  There has been growing clinical evidence of the value of targeted alpha
therapy for treatment of several cancers. The work has been slowed by the lack
of availability of the key alpha emitting isotopes, especially Ac-225. Until
this time, most of the supply has been from three Th-229 generators that are
milked to produce hundreds of mCi of Ac-225 every month. There has been a
growing effort to produce new sources of Ac-225 from several different
accelerator-based routes. It can be produced with medical-isotope cyclotrons
with a proton energy of at least 16 MeV using the reaction Ra-226(p,2n)Ac-225.
It can also be produced by using high-energy protons (150 to 800 MeV) for
spallation of a thorium target. Significant experimental work has been applied
to both processes. It can also be produced by the photonuclear reaction,
Ra-226({\gamma},n)Ra-225. The Ra-225 decays via beta decay to Ac-225 with a
half life of 14.9 days. The photons are produced by an intense beam of
electrons with an energy about 25 to 30 MeV. This paper will provide a
technical description of radium targets and a target chamber that would be
capable of producing a yield of four curies of Ra-225 from a 10-day irradiation
of one gram of radium segmented into two to four separate encapsulated targets,
at a beam power of 20 kW. These targets could be milked at least three times,
yielding nearly four curies of Ac-225. There is also a description of a method
to reduce production of Ac-227 to values less than a few parts per million of
the yield of Ac-225. The Monte Carlo code Fluka has been used to model the
yields of Ra-225 and support the design concept to reduce the production of
Ac-227. It has also been used to model the experimental results by Maslov et
al. [https://doi.org/10.1134/S1066362206020184] to provide reasonable
confidence in the cross-section value used by the code.
