Steam Turbine Failure at Hinkley Point ‘A’

Abstract

The catastrophic failure of Hinkley Point ‘A’ unit No. 5 in September 1969 was the result of spontaneous brittle fracture of a shrunk-on ***l.p. turbine disc, initiated by stress-corrosion cracking in the crown of a keyway in the disc bore. Stress corrosion cracking of disc bores and keyways was also found on a number of other discs. The discs were made of 3 Cr-Mo steel and complied with normal acceptance standards, but due to temper embrittlement, their fracture toughness was low, and cracks only about 1/16 in deep in the concentrated stress field at the keyway crown were large enough to initiate brittle fracture. Investigation of the cause of the stress-corrosion cracking is being separately reported.