H. Arimoto

H." Sakagami

K. "Yamazaki

T. Oishi

Y. Sakawa

National Institute for Fusion Science (NIFS-Repository)

     Ion temperature measurement has been carried out by a ToF measurement of neutrons using multi channel fast plastic scintillator system, i.e., MANDALA, at ILL of Osaka University. In a fast ignition ICF experiment, a ToF measurement for neutrons was sometimes disturbed by intense gamma-rays because scintillator had residual luminescence caused by the gamma-rays. By use of a diamond radiation detector with a fast time response, there is a possibility to measure accurate ToF spectrum of neutrons. In this development, diamond single crystals for radiation detectors were synthesized, then diamond radiation detectors were adapted in ICF experiments at ILL. In this stage, obtaining of basic data required for developing real diamond ToF spectrometer for gamma-rays and neutrons was main objective.   This year, CVD diamond single crystals were grown in Hokkaido University by a micro-wave assisted plasma CVD device. A HP/HT type IIa diamond single crystal with off-axis (001) surface, 5×5 mm, was used as a substrate in this crystal growth. The lift-off method was adopted for reuse of the substrate.  Typical growth condition was as follows, substrate temperature: 850 ℃ , gas pressure: 110 Torr, methane concentration: 1 to 4 %, growth time: 48 hours. Strong free exaction recombination luminescence were observed in cathode luminescence (CL) spectra obtained with grown single diamond crystals. An aluminum Schtokky contact and a Ti/Au ohmic contact were fabricated on the crystal by evaporation technique.  Charge collection efficiency of one CVD diamond single crystal was 100 % for holes, 97 % for electrons. An example of response function for 213 nm UV pulsed laser is shown in figure 1; time width of the pulsed laser was approximately 100 ps.   To suppress RF noise to the diamond radiation detector, an isolated measurement port was used. The detector was settled at 10.2 cm from the target. The detector was connected with a digital oscilloscope, analog bandwidth: 600 MHz, with double shielded SMA cable. The detector and cable was covered by aluminum foil.   The neutron yield was approximately 1×107 n/shot. Gamma burst was estimated arrived at 137 ns from the trigger signal, however no obvious signal caused by neutron or gamma-rays was not observed. From this result, it was reviled that electrical isolated measurement port did not work well. Then the detector was isolated by polyethylene sheet in the measurement port. It succeeded to suppress RF noise shown in Figure 2. Complete RF noise reduction should be done in the next step. -2 -1 0 1 2 3-0.5-0.4-0.3-0.2-0.10.0ElectronsPulse Height (V)Time (ns)HolesFig. 1. Examples of time response for 213 nm pulsed laser obtained by a CVD diamond single crystal grown in Hokkaido Univ. Methane concentration was 4 %. 0 200 400 600 800 1000-50050Pulse Height (mV)Time (ns)Fig. 2. Examples of output signals from the diamond radiation detector at Gekiko XII laser shot. Nuclear fission and fusion reactors are expected as abundant electric power generation systems reducing human global warming greenhouse gas (GHG) emission amounts. Different from fossil-fuel thermal power plants, the fuel cost fraction of nuclear plants is small. However, fission reactors with foreign gaseous diffusion uranium enrichment system in Japan lead to rather high GHG emissions in comparison with those of domestic centrifuge enrichment system, because of the large electricity consumption in the gaseous diffusion system.  In order to search for economically and environmentally optimized reactor designs, the system analyses of fusion reactors on physics, engineering, cost and CO2 emission amounts have been carried out for toroidal magnetic confinement fusion (MCF) reactor designs, and some comparative studies among conventional electric power generation systems were carried out. Here, we extend this to the inertial confinement fusion (ICF) system, and include the effect of CO2 tax. Various blanket designs including fission-fusion (F-F) hybrid and D-3He reactor designs are assessed with respect to the cost of electricity (COE) and the life-cycle CO2 emission amounts. Recently, we had compared the CO2 emissions from the life-cycle of several fusion reactors1-5). The magnetic confinement systems evaluated here are the tokamak reactor (TR), helical reactor (HR), and spherical tokamak reactor (ST). These models are calculated by the Physics-Engineering-Cost (PEC) code. The inertial confinement fusion reactor (IR) is also evaluated, assuming its driver energy and driver efficiency. In addition, different blanket modules and fuels are considered in the TR designs. To calculate life-cycle CO2 emission from fusion reactors defined by plasma parameters and radial build, we used a basic unit for CO2 weights (kt-CO2/t-material).Figure 1 shows schematic models of various fusion reactor systems and their calculation results on COE and CO2 emission rate. Calculation results indicate that CO2 is emitted mainly in the construction stage of superconducting magnet systems for magnetic confinement fusion reactors. For the IR design, the driver system construction and pelletfabrication stages involve considerable CO2 emission. By comparing fusion reactors with other electric power generation systems in terms of CO2 emission, we confirmed that fusion reactors emit less CO2. Therefore, introducing a carbon tax has little effect on the economics of fusion reactors, and the cost of electricity (COE) from fusion reactors might be lower than that of oil-fired electric power plants when a carbon tax of around several hundred yen/t- CO2 is introduced. 1) K. Yamazaki, T. Oishi and K. Mori, Nucl. Fusion 51 (2011) 103004 2) K. Yamazaki and T. Oishi, Fusion Science and Technology 60 (2011)1109-1112 3) T. Oishi, K. Yamazaki, and Y. Hori, Fusion Science and Technology 60 (2011) 1113-1116 4) T. Oishi, K. Yamazaki, Y. Hori and H. Arimoto, Plasma and Fusion Research 6 (2011) 2401052 5) K. Mori, K. Yamazaki, T. Oishi, H. Arimoto and T. Shoji, Plasma and Fusion Research 6 (2011) 2405126  Tokamak Reactor㻌9.8 ¢/kWh㻌9.2 g-CO2/kWh㻌Spherical Torus10.4 ¢/kWh㻌9.1 g-CO2/kWh㻌Inertial Reactor10.7 ¢/kWh㻌12.9 g-CO2/kWhHelical Reactor11.1 ¢/kWh㻌9.9 g-CO2/kWh㻌Fig.1 Schematic drawing of reactor core models and their assessment results on COE and CO2 emission rate. 501§34. Comparative Assessment of Economics and CO2 Emissions in Inertial and Magnetic Fusion ReactorsYamazaki, K., Oishi, T., Arimoto, H. (Nagoya Univ.),  Sakawa, Y. (Osaka Univ.),  Sakagami, H.

Comparative Assessment of Economics and CO2 Emissions in Inertial and Magnetic Fusion Reactors

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Comparative Assessment of Economics and CO2 Emissions in Inertial and Magnetic Fusion Reactors

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