The top thermal shields of the Hanford reactors were formed by placing single layers of large cast iron blocks on the top of the graphite stacks. Accumulative distortion of the graphite stack is causing several inches of variation in the elevation of the originally level top thermal shields. The integrity of the top thermal shield cooling tubes is of concern because of the high axial and bending stresses they are subjected to from the shield variations in addition to the normal service conditions common also to the side and bottom thermal shields. Concern for possible deteriorating condition of the top cooling tubes has increased with the discovery of a leaking cooling tube at the C Reactor. This report provides information of the present condition of the cooling tubes and discusses continued surveillance of their condition which is required for evaluation of their continued serviceability.

None