Xiang M. Chen

Bio: Xiang M. Chen is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: FLiBe & Inertial confinement fusion. The author has an hindex of 5, co-authored 8 publications receiving 63 citations.

The Soft-Sphere Equation of State for Liquid Flibe

Abstract: Molten Flibe (Li2BeF4) salt is a candidate material for the liquid blanket in the HYLIFE-II inertial confinement fusion reactor. The thermodynamic properties of the liquid are very important for the study of the thermohydraulic behavior of the concept design, particularly, the compressible analysis of the blanket isochoric heating problem. In this paper, a soft sphere model equation of state, which was used for describing liquid metals previously, is deployed with slight modifications for fitting the available experimental data for liquid Flibe. It is found that within the available temperature range the model gives a good agreement with experimental data for density, enthalpy and speed of sound. Additionally the model provides reasonable isotherms, spinodal line and predicts a “critical point”. The results show that the model has good thermodynamic behavior, although for a material like Flibe the “critical point” phenomenon is more complex than for pure component material.

Gas Dynamics in the Central Cavity of the HYLIFE-II Reactortitle

Abstract: In a HYLIFE-II ICF reactor, the microfusion of the D-T capsule in the center of the chamber produces X-rays that can ablate a thin layer off the liquid blanket which protects the first structural wall Thisablated material will implode toward the center line of the central cavity due to the initial vacuum and cylindrical geometry, and then rebound back to the liquid blanket vent through it and exert a pressure impulse'' onto the structural wall. The initial ablation occurs in a very short period with very small characteristic length and the implosion and rebounding processes feature very high pressures and temperatures. The proper design of the chamber relies on the reasonably accurate analysis of the gas dynamics in the central cavity and the gas-liquid interaction. In this paper, a second order Godunov numerical method is used to solve the compressible flow equations in the central cavity. The rarefaction and shock phenomena are very well captured by the numerical calculation. The equation of state for Flibe vapor is used in the calculation along with the parameters for the HYLIFE-II design. Since the radiation transport has not yet been included in the current calculations, the vapor possesses higher energy and therefore temperature.more » The total mass vaporized will also be underestimated in the later time of the calculation. The incorporation of a radiation calculation into this code is our next goal.« less

Fitted equations of state for Flibe gas

Abstract: HYLIFE-II reactor uses molten salt Flibe as the liquid blanket material. The property of its gaseous state was poorly known for gas dynamics calculations and other design problems. This study presents two fitted equations of state of the Flibe gas to meet the needs. The fitted range covers both dissociation and ionization regions. The methods used for fitting allow good agreement between the calculated data and fitted equations.

The pressure relaxation of liquid jets after isochoric heating

Abstract: During isochoric heating by fast neutron irradiation, a high pressure is almost instantaneously built up inside the falling liquid jets in a HYLIFE (ICF) reactor. It has been suggested that the jets will breakup as a consequence of negative pressure occurring during the relaxation. This is important to both the subsequent condensation process and the chamber wall design. In this paper the mechanism of the relaxation of liquid jets after isochoric heating has been studied with both incompressible and compressible models. The transient pressure field predicted is qualitatively similar for both models and reveals a strongly peaked tension in the wake of a rarefaction wave. The pressure then rises monotonically in radius to zero pressure on the boundary. The incompressible approximation greatly over predicts the peak tension, which increases with time as the rarefaction wave moves toward the center of the jet. Since the tension distribution is as a narrow spike rather than uniform, a cylindrical fracture is the most likely mode of failure. The paper also discusses the available methods for estimating liquid tensile strength.

The hydraulic analysis of cylindrical Flibe jets in a HYLIFE-II ICF reactor

Abstract: In HYLIFE, a conceptual design of inertial confinement fusion reactors, a liquid jet array is proposed to protect the reactor chamber from fusion radiation. During the pulse of fusion the jets will sustain severe neutron and X-ray heating. Since the high energy neutrons can penetrate the material fairly well, they induce a nearly uniform and very large pressure rise within each jet. This energy is deposited within nanoseconds or much faster than the time scale for fluid dynamic relaxation. The analysis of the relaxation of the liquid jets in a HYLIFE reactor is therefore important for understanding the configuration of the liquid blanket, which is directly related with the vapor and liquid impacts on the chamber wall. The correct estimation of these impacts will allow designers to optimize the cost and strength of the reactor. The calculations for the cylindrical lithium jets in the HYLIFE-I reactor were done previously by using a compressible flow mode and a soft sphere equation of state developed by Young. A similar equation of state model for Flibe, the HYLIFE-II blanket material, was recently developed. This equation of state allows us to use the same compressible analysis code to calculate the pressure field in themore » Flibe jets and to estimate the upper bound of Flibe tension limit. With these results we can predict the possibility of the liquid breakup and the momentum distribution generated by relaxation and breakup.« less

HYLIFE-II: A Molten-Salt Inertial Fusion Energy Power Plant Design — Final Report

