• KSBB Journal
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• v.18 no.5
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• pp.418-423
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• 2003

A laboratory jar fermenter was modified to measure the duration for cooling water supply and the temperatures of the coolant at the inlet and outlet of water jacket. Successful operation of temperature control and on-line measurement was achieved by adjusting optimum parameters of the Proportion-Integral-Derivative temperature controller. The variables measured on-line were used to estimate cooling rates from empirical equations comprised of the time period of cooling water supply and the temperatures of coolant. The measured cooling rate showed a good correlation to the specific growth rate during batch cultivation of E. coli. Cooling rate was measured and applied to programmed cell growth in a fed-batch cultivations. Three fed-batch cultivations were demonstrated by feeding substrate to follow the programmed cooling rates increasing exponentially.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.152-161
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• 2022

We analyzed mitigation strategies for steam generator tube rupture (SGTR) accidents using MARS code under both full-power and low-power and shutdown (LPSD) conditions. In general, there are two approaches to mitigating SGTR accidents: supplementing the reactor coolant inventory using safety injection systems and depressurizing the reactor coolant system (RCS) by cooling it down using the intact steam generator. These mitigation strategies were compared from the viewpoint of break flow from the ruptured steam generator tube, the core integrity, and the possibility of the main steam safety valves opening, which is associated with the potential release of radiation. The "cooldown strategy" is recommended for break flow control, whereas the "RCS make-up strategy" is better for RCS inventory control. Under full power, neither mitigation strategy made a significant difference except for on the break flow while, in LPSD modes, the RCS cooldown strategy resulted in lower break and discharge flows, and thus less radiation release. As a result, using the cooldown strategy for an SGTR under LPSD conditions is recommended. These results can be used as a fundamental guide for mitigation strategies for SGTR accidents according to the operational mode.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1518-1527
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• 2023

A method was proposed for in-situ evaluating the thickness and resistivity of the oxide/hydroxide film formed on the surface of aluminum alloy exposed to sump water formed in the containment after a loss-of-coolant accident. The evaluation entailed fitting a model for the film impedance, which has film thickness and other variables describing the resistivity profile of the film along its thickness direction as fitting parameters, to the practically measured electrochemical impedance data. The obtained resistivity profiles implied that the films formed at pHs_25℃ 7, 8, 9, 10, and 11 all had a duplex structure; compared to the outer layer in contact with the solution, the inner layer of the film had a much higher resistivity and was inferred to be denser and provide most of the protectiveness of the film. Both the thickness and the total resistance of the film decreased with the increasing solution pH_25℃, suggesting that the films formed in more alkaline solutions had less protectiveness against corrosion, consistent with the increasing aluminum alloy corrosion rates previously identified.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.85-91
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• 1997

Air grinding time in grinding process has a great effect on its efficiency due to low feedrate. This paper presents a reduction methos of air grinding time in cylindrical plunge grinding operation. Tje reduction of air grinding time is accomplished by finding the distance between contact point and rising point of ultra- sonic signal of the grinding wheel to workpiece. It uses a variation of sound signal generated by the flow of coolant when the grinding wheel approaches to workpiece. The ultrasonic sensor with 23 kHz center fre- quency and 8 kHz bandwidth is used to find the nearest approaching point(NAP). Monitoring and control system of the grinding conditions is implemented with CNC controller to control feedrate override and ultrasonic sensor to find NAP. The experimental result shows that the ultrasonic signal is a good measure- ment to find NAP. But it needs the considerations for the effect of the relationship between flowrate of coolant and diameter of workpiece.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.922-932
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• 2024

This paper presents the design features and preliminary design analysis results of the Wielenga Innovation Static Salt Reactor (WISSR). The WISSR incorporates features that make it both flexible and inherently safe. It is based on innovative technology that controls a nuclear reactor by moving molten salt fuel into or out of the core. The reactor is a low-pressure, fast spectrum transuranic (TRU) burner reactor. Inherent shutdown is achieved by a large negative reactivity feedback of the liquid fuel and by the expansion of fuel out of the core. The core is made of concentric, thin annular fuel chambers containing molten fuel salt. A molten salt coolant passes between the concentric fuel chambers to cool the core. The core has both fixed and variable volume fuel chambers. Pressure, applied by helium gas to fuel reservoirs below the core, pushes fuel out of a reservoir and up into a set of variable volume chambers. A control system monitors the density and temperature of the fuel throughout the core. Using NaCl-(TRU,U)Cl₃ fuel and NaCl-KCl-MgCl₂ coolant, a road-transportable compact WISSR core design was developed at a power level of 1250 MWt. Preliminary neutronics and thermal-hydraulics analyses demonstrate the technical feasibility of WISSR.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.230-233
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• 1999

The design and implementation of thyristor water cooling control systems in considered in this pape Coolant water is pumped through the thyristor heat sinks where heat is transferred from the thyristo to the water. This water is then pumped through outdoor air-to-water heat exchangers where heat I transferred to the outside air. Since the water must be pure, it is filtered and de-ionized. Also the water temperature must be below dew-point temperature. Redundant pumps, outdoor heat exchangers, power supply system, controller monitoring system are provided for system reliability and availability.

• Korean journal of applied entomology
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• v.60 no.2
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• pp.203-214
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• 2021

This study aimed at establishing a packaging standardization method that allows the maintenance of biological control agents product quality during delivery. First, based on the results of distribution status analysis of biological control agent products from four manufacturers, we confirmed that the mean temperature was maintained at 25.6℃ (minimum and maximum temperatures.: 18.1 and 30.7℃, respectively) inside the packaging box of each company for 36-48 h. To establish the optimal packaging method for each season, seven external temperature conditions were set ranging between 0℃ and 30℃ at intervals of 5℃. In addition, we evaluated internal temperature maintenance performance for each coolant pack handling method and determined 14 packaging combinations. A packaging combination that maintained a temperature of 3℃ - 9.9℃ at each external temperature conditions was considered efficient. This temperature range is close to a lower developmental threshold at which the biological control agents can survive with minimum energy for 12 h (direct delivery time), or 36-48 h (general delivery time) after packaging.

• Journal of Radiation Protection and Research
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• v.14 no.1
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• pp.34-45
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• 1989

The habitability of a reactor control room in a French 1300 MWe P'4 type PWR has been evaluated through the exposure dose assessment for the reactor operator following a Loss of Coolant Accident. The main hypotheses adopted in this evaluation are based on the French Standard Safety Analysis Report. A simple computer program, named COREX(Control Room EXposure), was developed to calculate : the time-integrated radioactivities released from the reactor building, the volume factors for radionuclides concerned and the resulting time-integrated external whole body and internal thyroid doses to the reactor operators staying in the control room up to 30 days following the LOCA. The results obtained in this study, on the whole, well agreed with those proposed by the EDF(Electricite de France) except for the case of the whole body exposure, which was attributed to the differences in the volume factors for the radionuclides concerned.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.3
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• pp.644-654
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• 2001

In this paper, an electronic control unit of the automobile engine for optimal fuel injection an spark timing control has been designed and developed. This system includes hardware and software for a precise control of fuel injection and ignition timing. Especially, the crank angle sensor provides two separate signals: One is the position signal (POS) which indicates 180 degree pulses per revolution, and the other is the reference signal (REF) that represents each cylinder individually. Consequently, the developed engine control system has been able to control fuel injection and ignition timing more quickly and accurately. Through the experiment, it has been found that the fuel injection duration and the position of MBT have been influenced by coolant temperature, air flow rate and engine speed.