Abstract: A method of converting uranium dioxide into a metallic uranium lump is provided The method comprises mixing a reducing agent comprised of metallic calcium, a slag solvent comprised of calcium chloride and a eutectic comprised of at least one member selected from the group consisting of barium chloride, lithium chloride, sodium chloride and potassium chloride into uranium dioxide to obtain a mixture, heating the mixture at a temperature not below the melting point of metallic uranium, separating resulting molten metallic uranium from a resulting molten slag based on a difference in specific gravity, and cooling the molten metallic uranium to produce metallic uranium as a solid lump.

Abstract: A microwave heating apparatus includes a microwave oscillator, a waveguide for transmitting microwave energy outputted from the microwave oscillator to an object to be heated, detectors for detecting the power of the microwave energy inputted from the microwave oscillator to the object to be heated and the reflected power of the microwave energy reflected from the object to be heated, a matching stub provided in the waveguide, and a driver for driving the matching stub. The driver calculates a VSWR value from the inputted power and the reflected power and includes a motor for driving the matching stub so that the VSWR value is maintained within a predetermined range. Matching of the waveguide impedance with the load impedance can be executed automatically and the VSWR value can be maintained in the range of good matching. Thus, lowering of heating efficiency can be prevented.

Abstract: A multi-mode Raman laser system wherein Raman conversion is performed by injecting exciting laser beam from transversely excited atmospheric pressure CO.sub.2 laser system into a Raman cell. Unstable resonator type oscillator is used as transversely excited atmospheric pressure CO.sub.2 laser system; and multi-mode Raman cell is used as the Raman cell. The quantity required for an excited CO.sub.2 laser system can thus be extensively reduced. Also, it is possible to reduce the input electric required for obtaining the same energy of 16 .mu.m light which is scattered light, because saturated conversion of excited light, can be achieved by multi-mode Raman cell, and system efficiency can be increased.

Abstract: A method of treatment of a high-level radioactive waste comprising heating the radioactive waste at a high temperature of about 500.degree. to 3000.degree. C. to vaporize part of the elements contained in the radioactive waste, and cooling the resultant vapor to separately collect the elements. In one embodiment, the heating step is replaced by a reduction-heating step wherein heating is carried out in the presence of a reducing agent, e.g. hydrogen. In another embodiment, the heating step may be followed by the reduction-heating step.

Abstract: A radioactive catalyst is disclosed which comprises a fine particle of semiconductor and a high radioactive platinum group element deposited on the particle of semiconductor. The radioactive catalyst serves as a source of radiation and also as a catalyst for oxidation-reduction reaction. By bringing the radioactive catalyst into contact with water, the water is decomposed by the oxidation-reduction reaction to produce hydrogen and oxygen.

Abstract: A method of extracting and separating a spent solvent generated in a nuclear fuel cycle and containing a phosphate (TBP) and a higher hydrocarbon (n-dodecane). This method comprises bringing the spent solvent into contact with methanol, thereby causing the spent solvent to be separated into a phase mainly composed of the higher hydrocarbon and a methanol phase containing the phosphate. By drying the phase mainly composed of the higher hydrocarbon at a low temperature, a minor amount of methanol contained in the phase is separated through evaporation to recover the higher hydrocarbon. By drying the methanol phase at a low temperature, methanol is recovered through evaporation and the phosphate remains as a remaining solution. The remaining solution may further be subjected to low-temperature vacuum distillation to separate the solution into the phosphate (TBP) and a deterioration product thereof (DBP).

Abstract: An electromagnet for a nuclear reactor shutdown system, which comprises upper and lower cores disposed in an axially symmetrical arrangement and capable of latching with and delatching from each other. When an ambient temperature increases, the upper and lower iron cores are delatched from each other and a control rod connected to the lower iron core falls down into a reactor core. The lower iron core is provided with a plurality of slits to form a plurality of fins therebetween. A temperature sensitive magnetic material (TSMM) is disposed in the outer circumferential lower corner portion of the lower iron core. An interface between the TSMM and an iron core material takes the form of a side surface of a cone whose central axis is coincident with the symmetry axis and whose apex angle lies in the range of 60.degree. to 120.degree..

Abstract: A method of separating uranium and plutonium from a mixed solution containing uranium nitrate and plutonium nitrate comprises cooling the mixed solution to a temperature ranging from -40.degree. to -20.degree. C. to thereby selectively precipitate uranyl nitrate. The precipitated uranyl nitrate is separated from the solution while leaving plutonium nitrate to remain in the solution.

Abstract: A radiation shielding structure including a radiation shielding panel which comprises a lead transparent plate, for example, a transparent lead acrylic resin plate, lead glass plate, etc., and a thin nonlead transparent plate, for example, a transparent acrylate resin plate, glass plate, etc., which is laminated on at least one side of the lead transparent plate. Thus, lead that is contained in the lead transparent plate shields radioactive rays, while the nonlead transparent plate, which is laminated on at least one side of the lead transparent plate, prevents oxidation of the lead in the lead transparent plate by air or chemicals, which oxidation would otherwise form an oxide film on the panel surface and make the panel opaque.

Abstract: The laser isotope separation apparatus utilizes the circularly-polarized light to selectively excite the isotopes to the first or the second excited level. In case where the isotope shift is equal to or smaller than the line width of the laser light, it can be selectively ionized and separated because the isotopes absorb the circularly-polarized light based on the angular momentum selection rule and are excited and the isotopes not excited according to the mass number of isotopes (or those having nuclear spin not equal to zero and equal to zero). The selective excitation by the angular momentum selection rule and the ionization are performed by 3 steps of excitation. Three excitation wavelengths are generated from two or more lasers, and the optical paths of these light beams are made to be in same length by optical delay circuit. Accordingly, even when the laser light source is pulse-operating, selective excitation and ionization can be performed.

