R. C. Briant, Director
J. H. Buck, Associate Director

A. J. Miller, Assistant Director

Edited by 

W. B. Cottrell

December 10, 1952


This quarterly progress report of the Aircraft Nuclear Propulsion Project at ORNL records the technical progress of the research on the circulating-fuel reactor and all other ANP research at the laboratory under its Contract W-7405- eng-26. The report is divided into four parts: I. Reactor Theory and Design; II. Shielding Research; III. Materials Research; and IV. Appendixes. Each part has a separate Summary and Introduction.


The Aircraft Nuclear Propulsion Project is comprised of some 300 technical and scientific personnel engaged in many phases of research directed toward the nuclear propulsion of aircraft. A considerable portion of this research is performed in support of other organizations participating in the national ANP effort. However, the bulk of the ANP research at ORNL is directed toward the development of a circulating-fuel type of reactor.


The nucleus of the effort on circulating-fuel reactors is now centered upon the Aircraft Reactor Experiment – a 3-megawatt high-temperature prototype of a circulating-fuel reactor for the propulsion of aircraft. The current status of the ARE is summarized in section l; however, much supporting research and developmental information on materials and problems peculiar to the ARE will be found in other sections of Part I and Part III of this report, in addition to the general design andmaterials research contained therein. Shielding Research, Part II, is devoted almost entirely to the problems of aircraft shielding.


The Aircraft Reactor Experiment (sec. 1) is now well into the transition period between design and reality. The design is essentially complete, almost all the components are on order, and a substantial number of these have been received and installed in the ARE Building. The significant modifications during the past quarter include completion of the off-gas system design (incorporating holdup tanks rather than charcoal adsorbers) and the inclusion of a reactor by-pass (so that the fluid circuits may be checked out independently of the reactor). Coincident with the completion of the reactor design, the Aircraft Reactor Experiment Hazards Summary Report, ORNL-1407, was submitted to the AEC for approval. It is anticipated that even though the experiment may be completely assembled by the summer of 1953, a significant and indeterminant. period will be required for shake-down operation before the reactor becomes critical.


Valves, pumps, instrumentation, and other components of both the fluoride fuel (NaF-ZrF4-UF4, 50-46-4 mole %) and reflector coolant (NaK) circuits are being developed for the Aircraft Reactor Experiment (sec. 2). In most instances, these components have been tested on smaller than full- scale prototypes of the actual ARE components. Tests are now under way, however, on the full-scale pumps, valves, and some instrumentation designed for the reactor experiment. At this time, centrifugal pumps with both gas seals and frozen seals have operated satisfactorily for extended periods at temperatures between 1200 and 1500°F. A combination packed and frozen seal has been specified for the ARE pump. Although a bellows type of seal has been specified for the ARE, a considerable program has been undertaken on high-temperature, self- lubricating seals.


The rotameter type of flowmeter and the modified Moore Nullmatic pressure transmitter have both operated satisfactorily at high temperatures (~1400°F). Neither of these instruments is affected by the ZrF4 vapor above the fuel. Vapor traps of the type that will be required in the gas system above the fuel surge tanks have been satisfactorily developed.


The heat transfer coefficient of an aircraft type of sodium-to-air radiator, in which the radiator fins were sectioned every 2 in. in the direction of air flow, was increased 20% over that of the same radiator with plain flat fins.


The general design studies (sec. 3) were confined to performance analysis of a Sapphire turbojet engine in which the engine radiator performance was extrapolated from a sodium-to-air radiator section tested at ORNL. Performance data for both the radiator and engine are presented. Arrangements have been completed with the Wright Air Development Center for their participation in the development of high-temperature 1iquid-to-air aircraft radiators.


The several reactor physics studies (sec. 4) include those of oscillations in a circulating fuel reactor, a technique for reactor calculations, and the temperature-dependence of a cross section exhibiting a resonance. The damping influence of fuel circulation has been demonstrated even when the earlier assumptions are replaced by more realistic conditions. With regard to reactor calculations, it is shown that the slowing down of neutrons in parallel slabs of materials with different properties can be described in some instances by a set of images of the original neutron source.


Critical assemblies of both the Aircraft Reactor Experiment and a reflector-moderated reactor have been tested (sec. 5). Critical mass.



Dec 27, 2014   877   egeneration    Aircraft Reactor Experiment, ORNL School Of Reactor Design Central Files
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