• 에너지공학
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• 제25권1호
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• pp.185-191
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• 2016

피동충수용 혼합형 안전주입탱크는 한국원자력연구원에서 제안한 원자력 피동안전계통의 한 종류로, 안전주입탱크의 상부와 가압기를 연결하여 모든 운전압력 조건에서 냉각수 주입이 가능하도록 개선한 시스템이다. 본 연구에서는 피동충수용 혼합형 안전주입탱크, 가압기와 원자력압력용기에 대한 압력 네트워크를 통해 피동충수용 혼합형 안전주입탱크와 가압기의 압력이 평형이 되는 조건을 이론적으로 도출하였으며, 개별효과시험장치를 이용하여 안전주입탱크에서 발생하는 다양한 열수력 현상(증기응축 및 열혼합 현상)들을 파악하였다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.500-510
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• 1996

A Direct injection -mixing total -flow -control sprayer was developed and evaluated . The system provided precise application rates and minimized operator exposure to chemicals as well as providing a possibility for recycling container so f unused chemicals that can causes environmental contamination. Chemicals were metered and injected proportionally to the diluent flow rate to provide constant concentrations. The main diluent flow was varied in response to changes in travel speed. Experimental variables of the sprayer were the control interval, the sensitivity of flow regulating valve, the tolerance of control object and the sensitivity of the injection pump system. The optimal performance of the flow control system was with an average response time of 8.5 sec at an absolute steady state of error of 0.067 L/min (0.8% of flow rate). The average response time of the injection rate was -0.53 sec and the coefficient of variation (CV) of concentration was 3.2%.

• Nuclear Engineering and Technology
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• 제45권2호
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• pp.237-248
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• 2013

Thermal stratification has continuously caused several piping failures in nuclear power plants since the early 1980s. However, this critical thermal effect was not considered when the old nuclear power plants were designed. Therefore, it is urgent to evaluate this unexpected thermal effect on the structural integrity of piping systems. In this paper, the thermal effects of stratified flow in two different safety injection piping systems were investigated by using a coupled CFD-FE method. Since stratified flow is generally generated by turbulent penetration and/or valve leakage, thermal stress analyses as well as CFD analyses were carried out considering these two primary causes. Numerical results show that the most critical factor governing thermal stratification is valve leakage and that temperature distribution significantly changes according to the leakage path. In particular, in-leakage has a high possibility of causing considerable structural problems in RCS piping.

• 대한임베디드공학회논문지
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• 제16권4호
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• pp.129-136
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• 2021

River facilities and port structures require a regular inspection and diagnosis due to obsolescence. Currently, most river facilities are undergoing indirect inspection and diagnosis by divers. The underwater inspections are not feasible due to safety issues of divers and restrictions on working hours and environment. To overcome these issues, it is intended to conduct inspections of river facilities using underwater drones. In this research, an underwater ROV (Remote Operated Vehicle) has been developed, which is a kind of drone with propellers. As a key device of this research, an injection device has been attached to the underwater drone to conduct an operation test, a stable operation test of an underwater drone, and a test of attached sensors. The river facility inspection can be carried out optimally using the hovering control of the drone and injection systems. With the developed ROV system, hovering test and injection test have been performed to verify the feasibility of this development.

• 한국안전학회지
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• 제37권5호
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• pp.80-88
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• 2022

The Korean nuclear industry had developed the SPACE (Safety and Performance Analysis Code for nuclear power plants) code, which adopts a two-fluid, three-field model that is comprised of gas, continuous liquid and droplet fields and has the capability to simulate three-dimensional models. According to the revised law by the Nuclear Safety and Security Commission (NSSC) in Korea, the multiple failure accidents that must be considered for the accident management plan of a nuclear power plant was determined based on the lessons learned from the Fukushima accident. Generally, to improve the reliability of the calculation results of a safety analysis code, verification is required for the separate and integral effect experiments. Therefore, the goal of this work is to verify the calculation capability of the SPACE code for multiple failure accidents. For this purpose, an experiment was conducted to simulate a Control Element Drive Mechanism (CEDM) break with a safety injection failure using the ATLAS test facility, which is operated by Korea Atomic Energy Research Institute (KAERI). This experiment focused on the comparison between the experiment results and code calculation results to verify the performance of the SPACE code. The results of the overall system transient response using the SPACE code showed similar trends with the experimental results for parameters such as the system pressure, mass flow rate, and collapsed water level in component. In conclusion, it can be concluded that the SPACE code has sufficient capability to simulate a CEDM break with a safety injection failure accident.

