This quarterly progress report of the Aircraft Nuclear Propulsion Project at ORNL records the technical progress of the research on circulating-fuel reactors and ether ANP research at the Laboratory under its Contract W-7405-eng-26. The report is divided into three major parts: I. Reactor Theory, Component Development, and Construction, II. Materials Research, and III. Shielding Research.

Calculations are given for eighteen stainless steel clad helium bonded specimens of UO2-ThO2 containing normal U to be placed in 6 holes in a holder in a position of the ORR not to exceed a peak unperturbed flux of 4 x 10^14 n.cm^2/sec and irradiated to a peak nvt of 1.96 x 10^21 neutrons/cm^2

A 10% phosphoric acid solution contain 0.2% "Rodine 45" inhibitor is recommended to be used for the chemical cleaning of the HRT seam and closed colling water systems. Wet storage is recommended for both of these systems. The steam system is to be stored with steam condensate containing 100 ppm hydrazine, and closed cooling water system is to be stored with steam condensate containing 1000 ppm potassium chromate.

Test work was completed on development of a stripping method for the amine extraction (Amex) process which produces a concentrated uranyl nitrate solution for shipment to the refinery. This procedure offers potential cost savings by simplifying the overall mill-refinery flowsheet. The process involves treatment of the amine extract with calcium nitrate solution to convert the uranium in the solvent to a nitrate complex, stripping the uranium with water or dilute nitric acid, and recovery of nitrate from the solvent for recycle by contact with a lime slurry.

Continued work on the adsorbability of metal complexes from concentrated LiCl solutions and LiCl-HCl mixtures on a strong-base anion-exchange resin further demonstrated the much higher adsorbability of these complexes from LiCl solutions than from HCl solutions. The effect is believed to be due to the formation of less strongly adsorbed undissociated chloro-complex acids in the case of the HCl solutions.

Several experiments have been performed at ORNL with light water solutions of uranyl nitrate (highly enriched in either U^233 or U^235) in an essentially bare sphere 27 inches in diameter. This report presents the results of several calculations with elementary bare reactor theory and a discussion of the observed discrepancies between the calculated and experimental results. If the observed critical concentration is used in the calculations, the calculated effective multiplication constant is less than unity' thus a higher critical concentration would be predicted than is actually observed.

This compilation includes the following subjects: (1) Spectroscopic studies, (2) Neutral carbon in the vacuum carbon arc, (3) Anode effects, doppler blast effects, and stark broadening, (4) Neutrals in the high-current carbon arc; (5) Photon breakup of N2 in the high-current carbon arc, (6) Ion density in the high current carbon arc, and (7) Recombination cross-section for fast hydrogen ions and slow electrons. Minor revisions have been made in the subject memoranda in incorporating them in the compilation.

The "absolute" containment of ions in the DCX magnetic mirror field resulting from the cylindrical symmetry of the field is discussed. The regions of confinement in space and momentum are plotted for 300 Kev deuterons.

Either system appears to be fairly satisfactory from a containment standpoint. Current results indicate probable over-all rates of about 0.2mils/mo for titanium vs. 1.5-3.0 mils/mo for Ni-o-nel. Tests are not 100% comparable due to changes made in flowsheet conditions, but have been of sufficient variation and length as to allow good predictions to be made. Both metals show some tendency toward local attack in Thorex solutions. These tendencies are increased by poor welding techniques.

In a discussion about design of cyclotron resonators, the suggestion has been made that a wide range variable-frequency system might be constructed with two coupled resonant circuits. It also would present the possibility of tuning without the switching of high-current contacts, a troublesome item now commonly used for cyclotrons. One of the circuits would be the dee and its stem which might, or might not, be tuned. The second circuit could be located out of the magnet gap in a region where more space is usually available. Tuning could be accomplished by variation of the coupling between the two circuits and/or by, say, variable capacitance of the tuned, or tunable, circuit.

