  PROCESS is a reactor systems code - it assesses the engineering and economic
viability of a hypothetical fusion power station using simple models of all
parts of a reactor system. PROCESS allows the user to choose which constraints
to impose and which to ignore, so when evaluating the results it is vital to
study the list of constraints used. New algorithms submitted by collaborators
can be incorporated - for example safety, first wall erosion, and fatigue life
will be crucial and are not yet taken into account. This paper describes
algorithms relating to the engineering aspects of the plant. The toroidal field
(TF) coils and the central solenoid are assumed by default to be wound from
niobium-tin superconductor with the same properties as the ITER conductors. The
winding temperature and induced voltage during a quench provide a limit on the
current density in the TF coils. Upper limits are placed on the stresses in the
structural materials of the TF coil, using a simple two-layer model of the
inboard leg of the coil. The thermal efficiency of the plant can be estimated
using the maximum coolant temperature, and the capacity factor is derived from
estimates of the planned and unplanned downtime, and the duty cycle if the
reactor is pulsed. An example of a pulsed power plant is given.
