[en] A material is claimed for recovering uranium from acidic uranium solution, which comprises a mineral acid salt of a weakly basic anion exchange resin being a cross-linked copolymer prepared from at east one vinyl monomer having a pyridine nucleus and a monomer having at least two unconjugated ethylenic double bonds with or without another vinyl monomer, and having a gel or porous structure. The cross-linked copolymer has a cross-linkage of 4 to 30% by weight

[en] A ultra sensitive neutron imaging system has been deviced with a 2-dimensional photon counting camara (ARGUS 100). The imaging system is composed by a 2-dimensional single photon counting tube and a low background vidicon followed with an image processing unit and frame memories. By using the imaging system, electronic neutron radiography (NTV) has been possible under the neutron flux less than 3 x 10⁴ n/cm²·s. (author)

[en] Published in summary form only

[en] The fission-track counting method using polycarbonate foil is known to be very effective for neutron monitoring. The detection system consists of a track detector foil placed in contact with a thin layer of fissile material. When the unit is irradiated with neutrons, fission fragments from the fissile material produce tracks in the foil. The foil is then etched chemically to enlarge the tracks to etch-pits, which are counted by an automatic spark counting method suggested by Cross and Tommasino. Spark counting characteristics of the above system using polycarbonate detector foils of different thicknesses and aluminized polyester sheets having different thicknesses of the aluminium which serves as an electrode, and etch-pit sizes in relation to spark counting have been studied. The results obtained are summarized as follows: 1. A growth in etch-pit sizes was observed for etching times of 10 to 50 minutes with Makrofol KG (10 μm thick) and Panlite foils (18 μm thick). As the etching time increased, the number of etch-pits which appeared as round pits increased and the number which appeared rod-like decreased; 2. Round etch-pits seemed to be easily spark-punched; 3. Major and minor diameters of etch-pits produced by fission fragments from the uranium fissile target were larger than those from the thorium target; 4. As the thickness of the Makrofol KG foil increased, the minor diameters of the etch-pits appeared to become smaller and major diameters larger; 5. The foils that appeared to be best suited for routine use were 10 μm thick Makrofol KG or 6 μm thick Lumirror foils. (author)

[en] Automatic spark counting of etch-pits on a polycarbonate film produced by nuclear fission fragments is now used for neutron monitoring in several countries. A method was developed using an aluminium oxide film instead of a polycarbonate as the neutron detector. Aluminium oxide films were prepared as follows: A cleaned aluminium plate as an anode and a nickel plate as a cathode were immersed in dilute sulfuric acid solution and electric current flowed between the electrodes at 12degC for 10-30 minutes. Electric current density was about 10 mA/cm². The aluminium plate was then kept in boiling water for 10-30 minutes for sealing. The thickness of the aluminium oxide layer formed was about 1μm. The aluminium plate attached to a plate of suitable fissionable material, such as uranium or thorium, was irradiated with neutrons and set in a usual spark counter for fission track counting. One electrode was the aluminium plate and the other was an aluminized polyester sheet. Sparked pulses were counted with a usual scaler. The advantage of using spark counting with an aluminium oxide film for neutron monitoring is rapid measurement of neutron exposure, since chemical etching which is indispensable for spark counting with a polycarbonate detector film, is not needed. (H.K.)

[en] The multiple-stage CVD method is the promising technology, which can be realized for rapid and long formation of YBCO tape. In earlier researches, we have fabricated the six-stage CVD system, and successfully developed 100 m long YBCO tape at the deposition rate of 10 m/h. However, over 500 m long wires are required for the practical applications. In order to achieve this, we have studied the multi-coating of YBCO layer at further high-speed deposition. Five layers of YBCO tape were fabricated on roll milled non-textured Ag substrate directly. Each layer was deposited by the six-stage CVD system at deposition rate of 25 m/h. After each deposition, temperature of YBCO tape went down to room temperature. The distribution of J_c was within 25% and its value is the same as single coating one. No significant degradation of J_c was observed. From these results, it was indicated that the multiple-stage CVD system, which equips more reactors serially, is effective way for making longer YBCO tapes

No abstract available

[en] Commercial Thermoluminescence dosemeters (TLDs) currently used are finely powdered lithium fluoride (LiF), calcium sulphate or magnesium silicate etc. sealed in glass tubes or those melted with special resins. These are opaque or semi-transparent and therefore thermoluminescence light emitted inside does not come out efficiently due to the self-absorption. To avoid the self-absorption LiF single crystals have been examined. A cylindrical graphite crucible including LiF mixed with trace amounts of magnesium, copper and phosphorus was heated in a vacuum stainless tube with a slowly moving heater coil along the axis. The LiF single crystal grew gradually from the bottom tip of the crucible. Thermoluminescence emitted from a LiF single crystal after irradiation with γ rays increased as phosphorus in the LiF crystal increased. Thermoluminescence emitted from a single crystal with 0.25 mole percent phosphorus was one order higher than that emitted from powdered LiF with the same mole percent phosphorus and the same weight. A single crystal could not grow with phosphorus of more than 0.25 mole percent. However, lithium phosphate appears to be a better activator material than the ammonium phosphate used in the experiments to overcome the 0.25 mole percent barrier. (author)

[en] Different (n, α) converter materials placed in contact with cellulose nitrate detectors were tested as thermal neutron detectors. A plastic sheet doped with 1% boron, a solidified boron oxide plate, a single crystal plate of boron oxide and a single crystal plate of lithium fluoride were used as converter materials. After thermal neutron irradiation in the low power research reactor of the Institute, the cellulose nitrate detectors were etched in alkaline solution. The etched holes on the films were counted with a spark counter. The single crystal of lithium fluoride was found to be the most sensitive converter for the detection of thermal neutrons. A linear relation was observed between thermal neutron fluence and spark counts in the range 10⁶ to 10⁷ n.cm^-2. A method of producing the single crystal converter is also described. (author)

[en] Polycarbonate sheets of different thickness for nuclear track detection and aluminized polyester sheet of different aluminium thickness for an electrode are examined. Optimum punching and counting voltages are approximately linear to the polycarbonate sheet thickness, and counting rate decreases nearly exponentially with time. Hole sizes on aluminized polyester sheet due to sparking (150-180μm) slightly decrease with thickness of aluminium layer of the aluminized sheet (27-220A). Plateau voltages for spark counting does not depend largely on thickness of aluminium layer of the aluminized sheets, however plateau length depends upon the thickness of aluminized sheets. Preparations of uranium target for thermal neutron detection and of thorium target for fast neutron detection using electroplating are also presented. Thorium electroplating is usually more difficult than uranium electroplating, but thorium was successfully deposited on stainless steel plate in the solution of ammonium oxalate, thorium nitrate, ethanol and water at 80⁰C. Electroplating efficiencies of 500μg of uranium and thorium were about 90% and 70% respectively