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In order to reduce the volume and the radiotoxicity of the nuclear waste coming from the operation of existing pressurized water reactors, accelerator-driven systems (ADSs) have been envisioned. The Lead-Cooled (Pb) European Facility for Industrial-Scale Transmutation (EFIT) (Pb-EFIT) plant is the first ADS design that has been going into a rather detailed engineering level. It is a lead-cooled, 385-MW(thermal) ADS prototype for minor actinide (MA) transmutation designed to achieve an optimal MA destruction rate of ~42 kg/TW⋅h(thermal). The spallation target unit is located in the center of the diagrid where 800-MeV protons from the accelerator impinge on a free surface of lead exposed to vacuum. The core inlet temperature was set at 400°C to assure a sufficiently large safety margin to lead freezing, and the core outlet temperature was limited to 480°C to allow acceptable corrosion. The ferritic-martensitic 9% Cr steel T91 protected against corrosion with alumina FeCrAlY [GESA (Gepulste Elektronen Strahl Anlage) treatment]. The primary circuit is designed for effective natural circulation, i.e., relatively low pressure losses, and the design offers good protection for a heat removal system in case of a blackout accident. The EFIT plant is designed to have a low likelihood and a low degree of core damage, to eliminate the need for off-site emergency responses in case of a severe accident, to use an extensively reliable passive safety system to fulfill the safety functions, and to eliminate the need of alternating-current safety-grade power (no safety-grade diesel generator). Three systems contribute to the decay heat removal (DHR) function of Pb-EFIT: the steam generators, the direct reactor cooling system, and the isolation condenser system. The EFIT plant exhibits four primary pumps; eight steam generator units, each rated at 52 MW, provide heat removal under normal operation. On the secondary side, the water steam ensures a thermal efficiency of ~40% with the superheated vapor secondary circuit, taking into account the electricity required by pumps (from both the primary circuit and the secondary circuits) but without deducing the power required for the accelerator. An estimate of the Pb-EF1T plant cost has been performed based mainly on experience and engineering judgment. A best estimate (base cost and contingency) of about 1890 million, with an overall uncertainty of 22%, has been found. [ABSTRACT FROM AUTHOR]

Abstract: Plutonium recycling in new-generation fast reactors coupled with minor actinides (MA) transmutation in dedicated nuclear systems could achieve a decrease of nuclear waste long-term radiotoxicity by two orders of magnitude in comparison with current once-through strategy. In a double-strata scenario, purpose-built accelerator-driven systems (ADS) could transmute minor actinides. The innovative nuclear fuel conceived for such systems demands significant R&D efforts in order to meet the safety and technical performance of current fuel systems. The Integrated Project EUROTRANS (EUROpean research programme for the TRANSmutation of high level nuclear waste in ADS), part of the EURATOM Framework Programme 6 (FP6), undertook some of this research. EUROTRANS developed from the FP5 research programmes on ADS (PDS-XADS) and on fuels dedicated to MA transmutation (FUTURE, CONFIRM). One of its main objectives is the conceptual design of a small sub-critical nuclear system loaded with uranium-free fuel to provide high MA transmutation efficiency. These principles guided the design of EFIT (European Facility for Industrial Transmutation) in the domain DESIGN of IP EUROTRANS. The domain AFTRA (Advanced Fuels for TRAnsmutation system) identified two composite fuel systems: a ceramic–ceramic (CERCER) where fuel particles are dispersed in a magnesia matrix, and a ceramic–metallic (CERMET) with a molybdenum matrix in the place of MgO matrix to host a ceramic fissile phase. The EFIT fuel is composed of plutonium and MA oxides in solid solution with isotopic vectors typical of LWR spent fuel with 45MWd/kgHM discharge burnup and 30years interim storage before reprocessing. This paper is focused on the thermomechanical state of the hottest fuel pins of two EFIT cores of 400MW(th) loaded with either CERCER or CERMET fuels. For calculations three fuel performance codes were used: FEMALE, TRAFIC and TRANSURANUS. The analysis was performed at the beginning of fuel life. Presented results were used for testing newly-developed models installed in the TRANSURANUS code to deal with such innovative fuels and T91 steel cladding. Agreement among codes predictions was satisfactory for fuel and cladding temperatures, pellet-cladding gap and mechanical stresses. [Copyright &y& Elsevier]