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The effects of neutron irradiation to 10 dpa at 500 and 800 °C on a high-quality three-dimensional balanced weave composite (FMI-222) is presented. Strength and dimensional stability for this system is compared to earlier work on this material, at lower dose, and contrasted with that of a well studied isotropic graphite (POCO AXF-5Q) irradiated at identical conditions. For both irradiation temperatures the composite strength in bending is substantially increased. While both irradiation temperatures cause contraction along the bend bar axis, the amount of contraction is greater for the higher temperature irradiation. Moreover, for the 500 °C irradiation the corresponding decrease in volume is observed, though an apparent large increase in volume occurs for the 800 °C irradiated composite. This departure from isotropic dimensional change is explained in terms of fiber dimensional stability model previously presented.

Specimens of pure copper, a high purity austenitic stainless steel, and V–4Cr–4Ti were exposed to eight cycles of either constant temperature or periodic temperature variations during neutron irradiation in the High Flux Isotopes Reactor to a cumulative damage level of 4–5 displacements per atom. Specimens exposed to periodic temperature variations experienced a low temperature (360 °C) during the initial 10% of accrued dose in each of the eight cycles, and a higher temperature (520 °C) during the remaining 90% of accrued dose in each cycle. The microstructures of the irradiated stainless steel and V–4Cr–4Ti were qualitatively similar to companion specimens that were continuously maintained at 520 °C during the entire irradiation. The microstructural observations on pure copper irradiated at a constant temperature of 340 °C in this experiment are also summarized. The main radiation-induced microstructural features consisted of dislocation loops, stacking fault tetrahedra and voids in the stainless steel, Ti-rich precipitates in the V alloy, and voids (along with a low density of stacking fault tetrahedra) in copper.

Post-irradiation examination has started and initial results are available for the varying temperature irradiation experiment conducted in the high flux isotope reactor (HFIR), carried out in the framework of the Japan–USA Fusion Cooperation Program (JUPITER project). This experiment is an unprecedented controlled irradiation experiment designed for symmetrical comparison of isothermal and temperature-variant neutron irradiation effects. This paper summarizes the irradiation experiments and initial results obtained from the post-irradiation examination of an austenitic alloy, vanadium, a vanadium alloy and copper. These preliminary results extend the trends observed in earlier, lower fluence experiments, with some effects of the low temperature phase of variable temperature irradiation on evolving microstructures.

A temperature controlled instrumented capsule has been irradiated in the RB* position of the high flux isotope reactor (HFIR) at the Oak Ridge National Laboratory in order to perform in situ thermal conductivity measurements of monolithic ceramics and composite materials during neutron irradiation. This determination of thermal conductivity utilizes a temperature gradient technique whereby two thermocouples measure the absolute temperature along a cylindrical sample which is constrained to one-dimensional thermal conduction. The heat source is the intrinsic gamma heating of the core region of the HFIR. This paper provides an overview of the experiment and gives preliminary results on the degradation in thermal conductivity of a few ceramic specimens measured as a function of irradiation temperature (200–700°C) and fast neutron fluence up to ∼3.4 × 1025 n/m2 (E>0.1 MeV ) .

An experiment to directly compare the effects of neutron fluence received at steady temperature on microstructure and mechanical properties of candidate fusion reactor structural materials to the effects of receiving 10% of the fluence at reduced temperature has been designed. The Varying Temperature Experiment is being fabricated for irradiation in a large Removable Beryllium (RB) position of the High Flux Isotope Reactor (HFIR). For this experiment, specimen temperatures are elevated and controlled whenever there is substantial neutron fluence to the specimens (reactor power > 10%). Half of the specimens are irradiated at two distinct temperatures, and half are irradiated at constant temperature. The capsule features to meet these requirements are described. The experiment will operate for ten reactor cycles beginning in early 1998. This project is a collaborative effort under the Japan-USA cooperative program (Jupiter Project).

The deuterium-tritium (D-T) experimental program on the Tokamak Fusion Test Reactor (TFTR) is underway and routine tritium operations have been established. The technology upgrades made to the TFTR facility have been demonstrated to be sufficient for supporting both operations and maintenance for an extended D-T campaign. To date fusion power has been increased to {approximately}9 MW and several physics results of importance to the D-T reactor regime have been obtained: electron temperature, ion temperature, and plasma stored energy all increase substantially in the D-T regime relative to the D-D regime at the same neutral beam power and comparable limiter conditioning; possible alpha electron heating is indicated and energy confinement improvement with average ion mass is observed; and alpha particle losses appear to be classical with no evidence of TAE mode activity up to the P{sub FUS} {approximately}6 MW level. Instability in the TAE mode frequency range has been observed at P{sub FUS} > 7 MW and its effect on performance is under investigation. Preparations are underway to enhance the alpha particle density further by increasing fusion power and by extending the neutral beam pulse length to permit alpha particle effects of relevance to the ITER regime to be more fullymore » explored.« less

An eight-shot pneumatic pellet injector has been developed for routine plasma fueling and optimization studies on short-pulse fusion experiments. Such experiments will require injection sequences of several pellets of various size over the discharge period. Two eight-shot injectors that are capable of producing and firing hydrogen and deuterium pellets have been built. The injectors are based on the pipe-gun concept, which generates deuterium and hydrogen pellets by direct condensation in the barrel. One injector is in operation on the Princeton Beta Experiment, and the other is operational on the Advanced Toroidal Facility (ATF). A general overview of the gun, the ATF injection line, and the ATF diagnostic systems is given. >

The architecture of a comprehensive signal validation system (SVS), which integrates various signal processing modules, is described. The architecture of the SVS consists of several parallel signal processing modules, with each module operating independently. The functional coordination of the modules and the decision about the overall signal status are performed by a system executive. The various techniques have been tested using pressurized water reactor plant operational data. The diversity of the modules increases the reliability of the decision about the validity of measurements. >

The varying temperature experiment HFIR-RB-13J has been assembled and inserted in the reactor. Approximately 5300 specimens were cleaned, inspected, matched, and loaded into four specimen holders. A listing of each specimen loaded into the steady temperature holder, its position in the capsule, and the identification of the corresponding specimen loaded into the varying temperature holder is presented in this report.

