PROGRESS RELATING TO CIVILIAN APPLICATIONS DURING FEBRUARY 1961

Reactor Materials and Components. The stresses required to produce creep rates of 0.001, 0.01, and O.l%/hr at 650, 800, and 1000 deg C were measured for Nb--2.37 wt.% Cr, Nb--3.34 wt.% Zr, snd Nb--5.21 wt.% V; anneals of these three alloys showed recrystallization only for heat treatment at 1260 deg C. Fabrication of miniature heating elements and thermocouples for a power-balancing thermal neutron fiux sensor is described. Fuels. Rolling propenties of Nb-10 wt.% U and Nb--20 wt.% U at 1000 deg F are described. Air oxidation tests were made at 1100 deg F for the following compounds: (Th/sub 9/U)C, ThC - lOUC - 5NbC, ThC - 10UC - 5SiC, ThC - 10UC - 2.5Mo/sub 2/C, ThC - 10UC - 5ZrC, (Th/sub 9/U)C/ sub 2/, ThC/sub 2/ - 10UC/sub 2/ - 5NbC, ThC/sub 2/ - 10UC/sub 2/ - 5SiC, ThC/sub 2/ - 10UC/sub 2/ 2.5Mo/sub 2/C, and ThC/sub 2/ - 10UC/sub 2/ - 5ZrC. Hardness measurements on Th--5 wt.% Pu snd Th--10 wt.% Pu show that complete recrystallization occurs within 1 min at 700 deg C. X-ray diffraction sthdies indicate No--25.6 wt.% Pu-6.1 wt.% Si to consist of free Nb and Nb/sub 5/Si/sub 3/ . Sintering and melting expeniments on PuO/sub 2/ in Ar and H/sub 2/ show that melting is caused by the existence of Pu/sub 2/O/sub 3/ in Ar or by reduction of PuO/sub 2/ to Pu/sub 2/O/sub 3/ in dry H/sub 2/. Compatibility tests with PuO/ sub 2/ pellets encased in types 304, 316, 318, and 347 stainless steel and Inconel, run for 2 hr at 1900 or 2000 deg F in H/sub 2/, gave no evidence of failure. An equation is presented which describes the in-pile steady-state release rate of fission products from dense plates. Fuel Element Development. A reaction layer was found at the interface between type 304 stainless steel cladding and UN-type 347 stainless steel cerments gas-pressure bonded at 2300 deg F. Fabrication of UN cerments is described. Experiments conducted with compacted mixtures of plastic binder, stainless steel powder, and UO/sub 2/ powder are described. Developmext of Uranium Carbide. Cores of UC and UC --10 wt.% Mo/sub 2/C were hot pressed at 1480 deg C, and density measurements before and after sintering are reported along with particle-size data. Uranium carbide melts were cast; analyses of castings gave 5.1 plus or minus 0.3 wt.% C. Phase studies of as-cast U--5.9 wt.% C and U--6.5 wt.% C were conducted which show UC --UC/sub 2/ mixtures and indicate a eutectlc in the UC--UC/sub 2/ system. Diffusion studies gave a preliminary value of 5 x 10/sup -//sup 8/ cm/sup 2//sec for the self- diffusion coefficient of C in UC at 1600 deg C. The research program on radiation effects on UC is described briefly. Growth of UO/sub 2/ Single Crystals. Experiments using a high-temperature tungsten reslstance furnace to grow single UO/sub 2/ crystals from melt are reported. It appears that tungsten is compatible with molten UO/sub 2/ and that dissociation of UO/sub 2/ does not occur up to its melting point. Other topics discussed in the abstract include: Radioisotope and Radiation Applications; Materials Evaluation; Coated-Particle Fuel Materials; Recovery of Spent Reactor Fuel Elements; Fueled Graphite Elements for Pebble-Bed Reactor; Cold Bonding of Zircaloy-2 to Type 410 Stainless Steel; Gas Cooled Reactor Program; Corrosion of Thorium and Uranium; and Gas-Pressure Bonding of Be-Clad Elements