[en] In support of the Tritium Facilities at the Savannah River Site (SRS), the Tritium Exposure Program (TEP) was initiated in 1986 to investigate the effects of tritium aging on metal hydride materials used in tritium processing applications. The primary material selected for tritium storage was the substituted LaNi₅ alloy, LaNi_4.25Al_0.75 (LANA.75). The substitution of Al for Ni served to lower the plateau pressure of the tritide, and to stabilize the material to cycling and tritium aging effects. The sub-atmospheric plateau pressure, of LANA.75 tritide at room temperature, made it a safe tritium storage medium, and the tritium aging effects were reduced from that of LaNi₅ tritide, but not eliminated. LANA.75 tritides retain the ³He decay product of absorbed tritium in the metal lattice. As the concentration of ³He grows, the lattice becomes strained due to the insoluble species. This strain is manifest in tritium aging effects. These effects include (1) a decrease in the equilibrium plateau pressure, (2) an increase in the plateau slope, (3) a reduction in the reversible storage capacity, and (4) the evolution of a tritium heel. The long term aging effects have been studied over the years, however the short term (less than one year) tritium aging effects have not been investigated until now. The acquisition of desorption isotherms at more than one temperature allows the thermodynamic parameters of change in enthalpy, ΔH, and change in entropy, ΔS, for the β-α phase transition of the metal tritide to be determined. These parameters are related to the equilibrium pressure, P, and the isothermal temperature, T, through the following relation: where R is the gas constant, and the factor of 1/2 yields results per mole of atomic tritium. A van't Hoff plot of 1/2 Ln(P) versus 1/T may be fitted to a straight line, with the slope and intercept used to determine ΔH and ΔS through equation

[en] Tritium aging studies have shown that LaNi_4.25Al_0.75 (LANA .75) tritide storage material undergoes significant degradation with tritium aging. After 5.4 years of dormant storage at full stoichiometry, which is considered a worst-case condition for this material, the performance is still acceptable for SRS tritium processing applications. The isotherms change, decreasing the desorption pressures, increasing the isotherm plateau slopes, and decreasing the total storage capacity. Eventually, the material will degrade with time to the point where it may no longer be useful for tritium processing applications. At the end of life, the tritium heel can be exchanged with protium or deuterium to produce a final material containing very little tritium

[en] Scanning electron microscope (SEM) images of polished surfaces, electron probe microanalysis, and X-ray powder diffractometry indicated the presence of a continuous Zr₂Fe phase with secondary phases of ZrFe₂, Zr₅FeSn, α-Zr, and Zr₆Fe₃O. A statistically-designed experiment to determine the effects of temperature, time, and vacuum quality On activation of St 198 revealed that when activated at low temperature (350 degrees C) deuterium absorption rate was slower when the vacuum quality was pwr (2.5 Pa vs. 3x10^-4 Pa). However, at higher activation temperature (500 degrees C), deuterium absorption rate was fast and was independent of vacuum quality. Deuterium pressure-composition-temperature (P-C-T) data are reported for St 198 in the temperature range 200--500 degrees C. The P-C-T data over the full range of deuterium loading and at temperatures of 350 degrees C and below is described by: K_0e-(ΔH_α/RT)=PD₂q²/(q*-q)² where ΔHα and K₀ have values of 101.8 kJ·mole^-1 and 3.24x10^-8Pa^-1, and q* is 15.998 kPa·L^-1·g^-1. At higher temperatures, one or more secondary reactions in the solid phase occur that slowly consume D₂ from the gas phase. XRD suggests these reactions to be: 2 Zr₂FeD_x → x ZrD₂ + x/3 ZrFe₂ + (2 - 2/3x) Zr₂Fe and Zr₂FeD_x + (2 -1/2x) D₂ → ZrD₂ + Fe, where 0 < x < 3. Reaction between gas phase deuterium and Zr2FC formed in the first reaction accounts for the observed consumption of deuterium from the gas phase by this reaction

[en] This document reports deuterium absorption and material phase characteristics of SAES St 198 Zr-Fe Alloy (76.5% Zr). Scanning electron microscope images of polished surfaces, electron probe microanalysis, and x-ray powder diffractometry indicated the presence of a primary Zr₂Fe phase with secondary phases of ZrFe₂, Zr₅FeSn, α-Zr, and Zr₆Fe₃O. A statistically designed experiment to determine the effects of temperature, time, and vacuum quality on activation of St 198 revealed that, when activated at low temperature (350C), deuterium absorption rate was slower when the vacuum quality was poor (2.5 Pa vs. 3 x 10^-4 Pa). However, at higher activation temperature (500C), deuterium absorption rate was fast and was independent of vacuum quality. Deuterium pressure-composition-temperature (P-C-T) data are reported for St 198 in the temperature range 200 to 500C. The P-C-T data over the full range of deuterium loading and at temperatures of 350C and below is described an expression. At higher temperatures, one or more secondary reactions in the solid phase occur that slowly consume D₂ from the gas phase. X-ray diffraction and other data suggest these reactions to be: 2 Zr₂FeD_x → xZrD₂ + x/3 ZrFe₂ + (2 - 2/3x) Zr₂Fe and Zr₂FeD_x + (2 - 1/2x) D₂ → 2 ZrD₂ + Fe, where 0 < x < 3. Reaction between gas-phase deuterium and Zr₂Fe formed in the first reaction accounts for the observed consumption of deuterium from the gas phase by this reaction

[en] The Savannah River Site (SRS) has been tasked by the Department of Energy (DOE) to design and construct a Tritium Extraction Facility (TEF) to process irradiated tritium producing burnable absorber rods (TPBARs) from a Commercial Light Water Reactor (CLWR). The plan is for the CLWR-TEF to provide tritium to the SRS Replacement Tritium Facility (RTF) in Building 233-H in support of DOE requirements. The CLWR-TEF is being designed to provide 3 kg of new tritium per year, from TPBARS and other sources of tritium (Ref. 1-4).The CLWR TPBAR concept is being developed by Pacific Northwest National Laboratory (PNNL). The TPBAR assemblies will be irradiated in a Commercial Utility light water nuclear reactor and transported to the SRS for tritium extraction and processing at the CLWR-TEF. A Conceptual Design Report for the CLWR-TEF Project was issued in July 1997 (Ref. 4).The scope of this Process Waste Assessment (PWA) will be limited to CLWR-TEF processing of CLWR irradiated TPBARs. Although the CLWR- TEF will also be designed to extract APT tritium-containing materials, they will be excluded at this time to facilitate timely development of this PWA. As with any process, CLWR-TEF waste stream characteristics will depend on process feedstock and contaminant sources. If irradiated APT tritium-containing materials are to be processed in the CLWR-TEF, this PWA should be revised to reflect the introduction of this contaminant source term

[en] Deuterated liquid scintillator detectors (NE230), which give excellent n/γ discrimination and provide a direct measure of the neutron energy spectrum, have been used to search for 2 to 3 MeV neutrons produced in d+d cold fusion. The apparatus consisted of an electrolytic cell using high-efficiency inverted-well geometry. Several samples of annealed Pd wire and a Pd casting (up to 13 g) were studied over a period of several weeks. An upper limit of ≤10^-3 fusion (n/s g) Pd was obtained corresponding to <7x10^-24 fusion (n/s) dd pair in our samples which excludes most of the reported positive results. Several sources of spurious signals, which could closely mimic signals from fusion neutrons, were also observed