South Korea’s domestic fusion research project, KSTAR, jumped its first major hurdle in 2008, when the Korean reactor achieved plasma that attained temperatures approaching those for the international ITER reactor, currently planned for Cadarache, France.
Now the researchers’ goals have shifted to perfect the plasma that they know they can generate, and extend the plasma generation for a longer period – from 389ms last year to 20s by 2012.
The 2008 discharge was also significant because it was the first-ever successful operation of a tokamak using Nb3Sn magnets, the same superconducting material that will be used for the ITER project.
So 2008’s engineering feat is expected to translate into big business for the supply chain. South Korea is one of the seven parties involved in ITER. After having spent $310 million in the period from 1996-2008, the Korean government is expected to award $280 million in private-sector contracts for ITER. In particular, this will include 20% of ITER superconductors ($71 million) and vacuum vessel and ports ($210 million). (Other ITER project members will take the remaining share of superconductor contracts: in addition to Korea’s 20%, Japan will get a 25% stake, Russia 20%, the EU 20%, China 7% and the USA 8%.)
KSTAR in detail
The construction of the Korea Superconducting Tokamak Advanced Research began in December 1995 and was completed on 14 September 2007. Altogether 39 organizations
participated in the project with South Korea’s National Fusion Research Institute acting as the central agency. The total investment in KSTAR was $309 million – $216.3m from the government, $50.4m from domestic nuclear energy R&D funds from Korea Hydro & Nuclear Power, and $42.3m from the private sector. The facility has yielded remarkable accomplishments, including local production of high technology superconductors, replacing $10 million worth of import. On the other hand, manufacturing difficulties in the superconducting magnets lead to delays – they took a total of 26 months in heat treatment.
The final commissioning of KSTAR began in February 2007. It was split into four phases.
Phase 1 involved testing the vacuum environment and the leak tightness of all vacuum systems. Testing was completed on 2 April 2008, when the pressure of the vacuum vessel and cryostat vessel measured less than the required 3.0×10-8mbar (3 microPascals).
For the second phase of commissioning, the system was cooled down to its operational temperature. KSTAR’s 9kW refrigeration system includes a compressor, chiller and distributor. The KSTAR magnets were cooled by the circulation of liquid helium (4.2K) for a month. All the superconducting magnets successfully reached 4.48K and maintained temperature for more than three months. The second phase of commissioning was completed on 2 May 2008.
The superconducting magnets or coils were tested during phase 3, which was completed on 6 June 2008. A toroidal field coil generates a torus-type magnetic field, which is required to hold the plasma within the vacuum vessel. All 16 TF coil currents were charged up to 15kA and maintained for eight hours without any faults. The poloidal field coil generates a large current in the plasma and controls the shape of the plasma. All 14 coils were tested for their synchronized operation.
Phase 4 involved the production of plasma with specified parameters and characteristics. Target parameters of 100kA plasma current for 100ms were chosen to achieve 107K of plasma temperature. This figure is the same criteria as ITER for the first plasma discharge. In general, the minimum required for power generation using deuterium-tritium fusion is 5×107-108K for more than 300s.
The first plasma that satisfied target parameters was generated on 13 June 2008 when a peak plasma current of 107kA was achieved during a 210ms pulse.
It is also important to note that an electron cyclotron heating system using an 84GHz gyrotron was deployed successfully to start up the plasma. With it, less than 2V of loop-voltage around the tokamak chamber was required for plasma start-up. The final phase of commissioning was completed at the end of June 2008.
KSTAR successfully achieved first plasma on 15 July 2008. The goal of the first plasma discharge test was to verify the operational capability in a new regime of plasma operation and to test whether the integration of the newly-built fusion device would be able to generate expected plasmas, even with limited ancillary systems. A plasma current of 133kA with pulse length of 389ms was generated in a 1.5T toroidal magnetic field, surpassing the original target parameters.
For the remaining three years of the first stage of KSTAR development, the team will concentrate on enhancing the performance of KSTAR. They will test the Ohmic, L and H operating modes of the tokamak with increasing plasma current, temperature and density. In particular, by 2012, D-type plasma in H-mode operation (the standard mode proposed for ITER) is to be achieved for at least 20 seconds. This will form the basis of long-time plasma operation.
