Rhenium remediation in the preparation of molybdenum-99

A method of removing rhenium from a particulate rhenium (Re) oxide-containing MoO3 matrix that contains one, the other or both of Mo-98 and Mo-100 isotopes that comprises the steps of:

• a) heating said particulate rhenium oxide-containing MoO3 matrix in the presence of an oxygen-rich gaseous stream (oxidative rich sparging) to a temperature of greater than about 300° C. and less than about 800° C.;
• b) maintaining the temperature and oxidative rich sparging for a time sufficient to form rhenium (VII) [Re (VII)] oxide and to vaporizingly remove said Re (VII) oxide to form a remediated MoO3 matrix that contains an amount of less than about 1000 parts per trillion of rhenium, while losing to vaporization less than about 0.2 percent of the molybdenum present in the MoO3 matrix;
• c) interrupting said heating and oxidative sparging of step b) after a time period of about 8 to about 20 hours;
• d) permitting the heated matrix to cool to a temperature at which the matrix can be handled;
• and
• e) comminuting the matrix, mixing the resulting comminuted matrix, and returning the mixed comminuted matrix to heating and oxidative sparging for a further time period of about 8 to about 20 hours.