Optimization of irradiation conditions for 177Lu production at the LVR-15 research reactor

The use of lutetium in medicine has been increasing over the last few years. The 177Lu radionuclide is commercially available for research and test purposes as a diagnostic and radiotherapy agent in the treatment of several malignant tumours. The yield of 177Lu from the 176Lu(n,γ)177Lu nuclear reaction depends significantly on the thermal neutron fluence rate. The capture cross-sections of both reaction 176Lu(n,γ)177Lu and reaction 177Lu(n,γ)178Lu are very high. Therefore a burn-up of target and product nuclides should be taken into account when calculating 177Lu activity. The maximum irradiation time, when the activity of the 177Lu radionuclide begins to decline, was found for different fluence rates. Two vertical irradiation channels at the LVR-15 nuclear research reactor were compared in order to choose the channel with better irradiation conditions, such as a higher thermal neutron fluence rate in the irradiation volume. In this experiment, lutetium was irradiated in a titanium capsule. The influence of the Ti capsule on the neutron spectrum was monitored using activation detectors. The choice of detectors was based on requirements for irradiation time and accurate determination of thermal neutrons. The following activation detectors were selected for measurement of the neutron spectrum: Ti, Fe, Ni, Co, Ag and W. (authors)