Modelling the effects of nuclear fuel reservoir operation in a competitive electricity market

In many countries, the electricity systems are quitting the vertically integrated monopoly
organization for an operation framed by competitive markets. In such a competitive regime one
can ask what the optimal management of the nuclear generation set is. We place ourselves in a
medium-term horizon of the management in order to take into account the seasonal variation
of the demand level between winter (high demand) and summer (low demand). A flexible
nuclear set is operated to follow a part of the demand variations. In this context, nuclear fuel
stock can be analyzed like a reservoir since nuclear plants stop periodically (every 12 or 18
months) to reload their fuel. The operation of the reservoir allows different profiles of nuclear
fuel uses during the different seasons of the year. We analyze it within a general deterministic
dynamic framework with two types of generation: nuclear and non-nuclear thermal. We study
the optimal management of the production in a perfectly competitive market. Then, we build
a very simple numerical model (based on data from the French market) with nuclear plants
being not operated strictly as base load power plants but within a flexible dispatch frame (like
the French nuclear set).
Our simulations explain why we must anticipate future demand to manage the current
production of the nuclear set (myopia can not be total). Moreover, it is necessary in order to
ensure the equilibrium supply-demand, to take into account the non-nuclear thermal capacities
in the management of the nuclear set. They also suggest that non-nuclear thermal could stay
marginal during most of the year including the months of low demand.