Welcome to the Glass Age

69 farm) by the coast and Figure 4.6 a giant wind turbine. Glass for nuclear waste disposal  More than 250,000 metric tons of high level radioactive wasteform (HLW) from nuclear power plants and weapons production facilities worldwide, are under storage in tanks such as seen in Figure 4.7. Even though a small fraction of total radioactive waste, it contains much of the radioactivity, posing great danger for society and a challenge to scientists and engineers. This wasteform is waiting to be converted into solids and then disposed of permanently in geological repositories. The solidified wasteform with radionuclides immobilized in a suitable matrix must remain stable against corrosion from groundwater for 1000 years, when the radioactivity would become comparable to acceptable ambient conditions. Three immobilization technologies, viz. cementation, bituminization and vitrification have been demonstrated to be commercially viable. Among them the highest degree of volume reduction and safety are demonstrated by vitrification although it is the most complex and expensive method. After considerable analysis of pros and cons of various choices, glass has appeared as the material of choice, and vitrification of HLW is currently being practiced in Belgium, France, Germany, India, Japan, Russia, UK and the USA. Glass is attractive to immobilize HLW waste through vitrification for the following reasons: • Strong capability to immobilize reliably a wide range of elements including radionuclides. • Relatively high loading of HLW thereby resulting in small volume to be disposed. • High chemical durability if and when the wasteform comes in contact with natural waters. • Desired properties have a high tolerance to radiation damage. • Well established production technology that can be adapted from glass manufacturing. Historically, borosilicate glasses were identified as potential hosts due to their high chemical durability, glass formability with HLW added as variety of oxides, and manufacturability. Subsequently, Russia focused also on sodium aluminophosphate glass as the HLW matrix. Overall, these glasses may contain more than 25 components. Such variations of composition, not to mention other test variables, have generated a plethora of data, making a comparison of relative performance very difficult. To overcome this challenge and establish a scientific basis for further developments, a six-component borosilicate glass known as the International Simple Glass (ISG) has been established by broad consensus to balance simplicity vs. similarity to waste glasses: 60.2SiO 2 -16.0B 2 O 3 -12.6Na 2 O- 3.8Al 2 O 3 -5.7CaO-1.7ZrO 2 (in mol%). Its basic properties and structure have been determined as a reference. In spite of considerable data generated on this and several other candidate glass compositions uncertainty remains about the assurance that overall a HLW package can maintain integrity over the lifetime of radioactivity under the highly interactive environment of radiation, temperature and groundwater. For example, new modes of corrosion of stainless steel have recently been identified at the interface with glass. Such enhancement of overall package degradation would require further optimization of individual components including glass. Glass for photobioreactors Photosynthesis by microalgae offers: an attractive approach to production of biomass rich in lipids and carbohydrates that can be used as a biofuel; CO 2 bio-fixation to reduce greenhouse gases; and treatment of wastewater to reduce