[en] Object: To carry out a series of processes, in a vessel, of separating, condensing, dewatering and solidifying a solid portion contained in a radioactive liquid waste. Structure: Radioactive liquid is ejected from a nozzle into the rotor and the radioactive liquid is separated into solid and liquid by a turning force of the rotor. The solid matter is adhered to the wall of the rotor and clear water enters a second space through an outlet drilled in the periphery of a hollow cylinder at the upper part of the rotor and is discharged through an outlet disposed in a lower wall of a housing. When the solid matter is somewhat accumulated within the rotor, the rotor is stopped to discharge the liquids remaining in the rotor outside the rotor through an opening in a cylindrical shaft at a lower end of the rotor. Finally, solidifying material such as cement is thrown into the housing through an inlet thereof to fill it into three spaces through a communicating hole until the housing forms one sheet. (Taniai, N.)

[en] Object: To introduce radioactive liquid waste into a drum can vessel and add cement or asphalt therein to close the can, which is then vibrated to obtain a solid in which the radioactive liquid waste and cement or asphalt are uniformly mixed. Structure: A drum can is placed on a vibration bed disposed at the upper part of a vibrator and fixed by a movable arm and a keep bed while rotating a screw-fastening handle. The liquid waste is introduced into the drum can into which cement or asphalt is added and the can is closed, and thereafter, the vibrator is vibrated by a vibration motor and an eccentric cam to uniformly mix the radioactive liquid waste and cement or asphalt within the drum can, thereby obtaining a solidified body. (Yoshihara, H.)

[en] Object: To permit solidification of waste water containing radioactive oil with cement by a method, which needs no agitator, eliminates scattering of the radioactive material, does not require emulsifier for treating the oil and eliminates oil component remaining on top of the solidified body. Structure: Radioactive waste water is held stationary within a container such as a drum can, and then a cement powder is uniformly sprayed over the water surface from above the container to wrap the oil on the water surface with cement powder and cause the resultant system to be lowered below bottom of the container and accumulated there in the form of a layer and then cement powder is continuously poured up to the water surface. In this way, waste water containing radioactive oil is solidified with cement. (Horiuchi, T.)

[en] Object: To securely perform separation and enrichment of radioactive rare gases to store safely them for a long period of time. Structure: The wastes extracted by an air extractor are processed by a heater and a recombiner and hydrogen and oxygen are changed into water thereby and it is passed through a gas and water separator to be dewatered, after which water and carbon dioxide gas are removed by passing through a delay pipe, filter, and water- and carbon dioxide gas removing device and then fed to a lower temperature adsorbing device to adsorb and remove the radioactive rare gases. This low temperature adsorbing device is composed of two towers, one of which is designed to saturate the radioactive rare gases, which are processed by a heater and passed through a recycle line to meet raw gases. Then, it is fed to the other lower temperature adsorbing device and this cycle is repeated to enrich the radioactive rare gases. Oxygen and impurities in the enriched gases are removed by the impurity removing device and thereafter are stored in a gas holder and finally sealed in a cylinder. (Kamimura, M.)

[en] The unit No. 1 of Onagawa Nuclear Power Station, Tohoku Electric Power Co., Inc. is a MARK-1 type 524-MWe BWR plant. Toshiba got the order for the design and construction as a main contractor, and completed the plant to be put into commercial operation last June. Description is made here of the highlights in its design, construction and test operation. It will be of note that : (1) this unit is a BWR-4 type housed in a MARK-1 type primary containment vessel; (2) the construction work has been completed in only 48 months since the start in December 1979 ; and (3) the number of BWR units completed by Toshiba has reached to 10 with this unit, totaling up to 7,274 MWe in output capacity. (author)

[en] Object: To reduce the producing amount of ozone within a liquefaction and distillation apparatus for processing radioactive dilute gas. Structure: The radioactive dilute gas containing gases are supplied to a rectification tower through a heat exchanger. Oxygen and nitrogen are cooled by a condenser cooled with liquid nitrogen, and they are partly condensed into a circulating liquid, the remainder being released into atmosphere through a purifying gas line. The radioactive dilute gas is taken out of the tower bottom through a liquid taking-out line and heated by a heater, after which ozone is removed by an ozone remover unit, finally meeting the raw gases. The tower bottom is filled with filler such as Raschig ring to absorb radioactive energy and thus prevent generation of ozone within the tower. (Kamimura, M.)

[en] Object: To safely and securely store radioactive rare gases for a long period of time. Structure: The waste gases produced in nuclear power plant are cooled by a cooler and then introduced into a low temperature adsorbing device so that the gases are adsorbed by adsorbents, and then discharged into atmosphere through the purifying gas discharge line. When the radioactive rare gases reach a level of saturation in the amount of adsorption, they are heated and extracted by a suction pump and heated by a heater. The gases are then introduced into an oxygen-impurity removing device and the purified rare gases containing no oxygen and impurities are cooled by a cooler and fed into a gas holder. When the amount of radioactive rare gases stored within the gas holder reaches a given level, they are compressed and sealed by a compressure into a storing cylinder and residual gases in the piping are sucked and recovered into the gas holder, after which the cylinder is removed and stored in a fixed room. (Kamimura, M.)

[en] Purpose: To store solid waste, which has been obtained by vaporizing and drying radioactive waste, in the form of a stable solidified body, to re-use separated water. Constitution: Enriched liquid waste, waste resin and sludge are respectively stored in a storage tank, after which they are fed into an adjusting tank at the rate suitably determined. The thus adjusted liquid waste is extracted by a pump and fed to a vertical-type film scraper and dryer to subject to heating, vaporizing and drying. The vaporized steam is formed into condensed water by means of a condenser and recovered into a sample tank for re-use. On the other hand, dried powder is fed to a powder storage tank until it reached a predetermined level of quantity, after which they are fed to a cement, asphalt or plastic solidifying device. Slurry-like material not sufficiently dried and washing water of dryer are collected tin a drain tank, and they are re-dried by the adjusting tank through the pump or returned to the waste disposal system. (Yoshihara, H.)

[en] Object: To prevent dispersion of radioactive rare gas atoms by sealing them in a pressurised state within zeolite and thereby confining them in position within the zeolite crystal lattice. Structure: Radioactive rare gas is separated from exhaust gas and concentrated by using a low temperature adsorption means or liquefaction distillation means and necessary accessory means, and then it is temporarily stored in a gas holder. When a predetermined quantity of storage is reached, the gas is led to a sealing tank containing zeolite heated to 300 to 400⁰C and held at 3,000 to 4,000 atmospheres, and under this condition radioactive rare gas is brought to occupy the spaces in the zeolite crystal lattice. After equilibrium pressure is reached by the pressure in the tank at that temperature, the gas is cooled in the pressurized state down to room temperature. Subsequently, the rare gas remaining in the tank and duct is recovered by a withdrawal pump into the gas holder. Thereafter, the zeolite with radioactive rare gas sealed in it is taken out from the tank and sealed within a long period storage container, which is then housed in a predetermined place for storage. (Kamimura, M.)

[en] Some guides for design objectives to meet the criterion ''As Low As Practicable'' was definitely announced as a national guidance last year. The concept of these guides has been early applied to the design of our plants. Moreover, efforts are being put forth for the development of volume reduction and solidification systems for solid wastes. This article gives an outline of the design improvement and development of radioactive waste disposal systems for BWR plants by Toshiba. (auth.)