Liquid Heavy Water Research Articles

A kinetic study of mechanically activated atom exchange: the effect of milling frequency and ball mass.

This study investigates the mechanochemical reaction of hydrogen isotope exchange between solid benzoic acid and liquid heavy water. The systematic change of milling conditions revealed that the reaction rate scales with the milling frequency and the mass of the milling balls. The ball size being always the same, faster reactions stem from the use of higher milling frequencies and heavier balls. The kinetic curves are described by a kinetic model that accounts for the statistical, deformational and chemical factors involved in mechanochemical transformations. The results indicate that the reaction is driven by the generation of a new interface area caused by the deformation of the solid reactants.

High-repetition-rate, multi-MeV deuteron acceleration from converging heavy water microjets at laser intensities of 1021 W/cm2

We demonstrate high repetition-rate deuteron acceleration by irradiating a continuously flowing, ambient temperature liquid heavy water jet with the high-intensity ALEPH laser. The laser delivered up to 5.5 J (120 TW, 1.2 × 1021 W/cm2) laser energy on target at 0.5 Hz. A high repetition-rate Thomson parabola spectrometer measured the deuteron beam energy spectra on each shot for 60 sequential shots (two minutes). Peak fluxes of 5×1010 deuterons/sr/pulse, corresponding to an average flux of 1.5×1012 deuterons/sr/min, were demonstrated with deuteron energies reaching up to 4.4 MeV. High shot-to-shot stability is observed up to 40%–50% of the maximum deuteron energy. These deuteron beams are suited for fast neutron production through deuteron breakup in a converter yielding energies similar to deuteron–deuteron (D–D, 2.45 MeV) fusion reactions of importance for material damage studies.

Shock compression-induced enhancement of stimulated Raman scattering in heavy water

Stimulated Raman Scattering (SRS) of shock-compressed liquid heavy water was observed using a Nd:YAG laser in both the forward and backward directions of the laser beam. SRS spectra exhibited different characteristic features at weak and intense pump energies. As for the intense pump energy, the main SRS peak occurred at approximately 2400 cm −1 and subsequently shifted to a lower frequency. Interestingly, some new peaks were observed in both directions. Specifically, a lower frequency peak close to 2200 cm −1 and 2nd-order anti-Stokes peaks were observed in the backward direction, which further indicated that an ice-VII cubic structure was formed under shock compression conditions. In addition, the normalized intensity ratio of the two main peaks exhibited quite different energy-dependent behaviors. The results demonstrated that the shock-induced high pressure environment significantly enhanced SRS. The results could be attributed to the enhancement effect of Kerr self-focusing and the competitive Backward Stimulated Brillouin Scattering (BSBS) and Forward SRS (FSRS) processes.

Vapour pressure measurements of liquid heavy water in the temperature range between 256 K and 286 K

The thermodynamic properties of heavy water (D2O) are important in industrial applications as well as in the scientific domain, where the understanding of the isotopic effects in aqueous solutions is relevant.In contrast with ordinary water (H2O), comparatively few saturation vapour pressure measurement data of D2O are reported in the literature in the temperature range where heavy water is in its supercooled state and often are provided with a poor or even unknown measurement uncertainty estimate.In this work accurate measurements of the vapour – liquid equilibrium along the saturation line of heavy water over the temperature range from 256 K to 286 K are performed, encompassing a relatively wide temperature range where heavy water is in its supercooled state (256 K–277 K).A comparison between the experimental measurements performed in this work and the available literature data is also carried out along with the recent D2O vapour pressure formulation. Measurement results are discussed and uncertainty sources are estimated.

