Vol. 12(16), pp. 194-198, 30 August, 2017 DOI: 10.5897/IJPS2017.4639 Article Number: 75DD9E465789 International Journal of Physical ISSN 1992 - 1950 Copyright ©2017 Sciences Author(s) retain the copyright of this article http://www.academicjournals.org/IJPS Full Length Research Paper Problems with p6Li plasma in a fusion reactor J. Bahmani*, B. Eslami and F. Mohammad Jafari Department of Physics, Payam Noor University, Tehran, Iran. Received 16 May, 2017; Accepted 27 July, 2017 Problems of using proton-Lithium-6 (p6Li) fuel are energy losses that occur in a fusion reactor. Investigating the energy balance equation in this fuel is significant. The p6Li reaction is termed aneutronic, as it produces relatively few neutrons and requires none for breeding. The energy from the charged reaction products can be directly converted to electrical power at a much higher efficiency than Deuterium-tritium (DT). In this paper, the approach of optimum performance of p6Li fuel in fusion reactors was presented investigating the energy balance equations for ions and electrons. The n optimum fuel mixture is almost p 3 . The performance was determined to be p6Li and is favorable for n 6 Li Ti=800 keV. Key words: Fuel, reactor, energy, radiation. INTRODUCTION Choice of suitable fuel for fusion reactors is subject to reproduction of tritium has more problem and it produces several conditions especially in terms of economic, safety a radial space resulting from blanket of lithium (Stott, and environmental parameters, while it is very difficult to 2005). The deuteron-deuteron (DD) fusion plasmas are satisfy all of them. Risks resulting from the release of very attractive since deuterium is abundant and it radioactive materials run as a result of activation of eliminates the need for breed tritium. The produced equipment and presence of tritium in the plasma system. neutrons are not a lot and they have less energy than DT Each fusion plasma Deuterium-tritium (DT) releases 17.6 plasma. However, there is atmospheric pollution due to MeV which turn into a kinetic energy with 3.5 MeV helium tritium production through DD fusion plasmas. D3He and 14.1 MeV neutron (Yu and Yu, 2009). plasma is called aneutronic which produces relatively few neutrons and nothing is needed for breeding. Energy 23D T 4 He(3.5 MeV) n(14.1MeV) resulted from the charged products (1) can directly change 1 1 2 (1) into the electric power in a much higher efficiency than DT. Thus, to do the same radioactivity as the DT, higher DT reaction has two major disadvantages: (1) It hurts the temperatures 50 to 100 keV are needed. In general, one reactor equipments due to the production of neutron, (2) of the most important alternatives in future fusion reactors *Corresponding author. E-mail: [email protected]. Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Bahmani et al 195 2D 2 D 3 He(0.82MeV) n 2.45 MeV (4) 1 1 2 (4) Since tritium does radioactive decay and neutron irradiation influences the reactor equipment, it is necessary to take some methods to limit the radioactivity caused by neutrons in order to prevent from releasing radioactive tritium. Another aneutronic fusion plasma is the plasma of proton with the lithium-6 (p6Li). This plasma: p6 Li 4 He(1.7MeV) 3 He(2.3MeV) (5) 32 2 (5) is proposed due to the little load of both components. Helium-3 would regress to plasma in the catalyzed mode and the plasma d3 ( ni Ti ) P ci +P si P Li P ie 0 (7) Figure 1. Cross -section as a function of energy for dt 2 (6) different plasmas (Momota et al., 1980). provides a very attractive net Q-value. This plasma is not ignitable in low temperatures and it has a very much energy losses in a fusion reactor. Therfore, the study of problems with p6Li plasma in a fusion reactor is significant. THE PROPERTIES OF P6LI PLASMA DT fusion reactors inherently encounter with economic and environmental challenges. Therefore, it is strongly emphasized to use a proper alternative among the advanced plasmas. In aneutronic fusion, instead of neutron, most of the energy is released through charged particles. In case of aneutronic plasmas such as D3He, the released tritium and the problems with radioactive wastes decreased. Neutron is produced indirectly through DD and DT side plasmas. D3He fusion reactor suffers from the following disadvantages: (1) Helium-3 is only available through the decay of tritium in proton bomb and