[Context and motivation] Regulatory requirements for Nuclear instrumentation and control (I&C) systems are first class requirements. They are written by national safety entities and are completed through a large documentation set of national recommendation guidesandnational/internationalstandards. [Question/Problem] I&C systems important to safety must comply to all of these requirements. The global knowledge of this domain is scattered through these different documents and not formalized. Its organization and traceability relationships within this domain is mainly implicit. As a consequence, such long lasting nuclear I&C projects set important challenges in terms of tacit expertise capitalization and domain analysis. [Principal ideas/results] To tackle this domain formalization issue, we propose a dual Model-driven Engineering (MDE) and Information Retrieval (IR) approach to address the nuclear regulatory requirements domain definition, and assisted traceability based on the acquired requirements model. [Contributions] In this paper, we present the Connexion metamodel that pro- vides a canvas for the definition and capitalization of the nuclear regu- latory requirements domain. We also present an hybrid MDE/IR-based approach, named INCREMENT, for acquiring, modeling and analyzing these regulatory requirements. This approach is supported by a tool that is developed in the context of the CONNEXION project, which gathers French major nuclear I&C industrial actors.