high to be competitive with a reactor. The cost of construction and operation of multiple machines would have to be analyzed to determine if a business case could be made for these approaches.

Another approach is photo-fission of U-238 using natural or depleted uranium targets. The challenge is the same as is mentioned for the other photon induced reaction (100Mo(γ,n)99Mo); that is, the need for a very high intensity beam to overcome the factor of about 1000 smaller cross section for this reaction versus neutron fission of U-235, although the fission yields are almost identical (approximately 6 percent).

The other option that has been explored is the direct production of Tc-99m from the 100Mo(p,2n)99mTc. The biggest disadvantage with this approach is that the final product (the one used in nuclear medicine procedures) is directly produced and has a short half-life (6 hours). Thus, its usefulness would be greatly hampered if it needed to be shipped great distances to the end users. Even a network of suppliers would face a challenge. Takács et al. (2002) report that the cross section for the direct production of Tc-99m from enriched Mo-99 would be approximately 17 mCi/μAh. At this level even a very high beam current facility (500μA protons) and irradiation periods of a day (i.e., 24 hours), the most that could be produced in a single facility would be < 200 Ci per day. To meet the needs of the United States there would have to be more than 25 cyclotrons dedicated to this process. This does not take into account the losses associated with transport and chemical efficiencies for separating the Tc-99m from the target matrix. A single site might be able to become self-sufficient but this would not help the larger community.

Takács et al. (2002, 2003) explored the production of Mo-99 from the 100Mo(p,pn)99Mo reaction. Their results indicated a thick target yield (40–45 MeV) of 3.8 mCi/μAh. The daily production for a similar cyclotron would be about 50 Ci thus about 100 cyclotrons would be required for this approach.

The other approach would be through the spallation (high-energy projectile collides with the target nucleus with enough energy that a very large array of products is produced) of a target to produce Mo-99. The production rate of Mo-99 from most reasonable target materials would be at best many orders of magnitude lower than the reactor methods and two orders of magnitude lower than the above accelerator reactions and thus not a viable approach.

From this analysis there are few viable alternative approaches to the supply of Mo-99 or Tc-99m for widespread distribution. With the termination of the Maple reactor project, alternative approaches need to be explored in comparison to the cost of constructing and commissioning a new reactor facility, especially with photon-induced fission with U-238.



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