PURNIMA, a PuO2-fueled copper-reflected zero-energy fast reactor at Trombay, was built as a mockup of the proposed air-cooled 30-kW Kalpakkam Pulsed Fast Reactor. This paper describes the salient features of PURNIMA and discusses the calculational methods used and the control philosophy and operational procedures adopted. Important aspects relating to the overall safety are examined in detail. Some of the experiments carried out with this facility are also briefly reported.