Visit to VENUS
To make the researchers familiar with some of the large-scale facilities available at SCK-CEN an excursion to the VENUS-GUINEVERE reactor was organized for the interested participants. Given that the groups were limited to 5-6 participants, two sessions were organized after lunch, each taking 1.5 hour.
2.1 VENUS Reactor
The VENUS reactor is an experimental low-power reactor of the “zero-power critical facility” type. It was critical for the first time in 1964 with a water-moderated core. Being a flexible installation, after the first start the VENUS reactor was modified several times in order to better meet the needs in nuclear research. VENUS has been used for the validation of reactor physics calculation codes. These codes are applied to make more efficient use of the core loading during the exploitation of nuclear installations.
In June 2003, SCK•CEN carried out a unique experiment in VENUS. For the first time a fuel assembly, irradiated in a power reactor like Doel or Tihange, was loaded. Because of burning in the nuclear reactor, irradiated fuel contains less uranium than non-irradiated fuel. The difference is called the “burn-up credit”. Since spent fuel can still attain a critical mass, the more accurate the knowledge of the "burn up credit" is, the better and safer the storage and transport of the spent fuel can be designed.
During 2008 and 2009, the VENUS facility was modified in order to allow the experimental programme to start in 2010. These experiments aim to provide an answer to the questions of on-line reactivity monitoring, subcriticality determination and operational procedures in ADS.
2.2 Guinevere experiment
The GUINEVERE project was initiated as a project within IP-EUROTRANS, a programme in the 6th Framework Programme (FP6) of EURATOM. It is devoted to specific experiments for the coupling of an accelerator, a target and a subcritical core, see schematic picture above. A major item to be investigated by these experiments is the validation of the subcriticality monitoring for an ADS since the guarantee of subcriticality is of fundamental importance for the safety of an ADS.
To obtain a fast lead core in the VENUS vessel, all internals were removed and are replaced by a core made of lead and uranium fuel. The fuel is provided by CEA, hence a tight collaboration with french nuclear authority and scientific community is present as well.