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1FNC Technology Co., Ltd.; 2Korea Atomic Energy Research Institute
SMART (System-integrated Modular Advanced ReacTor) is an integral pressurized water reactor with passive safety systems to enhance the operational safety of the reactor. It has Passive Safety Injection System (PSIS) that injects borated water into Reactor Coolant System (RCS) to prevent core uncover in case of a loss of coolant accident (LOCA) without operator action or AC power and Passive Residual Heat Removal System (PRHRS) that removes the RCS heat by natural circulation via steam generators. Those designs have been investigated numerically and tested experimentally to ensure the intended performance in various conditions. Until now, MARS-KS has been mainly used to simulate the experiments to validate the phenomena related to hydraulic characteristics and transient behaviors and has been proved its prediction adequacy. It is important to note that the severe accident analysis should be conducted to support Level 2 Probabilistic Safety Assessment (PSA) and source term evaluation. Therefore, severe accident analysis tools should also be validated prior to be used. However, those have not been validated explicitly for SMART. In this study, MELCOR has been validated by comparing the transient simulation results of MARS-KS. Theoretical and numerical methods used in both codes are examined with respect to passive safety system performance. The accident sequences which are important in PSA are simulated and differences in major event timing and mass/energy release characteristics are investigated.
To compensate reactivity excess in nuclear reactors burnable absorbers such as gadolinium and erbium are used. Their daughter nuclides resulting from neutron absorption by erbium and gadolinium play no important role in terms of neutron-physical processes occurring in the reactor core. A burnable absorber, daughter nuclides of which would have a beneficial effect on fission chain reaction, is of a great interest.
The aim of the research is to study neutron-physical properties of new burnable absorber protactinium-231, and possibilities of its production in significant quantities.
It has been demonstrated that in contrast to conventional burnable absorbers based on gadolinium and erbium, proposed isotope of protactinium is more attractive because it allows us not only to compensate initial reactivity excess, but also to provide high fuel burn-up thanks to good multiplying properties of its daughter nuclides uranium-232 and uranium-233. Significant quantities of protactinium-231 could be produced in hybrid fusion-fission reactors, which are sources of neutrons (not sources of energy), and parameters of which have been already achieved at present time at experimental facilities in USA, Japan, and UK.
Sensitivity Analysis of Branching Flow of TES Integrated Nuclear Power Plant in the UAE Environment
Ju Yeon Lee1, Jai Oan Cho1, Jeong Ik Lee1, Ho Joon Yoon2
1Korea Advanced Institute of Science and Technology; 2Khalifa University of Science, Technology & Research (KUSTAR)
UAE government targets to expand the share of clean energy to 50% of total energy under ‘UAE Energy Strategy 2050’. Based on the policy the portion of renewable energy will dramatically increase in coming years. If the share of energy sources which have intermittency increases, the problem of maintaining grid stability can become a technical issue. Therefore, only flexible power generation sources will be able to compete in the UAE future power market. In the UAE, four units of APR1400 Korean model nuclear power plants are being built in Barakah site. In this study, thermal energy storage (TES) integrated nuclear power cycle is proposed as a flexible nuclear power plant which can play a key role in the future energy market. The steam cycle is first modeled and optimized by varying the seawater temperature in order to evaluate the efficiency of nuclear power plants constructed in the UAE. Second, the seawater temperature was fixed and the optimization process for the branch flow to the thermal energy storage (TES) system is performed.
Design, experiment and commissioning of the passive residual heat removal system of China’s three-generation nuclear power HuaLong No.1
Feng Li, Xiaohua Zhang, Na Yu, Zhifan Qui
Nuclear Power Institute of China
In response to a Station Black-Out accident similar to the Fukushima nuclear accident, China's three-generation nuclear power Hualong No. 1 designed and developed a passive residual heat removal system connected to the secondary side of the steam generator. Based on the two-phase natural circulation principle, the system is designed to bring out long-term core residual heat after an accident to ensure that the reactor is in a safe state. The steady state characteristic test and transient start and run test of the PRS system were carried out on the integrated experiment bench named ESPRIT. The experiment results show that the PRS system can establish natural circulation and discharge the residual heat of the first loop. China's Fuqing No. 5 nuclear power plant completed the installation of the PRS system in September 2019, and will carry out commissioning work in October. This debugging is the first real-world debugging of the new design. This paper introduces the design process of the PRS system debugging scheme.
Model Based Systems Engineering Environment for the Nuclear Safety Case
James Cornish, Steven Fletcher
Innovation in managing complex nuclear projects is required to deliver cost and risk reduction that ensures nuclear technologies remain competitive. Traditionally, multi-disciplinary teams have relied on a vast array of documents, spreadsheets, and databases to manage design and safety case information. While these tools are capable of holding large amounts of information, they represent a fundamental barrier to understanding the entirety of the design, especially as the design matures and complexity increases. This lack of insight inevitably results in a build-up of unanticipated shortfalls, often requiring downstream changes that necessitate schedule delays and increased costs; ultimately eroding investor confidence.
At the forefront of the potential solutions is the application of Model Based Systems Engineering (MBSE) methods which are being proven as highly effective in dealing with the technical and commercial complexity of modern systems. MBSE replaces the array of traditional tools with a single, visually programmed, relational database that presents “one version of the truth”.
This paper will explore how vital elements of a modern nuclear safety case can be represented in an MBSE environment using real world examples, recognisable to safety engineers. These include how:
1. A modern nuclear power plant’s systems, structures and components can be presented in an MBSE environment as the design evolves;
2. High-level safety principles, safety functions, and safety functional requirements can be represented in an MBSE environment;
3. Design changes are consistent with the category and class designations of systems, structure and components;
4. Operating rules can be modelled for different scenarios including normal and fault conditions;
5. Fault and engineering schedules can be auto-generated and easily accessed and maintained;
6. Complex physical modelling substantiation can be integrated into the MBSE environment.
The paper will conclude by summarising the significant risk reduction and savings that an MBSE safety case environment could deliver.