Thermal conductivity of dissociating water—an ab initio study

The thermal conductivity of partially dissociated and ionised water is calculated in a large-scale study using density functional theory (DFT)-based molecular dynamics (MD) simulations. In doing so, the required heat current of the nuclei is calculated by mapping the effective particle interactions from the DFT-MD simulations onto classical pair potentials. It is demonstrated that experimental and theoretical thermal conductivity data for liquid heavy water and for ice VII are well reproduced with this efficient procedure. Moreover, the approach also allows for an illustrative interpretation of the characteristics of the thermal conductivity in the dense chemically reacting fluid. The thermodynamic conditions investigated here range from densities between 0.2 and 6 g cm−3 and temperatures between 600 and 50 000 K, which includes states highly relevant for understanding the interiors of water-rich planets like Uranus and Neptune and exoplanets of similar composition.

Platinum supported on graphene - PTFE as catalysts for isotopic exchange in a detritiation plant

The catalytic separation of hydrogen isotopes is of particular interest for nuclear industry from the point of view of tritium recovery and its use in fusion reactors. Isotopic exchange may take place in the homogeneous (gaseous) phase or in the heterogeneous phase (hydrogen or gaseous deuterium and water or liquid heavy water). Catalysts are necessary both for the homogeneous phase reaction and the heterogeneous reaction.Recently, graphene and graphene oxides have been investigated as support material due to their excellent physical and chemical properties. The high specific surface, their thermal and chemical stability, high mechanical strength make graphene a potential component in the development of new catalysts that could be used in isotopic exchange. The use of graphene and graphene oxides as support for the active metal has shown an improvement in catalytic activity when compared to the conventional support, degasolination carbon. This behavior may be explained by the high dispersion of active metal on the surface of graphene.The paper presents the preparation of the catalysts that will be used in the future catalytic isotopic exchange experiments (first vapor phase catalytic exchange - VPCE column in order to understand its efficiency in isotopic exchange then the catalysts will be integrated into a liquid phase catalytic exchange LPCE - type laboratory installation and results of BET, SEM and XRD analysis for the prepared powder Pt/graphene oxide and commercial Pt/C in order to highlight the characteristics of the new material. It also shows TGA results for Pt/graphene oxide/PTFE in order to compare the thermal stability of the new prepared catalyst with the previous one.

Influence of the hydrogen bond quantum nature in liquid water and heavy water on stimulated Raman scattering

Stimulated Raman scattering (SRS) of liquid water and heavy water have been investigated using Nd:YAG laser. The SRS spectra of liquid heavy water indicate that ice–VII and ice–VIII structures are formed by shock-induced compression (SIC) in forward and backward directions, respectively. Simultaneously, the SRS spectra reveal of liquid water that only ice-VII structure is formed in the backward direction. The difference in ice structures formed by SIC in liquid water and heavy water could be attributed to the effect of the hydrogen bond quantum nature with H+. SRS spectra of 2M NaOH water solution with ice–VII and ice-VIII structures have been successfully obtained in forward and backward, respectively, as OH− greatly reduce the quantum nature of hydrogen bonds by neutralizing H+ in water. The hydrogen bond quantum nature is important for understanding isotope calibration test structure and isotopic effect.

Application of the CAB evaluation of thermal scattering law for heavy water to ZED-2 critical benchmarks at room temperature

To improve the evaluations in thermal scattering sub-libraries, a set of thermal neutron scattering cross sections (scattering kernels) was developed recently at Centro Atómico Bariloche (CAB) for deuterium and oxygen bound in liquid heavy water, and made available in the ENDF-6 format. These libraries are based on a combination of results of molecular dynamics (MD) simulations and recent experimental data and, when used, result in an improvement of calculations of observables of single neutron scattering experiments, compared to results based on previous evaluations.In this work, we provide additional details on the CAB evaluation of heavy water at room temperature and discuss the important integral characteristics of neutron scattering kernels, such as the cross sections, average scattering cosine, and average secondary energy. Then, the new set of thermal scattering kernels is applied in modelling criticality of the ZED-2 reactor, and the international benchmarks LEU-MET-THERM-003 (ICSBEP handbook) and ZED2-HWR-EXP-001 (IRPhEP handbook) are analyzed in detail. The differences in the estimates of criticality due to changes in the S(α,β) data from the reference one (ENDF/B-VII) to the CAB evaluation are 100–200pcm; they are comparable but smaller than the ZED-2 benchmark uncertainties (≈±300pcm). Changing the reference evaluation of 16O to the recently developed one from the CIELO project (WPEC subgroup 40) results in a decrease of criticality by ∼100pcm. Using different combinations of the improved nuclear data for deuterium, oxygen, and the CAB TSL model, we obtain biases up to 300–400pcm in the estimates of criticality of the selected ZED-2 benchmarks. Application of the new evaluations for 235U and 238U from the CIELO project improves the estimates of keff by decreasing the bias by ∼100pcm that indicates a need for further investigations of the ZED-2 critical assemblies.

