Analysis of transients and severe accidents in accelerator driven transmuters (ADTs) of the 800 MWth class with fertile-free fuels

In the FUTURE Program, the development and application of fertile-free fuels for Accelerator Driven Transmuters (ADTs) has been advanced. To assess the reactor performance and safety behavior of an ADT with so-called dedicated fuels, various transient cases for an 800 MWth-class Pb/Bi-cooled ADT were investigated by using the SIMMER-III code. The FUTURE ADT also served as vehicle to develop and test ideas on a safety concept for such transmuters. Two fuels, a CERCER fuel with an MgO matrix and a CERMET fuel with a Mo-92 matrix, were chosen. The transient scenarios shown here are: spurious beam trip (BT), unprotected transient over current (UTOC), unprotected transient over power (UTOP), unprotected loss of flow (ULOF) and unprotected blockage accident (UBA). Since the release of fission gas and helium after cladding failure could induce a significant positive reactivity, the gas-blowdown was investigated for the transient scenarios. The present analyses showed that power excursions could be avoided by the fuel sweep-out from the core under severe accident conditions. (author)