A1I ABSTRACT OF THE THESIS OF Chemical Engineering Roy Alfred Strandberg for the M. S. in Date Thesis presented: April 6, 1951 of Hydrogen Title: Separation of the Principal Isotopes Redacted for privacy Abstract Approved: çIao;P;ofessor, \ investigation The uork herein described concerns an the principal isotopes into tiie feasibility of separating of selective hydrogen, hydrogen and deuterium, by means of investigaton, adsorption. In addition to the separation determined basic data regarding the adsorp- experimentally and an alloy tion of hydrogen and deuterium by zirconium of titanium and zirconium are given. experienta1 equipment and apparatus used during The groups. this investigation consisted of three principal controlled glass The first group contained automatically of gas volume. The cylinders for storage and measurement group included a combustion tube, an automatic second a contin- controlled electric tube furnace, and temper&ture pump. positive displacement mercury gas circulating uous thermal conductivit The third group consisted of a sensitive for gas analysis. Time, combustion tube temper- cell used were contin- gas volume, and gaseous mixture analysis ature, recording instru- uousiy recorded by a converted temperature ment. is The procedure followed during this investigation in the text of the thesis, described the inves- The experimental results obtained during the separation of tae isotopes has tigation concerning basic to the Atomic Energy Commission. The been forwarded as follows. data obtained during the investigation 'ias isobar for the adsorption of hydrogen An atmospheric experi- by zirconium was determined. '1ithin and deuterium adsorbed within mental accuracy, the two gases are equally temperature range investigated. the hydrogen adsorbed A comparison of the results of the investigation and by zirconium as observed during this investigators is shown work previously published by other graphically. isobars for The experimentally determined atmospheric by an alloy of the adsorption of hydrogen and deuterium was found to be zirconium and titanium (35' by wt. Ti) the same within experimental accuracy. approximately for the adsorptior A family of isotherms was obtained of isotherms are deuterium by zirconium. Similar sets of with an alloy of also given for hydrogen and deuterium titanium and zirconium (35% by it. Ti). SEPARATION OF THE PRINCIPAL ISOTOPES OF HYDROGEN by ROY ALFRED STRANDBERG A THESIS submitted to OREGON STATE COLLEGE in partial fulfillment of the requirements for the degree of MPSTER OF SCIENCE June 1951 APP}O7ED: Redacted for privacy Profso> of Chemical Engineering In Charge of Major Redacted for privacy Head of Department of Cernical Engineering Redacted for privacy / -.' Chairman of School Graduate Committee Dean of Graduate School Date thesis is presented April 6, 1951 Typed by Roy A. Strandberg AC KN:ÏLED GiWf S The author is indebted to the Atomic Energy Comniission 'ihose research grant made possible the undertaking of this project. The generous contribution of metal samples by the U. S. Bureau of Mines and the Foote Mineral Company is also appreciated. Sincere thanks is given to Professor Joseph Schulein for his helpful advice and criticism during this inves- tigation. TABLE OF CONTENTS SUBJECT PAGE A. Introduction i B. General Discussion 5 C. Experimental 1. Equipment and apparatus 2. Calibrations 19 3. Procedure 21 4. Accuracy and probable error 24 D. Experimental Results 27 E. Further Investigation 36 F. Bibliography 3 PUTE TITLE PAGE 1. Experimental Apparatus 9 FI GU RES TITLE PAGE 1. Flow Diagram 10 2. Sorption of hydrogen and deuterium by zirconium. 2 3. Comparison of sorption of hydro,cen by zirconium with other investigators. 29 4. Sorption of hydrogen and deuterium by zirconium- titanium alloy (35% by wt. Ti). 31 5. Isotherms for sorption of deuterium by zirconium. 32 6. Isotherms for sorption of deuterium by zirconium- titanium alloy (35% by wt. Ti). 33 7. Isotherms for sorption of hydrogen by zirconium- titanium alloy (35% by iit. Ti). 34 i SEPARATION OF THE PRINCIPAL ISOTOPES OF HYDROGEN INTRODUCTION Deuterium, a heavy isotope of hydroen of mass 2, was reported by Urey, Brickwedde, and Murphy (14, p.l64-l65) in 1932. Their method of concentration of the heavy iso- tope was by evaporation of a large quantity of hydroen to a very small volume. Calculations based upon spectro- graphic analysis showed a concentration of l:OO of heavy hydrogen to ordinary hydrogen in comparison to 1:4000 in the original hydrogen used. Since that time, many investigations have been made in an attempt to find an economical method of separation of the hydrogen isotopes. The principal methods in use today are: the repeated electrolysis of water to a very small volume, fractional distillation, and diffusional methods (4, p.113-131). The investiration herein 'ias an attempt to separate the principal isotopes of hydrogen by means of selective adsorption. The literature reports several facts which made this type of separation appear feasible. Ilany metals interact with hydrogen. The difference between the behavior of the metals with hydrogen has clas- sified them into four distinct groups (2, p.552). Group 1 consists of the alkali and alkaline-earth metals which form true hydrides that are ionic in behavior. 