Collective dynamics measurement of liquid methanol by inelastic neutron scattering

Collective dynamics of liquid deuterated methanol was studied at room temperature using neutron scattering. The inelastic excitation energy of coherent scattering from liquid deuterated methanol was proportional to the momentum transfer Q in the range of 0.2 to 0.9Å−1; the high-frequency sound velocity of liquid deuterated methanol obtained from the dispersion relation was 1770±30ms−1. The positive dispersion for liquid deuterated methanol was ~60%, about half that of liquid heavy water (~100%) previously reported. This could be reflective of the different number of hydrogen bonds. At Q positions below the first peak in S(Q), the dispersion relation of liquid deuterated methanol derived from neutron scattering was almost identical to that obtained from X-ray scattering. However, the excitation energy obtained from neutron scattering at Q positions above the first peak in S(Q) is larger than that from X-ray scattering, which could be ascribed to intramolecular methanol vibrations.

Vibrational Quantum Decoherence in Liquid Water.

Traditional descriptions of vibrational energy transfer consider a quantum oscillator interacting with a classical environment. However, a major limitation of this simplified description is the neglect of quantum decoherence induced by the different interactions between two distinct quantum states and their environment, which can strongly affect the predicted energy-transfer rate and vibrational spectra. Here, we use quantum-classical molecular dynamics simulations to determine the vibrational quantum decoherence time for an OH stretch vibration in liquid heavy water. We show that coherence is lost on a sub-100 fs time scale due to the different responses of the first shell neighbors to the ground and excited OH vibrational states. This ultrafast decoherence induces a strong homogeneous contribution to the linear infrared spectrum and suggests that resonant vibrational energy transfer in H2O may be more incoherent than previously thought.

Determination of Spectroscopic Band Shapes by Second Derivatives, Part II: Infrared Spectra of Liquid Light and Heavy Water.

Second derivative and band simulation techniques are used in a synergetic relationship to identify components in the infrared (IR) spectra of liquid light and heavy water. Nine Gaussian components are retrieved in massive OH and OD stretch absorption. In this context, ν1 and ν3 are the principal components along with satellites derived from harmonic and combination bands. The Raman spectrum of light water matches the IR components with intensity variations as expected.

Stimulated Raman scattering of lattice translational modes in liquid heavy water

A study was conducted on stimulated Raman scattering (SRS) when laser-induced plasma is formed in heavy water by focusing an intense picosecond pulsed Nd:YAG laser beam with wavelength 532 nm at room temperature. An unexpected 280 cm(-1) low frequency SRS line attributed to the lattice translational modes is observed. This SRS line and the internal-mode SRS lines indicate that the ice VII structure is formed in heavy water under the condition of laser-induced shockwave production.

