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   (Photo: Dr. Minjun J Choi and his article in Nature Communications) Dr. Minjun J Choi of the KSTAR Research Center of KFE has successfully proven the direct effects of plasma turbulence on magnetic islands. The findings, from a collaborative investigation involving researchers from Korea and the United States, were published in Nature Communications in January. “This research is the reverse of a previous study that revealed the effect of magnetic islands on the distribution and development of background turbulence. This time, we analyzed how background turbulence affects the evolution of magnetic islands. Based on this work, we expect to be able to weaken or redistribute the turbulence near magnetic islands, to prevent or alleviate plasma disruption," explained Dr. Choi, who was first author of the paper. A magnetic island is an island-like magnetic structure that is created in a plasma by a magnetic field reconnection, due to plasma instabilities. It can degrade tokamak performance by interfering with its magnetic confinement or can even cause plasma disruption. Understanding its effect and behavior has been one of the most difficult conundrums to solve in fusion research, and doing so is essential to realizing fusion energy. Several projects were being carried out on multiple fusion devices to address the problem. Dr. Choi focused his efforts on the interactions between magnetic islands and background plasma turbulence. The collaborative research team successfully proved by experiments on KSTAR that turbulence directly influenced magnetic islands to evolve by turbulence spreading or magnetic reconnection acceleration. Contributing researchers include Dr. Laszlo Bardoczi (General Atomics, US), Dr. George McKee (General Atomics, US), Professor T. S. Hahm (SNU, Korea), Professor Hyeon K. Park (UNIST, Korea), Professor Eisung Yoon (UNIST, Korea), and Professor Gunsu S. Yun (POSTECH, Korea). Multiple physics models have emerged to explain how plasma turbulence affects the evolution of magnetic islands, though few have been supported by actual experiments. Recent studies have suspected that turbulence spreading was suppressing the magnetic islands, but verifying it experimentally was difficult. The advanced diagnostics of KSTAR allowed the team to observe the turbulence as it spread from the outside of the magnetic islands to the inside. They were also able to witness turbulence enhancement at the reconnection site in the event of a fast collapse of a magnetic island. The findings provide a solid explanation of the main plasma phenomena necessary to realize fusion power. The researchers expect to contribute to future fusion reactor operations by advising how to suppress the magnetic islands causing plasma disruption. Related publication: Effects of plasma turbulence on the nonlinear evolution of magnetic island in tokamak
(Photo: The location of the diagnostics port plug inside ITER, where the diagnostics first wall is to be installed) A Korean company, Vitzro Tech, announced in December that it earned ITER's diagnostics first wall manufacturing contract. This contract is worth approximately 9.8 million euros. ITER will be equipped with a number of diagnostics to measure plasma temperature, density, radiation properties, etc. The diagnostics first wall will protect these devices inside the reactor from the super-hot plasma temperature, neutrons, and strong magnetic fields. Vitzro Tech also won another ITER contract in October 2018, the ITER IVC Busbar. The company’s accomplishments originate with its participation in Korean fusion research at ITER Korea and KSTAR, where it has been able to accumulate fusion know-how. It has participated in manufacturing the KSTAR Motor Generator and the NBI (Neutral Beam Injection) systems, which prepared it for such opportunities. Director-General of ITER Korea, Dr. Kijung Jung commented, "ITER is not only a crucial project for fusion energy research and development but also a huge opportunity for domestic industry to enter the global market to build the huge, state-of-the-art research facility. ITER Korea will do its best to support Korean companies with excellent fusion-related technologies to earn contracts from ITER and other partner countries."