2 Group 2 containing elements such as C, Si, As, Se, S, and some metals in the periodic groups 4B, 511, and 611 form covalent hydrides. Group 3 consisting of metals such as Al, Pt, Ni, Cu, Ag, Mo, W, Cr, Co, and Fe form true solutions with hydro- gen. Group 4 consisting of the metals Ti, Zr, Th, V, Cb, Ta, and the rare earth elements form pseudo-hydrides. Palladium behaves in a similar manner with respect to hydrogen under certain conditions. There are striking differences between the solubility of hydrogen and metals of groups 3 and /. (2, p.572). Metals in group 4 adsorb to iO times as much hydroen as the metals of group 3. At constant pressure, an increase in temperature causes a decrease in solubility of hydrogen in metals of group 4 while causing an increase in solubility in the metals of group 3. Since such large volumes of hydrogen are adsorbed by metals of group 4 and a large percentage of this adsorbed gas can be recovered by increasing the temperature, these metals were used to investigate the possibility of select- ive adsorption between hydrogen and deuterium. Although no information was available to indicate a difference between the adsorption of hydrogen and deut- erium on metals such as titanium and zirconium, information 3 had been published regarding the relative amounts adsorbed for sorie other metals. Sievertz and Zart (11, p.362) reported that the relat- ive solubility of hydroen and deuterium in palladium varied with temperature. The ratio for the solubility of deuterium to that of hydrogen varied from 0.67 at 3000 C to 0.91 at 10000 C. Sievert.z, Zapt, and Moritz (12, p.33) reported the solubility of deuterium in both armco- and carbonyl-iron to vary considerably in comparison to that of ordinary hydrogen. The variations again occurred with changes of temperature. The difference in the value of solubility ranged from 0.1 to 0.9 over the temperature range of 600° C to 1450° C. Sievertz and Moritz (10, p.125) reported that the solubilities of hydrogen and deuterium in columbium to be practically the same. The solubility of deuterium in nickel has been report- ed by Sievertz and Danz (9, p.134) to be approximately 10 percent smaller than that of hydroen in nickel. During the adsorption of a mixture of deuterium and hydrogen on copper, the rate of adsorption of deuterium at -7° C was less than that of hydrogen. Although the rates of adsorption were different, the relative amounts of each gas adsorbed was approximately the same when equilibrium had been attained (1, p.2532). if Eley (3, p.I.62) reported that at 293e K both hydrogen and deuterium are equally adsorbed on a tungsten film and 770 interchange on the film was rapid. At K, the exchange equilibrium was displaced in favor of deuterium so that no interchange was detected between a hydroen-tungsten film and deuterium gas. Another possibility of separa t.ion of the isotopes was that of fractional desorption of the gas mixture from the metal after adsorption had occurred. This possibility was suggested by the successful results obtained by Peters and Lohmar (, p.55) in their investigation of fractional desorption of hydrogen and deuterium on activated ciarcoal by the use of high vacuum. GENERAL DISCUSSION Metals in the group containing titanium and zircon- ium adsorb large quantities of hydro',en. The calculated compositions for these gas-metal sysLems approach stoich- iometric proportions. For zirconium the maximum quantity adsorbed corresponds to ZrH1 92 and for titanium the calculated composition corresronds to Till175 (2, p.573). The term often applied to the zirconium-hydrogen or the titanium-hydrogen system is "hydride", although more recent authors tend to use the term "pseudo-hydride'1. The only basis for this classification is the fact that the heats of adsorption reported for these systems are com- parable to the heats of adsorption given for the hydrides of the alkali and alkaline-earth metals. Beyond this point the similarity between these "pseudo-hydrides" and the true hydrides ceases (2, p.5S). For each temperature and volume of gas held by the metal, these gas-metal systems exhibit a characteristic vapor pressure. Sets of isotherms between the temper- 3750 atures of C and 9430 C have been published by Hall, Martin, and Reese (5, p.310-315). Data of a similar nature were not available for the zirconium-deuterium system. From the isotherms of such a system, data can be obtained to plot the isosteres as log P vs l/T where P refers to the vapor pressure and T to degrees Kelvin.