Analysis of High-Enriched Core Composition Behavior in Micro Modular Reactor During Long-Cycle Operation

Kiho Park,Minhyeok Bang,Gyutaek Kang 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Recently, as carbon-neutral energy sources become increasingly important worldwide, SMRs (Small Modular Reactors), which offer significantly enhanced safety, versatility, and mobility compared to conventional nuclear reactors, are gaining attention as a viable alternative. SMR generally refers to small modular reactors with a power output of 300 MWe or less. Unlike conventional reactors, SMRs are characterized by an all-in-one design where peripheral systems and equipment are all integrated into the reactor itself, leading to enhanced reliability and durability. Additionally, the nuclear fuel reloading cycle is significantly extended compared to traditional reactors, resulting in a substantial reduction in maintenance difficulty and costs. Researchers have taken note of these characteristics of SMRs, particularly the extended fuel reloading cycle. Therefore, we have initiated the initial design of an ultra-small Micro Modular Reactor with an electricity generation capacity of 10 MWe and a fuel cycle of up to 55 years, with the goal of using it as a propulsion power source for various transportation modes, especially ships. Our design of MMR, called ‘ARA,’ is primarily distinguished by its use of U233 and Th232 fuels instead of conventional UO2 fuel. Due to various features of ‘ARA,’ including different fuel compositions, ARA is predicted to exhibit several characteristic features compared to conventional PWRs. In this study, among these characteristics, we focused on predicting changes in material composition within the fuel rod during the extended cycle operation of high-enriched fuel, rather than short-cycle operation using low-enriched fuel, unlike conventional reactors. The primary goal of this research is to observe the behavior of the composition of the materials used in the fuel cycle of the MMR, which utilizes U233 and Th232 fuels instead of UO2. Considering the difficulties in the spent nuclear fuel disposal process, many different trials were made to minimize the fission products of ARA, which differs from conventional reactors in terms of fuel type, size, and fuel cycle, in relation to waste generation.

Modular reactors: What can we learn from modular industrial plants and off site construction research

Wrigley Paul,Wood Paul,Robertson Daniel,Joannou Jason,O'Neill Sam,Hall Richard 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.1

New modular factory-built methodologies implemented in the construction and industrial plant industries may bring down costs for modular reactors. A factory-built environment brings about benefits such as; improved equipment, tools, quality, shift patterns, training, continuous improvement learning, environmental control, standardisation, parallel working, the use of commercial off shelf equipment and much of the commissioning can be completed before leaving the factory. All these benefits combine to reduce build schedules, increase certainty, reduce risk and make financing easier and cheaper.Currently, the construction and industrial chemical plant industries have implemented successful modular design and construction techniques. Therefore, the objectives of this paper are to understand and analyse the state of the art research in these industries through a systematic literature review. The research can then be assessed and applied to modular reactors.The literature review highlighted analysis methods that may prove to be useful. These include; modularisation decision tools, stakeholder analysis, schedule, supply chain, logistics, module design tools and construction site planning. Applicable research was highlighted for further work exploration for designers to assess, develop and efficiently design their modular reactors.

Natural circulation characteristics under various conditions on heavy liquid metal test loop

Ryu, Kyung Ha,Ban, Byoung Min,Lee, Tae Hyun,Lee, Jeonghyeon,Lee, Sang Huk,Cho, Jae Hyun,Ko, Sung-ho,Kim, Ji Hyun Elsevier 2018 International journal of thermal sciences Vol.132 No.-

