Aircraft Nuclear Propulsion Project Quarterly Progress Report for Period Ending February 20, 1950
- ORNL
Shielding. The formal proposal for the new bulk shield testing facility is now awaiting approval by the AEC. This will be a 10 kw water-moderated critical assembly, made up of MTR fuel elements. Measurements in the lid tank shield test facility are now complete on pure water, and numerous measurements have been made on lead-water combinations. The power of fission source used in the lid tank work has been measured as 6 ± 1 watts. The water data are summarized in this report. Secondary gamma are observable in lead-water combinations containing as much as 26% lead. These recent data applicable to the inner regions of the shield appear to fit a "one collision and out" theory for neutrons. The measurements on lead and water combinations suggest that an idealized aircrafts shield for a two-foot reactor might weigh about 67 long tons. Measurements are being made at present on a combination lead--iron--water shield intended initially for Naval reactor use. The spectra of mock fission and of Po--Be sources have been measured incidental to the development of a proton recoil neutron energy spectrometer, The integrated neutron flux from the Po--Be source indicates a yield of 3.5 x 106 neutrons per curie. A fast neutron detector, based on resistance changes in a Pd film semiconductor, is under development, Improvements in gamma and neutron measurements to be instituted shortly include use of anthracene scintillation counters and proton recoil fast neutron detectors. Further calculations on uranium hydride shields are in progress. A survey indicates that ton lots of non-pyrophoric uran1um hydride of density about 9 gms/cc can probably be obtained with some effort. The dissociation pressure of hydrogen gas over this material is not expected t o be more than about 1 atmosphere at 430°C. Sheets of B4C in a tygon plastic matrix have been fabricated for testing the effectiveness of secondary gamma suppression through neutron absorption in boron. Additional tests on expansivity, moisture content and radiation damage have been made on MO and MI (boron-containing) concretes. Procedures for large-scale rolling of Boral sheets are being developed. The thermal conductivity of Boral has been found to lie between low carbon steel and aluminum, in the temperature range around 1200° F. Heat Transfer. An experimental rig for heat transfer studies with lithium at 1800°F is being fabricated from stainless steel, type 347 . A canned rotor liquid metal pump is also being constructed, using a liquid film bearing. Metallurgy aad Materials. A number of static corrosion tests have been made in which nickel, zirconium, iron, tungsten, tantalum molybdenum and columbium have been exposed to liquid lithium and bismuth for four hours at 1800°F. The next series of tests will be conducted at 1800°F for 40 hours, The first results with liquid lithium indicate best resist ance in iron, molybdenum and zirconium; however, the data are still very preliminary. The question of purity of the liquid lithium is now under study. With liquid bismuth, zirconium was severely attacked, Dynamic corrosion test equipment is now being constructed for measurements under convective circulation conditions in liquid bismuth and lithium. Corrosion harps are being made of various stainless steels as well as V-36 and L-605 alloys. Equipment is being designed for stress--rupture and creep tests, Preliminary tests are underway to find container materials for liquid uranium--bismuth and uranium--lithium alloys. Radiation damage. Accelerator experiments to determine radiation damage in various high temperature materials will shortly get underway at Berkeley and at Purdue. Various high temperature materials will also be placed in the Hanford reactor soon, An experiment is being designed for simultaneous radiation damage and heat transfer tests of circulating lithium system in the ORNL reactor. A high-intensity gamma source has been developed for use with the ORNL reactor. This is a hollow gold cylinder, which after irradiation for one week produces 105 r/hr upon materials at its center. Data on change in electrical properties of various irradiated plastics are presented in this report. Preliminary measurements have been made on the radiation-induced dissociation of lithium, titanium, and zirconium hydrides. Nuclear measurements. Preparations are underway for the neutron cross section measurements needed in ANP work. These will involve use of a 5 Mev Van de Graaff accelerator and a high-speed mechanical velocity selector, Li7 separation. The work at the Y-12 Research Laboratory on the practicality of obtaining tonnage lots of highly purified Li7 by chemical methods is discussed in this report because of the possible application of this metal as an aircraft reactor coolant and moderator. Separation methods under study include molecular distillation of Li metal, 1in exchange methods countercurrent electrolysis and electromigration, The most promising system so far is a liquid-liquid exchange column using dual-temperature for continuous operation.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- Contributing Organization:
- Y-12
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 1232662
- Report Number(s):
- ORNL-629
- Country of Publication:
- United States
- Language:
- English
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