The main goal of KSTAR development in its second stage, from 2013-2017, is to attain long-term plasma operation through various experiments of H-mode and hybrid mode operation. For the purpose of achieving this goal, non-inductive current drive, MHD instability control and long-term diverter operation technology are to be developed.
In the third stage, 2018-2022, the team will study high efficiency AT (advanced tokamak) operation techniques under relatively low heating power and magnetic field conditions. This will involve testing the real-time control of plasma current and pressure distribution, and intensive research activity to enhance plasma beta-value. In addition, research activities into ITER advanced operation mode, including steady-state mode are to be accomplished, and then plasma transport analysis under low-velocity situations similar to nuclear fusion reactor is also to be completed.
In the fourth and final stage from 2023-2025, the team will finalise a high-power heating device and a high-efficiency AT operation technique. To achieve this goal, bootstrap current distribution needs to be optimised, and long-term operation of the divertor under high thermal flux must be developed. In addition, KSTAR will be used to test the divertor and blanket under high power conditions so that they can be optimised before use in the DEMO reactor.
The KSTAR programme consists of four teams (about 80 people) including an experimental research division, a tokamak operation division, a tokamak engineering division and a plant engineering division. In addition, staff of national laboratories, university research centres and companies also participate in KSTAR projects.
ITER cooperation
Korea’s contribution to ITER
South Korea joined ITER in June 2003, 15 years after it was begun by the US, the EU, Japan and Russia. In April 2007 the South Korean National Assembly ratified the ITER Joint Implementation Agreement, which enables Korea to retain its original technologies.
Korea is supplying ten different components for the fusion reactor (see figure), a share of the ITER project funding, source technologies from KSTAR, as well as human resources and technical assistance.
The ITER project cost – estimated at EUR10 billion – is shared among all seven parties. The EU and Switzerland will contribute 45.46% of the total cost and the remainder will be split up in to six equal portions of 9.09% for the other members: Korea, Russia, the USA, Japan, China and India. South Korea is allocating its share, $1.6 billion, from government funds. The allocation comprises $870m for construction and $750m for operation and decommissioning. It is independent of KSTAR expenditure.
The manufacturers of the components for ITER will be those that supplied the parts for KSTAR (as shown in Table 2). Korea’s domestic ITER agency is responsible for the supply and delivery of South Korea’s contribution to ITER, and must ensure that all components meet quality requirements. It will also be responsible for the dispatch of domestic scientists and engineers to the ITER project in the construction and operation stages.
In addition, ITER Korea will develop source technologies to prepare for the commercialisation of the prospective DEMO reactor and establish a project management system for licensing and regulatory processes.
In 2009, South Korea is spending $58m on KSTAR and ITER cooperation.
Policy developments in Korea
To set up a legal framework for the development of original technologies in the field of fusion energy, the South Korean government introduced the National Fusion Energy Development Promotion Policy in December 2006 and the related decrees in March 2007, respectively. In August 2007, the government made it a rule to establish and renew a basic promotion plan for nuclear fusion energy development every five years.
The policy includes a comprehensive R&D programme for commercialisation of a Korean-made nuclear fusion reactor. It targets the period from 2007 to 2036 and it is divided into three stages, each with their own goals.
The goals of the first stage (2007-2011) are to establish the basis for promotion of nuclear fusion energy development. The goal of the second stage (2012~2021) is to become one of the five leading countries of nuclear fusion energy technology, with the US, Russia, Japan and the EU. During this period the government wishes to develop DEMO plant design technologies and industrialise nuclear fusion technologies, among other goals. In the third stage (2022-2036), the government expects to develop a robust capability for the construction of a nuclear fusion power plant.
Author Info:
Dr Young Ho Cho is a member of the Judging Committee and Technical Advisory Group of KINAC (Korea Institute of Nuclear Non-proliferation and Control) and KOSTI (Korea Strategic Trade Institute), organisations that are involved in screening South Korean items to be delivered from KSTAR to the ITER Organization. Young Ho Cho, Department of Radiological Science, Catholic University of Daegu, 330 Geumrak 1-ri, Hayang-eup, Gyeongsan-si, Gyeongbuk, Republic of Korea
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