Any employee who shall have contributed to the city employees’ pension fund, and who voluntarily and while in good standing as an employee of said city shall have left the employment of such city, shall be entitled, upon application at the time of such retirement, to a refund of all contributions made by the employee without interest and exclusive of the membership fee, payable in a lump sum. If a participant dies and no dependent benefits are payable, the participant’s named beneficiary or estate shall receive the participant’s contributions without interest, less any benefit payments theretofore received. Any employee    who shall have served one hundred eighty months or more, but less than two hundred forty months, and who shall have contributed to the city employees’ pension fund, and who voluntarily and while in good standing as an employee of said city shall have left the employment of such city, shall be entitled to elect retirement instead of refund, but at a pension equal to the proportion of a full pension as herein provided which the total number of months employed under the plan bears to two hundred forty months, but no pension shall be paid while the employee lives until the employee reaches the age of sixty years.