AIRCRAFT NUCLEAR PROPULSION PROJECT QUARTERLY PROGRESS REPORT for Period Ending June 10, 1952 (ORNL-1294)
R. C. Briant, Director
J. H. Buck, Associate Director
A. J. Miller, Assistant Director
W. B. Cottrell
June 10, 1952
The Aircraft Nuclear Propulsion Project at the Oak Ridge National Laboratory 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 carried out to provide support for other organizations participating in the national ANP effort. However, the purpose of the bulk of the ANP research at ORNL is the development of a circulating-fuel type of reactor. The nucleus of this effort is now centered on the Aircraft Reactor Experiment – a 3-Mev, high-temperature prototype of a circulating-fuel reactor suitable for the propulsion of aircraft.
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 of the Laboratory under its contract, W-7405-eng-26. The report is divided into four parts; I. Reactor Theory and Design; I I. Shielding Research; I II. Materials Research; and IV. Appendixes. Each part has a separate “Summary and Introduction.”
Analysis of the circulating-fuel aircraft reactor systems incorporating intermediate heat exchangers has led to the use of a spherical-shell type of heat exchanger and shield arrangement. This arrangement has resulted in an engineered reactor- shield assembly weighing about 8000 lb less than the best arrangement previously examined. A most promising design study has been undertaken of a c irculating-fluoride-fuel reactor core in which a thick reflector replaces the moderator. Such a design, which results in a homogeneous- fluoride reactor, has been shown to have a low critical mass and a neutron lifetime more than adequate to permit control. This compact, spherical- core design is compatible with the low-weight spherical shape 11 type of heat exchanger and shield arrangements (sec. 1).
The Aircraft Reactor Experiment to be constructed by the Oak Ridge National Laboratory was described in the last report. Only minor modifications in the design have occurred during the past quarter; the most significant changes were the reduction iu number of fuel passes through the core and the reversal of the inlet and outlet fuel headers. The design effort is concentrated on detailing drawings of components of the reactor and the procurement of these parts. The building for the ARE was released on June 6 to ORNL by the construction contractor, and installation of equipment is proceeding as rapidly as the receipt of parts permits ( s e c. 2 ).
The emphasis of the research and development program for reactor plumbing and associated hardware continues to be placed on the technology of high-temperature fluoride mixtures (sec. 3). Roth pumps and valves have been operated successfully with molten fluoride mixtures for extended periods of time at 1500°F. In both instances the problem reduces to that of sealing a moving shaft; this has been satisfactorily effected by both frozen seals and stuffing-box seals. NaK-to-NaK and Na-to-air heat exchangers have been operated – the former for over 3000 hours. In addition considerable effort has been devoted to developing instruments for measuring flow and pressure and for liquid level indication and control as required both by the ARE and the experimental high-temperature-liquid systems. Satisfactory techniques have been developed for the manufacture, transfer, and loading of fluoride mixtures without introducing contamination.
Studies of the kinetics of the circulating-fuel aircraft reactor have led to the conclusion that in spite of the loss of some delayed neutrons power oscillations in such reactors will be strongly damped; by a mechanism associated with the actual circulation of the ‘fuel (sec. 4). Physics research for the aircraft reactor experiment has involved numerous static calculations consequent to significant, but more: or less minor, design changes.
A critical assembly of the box-type, direct-cycle reactor was investigated for the GE-ANP program. Fission rate, flux measurements, reflector effects, and temperature response were determined. Upon completion of these measurements, a mockup of the circulating-fuel aircraft reactor will be assembled – the components are now on hand. The beryllium oxide machined for the ARE will be used in the critical assembly, together with a simulated fluoride mixture. A resume of the results from an earlier series of experiments with a graphite- moderated reactor is also presented ( se c. 5 ) .