22.08.2015   Nuclear and Radiochemistry

Isotope Preparations Generated with Fast Neutron Irradiation

Isotope preparations that are produced through the (n, p) nuclear reaction generated by epithermal or fast neutrons belong to this group. These nuclear reactions change the atomic number of the target element; for this reason, the product must be sepa­rated from the target by radiochemical methods. Such products do not contain non­radioactive nucleus (carrier atoms), so their specific activity is high, which is very beneficial for tracer reactions.

Phosphorus is a basic element of some fertilizers, so the 32P radionuclide (see in Table 8.9) plays an important role in agrochemical and related studies. At the same time, it is also frequently used in industrial tracer investigations for studying corro­sion inhibitors.

Typical production batch activity for 32P is around 740 GBq. Due to its rela­tively long half-life, this radionuclide can be dispensed for applications for weeks.

The details of the production of sulfur-35 isotope are given in Table 8.10. The typical production batch is 370 GBq. Due to its relatively long half-life, the product can be dispensed for utilization during periods of months.

Table 8.9 Preparation of 32P-Labeled H3PO4

Nuclear parameters

Half-life: 14 days.

Decay mode and energy: [3_ (keV) 1710.

Utilization

General radioactive tracer with high [3_ energy.

Used for labeling, e. g., nucleotides in biochemical research.

Target material

Elementary sulfur, 32S with natural abundance (95%).

Target irradiation

In a research reactor with fast neutrons, for some months.

Primary nuclear reaction

32S(n, p)32P.

Nuclear reactions resulting in contaminating nuclides

34S(n, Y)35S, 33S(n, p)33P.

Target processing

Elementary sulfur is irradiated in molten form, followed by dissolution in tetrachloroethylene (TCE) under reflux and heating.

Radiochemical separation

Separation of the generated 32P from the irradiated sulfur is made by extraction with water under reflux and heating.

Separation of phases

Made in a separation funnel by adding diluted

hydrochloric acid to the water phase until reaching a pH of 1-1.5.

Purification of the product

Ion exchange on Dowex cation — and anion-exchange resin for the removal of sulfuric acid (generated at the irradiation) and that of metal ions. Elution with diluted hydrochloric acid. Adjusting pH to 3-6.

Product finishing

Adjustment of radioactive concentration, dispensing to the ordered number of ampoules.

Other ways of production

a. Distillation or coprecipitation made with magnesium hydroxide is also used for separation.

b. The nuclear reaction 31P(n, Y)32P provides a lower activity yield.

Production of the P-33 radionuclide (for medical use) also belongs to this group. It is made from the S-33 target through the (n, p) nuclear reaction (see Section 8.6).