PROCESS

During the course of studies into a proposed fusion power plant, there may be times when questions of the following type arise:

• Are the machine’s physics and engineering parameters consistent with one another?
• Which machine of a given size and shape produces the cheapest electricity?
• What is the effect of a more optimistic limit on the maximum plasma density on the amount of auxiliary power required?

Questions such as these are extremely difficult to answer, since the large number of parameters involved are highly dependent on one another. Fortunately, computer programs have been written to address these issues, and PROCESS is one of them.

Suppose that an outline power plant design calls for a machine with a given size and shape, which will produce a certain net electric power. There may be a vast number of different conceptual machines that satisfy the problem as stated so far, and PROCESS can be used in “non-optimisation” mode to find one of these whose physics and engineering parameters are self-consistent. However, the machine found by PROCESS in this manner may not be possible to build in practice — the coils may be overstressed, for instance, or the plasma pressure may exceed the maximum possible value. PROCESS contains a large number of constraints to prevent the code from finding a machine with such problems, and running the code in so-called “optimisation” mode forces these constraints to be met. The number of possible conceptual machines is thus considerably reduced, and optimisation of the parameters with respect to (say) the cost of electricity will reduce this number to a minimum (possibly one).

Formally then, PROCESS is a systems code that calculates in a self-consistent manner the parameters of a fusion power plant with a specified performance, ensuring that its operating limits are not violated, and with the option to optimise a given function of these parameters.