The kinetics of extraction of uranium (VI) from alkaline carbonate medium by tricaprylmonomethylammonium chloride (Aliquat-336) in kerosene has been investigated using a stirred Lewis cell. The effects of different parameters affecting the extraction rate, such as hydrogen ion, carbonate, hydroxide, Aliquat-336, U (VI) concentrations as well as temperature, were separately studied and a rate equation was deduced. The extraction process was found to be governed by chemical reaction in the bulk phase rather than at the interface.

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The counting efficiency for air luminescence due to ²²²Rn and its daughters was determined with commercially available liquid scintillation spectrometers giving much attention to Cherenkov radiation due to β^--particles and internal conversion electrons from ²¹⁴Ph and ²¹⁴Bi. Based on the results, we propose a rapid and reliable method for preparation of known amounts of ²²²Rn, which are needed for calibration of detectors measuring ²²²Rn or a number of experiments using ²²²Rn, without elaborate instrumentation or technique.

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A review is given on radiochemical study on photonuclear reactions on target nuclei ranging from ⁷Li to ²⁰⁹Bi at intermediate energies, i.e. bremsstrahlung end-point energies of 30-1200 MeV, by the author's group since 1980s. The study covers the yield measurements of photopion reactions, spallation, fragmentation and fission of preactinides, ¹⁹⁷Au and ²⁰⁹Bi, systematically performed with respect to photon energy, target mass (A_t) and/or target composition (N/Z) _t, and product mass (A) and product composition (N/Z). Such a thorough study has not existed in this field. Thouusands of the yield data were compiled and found to be smoothly varying functions of these parameters. And the relevant empirical expressions for the reaction yields were derived. The data for the four reaction channels above 140 MeV indicate clear shapes of Δ (1232) -resonance and strong effects of the nuclear medium on the cascade-evaporation process in nuclei with A_t higher than 110-130 or (N/Z) _t larger than 1.3-1.4. All of the results have been updatedly used to test Monte Carlo calculations based on the photoninduced intranuclear cascade and evaporation analysis (PICA) code and its improved versions, and the degrees of the validity of the codes have been demonstrated. New implications for nuclear structure and reaction mechanism have been discussed by referring to the nuclear models, on which the calculations are based. Kinematic information from additional experiments performed on several targets at the Δ-resonance region has supported the findings from the yield measurements. The results of the yield measurements and the characteristic features of the four channels are explained separately, though these channels are competitive. Important consequences and perspectives of the accounted works are pointed out relevantly.

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This review paper gives the description on the recent development of various new sophisticated neutron spectrometers. For neutrons of energies beyond 100 MeV, the self-TOF detector using the NE102A plastic scintillators, large-scale NE213 organic liquid scintillator, and spallation detectors of C and Bi have recently been developed by our group, especially for use in neutron target and shielding experiments. Various neutron spectrometers have also been developed for use in the charged particle and neutron mixed field which is realized in space environment. The following spectrometers are briefly described: 1) Phoswich detector which combines the NE115 plastic scintillator and the NE213 scintillator, 2) Anti-coincidence detector system using . ΔE and E counters, and 3) Bonner sphere (multi-moderator detector) mounted a ³He counter or a pair of ⁷Li and ⁷Li glass scintillators.

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