Every January, KFE celebrates the authors of the most notable papers published the previous year with The Grand Paper Award, the Excellence Paper Award, and the Rookie Award. The Grand Paper Award goes to the author whose article recorded the highest SCI IF (Science Citation Index Impact Factor) and the Excellence Paper Award goes to the author of the second-highest article. The Rookie Award is for the young author with the highest IF among his or her peers who joined KFE within the last three years and earned their doctorate within the last five years. Here we have the three award winners with the most frequently cited papers of 2020. The Grand Paper Award / Senior Researcher Won-Seok Chang Senior Researcher Won-Seok Chang published a paper titled “A unified semi-global surface reaction model of polymer deposition and SiO2 etching in fluorocarbon plasma” in Applied Surface Science in 2020. It describes how silicon-based surfaces react to fluorocarbon plasma etching, based on modeling derived from measurements and diagnostics. It achieved the highest impact among all KFE papers released in 2020, by suggesting a realistic model of plasma surface reactions based on an analysis of reaction mechanisms with plasma diagnostics. The physical and chemical properties of plasma used in semiconductor processing are known to change depending on various factors, such as process gas, temperature, pressure, source, etc. This complexity, resulting from ions and radicals in the plasma, had to date been beyond the understanding of scientists and engineers, and semiconductor processing has been managed by hands-on experience. Chang’s research was a game-changer by providing a predictive model. He firstly conducted quantitative measurements of radical species that affect the deposition and ion incidence towards silicon oxide from plasma. Then he employed the results for modeling. He was able to attain more precise etching properties by analyzing the polymer layer produced by the etching and deposition of plasma particles. In particular, he included the property of the polymer layer as a factor, which researchers had always considered to be a mere byproduct of the etching process, and this significantly increased precision. Results from an industry-academia consortium The cutting-edge research, now attracting the interest of the semiconductor industry, was begun ten years ago. In 2009, a consortium of five institutions emerged to develop semiconductor process simulations: Jeonbuk National University, KW Tech, KRISS(Korea Research Institute of Standards and Science), Pusan National University, and KFE. When KFE started to develop plasma surface reaction modeling, Chang took charge of measuring and diagnosing plasma properties. The results laid the groundwork for the paper published in 2020. “In the beginning, I assumed my work would be over soon. However, plasma processing has kept getting more diverse, with semiconductor manufacturing evolving significantly. There is still a lot to know, and I want to know more than to stop.” He gave the consortium credit for his award. According to him, the semiconductor technology was developed because of contributions in three areas: industry experience, simulation technology, and analysis techniques. “Plasma is an original technology leading manufacturing competitiveness. Plasma research is empowered by collaboration and fusion between sectors. Industry and academia should work together to achieve results. Just as we did ten years ago, I hope for closer cooperation between industry and academia,” added Chang. The Excellence Paper Award / Doctor Jong Seok Song Dr. Jong-Seok Song has published work in Frontiers in Plant Science showing that plasma technology can help plants survive in stressful environments such as drought or against harmful microorganisms. The title of the article is ‘Emerging plasma technology that alleviates crop stress during the early growth stages of plants.’ "Seeds treated with plasma in gas or water gain the strength to survive stressful environments, as if it were vaccinated. Plasma can also sterilize microorganisms on the surface of seeds. In addition, it helps thick seeds to more easily germinate in extreme conditions such as drought by inflicting shock on their surface to absorb moisture," explained Dr. Song. The best part of this plasma technology is that it is environment-friendly. The agriculture industry has developed many chemical products to aid the sterilization and vitalization of seeds, but they have sometimes ended up threatening the environment and human health. In contrast, plasma technology only uses harmless air, water, and electricity to make fertilizer water. It can even degrade the chemical pesticides remaining in crops. Another reason his paper is worth attention is that it provides standard parameters for plasma treatment, such as the amount of electric power and exposure time. "Water, which is indispensable for plant growth, may also kill the plant if it is too abundant, by rotting the root. The same goes for plasma. Plasma treatment levels should differ depending on the type of crop, as they have different optimal growth conditions." Dr. Song made an effort to find the optimal conditions to enhance the seeds’ ability to sprout and thrive concerning seed sterilization and scarification. It also induces the plant to produce secondary