THE EUROPEAN LEAD-COOLED EFIT PLANT: AN INDUSTRIAL-SCALE ACCELERATOR-DRIVEN SYSTEM FOR MINOR ACTINIDE TRANSMUTATION-I

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 similar to 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 degrees C to assure a sufficiently large safety margin to lead freezing, and the core outlet temperature was limited to 480 degrees 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 similar to 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-EFIT plant cost has been performed based mainly on experience and engineering judgment. A best estimate (base cost and contingency) of about (sic)890 million, with an overall uncertainty of 22%, has been found.