3.30. Understanding of the performance of the disposal system and its safety features and processes evolves as more data are accumulated and scientific knowledge is developed. Early in the development of the concept, the data obtained and the level of understanding gained have to assure sufficient confidence to be able to commit resources for further investigations. Before the start of construction, during emplacement of waste and at closure of the facility, the level of understanding has to be sufficient to support the safety case for fulfilling the regulatory requirements applicable for the particular stage of the project.