Del. Code tit. 29, § 5529

Upon the death of an employee, former employee or pensioner or if a survivor’s pension is payable upon such death, when such pension ceases to be payable, there shall be paid to the designated beneficiary or, in the absence of a designated beneficiary, to the estate of the employee, former employee or pensioner a lump sum equal to the excess, if any, of the accumulated employee contributions with interest over the aggregate of all pension payments made.