<P><B>Abstract</B></P> <P>In advanced small modular reactors, a natural circulation system with liquid metal is preferred, as it offers enhanced safety features, simplicity of reactor design, and is economical with respect to construction. A natural circulation system also provides potential non-proliferation benefits to the international community. To test lead-bismuth eutectic as a liquid metal coolant, we have studied its natural circulation characteristics. We present the results of experiments on natural circulation conducted in a full-height scale test loop for varying core power, heat exchanger coolant oil temperature, and bubble injection rate. The experiments on the liquid metal were conducted under core power source conditions ranging from 2.5 kW to 15 kW. The aim of this experiment was to study natural circulation under various conditions. With our demonstration facility-based technology, we plan to verify small modular reactor cooling system safety and the technology of the bubble injection system that has been developed for liquid metal flow devices.</P> <P><B>Graphical abstract</B></P> <P>Liquid metal fast breeder reactors such as the sodium-cooled fast reactor and the lead-cooled fast reactor are candidates for GEN-IV nuclear energy systems. The advantages of the fast reactor design come from using liquid metal as the coolant. Small modular reactors are ideal for providing electricity to countries, offer a comparatively low initial capital investment, and offer flexibility for locations previously unable to accommodate nuclear reactors. A natural circulation system also provides potential non-proliferation benefits to the international community. The tests on liquid metal natural circulation were carried out on the liquid metal loop. Experimental studies on the isothermal natural circulation of the liquid metal were conducted in an integral test loop system, under steady state, and at varying core power source conditions ranging from 2.5 kW to 15 kW. The mass flow rate of the LBE increased rapidly from 0 to 0.36 kg/s over 500 s, and, as the core power increased, the mass flow rate of the LBE in the riser increased. As the oil temperature of the heat exchanger decreased, the temperature of the LBE also decreased. Because the temperature difference between the hot and cold legs was maintained, the mass flow rate was not affected. As the bubble injection rate was increased, the mass flow rate of the LBE in the riser also increased.</P> <P>[DISPLAY OMISSION]</P>

A Study on HSI Concept Design for Monitoring and Controlling Multi-Module Small Modular Reactors

Young Do Koo(구영도),Sa Kil Kim(김사길),Moon Won Song(송문원),Kwang Il Jeong(정광일),Joon Ku Lee(이준구) 대한인간공학회 2021 대한인간공학회 학술대회논문집 Vol.2021 No.11

Objective: The objective of the study is to elicit a basic concept for a new human-system interface (HSI) for integrated monitoring and controlling multi-module reactors, which is capable of minimizing any negative effects on the safety of the reactors or human performance. Background: Recently the researches on developing a new nuclear reactor system (i.e., small modular reactors (SMRs)) as well as improving the safety of the existing large-scale nuclear power plants (NPPs) are being carried out. In light water SMRs being developed, there are some characteristics in common, which are distinguished from the existing light water reactors: The safety of SMRs is secured through both advanced designs (e.g., passive safety systems, high level of automation, and so on) and proven technologies utilized also in the existing NPPs. Economy of SMRs due to less than 300 MWe production capacity is planning to be usually covered through multi-module SMR operation by one operator using an individual workstation in a single main control room, as well as a high level of automation technology. More works are accompanied because of more than one mission such as electricity generation, which is the conventional mission, and desalination or hydrogen production, which are new ones. According to these characteristics of SMRs, a new human-system interface (HSI) design being able to monitor and control integrated multi-module SMRs, differ from the existing HSI, is needed in common in SMRs. Specifically, in HSI, several essential capabilities are required: operator’s tasks for monitoring and controlling multiple reactors and access to information on reactors should be supported, and explanations for high levels of automation and alarms also have to be provided. Accordingly, a new HSI concept design proper to multi-module SMRs in view of users’ and regulatory requirements and considerations is necessary. Furthermore, competitiveness of SMR being developed in Republic of Korea can be strengthened by drawing a new HSI design. Method: Current HSI designs for a single reactor designed in accordance with standard design process (i.e., NUREG-0700 Rev.3) is expected to be constrained to monitor and control multi-module SMRs. Thus, a new HSI concept should be presented through addressing challengeable considerations or trying a novel approach. Functional requirements needed in providing plant status, alarm, and controls for multiple SMRs are considered from users’ or a regulatory point-of-view to draw a new HSI design concept, beyond addressing a single reactor only. In addition, HSIs in other multi-module SMRs or surrogate facilities are investigated. Results: New HSI concepts for monitoring and controlling multiple SMRs are proposed, and some of the design examples are drawn, which is distinguished for the existing HSI. Conclusion: As this study is a part of developing a new HSI design for multi-module SMRs, additional study will be sequentially performed based on the result drawn in the study. Application: The result of this study will be used as the input to a study for the basic design of the HSI to be available to multi-module reactors in the future.

