The Department of Energy’s Advanced Turbine Systems (ATS) program is aimed at fostering the devel-opment of a new generation of land-based gas turbine systems with overall efficiencies significantly be-yond those of current state-of-the-art machines, as well as greatly increased times between inspection and refurbishment, improved environmental impact, and decreased cost. The proposed duty cycle of ATS ma-chines will emphasize different criteria in the selection of materials for the critical components. In par-ticular, thermal barrier coatings (TBCs) will be an essential feature of the hot gas path components in these machines. The goals of the ATS will require significant improvements in TBC technology, since these turbines will be totally reliant on TBCs, which will be required to function on critical components such as the first-stage vanes and blades for times considerably longer than those experienced in current applications. Important issues include the mechanical and chemical stability of the ceramic layer and the metallic bond coat, the thermal expansion characteristics and compliance of the ceramic layer, and the thermal conductivity across the thickness of the ceramic layer.

One of the supporting elements of the Advanced Turbine Systems (ATS) Program is the materials/manufacturing technologies task.The objective of this element is to address critical materials issues for both industrial and utility gas turbines.DOE Oak Ridge Operations Office (ORO) will manage this element of the program, and a team from DOE-OR0 and Oak Ridge National Laboratory is coordinating the planning for the materials/manufacturing effort.This paper describes that planning activity which is in the early stages.

Analysis of the investigative data pertaining to this incident reveals the following conditions as key findings and probable causes: (1) The contractor failed to properly implement the surveillance program for monitoring reactor pressure vessel embrittlement. (2) Contractor and DOE organizations provided less than adequate oversight and independent overview, especially by not requiring operating organizations to provide documented evidence to substantiate claims that there was ''no problem'' with respect to embrittlement. (3) Although the temperature limitation for reactor pressurization identified in the Technical Specifications was never violated, the basis of this safety limitation was violated. (4) The basis for concluding that there would be no embrittlement of the pressure vessel steel over the expected life of the reactor is questionable. (5) The contractor and DOE failed to make the surveillance program visible by incorporating it in the Technical Specifications. (6) The Accident Analysis/Final Safety Analysis Report was never adequately reviewed and updated subsequent to its initial issuance. (7) Surveillance specimen analysis was incomplete and never transmitted to reactor operating personnel in a usable format prior to November 1986. (8) There was extensive delays (many years) in the testing, analysis, and reporting of surveillance program results.

Sufficient data exist to provide a high level of confidence that refractory-alloy-clad ceramic fuel pins and refractory structural alloys can be used successfully in an operational space power system. However, data are not yet sufficient to ensure that these materials can meet the temperature, lifetime, and system mass envelope requirements for reliable operation of a 100 kW(e) system as specified by the SP-100 Project. Development efforts to provide these data are being initiated.

The performance was determined of refractory metal alloys and uranium nitride fuel element specimens in flowing 1900F (1083C) lithium. The results demonstrate the suitability of the selected materials to perform satisfactorily from a chemical compatibility standpoint.

Advanced Rankine and other proposed space power systems utilize refractory metals in contact with both single-phase and two-phase alkali metals at elevated temperatures. A number of recent compatibility experiments are described which emphasize the excellent compatibility of refractory metals with the alkali metals, lithium, sodium, and potassium, under a variety of environmental conditions. The alkali metal compatibilities of tantalum-, columbium-, molybdenum-, and tungsten-base alloys are discussed.

Cb-1Zr pumped sodium loop tests to evaluate loop components, EM pump, pressure transducers, and instrumentation techniques

Tantalum and Ta alloys contamination rates in low pressure oxygen environment tests for use in space power systems

Both basic investigations and engineering experiments conducted for the most part during the last ten years have demonstrated that refractory metals generally have excellent compatibility with liquid metals. The temperature range of usefulness of the refractory metals begins at temperatures where conventional superalloys still have nominal mechanical strength but do not have the required resistance to corrosion by the liquid metals. The excellent compatibility of refractory metals with liquid metals can be degraded by impurity elements, and the controls required to assure compatibility will be presented.