(a) On or after July 1, 1973 any pensioner who returns to active public service, rejoins the Retirement System, renders at least one year of member service credit after restoration to active service, and has elected a death benefit pursuant to section 448 of the Retirement and Social Security Law, shall, upon his death while in service be entitled to full credit for all former service credit in the calculation of the death benefit.

(b) Such total service credit to which he is entitled shall be so credited only in the event the member returns to the Retirement System, with regular interest, the actuarial equivalent of the amount of the retirement allowance he received. In the event that such amount is not so repaid, the actuarial equivalent thereof shall be deducted from the death benefit. The provisions of this section shall be applicable only in the event the resulting death benefit will exceed the death benefit which would otherwise be payable.