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Kinetics of fission product release prior to fuel slumping

Description: This paper describes the primary physical/chemical models recently incorporated into a mechanistic code (FASTGRASS) for the estimation of fission product release from fuel, and compares predicted results with test data. The theory of noble gas behavior is discussed in relation to its effect on the release behavior of I, Cs, Te, Ba, and Sr. The behavior of these fission products in the presence of fuel liquefaction/dissolution and oxidation grain-growth phenomena is presented, as is the chemistry of Sr, Ba, I, and Cs. Comparison of code predictions with data indicates the following trends. Fission product release behavior from solid strongly depends on fuel microstructure, irradiation history, time at temperature, and internal fuel rod chemistry. Fuel liquefaction/dissolution, fracturing, and oxidation also exert a pronounced effect on release during fuel rod degradation. For very low burnup fuel appreciable fission product retention in previously liquefied fuel can occur due to the low concentration of fission products, and the limited growth of bubbles in the liquefied material. 24 refs., 13 figs., 9 tabs.
Date: October 1, 1987
Creator: Rest, J.
Partner: UNT Libraries Government Documents Department

Positron-annihilation 2D-ACAR studies of disordered and defected alloys

Description: Theoretical and experimental progess in connection with 2D-ACAR positron annihilation studies of ordered, disordered, and defected alloys is discussed. We present, in particular, some of the recent developments concerning the electronic structure of disordered alloys, and the work in the area of annihilation from positrons trapped at vacancy-type defects in metals and alloys. The electronic structure and properties of a number of compounds are also discussed briefly; we comment specifically on high T/sub c/ ceramic superconductors, Heusler alloys, and transition-metal aluminides. 58 refs., 116 figs.
Date: September 1, 1987
Creator: Bansil, A.; Prasad, R.; Smedskjaer, L.C.; Benedek, R. & Mijnarends, P.E.
Partner: UNT Libraries Government Documents Department

Geochemical modeling research related to the surface disposal of processed oil shale solid waste. [Elements and compounds in oil shale wastes]

Description: Several geochemical codes are available in the literature to model chemical processes such as oxidation-reduction, precipitation-dissolution, formation of solution complex, adsorption, and ion exchange. However, these models differ in the environments to which they apply. The objective of this research was to evaluate the applicability of existing geochemical codes to predict water quality from an oil shale solid waste environment. We selected EQ3/EQ6, GEOCHEM, MINTEQ, PHREEQE, SOLMNEQ, and WATEQFC geochemical models for further evaluation. We concluded that all these models lack thermodynamic data for minerals and solution complexes which are important for oil shale solid waste studies. Selection of any one of the models would require development of a more reliable thermodynamic database, and this report describes the initiation of that work. So far, critical evaluation of thermodynamic data has been completed for Sr, F, Mo, and Se. 64 refs., 15 tabs.
Date: October 1, 1987
Creator: Reddy, K. J. & Drever, J. I.
Partner: UNT Libraries Government Documents Department

Comparisons of VUU (Vlasov-Uehling-Uhlenbeck) predictions with streamer chamber data

Description: Experimental charged particle inclusive and exclusive parameters for several nuclear systems are compared with microscopic model predictions based on the Vlasov-Uehling-Uhlenbeck equation, for various density-dependent nuclear equations of state (EOS). Inclusive variables and multiplicity distributions are in good agreement, and are not sensitive to the EOS. Rapidity spectra show evidence of being useful in determining whether the model uses the correct sections for binary collisions in the nuclear medium, and whether momentum dependent interactions are correctly incorporated. Sideward flow parameters do not favor the same nuclear incompressibility at all multiplicities, and there are indications that the present model may provide only an upper limit on the true stiffness of the EOS. Findings relating to impact parameter averaging and the mass and energy dependence of transverse flow are also presented. 24 refs., 6 figs., 1 tab.
Date: January 1, 1987
Creator: Keane, D.; Chu, S.Y.; Fung, S.Y.; Liu, Y.M.; Qiao, L.J.; VanDalen, G. et al.
Partner: UNT Libraries Government Documents Department

Defect structures in YBa/sub 2/Cu/sub 3/O/sub 7-x/ produced by electron irradiation

Description: Defect structures in YBa/sub 2/Cu/sub 3/O/sub 7-x/ produced by electron irradiation at 300/sup 0/ K were investigated by transmission electron microscopy. Threshold energies for the production of visible defects were determined to be 152 keV and 131 keV (+- 7 keV) in directions near the a and b (b > a) axes (both perpendicular to c, the long axis in the orthorhombic structure), respectively. During above threshold irradiations in an electron flux of 3 x 10/sup 18/ cm/sup -2/ s/sup -1/, extended defects were observed to form and grow to sizes of 10 to 50 nm over 1000 s in material thicknesses 20 to 200 nm. Such low electron threshold energies suggest oxygen atom displacements with recoil energies near 20 eV. The observation of movement of twin boundaries during irradiation just above threshold suggests movement of the basal plane oxygen atoms by direct displacement or defect migration processes. Crystals irradiated above threshold were observed after about 24 hours to have transformed to a structure heavily faulted on planes perpendicular to the c axis. 3 refs., 3 figs.
Date: December 1, 1987
Creator: Kirk, M.A.; Baker, M.C.; Liu, J.Z.; Lam, D.J. & Weber, H.W.
Partner: UNT Libraries Government Documents Department

