Lead-cooled system design and challenges in the frame of Generation IV International Forum

doi:10.1016/j.jnucmat.2011.04.042

Journal of Nuclear Materials

Volume 415, Issue 3, 31 August 2011, Pages 245-253

https://doi.org/10.1016/j.jnucmat.2011.04.042 Get rights and content

Abstract

The Generation IV International Forum (GIF) Technology Roadmap identified the Lead-cooled Fast Reactor (LFR) as a technology well suited for electricity generation, hydrogen production and actinide management in a closed fuel cycle. One of the most important features of the LFR is the fact that lead is a relatively inert coolant, a feature that conveys significant advantages in terms of safety, system simplification, and the consequent potential for economic performance.

In 2004, the GIF LFR Provisional System Steering Committee was organized and began to develop the LFR System Research Plan. The committee selected two pool-type reactor concepts as candidates for international cooperation and joint development in the GIF framework: these are the Small Secure Transportable Autonomous Reactor (SSTAR); and the European Lead-cooled System (ELSY).

The high boiling point (1745 °C) of lead has a beneficial impact to the safety of the system, whereas its high melting point (327.4 °C) requires new engineering strategies, especially for In-Service-Inspection and refuelling. Lead, especially at high temperatures, is also relatively corrosive towards structural materials. This necessitates that coolant purity and the level of dissolved oxygen be carefully controlled, in addition to the proper selection of structural materials.

For the GIF LFR concepts, lead has been chosen as the coolant rather than Lead–Bismuth Eutectic primarily because of its greatly reduced generation of the alpha-emitting ²¹⁰Po isotope formed in the coolant. This results in significantly reduced levels of radioactive contamination of the coolant while minimizing the effect of decay power in the coolant from such contaminants; an additional consideration is the desire to eliminate dependence on bismuth which might be a limited resource.

This paper provides an overview of the historical development of the LFR, a summary of the advantages and challenges associated with heavy liquid metal coolants, and an update of the current status of development of LFR concepts under consideration. The main characteristics of the SSTAR and ELSY systems are summarized, and the current status of design of each system is presented. Because of the significant recent efforts in the ELSY system design, greater emphasis is placed on the ELSY plant, with focus on the technological development and design provisions intended to overcome or alleviate recognized drawbacks to the use of heavy liquid metal coolants. In the case of the SSTAR system for which development has proceeded more slowly, a more limited summary is provided. It is noted that both systems share many of the same research needs and objectives thus providing a strong basis for international collaboration.

Introduction

The development of the combined technologies of fast reactors and their associated closed fuel cycles has the potential to increase by a factor of about up to 100 the energy output from a given amount of uranium (through full use of U238), while enabling enhanced approaches to the management of high level radioactive waste through the transmutation of minor actinides. The resulting fast reactor systems are therefore potentially able to provide energy for the next thousand years with the currently known uranium resources.

R&D on the most promising concepts is currently being coordinated at the international level through initiatives such as the “Generation IV International Forum” GIF [1]. The European Community (EC), through the Sustainable Nuclear Energy Technology Platform (SNETP), has defined its own strategy and priorities for fast neutron reactors that are the most likely to meet Europe’s energy needs in the long term in terms of security of supply, safety, sustainability and economic competitiveness [2].

The application of lead technology to nuclear energy had its start in the Soviet Union in the 1950s where nuclear systems cooled by Lead–Bismuth Eutectic (LBE) were developed and deployed for submarine propulsion. More recently, attention to heavy liquid metal coolants for reactors has arisen in several countries around the globe as their advantageous characteristics have gradually become recognized. Moreover the features and the associated technologies of heavy liquid metal coolants inspired several projects in the emerging field of Accelerator Driven System (ADS), and in particular lead and LBE have been considered as both coolants and neutron spallation targets for several such projects under development throughout the world.

