• Environmental Engineering Research
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• v.12 no.5
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• pp.211-217
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• 2007

Polycyclic aromatic hydrocarbon growth from cyclopentadiene (CPD) pyrolysis was investigated using a laminar flow reactor operating in a temperature range of 600 to $950^{\circ}c$. Major products from CPD pyrolysis are benzene, indene and naphthalene. Formation of observed products from CPD is explained as follows. Addition of the cyclopentadienyl radical to a CPD $\pi$-bond produces a resonance-stabilized radical, which further reacts by one of three unimolecular channels: intramolecular addition, C-H bond $\beta$-scission, or C-C bond $\beta$-scission. The intramolecular addition pathway produces a 7-norbornenyl radical, which then decomposes to indene. Decomposition by C-H bond $\beta$-scission produces a biaryl intermediate, which then undergoes a ring fusion sequence that has been proposed for dihydrofulvalene-to-naphthalene conversion. In this study, we propose C-C bond $\beta$-scission pathway as an alternative reaction channel to naphthalene from CPD. As preliminary computational analysis, Parametric Method 3 (PM3) molecular calculation suggests that intramolecular addition to form indene is favored at low temperatures and C-C bond $\beta$-scission leading to naphthalene is predominant at high temperatures.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.2
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• pp.87-93
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• 2020

Seismic responses due to the dynamic coupling between a primary structure and secondary system connected to a structure are analyzed in this study. The seismic responses are compared based on dynamic coupling criteria and according to the error level in the natural frequency, with the recent criteria being reliant on the error level in the spectral displacement response. The acceleration responses and relative displacement responses of a primary structure and a secondary system for a coupled model and two different decoupled models of two degrees-of-freedom system are calculated by means of the time integration method. Errors in seismic responses of the uncoupled models are reduced with the recent criteria. As the natural frequency of the secondary system increases, error in the natural frequency decreases, but seismic responses of uncoupled models can be underestimated compared to that of coupled model. Results in this paper can help determine dynamic coupling and predict uncoupled models' response conservatism.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2033-2042
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• 1993

In conventional SCC susceptibility test, there are constant strain test, constant load test, slow strain rate test(SSRT) and K$_{ISCC}$ test. Among them, the SSRT method is much more aggressive in producing SCC than the other tests, so that the test time of it is considerably reduced. But this SSRT method has mostly been worked using the uniaxial tensile specimen untill now. Therefore, the SSRT method using the tensile specimen(Ten-SSRT) has much difficulty in SCC susceptibility evaluation of a localized region like weldment and the advantage material of high order. Recentely, the small punch(SP) test method using miniaturized small specimen is the very effective test method for fracture strength evaluation of a localized region like weldment and fusion reactor wall irradiated in the nuclear power plant. This paper investigated the possibility of SCC susceptibility evaluation by the SP-SSRT method using the miniaturized small specimen. Therefore, we obtained the result that the SP-SSRT had the possibility for the evaluations of SCC susceptibility for shorter time to corrosive environment compare to Ten-SSRT which was conventional method.

• Journal of the Korean Ceramic Society
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• v.21 no.3
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• pp.231-238
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• 1984

Heavy metal fluoride glasses exhibit considerable promise as high transparency materials from the UV to the IR. These glasses are prepared by fusion of the mixture of metal fulorides($ZrF_4$, $BaF_2$, $LaF_3$ etc) at 800-1, 00$0^{\circ}C$ under the inert$(N_2)$ or reactive ($CCl_4$, $Cl_2$) atmosphere following the casting into glass on cooling. Infrared absorption at the 3, 400 cm-1 -OH peak has been measured as a function of thickness for several ZrF-$BaF_2$-LaF and $HfF_4$-$BaF_2$-$LaF_3$ glasses to separate contributions from bulk and surface -OH. For glasses melted under $CCl_4$ reactive atmosphere the peak is due almost entirely to surface-OH. and melting in a closed reactor was best for removing -OH. In ambient atmosphere the -OH peak exhibited no time dependence over a 30 d period indicating a very small rate of surface attack by atmospheric H2O. Removal of -OH absorption processing was generally easier and more complete for the $BaF_2$/ThF4-glasses than for the $ZrF_4$-or $HfF_4$-based glasses.

