Development of Mullite Based Refractory Pot for High Lead Containing Glass Melting

Radiation shielding window (RSW) glass for nuclear reactor is primarily required for protecting the operating personnel from harmful radioactive rays produced during nuclear energy generation in nuclear hot cells. In this respect, the production of high lead (>70% PbO) containing RSW glass is generally made using platinum pot through bottom pouring flow casting technique. However, owing to low capacity (40 L max.) of high cost platinum pot, the production of glass slab is limited to a maximum dimension of 400x400x100 mm(3). Therefore, an alternate cost effective technology is highly required for making higher dimension glass slabs. To fulfill the requirement, low cost and higher volume refractory pot based tilt casting technology can be adopted. In this regard, the refractory pot is to be developed with adequate thermal, chemical and mechanical stabilities towards sustaining high corrosive lead oxide containing molten glass at 1100 degrees-1200 degrees C. For this purpose, a clay based alumino-silicate pot material enriched with mullite has been developed and characterized systematically. The rectangular bars have been fabricated by slip casting technique and the fabricated bars have been fired between 1450 degrees and 1550 degrees C. The fired materials have been characterized in terms of bulk density, apparent porosity, cold and hot modulus of rupture, etc. The RSW glass with more than 70% lead oxide content has successfully been melted in the pot. The quality of RSW glass produced using the pot has also been studied. In an optimized composition of the pot, the formation of higher content of mullite phase having high thermal shock and corrosion resistance with the desired mechanical stability is the key factor behind the stability of the refractory pot for making defect free RSW glass slabs. This cost effective refractory pot technology can substitute the platinum pot technology for producing larger dimension RSW glass slabs