In 2004, the Lead Fast Reactor (LFR) Provisional System Steering Committee (PSSC) was organized to develop the LFR System Research Plan (SRP). The committee selected two pool-type reactor concepts as candidates for international cooperation and joint development in the GIF framework: these are the Small Secure Transportable Autonomous Reactor (SSTAR) [3]; and the European Lead-cooled System (ELSY) [4].

In evaluating and planning research for these LFR concepts, the LFR–PSSC has followed the general aims of the Generation IV Roadmap; thus, efforts have focused on design optimization with respect to sustainability, economics, safety and reliability, and proliferation resistance and physical protection.

The needed research activities are identified and described in the SRP. It is expected that in the future, the required efforts could be organized into four major areas of collaboration and formalized as projects. The four areas are: system integration and assessment; lead technology and materials; system and component design; and fuel development.

In 2006 the EC partially funded, within the Euratom Framework Programme 6 (FP6), the ELSY project, conducted by a large consortium of European organizations to demonstrate the feasibility of designing a competitive and safe lead fast critical reactor using simple engineered features, while fully complying with Generation IV goals.

The ELSY project was completed in February 2010, but follow-on LFR development will continue within the Lead-cooled European Advanced DEmonstration Reactor (LEADER) project. The LEADER project will be built on the ELSY results with the objective to finalize the design of a large size LFR and to develop the conceptual design of a down-scaled demonstrator.

ELSY in fact is part of an extensive R&D program related to heavy-metal cooled systems involving FP5, FP6 and FP7. These efforts were initiated in FR5 with the development of the Accelerator Driven System. In the 6th FP these efforts were extended with the development of the critical system ELSY, the subcritical system IP-EUROTRANS and the development of basic technology by establishing the Virtual European Lead Laboratory (VELLA). The efforts now continue in the 7th FP with the further development of critical systems (LEADER), a subcritical system (CDT) and basic lead technology (GETMAT, HeLiMnet).

Section snippets

The heavy liquid metal coolants

Lead–Bismuth Eutectic-cooled reactors were developed and built in the Soviet Union as naval submarine propulsion reactors and supporting land prototypes. However, those reactors were strictly for military purposes. There has never been a LFR demonstration or prototype for commercial purposes.

Heavy Liquid Metal Coolants (HLMC) have several properties which, if properly exploited by the designer, together with specific design features, can potentially reduce the plant cost and improve safety (see

SSTAR LFR design

A critical issue for all designers has been the design of structures able to accommodate the mechanical loads, especially in seismic conditions, resulting from the use of a coolant with very high density (Table 1, column h). SSTAR can overcome this issue thanks to the small size; in fact the current reference design for the SSTAR in the United States is a 20 MWe natural circulation reactor concept with a small shippable reactor vessel (Fig. 1).

It should be noted that the genesis for the SSTAR

ELSY design

The ELSY project is aimed at demonstrating the possibility of designing a competitive and safe fast critical reactor using simple engineered features, whilst fully complying with the Generation IV goals of sustainability, economics, safety, proliferation resistance and physical protection [7], [8], [9].

ELSY is an ambitious project; several challenging design provisions had in fact to be developed to face expected issues and new ones, discovered in the course of the project activity, related to

Conclusion

This paper provides a description of the current status of development of the major LFR reactor concepts in the frame of Generation IV International Forum, including their design characteristics and approaches to overcoming the challenges associated with heavy liquid metal coolants. We believe that the SSTAR and ELSY concepts incorporate a variety of innovative approaches to address these challenges in delivering viable LFR designs. The results to date indicate that the LFR is a very promising

Acknowledgments

The work on LFR in GIF is supported by the European Commission through the Euratom Framework Programmes, by the U.S. Department of Energy Generation IV Nuclear Energy System Initiative and by the Tokyo Institute of Technology. The ELSY, CDT and IP-EUROTRANS consortia in Europe are coordinated by Ansaldo Nucleare, SCK-CEN and KIT respectively.

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