The Safety and Tritium Applied Research (STAR) Facility
INL’s premier facility for tritium research and fusion-relevant materials testing.
Following the decision to close the Tritium System Test Assembly facility at Los Alamos National Laboratory, the DOE FES selected INL to host its new tritium research facility in October 2000.
This facility, now called the Safety and Tritium Applied Research Facility (STAR), has a unique capability to handle up to 1.6 grams (15,390 Ci) of tritium, along with low-level activated materials and several hazardous elements contained in fusion breeders, including beryllium, lead and lithium.
The 4,000-square-foot tritium facility incorporates various experiments to identify the potential risks and hazards associated with tritium retention and permeation in fusion and fission systems, supporting a broad range of public research programs and private industry developers.
What STAR supports
Characterization of hydrogen isotopes (Hydrogen, Deuterium, Tritium) transport properties in fusion materials, including plasma facing components, structures, breeders and specialized membranes for isotopes separation.
Perform tritium experiments on plasma facing and structural materials irradiated in test reactors to evaluate the impact of neutron damage.
Develop methods to efficiently extract tritium from breeder materials, including lithium bearing liquid metals and molten salts.
Experimental Research at the STAR Facility
STAR experiments provide the critical data needed to understand how fusion-relevant materials behave under real-world conditions. By combining tritium handling, plasma exposure and advanced diagnostics, these experiments support the safe and effective design of future fusion energy systems.
The Tritium Plasma Experiment
Primary Contact: Masashi Shimada
The Tritium Plasma Experiment (TPE) is a linear plasma device to accelerate deuterium and tritium plasma ions into metal target samples. The main focus of study is tungsten and tungsten alloys due to their favorable characteristics: high melting point, low sputtering rate, and low tritium solubility and retention.
TPE test samples are first irradiated at the High Flux Isotope Reactor to simulate fusion neutron damage. Then the samples are exposed to fusionrelevant plasma in TPE. The samples are examined using nuclear reaction analysis at Sandia National Laboratories in New Mexico to understand density profiles of deuterium and tritium inside the sample. Thermal desorption spectroscopy helps researchers understand the retention of deuterium and tritium in the sample material. This information informs the safety and operation of fusion reactors. Researchers also use positron annihilation spectroscopy to measure the size and density of radiation-induced defects associated with deuterium and tritium trapping.
TPE can generate a maximum ion flux of 1,023 ions/m2s with ion temperatures up to 600 electron volts. The safety limit for handling radioactive samples in the STAR facility is a dose rate of less than 10 μSv/hour. TPE can accept beryllium samples as well as other fusion metals, such as steel or tungsten.
Tritium Gas Absorption Permeation Experiment
Primary Contact: Masashi Shimada
The Tritium Gas Absorption Permeation (TGAP) Experiment measures tritium permeability in fusion and fission materials at low tritium partial pressure and can also study the solubility of tritium in molten lead-lithium. This liquid-metal material is of interest because it can serve as both coolant and tritium breeding material in a fusion reactor. Understanding how the tritium (that would be bred in this coolant) interacts with the parent coolant is necessary to know that tritium fuel can be safely handled in a fusion reactor. TGAP injects a measured small quantity of tritium gas (e.g., 0.1 milligram) into a sample of liquid metal and measures the tritium that leaves the sample.
Plasma Experiment for Asymmetric Surfaces
Primary Contact: Masashi Shimada
INL created a new experimental capability to develop superpermeable membranes to support the FES Blanket and Fuel Cycle program. This new apparatus, Permeation Experiment for Asymmetric Surfaces (PEAS), is designed to investigate hydrogen superpermeation behavior in a wide pressure range with in situ surface diagnostics on the front and back surfaces of a membrane. An atomic hydrogen source, an electron cyclotron resonance plasma source, and in situ Auger emission spectroscope modify and measure evolving surface chemistry under realistic conditions (e.g. helium, water, neon, etc.) that simulate fusion gas exhaust. PEAS can also test various hyperthermal atom sources (e.g. plasmas or filaments) under a wide range of pressures. We will address the critical research gaps in plasma-exhaust processing with PEAS and accelerate the technology development of metal-foil pumps.
Tritium Extraction eXperiment
Primary Contact: Thomas Fuerst
A team has designed and constructed a forced convection lead-lithium loop to test tritium extraction from molten PbLi. The Tritium Extraction eXperiment (TEX) is designed to operate at temperatures and tritium concentrations relevant to helium-cooled PbLi, water-cooled PbLi, and dual-coolant PbLi breeding blankets. The major systems consist of a moving magnet pump, source permeator, supply tank, test section and plenum. Additional subsystems are described, including flowmeters, pressure gauges, valves and heaters. TEX’s versatile design will enable code validation using simple tubular membranes, as well as determination of tritium-extraction efficiencies for alternative test sections.
Molten Salt Tritium Transport Experiment
Primary Contact: Thomas Fuerst
The Molten Salt Transport Experiment (MSTTE) is a forced-convection fluoride salt loop that can inject hydrogen isotopes into flowing molten salt and measure transport phenomena such as permeation through metals and evolution from free surfaces. The MSTTE is designed to be versatile in testing potential control technology in future campaigns. MSTTE is fabricated from mating a Copenhagen Atomics pump salt loop with an external test section equipped with hydrogen injection and measurement capabilities. Currently, MSTTE operates with the salt FLiNaK and deuterium as a surrogate for tritium.
