Where the employer and employee are subject to the provisions of this chapter, the disablement or death of an employee caused by occupational exposure to radiation, as defined in this article, shall be treated as an injury by accident, and the employee or, in case of his death, his dependents shall be entitled to compensation as provided in this article. In no case, however, shall an employer be liable under this article for compensation by reason of exposure to radiation or for disability or death resulting therefrom unless such exposure arose out of and in the course of the employment and resulted from the nature of the employment in which the employee was engaged.