High count rate correlation measurement between the lifetime of positrons and the momentum of an annihilating positron-electron pair was achieved by using the fast fast coincidence system. This system reads out data for energies of 7-rays produced by annihilations of positron-electron pairs and those for lifetimes of such pairs. These two types of digitalquantities were stored in a memory matrix of 32 channels (energy) ×256 channels (time) ×4 bytes (count) . The data acquisition was controlled by a microcomputer. The age-momentum correlation measurement was applied to studies of the Ps formation and its reactions with molecules in pure water, ice and solutions of MnSO4.From the measurements, it was found that reactions of Ps can be clearly observed from lifetime spectra measured as a function of the Doppler shift in annihilation γ-rays. In pure water, the self annihilation of para-positronium (p-Ps) and the pick-off annihilation of ortho-positronium (o-Ps) were observed. In solutions of MnSO4, the spin-conversion from o-Ps to p-Ps with a significantly narrow momentum distribution was found. This fact suggests that o-Ps is fully thermalized before the annihilation because of its long lifetime (-1 ns) . The present investigation shows the potential of the age-momentum correlation measurement for the Ps chemistry.
Autoradiographic observations using a photographic film on a granite rock slice have been established for two-dimensional distribution of elements, Al, Mn, and Na, which produce relatively short-lived radionuclides after pure thermal neutron irradiation. In the case of aluminium detection, it was suggested from semi-empirical estimation that an obstacle reaction of 28Si (n, p) 28Al with fast neutrons significantly overcomes the objective28Al-activity from the neutron capture reaction of aluminium, in addition to the contribution of after-glow phenomena with reactor exposure to sensitize the photographic film. As a result, the fine textures of aluminium pattern among mineral constituents could be conveniently recognized as well as in the case of manganese distribution. Subsequently, the imaging plate based on photo-stimulated luminescence phenomena has proven to be preferentially employed for the quantitative treatments of imaging patterns due to neutron-induced radionuclides. The advantageous points of the imaging plate, involving ultra-high sensitivity and acquisition of quantitative information, are discussed in comparison with the traditional photographic technique.
A radiochemical neutron activation analysis to determine tellurium in sodium hydroxide solution has been developed. Coprecipitation with Fe (OH) 3was applied to preconcentration of tellurium. After the irradiation the tellurium is separated by solvent extraction with MIBK and determined using 131Te isotope. The purification of iron carrier to be used for the coprecipitation and the separation efficiencies of principal elements in the chemical process of this method were studied. The result indicates that the method has a high sensitivity for the tellurium, and the detection limit is 0.04 ppb. The method is applicable to the non-radioactive tracer testing to measure the transfer of radiotellurium, a fission product, in the sodium coolant of the fast neutron reactor.
Porto-systemic shunt was evaluated by portal scintigraphy with rectal administration of 123I-IMP in 18 patients with diffuse liver diseases. A dose of 123I-IMP (111 MBq) was administered to the upper rectum through a catheter. Images of the chest and abdomen were obtained with a large field of scintillation camera interfaced with a computer up to 60 min. In all patients, the liver and /or lung images were visualized for 5-10 min and became clear with time. Time-activity curves on the liver and /or lungs rose steadily after123I-IMP administration, The porto-systemic shunt index was obtained by dividing counts for lungs by those for liver and lungs. These values were higher in liver cirrhosis, especially in the decompensated stage and correlated siginificantly with ICGR15 on the liver function test. In conclusion, transrectal portal scintigraphy with 123I-IMP is useful for the noninvasive and quantitative evaluation of porto-systemic shunt in patients with liver diseases.
Morphological change with soybean root development was investigated non-destructively by neutron radiography. Not only the main root but also the side roots were shown as an clear image on both X-ray and dry films. In the case of dry film, the resolution of the image obtained was about the same as that by X-ray film and the thermal neutron flux was reduced to be about one fifteenth. The image of the root was much clearly obtained in the sand than in the soil where the soil aggregates were randomly shown. In order to know to which degree the root can be shown in the image, the aluminum containers with various thickness were tested. Even when the thickness of the container was increased up to 1.7cm, the image of the main root was clearly observed through the soil. It was shown that by neutron radiography the morphology of the plant root could be traced non-destructively during the development of the plant.
Experiments were made to determine the exposure rate dependence of CO33-signal intensity in ESR dosimetry of tooth enamel. Packages containing 100 mg of mixed tooth enamel of particle size of 500- 850μm were irradiated by 60Co gamma-rays with various exposure rates ranging from 5.17×10-3 to 3.48 C kg-1 h-1 up to a total exposure of about 1290×10-4 C kg-1 (500 R) . The irradiated tooth enamel samples were then subject to ESR measurements and the relative response was determined as a function of exposure rate. The response was found to be almost independent of exposure rate. No significant difference of response is observed between dry-irradiated and wet-irradiated samples.