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Slow Neutron Detectors
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
There are two natural isotopes of helium, namely 3He and 4He with natural abundances of 0.000137% and 99.999863%, respectively. The isotope 3He has a relatively large total thermal-neutron cross section of 5320 barns at 2200 m/s,3 of which the 3He(n,p)3H reaction constitutes 5316 barns. By contrast the thermal-neutron absorption cross section for 4He is essentially zero. The microscopic thermal-neutron absorption cross-section for 3He decreases with increasing neutron energy, with a dependence proportional to the inverse of the neutron speed (1/v) up to about 0.1 MeV, as shown in Fig. 17.1. For an incident neutron with negligible kinetic energy, the3He(n,p)3H reaction has the following energetics: 3He+n01→3H(0.191MeV)+1H(0.573MeV)withQ=0.764 MeV. The reaction products, while emitted isotropically, are emitted opposite to each other in order to preserve the almost zero incident momentum of the neutron.
Tritium Aging Effects on Fracture Toughness of Stainless Steel Weldments
Published in Fusion Science and Technology, 2020
Michael J. Morgan, Dale A. Hitchcock, Timothy M. Krentz, Scott L. West
Tritium handling and storage for fusion power and other applications requires large-scale tritium processing facilities that will be constructed from stainless steels because of their good compatibility with tritium. These steels are highly resistant to the embrittling effects of hydrogen isotopes and helium from tritium decay; however, they are not immune.1–5 Fracture toughness is reduced by exposure to tritium and the reduction increases with time as 3He builds into the material from tritium diffusion and radioactive decay.
Concept Design of the Tritium Plant on the TRINITI Site for the Tokamak Ignitor Project Tasks
Published in Fusion Science and Technology, 2020
M. Subbotin, M. Rozenkevich, A. Gostev, A. Bukin, V. Khripunov, V. Kochin, S. Marunich, Yu. Pak, A. Perevezentsev, G. Sharova
During the operation of the fusion reactor in the pulsed mode, part of the unreacted plasma must be continuously removed from the discharge chamber. A previous work estimated the composition of the gases regenerated at the temperature of the liquid nitrogen from the cryo-adsorption pumps of the JET reactor after working with the tritium plasma.6 It was shown that the regenerated gases mainly contain hydrogen isotopes, radiogenic helium, components of air (nitrogen, oxygen, and carbon oxides), and hydrocarbons.
Physical Properties and Effect of Helium-Vacancy Pair on Tungsten/Graphene Composite as Plasma-Facing Materials from First Principles
Published in Fusion Science and Technology, 2023
Yan Qizhen, Zhaochun Zhang, Guo Haibo, Wang Yang
Hydrogen isotopes and helium atoms in plasma irradiation will cause negative effects of bubble retention in tungsten, which damages the performance and stability of the material. To assess the effect of graphene on the radiation resistance of tungsten, we built the tungsten/graphene system containing the helium atom and vacancy. It should be noted that the tungsten/graphene model is doubled in the y-axis direction to minimize the influence of boundary effects.