This three-part module focuses on the principles of nuclear fusion and on the likely nature and components of a controlled-fusion power reactor. The physical conditions for a net energy release from fusion and two approaches (magnetic and inertial confinement) which are being developed to achieve this goal are described. Safety issues associated with fusion reactors are discussed, and comparisons with other power sources are compared. Problems and discussion questions are suggested for a further exploration of these subjects. Topic areas addressed in section 1 include: fusion power; fusion/fission; fusion reactions; charged-particle repulsion; physical conditions required for the fusion process; minimum ignition temperature; and the Lawson criterion. Topic areas addressed in section 2 include: magnetic confinement--magnetic field and ion density; inertial confinement; motion of charged particles in a uniform magnetic field; magnetic confinement--particle paths; the Tokamak; and fusion reactor design. Topic areas addressed in the third section on safety and pollution of fusion reactors include: tritium; neutron activation; radiation damage; accidents; comparison with fusion-reactor hazards; and problems of scale and cost; also included are projects, questions, and suggestions for further reading and research. (JN)