Superheated Water-Cooled Small Modular Underwater Reactor Concept

Koroush Shirvan,Mujid Kazimi 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.6

A novel fully passive small modular superheated water reactor (SWR) for underwater deployment is designed to produce 160 MWe with steam at 500ºC to increase the thermodynamic efficiency compared with standard light water reactors. The SWR design is based on a conceptual 400-MWe integral SWR using the internally and externally cooled annular fuel (IXAF). The coolant boils in the external channels throughout the core to approximately the same quality as a conventional boiling water reactor and then the steam, instead of exiting the reactor pressure vessel, turns around and flows downward in the central channel of some IXAF fuel rods within each assembly and then flows upward through the rest of the IXAF pins in the assembly and exits the reactor pressure vessel as superheated steam. In this study, new cladding material to withstand high temperature steam in addition to the fuel mechanical and safety behavior is investigated. The steam temperature was found to depend on the thermal and mechanical characteristics of the fuel. The SWR showed a very different transient behavior compared with a boiling water reactor. The inter-play between the inner and outer channels of the IXAF was mainly beneficial except in the case of sudden reactivity insertion transients where additional control consideration is required.

INSTRUMENTATION AND CONTROL STRATEGIES FOR AN INTEGRAL PRESSURIZED WATER REACTOR

BELLE R. UPADHYAYA,MATTHEW R. LISH,J. WESLEY HINES,RYAN A. TARVER 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.2

Several vendors have recently been actively pursuing the development of integral pressurizedwater reactors (iPWRs) that range in power levels from small to large reactors. Integral reactors have the features of minimum vessel penetrations, passive heat removalafter reactor shutdown, and modular construction that allow fast plant integration and asecure fuel cycle. The features of an integral reactor limit the options for placing controland safety system instruments. The development of instrumentation and control (I&C)strategies for a large 1,000 MWe iPWR is described. Reactor system modelingdwhich includesreactor core dynamics, primary heat exchanger, and the steam flashing drumdis animportant part of I&C development and validation, and thereby consolidates the overallimplementation for a large iPWR. The results of simulation models, control development,and instrumentation features illustrate the systematic approach that is applicable to integrallight water reactors

Numerical Study on the Natural Circulation Characteristics in an Integral Type Marine Reactor for Inclined Conditions

Kim, Tae-Wan,Park, Goon-Cherl,Kim, Jae-Hak Korean Nuclear Society 2001 Nuclear Engineering and Technology Vol.33 No.4

A marine reactor shows very different thermal-hydraulic characteristics compared to a land- based reactor. Especially, study on the variation of flow field due to ship motions such as inclination, heaving and rolling is essential since the flow variation has great influence on the reactor cooling capability. In this study, the natural circulation characteristics of integral type marine reactor with modular steam generators were analyzed using computational fluid dynamics code, CFX-4, for inclined conditions. The numerical analyses are performed using the results of natural circulation experiments for integral reactor which are already conducted at Seoul National University. From the results, it was found that the flow rate in the ascending steam generator cassettes increases due to buoyancy effect. Due to this flow variation, temperature difference occurs at the outlets of the each steam generator cassettes. which is mitigated through downcomer by thermal mixing. Also, around the upper pressure header the flow from descending hot leg goes up to the ascending steam generator cassettes due to large natural circulation driving force in ascending steam generator cassettes. From this result, the increase of How rate in the ascending steam generator cassettes could be understood qualitatively.

