Effect of Hydrogen, Hydride Orientation and Temperature on Low-Cycle Fatigue Resistance of Zr-1%Nb Fuel Rod Claddings

Low-cycle fatigue testing was conducted on annular samples with an outer diameter of 9.13 mm, a wall thickness of 0.68 mm and a width of 2.7 mm, namely: non-hydrogenated samples (cut out of standard Zr‑1%Nb cladding tubes); hydrogenated samples with a hydrogen concentration of 50 ... 400 ppm; samples cut out from hydrogenated dummy claddings after hydride reorientation tests performed according to various test modes. The tests were conducted at the temperatures of 25, 180, 350, 400 and 450 °С. The results obtained demonstrate that with increasing the hydrogen content in Zr-1%Nb alloy claddings the fatigue life increases.

FACILITY FOR HYDROGENATION AND THERMAL TESTING OF INTERNALLY PRESSURIZED DUMMY FUEL RODS

A facility allowing to conduct experiments on dummy fuel rods up to 250 mm long, at temperatures up to 700 °C is presented. The designed facility is unique in that the conditions for the tests to be conducted on it most closely resemble (except for irradiation) those of fuel rods operation, loading and storage in SFDSF. All test parameters are programmed and regulated by special sensors, which brings the experiment on fuel rod temperature effect and pressure under the cladding as close as possible to the conditions of fuel rod operation in reactor and further storage in SFDSF. Hydride Reorientation Test (HRT) was conducted on dummy fuel rod sunder internal pressure of 3...5 MPa (at room temperature) and with hydrogen concentration of 50...300 ppm in the modes that simulate SNF handling with limiting heating to 410 °С and accidents with seven 410↔300 and 410↔180 °С thermal cycles. It has been demonstrated that the effectiveness of the influence of the test conditions in the specified modes on hydride reorientation increases with increasing hydrogen concentration and tangential stresses in the dummy fuel rod claddings. It has been shown that the test samples design, control and measurement devices, as well as the parameters estimated during the test and further investigations fully meet the test requirements.