• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.11a
• /
• pp.73-78
• /
• 1996

In this study, we proposed a fuzzy gain scheduler with intelligent learning algorithm for a reactor control. In the proposed algorithm, we used the gradient descent method to learn the rule bases of a fuzzy algorithm. These rule bases are learned toward minimizing an objective function, which is called a performance cost function. The objective of fuzzy gain scheduler with intelligent learning algorithm is the generation of adequate gains, which minimize the error of system. The condition of every plant is generally changed as time gose. That is, the initial gains obtained through the analysis of system are no longer suitable for the changed plant. And we need to set new gains, which minimize the error stemmed from changing the condition of a plant. In this paper, we applied this strategy for reactor control of nuclear power plant (NPP), and the results were compared with those of a simple PI controller, which has fixed gains. As a result, it was shown that the proposed algorithm was superior to the simple PI controller.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.607-612
• /
• 2005

Check valves playa vital role in the operation and protection of nuclear power plants. Check valves failure in nuclear power plants often lead to a plant transient or trip. An overview of the failure history of check valves needs to identify key area where resources can be best applied to further improve their reliability, and provide cost effective means for failure reduction. The analysis of historical failure data gives information on the populations of various types of check valves, the systems they are installed in, failure modes, effects, methods of detection, and the mechanisms of the failures. The results presented are based on information derived from operating records, nuclear industry reports, manufacturer supplied information. A majority of check valve failures are caused by improper application. Failure modes are identified for swing and lift check valves. Failures involving improper seating and valve disc stuck comprised the largest percentage of failures.

• Journal of Energy Engineering
• /
• v.24 no.2
• /
• pp.51-54
• /
• 2015

The mesoporous metal organic framework structure of Ni-BTC was successfully synthesized in a low temperature and short operation time via hydrothermal synthesis process. Such operational route virtuously consumed less electrical and thermal energy. It proved time saving along with acceptable product yield (38%). The product was characterized through FESEM, FT-IR, XRD and $N_2$ gas adsorption measurement. Hightemperature stability of synthesized MOF was gauged by diffraction indexing of XRD patterns of as synthesized and heat treated samples of MOFs. The mathematically calculated particle size of Ni-BTC was found to be 42nm.

• The Korean Journal of Nuclear Medicine
• /
• v.35 no.4
• /
• pp.213-223
• /
• 2001

Breast cancer accounts for the higher proportion of cancer related deaths among women, and the incidence of this malignant disease is still increasing. The commonly used screening method is mammography. However, mammography has the drawback of low specificity in differentiating malignant and benign breast diseases. To overcome this low specificity of mammography, scintimammography using various radiopharmaceuticals such as Thallium-201, Tc-99m MIBI, Tc-99m tetrofosmin and Tc-99m MDP was introduced and now actively under the investigation. Several studios have shown that high sensitivity and specificity in detection of primary breast cancer and axillary lymph node metastases using these radiopharmaceuticals. Scintimammography may play important roles in the diagnosis of primary breast cancer, evaluation of the patients with high risk, determining axillary lymph node metastasis, evaluation of the response to chemotherapy, determining the extent of disease, and surveillance of local recurrence. In the future, we should investigate the prognostic role of scintimammography after treatment of breast cancer patients and cost-effectiveness of scintimammography in the detection of primary breast cancer.

• Proceedings of the KIEE Conference
• /
• 2000.11c
• /
• pp.476-478
• /
• 2000

Objective is to design a high performance purification filter system of reactor coolant and seal injection system at nuclear power station. The purification filter systems play an important role in the stability of the nuclear and volume control system which consist the primary network systems of the nuclear power station. But the users of the purification filter systems frequently suffer from high maintenance cost which comes from lack of understanding of the system technology and domestic suppliers. It is time to establish a high performance domestic filter system manufacturing technology and optimum design for wide use in industrial applications.

• Nuclear Engineering and Technology
• /
• v.30 no.5
• /
• pp.444-451
• /
• 1998

The cost-effective reduction of occupational radiation exposure (ORE) dose at a nuclear power plant could not be achieved without going through an extensive analysis of accumulated ORE dose data of existing plants. It is necessary to identify what are high ORE jobs for ALARA implementation. In this study, the Rank Sum Method (RSM) is used in identifying high ORE jobs. As a case study, the database of ORE-related maintenance and repair jobs for Kori Units 3 and 4 is used for assessment, and top twenty high ORE jobs are identified. The results are also verified and validated using the Friedman test, and RSM is found to be a very efficient way of analyzing the data.

• Nuclear Engineering and Technology
• /
• v.45 no.5
• /
• pp.689-694
• /
• 2013

A duplex stainless steel sheet with 1 wt.% gadolinium was fabricated for a neutron absorbing material with high strength, excellent corrosion resistance, and low cost as well as high neutron absorption capability. The microstructure of the as-cast specimen has typical duplex phases including 31% ferrite and 69% austenite. Main alloy elements like chromium (Cr), nickel (Ni), and gadolinium (Gd) are relatively uniformly distributed in the matrix. Gadolinium rich precipitates were present in the grains and at the grain boundaries. The solution treatment at $1070^{\circ}$ for 50 minutes followed by the hot-rolling above $950^{\circ}$ after keeping the sheet at $1200^{\circ}$ for 1.5 hours are important points of the optimum condition to produce a 6 mm-thick plate without cracking.

• Nuclear Engineering and Technology
• /
• v.32 no.6
• /
• pp.537-548
• /
• 2000

The requirement of ultra high reliability of the safety critical software can not be demonstrated by testing alone. The specification based on formal method is recommended for safety system software. But there exist various kinds of formal methods, and this variety of formal method is recognized as an obstacle to the wide use of formal method. In this paper six different formal method have been applied to the same part of the functional requirements that is calculation algorithm intensive. The specification results were compared against the criteria that is derived from the characteristics that good software requirements specifications should have and regulatory body recommends to have. The application experience shows that the critical characteristics should be defined first, then appropriate method has to be selected. In our case, the Software Cost Reduction method was recommended for internal condition or calculation algorithm checking, and statechart method is recommended for the external behavioral description.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2003.11a
• /
• pp.59-65
• /
• 2003

In order to reduce the cost of software maintenance including software modification, we suggest the object oriented program with checking the version of application program using the Java language and the technique of executing the downloaded application program via network using the application manager. In order to change the traditional scheduler to the application manager we have adopted the Xlet concept in the nuclear fields using the network. In usual Xlet means a Java application that runs on the digital television receiver. The Java TV Application Program Interface(API) defines an application model called the Xlet application lifecycle. Java applications that use this lifecycle model are called Xlets. The Xlet application lifecycle is compatible with the existing application environment and virtual machine technology. The Xlet application lifecycle model defines the dialog(protocol) between an Xlet and its environment

• New & Renewable Energy
• /
• v.17 no.2
• /
• pp.1-8
• /
• 2021

We estimated the price range of electricity transactions under the prosumer system, considering the spread of renewable energy and the prospect of introducing a surplus power trading system between power consumers in Korea. The range (min/max) of power transaction prices was estimated by prosumers and consumers who could purchase electricity from utilities if needed. It is assumed that utilities purchased electricity from prosumers and consumers under a Time-of-Use (TOU) rate, trading at a monthly price. The range of available transaction prices according to the amount of power purchased from utilities and the amount of transaction power was also estimated. The price range that can be traded is expected to vary depending on variables such as the TOU rate, purchased and surplus power, levelized cost of electricity, etc.