Abstract: A pressure measuring apparatus using process transmission media and comprising measuring and compensation systems. These systems have the substantially same construction which comprises a pressure receiving portion, a pressure transmitting portion and a pressure detecting portion. The pressure transmitting portion is divided into two sections, each of them contains a liquid NaK and a heat-resisting inert liquid, respectively, as pressure transmission media. A pressure of a fluid to be measured which is introduced into the pressure receiving portion of the measuring system is transmitted through the transmitting portion to the pressure detecting portion where the pressure is detected. A pressure of a gas introduced into the pressure receiving portion of the compensation system is detected in the pressure detecting portion of the compensation system in a same manner. The temperature compensation is conducted by subtracting a detected pressure in the compensation system from that in the measuring system.

Abstract: A method of detecting minute flaws on the surface of a metal material is provided, which is constituted by the steps of directing a laser beam onto the surface of the metal material, reflecting a component of the beam directly reflected by the surface of the material by a reflector having a rough surface, and measuring the change in the quantity of light in the beam reflected by said reflector. Alternatively, a component of the laser beam directly reflected by the surface of the material and a component of the laser beam scattered by the metal surface are passed through a semitransparent filter having a rough surface, and the change in the quantity of light in the beam passed through the filter is measured.

Abstract: A process for recovering uranium from a wet-process phosphoric acid crude solution is provided in which the phosphoric acid crude solution is contacted with an organic extractant consisting of octylphenyl phosphoric acid, di(2-ethylhexyl)phosphoric acid and trioctylphosphine oxide dissolved in an organic diluent to extract uranium from the phosphoric acid crude solution. The thus uranium loaded organic extractant is then contacted with mixed acid consisting of hydrofluoric acid and sulfuric acid, or alternatively with concentrated phosphoric acid to back-extract the uranium from the organic extractant.

Abstract: Method and apparatus for detecting the position of defects in a liquid metal handling instruments such as sodium-heated steam generator, which has a conduit structure invisible from the outside of the instrument. The conduit structure, which is used in a liquid metal, is positioned in a vessel filled with an inert gas. The vessel is sealed whereas a liquid inactive to the liquid metal is filled in the conduit structure. If there exists a defective spot in the conduit structure, the liquid will flow out of the defective spot, which is exactly detected by application of a fiber scope.

Abstract: A process for reducing plutonium is provided in which hydrazine is added as a reducing agent to a nitric acid solution of tetravalent plutonium in the presence of active carbon catalyst to thereby reduce tetravalent plutonium into trivalent plutonium.

Abstract: A hydrogen detector of the type in which the interior of the detector is partitioned by a metal membrane into a fluid section and a vacuum section. Two units of the metal membrane are provided and vacuum pipes are provided independently in connection to the respective units of the metal membrane. One of the vacuum pipes is connected to a vacuum gauge for static equilibrium operation while the other vacuum pipe is connected to an ion pump or a set of an ion pump and a vacuum gauge both designed for dynamic equilibrium operation.

Abstract: A plugging meter for automatically measuring the impurity concentration in a liquid metal is designed to have parallel passages including a cooling passage provided with a plugging orifice and with a flow meter, and a by-pass passage connected in series to a main passage having another flow meter, so that the plugging points may be obtained from the outputs of both flow meters. The plugging meter has a program signal generator, a flow-rate ratio setter and a comparator, and is adapted to change the temperature of the plugging orifice in accordance with a predetermined pattern or gradient, by means of a signal representative of the temperature of plugging orifice and a flow-rate ratio signal obtained from the outputs of both flow meters. This plugging meter affords an automatic and accurate measurement of a multi-plugging phenomenon taking place at the plugging orifice.

Abstract: An extraction method of a high purity tritium gas from tritium-containing heavy water is disclosed. Tritium-containing heavy water is led from a heavy water source into an exchange reaction column wherein the heavy water is brought into contact with a tritium-containing heavy hydrogen to thereby transfer tritium in the heavy hydrogen into the heavy water by way of the exchange reaction to obtain a tritium-enriched heavy water. The resulting tritium-enriched heavy water is then led to a heavy hydrogen gas generator such as an electrolytic cell to generate a tritium-enriched heavy hydrogen, a part of which is recycled to the exchange reaction column and the remaining part thereof is led into a hot-wire type thermal diffusion column, e.g. cascade to enrich tritium. The thus enriched tritium gas is withdrawn from the thermal diffusion column cascade.

Abstract: A detector to be inserted into a flowing conductive fluid, e.g. sodium coolant in a nuclear reactor, comprising at least one exciting coil to receive an a-c signal applied thereto and two detecting coils located in the proximity of the exciting coil. The difference and/or the sum of the output signals of the detecting coils is computed to produce a flow velocity signal and/or a temperature-responsive signal for the fluid. Such flow velocity signal or temperature signal is rectified synchronously by a signal the phase of which is shifted substantially .+-. 90.degree. with respect to the flow velocity signal or temperature signal, thereby enabling the device to detect voids in the flowing fluid without adverse effects from flow velocity variations or flow disturbances occurring in the fluid.

Abstract: A bellows which is made up of a plurality of coaxially joined bellows elements each having a plurality of n parallelogram-shaped wall elements of thin plate material joined together and positioned around a common center axis. The upper and lower edges of the thus joined wall elements define spaced parallel congruent planar orthopolygonal shapes each having n sides, n being equal to or greater than 3. Each of the orthopolygonal shapes in angularly offset in a direction around the central axis from the next adjacent orthopolygonal shape. The wall elements each have a fold line between the diagonally opposite vertexes which are the farthest apart. The bellows can have a further bellows with an axial cross-sectional shape in the form of waves joined coaxially thereto.

Abstract: An apparatus for detection of the level of a liquid metal is disclosed. The apparatus has a liquid level detecting probe provided with an exciting coil wound in a closed bottom non-magnetic sheath over the approximately whole length thereof, a level detecting coil wound in the sheath in an upper part thereof, and a temperature compensating coil wound in the sheath in a lower part thereof; a temperature control for maintaining the coils at a constant temperature; a drive circuit for supplying the exciting coil with an alternating current of a determined frequency and amplitude; and a signal processing circuit for subjecting output voltages induced in the liquid level detecting coil and in the temperature compensating coil to linear detection and then determining the ratio of the thus detected outputs, thereby detecting the level of the liquid metal.

Abstract: An apparatus for detecting the leakage of liquid sodium includes a cable-like sensor adapted to be secured to a wall of piping or other equipment having sodium on the opposite side of the wall, and the sensor includes a core wire electrically connected to the wall through a leak current detector and a power source. An accidental leakage of the liquid sodium causes the corrosion of a metallic layer and an insulative layer of the sensor by products resulted from a reaction of sodium with water or oxygen in the atmospheric air so as to decrease the resistance between the core wire and the wall. Thus, the leakage is detected as an increase in the leaking electrical current. The apparatus is especially adapted for use in detecting the leakage of liquid sodium from sodium-conveying pipes or equipment in a fast breeder reactor.

Abstract: A nuclear fuel rod is made up of a stack of pellets of fuel material and a cladding or sheathing tube is provided. A metallic supporting structure is interposed between the pellet stack and an end plug of said cladding tube. The supporting structure can maintain the original shape under the normal operating reactor conditions, but when an excess stress is applied to the supporting structure, a mechanical break is produced in the supporting structure to reduce its supporting length, otherwise the excess stress would be exerted on said cladding tube in the vicinity of the end plug joints and might cause failure of the fuel rod.

Abstract: A fuel assembly spacer for a nuclear reactor, the spacer having a plurality of spring with a uniform spring strength and arranged symmetrically around the outer periphery of the spacer so that the fuel assembly can be coaxially disposed with respect to a coolant duct. This spacer serves to maintain as uniform a gap as possible between the inner wall of the coolant duct and each outermost fuel rod in the fuel assembly so that the flow of the coolant keeps it symmetry in the section of the coolant duct, thereby improving the thermal performance of the fuel assembly.

Abstract: An inspection machine for detecting flaws in the surface of cylindrical fuel pellets, which comprises a pellet infeed section for successively transporting pellets to be inspected, a conveyer section for successively conveying delivered pellets to a plurality of inspection points, a plurality of inspection stations for detecting, at each inspection point, flaws at the corners, peripheral surface and end faces of the pellets by utilizing variations in back pressure prevailing in a sensor caused by the contact of an air stream with said flaws, an unacceptable pellet rejection station for rejecting pellets assessed to be unacceptable at any inspection station, and an acceptable pellet outfeed section for successively collecting pellets assessed as being acceptable.

Abstract: There is provided a process for continuous preparation of uranium tetrafluoride hydrate which comprises the steps of continuously feeding uranous solution and hydrofluoric acid into the lower section of a reaction vessel to produce crystal particles of uranium tetrafluoride hydrate causing the crystal particles to float up and be suspended in the upper section of the reaction vessel by agitation; in which section the crystal particles grow and then precipitating and discharging the thus grown crystal particles from the bottom of the vessel, while causing waste solution to overflow from the top of the vessel. There is also provided an apparatus to accomplish the aforementioned process.

Abstract: A method of measuring surface roughness of an object indirectly according to a tracer method by forming two different kinds of replicas. The first replica is made of a flexible material which can be easily stripped off from either the object surface or from the surface of the second replica. The second replica is made of a material with high hardness so that it will not suffer from any scratch or flaw from the tracer even when it hits the replica. Surface configuration of the object to be measured is transferred to the first replica and the surface configuration of the first replica is then transferred to the second replica, and surface roughness of this second replica is measured with a tracer.

Abstract: A method and an apparatus for removing hydrogen and other impurities contained in liquid metal. The liquid metal containing hydrogen and other impurities is cooled below their saturation temperature to precipitate hydrogen and other impurities in the form of various compounds of the metal, and the precipitate is trapped and accumulated. The thus accumulated precipitate is then dissolved in a small amount of liquid metal having a temperature at least above said saturation temperature to produce high temperature liquid metal having a high hydrogen concentration. The high temperature liquid metal is contacted with one side of a metal membrane having a hydrogen permeability, another side of which being at reduced pressure, thereby selectively removing hydrogen in gaseous state from the liquid metal.

Abstract: An improved Purex wet recovery process including the step of extracting and separating uranium and plutonium simultaneously from the fission products in the presence of nitric acid and nitrous acid by using a multistage extractor unit having an extracting section and a washing section is provided for separating and recovering neptunium simultaneously with uranium and plutonium contained in spent nuclear fuel. The improved method comprises the steps of maintaining the nitrous acid concentration in said extracting section at a level suited for effecting oxidation of neptunium from (V) to (VI) valence, while lowering the nitrous acid concentration in said washing section so as to suppress reduction of neptunium from (VI) to (V) valence, and maintaining the nitric acid concentration in said washing section at a high level.

Abstract: A method and an apparatus for continuously measuring the hydrogen concentration in argon gas containing hydrogen and other impurities. The argon gas containing impurities is continuously passed through a high temperature metal getter to thereby remove impurities other than hydrogen from the argon gas and produce a two-component mixture of gases consisting of argon and hydrogen. The two-component gas is then continuously introduced to a thermal conductivity detector and the hydrogen concentration can be determined from the detected thermal conductivity.