RRFM 2009 Transactions - European Nuclear Society

Finally, a new tool was defined and the validation was obtained through several pull tests
performed on dummy sections representative of the element and thorough inspections of
each watergap – see example of inspection with capacitive gauges on figure 10. You can
notice that results are as homogeneous from the most internal to the most external watergap.
watergap
2,50
2,40
2,30
UPPER LIMIT
2,20
2,10
2,00
1,90
1,80
1,70
1,60
1,50
1
32
63
94
125
156
187
218
249
280
311
342
373
404
435
466
497
528
559
mm
590
621
652
683
LOWER LIMIT
measurement points
Figure 10 – Inspection of the watergaps on JHR fuel section using capacitive gauges
3.4. Fabrication of an assembly able to be easily dismantled
For the elements meant for EOLE installation, one requirement was to benefit from an
element able to be easily dismantled in order to measure each plate by gamma-scanning
and to have more precise information about neutron beam. The challenge for AREVA-
CERCA was to design a fuel element almost identical to the others, but that could be
completely dismantled. The main requirements of the end-user were the following:
- Same watergap (1,95 mm) with a tolerance enlarged from 0,30 mm to 0,50 mm,
- Precise positioning of plates in the element and maintaining of their position,
- Assembling and dismantling of the element at least 100 times with a facilitated extraction
of the plates.
Advanced studies were performed during a period of 10 months to find adequate solutions to
each of these specificities. The work consisted in determining a set of solutions for each
requirement, presenting the principles to the end-user to take into account its constraints (a
few materials prohibited like stainless steel in different locations of the element, obstruction
of watergaps as reduced as possible, …) and testing the retained solutions on an inert
dummy at scale 1 to ensure of their adequacy with the given requirements.
At least, a specific design of element was proposed to the CEA, integrating adapted solutions
for each of the specificities requested: for example, specific lateral comb enabling to maintain
the watergap as well as to ensure the precise positioning of plates in the fuel assembly,
surface treated stiffeners to facilitate the extraction of plates, design of a made to measure
assembling tool and so on.
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