Static Gas Absorption and Permeation Apparatus
Primary Contact: Thomas Fuerst
The Static Gas Absorption and Permeation Apparatus (SGAP) experiment is a dual-purpose tool to measure hydrogen and deuterium permeability, solubility, and diffusivity through materials. On the permeation side, planar samples are mounted with metal O-rings in a quartz vacuum boundary. Permeation rates are measured with a calibrated quadrupole mass spectrometer or by pressure buildup in a closed volume. On the absorption side, samples are inserted into a closed-end quartz tube. SGAP is able to test samples at hydrogen and deuterium pressures between 101 < PQ2 [Pa] < 105 and temperatures up to 950 C. The open-source data-analysis tool called the hydrogen permeation and absorption tool (HyPAT) provides rapid data analysis.
Hydrogen Experimental Apparatus for Thermal Diffusion
Primary Contact: Chase Taylor
Hydrogen diffusion in metals is driven by a concentration gradient (Fick’s law) and thermal diffusion (Soret diffusion). Thermal diffusion is the transport of hydrogen or other species due to a metal being held at a certain temperature. For example, hydrogen might migrate from the hot side to the cold side of a sample. Measuring Fickian diffusion is achieved through various permeation or absorption experiments; however, measuring thermal diffusion is challenging and has rarely been performed. The Hydrogen Experimental Apparatus for Thermal Diffusion Experiment is designed to induce thermal diffusion in samples and freeze those samples to analyze the hydrogen using separate techniques.
Salt-Hydrogen Universal Test Stand
Primary Contact: Anthony Bowers
The Salt-Hydrogen Universal Test Stand is a static-pot experimental system designed to measure hydrogen transport in advanced hydrogen-sensor technologies operating in molten salts and lead-lithium at high temperatures. The current configuration includes a residual gas analyzer, dry scroll pumps, a turbomolecular pump, a high-temperature heater, a data-acquisition system, a variable leak valve, a z-axis translator, a sparger, and a helical permeation sensor that can be replaced as sensor concepts evolve.
The liquid test cell is the heart of the system. It contains a silicon carbide crucible enclosed in a stainless-steel tube and mounted on a z-axis translation stage. Inside the crucible, two thermocouples monitor temperature conditions — one positioned within the permeation sensor to measure the temperature at the sensing interface and another along the inner crucible wall to capture broader thermal behavior. The permeation sensor sits at the center of the crucible, and a straight 1/8-inch sparger introduces hydrogen directly into the molten fluid.
The gas delivery system supplies a 2 vol% hydrogen-argon mixture and can further dilute the hydrogen concentration by increasing the flow of purge argon into the stream. This setup enables accurate and repeatable evaluation of a wide range of hydrogen sensor technologies, including future sensor designs.
STAR Materials Characterization
Each of the diagnostics at the STAR laboratory has been designed or customized to analyze tritium-contaminated or low-activation radioactive samples. However, nondestructive analysis and interchangeable parts for destructive analysis avoid cross-contaminating clean samples.
Glow discharge optical emission spectroscopy (GD-OES)
Primary Contact: Chase Taylor
Few techniques are capable of directly detecting and measuring hydrogen in materials. GD-OES provides a means to measure the composition and concentration of any element, including hydrogen, at depths up to 10-100s microns with nanometer-depth resolution.
A radio-frequency plasma is used to etch a 2-10 mm diameter crater in a conductive or nonconductive sample. The eroded material is optically stimulated from the plasma, and light from the plasma is transmitted into the analyzer section, which separates the light through a diffraction grating into its different wavelengths. Each wavelength corresponds to a different element, and an array of photomultiplier tubes simultaneously measures the elements of interest. The system also contains a monochromator that can analyze almost any additional wavelength that may not have a dedicated photomultiplier tube. An integrated interferometry system measures the real-time depth of the eroded crater.
The GD-OES, located at STAR, is configured for tens of elements, ranging from hydrogen to iron to tungsten.
X-ray Photoelectron Spectroscopy
Primary Contact: Chase Taylor
Surfaces dictate how materials interface and interact with their environment. This is especially true for phenomena such as permeation and plasma-surface interactions. X-ray photoelectron spectroscopy measures the surface chemistry of materials that occur within depths of 1-10 nanometers.
Low-energy X-rays are generated as a high-voltage filament releases electrons that impact an Al or Mg anode, selected for either higher resolution or intensity, respectively. The X-rays interact with the interrogated sample and, through the photoelectric effect, release electrons. Researchers use a hemispherical analyzer to detect the kinetic energy of these photoelectrons. The binding energy, which is used to identify the sample’s chemical composition, is easily calculated as the difference between the incident X-ray energy and the photoelectron kinetic energy and work function.
