Two aluminum replicas of the fuel pins used in NRU reactor at CRNL for the production of molybdenum 99, a fission product from which technetium 99 is produced. The latter is widely used in medical diagnostics. The fuel pins are 19.6 cm long overall with the ribbed area being 16 cm in length. The diameter of the ribbed section is 1.3 cm. A split-diameter spacer ring that slides over the ends of the pins holds three vanes. These vanes allow cooling water to flow past the pins during irradiation while keeping the pins centered inside a 2 cm diameter tube.
