(a) Until the first payment of any member's retirement allowance becomes normally due, he may elect to convert the retirement allowance, otherwise payable to him, into a modified retirement allowance of equivalent actuarial value in accordance with one of the optional forms named below, provided that if he dies within 30 days after retirement, his optional election shall not be effective and he shall be considered to have been a member in service at the time of his death.

(b) Option one shall consist of a reduced retirement allowance payable during the life of the retired member, with the provision that, if he dies before he has received, in payments of his annuity, the amount of his accumulated contributions at the time of his retirement, the balance of such amount shall be paid to the person, if any, nominated by him by written designation duly executed and filed with the board of trustees, otherwise to the retired member's estate.

(c) Option two shall consist of a reduced retirement allowance payable during the life of the retired member, with the provision that after his death the reduced retirement allowance shall be continued throughout the life of and paid to the person nominated by him by written designation duly executed and filed with the board of trustees at the time of his retirement.

(d) Option three shall consist of a reduced retirement allowance payable during the life of the retired member, with the provision that after his death one-half of the reduced retirement allowance shall be continued throughout the life of and paid to the person nominated by him by written designation duly executed and filed with the board of trustees at the time of his retirement.

(e) Option four shall consist of a reduced retirement allowance payable during the life of the retired member, with the provision that upon his death some other benefit shall be payable, provided that the total value of the retirement allowance payable during his life and the succeeding benefit shall be computed to be of equivalent actuarial value to the retirement allowance which he would receive had he not chosen an optional retirement allowance under this Code section; provided, further, that the benefit shall be approved by the board of trustees.

(f) Whenever any member has elected an optional allowance under this Code section and has nominated his spouse to receive all amounts and benefits payable on or after his death as a result of such election, the member may revoke the election at any time after the entry of a final judgment of complete divorce from the spouse so nominated. Upon any such revocation, the member may elect to return to the retirement allowance otherwise payable to him or to elect to convert the retirement allowance otherwise payable to him into a modified retirement allowance of equal actuarial value as of the time of the election and in accordance with one of the optional forms named in subsections (b) through (e) of this Code section.

(g) The board of trustees shall promulgate rules and regulations to carry out this Code section.

(h) Upon the death of the retired member and then the death of the person designated by him to receive continuing retirement benefits under option two, three, or four if the total monthly benefits paid to the retired member and to such person designated to receive continuing benefits do not equal or exceed the retired member's accumulated contributions at the time of his retirement, the difference shall be refunded to the person designated in writing by the retired member to receive such a refund of this difference. If no such person is designated to receive this difference, or if such designated person has predeceased the person designated to receive continuing monthly retirement benefits, or if such designees are the same person, this difference shall be paid to the estate of the person designated to receive continuing monthly retirement benefits.

(i) Upon the death of the person designated by the retired member to receive continuing monthly retirement benefits under option two, three, or four and then the death of the retired member, if the total monthly benefits paid to the retired member prior to his death do not equal or exceed the retired member's accumulated contributions at the time of his retirement, the difference shall be refunded to the person designated in writing by the retired member to receive such a refund of this difference. If the person designated by the retired member to receive a refund of this difference also predeceases the retired member, or if such designees are the same person, or if no person is designated to receive this difference, this difference shall be paid to the estate of the retired member.

(j) Any other provisions of this Code section or of this chapter to the contrary notwithstanding, the board of trustees may, by rule or regulation, require that when a member or a retired member dies and the beneficiary is a person other than the surviving spouse of the member, the benefits payable to the beneficiary shall be paid to the beneficiary within a definite time period immediately following the death of the member or retired member.

(k) Any retired member who elected option two, three, or four may, after the death of the person designated by the retired member to continue receiving monthly benefits, revoke the election and elect a new option providing for a retirement allowance computed to be the actuarial equivalent of the retirement allowance in effect immediately prior to the effective date of the new option. Such new option shall be effective on the first day of the month following the month in which such new election is made.