Teruaki Nagahara

Decay properties of 145Ce and 146Ce

Abstract γ-ray singles, γ-γ coincidence, s-ray singles, β-γ coincidence and half-life measurements have been performed to study decay properties of 145Ce and 146Ce by using a rapid paper electrophoresis. Thirty-two γ-rays from 145Ce, including 14 new ones, and 26 γ-rays from 146Ce, including 6 new ones, were observed, and 25 γ-rays and 21 ones were assigned to the decay schemes for 145Ce, including 3 new levels and for 146Ce, respectively. The half-lives of 145Ce and of 146Ce are 3.01 ± 0.06 and 13.52 ± 0.13 min, and observed Qβ values for 145Ce and for 146Ce are 2.6 ± 0.1 MeV and 952 ± 50 KeV, respectively.

Decay studies of 143La and 147Pr

Abstract The decay properties of 143 La and 147 Pr were investigated with Ge(Li), NaI(Tl) and plastic detectors in singles and coincidence modes with the help of a rapid paper electrophoresis. Twenty-three new γ-rays for 143 La and 9 new transitions for 147 Pr were observed and fairly precise decay schemes for 143 La including 5 new levels and for 147 Pr including 4 new levels were proposed. The half-lives of 143 La and 147 Pr are 14.14 ± 0.16 and 13.3 ± 0.4 min, and observed Q β values for 143 La and 147 Pr are 3.28 ± 0.10 and 2.77 ± 0.10 MeV, respectively.

LEVEL STRUCTURE OF

Gamma rays from the 15-min fission product 138 Xe were studied with Ge(Li) detectors, NaI(Tl) crystal and coincidence equipments. Gamma rays of the following energies and relative intensities have been observed: 153.2(26), 242.8(9.6), 258.2(100), 396.5(16), 401.7(9.0), 434.6(48), 1770(39), 2002(14) and 2013 keV (29). With the measurements of the single gamma ray spectrum and the gamma-gamma coincidence spectra, the proposed levels in 138 Cs are at 15.4, 258.5, 411.4, 434.6 (or 450.0), 2028.4 and 2413.4 keV.

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A vertical diverging collimator is installed in the reactor tank of Rikkyo 100 kW TRIGA-II. The configuration of the collimator and the beam characteristics are summarized. The ASTM E545-81 sensitivity and beam purity indicators have shown that the collimator is qualified to be the category I. Inherent unsharpness for the combination of the 25 pm Gd screen and the KODAK-SR film is determined experimentally and found to be 48.0±0.5 µm. An application is given for the inspection of mold cavities in carburetors.

Cs FROM THE SHORT-LIVED FISSION PRODUCT

Recoiling behaviour of55Cr produced by54Cr/n, γ/55Cr reaction was studied by choosing solid Cr/acac/3 or its benzene solution as target material and by using rapid separation technique. The approximate retention value /“R-value”/ of55Cr, defined as the percentage of the activity retained in the benzene phase which was not extracted with an oxalic acid solution, was found to be higher than that of55Cr for practically all experimental runs tested /15 runs/. The ratio (55Cr/51Cr) was 1.115±0.027.

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A low background counter has been developed for alpha counting of extremely low activity. A scintillation counter with ZnS (Ag) was selected and alpha activities of sea water, river water, and vegetation were measured. The alpha activity of 10⁻¹⁰ mu c/ml could be measured by the counter. (auth)