You don't need to rewrite the whole thing, or read any Cobol. Collect the requirements, write the code.
It shouldn't be too difficult, the actual rules on dispensation are relatively simple. The code to send checks to a printer or ACH processor is simple and ubiquitous. Don't let anyone fool you, just because it's government and important doesn't mean it's particularly special.
A company I worked for had been running on AS400 for decades, but we were able to move to a SQL based backend with a web app on top of it, and we were in UAT within 1 year. Believe me, the financial data we dealt with was far more complex and convoluted than Social Security, with exceptions to every business rule, exceptions to exceptions, and a minor fuckup could expose us to massive legal risk.
This shouldn't be difficult. If SSA can define the business rules and RBAC, this should take less than a year with the right technical resources and a good project team.
^ this
This lame excuse for not rewriting code gets used too often by people who don't know how to program. COBOL is not ancient magic. You don't need to touch it if you simply build a new system from the requirements as was said above. The real reason they don't want to do that is that a rewrite will expose how little they actually know about the current system and the actual rules and logic that govern it. A new system will shine light on the fuckery that was put in the original system to do the things they want hidden. A good team of non-pajeet programmers (i.e. straight White men) can replace this old code in a year or two, but that would, again, expose the fuckery in the system. They will live with the COBOL because it hides the bodies.
This, 100%