C. Artioli

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 [approximately]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 [approximately]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 €1890 million, with an overall uncertainty of 22%, has been found.

Feasibility Studies and Scope Analyses for a SUPERSTAR Demonstrator Neutronics Design

A preliminary feasibility study and scope analysis for a demonstrator (demo) of the SUstainable Proliferation-resistance Enhanced Refined Secure Transportable Autonomous Reactor (SUPERSTAR) has been performed. Preliminary core design studies have been carried out focused on maximizing the power level compatibly with natural circulation cooling and transportability requirements, while meeting the foremost goals of (i) providing energy security and proliferation resistance thanks to a long life core design, (ii) minimizing the reactivity swing over the fuel lifetime, and (iii) flattening the radial power profiles, as demanded by the choice of wrapper-less fuel assemblies and by the stringent technological constraints imposed by the short-time-to-deployment feature. Once established appropriate geometrical pin and fuel assembly specifications, a suitable active height allowing the system to be cooled by free-flowing lead has finally been set through parametric T/H analyses. Fuel cycle calculations have been then performed to optimize both the fresh fuel composition and the radial enrichment zoning. Moreover, the use of several absorbing materials has been investigated in order to guarantee enhanced safety by incorporating control elements having a net density greater than that of the surrounding lead coolant. A complete static neutronic characterization of the resulting core has been finally accomplished.

A Simplified Model for a Preliminary Study of the Dynamic Behaviour of a Small Gen IV LFR DEMO

The Lead Cooled Fast Reactor (LFR) is one of the six concepts selected by the Generation IV International Forum (GIF) as candidates for the long term evolution of nuclear technology. Due to the significant technological innovations it implies, the European Sustainable Nuclear Energy Technology Platform (SNETP) recognized that LFR complete development requires the realization of a demonstration plant (DEMO) as a fundamental intermediate step. In this paper, a preliminary approach to the simulation of DEMO primary system dynamic behavior is presented. The need of investigating reactor responses to temperature transients has led to a simplified model reckoning with all the main feedbacks following a reactivity change in the core, which have been calculated by means of ERANOS deterministic code ver. 2.1 coupled with JEFF3.1 data library. A lumped-parameter approach has been adopted to treat both neutronics and thermal-hydraulics: indeed, the point-kinetics approximation has been employed and an average-temperature heat-exchange model has been implemented. Due to the latter, the dynamic mechanical behavior of DEMO core — modeled as a cylinder — has been addressed by considering expansions and contractions instantaneous with temperature variations, i.e. neglecting mass inertia effects. The very simple linearized model treated in the present work turns out to be a helpful tool in this early phase of the DEMO pre-design, in which all the system specifications are still considered to be open design parameters, since it allows a relatively quick, qualitative analysis of dynamics and stability aspects that cannot be left aside when refining or even finalizing the system configuration.Copyright