[en] A method of reducing the ultrasonic noise, or spurious echos, often present in austenitic metals has been developed. The method has been used on specimens of Type 316 stainless steel, Alloy 800, 16-8-2 weld metal, and Inco-82 type weld metal. The method has been applied to shear wave tests and is applicable to longitudinal wave tests. Noise in these materials has been subsequently reduced relative to saw cut notches in welded samples. Signal-to-noise improvements of 8Db have been achieved in 16-8-2 weld metal, and order of magnitude improvement is obtained in the probability of large noise signals per inspection. Experiments with 1 and 1/2 megahertz inspection indicate that the improvement attributed to longitudinal wave inspection may be due to the difference in wavelength rather than wave mode

[en] Under the direction of the Department of Energy's (DOE) Office of Civilian Radioactive Waste Management (OCRWM) program, the Nevada Nuclear Waste Storage Investigations (NNWSI) project is evaluating a candidate repository site at Yucca Mountain, Nevada, for permanent disposal of high-level nuclear waste. The Lawrence Livermore National Laboratory (LLNL), a participant in the NNWSI project, is developing waste package designs to meet the NRC requirements. One aspect of this waste package is the nondestructive testing of the final closure of the waste container. The container closure weld can best be nondestructively examined (NDE) by a combination of ultrasonics and liquid penetrants. This combination can be applied remotely and can meet stringent quality control requirements common to nuclear applications. Further development in remote systems and inspection will be required to meet anticipated requirements for flaw detection reliability and sensitivity. New research is not required but might reduce cost or inspection time. Ultrasonic and liquid penetrant methods can examine all closure methods currently being considered, which include fusion welding and inertial welding, among others. These NDE methods also have a history of application in high radiation environments and a well developed technology base for remote operation that can be used to reduce development and design costs. 43 refs., 23 figs., 3 tabs

[en] An improved probe for in-service ultrasonic inspection of long lengths of a workpiece, such as small diameter tubing from the interior, utilizes a conventional transducer or transducers configured to inspect the tubing for flaws and/or wall thickness variations. The probe utilizes a hydraulic technique, in place of the conventional mechanical guides or bushings, which allows the probe to move rectilinearly or rotationally while preventing cocking thereof in the tube and provides damping vibration of the probe. The probe thus has lower friction and higher inspection speed than presently known probes

[en] Ultrasonic examination and inservice inspection of transition joints between 2 1/4Cr-1Mo and Type 316 stainless steel is described for liquid metal fast breeder reactor applications. The detection of creep fatigue cracks as small as 0.5% of the pipe wall thickness in the 2 1/4Cr-1Mo heat affected zone was demonstrated. The detection of 3% artificial defects in the heat affected zone of the austenitic materials was demonstrated; 8-10% artificial defects in the weld metal were also detectable. These sensitivities required a weld shaved smooth (surface finish better than 250 microinches AA) on both surfaces and the use of signal processing in the austenitic weld metal. The inspection capabilities have been demonstrated in the laboratory and in the U.S. Department of Energy's transient test facility at the Energy Technology Engineering Center

[en] Cyanogen had been found to be an inhibitor of some carbonic anhydrases. This inhibition was accompanied by formation of 1 GLU-HIS link and no covalent incorporation of C₂N₂ into the protein. The authors report here that C₂N₂ induces inter-molecular cross-links in lysozyme, inter-subunit cross-links in Hb and chromatin, and intramolecular cross-links in several proteins. No significant amount (<14C-C₂N₂ was incorporated in any case examined to date. Most of the cross-links involve omega-COOH of GLU and ASP with epsilon-NH₂ of LYS. Individuals exposed to C₂N₂ through smoking show antibodies to in vitro C₂N₂ treated proteins (with L. Bernstein). In general, model amine carboxylates do not give a trace of amide bond formation under physiological conditions: with reactants in H₂O or a variety of organic solvents. However, omega-amino carboxylates including dipeptides such as PRO-PRO cyclize in 10's of seconds. Bimolecular condensation to form peptides occurs in pyridine at high reactant concentrations and low T. The authors conclude that C₂N₂ drives a carbodiimide like condensation with a preformed salt-bridge complex shielded to some extent from H₂O

