Samuel G. Durbin

Turbulent Liquid Sheets for Protecting IFE Reactor Chamber First Walls

Abstract Turbulent liquid sheets have been proposed to protect solid structures in fusion power plants by absorbing damaging radiation. Establishing an experimental design database for this flow would therefore be valuable in various thick liquid protection schemes. The effect of initial conditions on the flow free-surface fluctuation was studied experimentally for vertical turbulent sheets of water issuing downwards from nozzles of thickness (small dimension) δ = 1 – 1.5 cm into ambient air. Sheets issuing from nozzles with both two- and three-dimensional fifth-order polynomial contractions with exit aspect ratios of 6.7 and 10 were investigated at Reynolds numbers ranging from 2 × 104 to 1 × 105. Mean velocity and turbulence intensity profiles were measured just upstream of the nozzle exit using laser-Doppler velocimetry to quantify initial conditions. Planar laser-induced fluorescence was used to visualize the free surface geometry of the liquid sheet in the near-field region up to 25δ downstream of the nozzle exit. Fluctuations of the free surface, or surface ripple, are characterized by the standard deviation in the position of the gas/liquid interface.

Guideline for bolted joint design and analysis : version 1.0.

This document provides general guidance for the design and analysis of bolted joint connections. An overview of the current methods used to analyze bolted joint connections is given. Several methods for the design and analysis of bolted joint connections are presented. Guidance is provided for general bolted joint design, computation of preload uncertainty and preload loss, and the calculation of the bolted joint factor of safety. Axial loads, shear loads, thermal loads, and thread tear out are used in factor of safety calculations. Additionally, limited guidance is provided for fatigue considerations. An overview of an associated Mathcad{copyright} Worksheet containing all bolted joint design formulae presented is also provided.

Assessment and Control of Primary Turbulent Breakup of Thick Liquid Sheets in IFE Reactor Cavities: The "Hydrodynamic Source Term"

Abstract The “hydrodynamic source term” has been identified as a possible issue for thick liquid protection schemes in inertial fusion energy reactor cavities. The hydrodynamic source term refers to the ejected droplets due to the primary turbulent breakup of the jets themselves. Droplets are continuously ejected from the surface of the jets and spread about the chamber, possibly interfering with driver propagation and target injection. Published correlations are examined in order to estimate upper limits for the hydrodynamic source term in the case of the robust point design (RPD-2002), an update to the High-Yield Lithium Injection Fusion Energy II (HYLIFE-II) design. Experimental data for vertical turbulent sheets of water issuing into ambient air downward from nozzles of thickness (small dimension) δ = 1 cm and aspect ratio of 10 are compared with the empirical correlations at near-prototypical Reynolds numbers of 1.3 × 105. A simple mass collection technique was developed to estimate the amount of ejected droplets from the jet surface. Boundary layer cutting is examined as a means of reducing the source term and improving surface smoothness. Alternate flow conditioning schemes are also explored to establish the relative importance of “traditional” flow straightening elements. Planar laser-induced fluorescence was used to visualize the free-surface geometry of the liquid sheet in the near-field region up to 25δ downstream of the nozzle exit. These results indicate that boundary layer cutting can suppress the hydrodynamic source term for a well-conditioned jet but is not a substitute for proper flow conditioning.

Experimental Studies of High-Speed Liquid Films on Downward-Facing Surfaces for Inertial Fusion Energy Wet Wall Concepts

The fusion event in inertial fusion energy (IFE) reactors creates neutrons, photons, and charged particles that can damage the chamber first walls. The Prometheus design study used a high-speed thin film of molten lead injected tangential to the wall to protect the upper endcap of the reactor chamber from damaging X rays and target debris. To assure full chamber coverage, the film must remain attached. Film detachment under the influence of gravity is most likely to occur on the downward-facing surfaces over the upper endcap of the reactor chamber. Accurate numerical predictions of detachment length are effectively impossible in this turbulent flow because of difficulties in determining appropriate boundary conditions near the detachment point. As part of the ARIES-IFE study, experimental investigations of high-speed water films injected onto downward-facing planar surfaces at angles of inclination up to 45 deg below the horizontal were therefore performed. The initial growth and subsequent detachment of films with initial thickness up to 2 mm and injection speed up to 11 m/s were measured. To our knowledge, these experiments are the first to investigate the detachment of turbulent liquid films on downward-facing surfaces. The implications of these initial results on thin liquid protection and the “wet wall” concept are discussed.

Flow Conditioning Design in Thick Liquid Protection

Abstract The HYLIFE-II conceptual design proposed using arrays of high-speed oscillating and stationary slab jets, or turbulent liquid sheets, to protect the reactor chamber first walls from damaging neutrons, ions and X-rays. Flow conditioning can be used to reduce turbulent fluctuations in these liquid sheets and thereby reduce surface ripple, or free-surface fluctuations, and delay jet breakup. Several flow conditioning configurations are studied experimentally for vertical turbulent sheets of water issuing downwards from nozzles of thickness (small dimension) δ = 1 cm into ambient air for Reynolds numbers Re = 5.0 × 104 and 1.2 × 105. In particular, the role of one or more fine screens in the flow conditioner was studied. As the flow conditioning element immediately upstream of the nozzle inlet, fine screens have been shown to have a major impact upon the sheet free-surface geometry. Planar laser-induced fluorescence was used to measure the free-surface geometry of the liquid sheet and its fluctuations in the near field at streamwise distances downstream of the nozzle exit x ≤ 25δ. Laser-Doppler velocimetry was used to quantify the impact of different conditioning configurations on the cross-stream velocity component and its fluctuations just upstream of the nozzle exit. The results indicate that minor differences in velocity and velocity fluctuations near the nozzle exit can lead to major variations in free-surface geometry, and that free-surface fluctuations are strongly affected by changes in flow conditioner design, even in the near-field region of the flow. A single-screen configuration was shown to produce the smoothest jets at both Reynolds numbers, with fluctuations of 3.3% at Re = 1.2 × 105 and x = 25δ.

