(a) If monthly payments of any standard service retirement annuity under Section 854.103, optional service retirement annuity under Section 854.104, standard disability retirement annuity under Section 854.304, optional disability retirement annuity under Section 854.305, standard occupational disability retirement annuity under Section 854.408, or optional occupational disability retirement annuity under Section 854.410 cease before the sum of all payments of the annuity equals or exceeds the amount of accumulated contributions credited to the member’s individual account at the time of retirement of the member on whose service the annuity was based, a lump-sum benefit equal to the amount by which the amount of the accumulated contributions exceeds the sum of all payments made by reason of the annuity is payable:
(1) to the designated beneficiary, if living, or if not living, to the estate of the designated beneficiary, if the designated beneficiary survived the retiree; or
(2) to the estate of the retiree, if the designated beneficiary predeceased the retiree.
(b) The benefit provided by this section is payable from the benefit accumulation fund.