• Nuclear Engineering and Technology
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• 제47권2호
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• pp.157-164
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• 2015

Nuclear power plants have logical loop structures in their system configuration. This paper explains the method to solve a loop structure in reliability analysis. As examples of loop structured systems, the reactor core isolation cooling system and high-pressure core injection system of a boiling water reactor are considered and analyzed under a station blackout accident condition. The analysis results show the important role of loop structures under severe accidents. For the evaluation of the safety of nuclear power plants, it is necessary to accurately evaluate a loop structure's reliability.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2001년도 춘계학술대회
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• pp.173-178
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• 2001

This paper studies the structure and reliability of homogeneous s-coherent multistate system. We describe efficiency of inclusion-exclusion algorithm and pivotal decomposition algorithm for reliability calculation of 2-states system which developed in (Lee 1999) ［10］. We extend our method, applied in ［10］, to the case when components of the system are given multi-states. As an application, the high pressure injection system of a pressurized water reactor is modeled as a multistate system composed of homogeneous s-coherent multistate subsystems. And Several examples are illustrated.

• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1206-1215
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• 2005

The thermal stratification phenomena, frequently occurring in the component of nuclear power plant system such as pressurizer surge line, steam generator inlet nozzle, safety injection system (SIS), and chemical and volume control system (CVCS), can cause through-wall cracks, thermal fatigue, unexpected piping displacement and dislocation, and pipe support damage. The phenomenon is one of the unaccounted load in the design stage. However, the load have been found to be serious as nuclear power plant operation experience accumulates. In particular, the thermal stratification by the turbulent penetration or valve leak in the SIS and SCS pipe line can lead these safety systems to failure by the thermal fatigue. Therefore in this study an 1/10 scaledowned experimental rig had been designed and installed. And a series of experimental works had been executed to measure the temperature distribution (thermal stratification) in these systems by the turbulent penetration, valve leak, and heat transfer through valve. The results provide very valuable informations such as turbulent penetration depth, the possibility of thermal stratification by the heat transfer through valve, etc. Also the results are expected to be useful to understand the thermal stratification in these systems, establish the thermal strati­fication criteria and validate the calculation results by CFD Codes such as Fluent, Phenix, CFX.

• 터널과지하공간
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• 제23권6호
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• pp.572-580
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• 2013

이 사례연구에서는 스위스 바젤에서 진행되었던 인공지열발전(EGS) 프로젝트인 Deep Heat Mining Basel(DHMB)의 미소진동 관리시스템을 살펴보았다. 인공지열발전 프로젝트에 꼭 필요한 인공지열저류층 생성을 위한 수리자극으로 인해 발생하는 유도진동은 안전관리시스템을 수립하여 수리자극의 압력과 유량을 관리하여야 한다. DHMB프로젝트에서는 수리자극 기간 동안 지속적인 관측활동을 통해 미소진동 발생 진도에 따라 단계별로 대응하는 경보시스템과 커뮤니케이션 대응 절차가 사전에 수립되어 관리되었다. 그러나 수리자극을 위한 주입 완료 후에도 지열저류층에서 발생한 주입이후 진동현상으로 인해 예상보다 큰 지진이 발생하자 프로젝트가 중단되었다. 사후분석 결과 실시간 경보시스템은 주입이후 진동 현상을 감안한 새로운 미소진동 안전관리시스템을 수립하는 것이 필요하다고 확인되었다.

• 한국안전학회지
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• 제19권1호
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• pp.1-5
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• 2004

In the present study, the gas injection system based on air-water model was designed to investigate the flow characteristics of liquid phase. A PIV system was applied to analyze the flow pattern in a ladle which gas stated to rise upward from the bottom. Gas flow is one of most important factors which could feature a flow pattern in a gas injection system. As the gas injected into the liquid, the kinetic energy of bubble transfer to liquid phase and a strong circulation flow develops in the liquid phase. Such a flow in the liquid develops vortex and improve the mixing process. Due to the centrifugal force, circulation flow was well developed near both wall sides and upper region respectively. Increasing gas flow was helpful to remove dead zone but, weak flow zone still exists in spite of the increasement of gas flow rate.