The person responsible or his successor for a nuclear activity or a past or present professional activity likely to cause, directly or indirectly, exposure of persons to ionising radiation or to emissions of radioactive substances, which cannot be neglected from the point of view of radiation protection, shall take all necessary measures to reduce such exposure in accordance with the provisions of article L. 1333-3. The financial obligations linked to the application of these provisions lapse thirty years after the competent administrative authority becomes aware of the impact on health of the said exposure.