In the case of petri dish-type cloud chamber with an α-ray source of monazite sphere(2.5mm diameter), the expected number of the α-ray tracks was theoretically calculated using Bethe formula and compared with the reported experimental value. The validity of the calculation method was firstly confirmed. The theoretically calculated number of α-ray tracks(0.208 per second) in a cloud chamber was fairly agreed with experimental value(0.383 per second). During the observation of the tracks, the surface of the source was gradually wet with ethanol-liquid. The thickness of the liquid layer was estimated to be 6μm by comparing the calculated escape probability of the α-rays and the experimental value under having the liquid layer on the source surface.
Hydrogen ions accompany water from the anode to the cathode in solid polymer electrolysis for tritium water enrichment. The conventional enrichment apparatus has a flow pass between the anode and the cathode to mix water continuously. When the flow pass is closed, the cathode shows constant tritium enrichment, while the anode does not show any tritium enrichment at all. In this study, we built a system in which water obtained from the cathode returns to the anode with the help of a tube pump. The automated system repeats this process continuously and achieves tritium enrichment factor from 7.0 to 10.3 in the case of initial water value 600g, decreasing the enriched water value to half of these conventional value, i.e., from 54g to 27g.
New method for preventing contamination of an incubator with 35S in cell culture experiment was developed and successfully applied to actual experiment. Large radionuclide contamination in water in a humidification vat and on inner surface of an incubator was generally detected in cell culture experiment using amino acids labeled with 35S. We constructed a plastic vessel for home use installed with charcoal sheets at the bottom and its cap. Experimental cells were cultivated with 35S-labeled amino acid in dishes put into the vessel that was placed in the incubator. The charcoal sheet was quite effective to prevent 35S dispersion from the vessel, and no contamination was detected in the humidification vat and inner surface of the incubator. The charcoal sheets adsorbed large amount of 35S, and showed the effectiveness of the present method.
The experimental determinations of W-value, the average energy required to produce an ion pair by a charged particle in gases, have been attempted by many researchers since just after the discovery of radiation. From these experiments, W has become to be established in many gases, and to be known as being almost constant for electrons and protons over a wide range of energy. Still at present, however, some of gases have no established values of W, and there are few data of W for heavy charged particles(ions), which is known to show the dependence on particle energies. Some important properties of W, such as dependences of particle Z and the gas pressure, are not sufficiently clear. In this article, the present status of W is reviewed, and the problems in measurements of W are discussed.
Technetium-99 metastable nuclide(99mTc), a daughter nuclide of 99Mo, is a radio-isotope essential to the diagnosis of the disease like cancer. However, in Japan, a total amount of 99Mo for pharmaceutical ingredient of 99mTc is imported from abroad. Especially all of the 99Mo in Japan has been imported and it accounts for about 14% of all of the 99Mo production doses in the world. It is an urgent issue to secure domestic 99Mo supply for stable delivery to patients. Presently the materials testing reactor JMTR of Japan Atomic Energy Agency(JAEA) has been refurbished and will be restarted after long shutdown since 2007. Considering the above context, JAEA has investigated a feasibility to apply the neutron activation method, so-called the (n, γ) method, to 99Mo production with JMTR. The (n, γ) method is low cost because of no need for treating the irradiated nuclear fuel. Here the results of the investigation in collaboration with the industries and universities are described. The amount of 37TBq(1000Ci)/week of 99Mo is assumed as an appropriate amount of 99Mo for the domestic supply. Also a concentration of 99mTc is practically needed up to 37GBq/mL or more for drug preparation. As a result, it was found to solve the problem of low specific activity of 99Mo in the Mo target that high efficient 99Mo adsorbents and high concentration techniques of 99mTc are required.
A compact-medical cyclotron is applicable for the 99mTc direct production and medium-class one is good for 99Mo production, respectively. We demonstrated an automated production of 99Mo/99mTc by using charged particles on 100Mo target. The direct 99mTc production way is suitable for small-scaled production with an easy operation. The 99mTc purification was carried out automatically by using two ion exchange columns. Briefly, 99mTc was separated from 100Mo target by both a Tc selective resin(TEVA) and an anion exchange resin(Dowex) in series. Then, a dried 99mTcO4 was obtained in free or Na form as a result of final preparation. This separation method would be capable for any 99Mo, namely, 99Mo from 100Mo as well as neutron captured 98Mo. Therefore, this automated separation apparatus would be applicable widely as a novel 99Mo/99mTc generator. In our country, about 150 medical cyclotrons are in operation in PET facilities. Thus, the use of these accelerators located in every region would be helpful to produce local-demanding radioactive doses of 99mTc.
Neutron imaging at a pulsed neutron source can simultaneously give position-dependent neutron transmission spectra of a material. “Bragg edge” transmission pattern appears at low energy region of the spectrum. Since the Bragg edge transmission spectrum includes various crystalline structural information, e.g., crystal structure, crystalline phase, crystallographic texture, crystallite size and strain, the pulsed neutron imaging using a two-dimensional area detector can non-destructively visualize such the information over the wide area of a material. In this article, principles, features and experimental examples of the Bragg edge transmission imaging that is expected as a new analysis tool for materials science are presented.