## 2 Survey of Commercial Use of Radioactive Isotopes
### Mo  
The \({}^{99}\)Tc (T\({}_{1/2}\) = 6.01 h) isotope was discovered in 1938 from the radioactive decay of \({}^{99}\)Mo (T\({}_{1/2}\) = 65.94 h), and now it is the most widely used isotope tracer for SPECT (single-photon emission computed tomography) imaging. The world's capacity of such procedures is estimated to be \(\sim\)40 million screenings annually, which is roughly 80% of all treatments involving nuclear radiation [5]. The \({}^{99}\)Mo market is assessed to be as big as USD 5 billion yearly, with a forecasted increase of \(\sim\)9% per year. Over the decades, there have been significant investments in the \({}^{99}\)Mo production, and the need for additional \({}^{99}\)Mo capacity grows continually. A so-called six-day activity is a special unit applied for the \({}^{99}\)Mo production that usually means the activity after 6 days of the processing time. The present \({}^{99}\)Mo world demand of about 18,500 six-day TBq/year [5] is covered mainly by six reactors: HFR (Petten, The Netherlands) \(\sim\)40%, BR-2 (Mol, Belgium) \(\sim\)20%, Safary-1 in South Africa \(\sim\)15%, the Australian Opal \(\sim\)15%, Maria (Swierk, Poland) \(\sim\)5%, and the reactor LWR-15 in the Czech Republic \(\sim\)5%. There is an assessment of the \({}^{99}\)Mo market size: the Opal annual production (15% of the market) is around 81.4 six-day TBq/week (2200 six-day Ci/week). Due to natural decay of \({}^{99}\)Mo during shipping, storage, and processing, the world's supply capability should, and does, significantly exceed the market consumption by up to 50% [5]. The \({}^{99}\)Mo can be generated by an exposure to neutron irradiation of either natural molybdenum, metal, and MoO\({}_{3}\), or of the enriched \({}^{98}\)Mo through the \({}^{98}\)Mo(n,\(\gamma\))\({}^{99}\)Mo reaction. The generated specific activity is usually lower compared to the \({}^{99}\)Mo produced in research reactors utilizing targets filled with enriched uranium. The typical yield (a reference value used for the comparison in this work) of \({}^{99}\)Mo at the end of 1 week of irradiation is \(\sim\)1.2 \(\times\) 10\({}^{10}\) Bq/g [6,7]. In the case of the production in fission reactors, the activity of the \({}^{99}\)Mo is \(\sim\)4.0 \(\times\) 10\({}^{14}\) Bq/g [7] at the end of \(\sim\)200 h of irradiation. The cost for the \({}^{99}\)Mo production in early 2008 varied from USD 3380 to 8780/TBq (USD 125 to 325/Ci) [8]. The estimated present market value of \({}^{99}\)Mo could be USD 6760-17,570/TBq (USD 250-650/Ci). \({}^{192}\)Ir  
Iridium radioactive sources (T\({}_{1/2}\) = 73.83 days) are usually delivered in the form of thin wires or thin foil discs. The specific activity of the \({}^{192}\)Ir enables the preparation of very small, miniaturized radioactive sources for their utilization in vitro in the human body. Such implants typically require an exchange several times per year [9]. Because of the strong beta emission, this procedure, brachytherapy, is very effective at providing intensive local irradiation, for example, in the head and breast. \({}^{192}\)Ir also has applications in industrial radiography to check pipeline welds and to assess the structure of steels and various alloys. \({}^{192}\)Ir sources are typically produced by the neutron irradiation exposure of natural iridium through the \({}^{191}\)Ir(n,\(\gamma\))\({}^{192}\)Ir reaction. The target material, 10 mg of Na\({}_{2}\)IrCl\({}_{6}\), is sealed in aluminum capsules of 22 mm diameter and 44-50 mm length for 1 week [6; 10]. The typical yield of the \({}^{192}\)Ir after irradiation is approximately 68 GBq/g [6]. The total annual world demand exceeds 30,000 Ci (measured at the end of the irradiation). The price for \({}^{192}\)Ir radioactive sources varies significantly in the range USD 12,160-27,000/TBq (USD 450-1000/Ci) [11; 12].