• Journal of the Korean Ceramic Society
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• v.35 no.5
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• pp.451-457
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• 1998

$Li_2$$ZrO_3$ powder which is one of the candidates of breeding materials for the fusion reactor was syn-thesized by a precipitation-combustion process. Although precipitates from the reaction between zirconium nitrate and citric acid were existed in a precursor solution. $Li_2$$ZrO_3$ could easily be obtained by using the mixed fuel of urea and citric acid in stoichiometric composition. The phases of as-synthesized powder con-sisted of $Li_2$$ZrO_3$ and small amounts of $Li_6$$Zr_2O_3$ and $Li_2$$ZrO_3$ The latter phases disappeared after the cal-cination at $1100^{\circ}C$ for 2 h. The primary particle size and the specific surface area of as-synthesized powders were smaller than 20nm and 10-14 $M^2$/g, respectively. The primary particle size of the precipitation-combustion synthesized powders was affected by the size of precipitates present in a precursor solution.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1161-1162
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• 2006

In order to overcome the recrystallization embrittlement and irradiation embrittlement of Mo, which are major problems for its fusion applications, internally nitrided Mo alloys were prepared by a novel multi-step internal nitriding. Neutron irradiation was performed in the Japan Material Testing Reactor (JMTR). After irradiation, nitrided Mo alloys exhibited $\iota$ ower ductile-brittle transition temperature than irradiated TZM. These results suggested that multi-step internal nitriding was effective to the improvement in the embrittlement by irradiation. Transmission electron microscope observation revealed that TiN particles precipitated by nitriding acted as a sink for irradiation-induced defects.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2290-2298
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• 2020

The damage of first wall material in fusion reactor due to the bubbles caused by plasma has been studied by introducing a relation between the von Mises equivalent stress and the temperature field. The locations and shapes of the bubbles and the synergetic effect between the different bubbles under steady operational conditions have been studied using the finite elements method. Under transient heat loads, plastic deformations have been found to occur, and are significantly enhanced by the presence of the bubbles. The calculated concentration locations of von Mises equivalent stress are well consistent with the observed crack positions of the tungsten surface in many test experiments. Our simulations show that the damage of the bubbles is not severe enough to lead to catastrophic failure of the tungsten armor; however, it can cause local and gradual detachment of tungsten surface, which provides a reasonable explanation for the observed pits and rough or hairy surface morphology etc. Considering the transient heat loads, the lower bound of the security thickness of the tungsten tile is estimated to be greater than 2 mm.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2251-2260
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• 2021

The motion control of the divertor maintenance system of the China Fusion Engineering Test Reactor (CFETR) was studied in this paper, in which CFETR Multi-Functional Maintenance Platform (MFMP) was simplified as a parallel robot for the convenience of theoretical analysis. In order to design the motion controller of parallel robot, the kinematics analysis of parallel robot was carried out. After that, the dynamic modeling of the hydraulic system was built. As the large variation of heavy payload on MFMP and highly nonlinearity of the system, A Fuzzy-PID controller was built for self-tuning PID controller parameters by using Fuzzy system to achieve better performance. In order to test the feasibility of the Fuzzy-PID controller, the simulation model of the system was built in Simulink. The results have showed that Fuzzy-PID controller can significantly reduce the angular error of the moving platform and provide the stable motion for transferring the divertor.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.655-659
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• 2020

Hydrogen isotopes (i.e. deuterium and tritium) are supplied to the tokamak in the International Thermonuclear Experimental Reactor (ITER) fuel cycle. One important part of the ITER fuel cycle is the recycling of unused fuel back to the tokamak, as almost 99 % of fuel is unburned during fusion reaction. For this, cryogenic distillation has been used in the isotope separation system (ISS) of ITER, but this technique tends to be energy-intensive and to have low selectivity (typically below 1.5 at 24 K). Recently, efficient isotope separation by porous materials has been reported in the so-called quantum sieving process. Hence, in this study, hydrogen isotope adsorption behavior is studied using chemically stable ZIF-11. At low temperature (40 K ~ 70 K), the adsorption increases and the sorption hysteresis becomes stronger as the temperature increases to 70K. Molar ratio of deuterium to hydrogen based on the isotherms shows the highest (max. 14) ratio at 50 K, confirming the possibility of use as a potential isotope separation material.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2708-2715
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• 2021

The Multi-Purpose Overload Robot (CMOR) is a key subsystem of China Fusion Engineering Test Reactor (CFETR) remote handling system. Due to the long cantilever and large loads of the CMOR, it has a large rigid-flexible coupling deformation that results in a poor position accuracy of the end-effector. In this study, based on the Levenberg-Marquardt algorithm, the spatial grid, and the linearized variable load principle, a variable parameter compensation model was designed to identify the parameters of the CMOR's kinematics models under different loads and at different poses so as to improve the trajectory tracking accuracy. Finally, through Adams-MATLAB/Simulink, the trajectory tracking accuracy of the CMOR's rigid-flexible coupling model was analyzed, and the end position error exceeded 0.1 m. After the variable parameter compensation model, the average position error of the end-effector became less than 0.02 m, which provides a reference for CMOR error compensation.