Radiation Damage to the graphite moderator has played an important role in the history of reactor operation at Hanford. The operational problems, potential and real, which result from dimensional instability, stored energy, and gasification, as well as the solutions to these problems are discussed. The key to the graphite problems is operating temperature and its control. At present, stack expansion remains in the fringe regions of the original reactors, which coupled with the contraction of the central region gives rise to curvature problems in the top portion of the reactors. Stored energy is not a safety hazard because the release spectrum is such that a spontaneous and self sustained release cannot occur. Oxidation of the graphite moderator is controlled by maintaining operating temperature of the stack such that no significant amount of oxidation occurs.