Measurement of excitation functions for the natMo(d,x)99Mo and natMo(p,x)99Mo reactions
Highlights
► Cross sections were measured using the stacked foil technique. ► Cross sections were measured for the natMo(d,x)99Mo and natMo(p,x)99Mo reactions. ► Thick target yields were determined for the natMo(d,x)99Mo reactions up to 59 MeV. ► Thick target yields were determined for the natMo(p,x)99Mo reactions up to 50 MeV.
Introduction
After recent nuclear reactor shut downs caused a shortage of the medical isotope 99mTc, alternative methods of production are being sought. 99mTc is one of the most widely used medical isotopes, and is currently produced by fission of highly enriched uranium in nuclear reactors (OECD-NEA, 2010). There is a large 6.1% fission yield for 99Mo, the parent isotope of 99mTc. One proposed alternative method of production is to use dedicated cyclotrons to produce 99Mo and 99mTc from natural or enriched molybdenum. Measurements are needed to determine the viability of cyclotron production.
This work looks at two possible reactions that can be used for the direct production of 99Mo: natMo(d,x)99Mo and natMo(p,x)99Mo. Natural molybdenum consists of seven stable isotopes, with 98Mo and 100Mo contributing to the deuteron reaction. Only 100Mo contributes to the proton reaction. The excitation functions for the two reactions described above were measured. For the deuteron reaction, the excitation function was measured over an energy range from 9.7 to 58.5 MeV. The proton reaction excitation function was measured over an energy range from 11.3 to 49.6 MeV. In addition to the excitation functions, the thick target yields for both reactions were determined by two methods. The first method, experimental determination, consisted of irradiating thick targets of molybdenum at different energies and measuring the 99Mo activity produced. The second method was numerical integration of the measured cross sections to obtain a thick target yield.
Section snippets
Target preparation
The stacked foil technique was used to measure the excitation functions. For the deuteron reactions, the targets consisted of alternating layers of molybdenum and aluminum foils. The molybdenum foils were 99.95% pure, of natural isotopic composition, and were either 25 or 102 μm thick. The aluminum foils were used as energy degraders, to stop the Mo recoils from contaminating subsequent Mo foils, and for beam monitoring. The thickness of the aluminum foils were 127, 229 or 305 μm. The thickness
Cross sections for natMo(d,x)99Mo
The cross section as a function of energy is shown in Fig. 3 along with previously published data and is summarized in Table 3. The uncertainty bars for the previously published data were removed for clarity. The data from Řanda and Svoboda (1977) was converted to natural composition using the isotopic abundances found in Řanda and Svoboda (1976). There is a good agreement with published results including the recently published results of Lebeda and Fikrle (2010). There is also a good agreement
Conclusion
New cross section data for the production of 99Mo from deuteron and proton bombardment on natural molybdenum were measured. The data extend the deuteron cross section data to 59 MeV and the proton cross section data to 50 MeV. There was a good agreement between our measured data and many of the previously published data sets. In addition, thick target yields were determined for proton and deuteron reactions on natural molybdenum. The measured thick target yields suggest that it is feasible to
Acknowledgments
This work was supported in part by the U.S. Department of Homeland Security, UC Berkeley, and by the U.S. Department of Energy under contract nos. DE-AC02-05CH11231 (LBNL) and W-7405-Eng-48 (LLNL).
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2016, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and AtomsCitation Excerpt :The yield is rather low for routine production of 99Mo on commercially available compact cyclotrons (81.4 GBq for Ein = 24.0 MeV, beam current 500 μA and irradiation time 6 h). The recent measurement of Chodash et al. (2011) [19] suggests that the cross-sections for the 100Mo(p,x)99Mo reactions are almost constant in the energy interval 25–50 MeV, i.e. large-scale production may be possible on highly enriched 100Mo using e.g. dedicated linear accelerators. Anyhow, in this case one must take into account that the product will have low specific activity.
Benchmark experiment for the cross section of the <sup>100</sup>Mo(p,2n)<sup>99m</sup>Tc and <sup>100</sup>Mo(p,pn)<sup>99</sup>Mo reactions
2016, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and AtomsCitation Excerpt :Several experimental and evaluated data-sets and evaluation are published for the activation cross sections of different reactions regarding the production of 99mTc and 99Mo radionuclides. Studies on measuring the cross sections of the 100Mo(p,2n)99mTc and 100Mo(p,pn)99Mo reactions as a function of the bombarding proton energy were carried out by many research groups with conflicting results regarding the amplitude of the reported data [1,7–23] by using both natural Mo and enriched 100Mo targets. Selected data-sets of the available cross sections for the 100Mo(p,2n)99mTc reaction are collected in Fig. 1 and for the 100Mo(p,pn)99Mo reaction in Fig. 2.