Clad deformation

In the mechanism of corrosion due to MOX—clad interaction the fission product tellurium plays a dominant role, but several interdependent parameters can interfere among which on one hand, the critical pin bum-up rate (5—6%) having to be reached to generate the necessary chemical conditions to activate the Te-assisted corrosion and, on the other hand, the in-pile clad deformation via swelling and irradiation creep that produces an overheating of the fuel and thus an acceleration of the corrosion as shown in Fig. 8.3 [19]. 

Average max. linear clad deformation observed after irradiation on 3 lots of a same subassembly and belonging to the same phenix specification of standard CW15/15Ti... 

R. H. Chapman et al, "Zircaloy Cladding Deformation in a Steam Environment with Transient Heating," pp. 393-408 in Zirconium in the Nuclear Industry (Fourth Conference). ASTM STP 681, American Society for Testing and Materials, Philadelphia, PA (1979). 

As regards the separate effect tests, the development and assessment of the code relies on some national results and mainly on international research data. For example, the cladding deformation model is based on the French EDGAR results, low temperature liquefaction processes due to chemical interactions between core structures are mainly based on the KfK databank [4]- UO2 dissolution by solid and molten Zr, Zr02 dissolution by molten Zr, Zr/Inconel interaction, chemical behaviour of (Ag, In, Cd) absorber rods -fission product release is based on the French HEVA and VERCORS results. 

Case 6 was performed to evaluate the effect of clad deformation on the potential for HPME through comparison to Case 4. The only difference between Cases... 

The potential for HPME was not changed in any of the analyses by variation of the core damage parameters. The changes in cladding deformation limits and debris coolant interaction did have a significant effect on the ultimate timing of lower head failure. 

There are two sources of stress concentration from the fuel concentrations near radial cracks and concentrations near pellet ends. Gittus has analyzed the interaction of opening and closing cracks in frictional contact with the clad (63). Fuel crack width calculations assume that the fuel cracks homogeneously, so the number of cracks in the fuel must be estimated for an actual crack width to be found. As power is cycled the clad adjacent to the fuel crack is stretched when the crack opens and compressed when it closes. Local clad deformations have been produced in out-of-pile experiments and confirm Gittus predictions (13). 

OLYMPUS WARD, Madison Clad deformation from fuel and clad swelling, clad creep, and fuel densification. Calibrated from experimental data 45... 

ANA- YUGAMI PNC, Japan ANA code claculates temperature and central void radius. YUGAMI code calculates steady-state fuel-clad deformation using a method similar to DEFORM 90... 

Spent Removable Unit (SRU) of KM-1 stand with 105%-lrfetime power output has been stored at the storage facility since 1987. Over the storage period double meltingfreezing of Pb-Bi alloy took place tliat could have resulted in fuel element deformations with partial damage of claddings. 

Visual examination of the Subassembly and the fuel pins indicated their good health. Dimensional measurement on the SA and fuel pins revealed that there is no significant deformation or distortion either on the hex-can or on the fuel pins. Eddy current testing (ECT) and X-radiography did not reveal any defect in the fuel pin clad. Increase in stack length varied from 4.07 to 5.32 mm (i.e. an average increase in stack length of 1.44%). 

The deformation by mechanical creep of the claddings, which tends to decrease the gaps and, therefore, the Doppler effect. 

Deformations should not exceed those which can be accommodated by other connected elements such as partitions, glazing, cladding, services or finishes. In some cases limitation may be required to ensure the proper functioning of machinery or apparatus supported by the structure or to avoid ponding on flat roofs. Vibration may also require limitation as it can cause discomfort or alarm to users of a building and, in extreme cases, structural damage. 

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