RRFM 2009 Transactions - European Nuclear Society

Behaviour under conditions representative of JHR normal operating conditions (thermal
hydraulic and neutron flux)
A preliminary test has been carried out in the BR2 reactor in 2005, to validate the behaviour
of representative U 3 Si 2 plates under conditions similar the JHR ones. It consists of a “mixed”
BR2 fuel element, with its 5 inner usual rings (UAlx fuel and AG3N cladding) and an external
ring representative of JHR fuel. The plates were tested during 3 cycles (21 EFPD), with a
maximum power density of 435W/cm3 and BR2 cooling conditions (12m/s). The mean fuel
burn-up in U 3 Si 2 plates at the end of the experiment was 54%. Examinations carried out after
irradiation allowed to conclude that the silicide fuel plates behaved correctly under the
experimental conditions.
In order to complete this previous demonstration, it was decided to qualify the correct
behaviour of the fuel elements under JHR normal operating conditions (OC1) by means of an
experimental in-pile program. It will check that:
- the mechanical integrity of the fuel plates,
- the geometric integrity of the fuel plates and more generally of the whole assembly
are preserved in these conditions (in particular limited deformation under flux of the plates
and of the coolant channels is expected). For this purpose, a dedicated loop has been
designed to be implemented in the BR2 reactor of the SCK-CEN ([9], fig 8).
Fig 8: Artistic view of the EVITA loop in the BR2 reactor and location for JHR element during
irradiation (SCK-CEN)
Central channel
Of BR2 reactor
The in-core of the part of the loop is located in the central channel of the BR2 core (H1
channel). Adaptations have been done to host a JHR element for irradiation campaign at the
specified irradiation conditions.
The program plan is the following:
- previous examinations at fuel element reception at BR2 (geometrical
characterization) in order to obtain a dimension initial state,
- irradiation cycles under specified conditions with inter-cycles examinations of the
plates (visual and fission product release tests),
- post-irradiation examinations (EPI) whose objective is the characterisation of the
final state of the plates (swelling, corrosion of the cladding, levels of deformation).
It will also allow to access to the thermal-hydraulic and mechanical behaviour of the element
under normal operation and to consolidate some of the previous answers given by the test
performed in the BACCARA loop.
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