The MC21 Monte Carlo code is required to permit an individual geometric component or groups of components to be tagged as ''movable'' within some permissible range. Typical examples of such movable components would be control devices such as translating rods or rotating drums. Given this geometric information, a target multiplication factor (k{sub eff}), and a convergence criterion, MC21 will iterate on movable component positions and return a final position that reflects a k{sub eff} close to the target value. An initial version of this capability is demonstrated through modifications to MC21 that sets the geometry data structures for the movable components, calls the main Fortran-95 solver to compute k{sub eff}, and converges on the final position. This approach uses an adaptive batching algorithm that continually increases the accuracy of each successive MC21 k{sub eff} result as the movable geometry approaches the converged position
