With the removal of the plutonium enrichment process ( 40 p-239 + 5 p-238 ----> 42 p-239 + 2 p-238 ) there is no longer a process to turn p-238 exssess into p-239.
I would wish there was a way for p-238 to be turned into p-239. Maybe by buffing the output of p-239 in the breeder fuel cell reprocessing recipe. Or by making a fourth breeder cell recipe that requires much more p-238 than p-239.

I personally would love it if there was a super complicated, fourth breeder cell recipe that allowed for p-238 to turn into p-239 by using mountains of p-238 in its recipe. Here is a recipe idea: 1 used uranium fuel cell + 1 used MOX fuel cell + 1 used breeder fuel cell + 20 uranium ore + 50 p-238 --> 20 breeder fuel cell.
However I must acknowledge this is your mod and you can do whatever you wan't with it.

Additionally. I think this was accidental, but you removed the plutonium fuel rod recipe when you removed the plutonium enrichment process technology.

I may have the math wrong here so correct me if im wrong (there is SO much abstraction with recipe based math) but my rough calculations tell me that you need 5 breeder reactors to support about 3 MOX reactors, i think 15:10 is the more accurate ratio if you're going for closed cycle that is, though you will have TONS of pu 238 more so if you reprocess used MOX. Now im playing with numerous mods, and currently im able to convert uranium to neptunium, and then to pu239 so the lack of accessible plutonium isnt a huge issue, but thats not PE doing that (at least i dont think so). Either, the breeder cell recipes should align nicely with the MOX fuel recipes or there should be some method to get rid of excess pu238 other than ammo obviously. That and perhaps breeder reactors should burn more fuel, they're monumentally slow as is. Similar reactors IRL can burn much much hotter. That would be a fairly simple buff to implement.

One lazy option is just keeping enrichment but making it take AGES, with the mods im playing with kovarex takes 2100 seconds to complete which is an absolute pain, forces you to optimize your fuel cycle or have insane kovarex production and handling. In order to support a 1.1gw 8 reactor plant off of kovarex alone you need upwards of 220 centrifuges running near constantly. Its basically the same physical size as a 1.1gw plant and makes it a mess to deal with (each centrifuge stores like 80 uranium unless you run circuit conditions on all of them)

As a nuclear nerd myself i understand the want for realism, but lets be honest, storing hundreds of thousands of u238 and pu238 just aren't interesting or practical for factorio, especially considering the life span of fuel cells. Refueling only needs to happen once a year at most in real reactors. I think there are a few that run shorter cycles but those aren't for power generation afaik.

Thanks for poiting out the issue! I'll see what mechanic I can implement to convert pu-238 to something more usable. I don't want to put it in breeder directly yet.

And to answer @KillingTimeItself's suggestion: I purposefuly made breeder reactors not very powerful, because I wanted them to not be a primary energy generation source, but rather focused on generation of plutonium.

Thank you John:) !!!!!FEATURE CREEP CONFIRMED!!!!!

Thanks for poiting out the issue! I'll see what mechanic I can implement to convert pu-238 to something more usable. I don't want to put it in breeder directly yet.

And to answer @KillingTimeItself's suggestion: I purposefuly made breeder reactors not very powerful, because I wanted them to not be a primary energy generation source, but rather focused on generation of plutonium.

im unsure how the game mechanics work with reactors but i would assume you could increase the fuel consumption independently of power output. You could pretty easily 4x the consumption and still contain realistic values, though they won't line up with the other reactors anymore so that's not ideal.

though if you don't want to do that i can understand. Just wanted to say this is one of the more interesting nuclear mods, been having fun with this and a handful of other nuclear mods lately.

The power output and fuel consumption of a rector are tied, but the fuel value of a cell can be decreased to shorten its lifespan. Which would probably make sense in the mod's concept of breeder reactors - almost no energy output, but produces valuable isotopes.

The power output and fuel consumption of a rector are tied, but the fuel value of a cell can be decreased to shorten its lifespan. Which would probably make sense in the mod's concept of breeder reactors - almost no energy output, but produces valuable isotopes.

yeah, that is essentially the same thing as changing the burn up rate in this case. That's definitely an option to buff breeder reactor production.