AIRCRAFT NUCLEAR PROPULSION PROJECT QUARTERLY PROGRESS REPORT for Period Ending September 10, 1952 (ORNL-1375)
R. C. Briant, Director
J. H. Buck, Associate Director
A. J. Miller, Assistant Director
W. B. Cottrell
September 10, 1952
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 e £fort. However, the bulk of the ANP research at ORNL is directed toward the development of a circulating-fuel type of reactor. The nucleus of this effort is now centered upon the Aircraft Reactor Experiment – a 3-megawatt high- temperature prototype of a circulating-fuel reactor 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 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 over-all concept and design of the Aircraft Reactor Experiment were set forth in the two preceding reports. The most significant modifications during the past quarter have been those attendant to the specification of NaK as the reflector coolant and the NaF-ZrF.-UF. mixture as the 4 4circulating fuel. Most of the equipment for the experiment is now on order and some has already been received and installed in the ARE Building. The safety aspects of the reactor are being analyzed, particularly, the off-gas disposal system and the effect of a postulated fuel-tube rupture (sec. 1) . Valves, pumps, and instrumentation for the fluid circuit of the Aircraft Reactor Experiment are being developed (sec. 2). Valves with both bellows seals and packed seals have been successfully used with molten fluor ides, but the bellows seal appears to be the more reliable. Water tests with the maintained-level gas-sealed pump proposed for the ARE have been unsatisfactory. Since the packed seal is satisfactory when the back end is maintained at temperatures below the fluoride melting point, a pump incorporating this seal has been specified for the ARE. Instrumentation for the ARE fluid circuits must he designed so as to be unaffected by the high volatility and subsequent condensate of the ZrF4- containing fuel. Accordingly, flowmeters, pressure-measurement devices, and fluid-level indicators and controls are being redesigned and tested for this application. Data from the NaK-to-air radiator tests correspond exceptionally well with theoretical values. A hydrodynamic mockup of the ARE core has served to illustrate the problems associated with fuel loading and draining. Also of significance to the ARE is an experiment in which a fuel-tube rupture is simulated so that NaK (the reflector coolant) is injected into the fuel stream.
Theoretical investigations of the kinetics of the circulating-fuel reactor indicate that all subsequent oscillations will be moderate if the reactor survives the first, short, maximum excursion. The applicability of multigroup calculations to reactors with vastly different core and reflector materials is uncertain pending critical experiments. An improved method of computing the effects of gaps on reactivity has been developed (sec. 3 ) .
The recent experiments on the critical assembly of the General Electric air-cooled water-moderated reactor (R-1) have included reflector s tud ies and poison-rod calibrations. The preliminary assembly of the circulating-fuel reactor for the ARE has been critical with a uranium mass in excellent agreement with that predicted (sec. 4).