A seal disc, also known as a “soft seal stubby”, used at the Nuclear Power Demonstration (NPD) reactor as a temporary seal for a leaking end fitting on a fuel channel. The metal-metal seal was made on the outer edge of the “rimmed” face by cantilevering the entire disc. The discs, which have an outer diameter of 16 cm, were manufactured in varying thicknesses with this specific one (serial number 817) being 0.310 inches (7.87 mm) in thickness. The version of seal was temporary in nature in that it was used until a shutdown during which the regular sealing surface on the end fitting could be remotely retooled (ground) to correct the marred surface causing the leak. The imperfection most likely would have occurred during a refueling operation.
