Cladding failure by local plastic instability

Technical Report · Thu Dec 01 00:00:00 EST 1977

DOI:https://doi.org/10.2172/5053513· OSTI ID:5053513

Kramer, J M; Deitrich, L W

Cladding failure is one of the major considerations in analysis of fuel-pin behavior during hypothetical accident transients since time, location, and nature of failure govern the early postfailure material motion and reactivity feedback. Out-of-pile thermal transient tests of both irradiated and unirradiated fast-reactor cladding show that local plastic instability, or bulging, often precedes rupture and that the extent of local instability limits the initial rip length. To investigate the details of bulge formation and growth, a perturbation analysis of the equations governing large deformation of a cylindrical shell has been developed, resulting in a set of linear differential equations for the bulge geometry. These equations have been solved along with appropriate constitutive equations and various constraints on the ends of the cladding. Sources for bulge formation that have been considered include initial geometric imperfections and thermal perturbations due to either eccentric fuel pellets or nonsymmetric cooling. Of these, only the first is relevant to out-of-pile burst tests. Here it has been found that the most likely imperfection that will grow unstably to failure leads to a bulge around half the circumference with an axial length 1.1 times the deformed diameter. This is in general agreement with burst-test results. For the case of in-reactor fuel pins, it has been found that thermal perturbations can significantly affect local instability, particularly if the deformation process is thermally activated with a high activation energy.

• Research Organization: Argonne National Lab., Ill. (USA)
• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 5053513
• Report Number(s): ANL-77-95; TRN: 78-008424
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
FUEL ELEMENT FAILURE
LMFBR TYPE REACTORS
REACTOR ACCIDENTS
DEFORMATION
FUEL PINS
PLASTICITY
SIMULATION
TRANSIENTS
ACCIDENTS
BREEDER REACTORS
EPITHERMAL REACTORS
FAST REACTORS
FBR TYPE REACTORS
FUEL ELEMENTS
LIQUID METAL COOLED REACTORS
MECHANICAL PROPERTIES
REACTOR COMPONENTS
REACTORS
220900* - Nuclear Reactor Technology- Reactor Safety