Should a member cease to be a teacher, except by death or retirement under the provisions of this chapter, he shall be paid upon application made not less than four (4) months following his cessation of service the amount of the accumulated contributions standing to the credit of his individual account in the members' contributions account. Should a member die before retirement, the amount of his accumulated contributions standing to the credit of his individual account shall be paid to his estate or to such person as he shall have nominated by written designation, duly executed and filed with the board of trustees; provided, that such member has not made an optional election which has become effective.
T.C.A. § 49-1524