Enrichment Of Heavy Water Research Articles

Simulation Procedure for Multistage Water/Hydrogen Exchange Column for Heavy Water Enrichment Accounting for Catalytic and Scrubbing Efficiencies

The present paper gives a simulation procedure for multistage water/hydrogen exchange columns for heavy water enrichment using hydrophobic catalysts. The Murphree-type efficiencies for H2O, HDO and D2O are used as the scrubbing efficiencies for sieve trays. The reaction rate of H2+D2↔HD is assumed to be very rapid and equilibrated at the outlet of the catalyst bed. The catalytic efficiencies defined for H2O(g) and D2O(g) are considered for the nonequilibrated exchange reactions: H2+HDO(g)↔HD+H2O(g) and H2+D2O(g)↔D2+H2O(g). Those efficiencies are treated as input variables for the simulation. The main calculational loop is based on the Newton-Raphson iteration, but the order of the Jacobian matrix is just equal to the number of sieve trays for vapor/hydrogen scrubbing. The procedure is applicable to solution of operating problems in a wide range of input and output specifications.

The Enrichment of Heavy Water in a Continuous-Type Inclined Thermal Diffusion Column

Abstract Equations of the best angle of inclination and the maximum separation for the enrichment of heavy water in a continuous-type inclined thermal diffusion column have been derived. Considerable improvement in separation was obtained by employing the inclined column instead of using the Clusius-Dickel column.

Simulation procedure for multistage water/hydrogen exchange column for heavy water enrichment accounting for catalytic and scrubbing efficiencies.

The present paper gives a simulation procedure for multistage water/hydrogen exchange columns for heavy water enrichment using hydrophobic catalysts. The Murphree-type efficiencies for H2O, HDO and D2O are used as the scrubbing efficiencies for sieve trays. The reaction rate of H2+D2↔HD is assumed to be very rapid and equilibrated at the outlet of the catalyst bed. The catalytic efficiencies defined for H2O(g) and D2O(g) are considered for the nonequilibrated exchange reactions: H2+HDO(g)↔HD+H2O(g) and H2+D2O(g)↔D2+H2O(g). Those efficiencies are treated as input variables for the simulation. The main calculational loop is based on the Newton-Raphson iteration, but the order of the Jacobian matrix is just equal to the number of sieve trays for vapor/hydrogen scrubbing. The procedure is applicable to solution of operating problems in a wide range of input and output specifications.

The enrichment of heavy water in a batch-type thermal diffusion column

The separation equations for the enrichment of heavy water in a batch-type thermal diffusion column have been derived for low-concentration operations. The experimental works for various feed concentrations of H 2OHDOD 2O system has been also conducted and the results quantitatively confirm with the prediction of the theory.

A new simulation procedure for multistage water/hydrogen exchange column for heavy water enrichment.

A powerful new simulation procedure is developed for the multistage water/hydrogen exchange column for heavy water enrichment. In comparison with the distillation column, the exchange column considered here has several specific features such as the presence of three streams (liquid water, water vapor and hydrogen gas), occurrence of isotopic exchange reactions and much more complex column configuration comprising two different kinds of stages, a catalytic oxidizer at the top and an electrolytic cell at the bottom. The main calculational loop proposed here is the Newton-Raphson method where the number of independent variables is just equal to the total number of water/vapor scrubbing stages. Unlike the previously reported procedures for the exchange column, the present procedure is applicable even in cases where the deuterium concentration is significantly high, varying greatly from stage to stage within the column.

Theoretical study of three-body nonadditive interactions for the H2S-(H2O)2 system

An ab initio SCF MO study of the hydrogen-bonded system formed by an H2S molecule interacting with two water molecules is presented. The nonadditive contributions to the interaction energies are obtained using the 4-31G basis sets which tend to overestimate the dipole moments of the H2S and H2O molecules. Thus possibly too large interactions, including upper-limit values for the nonadditive three-body contributions, were obtained. The nonadditive corrections were found to be comparable in magnitude to the cases of other first-row hydride trimers. On this basis one can infer that they probably do not affect the proton and deuterium exchange in hydrated H2S (as occurs in the G-S heavy water enrichment process) and that they do not play an important role in the formation of clathrates involving hydrogen sulphide.

Hydrogen Isotope Separation by Catalyzed Exchange Between Hydrogen and Liquid Water

Abstract The discovery, at Chalk River Nuclear Laboratories, of a simple method of wetproofing platinum catalysts so that they retain their activity in liquid water stimulated a concentrated research program for the development of catalysts for the hydrogen-water isotopic exchange reaction. This paper reviews 10 years of study which have resulted in the development of highly active platinum catalysts which remain effective in water for periods greater than a year. The most efficient way to use these catalysts for the separation of hydrogen isotopes is in a trickle bed reactor which effects a continuous separation. The catalyst is packed in a column with hydrogen and water flowing countercurrently through the bed. The overall isotope transfer rate measured for the exchange reaction is influenced by various parameters, such as hydrogen and water flow rates, temperature, hydrogen pressure, and platinum metal loading. The effect of these parameters as well as the improved performance obtained by diluting the hydrophobic catalyst with inert hydrophilic packing are discussed. The hydrophobic catalysts can be effectively used in a variety of applications of particular interest in the nuclear industry. A Combined Electrolysis Catalytic Exchange - Heavy Water Process (CECE-HWP) is being developed at Chalk River with the ultimate aim of producing parasitic heavy water from electrolytic hydrogen streams. Other more immediate applications include the final enrichment of heavy water and the extraction of tritium from light and heavy water. Pilot plant studies on these latter processes are currently in progress.