The Mechanism of the Hydrogen Ion Conduction in Liquid Light and Heavy Water Derived from the Temperature Dependence of Their Limiting Conductivities

The anomalous behavior of liquid water is apparent from the temperature dependence of many experimental properties. Among these are the abnormal high limiting ionic conductivities λ(0) of protons and hydroxyl ions, which in a previous paper we found to depend linearly on the square root of the absolute temperature T(1/2). Here we describe a further study of these conductivities in both light and heavy water, together with the remarkable transition temperature T(0) [242.7 K in H(2)O and 250.5 K in D(2)O], where the supercooled liquid becomes inert and, for example, restricted water molecule rotation is arrested. From T(0) the rotation barrier heights for the two solvents are determined. The conductivity data enable to obtain experimentally the zero point energies of H(+) and D(+) in liquid water, with results in the right order of magnitude as compared to values estimated along quantum mechanical routes. Contrary to general opinion, the isotope effect λ(0)(H(+))/λ(0)(D(+)) is temperature dependent, its value being close to 2(1/2) only near 20 °C. The isotope effect λ(0)(OH(-))/λ(0)(OD(-)) also takes temperature dependent values, substantially higher than 2(1/2). Still, the linear relationships with T(1/2) sustain a model based on water rotation control for the conductivity mechanism. For a quantitative analysis, the rotation frequency ω is expressed by a simple linear function of T(1/2) in terms of the moment of inertia I and the quantity T(0)(1/2). This "ab initio" calculation is found to be in perfect agreement with theoretical and experimental data in the literature, when ω is identified with the reciprocal of the so-called single molecule relaxation time τ(s). The data analysis eventually leads to the conclusion that the hydrogen ion transfer between water molecules proceeds via two parallel pathways. Next to the rotation controlled hopping mechanism there exists a temperature independent transfer controlled by tunnelling, occurring at all relative orientations of the participating water molecules. The applicability of the excess conductivity concept for hydrogen and hydroxyl ions is critically discussed.

Study of Temperature Effect on Far-Infrared Spectra of Liquid H2O and D2O by Analytical Theory and Molecular Dynamic Simulations

The results of a combined study of dielectric loss (epsilon"(nu)) and power-absorption coefficient (alpha(nu)) are reported. The epsilon"(nu) and alpha(nu) values are obtained for liquid water (H2O) and heavy water (D2O) using analytical modeling and the molecular dynamics (MD) simulations method. The calculated spectra span the microwave and far-infrared (FIR) region. The temperature range probed is 220-355 K. Appropriate parametrization of the analytical model for liquid water enables the quantitative description of the dielectric spectra over the frequency range of 0-1000 cm-1. An excellent agreement between the calculated spectra and the experimental data demonstrates the accuracy of the applied analytical approximations. The spectra obtained using the MD simulations agree rather qualitatively with the experimental epsilon"(nu) and alpha(nu) dependences. The observed spectra are interpreted in terms of four molecular mechanisms that have been recently described [J. Phys. Chem. A 2006, 110, 9361].

Polarized infrared microspectroscopy of single spruce fibers: Hydrogen bonding in wood polymers

We studied wood polymers in their native composite structure using mechanically isolated single spruce (Picea abies [L.] Karst.) fibers. Dichroic infrared spectra of fibers placed in a custom-built microfluidic cuvette were acquired in air, in liquid (heavy) water, and in liquid dimethylacetamide using a novel combination of synchrotron-based Fourier transform infrared microspectroscopy with polarization modulation. Differences were observed in the O-H stretching frequency region of the spruce spectra upon changing the ambient conditions. Analysis of these spectral variations provides information on hydrogen bonding, orientation, and accessibility of structural units of the wood polymers in the spruce cell walls. Our in situ approach contributes to a further understanding of the structural details of wood polymers in their native setting.

Hyperspectral temperature and salt dependencies of absorption by water and heavy water in the 400-750 nm spectral range

The temperature and salt dependencies of absorption by liquid water (H2O) and heavy water (D2O) were determined using a hyperspectral absorption and attenuation meter (WET Labs, AC-S). Sodium chloride (NaCl) was used as a proxy for seawater salts. There was no significant temperature (PsiT) or salt (PsiS) dependency of absorption at wavelengths <550 nm. At wavelengths >550 nm, PsiT exhibited peaks at approximately 604, 662, and 740 nm. A small negative trough in PsiS occurred at approximately 590 nm, followed by a small positive peak approximately 620 nm, a larger negative trough at approximately 720 nm, and a strong positive peak at approximately 755 nm. The salt dependency of absorption by heavy water, Psis(H), exhibited a negative power-law shape with very low Psis(H), at wavelengths >550 nm. Our experiments with NaCl, clean open ocean seawater, and artificial seawater support the hypothesis that salts modify the absorption spectra of seawater by modifying the molecular matrix and vibrations of pure water.

