Calculation of the Neutron Parameters for Accelerator-Driven Subcritical Reactors

In this paper, the accelerator-driven subcritical reactor (ADSR) is simulated based on structure of the TRIGA-Mark II reactor. A proton beam is accelerated and interacts on the lead target. Two cases of using lead are considered here: firstly, solid lead is referred to as spallation neutron target and water as the coolant; secondly, molten lead is considered both as a target and as a coolant. The proton beam in the energy range from 115 MeV to 2000 MeV interacts with the lead to create neutrons. The neutron parameters as neutron yield Yn/p, neutron multiplication factor k, the radial and axial distributions of the neutron flux in the core have been calculated by using MCNPX program. The results show that the neutron yield increases as the energies of the proton beam increases. When using the lead target, the differences between the neutron yield are from 4.2% to 14.2% depending on the energies of the proton beam. The proportion of uranium in the mixtures should be around 24% to produce an effective neutron multiplier factor greater than 0.9. The neutron fluxes are much higher than the same calculations for the TRIGA-Mark II reactor model using tungsten target and light water coolant.

Upgrade of electronics of neutron monitors DOMC and DOMB

DOMC and DOMB neutron monitors (NM) operate at the Concordia research station (Dome C on the Antarctic plateau, 75 o 06’S, 123 o 23’E, 3233 m a.s.l.) since 2015. Their high elevation and proximity to the geomagnetic pole provide low atmospheric and geomagnetic cutoffs and, therefore, the exceptionally high sensitivity to low-ener- gy cosmic rays. The instruments are the so-called mini neutron monitors with BF 3 -filled counter tubes. DOMC has the standard design with a lead neutron multiplier and DOMB is a so-called “bare” (lead-free) unit. We report on a recent upgrade of the electronics heads of these instruments. The new heads have a modular architecture, built upon a single-board computer Raspberry Pi. The upgrade increases the capabilities of the instruments in two aspects: (1) measurements, particularly, of cosmic ray multiplicity; (2) remote control and monitoring. The new electronic heads register each pulse from a detector, giving a timestamp with microsecond precision, which is crucial for multiplicity measurements. Many important parameters (e.g., high voltage, pulse detection thres- holds) can be controlled and adjusted remotely with the new design. High computing power allows performing data processing on the fly. The upgrade increases the capability of DOMC and DOMB in cosmic ray measurements and improves control of the operation of the neutron monitors.

Neutronic and Thermo-Hydraulic Analyses of Water-Cooled Blanket Based on Pressurized/Supercritical Water Conditions for CFETR

China Fusion Engineering Test Reactor (CFETR) is a test tokamak reactor being designed in China to bridge the gap between International Thermonuclear Experimental Reactor (ITER) and future fusion power plant. As one of the candidates, a water-cooled solid breeder blanket based on pressurized water and supercritical water conditions were proposed. In the concept, multiplying layers separated by three breeding layers were designed and optimized for higher tritium breeding ratio (TBR) and uniform heat distribution. This blanket adopts the Li2TiO3 lithium ceramic pebbles as the breeder, while beryllium pebbles as the neutron multiplier. In this paper, the thermal and fluid dynamic analyses of the optimized blanket on both water conditions were performed by numerical simulation, to discuss thermo-hydraulic performance of the blanket using pressurized water/supercritical water as its coolant. At first, the neutronic analysis was performed and based on the typical outboard equatorial blanket. Then, thermal and fluid dynamic analysis of the 3D model was carried out by CFX with fluid–solid coupling approach. It was found that the blanket can be effectively cooled on both water conditions, certified the feasibility of the blanket design with pressurized/supercritical water conditions. It indicated that supercritical water blanket had smaller safety margin than pressurized water blanket, but supercritical water blanket would lead to higher outlet temperature, thermal conductivity, and heat exchange efficiency also. In addition, the beryllium fraction was considered as one of the dominant factor, which leading a higher TBR in our simulations.