[en] Synroc specimens doped individually with approximately1 wt% of Np or Pu have been studied, after leaching for >2,500 days, using α-spectroscopy and SEM. In the last leaching period, the leachant was replaced on either a daily or monthly basis. When the leachant was replaced on a daily basis the release rate of Np was similar to that measured when the samples were first leached, whereas for the monthly replacement the release rates of Np or Pu were about a factor of 20 to 30 lower than that for daily replacement. These findings agree generally with the results obtained from surface examination of the samples which showed that the thickness of actinide-depleted surface layer of anatase was 0.3 microm for monthly replacement but only 0.1 microm when the leachant was replaced frequently. Overall, the results suggest that release of actinides from Synroc are controlled by solubility limiting effects at the surface area to volume ratios employed in MCC-1 tests

[en] Ultrasonic testing of the Clinch River Breeder Reactor Steam Generator tubing has been performed to high sensitivity, using unique calibration procedures. The procedure is more explicit than conventional methods and provides a level of statistical ''risk'' to the test. Reinspection of a small lot of production tubing as an overcheck was statistically analyzed to estimate the frequency of flaws of a given equivalent amplitude. A comparison was made between conventional and statistically controlled tests. The probability of a rejectable size flaw per length of tube was not significantly different for the two types of tests. 10 refs

[en] Betafite and zirconolite occur in Ti-rich hydrothermal veins emplaced within dolomite marble in the contact aureole of the Adamello batholith, northern Italy. Zirconolite contains up to 18 wt% ThO₂ and 24 wt% UO₂, and exhibits strong compositional zoning. Some zirconolite grains were corroded by the hydrothermal fluid. Betafite, the Ti-rich member of the pyrochlore group, often occurs as overgrowths on zirconolite. The betafite is weakly zoned and contains 29--34 wt% UO₂. In terms of end-members, betafite contains approximately 50 mole percent CaUTi₂O₇ and is the closest known natural composition to the pyrochlore phase proposed for use in titanate waste forms. Amorphization and volume expansion of the betafite caused cracks to form in the enclosing silicate mineral grains. Backscattered electron images reveal that betafite was subsequently altered along crystal rims, particularly near the cracks. EPMA data reveal little difference in composition between altered and unaltered areas, except for lower totals, suggesting that alteration is primarily due to hydration. The available evidence demonstrates that both betafite and zirconolite retained actinides for approximately 40 million years after the final stage of vein formation. During this time, betafite and zirconolite accumulated a total alpha-decay dose of 3--4 x 10¹⁶ and 0.2--2 x 10¹⁶ α/mg, respectively

[en] New diffraction and microstructural data on the incorporation of rare earths, Np and Pu in nominally single-phase zirconolite (CaZrTi₂O₇) are presented. Such data are vital for the crystal-chemical design of zirconolite-rich titanate ceramics of the Synroc family, for the immobilization of up to 30 wt% of actinide wastes from advanced reprocessing/partitioning schemes. Some trial zirconolite-rich ceramics were made with U and Nd simulating tetravalent and trivalent actinides respectively. Some preliminary results to examine chemical flexibility with regards to variations in waste/precursor are given, for different actinide waste compositions

[en] The immobilization of excess weapons plutonium into Synroc yields wasteforms that satisfy the key criteria of the U.S. National Academy of Sciences for geological disposal. Synroc-C with a ¹³⁷Cs spike to provide an internal radiation barrier can immobilize up to about 12wt.% PuO₂ as well as adequate amounts of Gd₂O₃ and HfO₂ as neutron absorbers to limit risks of nuclear criticality. New results are presented on zirconolite-rich Synroc that has the potential to accept up to about 20 wt.% PuO₂ if the internal radiation barrier is not included. An external radiation barrier to improve diversion resistance can be utilized with the can-in-canister concept. The implications of the various radiation barriers on processing and eventual geological disposal of Pu-rich Synroc wasteforms are discussed briefly