Engineering Program (STEP) tests at the Power Burst Facility and
Loss-of Fluid Test facility would examine “what” would happen to a reactor in a full-scale accident. 226
To find out “what” would happen, the experimenters originally conceived tests that would involve
full-scale reactor systems and accidents. STEP was planned as a two-phase program. One phase—the
PBF reactor—would involve oxide core destructive excursion tests to be conducted in an open tank and in
a closed pressure vessel. SPERT I, south of TAN, would be modified for this phase.
The other phase would consist of the Loss-of-Fluid (LOFT) project and take place at the Flight
Engine Test Facility (FETF) at TAN. New facilities would be constructed and some existing facilities
modified and adapted. 227 This phase would simulate loss-of-coolant (or loss-of-fluid) accidents, in which
a coolant pipe would rupture. The test would deliberately initiate a rapid accumulation of heat in the
reactor core and cause a subsequent release of fission products from the melting fuel. This accident was
considered highly improbable to occur in a commercial reactor, but nevertheless it was posited as a
worst-case accident and referred to as the “maximum credible accident.”
The Power Burst Facility. The PBF reactor program advanced beyond the capabilities of the SPERT
reactors. It was equipped to examine in great detail how fuel reacted under accident conditions. The
reactor produced intense bursts of power capable of melting (and thus destroying) samples of fuel without
damaging the rest of the assembly. A loop carrying pressurized water through the core of the PBF reactor
permitted the testing of irradiated fuel samples containing highly radioactive fission products in a
controlled environment.
The research and experiments conducted during these programs extended the information base upon
which safety criteria, procedures, and regulations were developed. The PBF reactor was scheduled for a
series of forty tests. 228
Construction of the PBF reactor complex began near the old SPERT-I site on October 1965 and was
completed in October 1970. 229 The single-story PBF Control Center building, made of pumice block, was
located at the SPERT-I control area. The reactor console was in this building. The Reactor Building,
about half a mile from the control building, was 119 82 ft and had two annex wings, a main reactor
room, basement, and a sub-reactor room. 230
The complex included a variety of support and auxiliary buildings, including a well house, substation,
fabrication and development building, storage warehouses, emergency generator building, and others.
Many of these buildings remain in use. Additional buildings were constructed in the PBF area after the
PBF experiments ended and mission of the PBF area changed.
The PBF reactor had an open-tank reactor vessel, a driver core region where the test fuel was located,
and a loop coolant system. The loop coolant system provided temperatures and pressures typical of
pressurized water reactors. The water in the open pool provided cooling. The main core, usually referred
to as the driver core, was fueled with 18.5% enriched Uranium-235 contained in approximately 2,400 fuel
rods, grouped in assemblies containing 28 to 64 rods each. 231
226. J. A. Lieberman quoted in “AEC Plans Reactor-Safety Engineering Test Programs,” Nucleonics (February 1963), p. 19.
227. “Test Area North,” Nuclear News, May 1969.
228. Power Burst Facility (Idaho Falls: Prepared for the U.S. Department of Energy's, Idaho Operations Office by EG&G Idaho, Inc.
no date).
229. SPERT-I was decommissioned in 1964.
230. A. A. Wasserman, et al, Power-Burst Facility (PBF) Conceptual Design (Idaho Falls: Phillips Petroleum Report No. PTR-590,
no date).
231. Power Burst Facility (Idaho Falls: EG&G), n.p.
252