RRFM 2009 Transactions - European Nuclear Society

The main characteristics of the IRIS4 fuel plates are summarized in table 1. The length, width
and thickness of the IRIS4 plates are identical to previous IRIS experiments ones,
respectively close to 641 mm, 73 mm, 1.30 mm. The fuel plate inspections, such as
metallographic examinations, X-ray diffraction, blister tests, indicated that the plates met the
usual OSIRIS specifications.
Plate ID
Matrix
composition
Mo/UMo
(wt%)
235 U/U
(%)
U total
(g)
U density
(gU.cm -3 )
Mean plate
thickness
(mm)
Porosity
(%)
U7MZ
8043
Al + 2.1
wt% Si
19.78 131.3 7.7 1.31 3.8
U7MZ
8044
U7MZ
8053
U7MZ
8054
Al + 2.1
wt% Si
7.3
19.78 129.7 7.9 1.31 1.1
Pure Al 19.75 131.3 7.8 1.30 2.4
Pure Al
19.75 131.3 7.7 1.30 4.5
Table 1: Characteristics of IRIS4 oxidised UMo plates
From a microstructural point of view [12], the fuel meat presents a typical shape of rolled
plate made of atomised particles (cf. Fig.1a) with a homogeneous meat thickness. Some
UMo particles interpenetration can not be avoided due to the high uranium density and the
rolling process, leading up to some local cracks in the oxide layer. Such fuel characteristics
must be kept in mind for the on-going irradiation and further PIE, notably in the case of the
plates with Al added with Si, where Si can play its recognised protective role.
Fig. 1a and 1b : As-fabricated cross-section of IRIS4 plate (left) and
detail of as-fabricated IRIS4 microstructure (right)
3. Irradiation history
The irradiation of the four plates is being carried out in the IRIS device loaded in the OSIRIS
reactor at the core cell #52 which was already the irradiation position of the IRIS2 experiment
(cf. Fig. 2). This position leads to a slight flux gradient between the 2 most irradiated objects
(plates 8044 and 8053) and the 2 less ones situated in the inner part of the IRIS device
(plates 8043 and 8054) as illustrated by Fig. 2. The irradiation has started in October 2008
and should last up to reach a minimum of 50% 235 U, expected by mid-2009.
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