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161. Development of continuous-matrix fuel rods for advanced high-temperature gas-cooled reactors
ABSTRACTS
693
were found to have higher apparent crystallite sizes and smaller Young’s Moduli than low temperature deposits. Under neutron irradiation, the apparent crystallite size tends towards an equilibrium value dependent only on the pre-irradiation apparent density. 161. Development of continuous-matrix fuel rods for advanced high-temperature gas-cooled reactors* R. L. Hamner, J. M. Robbins and J. H. Coobs (Metals and Ceramics I&&ion, Oak Ridge National Laburatory, Oak Ridge, Tennessee). Continuous-matrix graphite elements with particle volume loadings of 30-45 per cent were extruded to close dimensional tolerances at an extrusion rate of 10 ft/min. Similar specimens prepared by slurry blending and warm-molding have withstood irradiation testing to a fast fluence of 7.5 X loZ1 neutrons/cm2 at 115O”C, and extrusions are now being irradiated. *Research sponsored by the U.S. Atomic Energy ~mmission
under contract with the Union Carbide Corporation.
16% The influence of nongraphitic carbon on the irradiation behaviour of polycrystalline graphitic materials G. Haag (Kernf_rrschungsanlugeJiilich, GmbH, W. Gennuny). The influence of nongraphitic carbon on the irradiation behaviour of polycrystalline graphitic materials is discussed. Using matrix materials with constant ansiotropy but varying production parameters, it is confirmed that irradiation-induced shrinkage increases with increasing content of disordered carbon. The thermal conductivity also exhibits the influence of the graphitization of disordered carbon by irradiation. 163. Influence of microstructure of irradiation-induced dimensional changes in annealed oriented polycarbons R. J. Price (Guy General Atomic Company, San Diego, California). Highly-oriented massive pyrocarbon was annealed at 2900,3000,3100 and 3300°C and the structure was characterized by X-ray diffraction and transmission electron microscopy. Sample dimensions parallel and perpendicular to the basal plane changed linearly with fast neutron fluence at 1375-1500°C to a maximum fluence of 1.4 X lOaz neutrons/ cm2 (E > 0.18 MeV). Dimensional change rates decreased with increasing annealing temperature. 164. The preparation and characterization of pyrolytic carbon sealants for graphite in power reactors* C. B. Pollock and W. H. Cook (Mean and Ceramics ~~~~, Oak Ridge Nat~~l L~~a~~, Oak Ridge, Tennessee). Graphite was sealed to helium permeabilities of < IO+ cm2/sec by coating with isotropic layers of pyrolytic carbon. Monolayer coatings deposited at temperatures above 1200% from propene and irradiated to a fluence of 1p2 neutrons/cm2 (> 50 KeV) at 700°C have shown satisfactory performance. Duplex-coated specimens are being irradiated. *Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.
165. Irradiation damage to graphite at 1475°C P. A. Thrower and D. D. Burleigh (M&&l Scierrces ~e~~~~, The P~~l~a~a State Un~~~~, Universi5 Park, Penlasylvania). A transmission electron microscope study has been made of pyrolytic graphites of various structures irradiated at 14’75°C. It is concluded that the activation energy governing the nucleation of irradiation damage, which has a value of I.2 eV in the temperature range 150-l35O”C, increases to - 2 eV somewhere between 1350°C and 1475°C. 166. Ultrasonic testing for web integrity in nuclear fuel graphite blocks B. F. Disselhorst (GulfGenemZAtomic Company, San Diego, CalifowLiu). An ultrasonic detection technique used for detecting voids in Fort St. Vrain high-tem~rature nuclear core graphite is discussed. The theory of the acoustical procedure is explained. A method of calibration is described which permits detection and location of continuous voids < O-014 in. in diameter in 3/16-in.-thick graphite webs separating fuel holes from coolant holes. 167. Irradiation hehaviour of gilsocarbon graphites R. Blackstone, Il. J. Veringa (Reactor Centrum Netherlands, Petten, The Netherlands), R. Krefeld (EURATOM, Joint Nuclear Research Centre, Petten, The Netherkds), W. W. Delle, D. L. Leushacke (Kernforschungsadage Jiilich GmbH, W. Germany) and M. R. Everett (Dragon Project, A.E.E. Winfdh, England). As
693
were found to have higher apparent crystallite sizes and smaller Young’s Moduli than low temperature deposits. Under neutron irradiation, the apparent crystallite size tends towards an equilibrium value dependent only on the pre-irradiation apparent density. 161. Development of continuous-matrix fuel rods for advanced high-temperature gas-cooled reactors* R. L. Hamner, J. M. Robbins and J. H. Coobs (Metals and Ceramics I&&ion, Oak Ridge National Laburatory, Oak Ridge, Tennessee). Continuous-matrix graphite elements with particle volume loadings of 30-45 per cent were extruded to close dimensional tolerances at an extrusion rate of 10 ft/min. Similar specimens prepared by slurry blending and warm-molding have withstood irradiation testing to a fast fluence of 7.5 X loZ1 neutrons/cm2 at 115O”C, and extrusions are now being irradiated. *Research sponsored by the U.S. Atomic Energy ~mmission
under contract with the Union Carbide Corporation.
