Dale G. Tuggle

Nitriding reactions with a Zr–Mn–Fe metal getter

Abstract The metal getter Zr–Mn–Fe (SAES ST909) is an important component of a metal hydride-based tritium clean-up system at Los Alamos National Laboratory (LANL). The system is normally used to clean a glovebox with a helium/nitrogen atmosphere. During start-up operations, it was found that the Zr–Mn–Fe alloy exhibited an anomaly during activation, namely an exotherm upon initial exposure to nitrogen. The purpose of this work is to better understand this nitriding reaction. Nitrogen absorption studies, temperature profile experiments, and powder X-ray diffraction (XRD) were used to study the nitriding reaction. An exothermic reaction between nitrogen and ST909 was observed at ∼450°C only when the getter was heated for the first time. ST909 that had been previously heated without nitrogen did not produce an exotherm when heated a second time with nitrogen. Based on the XRD evidence, it was speculated that nitrogen reacts exothermically with the zirconium in the ST909 material. After heating above ∼660°C, the aluminum binder in the ST909 melts and may alloy with the zirconium. The resulting alloy appears to be less reactive with nitrogen and does not produce an exotherm.

Hydrogen, deuterium and tritium in palladium : An elastic constants study

We have used resonant ultrasound spectroscopy to measure the three independent elastic constants of Pd-H, Pd-D, and Pd-T single crystal at 300K as a function of hydrogen, deuterium, and tritium concentration, respectively. The addition of interstitial H (D, or T) atoms, located at (0,½,0) in the fcc Pd lattice, affects all three elastic constants C’, C44, and B. In the mixed (α+β) phase, and with increasing H isotope, the shear modulus C’ shows an abnormal softening whereas C44 and B do not. This is explained in terms of Zener-type an elastic relaxations affecting the shape of the hydride phases in the coherent(α+β) two-phase mixture In the single β-phase, C’ shows a strong isotope dependence whereas C44 and B show none. This behavior is explained in terms of differences in the excitation of optical phonons. In Pd-T, 3He is produced by the radioactive decay of tritium. We have measured in situ the swelling and the change in the elastic constants in Pd-T as a function of aging time. Aging (3He formation) affects all three elastic constants. These measurements are being used to understand the early stages of 3H-3He cluster formation in aged Pd-T crystal.

Thermal Cycling Absorption Process (TCAP): Instrument and Simulation Development Status at Los Alamos National Laboratory

The Thermal Cycling Absorption Process (TCAP) Project at Los Alamos National Laboratory has been a collaborative effort with Savannah River Site to demonstrate the Tube-in-Tube (TnT) column design and to improve TCAP science. TnT TCAP is an alternative design which uses a liquid to thermally cycle the metal hydride packed column. Inert gas displacement tests and deuterium pulse tests have been performed on the TnT TCAP column. The inert gas displacement tests are designed to measure plug flow in the column while the deuterium pulse tests determine the separation ability of the column. A residual gas analyzer measures the gases in the exit stream and the experimental results are compared with pulse test model results.

High-Concentration Tritium Sensor

A bi-layer device was fabricated and tested for the direct collection of electrons emitted by tritium beta decay. The sensor functions at high pressures and concentrations where previously no simple and cost effective direct measurement technique existed for tritium. A polished KOVARTM (Fe-Ni-Co alloy) rod was coated with a 1-μm thick insulating layer of alumina using electron-beam evaporation, physical vapor deposition (PVD) of alumina with oxygen dosing. The alumina deposition process was optimized to minimize pinholes and obtain a stable coating with high resistivity. The detector exhibited a nanoampere electrical response over a few decades of tritium concentration, up to pure tritium at 200 kPa. The sensor has been in service for several months now without showing signs of degradation and no discernible physical damage or change in efficiency has been observed.

Design, fabrication, and testing of a getter-based atmosphere purification and waste treatment system for a nitrogen-hydrogen-helium glovebox

Abstract A system containing a combination of getters (Zr-Mn-Fe, SAES St909; and Zr2Fe, SAES St198) was used to process the nitrogen-hydrogen-helium atmosphere in a glovebox used for handling metal tritide samples. During routine operations, the glovebox atmosphere is recirculated and hydrogenous impurities (i.e. CQ4, Q2O, and NQ3, where Q [is equivalent to] H, D, T) are decomposed (cracked) and removed by Zr-Mn-Fe without absorbing elemental hydrogen isotopes. If the tritium content of the glovebox atmosphere becomes unacceptably high, the getter system can rapidly strip the glovebox atmosphere of all hydrogen isotopes by absorption on the Zr2Fe, thus lessening the burden on the facility waste gas treatment system. The getter system was designed for high flowrate (> 100 l/min), which is achieved by using a honeycomb support for the getter pellets and 1.27-cm diameter tubing throughout the system for reduced pressure drop. The novel getter bed design also includes an integral preheater and copper liner to accommodate swelling of the getter pellets, which occurs during loading with oxygen and carbon impurities. Non-tritium functional tests were conducted to determine the gettering efficiencies at different getter bed temperatures and flowrates by recirculating gas through the system from a 6-m3 glovebox containing known concentrations of impurities.