A setup I use for my 235 production. An easily tilealbe 4x6 design.
Each run the inserter's will re-circulate the 2 units of 238 and 40 units of 235. The extra unit of 235 is removed from the system and can be placed on a belt or chest as required. A buffer of 238 is held by the requester chest to continue the process.
The decider combinator settings are shown on the image for your convenience. This system runs without any intervention, I have not had any issues since 0.16. Potentially with low power, the system could lock due to inserter speed however; I am yet to see this happen.