Abstract: Enhanced safety and performance improvements have been made to the liquid-wall HYLIFE reactor, yielding the current HYLIFE-II conceptual design. Liquid lithium has been replaced with a neutronically thick array of flowing molten-salt jets (Li[sub 2]BeF[sub 4] or Flibe), which will not burn, has a low tritium solubility and inventory, and protects the chamber walls, giving a robust design with a 30-yr lifetime. The tritium inventory is 0.5 g in the molten salt and 140 g in the metal of the tube walls, where it is less easily released. The 5-MJ driver is a recirculating induction accelerator estimated to cost $570 million (direct costs). Heavy-ion targets yield 350 MJ, six times per second, to produce 940 MW of electrical power for a cost of 6.5 cents/kW[center dot]h. Both larger and smaller yields are possible with correspondingly lower and higher pulse rates. When scaled up to 1934 MW (electric), the plant design has a calculated cost of electricity of 4.5 cents/kW[center dot]h. The design did not take into account potential improved plant availability and lower operations and maintenance costs compared with conventional power plant experience, resulting from the liquid wall protection. Such improvements would directly lower the electricity cost figures. For example,more » if the availability can be raised from the conservatively assumed 75% to 85% and the annual cost of component replacement, operations, and maintenance can be reduced from 6% to 3% of direct cost, the cost of electricity would drop to 5.0 and 3.9 cents/kW[center dot]h for 1- and 2-GW (electric) cases. 50 refs., 15 figs., 3 tabs.« less

Implementation of Molten Salt Properties into RELAP5-3D/ATHENA

Abstract: Molten salts are being considered as coolants for the Next Generation Nuclear Plant (NGNP) in both the reactor and the heat transport loop between the reactor and the hydrogen production plant because of their superior thermophysical properties compared to helium. Because specific molten salts have not been selected for either application, four separate molten salts were implemented into the RELAP5-3D/ATHENA computer program as working fluids. The implemented salts were LiF-BeF2 in a molar mixture that is 66% LiF and 34% BeF2, respectively, NaBF4-NaF (92% and 8%), LiF-NaF-KF (11.5%, 46.5%, and 42%), and NaF-ZrF4 (50% and 50%). LiF-BeF2 is currently the first choice for the primary coolant for the Advanced High- Temperature Reactor, while NaF-ZrF4 is being considered as an alternate. NaBF4-NaF and LiFNaF- KF are being considered as possible coolants for the heat transport loop. The molten salts were implemented into ATHENA using a simplified equation of state based on data and correlations obtained from Oak Ridge National Laboratory. The simplified equation of state assumes that the liquid density is a function of temperature and pressure and that the liquid heat capacity is constant. The vapor is assumed to have the same composition as the liquid and is assumed to be a perfect gas. The implementation of the thermodynamic properties into ATHENA for LiF-BeF2 was verified by comparisons with results from a detailed equation of state that utilized a soft-sphere model. The comparisons between the simplified and soft-sphere models were in reasonable agreement for liquid. The agreement for vapor properties was not nearly as good as that obtained for liquid. Large uncertainties are possible in the vapor properties because of a lack of experimental data. The simplified model used here is not expected to be accurate for boiling or single-phase vapor conditions. Because neither condition is expected during NGNP applications, the simplified equation of state is considered acceptably accurate for analysis of the NGNP.

Hylife-II Inertial Fusion Energy Power Plant Design

Abstract: The HYLIFE-II inertial fusion power plant design study uses a liquid fall, in the form of jets, to protect the first structural wall from neutron damage, x rays, and blast to provide a 30-y lifetime. HYLIFE-I used liquid lithium. HYLIFE-II avoids the fire hazard of lithium by using a molten salt composed of fluorine, lithium, and beryllium (Li2BeF4) called Flibe. Access for heavy-ion beams is provided. Calculations for assumed heavy-ion beam performance show a nominal gain of 70 at 5 MJ producing 350 MJ, about 5.2 times less yield than the 1.8 GJ from a driver energy of 4.5 MJ with gain of 400 for HYLIFE-I. The nominal 1 GWe of power can be maintained by increasing the repetition rate by a factor of about 5.2, from 1.5 to 8 Hz. A higher repetition rate requires faster re-establishment of the jets after a shot, which can be accomplished in part by decreasing the jet fall height and increasing the jet flow velocity. In addition, although not adequately considered for FIYLIFE-I, there is liquid splas...

The High‐Yield Lithium‐Injection Fusion‐Energy (HYLIFE)‐II inertial fusion energy (IFE) power plant concept and implications for IFE

Abstract: In the High‐Yield Lithium‐Injection Fusion‐Energy (HYLIFE) power plant design, lithium is replaced by molten salt. HYLIFE‐II [Fusion Technol. 25, 5 (1994)] is based on nonflammable, renewable‐liquid‐wall fusion target chambers formed with Li2BeF4 molten‐salt jets, a heavy‐ion driver, and single‐sided illumination of indirect‐drive targets. Building fusion chambers from existing materials with life‐of‐plant structural walls behind the liquid walls, while still meeting non‐nuclear grade construction and low‐level waste requirements, has profound implications for inertial fusion energy (IFE) development. Fluid‐flow work and computational fluid dynamics predict chamber clearing adequate for 6 Hz pulse rates. Predicted electricity cost is reduced about 30% to 4.4¢/kWh at 1 GWe and 3.2¢/kWh at 2 GWe. Development can be foreshortened and cost reduced by obviating expensive neutron sources to develop first‐wall materials. The driver and chamber can be upgraded in stages, avoiding separate and sequential facilities. Important features of a practical IFE power plant are ignition and sufficient gain in targets; low‐cost, efficient, rep‐ratable driver; and low‐cost targets.