No abstract

This paper investigates the feasibility of using aluminum sludge (AS) to enhance copper mine tailings (MT)-based geopolymer. The Si/Al and Na/Al molar ratios were adjusted by adding AS into the high silica content MT and using different amounts of NaOH. Unconfined compression tests and SEM, XRD, and FTIR studies were conducted on geopolymer specimens prepared at different Si/Al and Na/Al ratios and after 7-day curing. The results indicate that by adding AS and utilizing appropriate amount of NaOH, the unconfined compressive strength increases significantly. The main reason is because the addition of AS along with utilization of appropriate amount of NaOH makes both the Si/Al and Na/Al ratios reach the optimum values for geopolymerization, leading to higher degree of geopolymerization and more compact geopolymer microstructure. Based on this study, it can be concluded that AS can be used to effectively enhance the MTbased geopolymer.

A modified tritium trick technique was used to implant three different levels of 3 He in V-15Cr-5Ti (wt %) and Vanstar-7 specimens before irradiation in the Fast Flux Test Facility (FFTF). The modifications include: (1) wrapping of the specimans with tantalum foil to minimize oxygen contamination, and (2) a 400°C decay-time treatment to prevent vanadium tritide formation and to produce a 3 He bubble distribution similar to that produced during elevated temperature irradiation.Preliminary results show that both modifications were successful.However, the tritium removal step at 700°C was probably too excessive, especially at higher helium levels, because large 3 He bubbles formed in the grain boundaries and severely embrittled the V-15Cr-5Ti alloy.Reduction of the tritium removal step to 400°C should alleviate thi problem. Vanstar-7 specimens consistently absorbed about half as much tritium, and subsequently contained half as much 3 He as V-15Cr-5Ti.Implanting 3 He in vanadium alloys via the tritium trick offers a convenient technique to study the mechanism of helium embrittlemert without irradiation and should provide a rapid screening method to help develop embrittlement-resistant vanadium alloys.

Gadolinium-153 production at the Oak Ridge National Laboratory (ORNL) involves the neutron irradiation of natural europium oxide (47.8% ^-^Eu, 52.2% 153E U)_ Yhj s target material undergoes a series of neutron captures and radioactive decays to produce the desired l^Gd product. Several undesirable europium isotopes (l^Eu, 154^U) anc j 156^uj are a-] s o produced during this irradiation process. Recent technical advances and other improvements in the radiochemical processing of this isotope have allowed ORNL to increase production by more than sevenfold. A newly developed electrochemical process has allowed the separation of the bulk of undesirable europium isotopes and has also affected a more efficient use of high-pressure ion exchange to achieve a final product radiochemical purity >99.999%. Specific activities >60 Ci/g of gadolinium oxide and product specific yields >2.9 Ci/g of irradiated europium oxide have been produced. Use of unique glove box manipulators and special equipment designed at ORNL have allowed final source fabrication to keep pace with the increased production rate while minimizing the radiation exposure to operating personnel.