1D diffusion Neumann boundary condition simulation with modulus

Hey! I am new to Modulus and I am building a 1D example of a diffusive particle and want to try with a Neumann boundary condition. I found Modulus has a diffusion interface constraint, but for that purpose I have to simulate a second geometry with a different diffusivity. What I want to do is simply state that my isolated geometry won’t let my diffusive particle escape. Is there any other way to do so? I also thought of trying to compute the derivative myself as criteria and equal it to zero, but I cannot work with the key of the solution to compute the derivative, is there maybe a way around this as well?