Tenn. Code Ann. § 8-25-209

Any employee participating in an optional retirement program whose benefits are limited to those of that program pursuant to § 8-25-207, may authorize the transfer of the employee's accumulated contributions deposited with the retirement system to such optional retirement program upon request made to the retirement system. Such transfer shall be made within ninety (90) days of the retirement system's receipt of the request, and shall be considered to be a withdrawal of accumulated contributions and shall terminate membership in the retirement system, in accordance with § 8-35-104. Any such transfer constitutes a waiver of all rights in the retirement system and may not be redeposited with the retirement system pursuant to § 8-37-214.