OMICO: Oxide fuels: Microstructure and Composition variations (2001-2007)

The project OMICO incorporated several challenging objectives on nuclear fuels, requiring technological developments in various areas. The complexity of some of these technological developments was initially overlooked and/or their extent was underestimated, leading to substantially higher expenses at the research institutes JRC/ITU for manufacturing and SCK•CEN for irradiation than originally foreseen and a substantial delay of the project (66 months instead of the original estimate of 36 months).

Despite its difficulties, OMICO did achieve important successes as well:

• The experimental OMICO assembly had to be calculated in a three dimensional approach. At the time of start of the OMICO project, 3D Monte Carlo calculations were not yet established for the complex core of the BR2 reactor. The thorough cross-checks with the conventional 2D approach, comparison with reference programs and the irradiation of a dummy assembly contributed to the confidence in the MCNP modelling of complex experiments in the BR2 reactor, and are today common practice.

• Fuel manufacturing to tight LWR specifications demonstrated once again ITU's key role as an independent experimental fuel manufacturer in Europe, and the OMICO programme has extended the core competence of this laboratory to heterogeneous (Th,Pu)O2 and UO2 fuels.

• In terms of fuel performance data, the OMICO experiment fully achieved the goals with respect to the acquisition of thermal data (power vs centreline temperature data set). The unfortunate loss of the instrumented rods after five cycles didn't allow us to address the dynamic evolution of fission gas release through on-line measurements, but through two dedicated irradiation cycles on the non-instrumented rods, one of which contained a mild transient, allowed to recover in part the objective of fission gas release.

Samples from the OMICO program will further be subject to detailed post-irradiation examinations by different laboratories throughout Europe. The detailed examinations will include further optical microscopy, detailed EPMA, radiochemical work, Secondary Ion

Mass Spectrometry etc. These analyses are part of the Sixth Framework programme LWR-DEPUTY.

Website

• www3.sckcen.be/omico

Contact person(s)

Verwerft Marc