In case of occupational exposure to radiation, as defined in this article, or of injury or disability resulting therefrom, all claims for compensation shall be forever barred, unless within one year after the employee first suffered disability therefrom and either knew or in the exercise of reasonable diligence should have known that the disability was caused therefrom, but in no event more than three years after date of the injury as hereinafter defined, the parties shall have agreed upon the compensation payable under this article, or unless within such period of time one of the parties shall have filed a verified complaint as provided in Section 25-5-88. In case of death, all claims for compensation shall be forever barred, unless the death results proximately from occupational exposure to radiation, as defined in this article, and occurs within three years of the date of the injury, as hereinafter defined, and unless within one year after such death the parties shall have agreed upon the compensation under this article, or unless within one year after such death one of the parties shall have filed a verified complaint as provided in Section 25-5-88; provided, however, that if upon the date of the death of the employee the employee’s claim is barred, any claim by or for his dependents shall likewise be barred. Where, however, payments of compensation have been made in any case, said limitations shall not take effect until the expiration of one year from the time of making the last payment. In case of the mental incapacity of the injured employee or his dependents to perform or cause to be performed any act required within the time in this section specified, the period of limitation in any such case shall be extended to become effective one year from the date when such incapacity ceases. No agreement, express or implied, to shorten or to extend said limitations shall be valid or binding on either of the parties when said employment, at the time of said exposure, is or was subject to the provisions of this article. The “date of the injury” shall mean, for all purposes of this article, the date of the last exposure to the hazards of radiation in the employment of the employer in whose employment the employee was last exposed, within a period of five years prior to the date of the injury, to the hazards of radiation in each of at least 12 months.