Multicomponent Isotope Separating Cascade Composed of Elements with Large Separation Factors

Interstage flows are analyzed for multicomponent separating cascades composed of elements with large separation factors. Based on the concept of cut relevant to each component, analysis is performed by extending the theory of binary component separation to multicomponent systems.

Since the cut relevant to each component is expressed by heads and tails separation factors, interstage flows of each component are calculated through giving separation factors of all stages in the cascade. Interstage flows of isotope mixture are obtained by summing those of each component.

A condition on separation factors to construct a “matched abundance ratio cascade” is also discussed in the case where the separation factor does not vary from stage to stage.     

Computer-Aided Simulation Procedure for Water Distillation Columns

A computer-aided simulation procedure is proposed for a water distillation column which has hundreds of stages. The procedure allows us to simulate a column processing all the six molecular species H₂O, HDO, HTO, D₂O, DTO and T₂O. By using the approximation that the isotopie exchange reactions are equilibrated in liquid phase and linearizing the atom balances for two of the three elements (H, D and T) around each stage, the Newton-Raphson iteration is applied to the main calculational loop. As a consequence, the Jacobian matrix has a block tridiagonal form and the order of the arrays is just two even in cases of the six component system. Thus, the serious problem of huge computer storage requirements inherent in previously reported procedures using the Newton-Raphson method is completely eliminated in the present procedure.

The procedure is very useful to the solution of operating problems for water distillation columns used as the upgrader of heavy water from the heavy water reactor and the finisher in the heavy water production process.     

以乙醇为介质气体扩散法分离碳同位素的可行性研究

碳-13作为同位素示踪技术的标记物,应用广泛,市场需求呈上升趋势。为探索碳-13同位素的分离方法,开展以乙醇为介质的气体扩散分离实验,并在单级实验的基础上进行级联计算。单级分离实验的结果表明,在现有的实验条件下,气体扩散法分离乙醇的基本全分离系数可达1.0089,以乙醇为介质扩散分离碳同位素可行。通过级联计算可知,以天然乙醇为原料,结合分离的可行性和经济性,经过一次矩形级联或相对丰度匹配级联分离,能够得到碳-13同位素丰度大于25%的重组分。如能将碳-13同位素丰度大于25%的乙醇转化为合适形态的碳化合物,可再进一步分离得到更高丰度的碳-13同位素。     

Theoretical Analysis of Separating Nitrogen Isotopes by Ion-Exchange, (II)

A method was proposed to precisely simulate the separation of nitrogen isotopes by ion-exchange in the case that the isotopes were confined in a band. In the present paper, the simulation code is developed so as to calculate the case with feed supply and product and waste withdrawal.

The code successfully describes the dynamic behaviors under an appropriate control to obtain the target values of the separation factors and cut which are calculated through cascade analysis. The results of these simulation calculations give the traveling time and the amount of the chemicals for the production of 90% enriched nitrogen isotopes.     

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.     

Observation of H/D isotope effects on polymer electrolyte membrane fuel cell operations

The hydrogen isotope effects upon operation of a polymer electrolyte membrane fuel cell have been observed. The deuterium concentration in the exhaust hydrogen gas from the cell was found lower than that of the hydrogen gas fed to the cell, which indicated that the heavier isotope of hydrogen was preferentially oxidized at the anode. The overall hydrogen isotopic separation factor between the oxidized and non-oxidized hydrogen ranged from 3.46 to 3.99 and increased with decreasing flow rate of the feed gas or increasing rate of hydrogen utilization.