also in the future space exploitation programs while just a few countries can afford it or it is produced in the fusion Figure 2. Average reactivity as a function of ion temperature 3 for different plasmas (Momota et al., 1980). of deuterium-tritium; (2) D He needs a higher temperature, a more beta and a better containment than 6 DT plasma. p Li fusion reaction is an aneutronic is D3He plasma. advanced fuel. Figures 1 and 2 show a cross-section in terms of energy and average reactivity versus ion 6 21D3 He 4 He(3.6MeV) H(14.7 MeV) temperature for different plasmas, (2) respectively. The p Li 12 2 1 (2) fusion plasma has advantages: (1) decreases neutron production; (2) no need for Lithium blanket requirement; However, the share of “cleanless” has not been done in 3 (3) reduces tritium inventory; (4) direct electrical D He completely due to production of neutrons and conversion; (5) optimum chain plasma features. tritium through the DD side fusion plasma with equal Unfortunately, it has disadvantages including: (1) high probability as follows: bremsstrahlung radiation; (2) produces indirect 7 11 2 2 3 1 radioactive Be and C; (3) utilizes condensable plasma D D T(1.01MeV) H(3.02 MeV) 6 (3) 1 1 1 1 (3) ( Li); and (4) high-temperature for ignition (Mily, 1981). 196 Int. J. Phys. Sci. ENERGY BALANCE IN P6LI PLASMA magnetic field in an inertial fusion reactor. The calculations show that the amount of T =800keV and It is necessary in the reactors that the input power be i are almost ideal conditions with considered sufficiently low when it is compared to the power output Te 300keV for production of a great net power. The study of the p6Li criteria. Fusion power per unit volume produced is: plasma is important in equilibrium state. The conditions is W different for "ideal ignition" and "ignition" cases. In "ideal P n n συ E 1.602.1019 n 2 συ E (11) f p6 fus 23e fus ignition" which are lower sets for the operating Li ( 3 ) cm (11) temperature in the plasma. In “ignition” mode is restricted; the pressure, energy confinement time, and n temperature for the plasma in stable mode under real where E is the released energy (in eV) and p . fus n condition. The mode of ignition is more practical in this 6 Li plasma. It is assumed without external power for P is equal with P . Investigations indicate that P is 6 f p6 Li f sustentation of the p Li plasma. Here, ion and electron 6 energy balance equations reviewed for this plasma. Ion maximized for p Li plasma by assuming 3 with energy balance equation as: and n= 1025 cm -3 . The results show that e P and P increase with high T and n . Figure 3a f B e e d3 display( ns T )the Pideal +P T P is P 800 0 keV . In this state , P is (7) (7) dt 2 ii ci sii Li ie B minimized. Figure 3b shows that the ideal fuel mixture is 3 . In this factors, P is more than P . Figure 4a where Pci is the amount of energy transferred from B f charged particles to ions per unit of time, P is the shows that PB reduces with low . Figure 4b indicates si P ie injected power, PLi is expended energy of each ion per that decreases with and low lnΛ P . f unit of time and Pie is the rate of energy losses by ions as the follow (Spitzer, 1940): The investigations show is also important in 3 2 2 28 Zi n i lnΛTmee i 0.3T W value. reduces with in low . P decreases in low Pie 7.61 10 n e 1 1 T i T e (8) B 3 m T m c23 cm i μT2 i e e ie (8) and it makes an enhancement in . Electron and ion temperature Te , Ti and the electron rest 2 energy mce are in eV , mi is the ion mass CONCLUSION ( mi μm i p , m p is the proton mass) and density n is in 6 -3 ne This study is showed that for the ignition of p Li fuel in a cm . The Coulomb logarithm is lnΛ 31 ln( ) Te fusion reactor, two important problems would emerge; the (Fundamenski and Garcia, 2007). Electron energy lossed energy and the need for high-temperature balance equation is: P electrons and ions. is obtained by the use of B . It P d3 f ( ne Te ) = P ce +P se +P ie -P Le -PBC -P =0 has been determined that the operation (9) is almost 800 d2t (9) keV. Coulomb logarithmic decreased to lnΛ5 and In comparison with Equation 8, bremsstrahlung and improved p6Li plasma performance. In this case, is cyclotron power are the different quantities. PB is more than . At high Te , radiation losses are very bremsstrahlung radiation power as follows (Nevins, 1998): much. Calculations show and increase with high and .