Michael T. Tobin

Neutronics Analysis for HYLIFE-II

A preliminary neutronics analysis of the HYLIFE-2 reactor concept gives a tritium breeding ratio of 1.17 and a system energy multiplication factor of 1.14. Modified SS-316 (in which Mn is substituted for Ni) is superior to Hastelloy X and Hastelloy N as a firstwall material considering He generation, dpa-limited lifetime, and shallow-burial index. Since Flibe is corrosive to Mn metals, however, a favorable first-wall material is yet to be decided on. Flibe impurities considered (e.g., inherent impurities and those arising from wall erosion or secondary-coolant leakage) do not increase the hazard to the public over that of pure Flibe. The main issues for HYLIFE-2 are the high shallow-burial index (106) and the requirement to contain some 99.7% of the {sup 18}F inventory to prevent its release to the public 18 refs., 3 figs., 9 tabs.

Supersonic heat wave propagation in laser-produced underdense plasma for efficient x-ray generation

We have observed supersonic heat wave propagation in a low-density aerogel target (ρ ~ 3.2 mg/cc) irradiated at the intensity of 4 × 1014 W/cm2. The heat wave propagation was measured with a time-resolved x-ray imaging diagnostics, and the results were compared with simulations made with the two-dimensional radiation-hydrodynamic code, RAICHO. Propagation velocity of the ionization front very slightly decreased as the wave propagates into the target. The reason of decrease is due to increase of laser absorption region as the front propagates and interplay of hydrodynamic motion and reflection of laser propagation in the target. These features are well reproduced with the simulation.

X-Ray Response of National Ignition Facility First Surface Materials

The ablation of first surface materials by x rays is a primary threat to the final optics in the NIF target chamber. To meet the operational goals of the facility, the designs of the chamber wall, ...

Progress on Establishing Guidelines for National Ignition Facility (NIF) Experiments to Extend Debris Shield Lifetime

The survivability of the debris shields on the National Ignition Facility (NIF) are a key factor for the affordable operation of the facility. The improvements required over Nova debris shields are described. Estimates of debris shield lifetimes in the presence of target emissions with 4-8 J/cm 2 laser fluences indicate lifetimes that may contribute unacceptably to operations costs for NIF. We are developing detailed suggested guidance for target and experiment designers for NIF to assist in minimizing the damage to, and therefore the cost of, maintaining NIF debris shields. The guidance suggests a target mass quantity that as particulate on the debris shields (300 mg) may be within current operating budgets. It also suggests the amount of material that should become shrapnel on a shot (10 mg). Finally, it suggests the level of non-volatile residue (NVR) that would threaten the sol-gel coatings on the debris shields (1 μg/cm 2 ). We review the experimentation on the Nova chamber that included measuring quantities of particulate on debris shields by element and capturing shrapnel pieces in aerogel samples mounted in the chamber. We also describe computations of X-ray emissions from a likely NIF target and the associated ablation expected from this X-ray exposure on supporting target hardware. We describe progress in assessing the benefits of a pre-shield and the possible impact on the guidance for target experiments on NIF. Plans for possible experimentation on Omega and other facilities to improve our understanding of target emissions and their impacts are discussed. Our discussion of planned future work provides a forum to invite possible collaboration with the IFE community.

Inertial fusion energy power plant design using the Compact Torus Accelerator: HYLIFE-CT

The Compact Torus Accelerator (CTA), under development at Lawrence Livermore National Laboratory, offers the promise of a low-cost, high-efficiency, high energy, high-power-density driver for ICF and MICF (Magnetically Insulated ICF) type fusion systems. A CTA with 100 MJ driver capacitor bank energy is predicted to deliver {approximately}30 MJ CT kinetic energy to a 1 cm{sup 2} target in several nanoseconds for a power density of {approximately}10{sup 16} watts/cm{sup 2}. The estimated cost of delivered energy is {approximately}3

Adapting an X-Ray/Debris Shield to the Cascade ICF Power Plant: Neutronics Issues

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Neutronics Analysis of the Laboratory Microfusion Facility

100M for 30 MJ. This driver appears to be cost-effective and, in this regard, is virtually alone among IFE drivers. We discuss indirect-drive ICF with a DT fusion energy gain Q = 70 for a total yield of 2 GJ. The CT can be guided to the target inside a several-meter-long disposable cone made of frozen Li{sub 2}BeF{sub 4}, the same material as the coolant. We have designed a power plant including CT injection, target emplacement, containment, energy recovery, and tritium breeding. The cost of electricity is predicted to be 4.8 {cents}/kWh, which is competitive with future coal and nuclear costs.

Physics Issues Related to the Confinement of ICF Experiments in the U.S. National Ignition Facility

A neutronics analysis has been carried out to determine the effects on the Cascade ICF reactor concept of adding a solid-lithium x-ray and debris shield to each ICF capsule. Results indicate that tritium breeding in LiAlO{sub 2} is possible with a modest isotopic enhancement in {sup 6}Li (to 15%). The shallow-burial index is greater than 1 (indicating that deep burial may be required) if the blanket is kept in the reactor for more than 2.5 yr. Nine percent of the total thermal power is unrecoverable. Parts of the chamber wall may require replacement once during the reactor life due to radiation damage. Part of the SiC chamber end cap must be replaced annually. The reactor may not require any nuclear-grade construction. 20 refs., 4 figs., 3 tabs.

Design of the target area for the National Ignition Facility

The radiological safety hazards of the experimental area (EA) for the proposed Inertial Confinement Fusion (ICF) Laboratory Microfusion Facility (LMF) have been examined. The EA includes those structures required to establish the proper pre-shot environment, point the beams, contain the pellet yield, and measure many different facets of the experiments. The radiation dose rates from neutron activation of representative target chamber materials, the laser beam tubes and the argon gas they contain, the air surrounding the chamber, and the concrete walls of the experimental area are given. Combining these results with the allowable dose rates for workers, we show how radiological considerations affect access to the inside of the target chamber and to the diagnostic platform area located outside the chamber. Waste disposal and tritium containment issues are summarized. Other neutronics issues, such as radiation damage to the final optics and neutron heating of materials placed close to the target, are also addressed. 16 refs., 2 figs., 1 tab.

TSUNAMI Analysis of National Ignition Facility 2-D Gas Dynamics Phenomenon

ICF experiments planned for the proposed US National Ignition Facility [NIF] will produce emissions of neutrons, x rays, debris, and shrapnel. The NIF Target Area [TA] must acceptably confine these emissions and respond to their effects to allow an efficient rate of experiments, from 600 to possibly 1500 per year, and minimal down time for maintenance. Detailed computer code predictions of emissions are necessary to study their effects and impacts on Target Area operations. Preliminary results show that the rate of debris shield transmission loss [and subsequent periodicity of change‐out] due to ablated material deposition is acceptable, neutron effects on optics are manageable, and preliminary safety analyses show a facility rating of low hazard, non‐nuclear. Therefore, NIF Target Area design features such as fused silica debris shields, refractory first wall coating, and concrete shielding are effective solutions to confinement of ICF experiment emissions.