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A FTIR based method was developed for in-situ monitoring the gas phase chemistry in the reaction chamber of technological scale CVI/CVD reactors. Using methyltrichlorosilane (MTS) as SiC precursor, several gaseous species could be detected including MTS, SiCl2, (SiCl3)n=1,2, SiCl4, HSiCl3, CH4, CH3Cl and HCl which, consequently, can be monitored simultaneously. First attempts have been established for derivinp arbitrary and absolute concentrations of species from emission spectra. The determined composition of the reaction mixture supports recent theoretical results of kinetic rnodelling. Using the established technique, several runs have been monitored within the SiC-CVI/CVD reactor at different stages of deposition. Unexspectedly strong variations of concentrations of most of the gaseous species have been detected whose reason is not fully clear yet. These technique will be a key element in establishing a closed loop process control

This research project involved working on the pressure resistance welding of oxide dispersion strengthened (ODS) alloys which will have a large role to play in advanced nuclear reactors. The project also demonstrated the research collaboration between four universities and one national laboratory (Idaho National Laboratory) with participation from an industry for developing for ODS alloys. These alloys contain a high number density of very fine oxide particles that can impart high temperature strength and radiation damage resistance suitable for in-core applications in advanced reactors. The conventional fusion welding techniques tend to produce porosity-laden microstructure in the weld region and lead to the agglomeration and non-uniform distribution of the needed oxide particles. That is why two solid state welding methodspressure resistance welding (PRW) and friction stir welding (FSW)-were chosen to be evaluated in this project. The proposal is expected to support the development of Advanced Burner Reactors (ABR) under the GNEP program (now incorporated in Fuel Cycle R&D program). The outcomes of the concluded research include training of graduate and undergraduate students and get them interested in nuclear related research. The primary research components of the proposal were the following: PRW and FSW were applied to two mechanically alloyed (MA) ODS alloys. The process optimization was carried out to get to a process window that worked for the alloys. Microstructures and mechanical properties of the as received and welded materials were characterized using a number of advanced characterization tools (SEM/EDS/EBSD and TEM). Mechanical properties were evaluated using microhardness, tensile testing, crack growth tests under fatigue loading and burst testing. The as received and friction stir welded alloys were irradiated in the Advanced Test Reactor (ATR). The samples are still being evaluated due to some schedule delay. Overall, the project highlighted that the use of solid state welding techniques can open up new opportunities in nuclear reactor applications, and the high performance alloys like ODS alloys would require these techniques in order to retain their best properties. These welding techniques can be developed as an 'enabling technology' in nuclear applications.