[en] A three dimensional thermal analysis code TBLOCK was developed to analyze the temperature distribution in the fuel stack of the VHTR for various flow rate or heat generation rate in the horizontal direction. This computer code simulates one column of fuel blocks. The temperature distributions in the horizontal plane and in the axial direction were solved by the finite element method as well as by the finite differential method. This report describes the outline of analytical model and numerical method of the code. (author)

[en] The Japan Atomic Energy Research Institute (JAERI) has been planning the construction of High Temperature Engineering Test Reactor (HTTR) which in 30MW in thermal power, 850degC and 950degC in outlet coolant temperature and 40kg/cm²G in primary coolant pressure. In the HTTR, coolant flows upward in channels between core and Reactor Pressure Vessel (RPV), then mixed in the upper plenum and flows into the core. This report presents the evaluation results of the core inlet temperature, which is a fundamental value of maximum fuel temperature calculation. Temperature behavior at the core side channel is calculated by FEM code and temperature mixing characteristics is calculated by thermal-hydraulic code 'STREAM'. The evaluation error of core inlet temperature is one of the hot spot factors for the maximum fuel temperature calculation. (author)

[en] The thermal mixing behavior in the upper plenum of the High Temperature engineering Test Reactor (HTTR) was investigated by the thermal-hydraulic analysis code STREAM. This code is vectrized so that a large and complicated system can be treated. Taking into consideration that there are many structures in the upper plenum and coolants with different temperature flow into the core being mixed in the upper plenum, a three-dimensional calculation was carried out to quantify the magnitude in thermal mixing in the upper plenum and a mesh effect and magnitude of thermal mixing were clarified. (author)

[en] This report presents the verification results of in-vessel thermal and hydraulic analysis code, ''FLOWNET'', for the High Temperature engineering Test Reactor (HTTR). The experimental results by 1 column test facility and in-core structure test section (HENDEL T₂) were used in course of validation of accuracy of the code and of adequateness of data-base. Verification results showed quite good agreement with the experimental results. (author)

[en] Experimental studies on thermal and hydraulic performance of a fuel channel has been performed with the single-channel test rig of the fuel stack test section (T₁) in order to contribute the licensing of the JAERI's high-temperature gas-cooled reactor (HTTR). Present report showed experimental results obtained by a high temperature test that helium gas was heated up to 1000degc, using a simulated fuel rod of which heat flux distribution was uniform in the axial direction and varied like an exponential and cosine functions, respectively. In this test, friction factors of a fuel channel and heat transfer coefficients of a fuel rod were well correlated, respectively. These data agreed well with previous results. On the other hand, it was showed that there was almost no difference of heat transfer coefficients between three types of the heat flux distributions. (author)

[en] This report presents the verification results of fuel temperature analysis code ''TEMDIM'' for core thermal and hydraulic design of the High Temperature Engineering Test Reactor (HTTR), which has been designed at the Japan Atomic Energy Research Institute (JAERI). The experimental results obtained by the single-channel test rig of HENDEL fuel stack test section (T_1-s) were used for the verification of TEMDIM code. The verification results show the adequateness and conservativeness of fuel temperature analysis methods in core thermal and hydraulic design. (author)

[en] Nonuniform power distribution test was performed with the multi-channel test rig of the fuel stack test section (T₁) in order to contribute the licensing of the JAERI's High-Temperature Engineering Test Reactor (HTTR). In the test, helium gas was heated up to 750degC under asymmetric and slantwise power distributions realized by changing input electric powers of 12 simulated fuel rods respectively. Experimental results showed that the distribution of helium gas flow rate was influenced by the temperature distortion in the mock-up fuel stack. Calculated results with the numerical thermal analysis code indicated that the temperature distortion in the fuel stack was flattened by the thermal conduction in the graphite block. (author)

[en] This report presents the results of quantitative evaluation on the effects of the dominant parameters on the maximum fuel temperature in the core thermal hydraulic design of the High Temperature Engineering Test Reactor(HTTR) of 30 MW in thermal power, 950 deg C in reactor outlet coolant temperature and 40 kg/cm² G in coolant pressure. The dominant parameters investigated are 1) Gap conductance. 2) Effect of eccertricity of fuel compacts in graphite sleeve. 3) Effect of spacer ribs on heat transfer coefficients. 4) Contact probability of fuel compact and graphite sleeve. 5) Validity of uniform radial power density in the fuel compacts. 6) Effect of impurity gas on gap conductance. 7) Effect of FP gas on gap conductance. The effects of these items on the maximum fuel temperature were quantitalively identified as hot spot factors. A probability of the appearance of the maximum fuel temperature was also evaluated in this report. (author)

[en] Experimental studies on thermal and hydraulic performance of a fuel column have been performed with the multi-channel test rig of the fuel stack test section (T_1-M) installed in the helium engineering demonstration loop (HENDEL). Present report showed experimental results and numerical analysis obtained by a high temperature test that helium gas was heated up to 1000 degC, using 12 simulated fuel rods in T_1-M. Under the conditions of uniform heating of 12 simulated fuel rods installed in the fuel block, it was found that a flow rate distribution of helium gas in 12 fuel channels was almost uniform, radiant heat from the fuel rod was increased with surface temperatures of the fuel rod more than 20 % in laminar flow region, and average heat transfer coefficients agreed with the correlation obtained by the single-channel test rig. On the other hand, the temperature distribution in the horizontal cross section of the fuel block with power distributions of 12 fuel rods was calculated with a three dimensional thermal analysis code, and the temperature difference was found to be small. (author)

[en] The optimization of uranium isotope distribution and burnable poison of the High Temperature Engineering Test Reactor (HTTR) with the thermal power of 30MW has been done to achieve the reactor outlet coolant temperature of 950degC. The uranium isotope distribution is adjusted to obtain the optimal power distribution with which the fuel temperature is minimized. The burnable poison is used to reduce the excess reactivity so that the power distribution is not disturbed through the control rod inserted in core. The core of which the maximum fuel temperature is kept under the limited temperature has been constructed from this optimization. This report presents the optimization process of uranium isotope distribution and burnable poison and its result. (author)