16% The influence of nongraphitic carbon on the irradiation behaviour of polycrystalline graphitic materials G. Haag (Kernf_rrschungsanlugeJiilich, GmbH, W. Gennuny). The influence of nongraphitic carbon on the irradiation behaviour of polycrystalline graphitic materials is discussed. Using matrix materials with constant ansiotropy but varying production parameters, it is confirmed that irradiation-induced shrinkage increases with increasing content of disordered carbon. The thermal conductivity also exhibits the influence of the graphitization of disordered carbon by irradiation. 163. Influence of microstructure of irradiation-induced dimensional changes in annealed oriented polycarbons R. J. Price (Guy General Atomic Company, San Diego, California). Highly-oriented massive pyrocarbon was annealed at 2900,3000,3100 and 3300°C and the structure was characterized by X-ray diffraction and transmission electron microscopy. Sample dimensions parallel and perpendicular to the basal plane changed linearly with fast neutron fluence at 1375-1500°C to a maximum fluence of 1.4 X lOaz neutrons/ cm2 (E > 0.18 MeV). Dimensional change rates decreased with increasing annealing temperature. 164. The preparation and characterization of pyrolytic carbon sealants for graphite in power reactors* C. B. Pollock and W. H. Cook (Mean and Ceramics ~~~~, Oak Ridge Nat~~l L~~a~~, Oak Ridge, Tennessee). Graphite was sealed to helium permeabilities of < IO+ cm2/sec by coating with isotropic layers of pyrolytic carbon. Monolayer coatings deposited at temperatures above 1200% from propene and irradiated to a fluence of 1p2 neutrons/cm2 (> 50 KeV) at 700°C have shown satisfactory performance. Duplex-coated specimens are being irradiated. *Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.
165. Irradiation damage to graphite at 1475°C P. A. Thrower and D. D. Burleigh (M&&l Scierrces ~e~~~~, The P~~l~a~a State Un~~~~, Universi5 Park, Penlasylvania). A transmission electron microscope study has been made of pyrolytic graphites of various structures irradiated at 14’75°C. It is concluded that the activation energy governing the nucleation of irradiation damage, which has a value of I.2 eV in the temperature range 150-l35O”C, increases to - 2 eV somewhere between 1350°C and 1475°C. 166. Ultrasonic testing for web integrity in nuclear fuel graphite blocks B. F. Disselhorst (GulfGenemZAtomic Company, San Diego, CalifowLiu). An ultrasonic detection technique used for detecting voids in Fort St. Vrain high-tem~rature nuclear core graphite is discussed. The theory of the acoustical procedure is explained. A method of calibration is described which permits detection and location of continuous voids < O-014 in. in diameter in 3/16-in.-thick graphite webs separating fuel holes from coolant holes. 167. Irradiation hehaviour of gilsocarbon graphites R. Blackstone, Il. J. Veringa (Reactor Centrum Netherlands, Petten, The Netherlands), R. Krefeld (EURATOM, Joint Nuclear Research Centre, Petten, The Netherkds), W. W. Delle, D. L. Leushacke (Kernforschungsadage Jiilich GmbH, W. Germany) and M. R. Everett (Dragon Project, A.E.E. Winfdh, England). As