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The Argonne Fast Source Reactor is designed to operate at low power (nominally 1000 watts) to supply neutron fluxes, both fast and thermal, for laboratory experiments. It is built around a-cylindrical core (with vertical axis) of solid, highly enriched uranium approximately 42 inches in diameter by 4:^ inches high. The blanket is of solid depleted uranium with a minimum thickness of eight inches; its outer form is cylindrical, 20^ inches in diameter by 20-| inches high. The reactor, contained in a shield of high density concrete of minimum thickess 4-2 feet, is freestanding on the floor of the reactor building. A graphite thermal column 4x4x6 feet is provided. All control and safety mechanisms are located in a pit beneath the reactor. The hazards associated with operation of the reactor have been analyzed. A number of potentially dangerous circumstances were studied to determine the probable severity of the resultant excursions. As an upper limit, a detailed study was made of the extreme case in which the reactor, overloaded by five kilograms of U^^^, goes critical at the air cylinder speed of 18 inches per minute. It is estimated that the excursion would amount to 3.6 x 10^^ fissions. This is expected to destroy the core and eject all core material into the pit where it burns, greatly adding to the total energy of the excursion. No rupture of reactor shield or building is expected. The reactor pit and reactor building will be heavily contaminated and some radioactive miaterial will escape from the building. It is nearly certain that the maximum radiation dose to personnel outside the reactor building will not exceed 15 roentgens. Consideration of the design characteristics, possible accidents and method of operation lead to the conclusion that the reactor is fundamentally safe for the following reasons: 4. Both core and blanket are at maximum density; almost any conceivable disturbance reduces reactivity. 5. Even in the event of a severe excursion, the isolation of the site, the prevailing winds, and the low inventory of fission products minimize the number of persons exposed and the severity of their exposure.
Measurements of prompt-neutron lifetime by the Rossi-ct method in more than 30 different critical systems are reported. Most were assembled in Argonne's Zero Power Reactor III (ZPR-III). The Rossi-a method, which has been described in the literature,(l>4,5) represents a direct experimental determination of the ratio Akp/To, from which a value for To is obtained if an estimate of Akp is available. P(t) At = CAt + Ae^-i^i"^)* At + Be^-"'^''')* At , where the two amplitudes A and B were nearly equal. The larger alpha is interpreted as representing the time behavior of chain-related neutron pairs having no intervening events in the beryllium. The smaller alpha represents the time behavior of chain-related neutron pairs when at least one intervening event has occurred in the beryllium. When the terminating counter was placed in the beryllium, a single value for alpha was obtained which agreed with the smaller value found in the core. The disappearance of the fast decay in this case supports the hypothesis that the larger alpha is associated with the core composition. Further, an extension of Orndoff's theory gives a method, of determining the reactivity of the fast system independent of the reactivity contribution of a moderating reflector.
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