metabolites, which are beneficial ingredients for people, by allowing it to develop a defense system against stressful environments. For example, plasma can enhance the level of ginsenoside in ginseng sprouts. To build a platform from cross-cutting research In 2016, Dr. Song attended an interdisciplinary symposium in university where he learned how plasma technology could lead to agricultural innovation. Then he joined the Plasma Bio Convergence division of Plasma Technology Institute in KFE, where researchers from various fields such as agriculture and life sciences, chemistry, and plasma science are conducting convergence projects outside of the box. "Other laboratories are also carrying out bio research using plasma technology. However, they only have limited access to conventional plasma devices that merely show beneficial effects based on manuals. On the other hand, here in KFE, we can customize our own plasma machines and develop processing techniques to find the best conditions," commented Dr. Song. Regarding his ultimate goal, he said: "My final goal is to build a platform, which is open for both academia and industry, by applying plasma technology to various crops, converging plasma technology and crop production, and databasing the research results." The Rookie Award – Doctor Jisung Kang In 2020 Dr. Jisung Kang published 'Role of fast-ion transport manipulating safety factor profile in KSTAR early diverting discharges' based on his 2018 KSTAR experiments. "Several pillars sustain the hot plasma shape like a doughnut. A safety factor can indicate whether one of these pillars is collapsing, causing plasma instability. From the KSTAR experiment data, I was able to learn that fast-ions significantly manipulate the safety factor," explained Dr. Kang. When fast-ion transport speeds up in unstable plasma, it affects the plasma safety factor. In this sense, fast-ions would seem to have a negative impact on fusion. However, according to him, it is not necessarily a bad thing. "Fusion plasma must reach the self-heating status, where the energy from the fusion reactions themselves can heat the plasma up without any assistance from an external heating device. Fast-ion research is crucial because if we can understand the impact of fast-ions on plasma, we can get a clue about how to get to the stable self-heating status." It is necessary to understand such a phenomenon in experimental devices like KSTAR, because DEMO reactors will produce much more fast-ions. The uniqueness of this research also lies in how it derives the safety factor. A safety factor profile needs to be based on multiple diagnostics, meaning it draws on all of the state-of-the-art technologies of KSTAR. That is why many researchers are paying attention to his work. "KSTAR's distinctive features helped me to draw a meaningful conclusion from experiments. Conventional fusion devices produce fast-ions only for a short period and have difficulty attaining continuous, steady-state data. KSTAR, in contrast, can carry out a stable operation with high-performance plasma thanks to its superconducting magnet, which enabled me to continuously observe and analyze them," Dr. Kang added. KSTAR's first plasma in 2008 ignited another dream in a young physicist's heart Dr. Kang's dream of fusion began ten years before he joined KFE. In 2008, KSTAR ignited its first plasma, a watershed in Korean fusion research history. And he was there, a young physicist visiting KFE to write his undergraduate thesis. KSTAR's first plasma started another fire in him to become a fusion researcher. Later in June of 2017, he became a researcher at KFE, where his job was to connect results from the Integrated Simulation division, the division he is in, with those from other divisions. "My research mission is roughly divided into three categories: firstly, as I have written in the paper, I am working on fast-ion physics. Secondly, I carry out simulations to build a future fusion reactor. Lastly, I am a sort of a translator between experimental data and the supercomputer, as we need to standardize KSTAR experiment data before the supercomputer can process and figure out certain physics phenomena," he commented. His research on fast-ions has been progressing since he began in 2018. His major interest is to solve the relations between plasma transport and fast-ions, which is one of the key challenges that need addressing to realize fusion power. He has focused on finding the associations between fast-ions and the fast frequency bands that happen in plasma instabilities. Now, he will take a step further, to draw a safety factor from relations between fast-ions and slow frequency bands.
KFE hosted the 24th International Plasma Conference on Plasma Surface Interactions in Controlled Fusion Devices(PSI-24) in January. In the original planning, the PSI-24 was supposed to be held in May of 2020. However, COVID-19 postponed it, to five days in January from the 25th to the 29th. The conference location also changed from Jeju in South Korea to an online webinar. 286 PSI experts from 22 countries participated in PSI-24 to address issues regarding divertor heat flux and lifetime. Participants exchanged recent results and technical information on fusion reactor divertor and inner walls, which will enable divertor-related technologies and contribute to future reactor manufacturing and operations.
