Tenn. Code § 49-1553
Until the first payment on account of any benefit becomes normally due, any member of this retirement system, or any local retirement system, may elect to convert the retirement allowance otherwise payable to him to a reduced retirement allowance of equivalent actuarial value with the provisions that:
Option 1. [Repealed, Acts 1971, ch. 152, § 18.]
Option 2. Upon his death his reduced retirement allowance shall be continued throughout the life of, and paid to, such person as he shall nominate by written designation duly acknowledged and filed with the board of trustees at the time of his retirement; or
Option 3. Upon his death, one half (½) of his reduced retirement allowance shall be continued throughout the life of, and paid to, such person as he shall nominate by written designation duly acknowledged and filed with the board of trustees at the time of his retirement.
The election of an option shall become effective on the first date the member becomes eligible for service retirement or thirty (30) days after his date of retirement on disability, if earlier, except that no such election shall become effective until thirty (30) days after written application therefor has been filed with the board of trustees. Should a beneficiary die before any such election has become effective he shall be considered as an active member on the date of his death. Should a member die after any such election has become effective he shall be considered as having been retired on the date of his death. The election of the option may not be changed or revoked by the member after it has become effective, but if the person designated under the option dies prior to the date of retirement of the member, the option shall thereby be revoked. Notwithstanding the previous sentence if a member who has become eligible for service retirement has elected an option which has become effective, and continues in service, he may change or revoke such election prior to retirement, but such change or revocation shall not become effective until thirty (30) days after written notice has been filed with the board of trustees.
The above provisions of this section or of any section of §§ 49-1501 through 49-1562 to the contrary notwithstanding, the spouse of any member, who after July 1, 1968, became deceased without having elected an option, and who was eligible to have done so thirty (30) days or more before becoming deceased, shall receive a monthly retirement benefit in the same manner and amount that he or she would have received had the member elected option 2; provided, however, that if a lump-sum payment has been made to the beneficiary under the provisions of § 49-1524, the monthly retirement benefit payments shall not begin until such time as the beneficiary would have received payments that totaled the lump-sum payment already received had the deceased member elected option 2, and further provided that all claims for retirement benefits filed under the provisions of this act shall be filed before July 1, 1970.
T.C.A. § 49-1553