F. O. Lawrence

Half-life of 238Pu☆

Abstract The half-life of 238 Pu has been measured by determining its rate of growth from 242 Cm. The weighted average of two determinations is 86·41 years, with an estimated error of 0·3 year.

Radiochemical purification of tin and the half-lives of 121Sn, 123Sn, 125Sn and 125Sb☆

Abstract A procedure is given for the separation and radiochemical determination of tin isotopes in uranium fission product mixtures at least 2 days old. The half-lives of 121Sn, 123Sn, 125Sn and 125Sb were determined to be 26·85 ± 0·20 hr, 129·0 ± 0·5 days, 9·625 ± 0·025 days and 2·81 ± 0·05 years, respectively.

Half-life of Pu236☆

Abstract The half-life of the alpha emitter, Pu236, was measured by a direct decay method. Corrections were applied for the alpha-emitting daughters of Pu236. The results of three sets of data were: 2·855 yr, s = 0·009 yr; 2·817 y, s = 0·04 yr; 2·836 yr, s = 0·021 yr. The weighted average is 2·851 yr with s = 0·008 yr.

Decay of 24 min 146Pr

Abstract The radiations associated with the β-decay of 24 min 146 Pr have been studied with Ge(Li), Si(Li), NaI(Tl) and trans -stilbene detectors. Gamma-gamma and gamma-beta coincidence experiments were performed, and gamma-gamma directional correlations were measured for the 1.525–0.454 MeV cascade. The observation of a 3.6 MeV β-group in coincidence with the 0.454 MeV photopeak establishes the total β-disintegration energy of 146 Pr as 4.1±0.1 MeV. The β-ray spectrum is complex with an end-point energy of 4.1±0.2 MeV. The intensity of the 0.454 MeV γ-transition per β-disintegration was found to be 0.49, and the intensities of some 40 other γ-rays were determined. Most of these γ-transitions have been placed in the 146 Nd level scheme which includes excited states with energies has high as 3.819 MeV. The present data appear to be consistent with an assignment of either 1 − or 2 − for the ground state of 146 Pr.

Decay of 243Pu

The radiations associated with the β-decay of 4.96 h 243Pu have been studied with Ge(Li) and Si(Li) detectors and krypton- and xenon-filled proportional counters. Conversion electron lines of the more intense γ-transitions have been measured and tentative multipolarities have been assigned. A decay scheme incorporating some 20 γ-transitions is presented. The Nilsson assignments of 72+[624] for 243Pu and 52−[523] for 243Am are substantiated by the present data. The total β-disintegration energy of 243Pu is 580 ± 10 keV.

Sorption and Migration of Radionuclides in Geologic Media

The interactions of a quartz monzonite, an argillite, an alluvium, and several tuffs with various radionuclides in selected phreatic waters have been studied. The sorption--desorption hehavior of Sr, Tc(VII), Cs, Ba, Ce, Eu, U(VI), Pu, and Am under ambient and 70{sup 0}C temperature conditions has been measured.

Decay of 245Pu

Abstract The radiations associated with the β-decay of 10.5 h 245 Pu have been studied with Ge(Li) and Si(Li) detectors, a xenon-filled proportional counter and conventional NaI(Tl) scintillators used in singles and coincidence configurations. The β-ray spectrum is complex with a 1210±40 keV end-point energy. The most intense group has a 930±30 keV end-point energy. Conversion electron lines of the more intense γ-transitions have been measured and tentative multipolarities have been assigned. A total of 70 γ-rays was observed in Ge(Li) singles spectra, and most of these transitions have been included in the 245 Am level scheme, which includes excited states at 19, 28, 47, 70, 87, 124, 134, 327, 396, 475, 757, 796, 887, 920, 958, 988, 1066, 1112 and 1185 keV. The present data are consistent with spin and parity assignments of 9 2 − for 245 Pu and 5 2 + for 245 Am. The total β-disintegration energy of 245 Pu is 1.26±0.03 MeV.