The ITER Organization will host a 2-day Remote ITER Business Meeting presenting thecoming business opportunities, and the latest highlights of the Project on Wednesday 7 andThursday 8 April 2021.  In this virtual meeting, the ITER Organization presents the coming business opportunities. With six thematic sessions, experts from different areas give specific information about contracts and procurement needs in the next coming years. 1. Name of event: Remote ITER Business Meeting 2. Object: provide specific information about contracts and procurement needs in the next coming years 3. Date of event: 7-8 April 2021 4. Program  - Update of the ITER Project Status by Director General  - Procurement and Contract News  - Thematic sessions by ITER technical experts giving overview on coming business opportunities  - One-to-One meetings between interested companies and ITER experts  - Possibility to arrange Business-to-Business with other companies 5. Registration Period: 20 January - 6 April 2021 6. Linka:
Aiming to operate continuously high-temperature plasma over 100 million degrees for 300 seconds by 2025 temperature plasma for 20 seconds with an ion temperature exceeding 100 million degrees.   On November 24, the KSTAR Research Center at KFE announced that in joint research with Seoul National University (SNU) and Columbia University in the United States, it succeeded in the continuous operation of plasma for 20 seconds with an ion temperature higher than 100 million degrees, which is one of the core conditions of nuclear fusion in the 2020 KSTAR Plasma Campaign.   It is an achievement to extend the eight-second plasma operation time during the 2019 KSTAR Plasma Campaign by more than two times. In its 2018 experiment, KSTAR reached a plasma ion temperature of 100 million degrees for the first time (retention time: about 1.5 seconds).   Recreating the fusion reactions of the sun, given its ultra-high temperature and density, on earth requires heating and the maintenance of ion temperatures exceeding 100 million degrees after fueling a fusion device such as KSTAR and dividing nuclei into ions and electrons to create a plasma state.    Thus far, there have been other fusion devices that have briefly managed plasma at temperatures of 100 million degrees or higher. None of them broke the barrier of maintaining the operation for ten seconds or longer. This represented the operational limit of a normal conducting device,* and it was difficult to maintain a stable plasma state in the fusion device at such a high temperature for a long time. * Limits of a normal conduction device: Unlike KSTAR, a fusion device that features a superconducting magnet, existing fusion devices based on normal conducting magnets such as copper magnets cannot be operated for an extended period of time because when a high electric current runs through the magnet to create a magnetic field that is strong enough to confine plasma, the magnet overheats due to its resistance.   In its 2020 experiment, KSTAR improved the performance of the internal transport barrier (ITB) mode, one of the next-generation plasma operation modes developed in 2019 and succeeded in maintaining the plasma state for a long period of time, overcoming the existing limits of the ultra-high-temperature plasma operation.   Director Si-Woo Yoon of the KSTAR Research Center at the KFE explained, “The technologies required for long operations of 100 million-degree plasma are the key to the realization of fusion energy, and KSTAR’s success in maintaining high-temperature plasma for 20 seconds will be an important turning point in the race for securing the necessary technologies for long high-performance plasma operation, a critical component of a commercial nuclear fusion reactor in the future.”   “The success of the KSTAR experiment in the long high-temperature operation by overcoming certain drawbacks of the ITB modes brings us a step closer to the development of technologies leading to the realization of nuclear fusion energy,” added Yong-Su Na, a professor in the Department of Nuclear Engineering at SNU, who has been jointly conducting research on the KSTAR plasma operation.   KSTAR is going to share its key experiment outcomes in 2020, including this success, with fusion researchers around the world at the IAEA Fusion Energy Conference to be held in May of 2021.  The final goal of KSTAR is to succeed in continuous operation of 300 seconds with an ion temperature higher than 100 million degrees by 2025.
