Estimation and measurement of MO⁹⁹ activity in natural molybdenum metal and oxide sample irradiated in Dhruva

Technetium-99m is a widely used medical radioisotope due to its soft gammas (140 KeV) and relatively short half life of 6 hrs. It is formed as a daughter product of molybdenum-99 (⁹⁹Mo). Because of its short half life (t_1/2 ∼ 65.94 hrs), ⁹⁹Mo cannot be stored for long and hence a continuous supply of ⁹⁹Mo/Tc^99m is required for its effective utilization. Like other radioisotopes, ⁹⁹Mo is produced by irradiating natural molybdenum in Dhruva. We have carried out detailed theoretical analyses for estimation of ⁹⁹Mo activity due to neutron irradiation of natural molybdenum. The á 'shape factor' of real, non-ideal 1/(E)^1+á epithermal neutron spectrum in an isotropic neutron field of tray rod location in Dhruva reactor has been estimated using Monte Carlo Method and Dragon Lattice code. Based on the estimated á factor, infinite dilution resonance integral has been modified. The results are validated by experimental irradiation of molybdenum samples in metal and oxide forms in research reactor Dhruva. The present report gives details of the methodology for calculations, experimental irradiation and measurement of activity. Finally, results of estimations and measurements are presented. (author)