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[en] Goals: – Develop the fundamental scientific basis to understand, predict, and measure changes in materials and systems, structures and components (SSCs) as they age in environments; – Apply this knowledge to develop and demonstrate methods and technologies that support safe and economical long-term operation of existing reactors; – Research new technologies that enhance plant performance, economics, and safety.
[en] The phenomenon and mechanism of FCI (Fuel Coolant Interaction) has been widely studied around the world in the past few decades. A series of experiments were performed and several FCI models were developed on the basis of these experiments. However, there are still large uncertainties in the models of FCI and limitations to predict FCI process, especially the reactor scale process. To study the mechanism of FCI, a new FCI experimental facility was designed and further experiments were performed by Shanghai Jiao Tong University, China. The photography of FCI process were obtained by 2 high-speed cameras recording from 2 different directions vertical to each other. Water level changed can also be got from images of FCI process. Pressure peak produced by intense interaction and temperature of coolant are recorded. To discuss the influence of different factors for FCI, numbers of variables are considered in these experiments, including jet material, melt temperature, coolant type, coolant subcooled temperature, release heights, break size and interaction pool size. This paper focuses on the FCI responses for different melt temperatures. Tin, with the melt point of 231.9 C. degrees, was chosen as the melt material since it is possible to acquire a large temperature range of melt from 400 to 1300 C. degrees. The phenomenon responses of FCI process and the particle size responses for different melt temperature are discussed in the paper. (authors)
[en] The multiple safety systems including high pressure safety injection (HPSI), low pressure safety injection (LPSI), safety injection tank (SIT), and etc. have been designed to protect the core under the accidents in NPPs. If the decay heat from reactor is not removed due to the failure of safety systems under the accidents, the core can be melted. Therefore, the monitoring of reactor internal phenomenon is very important to prevent core meltdown. The deep learning model can be simulated for reactor internal phenomena without knowledge of physical. Deep learning is one of the most active research fields in recent years because computer’s performance has been improved. It has been widely used not only in science but also in various industries such as medicine, advertising, and finance. Deep learning is a technology that applies information processing methods of human brain to machines. The basic structure of Deep learning has a multilayer perceptron (MLP) structure consisting of three or more hidden layers. The MLP is a neural network composed of several nodes and layers. The location of data is as follows: The thermal distribution of core cell, core baffle, bypass, support barrel, down comer, and vessel cylinder. The data was obtained by using MELCOR which is the severe accident analysis code. The operators can maintain the integrity of the reactor when an unexpected severe accident is occurred in the nuclear power plant because the developed model can predict the reactor internal phenomena by the thermal distribution of vessel cylinder.
[en] This publication results from a technical meeting on phenomenology and technologies relevant to in-vessel melt retention (IVMR) and ex-vessel corium cooling (EVCC). The purpose of the publication is to capture the state of knowledge, at the time of that meeting, related to phenomenology and technologies as well as the challenges and pending issues relevant to IVMR and EVCC for water cooled reactors by summarizing the information provided by the meeting participants in a form useful to practitioners in Member States.
[en] The Nuclear Engineering Department at Israel Electric Company has been engaged for a number of years in a joint research agreement with the Technion Nuclear Reactor Research Group on various thermal-hydraulic aspects of reactor design and safety. Besides developing their own analytical models, the researchers rely heavily on the RELAPS computer code in their analyses. The RELAPS series are general purpose, thermal-hydraulic system codes, used to simulate system response (such as the RCS) to transients and accidents. They are based on solving the equations of conservation of mass, energy and momentum within the system being modeled, where the model is a series of control volumes connected by junctions. The equations are solved simultaneously in each volume and junction using a finite difference numerical scheme. As an example, a recent report refers to containment response to a large LOCA in an AP600-like advanced rector. This work has been performed using RELAPS/Mod2. Accidents like LOCA represent design base events necessary to verify the adequacy of the emergency core cooling system, the passive containment system and other safety systems. The validation of simulation results is therefore important to the IEC staff responsible for monitoring the research. (author); 3 refs
[en] The Diverse Protection System (DPS) provides a diverse method to trip the reactor to satisfy the requirements related with Anticipated Transients Without Scram (ATWS) with a concurrence of the Common Cause Failures (CCF) in the safety I and C systems. All of the Optimized Power Reactor 1000 (OPR1000) and the APR1400 nuclear power plants have been designed with the DPS, which has the diverse reactor trip function and the initiation of diverse Auxiliary Feedwater Actuation Signals (AFAS) for the Engineered Safety Feature. Component Control System (ESF CCS) components. For the mitigation of ATWS caused by the CCF within the PPS and ESFCCS, and to overcome the diversity and defense in depth (D3) issues, various design changes have been made for new nuclear units to be built in Korea and abroad. This paper briefly describes recent design improvements and possible design changes of the DPS regarding the CCF and D3 issues