KFE’s Institute of Plasma Technology has paved the way for a paradigm shift in the storage and distribution of agricultural produce with their “Plasma-Technology-Based Smart Storage System.”   |Plasma storage system changes the storing function of humidity and temperature Organic Onion Regular Onion The “Plasma-Technology-Based Smart Storage System” has recorded excellent scores in germ and mycete tests prior to its deployment at farms. The picture on the left is of organic onions, while that on the right show regular onions. In each picture, only the onions on the left had plasma technology applied while stored for a month.  “Agriculture and ICT met to evolve into smart farms. Likewise, the crops grown on smart farms will meet with a smart storage system to accelerate agricultural innovation,” explained Dr. Seong-Bong Kim, the Director of the Division of Plasma-Bio Convergence. Plasma technology, which has already made substantial contributions to state-of-the-art industries such as the semi-conductor and medical industries, can change the paradigm of produce storage as well. The plasma storage system is a smart storage system that integrates three key elemental technologies (micro-organism sterilization, aging suppression, and respiration suppression) and the storage environment factors of the temperature and humidity for proper control. It is an eco-friendly technology to hinder the respiration and aging of farm products and to sterilize micro-organisms by plasma technology without the use of chemicals.    Existing low-temperature storage applications focus on minimizing the respiration of produce by lowering the temperature, as animals in hibernation do so as to sustain life. However, the typical temperature of a low-temperature storehouse was around 5℃, which caused cold damage to the stored products. During sizzling summers, electricity bills were another burden, with some storehouses even shutting down due to the high bills resulting from high electricity demand during heat wave periods.   “Until recently, key factors at a low-temperature storehouse were to control the temperature and humidity. However, controlling only these two factors led to limits with regard to the ability to restrict decomposition by micro-organisms, aging and respiration, as there are fungi and germs propagating even at low temperatures. Also, ethylene is not removed,” said Director Kim.   Hence, plasma storage systems are attracting more attention given their ability to control factors such as aging and respiration. The repression of aging and respiration is an original technology novel to existing storage systems. Being the most intricate technique, plasma catalyst hybrid technology was completed to adsorb ethylene selectively, which is the main substance causing the maturation of produce, and to remove it by means of plasma. In addition, a smart automatic control system was developed to enable customized, independent module control depending on the crop by modulizing each function of sterilization, aging suppression and respiration suppression.   |Aiming at operation recipe development based on demonstration data   “Korean fruits and vegetables are renowned overseas for their taste and quality. As the best condition differs from each product, we are planning to complete the optimal storage recipes which even take each product’s distribution stages into account through ceaseless demonstrations.” Director Kim expects that the completion of recipes tailored for each type of produce will ensure competitive quality for both domestic and export markets.   In addition, another dream of creating a new agricultural distribution system is being realized by transferring related technologies to local companies. The performance has already been proved for the plasma storage system with demonstration tests that began in 2019. Commercialization is planned to begin in earnest from 2021, when additional demonstrations and module, equipment and system tests are to be completed.   The MoU concluded on the 17th of July of 2020 among the Institute of Plasma Technology, and Jeollabuk-do Wanju-gun, and Jeonbuk Technopark was a milestone in relation to this plan. With the MoU, the three institutions will start joint research on plasma technology support and solutions, demonstrate and run a plasma-smart storage system in Wanju-gun, and cooperate closely in various fields such as smart agriculture policies and the organization of new projects. The Institute of Plasma Technology will extend trial projects nationwide based on Wanju-gun’s example after finishing the demonstrations.  The four plasma technology-based smart storage system testbeds located at the Institute of Plasma Technology, Gunsan
