It is agreed and understood that otherwise subject to the terms, exclusions, provisions and conditions contained in the Policy or endorsed thereon, cover shall be extended to include loss of gross profits resulting from prolongation of the interruption or interference due to the decontamination of items specified in the List of Machinery and Plant Insured, provided that the contamination was caused by indemnifiable material damage to the item(s) with instruments containing radioactive isotopes specified in the List of Machinery and Plant Insured.