Are these result variation normal in the criticality over burnup on the two different method
The rate of burnup will depend on a lot of factors, so if you blindly run two codes without thinking about what data they are using, it’s easy to end up with results that don’t match. I would highly suggest reading our “caveats” section in the user’s guide description of depletion. The biggest factor that will affect the rate of burnup is the Q values that are used for fission. If you want to get two codes to match, you should ensure they are using the same Q values for fission if possible, which can be done using the fission_q argument to the openmc.deplete.Operator class.