The KFE vision for core technology research and development for a nuclear fusion demonstration was shared.                   From the left, Professor Seung Jeong Noh(KFITA), Chief Commissioner Jeong-Won Lee (KFE Incorporation Commission), Dr. Gyung-Su Lee(Former president of NFRI), Congressman Sang-Min Lee, First Vice Minister Byung-Seon Jeong(MIST), President Suk Jae Yoo(KFE), Congressman Seung-Rae Jo, Congressman Yeung-Shik Kim, Acting Chairperson Sun-Hwa Hahn (NST), President Hyung-Shik Shin (KBSI)   KFE held a commencement ceremony on the 27th of December of 2020 to celebrate its new beginning as an independent research institution.   KFE began its research in January of 1996 as a project division of KBSI. After 20 years, in October of 2005, it was established as an affiliated research institute of KBSI, referred to as NFRI. Given the increasing need for a fusion-specialized research institution, an act in the Korean National Assembly was passed in April of 2020 to promote NFRI to KFE. Accordingly, KFE commenced as an independent institution on the 20th of November of 2020.    During the opening ceremony, only President Suk Jae Yoo and invited speakers attended in person according to the COVID19 quarantine policy. Attendants were the First Vice Minister Byung-Seon Jeong from MSIT; Congressman Sang-Min Lee of the Daejeon Yuseong District; Congressman Seung-Rae Jo and Congressman Yeung-Shik Kim from the Science, ICT, Broadcasting, and Communications Committee of the National Assembly; Acting Chairperson Sun-Hwa Hahn from the National Research Council of Science & Technology; Chief Commissioner Jeong-Won Lee of the KFE Incorporation Commission; President Hyung-Shik Shin of KBSI; Dr. Gyung-Su Lee who was the former president of NFRI; and Commissioner Seung Jeong Noh of KFITA. Others including KFE employees celebrated the opening through a YouTube live broadcast.    President Yoo commented through his opening speech, “We should be fully prepared for the vocation, for which what we do is not just mere research and development but will solve the energy problems of the future for good.” He also revealed the institutional vision “to shift the research focus from fundamental studies to core technologies for fusion energy demonstrations as well as to achieve innovations making use of the fourth industrial revolution to lay the foundation for a virtual fusion reactor.”   Vice Minister Jeong of MSIT added, “The hope of commercializing fusion energy was shown in a series of events from the completion of KSTAR in 2007 to the success of 2020 of the 20s operation at 100 million ℃. Twenty-five years have passed with the devotion of every scientist at KFE. Still, commercializing fusion energy to be delivered to us will take approximately another 35 years. There remains a path for us to go with a broader, further and longer perspective. Many say the carbon neutrality is achievable within the year 2050 if we realize our fusion plans. I would like to ask KFE to succeed in the demonstration so that fusion is more than just a possibility and will be the obvious alternative and to make an effort to communicate and unite with others despite beginning as an independent research institute.”
The 8th Korea-China JCM and the 16th Korea-Japan JCM were held via video conferences due to COVID19, respectively, on the 7th-8th of December and on the 10th-11th of December. Government officials and renowned scholars gathered to discuss national policies related to fusion R&D and collaborations using KSTAR and devices in each country as well as collaborations for ITER. In particular, at the KO-CN JCM, progress toward the HHLT ISO standard was shared, while the KO-JP JCM members discussed the impact of both countries’ de-carbonization policies on fusion R&D directions. Through the two JCMs, Korea recognized the importance of cooperation in area of fusion with China and Japan and agreed to implement remote collaborations proactively in 2021. With the end of the COVID-19 pandemic, the KO-CN JCM of 2021 will be held in China, while the KO-JP JCM will be held in Korea.
