RRFM 2009 Transactions - European Nuclear Society

3.2. U 3 Si 2 high density fuel plates bending
JHR fuel section is constituted of 8
sizes of plates, bended according to
various radius of curvatures. The
radius of curvature of the most internal
sizes of plates were lower than those
usually manufactured in AREVA-
CERCA (in particular, size # 1 with a
radius of curvature of 22 mm). This
meant that we had to adapt the
bending tool and to develop new
bending parameters enabling to distort
the plate while ensuring a perfect
integrity of the fuel core and no
modification of the global thickness of
the plate.
Fig 8 – Picture of bended JHR plates of
extreme sizes
To do so, a specific study was performed to define the necessary tools to implement. Several
plates in surrogate materials and then in depleted uranium were manufactured and bended
with the retained tool. Detailed inspections were performed on the plates to make sure of
their internal quality (radiography of the plate, metallographic inspection on the entire core
and on the boron insert). For example, figure 9 - metallographic picture on the central zone of
the core on an overbended plate (radius of curvature around 16 mm) – doesn’t show any
crack and deformation.
Size 8 – Most
external size
Size 1 – Most
internal size
Fig 9: Picture of a metallographic inspection – central zone of the plate
These excellent results enabled to validate the modified tools and to install them on the
bending machine.
3.3. Roll-swaging of 8 sizes of plates with a narrow watergap
The aimed watergap by CEA was extremely difficult to achieve considering concentric
assemblies.
The challenge for AREVA-CERCA lied in reaching the low value of 1,95 mm, while
maintaining a limited tolerance of ± 0,30 mm, and this, on seven successive watergaps.
This has conducted AREVA-CERCA to design a new parametering on the roll-swaging
machine with a complete modification of the existing tools.
A complex study has been launched to define a tool that would enable to perform the
operation and to check the manufacturing reproducibility on each watergap. Following
parameters were particularly studied: the accurate positioning of the plates inside the
element, the shape of the roll-swaged wheels, …
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