[en] The helium circulators for the Fort St. Vrain nuclear power station incorporate bellows-actuated shutdown seals. Circulator C2102 was removed in March 1976 from its penetration following a suspected failure of the bellows actuator or its supply line, as evidenced by a substantial leak. The circulator was returned to San Diego for disassembly and inspection. Examination of the shutdown seal revealed the failure to be a circumferential crack in the inner bellows in the crown of the first convolution adjacent to the fixed end. Investigation of the failure showed that the crack was most probably initiated by repeated overextension of the bellows prior to installation in the circulator and was propagated by shorter stroke cyclic loading. It was concluded that the conditions leading to failure were abnormal and unique to this particular seal and circulator. Therefore, the failure does not appear to be indicative of a generic problem