Steam generators transfer the thermal energy generated in the reactor vessel of a PWR from the primary (reactor) cooling system to the secondary (turbine) cooling system, producing the steam to drive the electricity generation turbine. In French 900 MWe PWRs, the main primary circuit includes three steam generators.
Three new steam generators - each measuring about 21 metres in height, 4.5 metres in diameter and weighing some 330 tonnes - were delivered to the Cruas-Meysse site on 11, 18 and 24 January following a two-day journey. The components were manufactured by Framatome at its Saint-Marcel plant in Chalon-sur-Saône and were then transported 283 km by barge and 3 km by road. The journey had been carefully prepared since June last year.
A steam generator is unloaded from the barge (Image: Framatome)
The new steam generators will be installed in the reactor building of unit 3 in place of those that will be dismantled after 40 years of use. The new components will be re-welded to the hydraulic circuits of the plant before a comprehensive testing phase begins.
The old steam generators will be removed, taken out of the reactor building and stored in a specially constructed building on the site.
A steam generator being transported by road (Image: Framatome)
EDF noted that, over time, the thousands of tubes within the steam generators can become clogged, making heat exchange less efficient. It said the replacement of these components allows performance gains with 13% additional heat exchange surface due to the number of tubes being increased from 3460 to 4460.
Unit 3 at the Cruas-Meysse plant will be taken offline in August for a complete inspection that will last more than seven months, called a ten-year inspection. During the outage, the replacement of the steam generators will last about 100 days and will involve nearly 1000 workers.
Cruas-Meysse 3 is the first unit at the site to undergo its fourth ten-year inspection.
A ten-year inspection includes modifications, maintenance work, checks and tests on the installation with regard to the most recent safety standards and best national and international practices. It also constitutes a decisive step in obtaining the opinion of the Nuclear Safety Authority regarding the continued operation of the production unit for an additional ten years.
The steam generators of Cruas-Meysse units 4 and 1 took place in 2014 and 2017, respectively, while those of unit 2 are scheduled to be replaced in 2027.
