⁹⁹Mo Production at KIPT Neutron Source Facility

Argonne National Laboratory (ANL) and Kharkov Institute of Physics and Technology (KIPT) have cooperated on the construction of the Neutron Source Facility (NSF) at KIPT, Kharkov (Ukraine). The NSF facility consists of an electron accelerator driven system (ADS) generating 300 kW of thermal power for multiple applications, including medical isotope production. ANL performed extensive analyses including medical isotopes production, reactivity monitoring, operations and control, refueling, cold neutron source design, target design,and radiation shielding. The present study focuses on the use of the KIPT NSF for medical isotope production. Medical isotopes are radioactive isotopes with short half-lives used in diagnostic and therapeutic medical procedures. For example, brain cancer is difficult to treat by ordinary surgery and only brachytherapy with ¹³¹Cs, which has 9.7 days half-life, has shown effective results on the patients. ^99mTc is the most common medical isotope used in medical diagnoses because the wavelength of its gamma radiation (8.8 pm) is about the same as the conventional X-ray diagnostic devices. ^99mTc has 6 hours half-life, therefore it cannot be stored because it decays into ⁹⁹Tc. The parent of ^99mTc is ⁹⁹Mo, which has 66 hours half-life. Consequently, the delivery of ^99mTc occurs through shipping ⁹⁹Mo samples to the medical facilities. The Neutron Source Facility of KIPT is the first ADS in the world operating at non-zero power and allows producing several isotopes for medical applications. The total power of the facility is about 300 kW, including ∼200 kW from fission reactions. The construction of the NSF has been already completed and operations will start during year 2016. After 20 irradiation days, ⁸²Br, ⁶⁴Cu, ¹⁶⁵Dy, ¹⁶⁶Ho, ¹⁹²Ir, ¹⁹⁴Ir, ¹⁸⁶Re, ¹⁸⁸Re and ¹⁵³Sm have specific activities, larger than 100 MBq/mg without taking into account the self-shielding effect and therefore they are good candidates for production. The self-shielding effect plays an important role for all nuclide parents that have a large microscopic capture cross section. This effect reduces the reaction rate and therefore the specific activity. For instance, the analyses of molybdenum trioxide (MoO₃) irradiation samples have shown that the self-shielding effect may reduce the specific activity by a factor 1.4. The metallic form of natural molybdenum produces a higher specific activity, relative to the trioxide form. Analyses on the 6-day Ci ⁹⁹Mo activity have shown that is possible to perform between 40 to 310 ^99mTc medical procedures per MoO₃ irradiation week. The number of medical procedures depends on the diagnosed organ and the weight of the patient. (authors)