Measurement of excitation functions for the natMo(d,x)99Mo and natMo(p,x)99Mo reactions

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Abstract

The excitation functions for proton and deuteron induced reactions on natural molybdenum for the production of 99Mo were measured. The proton induced reaction was measured in the energy range of 11.3–49.6 MeV, and the deuteron induced reaction was measured in the energy range of 9.7–58.5 MeV. Both beams were generated by the 88" cyclotron located at Lawrence Berkeley National Laboratory. The results are compared to previously published data. Thick target yields were obtained by direct measurement, in addition to being determined by integration of the measured cross sections.

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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