A capsule has been designed that permits four specimen sets to be irradiated in an RB* location in the High Flux Isotope reactor (HFIR) with distinct temperature histories. During the reporting period critical component prototyping was completed. The results have lead to some design and operational changes from that previously reported. The primary design changes are (1) compression seals in the specimen holes of the beryllium holders, and (2) oxide-dispersion strengthened aluminum alloy (DISPAL) specimen sleeves in all holders. Details of the capsule design are presented in the previous issue of this publication. Four, axially displaced temperature zones are independently controlled. Holder temperatures are monitored by thermocouples and controlled by a combination of adjustable temperature control gas mixtures and auxiliary heaters. The high temperature holders are located in the center of the experimental region, which is centered on the reactor mid-plane, and the low temperature holders are located at the ends of the experimental region.

The purpose of this experiment is to determine effects of temperature variation during irradiation on microstructure and mechanical properties of potential fusion reactor structural materials. A varying temperature irradiation experiment is being performed under the framework of the Japan-USA Program of Irradiation Tests for fusion Research (JUPITER) to study the effects of temperature variation on the microstructure and mechanical properties of candidate fusion reactor structural materials. An irradiation capsule has been designed for operation in the High Flux Isotope Reactor at Oak Ridge National Laboratory that will allow four sets of metallurgical test specimens to be irradiated to exposure levels ranging from 5 to 10 dpa. Two sets of specimens will be irradiated at constant temperature of 500{degrees}C and 350{degrees}C. Matching specimen sets will be irradiated to similar exposure levels, with 10% of the exposure to occur at reduced temperatures of 300{degrees}C and 200{degrees}C.

The TRIST-ERI capsule was assembled and irradiated in a large Removable Beryllium (RB{star}) position of the High Flux Isotope Reactor (HFIR) during this reporting period. Irradiation began on March 8, 1996, was completed on June 20, 1996, during operating cycles 344, 345, and 346. This report describes the thermal operation of the capsule.

A collaborative DOE/Monbusho series of irradiation experiments is being implemented to determine, in situ, the effects of irradiation on the electrical resistivity of ceramic materials. The first experiment, TRIST-ER1, has been designed to irradiate 15 Al{sub 2}O{sub 3} test specimens at 450{degrees}C in an RB position of the High Flux Isotope Reactor (HFIR). Each test specimen is located in a sealed vanadium subcapsule with instrumentation provided to each subcapsule to measure temperature and resistance, and to place a biasing voltage across the specimen. Twelve of the specimens will be biased with 200 V/mm across the sample at all times, while three will not be biased, but can be if so desired during the irradiation. The experiment design, component fabrication, and subcapsule assembly have been completed. A three cycle irradiation, to a fast neutron (E>0.1 MeV) fluence of about 3x10{sup 25}n/m{sup 2} ({approx}3 dpa in Al{sub 2}O{sub 3}), is expected to begin early in March 1996.

Summary form only given. A synchronization system for high-speed photography using pulsed light sources, standard video cameras, and video recorders is discussed. This system enabled near-real-time visualization of the pellet shape, size, and flight trajectory over a wide range of pellet speeds and at one or two positions along the flight path. The system provides synchronization pulses to the data system for pseudo-points along the flight path, such as the estimated plasma edge. This was accomplished using an electronic system that took the time measured between sets of light gates and generated proportionally delayed triggers for light source strobes and pseudo-points.

Several advanced plasma fueling systems are under development at the Oak Ridge National Laboratory (ORNL) for present and future magnetic confinement devices. These include multishot and repeating pneumatic pellet injectors, centrifuge accelerators, electrothermal guns, a Tritium Proof-of-Principle experiment, and an ultrahigh velocity mass ablation driven accelerator. A new eight-shot pneumatic injector capable of delivering 3.0 mm, 3.5 mm, and 4.0 mm diameter pellets at speeds up to 1500 m/s into a single discharge has been commissioned recently on the Tokamak Fusion Test reactor. The so-called Deuterium Pellet Injector (DPI) is a prototype of a Tritium Pellet Injector (TPI) scheduled for use on TFTR in 1990. Construction of the TPI will be preceded by a test of tritium pellet fabrication and acceleration using a 4 mm bore ''pipe gun'' apparatus. A new repeating pneumatic pellet injector capable of 2.7 mm, 4 mm, and 6 mm operation is being installed on the Joint European Torus to be used in ORNL/JET collaborative pellet injection studies. A 1.5 m centrifuge injector is being developed for application on the Tore Supra experiment in 1988. The new device, which is a 50% upgrade of the prototype centrifuge used on D-III, features a pellet feed mechanism capablemore » of producing variable-size pellets (1.5 to 3.0 mm diameter) optimally shaped to survive acceleration stresses. Accelerating pellets to velocities in excess of 2 km/s is being pursued through two new development undertakings. A hydrogen plasma electrothermal gun is operational at 2 km/s with 10 mg hydrogen pellets; this facility has recently been equipped with a pulsed power supply capable of delivering 1.7 kJ millisecond pulses to low impedence arc loads.« less