 - ITER Korea DA succeeded to manufacture the first product of a blank shield block The first product of the International Thermonuclear Experimental Reactor (ITER) "Blanket Shield Block" has been successfully manufactured in Korea. It is designed to protect nuclear fusion reactor devices from plasma whose neutrons and more than 100 million °C temperature can damage the parts. "The ITER Blanket Shield Block is a primary barrier to protect the ITER devices from plasma’s neutron damages and enormous energy set from ultra-high temperature over 100 million °C. Like a blanket, it protects all the main components such as vacuum vessel, magnet and so on" said Sa-Woong Kim, the team leader. In other words, it is the part to shield major ITER devices from plasma and neutrons from nuclear fusion, and is to be installed in puzzle-like connections, surrounding the inner wall of the vacuum vessel. Total 440 blanket shield blocks are going to be installed at ITER, procured by South Korea and China each to supply 220 units. This achievement is remarkable in that the team has successfully resolved technical issues which they have encountered in every stage, including design, manufacture and testing. They have successfully met the high standards required by ITER and have established mass production system for the blanket shield blocks. First product of ITER blanket shield block ITER Korea Project Blanket Technology Team members including Byung-Il Park(senior engineer), Sikun Chung (senior engineer), Hee-Jin Shim(principal researcher), Sa-Woong Kim(principal researcher, team leader), starting from left Mission 1. Finding the best material and design: Stainless Steel ITER put forward strict standards in selecting and manage the block materials. This was the first to meet for the production of blanket shield blocks. "Good quality is essential for shielding from neutrons and for cooling plasma. It must be a low-radiation material with a short half-life when exposed to neutrons. On top of that, drilling and welding must be made possible to serve as a part to prevent plasma heat," commented Hee-Jin Shim, the principal researcher of the team. Accordingly, the researchers first of all worked on developing a special stainless steel (i.e. 316L(N)-IG) for the blanket shield block to withstand extreme environments, which succeeded in satisfying all the strict criteria of ITER. Next, the design was completed in such a complex form considering, on the one hand, the shape of plasma inside, and on the other hand, all coils and pipes outside to tightly adjoin vacuum vessel. "We had to wait till finishing the design of ITER vacuum vessel to start designing blanket shield blocks in earnest. This is because we had to consider the blanket shield blocks’ location which is internally adjacent to plasma and externally to the vacuum vessel. The shape of blanket shield blocks was decided based on ITER’s idea of the most stable plasma form and by the location of coils and pipes inside the vacuum vessel,” said Dr. Kim. Mission 2. Carving ‘Stainless Steel 316L(N)-IG’ as elaborately as if it were made of clay In the production stage, a technique to delicately process difficult-to-machining materials of large size was developed to enable complicated shapes. "First of all, we introduced a precision drilling equipment to make a path of cooling water into the stainless steel 316L(N)-IG which weighed around 5 to 6 tons. And the cover plate was welded precisely by welding craftsmen. Then, we finished machining the external into complicated shapes by a large precision-machining-device which can move both horizontally, vertically and tilting as well" said Sikun Chung, a senior engineer of the team. It was a challenge of carving very huge, sturdy surface with a very fine knife. Drilling was another challenge to create a path for coolant. One shield block, whose size is 1m in height, 1.4m in width and 0.4m in thickness, requires as many as 220 drillings to create coolant passage. For the smooth flow of coolant, a hole of 1.4m length must be drilled through by one single drilling without mistake. If the way is drilled from both ends of the shield block towards the middle point, even a tiny miss of the point will lead to slow down the water flow on the spot, causing turbulence and drop in cooling performance. Therefore, it must penetrate 1.4 m with one single drilling, not to mention all the 220 coolant paths drilled inside a blanket shield block must meet each other accurately within 1mm tolerance. Senior engineer Byung-Il Park explained the difficulty of drilling as follows: "The 1.4 m should be drilled in one way within a 16-32mm diameter. Stainless chips from drilling may interfere with the way, and the drill may go astray due to the collision of power between the stainless steel and the drilling. We gathered initial mistakes and errors to come up with the best processing method. The ways in and out for coolant were finished by welding approximately 55 pieces of cover plate. Another trial and error was inevitable in welding as well to minimize distortion while welding total 160 meters.” In addition to the initial trials and lessons, the partnership with domestic companies also enabled engineers to find the best processing method. The blanket shield block passed a non-destructive test designed to fully inspect for all welds. By using the world's first developed ultra-high temperature helium leakage test facility, it also proved its performance by completing ITER-like operation test under high-temperature, high-vacuum conditions. Dr. Kim recalled that the various performance tests of the blanket shield block were like a series of endeavors trying to find something invisible. In particular, regarding the high temperature helium leakage test, the lack of both such a device and such experience demanded countries participating in ITER to gather for workshops to find a breakthrough together. It is notable that ITER Korea DA successfully passed the stringent testing standards of ITER for the first time among ITER members, with some of the technologies developed during the tests waiting for their patents to be approved.

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