The PHI 5600-LS XPS system at STAR is configured with a dual anode X-ray source, a high-resolution monochromatic X-ray source, an ion-beam sputter gun for depth profiling, and an electron flood gun for charge neutralization. The large sample platen allows for dozens of samples to be mounted simultaneously, which can be programmatically analyzed.
Scanning Auger Microprobe
Primary Contact: Thomas Fuerst
Equipped with a rastering LaB6 filament-generated electron beam, a cylindrical mirror analyzer and a secondary electron detector, the scanning Auger microprobe (SAM) versatile diagnostic performs Auger electron spectroscopy (AES) as well as scanning electron microscopy (SEM).
AES provides the surface elemental composition of samples. The electron beam’s ability to raster enables elemental mapping of the surface (<5 nanometers). SAM elemental-mapping differs from conventional mapping systems (e.g., energy-dispersive X-ray spectroscopy) found in typical SEMs, which instead provides information from the bulk material (1-3 microns).
SEM produces high-magnification images of sample surfaces. Many processes modify the micro- and nanostructure of materials. Under fusion-relevant divertor conditions, the TPE at STAR can cause micro-fuzz to grow from tungsten surfaces. Plasma and ion irradiation can cause blistering of metals. These phenomena and more can be characterized using the SAM.
Positron Annihilation Spectroscopy
Primary Contact: Chase Taylor
At the atomic scale, all materials have defects in the form of occasionally missing atoms. High-powered transmission electron microscopes can measure large clusters of these missing atoms; however, positron annihilation spectroscopy (PAS) is the only technique that is sensitive to a single missing atom.
PAS uses positrons, or anti-electrons, that are emitted from a radioactive source, typically 22Na. Positrons from the source enter an adjacent sample and almost immediately slow down and begin a random walk through the atomic crystal lattice. If the positively charged positrons encounter a vacancy where an atom, or a cluster of atoms, is missing, the positron becomes trapped by the repulsive positive charge of the atoms lining the vacancy. Eventually, the positron will collide with an electron. When any antimatter touches its matter counterpart, the pair annihilates — in this case the mass of the positron and electron undergo a pure conversion into energy. This energy is detected as two 511 kiloelectron volt photons that are emitted almost exactly 180 degrees from each other.
STAR uses two PAS systems to measure defects in materials.
Coincidence Doppler broadening PAS uses two high-purity germanium detectors to measure the subtle shift in energy in the 511 keV annihilation photons. Positrons that annihilate with electrons at vacancies (valence electrons) produce annihilation photons close to 511 keV, while annihilation events with electrons in the defect-free bulk tend to deviate farther from 511 keV. This small difference provides a relative measure of defect concentration from one sample to another.
Positron annihilation lifetime spectroscopy employs two ultra-fast scintillating detectors. At almost exactly the same moment that a positron is emitted from 22Na, another photon is also released. One of the fast detectors measures this 1,274 keV photon, marks it as a start signal, and starts a timer. The stop signal is registered when the other detector measures the 511 keV annihilation photon. The time difference between the start and stop signal (i.e., positron lifetime) is a few hundred picoseconds (0.0000000001 sec). The lifetime is directly proportional to the size of the defects.
PAS measurements are important for understanding the mechanical properties of materials, catalysis efficiency, radiation-induced defects and semiconductor quality, among many other applications. In fusion materials, deuterium and radioactive tritium fuel become trapped in vacancies. PAS is especially important in correlating vacancy concentration and size to the amount of trapped deuterium and tritium.
Confocal Laser-Scanning Microscope
Primary Contact: Chase Taylor
A 3D laser-scanning confocal microscope can be used for quick, atmospheric, submicron sample imaging, for which virtually no sample preparation is required. The microscope combines standard optical microscopy with a scanning laser to produce high-resolution 3D images. Height data are obtained as the laser light reflects from the sample to a photomultiplier tube. A small pinhole aperture located in front of the tube detects only light that is completely in focus. By changing the objective lens height to bring the laser light into focus and repeating this for every X-Y position on the sample, the height data can be applied to the standard optical image for full 3D reconstruction. The confocal laser-scanning microscope (CLSM) also offers noncontact profilometry, ASTM grain-size measurements, particle counting and a host of other measurements.
Static Gas Absorption and Permeation Apparatus
Primary Contact: Thomas Fuerst
Fusion-relevant gases, such as deuterium, tritium and helium, become implanted in plasma-facing materials in fusion reactors. Because fusion reactors will have a regulatory limit of tritium on-site, it is important to understand and limit how much tritium is stuck in plasma-facing surfaces.
Researchers can determine the total amount of deuterium, tritium or helium that is trapped in materials using thermal desorption spectroscopy (TDS). To do so, a sample is heated at a very controlled rate. Quadrupole mass spectrometers measure the gases that come out of the sample. Correlating the gas emission with temperature helps determine the microstructural trapping mechanism in the material.
The TDS system at STAR uses an infrared tube furnace (Tmax = 1,100 C) and directly measures the sample’s surface temperature using redundant thermocouples. Of the two mass spectrometers on the system, a high-resolution unit is used to measure the minute mass difference between deuterium and helium (both nominally 4 amu). The system is calibrated using several National Institute of Standards and Technology-traceable leak
