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With 70 % of electrical production coming from nuclear sources (1986) France by far holds the world record. The Rhone-Alps Region is an outstanding example in point, accounting for over 30 % of French electric energy with three quarters of it from nuclear sources. Whether they are conventional or nuclear, the output of thermal or powerstations can hardly be modulated according to needs. Owing to its mountains, the Rhone-Alps Region has long held hydroelectric equipments allowing it to cope with peaks in consumption. The large range of this equipment represents a second original point. Recent or prospective developments in the Romanche basin show the evolutionary aspect of this policies of modulation : — the decision to create the pump storage station of Grandmaison has taken place in a such context as made the modulation of nuclear production appear as a remote goal ; — the Romanche-Isere plan in comparison looks rather as an alternative solution to the construction of one more powerstation in connection with the new patterns of consumers' behaviour in winter (electric heating) which are caused by the use of nuclear energy.

The creation of industrial and nuclear energy powerstation in the Rhone valley by CEA and EDF accounts for some rise in standards for the « communes » to a level roughly equal to that of county seats. Population growth, susceptible as it is to migratory balance has logical connection with the size of the installations and the steps in their development. Their financial well-being results from a legislation which keeps on attributing the major part of professional tax to the « communes » that are the seats of such installations. The urban development refers to two different original models : new residential areas of highrise buildings of old cities (CEA) or isolated suburban developments (EDF). The models are being questioned nowadays. Upon the whole, by sometimes giving rise to a genuing growth of tertiary activities, nuclear plants have been the cause of the swift blooming of proper towns.

In the Rhone-valley, the nuclear plants can deliver large amounts of hot or mild water. This water is used for the warming of horticultural green-houses. Two classical systems of very well-fitted « church-shaped » green-houses have been built in Bugey and Pierrelatte. The management of these erections is very expansive, so that farmers and collectivities involved suffer heavy financial problems. On the other hand more realistic and less expansive new projects have been developped in Bollene and Cruas-Meysse. Nevertheless this highly productive agricultural investments could after time give a good return.

Disregarding any nuclear accident, the most important ecological impacts of the nuclearisation of the Rhone's basin concern, at the moment, the landscape (in the « moyenne vallée du Rhône ») and the hydrobiological system (beginnings of deterioration immediatly downstream of the Bugey's site) ; the climatic and radioecological effects remain limited at the present time. However, we must emphazise : the synergy of some phenomena (interference of thermal pollution with organic pollution, and with hydromecanic effects of the dams) ; the short time perspective regarding the ecological inertia and the expected longevity of the nuclear power plants. Prudence and caution are therefore necessary, in a contentious context from both the informative and economical point of view.

The river Rhône, from Creys-Malville at Marcoule is accompanyed on his banks by a very great concentration of nuclear power-plants : six groups and a power of 15 000 MW. In this paper the author search answers at two facts. In first, what are the objective reasons of the geographical site which explains that concentration : the existence of a stream with an abundant and regular flow is fondamental, quasi unique. In second he tempts to appreciate in front of every type of powerplant and refrigeration what is the impact of those equipments on landscapes and specially in the morphology.