Engineering topics

Lazarevic, Sladjan

Publications and source records attributed to Lazarevic, Sladjan.

4 records

DOE OSTI2018

Investigating grid-to-rod fretting wear of nuclear fuel claddings using a unique autoclave fretting rig

Fuel rods in a pressurized water nuclear reactor (PWR) experience coolant flow-induced relative motion against the grid support features, a phenomenon called grid-to-rod fretting (GTRF), which may cause progressive fretting wear damage. Wear-through of the cladding on fuel rods will leak the radioactive fuel into the coolant loop to significantly increase the radiation level in PWR primary loop and often trigger expensive Post Irradiation Examination. In this work, a unique autoclave fretting test rig was designed and fabricated to allow studying GTRF using actual cladding and grid materials. Water temperature was up to 220 °C, which was designed to mimic the environment in an industry full-assembly reactor core simulator. The contact load (0.1–1 N), oscillation frequency (20–30 Hz) and stroke (50–150 µm), and work rate (1–3 mW) were defined based on simulations of GTRF in an actual reactor. Using this autoclave GTRF rig, tests were conducted to learn the effect of water temperature and to investigate the wear behavior of different cladding-grid material combinations currently used in actual PWRs, including Zr alloy claddings without and with pre-oxidation against Zr alloy and Inconel grids. Higher water temperature evidently increased the cladding wear, and pre-oxidation of the Zr alloy and/or using the Inconel grid effectively reduced the wear rate. In conclusion, results were correlated with the data of a full-size industry reactor core simulator in terms of both wear rate and wear scar morphology.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2018

Benchscale Evaluation of Nanodiamond Oil Additives

This CRADA between Cool-X and ORNL was to investigate the impact of diamond nanoparticles as diesel engine oil additives on lubricating behavior and gain fundamental understanding of the friction and wear reduction mechanisms. Systematic tribological bench tests were used for evaluating the Cool-X diamond nanoparticles (ND) as candidate diesel engine oil additives, and surface characterization was carried out to reveal the friction reduction mechanisms. No significant micro-rolling effect or increased oil pressure-viscosity coefficient was observed. Instead, a faster running-in and moderate friction reduction were achieved by the ND in tests of used diesel engine components, which was attributed to the polishing effect. ND agglomeration seemed to a problem and could significantly impair the functionality and future research is needed to seek the mitigation.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2017

Summary report describing CASL accomplishments in support of the GTRF Challenge Problem

Coolant flow-induced relative motions between structural components in the cores of lightwater nuclear reactor cores, a phenomenon called Grid-To-Rod Fretting (GTRF), can result in progressive wear damage. Wear-through of the cladding on fuel rods can introduce radioactive species into the coolant loop. Such an event is termed a “leaker” and may cause premature and expensive reactor shut-down. GTRF results in wear scars of various sizes, shapes, and depths on the sides of the fuel rod cladding. Fretting damage may also occur on the springs and dimples that hold the fuel rods in place, resulting in the formation of gaps. Due to variability in the operating conditions of the reactor (burn-up rates and operating campaigns) and the associated variable cladding surface oxide film growth and removal rates, the wear coefficient is unlikely to remain constant over time. Therefore, constant wear rate models do not accurately account for transients in the operating conditions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2017

GTRF Cladding Wear Modeling and Experimental Validation

Coolant flow-induced relative motions between certain structural components in the cores of lightwater nuclear reactor cores, a phenomenon called Grid-To-Rod Fretting (GTRF), can result in progressive wear damage. Wear-through of the cladding on fuel rods can introduce radioactive species into the coolant loop. Such an event is termed a “leaker” and may cause premature and expensive reactor shut-down. GTRF results in wear scars of various sizes, shapes, and depths on the sides of the fuel rod cladding. Fretting damage may also occur on the springs and dimples that hold the fuel rods in place, resulting in the formation of gaps. Due to variability in the operating conditions of the reactor (burn-up rates and operating campaigns) and the associated variable cladding surface oxide film growth and removal rates, the wear coefficient is unlikely to remain constant over time. Therefore, constant wear rate models do not accurately account for transients in the operating conditions.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