The EPRI Laboratory experiments at ANL. [Vaporization of core-concrete mixtures]

Description: The vaporization of core-concrete mixtures is being measured using a transpiration method. Mixtures of stainless steel, concrete (limestone or basaltic) and urania (doped with La/sub 2/O/sub 3/, SrO, BaO, and ZrO/sub 2/) are vaporized at 2150 - 2400 K from a zirconia crucible into flowing He - 6% H/sub 2/ gas. Up to 600 ppM H/sub 2/O is added to the gas to fix the partial molar free energy of oxygen in the range -420 kJ to -550 kJ. The fraction of the sample that is vaporized is determined by weight change and by chemical analyses on the condensates that are collected in an Mo condenser tube. The results are being used to test the thermodynemic data base and the underlying assumptions of computer codes used for prediction of release during the severe accident. 13 refs., 2 tabs.
Date: October 28, 1987
Creator: Roche, M.F.; Settle, J.L.; Leibowitz, L.; Johnson, C.E. & Ritzman, R.L.
Partner: UNT Libraries Government Documents Department

Radiation damage in YBa/sub 2/Cu/sub 3/O/sub 7/ by fast neutrons

Description: The superconducting transition temperature of sintered YBa/sub 2/Cu/sub 3/O/sub 7/ decreases at a rate of 2.7 K/10/sup 18/ n/cm/sup 2/ (E > 0.1 MeV) for fast neutron irradiation. The critical current density J/sub c/ increases a factor of three at zero field and more than three at nonzero fields for fluences up to 2 x 10/sup 18/ n/cm/sup 2/. At both 7 and 75 K, J/sub c/ is decreasing with fluence near 3 x 10/sup 18/ n/cm/sup 2/.
Date: January 1, 1987
Creator: Willis, J.O.; Cost, J.R.; Brown, R.D.; Thompson, J.D. & Peterson, D.E.
Partner: UNT Libraries Government Documents Department

Resistivity of EuBa/sub 2/(Cu/sub 1-y/Zn/sub y/)/sub 3/O/sub x/ as a function of temperature, magnetic field, pressure and Zn concentration

Description: We report electrical resistance and magnetoresistance measurements on EuBa/sub 2/(Cu/sub 1-y/Zn/sub y/)/sub 3/O/sub x/ under pressure to 17 kbar. With Zn substitution, T/sub c/ is depressed rapidly (approx.19 K/at.% Zn) and there are qualitative changes in the temperature and field response of the resistance. Pressure drives the Zn-substituted samples toward undoped EuBa/sub 2/Cu/sub 3/O/sub x/ behavior. Analysis of the temperature dependent resistance for y = 0.05 and P = O, together with Hall effect and thermopower data, suggests that the suppression of superconductivity may arise from weak three-dimensional localization promoted by Coulomb interactions.
Date: January 1, 1987
Creator: Borges, H.A.; Wells, G.L.; Cheong, S.W.; Kwok, R.S.; Thompson, J.D.; Fisk, Z. et al.
Partner: UNT Libraries Government Documents Department

Actinide removal from aqueous solution with activated magnetite

Description: An actinide aqueous waste treatment process using activated magnetite has been developed at Rocky Flats. The use and effectiveness of various magnetites in lowering actinide concentrations in aqueous solution are described. Experiments indicate that magnetite particle size and pretreatment (activation of the magnetite surface with hydroxyl ions greatly influence the effective use of magnetite as an actinide adsorbent. With respect to actinide removal, Ba(OH)/sub 2/-activated magnetite was more effective over a broader pH range than was NaOH-activated magnetite. About 50% less Ba(OH)/sub 2/-activated magnetite was required to lower plutonium concentration from 10/sup -4/ to 10/sup -8/ g/l. 7 refs., 8 tabs.
Date: August 10, 1987
Creator: Kochen, R.L. & Thomas, R.L. (ed.)
Partner: UNT Libraries Government Documents Department

Experiments on heavy electron and high T/sub c/ oxide superconductors. [Gd-doped (U,Th)Be/sub 13/; RBa/sub 2/Cu/sub 3/O/sub 7/]

Description: In the first part of this paper, we briefly describe some of our efforts to determine the type of pairing and pairing mechanisms that are associated with the superconductivity of heavy electron materials by means of H/sub c2/(T) measurements in Gd-doped (U/sub 1-x/Th/sub x/)Be/sub 13/ alloys. An account of some of our recent work on the new high T/sub c/ copper oxide superconductors is given in the second part of the paper. 30 refs., 12 figs.
Date: January 1, 1987
Creator: Maple, M.B.; Dalichaouch, Y.; Ferreira, J.M.; Hake, R.R.; Lambert, S.E.; Lee, B.W. et al.
Partner: UNT Libraries Government Documents Department