• Journal of Welding and Joining
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• 제14권3호
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• pp.58-65
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• 1996

The work presents the experimental results concerning the local softening of Diesel motor cylinders with plasma using a specialized plasma generator.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1367-1370
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• 1997

This paper presents a vision algorithm for finding the centers of steam generator tubes using the generalized symmetry transform, which is used for ECT(Eddy Current Test) of steam generator tubes in nuclear power plants. The geometrical properties of the image representing steam generator tubes shows that they have amost circular or somewhat elliptic appearances and each tube has strong symmetry about its center. So we apply the generalized symmetry transform to finding centers of steam geneator tubes. But applying the generalized symmetry transform itself without any modification gives difficulties in obtaining the exact centers of steam generator tubes. But applying the generalized symmetry transform itself without any modification gives difficulties in obtaining the exact centers of tubes due to the shadow effect generated by the local light installed inside steam generator. Therefore we make the generalized symmetry transform modified, which uses a modified phase weight function in getting the symmetry magnitude in order to overcome the misleading effect by the local light. The experimental results indicate that the proposed vision algorithm efficiently recongnizes centers of steam generator tubes.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1784-1791
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• 2020

The 14 MeV neutron generator facility is being developed by the Institute for Plasma Research India to conduct the lab scale experiments related to Indian breeding blanket system for ITER and DEMO. It will also be utilized for material testing, shielding experiments and development of fusion diagnostics. Occupational radiation exposure control is necessary for the all kind of nuclear facilities to get the operational licensing from governing authorities and nuclear regulatory bodies. In the same way, the radiation exposure for the 14 MeV neutron generator facility at the occupational worker area and accessible zones for general workers should be under the permissible limit of AERB India. The generator is designed for the yield of 10¹² n/s. The shielding assessment has been made to estimate the radiation dose during the operational time of the neutron generator. The facility has many utilities and constraints like ventilation ducts, accessible doors, accessibility of neutron generator components and to conduct the experiments which make the shielding assessment challenging to provide proper safety for occupational workers and the general public. The neutron and gamma dose rates have been estimated using the MCNP radiation transport code and ENDF -VII nuclear data libraries. The ICRP-74 fluence to dose conversion coefficients has been used for the assessment. The annual radiation exposure has been assessed by considering 500 h per year operational time. The provision of local shield near to neutron generator has been also evaluated to reduce the annual radiation doses. The comprehensive results of radiation shielding capability of neutron generator building and local shield design have been presented in the paper along with detailed maps of radiation field.

• 대한기계학회논문집A
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• 제28권11호
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• pp.1813-1821
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• 2004

Until now, the 40% of wall thickness criterion, which is generally used for the plugging of steam generator tubes, has been applied only to a single cracked geometry. In the previous study by the authors, a total number of 9 local failure prediction models were introduced to estimate the coalescence load of two collinear through-wall cracks and, then, the reaction force model and plastic zone contact model were selected as the optimum ones. The objective of this study is to estimate the coalescence load of two collinear through-wall cracks in steam generator tube by using the optimum local failure prediction models. In order to investigate the applicability of the optimum local failure prediction models, a series of plastic collapse tests and corresponding finite element analyses for two collinear through-wall cracks in steam generator tube were carried out. Thereby, the applicability of the optimum local failure prediction models was verified and, finally, a coalescence evaluation diagram which can be used to determine whether the adjacent cracks detected by NDE coalesce or not has been developed.

• 한국군사과학기술학회지
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• 제15권1호
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• pp.66-74
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• 2012

The virtual target signal generator was developed to verify the shipborne tracking radar performance. It was used to DRFM(Digital RF Memory) method to generate the virtual moving targets. The target signal includes Doppler shift and RCS according to the target motion. And the signal generator can make jamming signal and clutter to test shipborne radar performance at real environmental condition. This paper described the functional diagram and the hardware configuration items to meet the test requirements for the tracking radar. And it showed the critical design points for the sub-systems. The signal generator which was developed in this paper shared the operational information of the radar with the radar command and control part. To test the frequency agility of the radar, it had the local oscillator which could do high speed frequency switching according to radar information. By communicating between the signal generator and the radar command and control part, the local oscillator of signal generator could be controlled every pulse. It reduced the instantaneous bandwidth of signal generator and minimized the spurious. So it lowered the probability of generating wrong targets.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.494-499
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• 2011

One of the devices to prevent separated flow over a wing or a flap at high angle of attack is a vortex generator. In the present work, we numerically study the flow around a low-profile or micro vortex generator whose height is less than local boundary layer thickness which can delay separation with a minimum drag penalty owing to its very small wetted surface area. As a first step toward a parametric study to efficiently design this MVG flow control system, we simulate the flow around a single MVG on a flat plate. For the simulation, we employ OpenFOAM with Launder-Sharma ${\kappa}$-epsilon model. The analysis results are validated by comparing with experimental results of a rectangular MVG at an angle of attack of 10 degrees whose height is 20% of local boundary layer. Important results and aspects of this numerical study are discussed. We also simulate the flow around rectangular, triangular and trapezoidal MVGs and the results are compared

• 비파괴검사학회지
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• 제31권5호
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• pp.543-551
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• 2011

Steam generator tubes for nuclear power plants contain the local shape transitions on their inner or outer surface such as dent, bulge, over-expansion, eccentricity, deflection, and so on by the application of physical force during the tube manufacturing and steam generator assembling and by the sludge (that is, corrosion products) produced during the plant operation. The structural integrity of tubes will be degraded by generating the corrosive crack at that location. The profilometry using the traditional bobbin probes which are currently applied for measuring the profile change of tubes gives us basic information such as axial locations and average magnitudes of deformations. However, the three-dimensional quantitative evaluation on circumferential locations, distributional angle, and size of deformations will have to be conducted to understand the effects of residual stresses increased by local deformations on corrosive cracking of tubes. Steam generator tubes of Korean standard nuclear power plants expanded within their tube-sheets by the explosive expansion method and suffered from corrosive cracks in the early stage of power operation. Thus, local deformations of steam generator tubes at the top of tube-sheet were measured with an advanced rotating probe and a laser profiling system for the two cases where the tubes expanded by the explosive expansion method and hydraulic expansion. Also, the trends of eccentricity, deflection, and over-expansion of tubes were evaluated. The advanced eddy current profilometry was confirmed to provide accurate information of local deformations compared with laser profilometry.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.676-678
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• 2003

The present support for local coal generator amounts to above 100 billion won every year by electricity fund collected from general consumer. This paper presents the appropriate supporting policy for local coal generator in TWBP market in the future.

• 동력기계공학회지
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• 제10권3호
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• pp.38-44
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• 2006

Failure assessment of steam generator tube are very important for the integrity of energy plants. In pipes of energy plants, sometimes, the local wall thinning may result from severe erosion-corrosion damage. Recently, the effects of local wall thinning on fracture strength and fracture behavior of piping system have been well studied. In this paper, the elasto-plastic analysis is performed by FE code ANSIS on steam generator tube with wall thinning. We evaluated the failure mode, fracture strength and fracture behavior from FE analysis. It was possible to predict the crack initiation point by estimating true fracture ductility under multi-axial stress conditions at the center of the thinned area.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.61-66
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• 2003

Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator.