(1) Subject to a member's right to a refund of the member's accumulated contributions under Title 19, chapter 2, part 6, the following members are eligible to receive a nonforfeitable service retirement benefit under 19-8-603:
(a) a member who has terminated service, completed at least 20 years of membership service, reached 50 years of age, and files a written application with the board; or
(b) a vested member who terminated service before completing 20 years of membership service and applies to begin receiving a service retirement benefit upon reaching 55 years of age.
(2) For purposes of compliance with section 411 of the Internal Revenue Code, 26 U.S.C. 411, a member described in subsection (1)(a) is treated as having attained normal retirement age and has a nonforfeitable right to the member's service retirement.