You will automatically be placed in TRICARE standard, which will have no monthly payments, but has copays, generally 20% but depends on what they are doing. It also has a deductible, meaning you must pay $300 (150 if single) before coverage begins. This functions much like the prime's enrollment fee, except there is no payment if you don't visit a doc.
TRICARE prime is location dependent, so you may not qualify. It has an annual enrollment fee of $555.84 per year, or a little less than $50/month. It has a set cost for service instead of copays, generally much lower. You will have to call TRICARE after separation and request enrollment into prime.
