5. (1) A member of the Commission shall hold office for a period of three years from the date of his appointment and shall be eligible for re-appointment for such further period or periods, not exceeding three years at any time, as the Government may decide: Provided that no member shall hold office for more than two consecutive terms, unless under special circumstances, to be decided by the Government, where the services of a member is expressly desired in the interest of Nuclear Science. (2) A person appointed to be a member of the Commission may at any time resign his office by letter addressed to the Chairman: Provided that no resignation shall take effect until it has been accepted by the Government. (3) A vacancy caused by resignation or any other reason shall be filled by appointment of a person qualified to fill such vacancy. (4) The Government at any time terminate the appointment of the Chairman or any other member of the Commission without assigning any reason. (5) No act or proceeding of the Commission shall be invalid merely on the ground of the existence of a vacancy in, or defect in the constitution of, the Commission.