Abstract: A method of separating and purifying a spent solvent generated in a nuclear fuel cycle and containing a phosphate and a higher hydrocarbon. This method comprises treating the spent solvent at a temperature not greater than the freezing point of the higher hydrocarbon but not less than the freezing point of the phosphate to selectively freeze the higher hydrocarbon, and separating a resulting frozen solid mainly composed of the higher hydrocarbon from a remaining solution containing the phosphate in a higher concentration. The remaining solution may further be subjected to low-temperature vacuum distillation to separate the solution into the phosphate and a deterioration product thereof.

Abstract: In-core nuclear instrumentation for a fast breeder reactor includes a neutron flux measuring unit disposed in a control rod assembly, whereby it is possible to measure a change in in-core neutron flux reliably and highly accurately without requiring a major modification in core design.

Abstract: A method of controlling a single temperature type water/hydrogen isotopic exchange reaction plant comprising an electrolytic system, an exchange reaction column and a recombining system for separating degraded heavy water into product and waste both of which have a stable concentration. The control method comprises controlling an extracting quantity of waste so that a heavy water concentration of water at an intermediate portion of the reaction column is kept constant, and controlling an extracting quantity of product so that a water quantity inside the exchange reaction plant is kept constant.

Abstract: A radioactive catalyst is disclosed which comprises a fine particle of semiconductor and a high radioactive platinum group element deposited on the particle of semiconductor. The radioactive catalyst serves as a source of radiation and also as a catalyst for oxidation-reduction reaction. By bringing the radioactive catalyst into contact with water, the water is decomposed by the oxidation-reduction reaction to produce hydrogen and oxygen.

Abstract: A method of treatment of a high-level radioactive waste containing platinum group elements is provided in which boron and a boron compound is added to a calcined material of the high-level radioactive waste in an amount of 0.5 to 10% by weight in terms of boron as a simple substance, and the resultant mixture is heated at a temperature of about 1000.degree. C. or above under a reduction condition to melt the mixture and to alloy the platinum group elements present in the calcined material with boron. A layer of the resultant platinum group element alloys is then separated and recovered from a layer of residual oxides through sedimentation. The layer of the residual oxides is solidified to form a highly volume-reduced high-level radioactive solidified waste.

Abstract: A self-actuated nuclear reactor shutdown system includes a control rod, a temperature sensitive electromagnet disposed above the control rod for causing the control rod to latch thereto and unlatch therefrom, and a control rod insertion portion around which a plurality of wrapper tubes each accommodating a fuel assembly are arranged. The present invention is characterized in that the upper part of the wrapper tube or an extension tube connected to the upper end of the wrapper tube is made of a temperature-sensitive magnetic material having a characteristic by which the saturation flux density thereof will be reduced at the time of an extraordinary rise in the temperature of a coolant flowing through the fuel assembly. The temperature sensitive magnetic material constitutes a part of a magnetic circuit of the electromagnet.

Abstract: A bus bar for power supply is comprised of a pipe-shaped outer conductor and at least one inner conductor inserted therein. The inner conductor is also formed in a pipe shape and serves as a coolant flow passage. Insulation is interposed between the outer conductor and the inner conductor to electrically isolate them from each other.

Abstract: A method of compacting radioactive metal wastes comprising enclosing the radioactive metal waste in vacuo in a capsule, placing the capsule into a pressure container, and subjecting the capsule to an increased pressure at a high temperature to compact the waste. The compacting treatment is conducted in a state in which the atmosphere within the pressure container contains water molecules in an amount, in terms of the total weight W (g) thereof, the amount being preferably in the range of:1.3.times.10.sup.-6 .times.V.ltoreq.Wwherein V (cm.sup.3) is the volume of the compacting space in the pressure container. Alternatively, an oxide coating is formed on the outer surface of the capsule before the capsule is placed into the pressure container, or the formation of the oxide coating is followed by the compacting treatment conducted in the above-mentioned state.

Abstract: An electric melting furnace for vitrifying waste, having a melting tank having walls of refractory bricks, the melting tank being provided at the upper portion thereof with a supply port for a glass additive and waste and at the bottom portion thereof with a discharge port for molten glass containing the waste; at least a pair of side electrodes horizontally provided on opposite side walls of the melting tank; and at least one central electrode having a polarity opposite to that of the side electrodes, the central electrode being horizontally positioned in the interior of the melting tank at substantially the middle portion between the side electrodes. By such melting furnace construction, as described above, the heating current selectively flows through between the side electrodes and the central electrode, and does not flow electrically conductive substances deposited on the furnace bottom.

Abstract: A plant malfunction diagnostic method is characterized by determining by simulation a change in a plant state variable, forming a pattern among plant state variables obtained by autoregressive analysis of the change in plant state variable, inserting the formed pattern among the plant state variables in a neural network, performing learning until a preset precision is obtained, and identifying the cause of the malfunction by inserting, in the neural network, a pattern which indicates the pattern among plant state variables formed by data gathered from the plant. This makes possible early identification of the cause of a malfunction. Plant rate of operation and safety are improved by allowing the operator to perform the appropriate recovery operation with a sufficient time margin.