Any participant in the Foreign Service Retirement and Disability System who is separated under subsection (a) of this section shall be entitled to receive a refund as provided in section
4055 of this title of the contributions made by the participant to the Foreign Service Retirement and Disability Fund. Except in cases where the Secretary determines that separation was based in whole or in part on the ground of disloyalty to the United States, a participant who has at least 5 years of service credit toward retirement under the Foreign Service Retirement and Disability System (excluding military and naval service) may elect, in lieu of such refund, to an annuity, computed under section
4046 of this title, commencing at age 60.