T. Hartmann

The effect of supercritical carbon dioxide treatment on the leachability and structure of cemented radioactive waste-forms

The former process for the cementation of transuranic (TRU) low-level wastes poses several technical problems. Specifically in the US a TRU waste-form has not yet passed the Waste Isolation Pilot Plant prohibition for free liquid. For the reason, treatment of the portland cement based waste-form with supercritical carbon dioxide (SCCO[sub 2]) is shown to satisfy regulations. The effect of SCCO[sub 2] treatment by applying different CO[sub 2] pressure and temperature conditions on the leachability, phase constitution, and microstructure of surrogate-groped portland cement type I/II samples is presented. Leaching studies were performed using a synthetic groundwater leaching procedure. Changes in phase constitution of the major crystalline phases (Ca(OH)[sub 2], CaCO[sub 3]) as well as the microstructure were measured by X-ray diffraction and scanning electron microscopy. SCCO[sub 2] treatment at 8.4 MPa and 25 C can be shown as the most promising conditions to satisfy the requirements of the Department of Transportation (DOT) and to enhance the natural aging reaction of cement paste by carbonation, combined with the lowest release rate of the surrogates [sup 232]Th, and [sup 151/153]Eu.

A comparison between radiation damage accumulation in oxides with pyrochlore and fluorite structures

Abstract Ion irradiation damage experiments were performed on single crystals of the pyrochlore compound Er2Ti2O7 and the fluorite compound Er2Zr2O7. Results indicate that the pyrochlore compound is far more susceptible to defect accumulation and amorphization than the fluorite compound. In particular, Er2Ti2O7 irradiated with 350 keV Xe++ ions succumbs to an amorphization transformation by a fluence of 1 × 1015 Xe/cm2, while Er2Zr2O7 remains crystalline with no change in crystal structure to at least 5 × 1016 Xe/cm2. Atomistic computer simulations were used to explain this difference in radiation damage behavior between compounds with similar structures. Simulations of defect formation energies reveal that point defects induced by irradiation, such as cation antisite and anion Frenkel pairs, are far more stable in the fluorite compound than in the pyrochlore compound.

Measurement of the branching fractions of the radiative charm decays D-0 ->(K)overbar(*0)gamma and D-0 ->phi gamma

We present a measurement of the branching fractions for the Cabibbo-favored radiative decay D^0→K ^(*0) γ and the Cabibbo-suppressed radiative decay D^0→ϕγ. These measurements are based on a data sample corresponding to an integrated luminosity of 387.1  fb^(-1) and recorded with the BABAR detector at the PEP-II e^+e^- asymmetric-energy collider operating at center-of-mass energies 10.58 and 10.54 GeV. We measure the branching fractions relative to the well-studied decay D^0→K^-π^+ and find B(D^0→K ^(*0) γ)/B(D^0→K^-π^+)=(8.43±0.51±0.70)×10^(-3) and B(D^0→ϕγ)/B(D^0→K^-π^+)=(7.15±0.78±0.69)×10^(-4), where the first error is statistical and the second is systematic. This is the first observation of the decay mode D^0→K ^(*0) γ.

Supercritical CO{sub 2} carbonation of cemented radioactive waste-forms: Influence on leachability and structure

The traditional practice of cementing transuranic (TRU) low-level waste poses several technical problems, the most serious of which is that many of the legacy TRU waste-forms do not meet Department of Transportation (DOT) prohibitions on decay heat and/or free liquid. To address these problems, a treatment of cemented waste-forms with supercritical CO{sub 2} (SCCO{sub 2}) has been proposed. This treatment method alters the bulk chemical and structural properties of cast cement by accelerating natural carbonation reactions, while at the same time reducing both free and bound water. Reducing the amount of the hydrogenous content of a cemented waste-form to below 30 wt% simultaneously fulfills the DOT free-liquid requirement and increases the maximum allowable decay heat of the TRU-PACT-II drums by a factor of 4. The effect of SCCO{sub 2} treatment applying different CO{sub 2} pressure and temperature conditions (8.4 MPa < p < 28 MPa, 35 C < T < 62 C) on the leachability, phase constitution, and microstructure of surrogate-doped Portland cement type I/II samples was investigated.

Observation of e(+)e(-)->rho(+)rho(-) near root s=10.58 GeV

We report the first observation of e^+e^- → ρ^+ρ^-, in a data sample of 379 fb^(-1) collected with the BABAR detector at the PEP-II e+e- storage ring at center-of-mass energies near √s = 10:58 GeV. We measure a cross section of σ(e^+e^- → ρ^+ρ^-)= 8:3 ± 0:7(stat)± 0:8(syst) fb within the range of │cosθ^*│ < 0:8 and │ cosθ_±│ < 0:85, where θ^* is the center-of-mass polar angle of the ρ^± meson and θ_± are the angles in the ρ^± rest frame between the direction of the boost from the laboratory frame and the direction of the π^±. Assuming production through single-photon annihilation, there are three independent helicity amplitudes. We measure the ratios of their squared moduli to be │F_(00)│^2:│F_(10)│^2:│F_(11)│^2 = 0:51 ± 0:14(stat) ± 0:07(syst):0:10 ± 0:04(stat) ± 0:01(syst):0:04 ± 0:03(stat) ± 0:01(syst). The │F_(00)│^2 result is inconsistent with the prediction of 1.0 made by QCD models with a significance of 3.1 standard deviations including systematic uncertainties.The authors report the first observation of e{sup +}e{sup -} {yields} {rho}{sup +}{rho}{sup -}, in a data sample of 379 fb{sup -1} collected with the BABAR detector at the PEP-II e{sup +}e{sup -} storage ring at center-of-mass energies near {radical}s = 10.58 GeV. The authors measure a cross section of {sigma}(e{sup +}e{sup -} {yields} {rho}{sup +}{rho}{sup -}) = 19.5 {+-} 1.6(stat) {+-} 3.2(syst) fb. Assuming production through single-photon annihilation, there are three independent helicity amplitudes. They measure the ratios of their squared moduli to be |F{sub 00}|{sup 2} : |F{sub 10}|{sup 2} : |F{sub 11}|{sup 2} = 0.51 {+-} 0.14(stat) {+-} 0.07(syst) : 0.10 {+-} 0.04(stat) {+-} 0.01(syst) : 0.04 {+-} 0.03(stat) {+-} 0.01(syst). The |F{sub 00}|{sup 2} result is inconsistent with the prediction of 1.0 made by QCD models with a significance of 3.1 standard deviations including systematic uncertainties.

Search for B -> K-*nu(nu)overbar decays

We present a search for the decays B -> K-*nu(nu)overbar using 454x10(6)B(B)overbar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We first select an event sample where one B is reconstructed in a semileptonic or hadronic mode with one charmed meson. The remaining particles in the event are then examined to search for a B -> K-*nu(nu)overbar decay. The charged K-* is reconstructed as K*+-> K-S(0)pi(+) or K*+-> K+pi(0); the neutral K-* is identified in K-*0 -> K+pi(-) mode. We establish upper limits at 90% confidence level of B(B+-> K*+nu(nu)overbar>) K-*0 nu(nu)overbar) K-*nu(nu)overbar)< 8x10(-5).We present a search for the decays

Ash Cements Stabilized by Supercritical Co2 Carbonation for Tailings Pond Overlayer

B \to K^{*} \nu \bar{\nu}

Role of antisite disorder on preamorphization swelling in titanate pyrochlores.

using 454

Cation Disorder and Vacancy Distribution in Nonstoichiometric Magnesium Aluminate Spinel, MgO·xAl2O3

\times10^{6}