Thermal transient strength test of 24-inch elbow; Test at ETEC under PNC/USDOE corporation and its analysis

not registered; not registered; Atsumo, Hideo

As a part of PNC-USDOE corporation in the field of fast breeder reactor, thermal transient test of 24-inch elbow, made of type 304 stainless steel, was performed at ETEC (Energy Technology Engineering Center). Test results were analysed and evaluated at PNC. Following results were drawn from the test and the relevant stress analysis: (1)Thermal transient test was performed under constant in-plane bending moment and cyclic rapid cooling by nitrogen gas. When the mechanical load was increased step by step, shakedown or ratchetting behavior was observed under or above a certain level of load. For typical points at inner and outer surface of elbow, strain was measured by using high-temperature strain gage. (2)Thermal ratchetting analysis was performed by using FINAS. Coincidence between analysis and test results was obtained for qualitative shake down or ratchetting behaviour. As to increment of displacement or strain per cycle, analytical results were fairly larger than test results. (3)In the case of this test, in which creep effect is negligible, ratchetting load calculated by current high-temperature structural design method (ASME Code Case N-47 and PNC's structural design guide) gives sufficiently concervative value. (4)Thermal ratchetting mechanism of elbow under in-plane bending moment was identified as follows by test and analysis : bending deformation in circumferential direction at elbow side; extensional deformation in longitudinal direction at outer point from the elbow side by 20-degree; compressive deformation in longitudinal direction at inner point from the elbow side by 30-degree. (5)Ratchetting condition can be estimated fairly well and conservatively by taking following parameters in Bree's diagram : x = [(membrane stress) + (bending stress)/(section factor)]/(yield stress), and y = (thermal stress using equivalent linear temperature difference)/(yield stress). (6)Comparing this test with another test for smaller elbow at O-arai Engineering ...