TWO-Point Reactor Kinetics for Large D$_2$O Reflected Systems

노태완,오세기,김성년,김동훈,Noh, T.W.,Oh, S.K.,Kim, S.Y.,Kim, D.H. Korean Nuclear Society 1987 Nuclear Engineering and Technology Vol.19 No.3

다량의 중수반사체를 가진 조밀한 노심에서는 핵분열시 발생하는r선과 중수소와의 (r,n) 반응에 의해 지발 광중성자가 다량 생성되므로 이러한 계통을 기술하기 위하여 광중성자와 그 모핵종의 공간적 분리에 역점을 두어 2-점노 운동방정식을 정립하였다. 여러 반응도를 주입하여 출력 천이를 모사계산하므로써 노심과 반사체사이의 관련 효과를 조사하였다. 이 모델에 의한 모사계산 결과와 공간 종속 운동방정식에 의한 계산결과를 비교하였다. 반사체 영역에서의 광중성자 효과가 포함되므로써, 이를 포함하지 않은 모델에 비해 출력 천이현상을 감소시켰다. 실제로 출력을 측정하는 계측기는 이러한 공간적 분리영 향을 제거하기 위하여 노심 내부에 위치하여야 한다. Two-point kinetic equations for a compact-core-with-bulky-D$_2$O-reflector system were developed. A unique feature of the system is that certain fission gammas create retarded photoneutrons in the D$_2$O reflector by (r, n) reaction. Coupling effect between the core and the reflector was investigated by simulating power transients with various ramp reactivity insertions. Special attention was paid to the phenomenon associated with spatial separation of photoneutrons and their precursors. Simulations show that accuracy of the two-point model is comparable with that of space-dependent approach. Also it is found that the explicily expressed photoneutron terms in the reflector equation slow down the power transient compared to non-photoneutron expressions. Detectors for reactor power control purpose prefer to be deployed in the core zone to be able to accurately perdict transient power.

복사수송 계산의 위치변수 차분법

盧泰完 弘益大學校 科學技術硏究所 2002 科學技術硏究論文集 Vol.13 No.-

In this study, the discrete ordinates method which has been widely used in the solution of neutron transport phenomena is applied to the solution of radiative transfer equation. The self-adjoint form of the second order radiation intensty equation is used to enhance the stability of the solution, and a new linearization method is developed to avoid the nonlinearity in the material temperature equation. This new solution method is applied to the well known Marshak wave problem, and the numerical result is compared with that of the conventional Monte-Carlo method.

단순 우성 중성자 수송방정식을 이용한 노달 수송해법

노태완 한국방사성폐기물학회 2018 방사성폐기물학회지 Vol.16 No.2

Nodal transport methods are proposed for solving the simplified even-parity neutron transport (SEP) equation. These new methods are attributed to the success of existing nodal diffusion methods such as the Polynomial Expansion Nodal and the Analytic Function Expansion Nodal Methods, which are known to be very effective for solving the neutron diffusion equation. Numerical results show that the simplified even-parity transport equation is a valid approximation to the transport equation and that the two nodal methods developed in this study also work for the SEP transport equation, without conflict. Since accuracy of methods is easily increased by adding node unknowns, the proposed methods will be effective for coarse mesh calculation and this will also lead to computation efficiency. 중성자 확산방정식에 대해 개발된 노달 확산이론을 단순 우성 중성자 수송방정식에 적용할 수 있는 노달 수송이론을 제시한다. 노달이론으로 다항식전개 노달법과 해석함수전개 노달법을 채택하였고 단순 우성 수송방정식은 수송방정식에 대한 합리적 근사이며 기존의 노달해법이 방향 차분된 단순 우성 수송방정식에 정확히 적용될 수 있음을 수치적으로 확인하였다. 본 연구에서는 방법론 개발이 목적이므로 노드 당 최소한의 미지수를 정의하여 사용했지만 미지수를 추가함으로써 정확도를 증가시킬 수 있음은 기존의 노달 확산이론의 경우와 같다. 즉 중성자 수송방정식에 대해 노달이론을 적용하여 소격격자에 대해 계산 정확성이 확보되고 이는 결국 계산 효율성 증대로 나타난다.

다차원 2계 중성자 수송방정식의 방향근사를 위한 영역상수법

노태완 한국에너지학회 2007 에너지공학 Vol.16 No.1

- The piecewise constant angular approximation is developed to replace the conventional angular quadrature sets in the solution of the second-order, multi-dimensional SN neutron transport equations. The newly generated quadrature sets by this method substantially mitigate ray effects and can be used in the same manner as the conventional quadrature sets are used. The discrete-ordinates and the piecewise-constant approximations are applied to both the first-order Boltzmann and the second-order form of neutron transport equations in treating angular variables. The result is that the mitigation of ray effects is only achieved by the piecewise-constant method, in which new angular quadratures are generated by integrating angle variables over the specified region. In other sense, the newly generated angular quadratures turn out to decrease the contribution of mixed-derivative terms in the even-parity equation that is one of the second-order neutron transport equation. This result can be interpreted as the entire elimination or substantial mitigation of ray effect are possible in the simplified even-parity equation which has no mixed-derivative terms.

