Two-step-pressurization method in pulsed electric current sintering of MoO₃ for production of ^99mTc radioactive isotope

Pulsed electric current sintering of molybdenum trioxide (MoO3) was carried out by one- and two-step pressurization methods for fabrication of irradiation targets used in the production of 99Mo and 99mTc nuclear medicines. At 550°C by the two-step pressurization method, a relative density of 93.1% was obtained while, by the one-step pressurization method, the relative density was 76.9%. Direct sample temperature measurements were conducted by a thermocouple inserted in a punch. By the two-step pressurization method, the sample temperature was higher than that by the one-step pressurization method even at almost the same die temperature. From voltage and current waveforms, it was indicated that the conductivity of the sample increased by the two-step pressurization method to increase the sample temperature and the relative density. The two-step pressurization method allows us to prepare dense targets at a low temperature from recycled and coarse-grained 98Mo enriched MoO3 powder.