LOCATING TRITIUM SOURCES IN A RESEARCH REACTOR BUILDING

Despite renovation of the D2O facility, tritium concentrations in the condensates of reactor room air showed tens of Bq mL before venting resumption on July 1997. This suggested the presence of tritium sources in the research reactor-containment building. An investigation was therefore initiated to locate the source and determine the distribution of tritium in the containment building. Air monitoring in the working area using a dish of water placed in the building suggested that the source of tritium was near the reactor core. Monitoring exhaust air from the two facilities (a cold neutron source and a D(2)O tank) showed high specific activity on the order of 10 Bq mL(-1), suggesting the presence of tritium in condensates near the reactor core. The major concern was whether the leakage of liquid deuterium (4 L) and heavy water (2 x 10(3) L) used as a moderator had occurred. The concentration of tritium in condensates has not increased over the past few years in either the exhaust line or working area, and the deuterium itself has not been found in the surrounding environment. The concentration of tritium measured using an ionization chamber after Ar decay was dependent on the thermal output of the research reactor, indicating that the tritium was produced by the irradiation process within shielding/moderator materials or cover gas with neutrons.

Pretransitional scaling close to a double critical point in a potassium laurate, 1-decanol, and heavy water lyotropic liquid crystal.

Light scattering measurements were done close to the double critical point of the isotropic boundary of the lyotropic liquid crystal potassium laurate, 1-decanol, and heavy water. From scaling analysis we find susceptibility and correlation length exponents that are clearly higher than the mean-field values usually found in other studies on this and similar systems. In order to recover mean-field analysis, we use a parabolic version of the Landau-de Gennes free energy in account of the convex nature of the phase diagram. We also observe pretransitional characteristic domain sizes greater than the correlation length. Furthermore, we show that the transition goes into a new two-phase coexistence region, between the convex tips of pure isotropic and discotic nematic boundaries.

Possibility of breakdown of overdamped and narrowing limits in low-frequency Raman spectra: phenomenological band-shape analysis using the multiple-random-telegraph model.

Depolarized low-frequency Raman spectra of liquid water and heavy water are investigated from 266 K to 356 K. The reduced Raman spectra below 250 cm(-1) are reproduced by a superposition of one relaxation mode and two damped harmonic oscillator modes. The multiple-random-telegraph (MRT) model, which takes into account inertia and memory effects, is applied to analyze the relaxation component. Two damped harmonic oscillators around 50 cm(-1) and 180 cm(-1) are known as a bendinglike mode and a stretchinglike mode, respectively. It is found that the intensity of the bendinglike mode in water (heavy water) gradually decreases with increasing temperature, and finally vanishes above about 296 K (306 K). The relaxation time of the MRT model is interpreted as representing the averaged lifetime of the vibrating unit. At high temperature, the relaxation time becomes short, that is to say, the vibrating unit is quickly destroyed before the 50 cm(-1) mode is oscillating sufficiently. In the present analysis, the strongly disrupted oscillation cannot be distinguished from the relaxation mode which includes the inertia and memory effects. It is found that the low-frequency Raman spectrum of liquid water at high temperature is a good example demonstrating an application of the MRT model.

Sonoluminescence in heavy water

We have performed an experiment on sonoluminescence in liquid heavy water. We have verified that sonoluminescence takes place with air bubbles as well as with D2 bubbles in heavy water (98.5% D2O). No radioactivity originating from the phenomenon has been observed.