Výběr zpráv ze sítě NucNet - 11. týden 2006

Milestone For China’s Fusion Research Programme

17 March (NucNet): China’s fusion research programme has reached another milestone with scientists working on the China Tokamak HL-2A reactor confirming stable operation close to the design limits after major modifications since 2004.

The China National Nuclear Corporation (CNNC) said the reactor’s plasma electric current reached 400 kiloamperes and the plasma state lasted almost three seconds. Twelve reiterative stable discharge cycles were carried out one after each other. The highest temperature reached was 20 million degrees Celsius.

The HL-2A is China’s first tokamak with divertors – extra magnetic coils and target plates that remove impurities and fusion products from the plasma. The outer radius of the HL-2A torus – a doughnut-shaped vacuum chamber containing the plasma in a magnetic field – is 1.64 metres.

The HL-2A was built by CNNC’s Southwestern Institute of Physics (SWIP) on the outskirts of Chengdu, the capital of Sichuan province. Construction was based on the original ASDEX tokamak using its main components. The ASDEX (axially symmetric divertor experiment) was successfully operated during the 1980s by the Max Planck Institute of Plasma Physics at Garching near Munich. Operation of the HL-2A started in December 2002.

The SWIP is China’s largest research establishment for controlled nuclear fusion and plasma physics. Its HL-2A tokamak is used for research into divertor physics, auxiliary heating, advanced diagnostics and plasma heating.

China has listed controlled nuclear fusion in its national programme for science and technology development. At Hefei, capital of east China's Anhui province, the HT-7U tokamak fusion device is being commissioned by the Institute of Plasma Physics of the Chinese Academy of Sciences. This will be the first Chinese fusion experiment with superconducting magnets enabling discharge cycles lasting several minutes.

Since 2003, China has been a member of the International Thermonuclear Experimental Reactor (ITER) project with the EU, Russia, Japan, the US, South Korea and India. These countries will share the estimated 4.57 billion euro (5.56 billion US dollar) cost of constructing ITER, a tokamak experiment designed to show the scientific and technological feasibility of a full-scale fusion power reactor.

A fusion power reactor provides energy through the fusion of atomic nuclei. The fuel is a mix of the heavy hydrogen isotopes deuterium and tritium in the form of an ionised low-density gas, hydrogen plasma. The plasma is confined in magnetic fields and heated to temperatures exceeding 100 million degrees Celsius. At this temperature, deuterium and tritium nuclei collide with so much impact they merge into helium nuclei, releasing thermal energy. Fusion reactors with a torus or doughnut shaped confinement are called tokamaks.

JET, the Joint European Torus in Oxfordshire, England, is the largest nuclear fusion experimental reactor yet built. It has a radius of 2.96 metres, the plasma electric current is 3,200 to 4,800 kiloamperes, and the pulse length up to 60 seconds.

Zdroj: NucNet

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