A Global Collision-Free Path Planning Using Parametric Parabola Through Geometry Mapping of Obstacles in Robot Work Space

Ihn Namgung 대한기계학회 1996 KSME International Journal Vol.10 No.4

Path Space Approach for Planning 2D Shortest Path Based on Elliptic Workspace Geometry Mapping

Ihn Namgung 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.1

A new algorithm for planning a collision-free path based on algebraic curve is developed and the concept of collision-free Path Space (PS) is introduced. This paper presents a Geometry Mapping (GM) based on two straight curves in which the intermediate connection point is organized in elliptic locus (δ. θ). The GM produces two-dimensional PS that is used to create the shortest collision-free path. The elliptic locus of intermediate connection point has a special property in that the total distance between the focus points through a point on ellipse is the same regardless of the location of the intermediate connection point on the ellipse. Since the radial distance, 8, represents the total length of the path, the collision-free path can be found as the GM proceeds from δ=0 (the direct path) to δ=δ_max(the longest path) resulting in the minimum time search. The GM of elliptic workspace (EWS) requires calculation of interference in circumferential direction only. The procedure for GM includes categorization of obstacles to reduce necessary calculation. A GM based on rectangular workspace (RWS) using Cartesian coordinate is also considered to show yet another possible GM. The transformations of PS among Circular Workspace Geometry Mapping (CWS GM), Elliptic Workspace Geometry Mapping (EWS GM), and Rectangular Workspace Geometry Mapping (RWS GM), are also considered. The simulations for the EWS GM on various computer systems are carried out to measure performance of algorithm and the results are presented.<br/>

Application of Quadratic Algebraic Curve for 2D Collision-Free Path Planning and Path Space Construction

Ihn Namgung 대한전기학회 2004 International Journal of Control, Automation, and Vol.2 No.1

Investigation of Burst Pressures in PWR Primary Pressure Boundary Components

Ihn Namgung,Nguyen Hoang Giang 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.1

In a reactor coolant system of a nuclear power plant (NPP), an overpressure protectionsystem keeps pressure in the loop within 110% of design pressure. However if the systemdoes not work properly, pressure in the loop could elevate hugely in a short time. It wouldbe seriously disastrous if a weak point in the pressure boundary component bursts andreleases radioactive material within the containment; and it may lead to a leak outside thecontainment. In this study, a gross deformation that leads to a burst of pressure boundarycomponents was investigated. Major components in the primary pressure boundary that isstructurally important were selected based on structural mechanics, then, they were usedto study the burst pressure of components by finite element method (FEM) analysis and bynumber of closed forms of theoretical relations. The burst pressure was also used as ametric of design optimization. It revealed which component was the weakest and whichcomponent had the highest margin to bursting failure. This information is valuable insevere accident progression prediction. The burst pressures of APR-1400, AP1000 andVVER-1000 reactor coolant systems were evaluated and compared to give relative marginsof safety.

KSNP^+ Reactor Vessel Head Drop Analysis for a 5.5M Free Fall

Ihn Namgung,Seung Ha Jeong,Dae Hee Lee,Taek Sang Choi 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.1

The KSNP^+ RV closure head drop analysis was carried out to assess the reactor core coolability in case of the RV closure head drop accident during the refueling operation. The analysis consists of a number of different RV head drop scenarios as the postulated accident events during refueling that include a concentric head drop case and three different cases of laterally offset head drop cases. The analysis was initiated due to the adoption of the IHA (Integrated Head Assembly) in the KSNP^+ reactor design, which increases the weight of the RV closure head assembly. Four different analysis models were developed that correspond to the RV head drop analysis scenarios. An in-house dynamic analysis code was used for the RV head drop analysis. The entire reactor internals and fuel assemblies are modeled by using lumped masses and spring elements. Because of the extreme load exerted by RV head drop, most members experience stresses that are beyond the elastic limits. A separate elastic-plastic analysis for some members was carried out and the resulting load-deflection curve was used as the stiffness of the element. The effect of water above the reactor vessel in the refueling pool was ignored for the conservative estimation of the analysis. The analysis shows that the concentric head drop is the most severe case of loading condition. It also reveals that the local deformation of some reactor internals and the fuel assemblies is occurred; however the primary membrane stresses are within the bound of allowable stress limits. Consequently the reactor core remains in coolable state.

