RRFM 2009 Transactions - European Nuclear Society

considered carefully: (i) maintain the geometry of the fuel core, of the plates and of the fuel
element in order to ensure the same thermo-hydraulic characteristics, (ii) ensure the swaging
criteria, (iV) keep the stiffeners mechanical characteristics and (iiii) keep the current
assembling process.
As a part of the project, the manufacturing costs and delivery schedule of 2 BR2 fuel
elements at Mol by Mid 2010 were took into consideration.
4.1 Mechanical calculations and proposed technical solution
The stiffener geometry, principally the thickness, has to be modified in order to maintain the
mechanical characteristics as well as ensure a perfect insertion of cadmium wires (see figure
3). The Cd wire dimension was selected by BR2. The design modification may avoid any
major change on the fuel plate design.
Figure 3: Fuel section with sheathed cadmium wires
The new stiffener design and the stiffener mechanical characteristics were defined and
validated by a series of specific mechanical tests.
According to our experience on swaging, a technical investigation has shown that the
mechanical modifications do not change the swaging parameters that were already qualified
for BR2.
As a consequence of the stiffener width modification, an analysis of the fuel plate geometry
was performed in order to confirm their correct adaptation to the new design.
Regarding the conventional criteria, some margin was found on plate and fuel dimension to
successfully perform the modification without cost (processing modification…) and safety
impact (thermo-hydraulic cooling aspect on the border edge in between the stiffener and the
fuel area…). Taking into account our quality approach, the margin was validated throughout
a full measurement campaign on existing plates.
Thus, for the new fuel elements design, the border edge aluminium area (AA) and the
stiffener groove edge (D), will remain the same as in the current BR2 fuel element (see figure
4). Most of all, the fuel element geometry will not be modified avoiding any long and costly
safety demonstration and qualification program.
As one of the most critical manufacturing step, a global approach was carried out to validate
the swaging processing phase.
AA
*AREVA-CERCA, a subsidiary of AREVA NP, an AREVA an SIEMENS company
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