Design and simulation of a blanket module for TOKAMAK reactors

In this paper, we simulated an appropriate model for an advanced breeding blanket of future TOKAMAK fusion reactors with solid breeder (Li4SiO4) building material in the form of pebble beds, ODS ferritic steel as structural material and Beryllium as neutron multiplier. With the MCNPX code, the efficiency of this proposed model for the production and self-sufficiency of tritium was investigated. Total tritium breeding ratio of 1.15 is achieved. The helium-cooled pebble bed system and parameters of temperature and pressure are investigated by COMSOL multiphysics simulating software. The temperature of helium as cooling gas never exceeded 530[Formula: see text]C and the tolerable temperature of beryllium was obtained at 650[Formula: see text]C. In the proposed design, it is adequate to enrich the 6Li to 40%.

Conceptual Design of the Water Cooled Breeder Blanket for Both Phases of CFETR

The Chinese Fusion Engineering Testing Reactor (CFETR) will be operated in two phases. Phase I focuses on fusion power Pfusion = 200 MW, fusion power gain Qplasma = 1 – 5, tritium breeding ratio TBR>1.0, neutron DPA requirement ∼10 dpa. Phase II emphasizes DEMO validation, which means Qplasma > 10, Pfusion > 1 GW, e.g. 1.5 GW. It is required that one blanket design can cover the operation of both phases of CFETR from the viewpoint of saving construction cost and reducing waste inventory. However, fusion power in Phase-II is 4–6.5 times larger than those in Phase-I, and this also causes the great challenge facing the thermal-hydraulics design of the blanket. A new version of water cooled ceramic breeder (WCCB) blanket for both phases is proposed for CFETR, based on a trade-off considering on TBR, release tritium temperature in breeder zone, and removal heat capability of coolant. This design continues to employ the mixed breeder of Li2TiO3 and Be12Ti as tritium breeder and primary neutron multiplier, and a few Be as supplement of multiplying neutrons, Reduced Activation Ferritic/Martensitic steel as structural material, tungsten as plasma facing material. Pressurized water of 15.5 MPa is chosen as coolant with 285 °C inlet/325 °C outlet temperature. Main design change is that it employs two independent coolant systems in the blanket cooling components. For Phase I, one coolant system is only used and hoped to improve the breeder zone temperature higher than tritium release temperature. For Phase II, all of two coolant systems are put into using to ensure the material temperature less than the allowable limit. In this paper, the WCCB blanket design work is presented and its feasibility is investigated from the aspect of neutronics and thermo-hydraulics.

Thermo-Hydraulic Analysis of the Optimized Helium Cooled Solid Breeder Blanket for CFETR

China Fusion Engineering Test Reactor (CFETR) is under design recently, in which a conceptual structure of the helium-cooled solid breeder blanket is proposed as one of the candidate tritium breeding blankets. In this concept, three radial arranged U-shaped breeding zones are designed and optimized for higher Tritium Breeding Ratio (TBR) and structure simplification. This blanket uses the Li4SiO4 lithium ceramic pebbles as the breeder, while beryllium pebbles as the neutron multiplier. In this paper, the thermal and fluid dynamic analyses of the optimized typical outboard blanket module are performed by CFD method, where the nuclear heating rate is obtained from the preliminary neutronics calculations. The thermal hydraulic behaviors of the first wall (FW), the temperature distributions of submodule structure material, Li4SiO4 pebble bed and Beryllium pebble bed under normal and critical conditions are calculated, respectively. The results show that the temperature on the blanket module can be effectively cooled below allowable temperature limits of the materials, even if the FW is suffering the maximum surface heat flux, which verified the reasonability of the design of the blanket cooling scheme. In addition, several parametric sensitivity studies are conducted to investigate the influences of main parameters (e.g. coolant mass flow rate, inlet temperature, pebble bed thermal conductivity and fusion power) on the temperature distributions of the blanket components.