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TFTR has begun its campaign to study deuterium-tritium fusion under reactor-like conditions. Variable amounts of deuterium and tritium neutral beam power have been used to maximize fusion power, study alpha heating, investigate alpha particle confinement, and search for alpha driven plasma instabilities. Additional areas of study include energy and particle transport and confinement, ICRF heating schemes for DT plasmas, tritium retention, and fusion in high βp plasmas. The majority of this work is done in the TFTR supershot confinement regime. To obtain supershots, extensive limiter conditioning using helium fueled ohmic discharges and lithium pellet injection into ohmic and neutral beam heated plasmas is performed, resulting in a low recycling limiter. The relationship between recycling and core plasma confinement has been studied by using helium, deuterium and high-Z gas puffs to simulate high recycling limiter conditions. These studies show that confinement in TFTR supershots is very sensitive to the influx of neutral particles at the plasma edge.

The high power D-T experiments on the tokamak fusion test reactor (TFTR) at the Princeton Plasma Physics Laboratory commenced in November 1993. During initial operation of the tritium systems a number of start-up problems surfaced and had to be corrected. These were corrected through a series of system modifications and upgrades and by repair of failed or inadequate components. Even as these operational concerns were being addressed, the tritium systems continued to support D-T operations on the tokamak. During the first six months of D-T operations more than 107 kCi of tritium were processed successfully by the tritium systems. D-T experiments conducted at TFTR during this period provided significant new data. Fusion power in excess of 9 MW was achieved in May 1994. This paper describes some of the early start-up issues, and reports on the operation of the tritium system and the tritium tracking and accounting system during the early phase of TFTR D-T experiments.

Two plateaux are observed in the desorption isotherm for palladium hydride: a lower plateau pressure for a hydrogen/metal atom ratio (H/M) less than about 0.3 and a slightly higher plateau pressure for H/M greater than about 0.3. This higher pressure corresponds to the reported pressure for palladium hydride. These observations were made for a large surface area palladium powder exposed to both protium and tritium. Helium buildup from tritium decay decreases the lower plateau pressure but does not affect the observations for H/M greater than about 0.3. A multiple-energy hydrogen site occupancy model is proposed to explain qualitatively both the dual plateau and the helium effect in palladium hydride.

Helium from tritium decay causes the desorption isotherm plateau pressure for LaNi4.25Al0.75 tritide to be lowered. From the shape of the 3He altered isotherm, it appears that the material becomes disordered and possibly disproportioned. The microstructure of the parent LaNi4.25Al0.75 tritide material is believed to influence the behavior of 3He from tritium decay.

Intermetallic compounds which react with hydrogen isotopes to form reversible hydrides offer several advantages for storing and processing tritium. Advantages include safe, low pressure, high density storage, and delivery of high purity 3He-free tritium without the use of pumps. As part of a program to devleop metal hydride technology for storing and processing tritium, the effects of tritium aging on the thermodynamic behavior of the tritides are under investigation. During aging of LaNi4.25Al0.75 tritides, the 3He decay product of tritium produced in the lattice does not leave the lattice but causes changes in the thermodynamics of the gas-solid system. Among the changes noted are (1) decreased tritium desorption pressures, (2) increased slopes of desorption isotherm plateaux and (3) small quantities of irreversibly-held tritium. Absorption-desorption cycling and brief heating of samples to 350°C while loaded with deuterium partially reverses these effects. While the desorption isotherms of tribium-aged LaNi4.25Al0.75 tritides resemble the desorption isotherms of amorphous hydrogen storage materials, X-ray diffraction patterns of tritium-aged samples after desorption of tritium do not exhibit the characteristics of an amorphous material. The diffraction patterns show broadening and anisotropic effects that suggest the presence of lattice strains and orientational effects of 3He in the LaNi4.25Al0.75 lattice. Self-interstitials, dislocations and bubbles are probably present in the aged samples.

Helium dynamics in La-Ni-Al tritides have been observed by measuring the plateau pressure decrease for the pressure of tritium in equilibrium with the solid as a function of helium composition. Calculations suggest that a crystal lattice volume expansion, caused by helium, stabilizes the tritide. Temperature cycling the helium-altered, tritium-saturated intermetallic partially restores the plateau pressure. These data are discussed in the context of immobile helium which can gain mobility as the tritide ages.

The absorption spectrum of PuF 6 is investigated using a long-pass multiple reflection cell. Cross sections over the spectral region of 3000–9000 A are reported. Due to the enhanced sensitivity of our apparatus the wavelengths and absorption cross sections are significantly improved over the previously available data.