Due to the amount of nuclear waste packages already produced and expected to be produced, the secular duration of disposal operations in deep geological formation necessitates a progressive construction, pursuant to step by step development stages of the underground architecture and disposal areas. Building and operating underground disposal facility through an incremental development includes a temporal dimension, guided by a permanent, regular and careful sequencing of construction activities of the disposal facility over the operating period.

The current phase of final design allows the “injection” of optimizations in late 2016 and early 2017. Originally initiated by planning and costs improvement, these optimizations will be included in the reference design as soon as the possible advantages and disadvantages are evaluated according to operational and post-closure safety rules, construction, closure of underground structures, and reversibility.

Thus, an incremental development is a way for all the successive generations that will have to govern the disposal facility, to benefit from scientific knowledge and technological improvements and is an important part of reversibility.