[en] The isotopic exchange principle has proved effective in increasing air detritiation factors of atmospheric dryers. A CFFTP/AECL Chalk River program has demonstrated detritiation factors of 100,000 in trials. The technology is designed for application on regenerating atmospheric dryers using molecular sieve desiccant beds, used in rooms likely to encounter airborne tritium contamination. Dryer design concepts for dryers at JET (Joint European Torus, England) and ITER have been prepared by Alan Dombra of AECL, using the isotopic exchange technology. The isotopic exchange method works by passing tritiated air over a detritiated desiccant bed. Airborne tritium atoms are exchanged in the bed for ordinary hydrogen atoms from the bed's residual moisture loading. Tritium remains on the bed until it is discharged in a regeneration cycle. During regeneration, the desiccant bed is first heated with hot, dry air to drive off collected tritiated moisture. Airborne tritium removed from the air is collected as a tritiated water distillate and stored for later processing. During the second part of the regeneration cycle, the desiccant bed is washed with clean moist air to elute remaining traces of tritium and to refresh the bed to ready it for another tritium absorption period

[en] The purpose of this chapter was that of mathematically describing exchange behavior under a variety of conditions, outlining the evaluation of exchange rates from experimental data, and illustrating the basic information that could be obtained from such studies. An isotopic exchange process may be followed experimentally by physically or chemically separating the exchanging species and measuring the extent of isotopic redistribution as a function of time. When radioactive tracers are used, the experimental data will express the specific activity of either or both of the exchanging species as a function of time. Homogeneous, complex, and heterogeneous exchange reactions were discussed. 6 figures, 3 tables

[en] Published in summary form only

[en] A plain low cost, procedure for the continuous, low temperature preparation of sodium or potassium hydrides using cheap reagents is presented. Said invention is especially concerned with a process of purifying of a catalytic exchange liquid used for deuterium enrichment, in which an alkali metal hydride is produced as intermediate product. The procedure for producing the sodium and potassium hydrides consists in causing high pressure hydrogen to be absorbed by a mixture of at least a lower monoalkylamine and an alkylamide of an alkali metal from at least one of said amines

[en] The observation of a kinetic selectivity of 290 : 1 in the base-catalyzed H-D exchange of the diastereotopic protons α to the carbonyl group in twistan-4-one is reported. The observation of such a highly selective exchange process clearly shows that the principle of stereoelectronic control can be of major importance in the reaction of an α ketocarbanion

[en] The adsorption and spillover of hydrogen on Pt/TiO₂ have been carried out by using temperature-programmed desorption (TPD) in an ultrahigh-vacuum system. Sequential dosing of hydrogen isotopes at temperatures between 200 and 500 K results in variable isotope exchange, with the desorption for H₂ and D₂ reversed with respect to the dose sequence. This is interpreted in terms of spillover from Pt onto TiO₂ sites. High-temperature oxidation confirms the presence of an intermediate state in the spillover mechanism. Oxygen titration experiments, coupled with the desorption of sequentially dosed isotopes, indicate that desorption of spillover deuterium proceeds by a mechanism involving surface migration back to Pt sites rather than recombination and desorption directly from the oxide. 22 references, 6 figures, 2 tables

[en] In order to evaluate the factors that affect the determination of the isotopically exchangeable phosphorus in soils (L value), various greenhouse experiments were carried out. The following factors were considered: carrier level; plant species; harvest time; nitrogen doses; nitrogen sources; culture conditions and soil type. A radioactive solution with an activity level of approximately 10 μCi ³²p/3 kg soil with different carrier levels was located in layers or mixed completely with the soil depending upon the experiment. (author)

[en] Hydrogen--deuterium exchange kinetics were measured for poly(isopropylacrylamides) over a molecular weight range from 100 to 200,000. A sharp drop in rate appears as soon as one goes from monomer to trimer. Thereafter a very slow progressive decrease is displayed. The local environment of the exchanging amide residue is largely (although not completely) established by the mutual interaction of as few as three residues in these polymers of random conformation. (U.S.)

[en] This patent describes a catalyst for separating isotopes of hydrogen in a process consisting of hydrogen gas and liquid water. In previous inventions the catalyst activity diminished as it came into contact with water. The process described here utilizes a catalyst with a water repellant coating which extends its useful life. (OT)

No abstract available