Laboratory Enrichment of Heavy Water by Electrolysis Part II: Effect of Current Density, Cathode Material, and Temperature on the Separation Factor

The different parameters affecting the electrolytic H-D separation factor were investigated. The separation factor α was found to increase with current density and then attains a constant value. With different α increased in the following way: Phosphated iron > iron > stainless steel > nickel. It was found that α decreased as the temperature increased. Applying Arrhenius equation it was possible to calculate the difference in the free energy of activation for proton and deuteron transfer using different cathodes. Excessive reduction in the volume of electrolyte lowered the separation factor. No marked effect on α was observed by changing the type or concentration of electrolyte.

Optimization of Squared Off Cascade as Applied to Distillation

Some generalized relations were developed with all the necessary cost factors for the design of a distillation plant for the separation of stable isotopes based on the principles of the squared off cascade. These relations, useful for design of a plant for enrichment of an isotope in concentration ranges up to about 5%, were used to design a water distillation plant for the enrichment of heavy water. (auth)

Enrichment of Heavy Water by High Pressure Exchange Between Hydrogen and an Aqueous Catalyst Suspension Part II: Construction and Operation of a Pilot Plant

AbstractThe construction and operation of a pilot plant for the enrichment of heavy water by high pressure exchange between hydrogen and an aqueous catalyst suspension are described. A continous experiment carried out for a period of 86 days proved the technical feasibility of the process and the validity of the assumptions used in an earlier discussion of the economic aspects.

水精溜塔運転に関する2, 3の解析

In operating a water rectification tower for the manufacture of heavy water, it generally takes long hours before it is brought to steady operation from start-up. Consequently it is a matter of economical significance how to shorten the required time to reach the steady operation.An analysis has been made of the transient accumulating operation for heavy water on the following three processes:(1) Enrichment of heavy water by the total reflux method;(2) Enrichment of heavy water by the top feed and reflux method;(3) Enrichment of heavy water by the intermediate feed and reflux method.Regarding the steady operation of the water rectification tower, an analysis has been carried out on the methods related to the total reflux and drain-out rectification and the continuous rectification.

Influence of Liquid Hold-up in Still to the Rate of Approach to Equilibrium of a Packed Distillation Column

The rate of approach to equilibrium of a packed distillation column with finite hold-up of liquid in the still was analysed in a case of top liquid feed, top vapor discharge and no reflux liquid. From the strict results, the following simplified approximate solution was derived.(23) where This equation means that the time required for 99% approach to equilibrium is proportionate to the amount of liquid hold-up in the still and is inversely proportionate to the rate of liquid flow. Prerequisite conditions for the derivation of approximate solution were summerized in Eq.(26) and Eq.(27).An experiment of the enrichment of heavy water in the flow sheet shown in Fig. 5 was conducted under atmospheric pressure. The calculated values by the use of approximate equation showed a fairly good agreement with the observed values, as shown in Fig. 6 and Fig. 7.

水電解工場における副産重水製造法の最適濃縮カスケード

An analysis to get the most economical combination of three methods of heavy water enrichment, such as electrolysis-exchange reaction, distillation, and recovery electrolysis was made under the condition that the heavy water solution, by-product from a normal water electrolysis plant, is available as a raw material. As the result, the following combination was obtained as the optimum enrichment cascade in the case being planned: 4 stages of electrolysis-exchange towers with yields up to 3 wt.% D/sub 2/O; distillation plant with yields from 3 to 28.8 D/ sub 2/O; and recovery electrolysis plant with yields from 28.8 to 99.8 D/sub 2/O. (auth)

Preparation of Heavy Water by Catalytic Exchange

The great advantages of heavy water as a moderator in nuclear reactors have been very largely offset by the difficulties of establishing a satisfactory and economical manufacturing process. This article reviews possible methods of preparation by catalytic exchange, with particular reference to a process, recently developed in Germany, for the enrichment of heavy water by high pressure exchange between hydrogen and an aqueous platinum catalyst suspension.

A Conjectured Electrolytic Enrichment of Tin Isotopes

IT is, of course, a matter of history that a considerable enrichment of heavy water was found in long-used commercial electrolytic cells.

Enrichment of Heavy Water by a Biological Method

IN all methods for the enrichment of heavy water, the first stage is always very expensive, and a slightly enriched feed water could mean a lot in the price of the final product. Some biochemical processes, such as the photosynthesis of Chlorella 1, have been shown to give a small separation between light and heavy water. We have tried to investigate some further possibilities and measured the heavy-water content of water from some industrial biological and microbiological processes.