A new ferritic superalloy, which exhibits coherent coplanar ordered nanoscale (Ni,Fe)Al B2-type precipitates analogue to the Ni-based superalloy, has been fabricated and shown good creep resistance for the potential application of ultrasupercritical steam turbines. In order to further improve the creep resistance, the motivation of the proposed work is to investigate the relationships between microscopic elastic lattice strain and macroscopic creep behavior, and thus provide some micromechanical insights into creep deformation. The objectives are to utilize in-situ neutron diffraction to (1) measure the elastic strain evolution during in-situ isothermal creep tests as a function of time and stress, (2) obtain the evolution of lattice misfit as a function of temperature with and without loading, and (3) estimate the volume fraction of B2 phase and check other minor phases.