Design and development of a device for the opening of irradiated aluminum capsules in the IPEN IEA-R1 nuclear reactor

Abstract

The production of radionuclides in nuclear research reactors is an important activity of national nuclear energy programs. Numerous radionuclides produced include molybdenum-99, iodine-131 and phosphorus-32, widely used in medical procedures. Radionuclides are produced by exposing the target material to a neutron flux in one of the irradiation positions in the core of the nuclear reactor. Before irradiation, the target materials must be contained in sealed capsules, preventing the release of radionuclides that contaminate the nuclear reactor installation. The capsules used in the Nuclear and Energy Research Institute (IPEN) IEA-R1 nuclear reactor are made of aluminum, taking advantage of the following characteristics: low cross section for neutron absorption, radionuclide production from the aluminum alloy of short half-life, good thermal conductivity and possibility of cold sealing of the capsule. This work proposes a new device for opening irradiated aluminum capsules (rabbits), with implement of a better procedure, focusing on operator safety. Ensuring safety during all stages and processes is a preponderant factor when it comes to radioactive materials. The following main deficiencies are identified about the current opening procedure: a) radioactive debris generated by the cutting contaminate the environment of manipulation, increasing the risks of exposure to radiation and the care with the collect and disposal of these debris; b) rotation movement of the capsule during opening may cause damage to the target material and its casing, leading release of radioactive target materials. The new opening device: a) uses the least possible electronic components based on integrated semiconductor circuits, susceptible to radiation; b) contemplates that the insertion and removal of the capsules will be done by telemanipulators; c) modifies the type of cutting performed, from abrasive to cutting wheel blade, allowing minimal generation of small size radioactive debris; d) replaces the rotation of the capsule by a movement in the cutting head, keeping the capsule still, thus reducing the risk of damage to the samples; e) provides greater control, process accuracy and emergency stop, through improved remote operating system. Results of comparative tests showed that the current system produces average 0.3(2) mg of debris per cut, while the proposed system of cutting wheel blade presented a reduction of more than 99 % in the generation of debris. In addition, the immobilization of capsule during the open prevents damage to the radioactive target materials.