Zhiwei Zhou

Burnup Analysis of Thorium-Uranium Based Molten Salt Blanket in a Fusion-Fission Hybrid Reactor

Abstract Progress on the fusion-fission hybrid reactor (FFHR) brings fusion a viable energy source in foreseeable future. Energy multiplication in a FFHR makes a much easier prerequisite for the fusion reaction than a fusion reactor. The molten salt reactor has advantages on heat transfer and post-processing of the spent fuels. A fission blanket made of molten salt was studied for the FFHR. The molten salt consists of F-Li-Be, with nuclear fuels dissolved in it. When thorium-uranium-plutonium fuels were added into a F-Li-Be molten salt zone with a component of 71% LiF -2% BeF2 -13.5% ThF4 -8.5% UF4 -5% PuF3, the appropriate blanket energy multiplication factor and TBR can be obtained. Two different molten salt models (Single molten salt zone model and multi molten salt zone model) were designed and compared in this study. The changes in blanket multiplication factor, M, and the tritium breeding ratio, TBR, during burnup life are investigated. The burnup analysis of the molten salt blanket was carried out by the COUPLE2 code. Through the burnup analysis, the breeding of the fissile fuel 233U and the transmutation of the minor actinides were also studied.

Neutronic Study of an Innovative Thorium-Uranium–Based Fusion-Fission Hybrid Energy Reactor with 233U Breeding Enhancement by Using Dual-Coolant System

Abstract In this technical note, an innovative thorium-uranium–fueled fusion-fission hybrid reactor (FFHR) design that employs a dual-coolant system to enhance 233U breeding and is based on a three-dimensional engineering model is presented. The reactor consists of two kinds of modules: a water-cooled, thermal spectrum power generation natural uranium–fueled module and helium-cooled, fast spectrum fissile-breeding natural thorium–fueled modules, which are arranged alternately in the poloidal direction of the blanket. An interesting and important neutronic characteristic of the FFHR is found in this technical note: Energy multiplication is primarily determined by the uranium module parameters and is almost independent of the thorium module parameter. Uranium module design should first consider improving energy production. The 232Th neutron capture rate is primarily determined by the thorium module parameters. The uranium module parameter has almost no influence on the 232Th neutron capture rate in the thorium module. The uranium and thorium modules have weak coupling in neutronic behavior. However, with the fixed design parameters of the uranium and thorium modules, the most important influencing factor on energy multiplication factor M (the ratio of total blanket energy output and the fusion energy) and the 233U breeding rate is the fraction of the external fusion neutron source irradiated on the uranium or thorium module or the blanket coverage rate of the uranium or thorium modules. Based on this characteristic, an innovative hybrid reactor design that employs a dual-coolant system is proposed in this technical note. Uranium modules still use water as the coolant to maintain a high energy multiplication factor, whereas helium is used as the coolant for the thorium module to obtain a fast neutron spectrum to enhance the 233U breeding. The simulation results show that the helium-cooled thorium module is 2.5 times more efficient in 233U breeding compared to the original water-cooled thorium module design. Approximately 10 tons of 233U is produced after 20 years of operation for the helium-cooled thorium module design.

Analysis of Density Wave Oscillations in Helically Coiled Tube Once-Through Steam Generator

Helically coiled tube Once-Through Steam Generator (H-OTSG) is one of the key equipment types for small modular reactors. The flow instability of the secondary side of the H-OTSG is particularly serious, because the working condition is in the range of low and medium pressure. This paper presents research on density wave oscillations (DWO) in a typical countercurrent H-OTSG. Based on the steady-state calculation, the mathematical model of single-channel system was established, and the transfer function was derived. Using Nyquist stability criterion of the single variable, the stability cases were studied with an in-house computer program. According to the analyses, the impact law of the geometrical parameters to the system stability was obtained. RELAP5/MOD3.2 code was also used to simulate DWO in H-OTSG. The theoretical analyses of the in-house program were compared to the simulation results of RELAP5. A correction factor was introduced to reduce the error of RELAP5 when modeling helical geometry. The comparison results agreed well which showed that the correction is effective.

Research on Nuclear Heat Deposition Behavior in the Spallation Target of an Accelerator Driven Subcritical System

The power density distribution behavior of the ADS spallation target, which is a key factor in the thermal-hydraulic and mechanical design of the high-power ADS target, was investigated under different proton incident energy. A Chinese ADS conceptual design of spallation target was proposed in this paper. The deposition heat in the spallation target was calculated by MCNPX code. From the results, it was found that the Bragg peak phenomenon weakens as the proton source incident energy increases. Large Bragg peak was observed for proton incident energy below 500MeV, however for the proton source energy above 900MeV, Bragg peak phenomena was not obvious. Analysis on the nuclear reactions behavior and ionization process induced by source proton in the target was carried out to address this issue. Meanwhile, the results show that the proton leakage rate from the target, which is an important factor in proton radiation shielding, greatly depends on the proton range (penetration depth) under different incident energy. In order to stop or keep the protons in the target, the minimum axial length (in the incoming particles direction) of the target at a given proton source incident energy should be determined according to the corresponding proton range. The results of this paper will be useful to guide the design of spallation target of a reference ADS.Copyright

The Sensitivity Analysis of Passive Containment Cooling System During Design Basis Accidents

Containment is the ultimate barrier which protects the radioactive substance from spreading to the atmosphere. Sensitivity analysis on AP1000 containment during postulated design basis accidents (DBAs) was studied by a dedicated analysis code PCCSAP-3D. The code was a three-dimensional thermal-hydraulic program developed to analyze the transient response of the containment during DBAs; and it was validated at a certain extent. Peak pressure and temperature were the most important phenomena during DBAs. The parameters being studied for sensitivity analysis were break source mass flow rate, containment free space, surface area and volume of heat structures, heat capacity of the containment shell, film coverage, cooling water tank mass flow rate and initial conditions. The results showed that break mass flow rate as well as containment free space had the most significant impact on the peak pressure and temperature during DBAs.Copyright

Thermal-Hydraulic Analysis of Concept Design of Spallation Target in Chinese Accelerator Driven Subcritical System

A concept design of spallation target in Chinese Accelerator Driven Subcritical System (ADS) was proposed in this paper. Spallation target is located in the center of an ADS, which produces neutron source for nuclear transmutation. The thermal-hydraulic demands for spallation target were proposed, and Lead-Bismuth Eutectic (LBE) was chosen as the spallation target and the coolant for the ADS. The deposition heat in the spallation target was calculated by MCNPX code, and the thermal-hydraulic behavior in the spallation target zone was calculated by CFD code FLUENT. The target can fulfill the design tasks under current design parameters. Different design parameters as well as different window shapes were studied to find their impacts to the temperature distribution and velocity distribution, and a proper design was proposed for future ADS with higher input energy.Copyright