Flocculation is a common and inexpensive method for harvesting algae from solution. After nitrogen starvation, it was shown that 83 + 3% of the wall-deficient cells of the cw 15 mutant of Chlamydomonas reinhardtii flocculated from 12 mL samples within 15 min after the addition of 15 mM calcium chloride at pH 8.4. Only 24 2% of the wildtype strain flocculated under these conditions, thus demonstrating how a simple mutation might facilitate process design. The data suggested that algae grown in waters with similar calcium concentrations (e.g. certain wastewaters) might be harvested through simple pH adjustment. It was also discovered that the addition of small amounts (<5% v/v) of methanol could significantly reduce the calcium needed to achieve flocculation. Within 15 min after addition of 12 mM calcium chloride and 4.6% (v/v) methanol, 83 + 4% of cw15 cells flocculated. Methanol is fully recoverable by distillation, and its use might enable flocculation without further water salinization when media calcium concentrations fall short of 15 mM. It was further shown that substrates for and/or products of cellular growth affected flocculation adversely. Nearly 81% of cells flocculated from fresh medium compared to only 54% in spent medium.

No abstract

Evaluation of fuel debris properties in the Fukushima Daiichi nuclear power plant (1F) is required to develop fuel debris removal tools. In the removal of debris resulting from the Three Mile Island unit 2 (TMI-2) accident, a core-boring system played an important role. Considering the working principle of core boring, hardness, elastic modulus, and fracture toughness were found to be important fuel debris properties that profoundly influenced the performance of the boring machine. It is speculated that uranium and zirconium oxide solid solution (U,Zr)O2 is one of the major materials in the fuel debris from 1F. In addition, the Zr content of the fuel debris from 1F is expected to be higher than that of the debris from TMI-2 because the 1F reactors were boiling-water reactors. In this research, the mechanical properties of cubic (U,Zr)O2 samples containing 10%–65% ZrO2 are evaluated. The hardness, elastic modulus, and fracture toughness are measured by the Vickers test, ultrasonic pulse echo method, and indentation fracture method, respectively. In the case of (U,Zr)O2 samples containing less than 50% ZrO2, Vickers hardness and fracture toughness increased, and the elastic modulus decreased slightly with increasing ZrO2 content. Moreover, all of those values of the (U,Zr)O2 samples containing 65% ZrO2 increased slightly compared to (U,Zr)O2 samples containing 55% ZrO2. ZrO2 content affects fracture toughness significantly in the case of samples containing less than 10% ZrO2. Higher Zr content (exceeding 50%) has little effect on the mechanical properties.

No abstract

No abstract