Selection of IFE target materials from a safety and environmental perspective

Self Cite

Z-pinch driven IFE (Z-IFE) requires the design of a repetitive target insertion system that allows coupling of the pulsed power to the target with adequate standoff, and a chamber that can withstand blast and radiation effects from large yield targets. The present strategy for Z-IFE is to use high yield targets (~2-3 GJ/shot), low repetition rate per chamber (~0.1 Hz), and 10 chambers per power plant. In this study, we propose an alternative power plant configuration that uses very high yield targets (20 GJ/shot) in a single chamber operating at 0.1 Hz. A thick-liquid-wall chamber is proposed to absorb the target emission (x-rays, debris and neutrons) and mitigate the blast effects on the chamber wall. The target is attached to the end of a conical shaped Recyclable Transmission Line (RTL) made from a solid coolant (e.g., frozen flibe), or a material that is easily separable from the coolant (e.g., steel). The RTL/target assembly is inserted through a single opening at the top of the chamber for each shot. This study looks at the RTL material choice from a safety and environmental point of view. Materials were assessed according to waste disposal rating (WDR) and contact dose rate (CDR). Neutronics calculations, using the TART2002 Monte Carlo code from Lawrence Livermore National Laboratory (LLNL), were performed for the RTL and Z-IFE chamber, and key results reported here.

Section: Recyclable Transmission Line (Rtl) Analysissupporting

confidence: 76%

Nuclear design considerations for Z-IFE chambers

Meier¹,

Schmitt²,

Abbott³

et al. 2006

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“…DOE Fusion Safety Standards limit dose in accident scenario to 10 mSv [32]. This value refers to a 50 year committed effective dose calculated to the most exposed individual at the site boundary (1 km) with contributions from direct cloudshine, and inhalation during plume passage [33].…”

Section: Accident Dosementioning

confidence: 99%

Neutronics and activation analysis of lithium-based ternary alloys in IFE blankets

Jolodosky

Kramer

Meier

et al. 2016

h i g h l i g h t s • Monte Carlo calculations were performed on numerous lithium ternary alloys. • Elements with high neutron multiplication performed well with low absorbers. • Enriching lithium decreases minimum lithium concentration of alloys by 60% or more. • Alloys that performed well neutronically were selected for activation calculations. • Alloys activated, except LiBaBi, do not pose major environmental or safety concerns. a b s t r a c t An attractive feature of using liquid lithium as the breeder and coolant in fusion blankets is that it has very high tritium solubility and results in very low levels of tritium permeation throughout the facility infrastructure. However, lithium metal vigorously reacts with air and water and presents plant safety concerns. The Lawrence Livermore National Laboratory is carrying an effort to develop a lithium-based ternary alloy that maintains the beneficial properties of lithium (e.g. high tritium breeding and solubility) and at the same time reduces overall flammability concerns. This study evaluates the neutronics performance of lithium-based alloys in the blanket of an inertial fusion energy chamber in order to inform such development. 3-D Monte Carlo calculations were performed to evaluate two main neutronics performance parameters for the blanket: tritium breeding ratio (TBR), and the fusion energy multiplication factor (EMF). It was found that elements that exhibit low absorption cross sections and higher q-values such as Pb, Sn, and Sr, perform well with those that have high neutron multiplication such as Pb and Bi. These elements meet TBR constrains ranging from 1.02 to 1.1. However, most alloys do not reach EMFs greater than 1.15. Additionally, it was found that enriching lithium with 6 Li significantly increases the TBR and decreases the minimum lithium concentration by more than 60%. The amount of enrichment depends on how much total lithium is in the alloy to begin with. Alloys that performed well in the TBR and EMF calculations were considered for activation analysis. Activation simulations were executed with 50 years of irradiation and 300 years of cooling. It was discovered that bismuth is a poor choice due to achieving the highest decay heat, contact dose rates, and accident doses. In addition, it does not meet the waste disposal ratings (WDR). Some of the activation results for alloys with Sn, Zn, and Ga were in the higher end and should be considered secondary to elements such as Sr and Ba that had overall better results. The results of this study along with other considerations such as thermodynamics, and chemical reactivity will help down select a preferred lithium ternary alloy.

“…Work is continuing to refine these analyses. Other recent and ongoing work in this area includes safety analyses for a target fabrication facility [19], a safety and environmental assessment of possible target materials [20], and the study of a fusion waste management system that maximize the amount of fusion materials that can be cleared or recycled [2 I].…”

Section: Safety and Environmentalmentioning

confidence: 99%

Progress toward heavy-ion IFE

Meier¹,

Logan²,

Waldron³

et al. 2002

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