The OCUSOL-A program (ORNL-CF-57-6-4) for Univac is a modification of the Eyewash (ORNL-1925) multi-group, multi-region reactor code. The group=energy-lethargy-temperature relationship are given in Table A. The element code numbers are given in Table B. The cross sections now on the sigma-tape are given in tables in the Appendix numbered with the element code number. This technical report explains the bases for choosing the cross sections.

A method has been developed for the determination of total sulfur in fluoride salts using the methylene blue procedure. Reduction of sulfate to hydrogen sulfide is achieved through the use of a new reducing mixture consisting of stannous chloride dissolved in concentrated phosphoric acid. The new mixture is effective on microgram amounts of sulfate and offers a major advantage over the red phosphorous reducing mixtures in that larger samples may be taken for analysis. The procedure has been applied to fluoride salts containing from 1 to 500 ppm of sulfur. The coefficient of variation the method is 10 percent.

For various reasons it is not possible to leave the uranium or other nuclear fuel in a power reactor until all of it has been "burned up" by fission. In the case of liquid fuel (homogeneous) reactors a small part is continuously bled out, purified and returned. In the case of solid fuel reactors, fuel elements are periodically removed, reprocessed and the "unburned" fuel put back into service. In both cases the purification produces wastes which contain radioactive fission products and transuranic elements, and it is with the disposal of these wastes that we are concerned. For technical reasons, we will limit our consideration to the wastes from the processing of solid fuel elements, and from the processing of the very similar solid "blanket" elements in which fissionable fuel is made from non-fissionable isotopes of uranium and thorium by interaction with neutrons in the outer regions of the nuclear reactor.

Nickel is more susceptible to mass transfer in a 100hr non-isothermal dynamic corrosion system than is Inconel when exposed to a NaCl-MgCl2-UCl3 (50.0-33.3-16.0 mole %) bath at a hot zone temperature 1800 F. No nickel mass transfer was observed in a 500-hr test at 1350 F, but Inconel showed some attack under these conditions. Inconel mass transfer was observed in both tests, being more severe at the higher temperature. On the bases of these preliminary tests, it appears that nickel is a more satisfactory container than Inconel for the chloride bath at temperatures in the region of 1350 F. The chromium is more susceptible to selective leaching from Inconel at 1800 F during a short 100-hr test (0.26% Cr in bath) than in a 500-hr test (<0.001% Cr in bath) at a lower temperature (1350 F ).

The general Wigner-Eisenbud theory is used to develop a method of analysis for the cross sections of fissionable nuclei. The method is employed in giving a reasonable description of the low energy cross sections in U/sup 235/. The single level fit for U/sup 235/ is known to be unreasonable. Many level expressions for the cross sections are derived--the only approximation to the general theory being the neglect of all but a small group of resonances. It is shown that regardless of the number or definition of the fission channels the many-level expressions require few level parameters: the E/sub lambda /, GAMMA / sub lambda n/, GAMMA /sub lambda gamma / and GAMMA /sub lambda F/ of the single level theory for each resonance and a few additional parameters pertinent to the interference between levels. The interference terms are described and shown to be important. The shape and size of the U/sup 235/ cross sections below 2 ev are fitied to within one per cent using (a) only one negative energy resonance of smaller size than in the single level fits (b) no additional levels to fit the shape other than the observed levels at positive energies (c) three interference parameters …

Design calculations were made for a system consisting of a pump, one hundred feet of pipe, and a heat exchanger to remove 1 Mw of heat from various aqueous thorium oxide slurries. The rheological properties of the slurries were varied over a range of yield stresses from 0 to 1.5 lb/sq ft and of coefficients of rigidity from 1/2 to 2 centipoise. Two different cases were studied: a heat exchanger having fixed axial and radial delta T in which the tube length was allowed to vary and a heat exchanger having fixed tube length in which the axial and radial delta T were allowed to vary. It was shown that the pump power must be increased by a factor of 15 to 30 in order to maintain satisfactory operation of the heat exchanger as the slurry yield stress is increased form 0 to 1.5 lb/sq ft. However the pump power is essentially independent of heat exchanger tube diameter for any given slurry. The rated capacity of a slurry heat exchange is essentially independent of slurry yield stress and coefficient of rigidity, provided that the tube velocity can be suitably increased as the slurry yield stress in increased.

