S.D. Codified Laws § 3-12C-1214
Upon the death of a generational member who was vested or died while performing usual duties for the employer and who has reached normal retirement age but has not yet begun a retirement benefit, a surviving spouse is eligible to receive a surviving spouse benefit. The surviving spouse benefit is equal to sixty percent of the actuarially reduced amount the member would have received if the member retired on the date of death and elected the sixty percent joint and survivor benefit. The annual benefit shall be divided into monthly payments and is payable for the life of the surviving spouse. The surviving spouse benefit is effective the first day of the month following the date on which the member's contributory services terminates and is payable upon receipt of a completed application.
SDCL 3-12C-1214