Chemistry and Chemical Biology ETDs

Publication Date

10-13-1964

Abstract

Chemical procedures have been developed for the rapid preparation of radiochemically pure europium sources from rare earth mixtures and from fission products. Unpurified mixtures of the mono- and dirp(l,1,3,3- tetramethylbutyl)phenyl 1 esters of orthophosphoric acid are used to ex­tract rare ei1arths in the (III) oxidation state away from europium in the (II) oxidation state. Europium sources can be prepared in about 30 min-11tes.

A slow􀀼r chemical procedure for the preparation of europium sources which are both radiochemically pure and mass free has also been developed. Di(2-ethylhEtxyl) orthophosphoric acid is used to separate europium from yttrium, which has a high fission yield and interferes in the subsequent cation column separation, and from many other fission products. Europium is separated from other rare earths by elution from a cation column "With ammonium -hydroxyisobutyrate solution.

The radiations of Eu 157, Eu158 and Eul.59 have been studied by beta­ray and gamma-ray scintillation spectrometry. The endpoint energies (and intensities􀁦 of the observed major beta groups are l.􀁭 ± 0.10 MeV (401i), 0.93 ± 0.10 MeV (45i) and 0.'71 ± 0.10 MeV (􀁱 15i) for Eu157; 3.40 ± 0.15 MeV (51,), 2.43 ± 0.10 MeV (44i), 1.55 ± 0.10 MeV (􀁱 36i) and 1.2 ± 0.2 MeV (< 15i) for Eui58; 2.40 ± 0.10 MeV and ~1.8 MeV? for Eul.59• The energies in MeV (and, intensities measured at a distance of l centimeter from the detector) of the g8111D8 transitions attributed to Eu157 are o.064 ± 0.00'2 (57%), 0.16 to 0.20 (2i), 0.321 ± 0.004 (3i), 0.373 ± 0.005 (14i), o.411 ± 0.003 (26i), 0.475 ± 0.010 (bi), 0.565 ± 0.010 (􀀁i), 0.621 ± 0.005 (5i), 0.685 :t 0.010 (21,), o. 750 :t 0.010 (1i) and 0.970 ± 0.015 (o.5i). The energies in MeV (and intensities measured at a distance ot 5 centilletera from the detfactor) of the gaana transitions attributed to Eul.!58 are o.oBo ± 0.002 (91i:,, 0.182 :to.􀀹 (4i), 0.525 :t 0.005 {􀀻), o.600 :t 0.005 (6j), o. 750 ± 0.01< ) {5􀀆), o.890 ± o.􀁀o (22j), o.􀁁5 :t 0.010 {56􀀃), 0.995 :to.􀀃 (14i), 1.105 ± 0.010 (􀁇), 1.18 (caaplex, 13j), 1.26 :to.􀁀 {􀀻), 1.33

(complex, 3􀀁), 1.93 :to.􀁀 (4􀀆), 2.16 :t o.oi. (3􀀆) and 2.75 :t 0.05 (l􀀆). The energies in MeV of the g-. tranaitiona attributed to Bu158 are 0.071 ± 0.005, 0.01?6 ± 0.005, 0.120 :t 0.005, 0.148 :t 0.005, 0.225 :t 0.007 and 0.670 ± o.ou>. On the basis of gamma-gamma coincidence measurements, the radiations of Eu157 and of Eu158 have been fitted to partial decay schemes involving the following levels tar Eul.157 : o.o,..,, o.0611-o, o.u,a, 0.1,1,, o.4366, o.47 , 0.685, o. 750 and 0.970{ T) MeV; and the following levels

for Eu158: -o.oBo, o.262, 1.0'25, 1.185, 1.2'7, 1.785, 1.93, 2.ai.. and 2.7'{!) MeV. The total beta decay energies are 1.40 :t 0.13 MeV tor Eul.157, 3.44 :t 0.20 MeV for. Eul.!58 and 2.43 ± 0.13 Mev for Eu159.

The half-lives of five europium and gandolinium nuclides have been measured by following the beta decay of these nuclides. The half-lves are: Eu158 , 15.18 ± 0.10 days; Eu157, 15.16 :t 0.10 hours; Eu1158, 45.7 +- 0.5 minutes; Eul!59 , 17 .9 ± 1.0 minutes; Gdl.59 , 18.'6 +- 0.08 hours. An attempt to determine the half-life of Sm158 by experiments involving periodic chemical separations of Eu158 from fission product samarium was unsuccessful, but an upper limit of 15 minutes for the half-life was established.

The fission yields for Eu156, Eu157, Eu158, and Eu159 for thermal neutron fission of U235 and for 25-MeV He3 fission of U238 have been determined. The thermal fission yields are: Eu158, 0.0125 +- 0.0010%; Eu157, 0.0060 ± 0.00071,; Eu158, 0.0031 ± o.oo061,; Eu159, 0.0011 ± 0.00031,. The 25-MeV He3 fission yields are: Eul.56, 0.27 ± 0.071,; Eu157, 0.13 ± 0.021,;Eu158, o.o89 ± 0.0151,; Eu159, 0.057 ± 0.010.

The mass assignments for 15.16-hour Eu157, 45.7-minute Eu158 and 17.9-minute Eu159 have been confirmed by cross bombardments, radiochemical "milk­ing" experiments, determination of fission yields and total beta decay energies, and comparison of nuclear levels populated by beta decay with those of the same nucleus populated in other ways.

A search has been made for the existence of isomeric states of Eu156, Eu158 and Eu160• Beta decay and gamma scintillation spectra observations on fission product europium and on europium produced by 14-MeV deuteron bombardment of Gdl.58 and of Gd160, 22-MeV bremsstrahlung irradiation ofGd160, and 14-MeV neutron bombardment of Gd158, Gd160 and Tb159 reveal no definite evidence for the existence of isomeric states with half-lives in the range 4 minutes to 70 days for Eu156, 15 minutes to 15 days for Eu158and 5 minutes to 18 hours for Eu160.

Language

English

Document Type

Dissertation

Degree Name

Chemistry

Level of Degree

Doctoral

Department Name

Department of Chemistry and Chemical Biology

First Committee Member (Chair)

Milton Kahn

Second Committee Member

Raymond N. Castle

Third Committee Member

Guido Herman Daub

Fourth Committee Member

J. V. Lewis

Download

Share

COinS