Optimization of reactivity control in a small modular sodium-cooled fast reactor

Guo H.,Buiron L.,Sciora P.,Kooyman T. 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.7

The small modular sodium-cooled fast reactor (SMSFR) is an important component of Generation-IV reactors. The objective of this work is to improve the reactivity control in SMSFR by using innovative systems, including burnable poisons and optimized control rods. SMSFR with MOX fuel usually exhibits high burnup reactivity loss that leads to high excess reactivity and potential fuel melting in control rod withdrawal (CRW) accidents, which becomes an important constraint on the safety and economic efficiency of SMSFR. This work applies two types of burnable poisons in a SMSFR to reduce the excess reactivity. The first one homogenously loads minor actinides in the fuel. The second one combines absorber and moderators in specific assemblies. The influence of burnable poisons on the core characteristics is discussed and integrated into the analysis of CRW accidents. The results show that burnable poisons improve the safety performance of the core in a significant way. Burnable poisons also lessen the demand for the number, absorption ability, and insertion depth of control rods. Two optimized control rod designs with rare earth oxides (Eu2O3 and Gd2O3) and moderators are compared to the conventional design wi

Safeguards Distinction in Water-Cooled SMRs

Kwangho Ju,Seungho Jeong,Hosik Yoo 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Small modular reactors (SMRs) are getting attention as an alternative to fossil fuel power stations due to versatile application and carbon dioxide reduction. Although various types of advanced reactors are being developed, water-cooled SMR will be first deployed on a commercial scale. The International Atomic Energy Agency (IAEA) and regulatory bodies are trying to identify safeguards issues of water-cooled SMRs as the first priority. IAEA begins to develop a safeguards plan by asking for the facility’s specification in a given format, a design information questionnaire (DIQ). Then, IAEA periodically performs safeguards activities such as design information verification (DIV) and physical inventory verification (PIV). In this sense, we utilize research and power reactor DIQ for water-cooled SMRs (NuScale, SMART, i-SMR and KLT-40S). Most of the questions are answered with open information. For undisclosed answers, pressurized water reactor (PWR) features are described. Safeguards issues in water-cooled SMR originate from core modularization. As the nuclear material flows are diversified, the number of safeguards measure will be increased while staff are reduced in SMRs. Instrumentation for safeguards should be developed to reduce worker’s fatigue level. Intensive arrangement of fuel assemblies may also need unique devices to secure their visibility or detectability. A transparent floor with a surveillance system or advanced Cherenkov viewing device may be adopted to enhance containment and surveillance. Meanwhile, some questions could be more elaborate regarding safeguards. First, question #38 cannot confirm the time of occurrence of weapon-grade plutonium for reactor operation. Second, the answers in questions #46 and #49 are primitive to identify a place to generate an undeclared fissile material. Therefore, the current DIQ should be revised to get a detailed burnup report and spatial distribution of neutron flux.

An autonomous control framework for advanced reactors

Richard T. Wood,Belle R. Upadhyaya,Dan C. Floyd 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.5

Several Generation IV nuclear reactor concepts have goals for optimizing investment recovery throughphased introduction of multiple units on a common site with shared facilities and/or reconfigurableenergy conversion systems. Additionally, small modular reactors are suitable for remote deployment tosupport highly localized microgrids in isolated, underdeveloped regions. The long-term economicviability of these advanced reactor plants depends on significant reductions in plant operations andmaintenance costs. To accomplish these goals, intelligent control and diagnostic capabilities are neededto provide nearly autonomous operations with anticipatory maintenance. A nearly autonomous controlsystem should enable automatic operation of a nuclear power plant while adapting to equipment faultsand other upsets. It needs to have many intelligent capabilities, such as diagnosis, simulation, analysis,planning, reconfigurability, self-validation, and decision. These capabilities have been the subject ofresearch for many years, but an autonomous control system for nuclear power generation remains as-yetan unrealized goal. This article describes a functional framework for intelligent, autonomous control thatcan facilitate the integration of control, diagnostic, and decision-making capabilities to satisfy theoperational and performance goals of power plants based on multimodular advanced reactors.