th
Proceedings of the 20 International Conference on Nuclear Engineering ICONE20 July 30-August 3, 2012, Anaheim, California, USA
54728 PRELIMINARY DISCUSSION ON LFR FUEL PIN DESIGN: CURRENT STATUS, FUEL MODELING AND OPEN ISSUES Davide Rozzia
Alessandro Del Nevo
University of Pisa-DIMNP Pisa (PI), Italy
[email protected]
ENEA CR-Brasimone Camugnano (BO), Italy
[email protected]
Mariano Tarantino ENEA CR-Brasimone Camugnano (BO), Italy
[email protected]
ABSTRACT The current activity deals with the investigation of the LFR fuel rod conceptual design proposed in the European Lead cooled System project (ELSY) and in the Advanced Lead Fast Reactor European Demonstrator (ALFRED). It has been carried out in the framework of the Lead-cooled European Advanced DEmonstration Reactor (LEADER) Project. Two main objectives are pursued. The first one is to provide a general overview of the fuel rod conceptual design status. The main focus is to point out comments related to the pellet pre-design and the methodologies adopted for the preliminary thermomechanical assessment of the single fuel rod by means of fuel pin mechanic codes. The analysis identifies the pellet parameters still not investigated. The second objective is connected to the analysis of the cladding component. The cladding material is a crucial issue for LFR development. Data on performances of the candidate materials in high temperature lead and under irradiated conditions are not available. Beneficial may be obtained from the proven sodium technology materials tested in lead environment. Indeed, the development of Lead Fast Reactor (LFR) fuel is connected to and depends on the development of Sodium Fast Reactor (SFR) fuel. The activity focuses on the state of qualification of the candidate cladding materials in connection to their applicability in the short-medium term. The Ferritic-Martensitic T91 steel requires a long term qualification process mainly because of lack on fueled rods irradiation campaigns. The materials that in principle could be applicable to LFR in the near term are those that belong to the proven technology (if they withstand lead environment). The proven austenitic steels D9, 15-15 Ti, PNC316, ChS68 and F/M HT9 are briefly discussed.
INTRODUCTION In the framework of European activities, the LFR technology was developed in the FP-6 European Lead cooled System (ELSY) and the subsequent FP-7 Lead-cooled European Advanced DEmonstration Reactor (LEADER) projects. The result of ELSY project is the conceptual design of a 600 MWe pool type lead cooled reactor concept (Smith et al., 2011). Its primary circuit is designed for good natural convection capability, which is achieved by a simple flow path, low core pressure losses, low primary circuit pressure losses and a large vertical distance between thermal centers of the core and SGs. These last components consists of 8 flat-spiral SGs located above the reactor core, each one enclosing coaxially to a primary pump. The coolant flows radially in the SGs in countercurrent with the feedwater. This solution allows high design compactness (Cinotti et al., 2006). The Lead-cooled European Advanced DEmonstration Reactor (LEADER) is an ongoing project (EC-EURATOM, 2010). It starts from the results achieved in the ELSY project with a deep analysis of the hard points of the reactor configuration. It aims to define the main components and systems of a commercial size 600 MWe European Lead Fast Reactor (ELFR) and to realize a conceptual design of a representative scaled down European LFR Technology Demonstrator Reactor named ALFRED (Advanced Lead Fast Reactor European Demonstrator). The present activity is focused on the LFR fuel component. Due to the early stage of development of such item, the paper presents a critical overview of the fuel rod conceptual design with the aim to point out comments related to the pellet predesign and the methodologies adopted for the preliminary thermo-mechanical assessment of the single fuel rod by means of fuel pin mechanic codes. The analysis identifies the pellet
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Copyright © 2012 by ASME
parameters still not defined in the conceptual design discussing their relevance in the nuclear technology. The last part of the paper focuses on the cladding materials outlining their status of qualification and applicability to LFR in the short-medium term. LFR FUEL COMPONENT Status of LFR fuel design LFR conventional MOX fuel is designed on the basis of selected criteria and boundary conditions that include thermal hydraulic, neutron kinetic and chemistry. Table 1 reports the main parameters applied in ELSY (Carlsson, et al., 2010). ALFRED differentiates in the thermal power (130 MWth).
Hexagonal, wrapped with spacer grid FA has been selected for ALFRED core (Mansani, L., 2011). It relies on proven MOX fuel. At present, only the maximum enrichment (30%), the active height (600 mm), and the inner diameter of the annular pellets (2 mm) have been definitively fixed. The core design is still ongoing. Preliminary calculations pointed out that 171 FAs with 2 enriched radial zones pursuit a good flux radial flattening. The preliminary fuel pin concept is given in Fig. 1.
Table 1: LFR Boundary conditions and fuel design criteria. Boundary Conditions
Fig. 1. ALFRED fuel pin preliminary conceptual design.
Lead core inlet/outlet temperature: 400 / 480 °C Lead velocity maximum allowable:
