[en] The experimental results on the hydrogen permeation behaviour of different high temperature alloys under steam/methane reforming conditions at 650°C are communicated in the context of sample parameters and the operational data of the facility ''AUWARM'' during this test run, called 100/2. Comparisons are made with previous experiments, and some post- exposure investigations on the temperature and pressure dependency of permeation rates through oxide-protected sample walls are evaluated, Final interpretations of the experimental results are not comprised in this report, because the post-test metallography is not yet completed. (author)

[en] In a HTGR reactor having helium as coolants, a helical tube-type intermediate heat exchanger is used, the temperature of helium at an exit of the reactor is set to 950degC, and the temperature at an inlet thereof is set to 400degC to 450degC as proposed so far, to enhance power generation efficiency of a helium turbine system. In this case, an inner heat insulation layer having a corrugated thin metal plate structure is disposed to the inner side of the reactor to separate a temperature boundary and a pressure boundary thereby lowering temperature of a pressure vessel in order to ensure the integrity of the reactor container caused by the temperature elevation of the inlet. In addition, blade end loss is minimized by using a metal material suitable to dynamic helium turbine blades and performing three dimensional calculation, as well as the turbine system is optimized to attain a power generation thermal efficiency of about 45%. In addition, the thermal energy generated from the reactor is utilized for public welfare and agricultural industries in the area of the location of the plant in addition to provide power generation, and a flush-type sea water desalinating device is disposed to increase the entire thermal efficiency of the power plant to about 90%. (N.H.)

[en] The present paper deals with a gas-exchange process of a light gas in a reverse U-shaped tube with a heavy gas outside. The reverse U-shaped tube consists of two vertical pipes; one is at high temperature and the other at low temperature. In order to investigate the gas-exchange process, one-dimensional mole conservation equations for the binary gas mixture and for the gas species and a momentum-conservation equation for the gas mixture are numerically solved to calculate the variation of mole-fraction distributions of species A and B in the reverse U-shaped tube and the onset time of natural circulation of the heavy gas through the reverse U-shaped tube. The calculation is performed for both the cases where the density of the binary gas mixture is approximated and where the density is expressed by the equation of state for an ideal gas

[en] The present invention provides a helium cooling FBR type reactor as a novel energy system ensuring safety and reliability and being excellent as an energy source. Namely, in a primary circuit, helium undergoing heat generated by combustion of fission products of reactor core fuel rods, passing through an intermediate exchanger and cooling reactor control rods is circulated. In a secondary circuit, helium undergoing the heat from the primary circuit in the intermediate heat exchanger and forming a fluid for actuating a gas turbine generator is circulated. A flow channel external tube is disposed at a predetermined distance on the outside of a fuel cladding tube in which a reactor core fuel rod is sealed. A predetermined number of annular helium flow channel units having an annular flow channel between the fuel cladding tube and the flow channel external tube are disposed. With such a constitution, since the fluid of the primary and secondary circuits is an inert gas, and the fuel rod is sealed in the fuel cladding tube, there is no leakage of radioactive materials to the primary circuit. Accordingly, there is utterly no radioactive material in the secondary circuit passing through the intermediate heat exchanger. (I.S.)

[en] Purpose: In reactivating a copper reactant in a purification drum removing impurities in a helium gas used in a htgr type reactor, to carry out reactivation of the copper reactant while controlling the temperature so that it does not rise abnormally. Method: The temperature of a purification drum is maintained in the range of from 120 to 300 C, and an inset gas (such as nitrogen) in which a gas to be regenerated is mixed is supplied into said drum, thereby increasing the concentration of the gas to be regenerated by taking a sufficient time. In this case, the inert gas is circulated to be used. In this manner, the inert gas is circulated thereby preventing the abnormal rise of the temperature. (Kamimura, K.)

[en] A primary-pipe rupture accident is one of the design-basis accidents of a high-temperature gas-cooled reactor (HTGR). When the primary-pipe rupture accident occurs, air is expected to enter the reactor core from the breach and oxidize in-core graphite structures. This study is to investigate the air ingress phenomena and to develop the passive safe technology for the prevention of air ingress and of graphite corrosion. This paper describes the method for the prevention of air ingress into the reactor during the primary-pipe rupture accident. It is found that a safe cooling rate of the reactor core exists for the prevention of air ingress. The experimental results show that the natural circulation flow of air during the accident can be controlled by the method of helium gas injection into the reactor pressure vessel.

[en] Experimental study was performed on heat transfer of an open thermosyphon with constant wall heat flux. Water and aqueous glycerin were used as working fluids. Experimental range of modified Rayleigh Number was 1 x 10³ < Ra_m < 3 x 10⁵. Average and local heat transfer coefficients, vertical temperatures distributions of the tube wall and fluid at the center line of the tube, temperature fluctuation of the fluid were measured. Flow patterns were observed by adding tracer powder in the fluid. Fluid velocities were measured by L. D. V (Laser Doppler Velocimeter). Experimental results indicate that there exists three different heat transfer characteristics and corresponding flow patterns. For 1 x 10³ < Ra_m < 4 x 10³, flow was laminar and thermal boundary layer reaches near the center of the tube. Heat was exchanged between wall and descending flow. Wall temperature rose towards downward. For 4 x 10³ < Ra_m < 3 x 10⁴, no turbulence was observed in the flow and thermal boundary layer was localized in the vicinity of the wall. Wall temperature rose towards upward. For 3 x 10⁴ < Ra_m < 3 x 10⁵, flow is considerably disturbed by the mixing of upward and downward flow in the upper part of the tube. However, flow is almost laminar in the lower part of the tube. Reduction of flow rate induced by the flow mixing at high Ra_m would be one of the major causes of the deterioration of heat transfer from the Light hill's theory. (author)

[en] Purpose: To effectively remove heat from specimens in a reactor core and shorten the irradiation time. Constitution: As the cooling system for the specimens in a reactor, a heat pipe cooling system utilizing evaporization and condensation is additionally disposed in addition to the conventional cooling system. Specifically, cooling is conducted by either inserting heat pipes in the specimens or inserting the specimens directly in a heat pipe operation fluids. Since sodium, mercury and water are used as the heat pipe operation fluids and heat pipe cooling system is used, the heat removing performance is remarkably high and the specimens can be maintained at a uniform temperature. Further, the heat removing power can be controlled to easily set the specimens to a predetermined temperature. (Sekiya, K.)

[en] The net mass-exchange rate during Helium-Air exchange flow was measured in inclined rectangular channels and circular channels. The net mass-exchange rate was dependent on the shape of cross-section, that is, the rate in rectangular channels was significantly greater compared with that in circular channels. Moreover, it was also found that the rate in the narrow-rectangular channel is greater than that in the wide-rectangular channel. These results were discussed in connection with the velocity profiles visualized by smoke-wire method. (author)

[en] Air ingress by buoyancy-driven exchange flow occurs during a standpipe rupture accident in a high-temperature engineering test reactor (HTTR). The exchange flow of helium and air through annular and round tubes is investigated. The method of mass increment is applied to measure the exchange flow rate. A test cylinder with a small tube on the top is used for the experiment. The following results were obtained: The exchange velocity is largest for the short vertical round tube as compared with the orifice and long tube. In the annular tube, the exchange-velocity or the volumetric exchange flow rate decreases with the equivalent diameter of the annular passage under 6 mm. The annular tube is effective to reduce the air ingress flow rate from the broken standpipe of the HTTR. In the inclined round tube, the inclination angle for the maximum densimetric Froude number decreases with the increase of the length-to-diameter ratio of the tube for the helium-air system. On the other hand, this angle remains almost constant for the water-brine system. Flow visualization results indicate that the exchange flows through the inclined round tubes take place smoothly and stably in the separated passage of the tube. The flow pattern in the vertical annular tube seems to be similar to that in the inclined round tube