７２ Fusion Power

７２　Fusion Power【Space Travel】Dialogue with the Universe

７２－１　ITER( International Thermonuclear Experimental Reactor) [1]
・The goal is to build a fusion power plant in 2040-2050.
・The ITER experimental design has been changed to 2020, one year later than originally planned, under the influence of in eastern earthquake. Aim to start full-scale operation in 2027 as planned. The total project cost is 2 trillion yen.
・In addition, experimental reactor completion of the 2020 has become difficult.

【Reference】
・The name is derived from iter (: Net, Road).
・Seven countries and Region (Japan, China, EU, India, Russia, South Korea, USA)are involved in the this plan.
・ITER construction site is in Cadarache, France.

※Tokamak ：A tokamak is a device that uses a toroidal field (traveling around the torus in circles) and a poloidal field (traveling in circles orthogonal to the toroidal field). In a tokamak, the toroidal field is produced by electromagnets that surround the torus, and the poloidal field is the result of a toroidal electric current that flows inside the plasma. This current is induced inside the plasma with a second set of electromagnets. In this device, construction cost is cheap but plasma is unstable. [2]

７２－２　Nuclear Fusion Reaction [3]
○The most-researched candidate for producing controlled thermonuclear fusion power is D-T fusion reaction. (D: deuterium, T: tritium) 

○Deuterium is contained in large quantities in seawater.
○Tritium is breeded while irradiated with neutrons in lithium blanket surrounding the fusion reactor.


７２－３　Proton-proton chain reaction [4]
○The proton–proton chain reaction is one of the two (known) sets of fusion reactions by which stars convert hydrogen to helium. It dominates in stars the size of the Sun or smaller.
○Plasma(atomic nuclei and electrons become apart) is confined by gravity.

Individual reaction


Total

・ν is e-neutrino, γ is gamma ray.
・(1-1) occurs at a rate of99.75%( (1-2) :0.25%).

７２－４　Merit and Demerit
○Merit ： Nuclear fusion reaction is stopped automatically with a little adjustment mistake.
○Demerit：Radioactive waste of the same level as nuclear power plant.

７２－５　Cold Fusion　[5]
○The research is continuing.

７２－６　News
○The Wendelstein 7-X fusion device（W7-X）（Stellarator）at Max Planck Institute for Plasma Physics (IPP) in Greifswald produced its first hydrogen plasma on 3 February 2016. 
・Successive extensions are planned until, in about 4 years, discharges lasting 30 minutes.
The practical application of nuclear fusion is expected of around 2025. [6]

・Germany has forged ahead in funding the project, which in the past 20 years has cost €1.06bn.

※Stellarator [7]（Helical Device）：A stellarator is a device used to confine hot plasma with magnetic fields in order to sustain a controlled nuclear fusion reaction.
The name refers to the possibility of harnessing the power source of the sun, a stellar object.

※ The diameter of the W7-X is 10m. [7]

○A small, modular, efficient fusion plant (Tokamak)
New design could finally help to bring the long-sought power source closer to reality.
　August 10, 2015　 MIT News [8]

Illustration courtesy of the MIT ARC team [8]

【References】
1. ITER 
https://www.iter.org/
2. Wikipedia：Tokamak
3. Wikipedia：Fusion power
4. Wikipedia：Proton-proton chain reaction
5. Wikipedia：Cold Fusion
6. IPP:Max-Planck-Institut für Plasmaphysik
http://www.ipp.mpg.de/4010154/02_16
7. Wikipedia：Stellarator
8. MIT News
http://news.mit.edu/2015/small-modular-efficient-fusion-plant-0810