TRITIUM BARRIER MATERIALS AND SEPARATION SYSTEMS FOR THE NGNP

Contamination of downstream hydrogen production plants or other users of high-temperature heat is a concern of the Next Generation Nuclear Plant (NGNP) Project. Due to the high operating temperatures of the NGNP (850-900 C outlet temperature), tritium produced in the nuclear reactor can permeate through heat exchangers to reach the hydrogen production plant, where it can become incorporated into process chemicals or the hydrogen product. The concentration limit for tritium in the hydrogen product has not been established, but it is expected that any future limit on tritium concentration will be no higher than the air and water effluent limits established by the NRC and the EPA. A literature survey of tritium permeation barriers, capture systems, and mitigation measures is presented and technologies are identified that may reduce the movement of tritium to the downstream plant. Among tritium permeation barriers, oxide layers produced in-situ may provide the most suitable barriers, though it may be possible to use aluminized surfaces also. For tritium capture systems, the use of getters is recommended, and high-temperature hydride forming materials such as Ti, Zr, and Y are suggested. Tritium may also be converted to HTO in order to capture it on molecular sieves or getter materials. Counter-flow of hydrogen may reduce the flux of tritium through heat exchangers. Recommendations for research and development work are provided

DOE handbook: Tritium handling and safe storage

The DOE Handbook was developed as an educational supplement and reference for operations and maintenance personnel. Most of the tritium publications are written from a radiological protection perspective. This handbook provides more extensive guidance and advice on the null range of tritium operations. This handbook can be used by personnel involved in the full range of tritium handling from receipt to ultimate disposal. Compliance issues are addressed at each stage of handling. This handbook can also be used as a reference for those individuals involved in real time determination of bounding doses resulting from inadvertent tritium releases. This handbook provides useful information for establishing processes and procedures for the receipt, storage, assay, handling, packaging, and shipping of tritium and tritiated wastes. It includes discussions and advice on compliance-based issues and adds insight to those areas that currently possess unclear DOE guidance

LUX-ZEPLIN (LZ) Technical Design Report

In this Technical Design Report (TDR) we describe the LZ detector to be built at the Sanford Underground Research Facility (SURF). The LZ dark matter experiment is designed to achieve sensitivity to a WIMP-nucleon spin-independent cross section of three times ten to the negative forty-eighth square centimeters

Fusion transmutation of waste: design and analysis of the in-zinerator concept.

Due to increasing concerns over the buildup of long-lived transuranic isotopes in spent nuclear fuel waste, attention has been given in recent years to technologies that can burn up these species. The separation and transmutation of transuranics is part of a solution to decreasing the volume and heat load of nuclear waste significantly to increase the repository capacity. A fusion neutron source can be used for transmutation as an alternative to fast reactor systems. Sandia National Laboratories is investigating the use of a Z-Pinch fusion driver for this application. This report summarizes the initial design and engineering issues of this ''In-Zinerator'' concept. Relatively modest fusion requirements on the order of 20 MW can be used to drive a sub-critical, actinide-bearing, fluid blanket. The fluid fuel eliminates the need for expensive fuel fabrication and allows for continuous refueling and removal of fission products. This reactor has the capability of burning up 1,280 kg of actinides per year while at the same time producing 3,000 MWth. The report discusses the baseline design, engineering issues, modeling results, safety issues, and fuel cycle impact

Controlling the interstitial element concentration in Ti-6Al-4V using calciothermic reduction

The production of Ti-6Al-4V components via powder metallurgy routes is looked upon as an efficient production method that reduces wastage, but leaves finished products with high interstitial oxygen concentrations that do not meet industrial standards. The ability to control the interstitial oxygen concentration in Ti-6Al-4V powder metallurgy would improve the viability of near net shape processing for the production of industrial components. One process that has demonstrated the ability to remove oxygen from titanium alloys is calciothermic reduction, which is a reduction process originally developed to reduce titanium dioxide to commercial purity titanium using a molten flux of calcium and calcium chloride. The aim of this thesis is to examine whether calciothermic reduction can be used to control the interstitial concentration of oxygen and nitrogen in powder metallurgy Ti-6Al-4V and understand the reaction mechanisms that enable this process to work. By understanding these mechanisms, the process can then be optimised to improve the properties of powder metallurgy Ti-6Al-4V components, and provide a basis to extend this to other alloy systems. Calciothermic reduction was demonstrated to be effective at reducing the interstitial oxygen concentration in powder metallurgy Ti-6Al-4V to acceptable industrial standards (< 2,000 wt .ppm). The optimisation of the process required the balance of thermodynamics and kinetics to be controlled; thermodynamics was important to ensuring the reaction would begin, with the kinetics becoming more important during the reduction process because the removal of interstitial oxygen concentration relied upon a diffusion based mechanism. Evaluation of the mechanism that underpins the removal of oxygen via calciothermic reduction, was assessed using a FIB-SIMS based technique. This method of analysis was developed during this research and demonstrated to be effective at quantifying interstitial oxygen concentrations in titanium alloy, which was used to confirm the formation of oxygen concentration gradients from titanium alloy bulk to the surface during calciothermic reduction. Further investigation of the reduction process indicated that calciothermic reduction could facilitate the nitriding of Ti-6Al-4V in a sealed air environment, forming a wear resistant surface layer in a novel process referred to as “Calciothermic Assisted Immersion Nitriding” (CAIN). The nitriding process produced a consistent TiCxNyOZ surface layer where the chemical composition of the layer developed in a three stage reaction involving the inward diffusion of interstitial carbon and nitrogen, whilst oxygen was removed from the surface. This surface layer improved the tribological properties of the Ti-6Al-4V samples by changing the wear mechanism from adhesive to abrasive, which resulted in an increased wear resistance, which was comparable to a commercial produced, physical vapour deposition TiCN coating.Open Acces

DarkSide-20k: A 20 tonne two-phase LAr TPC for direct dark matter detection at LNGS

This paper describes a preliminary design for the experiment, in which the DarkSide-20k LAr TPC is deployed within a shield/veto with a spherical Liquid Scintillator Veto (LSV) inside a cylindrical Water Cherenkov Veto (WCV