This paper presents some preliminary observations from six representative tests on the plastic behavior of small bore carbon steel piping bends/elbows with general and local wall loss subject to combined internal pressure and bending moment loading at typical CANDU® reactor operating temperature. These six tests include three materials (normalized elbow, stress relieved bend and cold worked bend), two piping sizes (NPS 2 and NPS 2 1/2), two loading modes (monotonic and cyclic) and three modes of failure (collapse, burst and leak). The test results show that a collapsed piping bend/elbow can still withstand five times design pressure without the loss of pressure boundary. The stress relieved bend appears to offer a compromise in the resistance to both environmental assisted cracking and plastic collapse relative to the normalized elbow and cold worked bend.

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