In this group, there are isotope preparations that are made through the (n, p) nuclear reaction, followed by a decay mode causing a change in atomic number, and by the subsequent separation of the product from the irradiated target. Such products do not contain nonradioactive nucleus (carrier atoms), so their specific activity is high.
The I-131 radionuclide (see Table 8.11) can be listed in this group. Its typical production batch activity is around 740 GBq which—due to its high dose rate constant—needs thick shielding. Air exhausted from the production hot cell passes
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Table 8.10 Preparation of 35S-Labeled H2SO4
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Nuclear parameters
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Half-life: 87 days.
Decay mode and energy: в_ (keV) 167.
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Utilization
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General radioactive tracer with low 3_-energy.
Used for labeling, e. g., nucleotides in biochemical research.
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Target material
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Potassium chloride, KCl, with natural abundance of 35Cl (36%).
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Target irradiation
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In a research reactor with fast neutrons, for some months.
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Primary nuclear reaction
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35Cl(n, p)35S.
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Nuclear reactions resulting in contaminating nuclides
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33S(n, p)36P, 35Cl(n, Y)36Cl, 35Cl(n, a)32P.
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Target processing
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Dissolution in diluted hydrochloric acid.
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Radiochemical separation
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Adsorbing 36P, 36Cl, and 32P contaminating radionuclides on the alumina column. Elution of 35S from the column with diluted ammonium hydroxide. pH adjustment of the eluent with hydrochloric acid to 1.5.
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Purification of the product
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Passing the solution through Dowex cation — exchange resin to bind ammonium, aluminum, potassium, and other metallic ions. The resin is then washed with water. Dry evaporation of the eluent for eliminating HCl generated during ion exchange. Re-dissolution of the dry residue in water.
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Product finishing
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Adjustment of radioactive concentration, dispensing to the ordered number of ampoules.
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Other ways of production
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a. Starting from the 35Cl target, other chemical procedures are also used.
b. The 34S(n, Y)35S nuclear reaction with a low-activity yield.
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through a charcoal filter impregnated with iodine absorbent. Both the filter and the absorbent material will be handled later as radioactive waste.
In addition to the 131I radioisotope, there is another iodine radioisotope suitable for in vitro investigations; namely, 125I (see Table 8.12) which also has low X-ray and gamma energy. It is produced from Xe gas, and the typical batch size is around 370 GBq. Its low gamma energy does not require high shielding. Air exhausted from the production hot cell passes through a charcoal filter impregnated with iodine absorbent. (The third important iodine radioisotope, 123I, is a cyclotron product.)