The use of mercury as a solvent in the recovery of uranium from spent fuels is of the interest at Oak Ridge National Laboratory. The vapor pressure of mercury is lowered by increased concentration of uranium. By dew-point measurements, the vapor pressure at 175°C was found to very between 2 and 8mm of mercury, and at 375°C, between 300 and 1100 mm of mercury, depending upon composition as described below. Plots of the log of mercury vapor pressure vs. the reciprocal of absolute temperature gave a family of straight lines. Each line corresponded to one of the composition: UHg2, UHg3, UHg4, and a saturated solution of UHg4 in Hg. No Mutual solubility of the intermetallics was indicated.

A replica electron microscope study of as-polished and cathodically etched surfaces of pyrolytic carbon coating on fuel particles has been made in an attempt to characterize coatings that showed as much as a 30% difference in bult density. High and low density coating could be characterized by their polished surface textures; however, these features were not indicative of the true structure as seen by direct electron transmission. Microvoids detected by the transmission study of cleavage flakes exist on too fine a scale to be observed either optically or by electron microscope examination of replicas of the polished surface. Other features such as the effect of cathodic and chemical etching, coating delamination, and duplex coating interfaces have also been examined.

The ORNL 86-in. cyclotron is being modified to provide for deflection of the proton beam. It is expected that operation will be resumed late in the spring. Nuclear physics work was limited, for the most part, to interpretation of previously collected data and to making preparations for utilizing the deflected beam. It was found that for certain isotopes the production rates could be almost doubled by operating at a slightly reduced energy and a much larger current. With the use of the ORNL 63-in. cyclotron, the absolute values of the electron capture and loss cross sections for 26-Mev nitrogen ions were obtained. The angular distribution of the cross sections for elastic scattering of nitrogen by nitrogen was measured at energies from 13 to 22 Mev. A double-focusing 90-deg magnet is being planned for use in identifying stable reaction products from nitrogen-induced reactions. The major components of the revised 44-in. test cyclotron were assembled and are being tested. Consideration is being given to the use of these components, along with a new 20,000-oersted magnet and a shielded cyclotron room, and if the tests are satisfactory the Laboratory will have available a machine which will accelerate N5+ ions to 81 Mev.

The power and estimated reprocessing load are tabulated for existing and proposed United States and United States-built reactors of 10 Kw or greater thermal power.

A slurry addition system, a venturi in the circulation loop, and two types of sampling systems were tested with 500 and 800 g Th/kg H2O slurries in the 200 gpm loop at 250 C and 1000 psig. The addition system worked satisfactorily while the venturi gave erratic readings during part of the run. Both the capillary and in-line sampling systems proved satisfactory with the capillary sampler being much easier and more convenient to operate. The addition of uranium to the slurry had no appreciable effect on the handling characteristics, the attack rate on 347 SS, the particle size and crystallite size of the thorium oxide. The attack rate was found to be 1 mpy during the first 100 hours of circulation and decreased to 0.4 mpy at the end of the run.

Technical report covering the work done to explore heat transfer analytically and experimentally in liquid metals in turbulent flow within the thermal entrance region of circular tubes having uniform well temperature. Includes implications of this research. [From Summary]

By using a large central fuel and blanket reprocessing facility, slurry-fueled aqueous homogeneous reactors can attain an estimated minimum fuel cycle cost of 1.4-1.6 mills/kwh; with solution-fueled two-region reactors, a doubling time of 14 years may be obtained at a fuel cycle cost of 2.0 mills/kwh. On-site processing appears desirable only for large power stations made up of reactors designed for short doubling times. For instance, a solution-fueled two-region reactor can attain a 12-year doubling time at an estimated fuel cycle cost of 1.5 mills/kwh at a 2000 Mw electricity station with an on-site processing plant.

This technical report summarizes some preliminary calculations of fuel exposures attainable in heterogeneous reactors, fueled with a mixture of thorium and U233, moderated with D2O and operated with no net loss in fissionable fuel.