[en] HIFAR (High Flux Australian Reactor) is a heavy water moderated and cooled, materials testing and research reactor producing a maximum thermal neutron flux of 10¹⁴ neutrons per square centimeter per second at a heat output of 10 megawatts. It is one of six similar research reactors designed in the United Kingdom in the 1950s and known as the DIDO class. HIFAR operates on a 28-day cycle - 24 days working and four days shutdown to carry out routine maintenance, check safety mechanisms and load fresh fuel. Rigorous maintenance, upgrading and refurbishment have been the key to keeping HIFAR in top condition. Another important factor has been the regular and very carefully implemented longer shutdowns for major maintenance and upgrading work. Top priorities for the 1991 extended shutdown summarized in this issue include: upgrading the total heavy water inventory, inspecting and cleaning the reactor main tank, installing three new collimators for neutron beam experiments and improving facilities for transmutation doped silicon production. The program also included improving the reactor's capabilities in neutron beam research and neutron transmutation doped silicon production. Further tasks carried out were cleaning and repair of main heat exchanger mesh screens and cleaning and painting the reactor plant room floor. Inspections performed in the 1991 have provided a much clearer picture of the condition of the reactor which have been under routine operation for 32 years. This work was aided greatly by remote camera surveillance techniques which have been refined and upgraded in the period since the last major shutdown. Live testing of the emergency core cooling system confirmed the efficacy of new developments in the emergency cooling. ills