Optimal parameters to produce 131I by neutron irradiation and melting of sintered tellurium dioxide

High purity TeO2 was produced by adding 125 ml of 6N HNO3 to 50 g of metallic tellurium (Merck No. 8100) and heating to 330°C till dryness in presence of an air flow. Released vapors of NO2 are dissolved in 3 connected closed water containers. TeO2 is sintered in quartz tube put in an oven and heating gradually to 700°C and then for 5 min at this temperature. The sintered TeO2 is a suitable target to be irradiated with thermal neutrons and induce the nuclear reactions: 130Te(n,γ) 131mTe (t1/2=30 h) and 130Te(n,γ) 131Te (t1/2=24.8 m) for and irradiation time of 24 h. After a cooling time of 48 h, the radioactive source is put in a small electric oven enclosed in an airtight box where a negative pressure is kept along the experiment (0.5 cm of water). There it is heated gradually till melting (733°C). From 400°C on the vapors from the oven are pumped out and bubbled in 2 solutions. First one is 0.1 M NaOH. Second one is 0.02 M Na2CO3 plus 2.5×10−3 M NaHCO3 (40%). Before being released, vapors bubbled in the solution passed an activated carbon filter. The first solution (0.1 M NaOH) catches 99.9% of 131I activity pumped out (about 300 m Ci for 1.5 h of pumping). This solution is diluted and the pH value fixed at suitable value (7–9) before being distributed for its use. The residual activity remains in the second solution and the activated carbon filter.