Analysis of Fuelling Sequence and Fatigue Life for 4-Bundle Shift Refuelling Scheme in CANDU6 NPP

Namgung, Ihn 한국원자력학회 2002 Nuclear Engineering and Technology Vol.34 No.2

Investigation of Burst Pressures in PWR Primary Pressure Boundary Components

Namgung, Ihn,Giang, Nguyen Hoang Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.1

In a reactor coolant system of a nuclear power plant (NPP), an overpressure protection system keeps pressure in the loop within 110% of design pressure. However if the system does not work properly, pressure in the loop could elevate hugely in a short time. It would be seriously disastrous if a weak point in the pressure boundary component bursts and releases radioactive material within the containment; and it may lead to a leak outside the containment. In this study, a gross deformation that leads to a burst of pressure boundary components was investigated. Major components in the primary pressure boundary that is structurally important were selected based on structural mechanics, then, they were used to study the burst pressure of components by finite element method (FEM) analysis and by number of closed forms of theoretical relations. The burst pressure was also used as a metric of design optimization. It revealed which component was the weakest and which component had the highest margin to bursting failure. This information is valuable in severe accident progression prediction. The burst pressures of APR-1400, AP1000 and VVER-1000 reactor coolant systems were evaluated and compared to give relative margins of safety.

Path Space Approach for Planning 2D Shortest Path Based on Elliptic Workspace Geometry Mapping

Namgung, Ihn The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.1

A new algorithm for planning a collision-free path based on algebraic curve is developed and the concept of collision-free Path Space (PS) is introduced. This paper presents a Geometry Mapping (GM) based on two straight curves in which the intermediate connection point is organized in elliptic locus ($\delta$, $\theta$). The GM produces two-dimensional PS that is used to create the shortest collision-free path. The elliptic locus of intermediate connection point has a special property in that the total distance between the focus points through a point on ellipse is the same regardless of the location of the intermediate connection point on the ellipse. Since the radial distance, a, represents the total length of the path, the collision-free path can be found as the GM proceeds from $\delta$=0 (the direct path) to $\delta$=$\delta$$\_$max/(the longest path) resulting in the minimum time search. The GM of elliptic workspace (EWS) requires calculation of interference in circumferential direction only. The procedure for GM includes categorization of obstacles to .educe necessary calculation. A GM based on rectangular workspace (RWS) using Cartesian coordinate is also considered to show yet another possible GM. The transformations of PS among Circular Workspace Geometry Mapping (CWS GM) , Elliptic Workspace Geometry Mapping (EWS GM) , and Rectangular Workspace Geometry Mapping (RWS GM), are also considered. The simulations for the EWS GM on various computer systems are carried out to measure performance of algorithm and the results are presented.

KSNP+ 원자로덮개 5.5m 수직 낙하 시 원자로내부구조물 건전성 평가

남궁인(Ihn Namgung),정승하(Seung Ha Jeong),이대희(Dae Hee Lee),최택상(Taek Sang Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

Due to the application of Integrated Head Assembly (IHA) in KSNP+ reactor design, an investigation of<br/> reactor internals integrity is carried out to assure that the adoption of IHA does not affect the safety of reactor<br/> operation. One of the postulated accident events is the R.V. closure head fall from 5.5m high directly above<br/> the reactor vessel that may occur during the refueling operation. The analysis model consists of lumped mass<br/> elements of the entire reactor vessel and internals. Because of extreme load, separate elastic-plastic analyses<br/> are done for the members that undergo plastic deformation. The analysis verified that the stresses of the<br/> reactor internals and the fuel assemblies are within the bound of allowable stress limits and the integrity of the<br/> fuel assemblies is maintained.

Design Re-engineering of APR1400 Reactor Vessel

Mutegi Peter Mutembei,Ihn Namgung 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

This paper describes the conceptual re-engineering of the RV (Reactor Vessel) for the APR1400. The RV is classified as safety class 1 and therefore must adhere strictly to the rules of ASME BPVC section III, subsection NB and seismic category I. This study explores designing the RV by following the ASME guidelines and making a comparative study with the current design. Focus is on the determining the design parameters of RV major nozzles and their reinforcement, given that they present structural discontinuities that may weaken the nozzle opening if not compensated for adequately. The design parameters that are not derived from ASME code guidelines were referred from the APR1400 SSAR. The obtained parameters offered an input to creating a 3D model using the CATIA software 3D platform. A comparative study was done on the ASME Code specification RV geometrical model and the standard geometrical model.