A feasibility study on photo-production of 99mTc with the nuclear resonance fluorescence

Abstract

This paper presents a feasibility study for producing the medical isotope 99mTc using the hazardous and currently wasted radioisotope 99Tc. This can be achieved with the nuclear resonance fluorescence (NRF) phenomenon, which has recently been made applicable due to high-intensity laser Compton scattering (LCS) photons. In this work, 21 NRF energy states of 99Tc have been identified as potential contributors to the photo-production of 99mTc and their NRF cross-sections are evaluated by using the single particle estimate model and the ENSDF data library. The evaluated cross sections are scaled using known measurement data for improved accuracy. The maximum LCS photon energy is adjusted in a way to cover all the significant excited states that may contribute to 99mTc generation. An energy recovery LINAC system is considered as the LCS photon source and the LCS gamma spectrum is optimized by adjusting the electron energy to maximize 99mTc photo-production. The NRF reaction rate for 99mTc is first optimized without considering the photon attenuations such as photo-atomic interactions and self-shielding due to the NRF resonance itself. The change in energy spectrum and intensity due to the photo-atomic reactions has been quantified using the MCNP6 code and then the NRF self-shielding effect was considered to obtain the spectrums that include all the attenuation factors. Simulations show that when a 99Tc target is irradiated at an intensity of the order 1017 γ/s for 30 h, 2.01 Ci of 99mTc can be produced. Keywords: Laser-Compton scattering (LCS), Nuclear resonance fluorescence (NRF), Tc-99 m, Energy recovery LINAC, Photo-production