방향차분법을 적용한 시간종속 복사 열전달 계산

노태완 한국에너지학회 2006 에너지공학 Vol.15 No.4

원자력 분야에서 중성자 수송계산을 위해 개발되어 널리 사용되는 방향차분법을 시간 종속 복사 열전달식의 해를 구하는데 적용하였다. 광자의 방향별 밀도를 자체수반형 2계 편미분방정식으로 나타내어 해의 안정성을 높였고 매질의 온도방정식의 비선형성은 다단계 선형화법을 사용하여 근사하였다. 본 연구에서 개발된 해법을 전형적인 Marshak wave 문제에 적용하였고 계산 결과를 기존의 Monte Carlo의 계산결과와 비교하여 그 우월성을 보였다.

Numerical Calculation of λ-Mode of the Diffusion Equation

노태완,오세기,김성년,김창효,Noh, T.W.,Oh, S.K.,Kim, S.Y.,Kim, C.H. Korean Nuclear Society 1987 Nuclear Engineering and Technology Vol.19 No.4

중성자 확산 방정식의λ -mode를 구하는 반복 계산법을 정립하였고, 이 방법을 이용한 2군, 3차원 전산 코드 MOGEN을 개발하였다. 2차원 직각형 균질 원자로에 대해 계산을 수행하여, 생산된 고유치와 고유함수가 해석해에 잘 일치함을 보여 코드의 정확도를 검증하였다. 실제 CANDU형 포준 원자로의 2차원 mode를 생산하였고, 이는 기존의 mode특성을 정확히 나타내었다. 마지막으로, λ-mode의 응용분야에 대하여 간략히 설명하였다. A successive iteration method to calculate the λ-modes of the diffusion equation was developed. The 2-group, 3-dimensional computer code MOGEN was developed to implement this method, The accuracy of the method was demonstrated using 2-dimensional bare homogeneous rectangular reactor. The numerical solution shows good agreement with the analytic solution in terms of eigenvalue and eigenfunction As for the standard CANDU-600 reactor, the 2-dimensional modes were generated and these represent the conventional mode characteristics well. Finally, application of theλ-mode in reactor engineering problems is described briefly.

외국인력 유입이 중소제조업 내국인력의 임금에 미치는 영향

노태완,이찬영 한국지역경제학회 2023 韓國地域經濟硏究 Vol.21 No.3

This study analyzes the effect of the inflow of foreign manpower on the wage level of the domestic labor market. Considering the characteristics of foreign workers in Korea, data for 12 years from 2008 to 2019 were collected for small and medium-sized manufacturing industry and 16 city and provincial regional panel data were established to reflect regional characteristics. Finally, endogenous problems were considered through the Fixed Effect (FE) model and the Generalized Method of Moments (GM) model for companies with less than 100 employees. As a result of the analysis, there was a negative effect of the inflow of foreign manpower on the wages of domestic workers, but it was not statistically significant. On the other hand, the effects are differ in metropolitan(negative effect) area from non-metropolitan area(positive effect), However, numerically, the size was very small. In addition, it was found that the effect was somewhat overestimated without considering the endogeniety of foreign workers. These results somewhat dispel concerns about worsening working conditions in the non-metropolitan area and suggest the need to adjust the size of foreign manpower to meet local labor market conditions when considering future policies related to foreign manpower in the future.

수평배수재 진공압밀 지배방정식에 대한 수치해법 개발

盧泰完,金昌謙 弘益大學校 科學技術硏究所 2000 科學技術硏究論文集 Vol.11 No.-

We developed a numerical method for the problem of dissipating pore-water in hydraulic fills. The Dufort-Frankel's finite difference algorithms were applied to the problem with remodeled boundary conditions. The result showed that the horizontal drain with the vacuum consolidation is more efficient than self-weight or horizontal drain without vacuum in consolidating hydraulic fills.

중성자 수송방정식의 해의 양수성 해석

盧泰完 弘益大學校 科學技術硏究所 1998 科學技術硏究論文集 Vol.9 No.1

It is known that the first-order diamond-difference approximation is not guaranteed to yield positive solutions with given positive sources and cross sections, requiring negative-flux-fixups to correct this non-physical result. It is quite important for a solution method to have guaranteed positivity, since negative-flux-fixups demand additional computational work and sometimes can cause numerical instability when used with acceleration methods. Using the concept of S-matrix, we analyzed the positivity of a finite element solution scheme for the even-parity transport equation and a conventional 5-point finite difference scheme for the simplified even-parity transport equation. The result is that the even-parity transport equation does not have a guaranteed positivity, but the simplified even-parity equation has. Along with other characteristics this guaranteed positivity of the simplified even-parity transport equation enhances its usefulness despites of the mathematical weakness as an approximation to the transport equation.

A Study on Diffusion Approximations to Neutron Transport Boundary Conditions

노태완 한국방사성폐기물학회 2018 방사성폐기물학회지 Vol.16 No.2

To correctly predict the neutron behavior based on diffusion calculations, it is necessary to adopt well-specified boundary conditions using suitable diffusion approximations to transport boundary conditions. Boundary conditions such as the zero net-current, the Marshak, the Mark, the zero scalar flux, and the Albedo condition have been used extensively in diffusion theory to approximate the reflective and vacuum conditions in transport theory. In this paper, we derive and analyze these conditions to prove their mathematical validity and to understand their physical implications, as well as their relationships with one another. To show the validity of these diffusion boundary conditions, we solve a sample problem. The results show that solutions of the diffusion equation with these well-formulated boundary conditions are very close to the solution of the transport equation with transport boundary conditions.