Contents lists available at ScienceDirect Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso Developing a new target design for producing 99 Mo in a MTR reactor Ehsan Boustani a , Hassan Ranjbar b,* , Aref Rahimian a a Nuclear Science and Technology Research Institute (NSTRI), Reactor and Nuclear Safety School, 14399-51113, Tehran, Iran b Nuclear Science and Technology Research Institute (NSTRI), Material and Fuel Cycle School, 14399-51113, Tehran, Iran HIGHLIGHTS • An investigation is performed for producing more efficient of 99 Mo in Tehran research reactor. • Stochastic code MCNPX along with CFD code ANSYS are used to perform the calculations. • The proposed design satisfied all the neutronic, safety and operational constraints. • The new target gives rise to a higher production of 99 Mo enough for the local demand. • The proposed design causing a reduction in nuclear waste, process and operating difficulties. ARTICLE INFO Keywords: 99 Mo production Neutronic Thermal-hydraulic MCNPX ANSYS ABSTRACT 99 Mo is an important radioisotope and mainly produced using uranium fission reaction in a nuclear reactor. Investigation for probable improvements, especially on target geometry and in-core location of target is the main goal of this research. This is for producing more efficient of 99 Mo in a typical Material Testing Reactors (MTRs). A parametric investigation is done focused on the target characteristics such as geometry, location, material, density, heat flux (power density) and also usability in Tehran Research Reactor (TRR) as a MTR case study. Stochastic code MCNPX 2.6.0 along with CFD code ANSYS are used to perform neutronic and thermal-hydraulic analyses. A target with plate type design is specified and proposed as a final and most favorable design. Taking into account the safety criteria, the production yield, the chemical process and radioactive waste, it is demon- strated that the new target design meets the key design requirements without compromising the reactor safety. This research results indicate that the new target gives rise to a higher production of 99 Mo using less amount of initial material causing to a reduction in nuclear waste and process difficulties. 1. Introduction The importance of 99 Mo is for its daughter, 99m Tc. This radioisotope with acceptable properties is suitable for being used widely for detec- tion studies in nuclear medicine (Chechev and Bé, 2014). 99m Tc with its half-life of 6.02 h has numerous applications in nuclear medicine (Badwar et al., 2017; Capogni et al., 2017). About 80% of diagnostic imaging procedures in nuclear medicine use this isotope, 10% with 18 F and the remaining 10% with the other radioisotopes (Lyra et al., 2011; Phillips et al., 2016; Liu et al., 2017). The great tendency reasons for use of 99m Tc are its low price, small amount of absorbed dose in noncritical organs and the high resolution of given images in the light of this radioisotope (IAEA, 2008; Tymiński et al., 2017). Throughout the world, the amount of 99 Mo needs are more than 30 million cases per year-nearly 500 6-days kCi (Charlton, 2016; National Academies of Sciences and Medicine, 2016). Nowadays, the amount of the consumed 99 Mo in Iran is more than 100 6-days Ci and there is an increasing demand for it. Many methods for 99 Mo production are not affordable and used only for research or special cases. The present gold standard process for producing 99 Mo for medical purposes is uranium fission in reactor. = Unf σ barns (, ) 570 th 235 (1) More than 95% of 99 Mo/ 99m Tc generators are provided using 235 U nucleus fission. In this method, the resulted molybdenum from fission in uranium target is used for 99 Mo production. These targets are irra- diated in reactor, interact with the thermal neutrons and produce fis- sion fragments with fission yield of 6% for 99 Mo. The irradiated targets which contain many fission products are https://doi.org/10.1016/j.apradiso.2019.03.006 Received 4 January 2018; Received in revised form 19 December 2018; Accepted 4 March 2019 * Corresponding author. E-mail address: hranjbar@aeoi.org.ir (H. Ranjbar). Applied Radiation and Isotopes 147 (2019) 121–128 Available online 07 March 2019 0969-8043/ © 2019 Elsevier Ltd. All rights reserved. T