[en] A natural circulation, pool-type nuclear reactor, called SLOWPOKE-3, is being developed at the Chalk River Nuclear Laboratories. It is intended for producing 2 MW of hot water at atmospheric pressure for space heating and perhaps for generating some electricity. A simulation has been developed to investigate the rate-of-rise of reactor power and consequences of loss-of-regulation accidents during startup. The effects of fuel temperature and of coolant density on the rate-of-rise of reactor power were examined individually and in combination. The influence of different initial pool temperatures and input reactivity rates on startup transients was also investigated. The simulation is based on the point kinetic equations for neutrons and the conservation of mass, energy and momentum for the thermal-hydraulic circuit. The equations were solved digitally on CDC CYBER 175/6600 computers via the FORSIM computer program, developed at Chalk River Nuclear Laboratories