Surface Fluctuation Analysis for Turbulent Liquid Sheets

Abstract A lattice consisting of arrays of stationary turbulent liquid sheets has been proposed for the HYLIFE-II inertial fusion energy reactor design to allow target injection and driver-beam propagation while protecting the first walls from damaging radiation. Interference between these sheets and the driver beams must be avoided, placing strict requirements on sheet free-surface fluctuations. Experiments were performed on nearly prototypical liquid sheets to determine the surface ripple and the absolute position of the free surface with respect to the nozzle exit. Planar laser-induced fluorescence was used to directly image the free surface at downstream distances up to 25 times the jet thickness (i.e., short dimension) at the nozzle exit δ for Reynolds numbers up to 130 000. Surface ripple, calculated using two different methods, was compared for two nozzle and two flow straightener designs. The surface ripple was found to be <0.05δ (versus the current HYLIFE-II requirement of 0.07δ). The mean thickness of the sheet was found to decrease with increasing x. This work should be useful in establishing the minimum distance between neighboring jets to avoid interference with the driver beams and to provide quantitative geometric data for shielding and neutronics analyses of such systems.

Impact of Boundary-Layer Cutting and Flow Conditioning on Free-Surface Behavior in Turbulent Liquid Sheets

Abstract The HYLIFE-II conceptual design uses arrays of high-speed oscillating and stationary slab jets, or turbulent liquid sheets, to protect the reactor chamber first walls. A major issue in thick liquid protection is the hydrodynamic source term due to the primary turbulent breakup of the protective slab jets. During turbulent breakup, drops are continuously ejected from the surface of turbulent liquid sheets and convected into the interior of the cavity, where they can interfere with driver propagation and target injection. Experimental data for vertical turbulent sheets of water issuing downwards from nozzles of thickness (small dimension) δ = 1 cm into ambient air are compared with empirical correlations at a nearly prototypical Reynolds number Re = 1.2 × 105. A simple collection technique was used to estimate the amount of mass ejected from the jet surface. The effectiveness of boundary-layer cutting at various “depths” into the flow to reduce the source term and improve surface smoothness was evaluated. In all cases boundary-layer cutting was implemented immediately downstream of the nozzle exit. Planar laser-induced fluorescence (PLIF) was used to visualize the free-surface geometry of the liquid sheet in the near-field region up to 25δ downstream of the nozzle exit. Large-scale structures at the edges of the sheet, typically observed for Re < 5.0 × 104, reappeared at Re = 1.2 × 105 for sheets with boundary-layer cutting. The results indicate that boundary-layer cutting can be used to suppress drop formation, i.e. the hydrodynamic source term, for a well-conditioned jet but is not a substitute for well-designed flow conditioning.

Analysis of dose consequences arising from the release of spent nuclear fuel from dry storage casks.

The resulting dose consequences from releases of spent nuclear fuel (SNF) residing in a dry storage casks are examined parametrically. The dose consequences are characterized by developing dose versus distance curves using simplified bounding assumptions. The dispersion calculations are performed using the MELCOR Accident Consequence Code System (MACCS2) code. Constant weather and generic system parameters were chosen to ensure that the results in this report are comparable with each other and to determine the relative impact on dose of each variable. Actual analyses of site releases would need to accommodate local weather and geographic data. These calculations assume a range of fuel burnups, release fractions (RFs), three exposure scenarios (2 hrs and evacuate, 2 hrs and shelter, and 24 hrs exposure), two meteorological conditions (D-4 and F-2), and three release heights (ground level - 1 meter (m), 10 m, and 100 m). This information was developed to support a policy paper being developed by U.S. Nuclear Regulatory Commission (NRC) staff on an independent spent fuel storage installation (ISFSI) and monitored retrievable storage installation (MRS) security rulemaking.

SHRAPNEL GENERATION FROM RECYCLABLE TRANSMISSION LINES

The ultimate goal of this research is to understand how the recyclable transmission lines (RTL) fail and break apart following each power generating pulse under inertial-fusion-energy-type loading. Containing and collecting the resulting dust, debris, and shrapnel so that it may be repetitively reprocessed and recycled is an especially important step, among many others, to successfully operating a power plant. In this paper the current and the dynamic pressure pulse along the RTL are simulated with the Micro-Cap network circuit code. These results are used as inputs to the CTH shock physics code that characterizes the debris formation and containment wall impacts. These models were applied to represent different sections of the RTL at two resolutions. The following discussion addresses the full size nested cone RTL for a Z-pinch IFE power plant.

Z-inertial fusion energy: power plant final report FY 2006.

This report summarizes the work conducted for the Z-inertial fusion energy (Z-IFE) late start Laboratory Directed Research Project. A major area of focus was on creating a roadmap to a z-pinch driven fusion power plant. The roadmap ties ZIFE into the Global Nuclear Energy Partnership (GNEP) initiative through the use of high energy fusion neutrons to burn the actinides of spent fuel waste. Transmutation presents a near term use for Z-IFE technology and will aid in paving the path to fusion energy. The work this year continued to develop the science and engineering needed to support the Z-IFE roadmap. This included plant system and driver cost estimates, recyclable transmission line studies, flibe characterization, reaction chamber design, and shock mitigation techniques.