Research Highlight

Rig designed to study effect of vibration on spent nuclear fuel

A fatigue-fractured, high-burn-up spent nuclear fuel rod shows failure at the pellet-pellet interface (top), where the fuel pin number is clearly visible from the failed pair. A lateral view (bottom) shows a failed specimen of 2-inch gauge section.

Researchers have developed an innovative system, called Cyclic Integrated Reversible-bending Fatigue Tester (CIRFT), to test and evaluate the mechanical behavior of spent nuclear fuel (SNF) under normal transportation conditions. The SNF fatigue data generated by CIRFT technology are essential in assisting back end fuel cycle reliability investigation.

High burn-up (HBU) (>45 GWd/MTU) nuclear fuel is associated with increased corrosion and hydride precipitation and high levels of irradiation-induced damage to cladding and fuel pellets. Each of these HBU phenomena has the potential to impact the mechanical behavior of spent nuclear fuel. During transportation, SNF experiences unique conditions and challenges to the cladding integrity as a result of vibrations encountered during road or rail shipment. Understanding the role of fuel pellet–pellet and fuel pellet–cladding interactions is critical to characterizing the SNF system’s dynamic performance. Until recently, however, such data has not been available due to the lack of an effective testing system. Testing HBU SNF with fuel intact presents many challenges, mainly because the tasks are complicated by the radioactivity of the test specimens.

The HBU SNF rods with Zircaloy-4 and M5 cladding were studied under both quasi-static and dynamic reversal bending. The majority of the SNF dynamic test samples fractured at or near a pellet–pellet interface. The fatigue life of HBU SNF rods during dynamic testing mainly depended on the level of vibrational loading and fuel pellet–cladding interaction and the conditions of the rod.

 

1   J.-A. Wang, H. Wang, H. Jiang, B. B. Bevard, R. L. Howard, “CIRFT Testing Results on High Burnup UNF,” M2-FCRD-UFD-2014-000053.

 

For more information contact J-A. Wang (wangja@ornl.gov)

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