Development of versatile liquid metal testing facility for lead-cooled fast reactor technology

Liquid-metal-cooled nuclear reactors are advanced nuclear reactor designs where the primary coolant is a liquid metal, such as sodium, lead or a lead-bismuth mixture. The excellent heat transfer properties of liquid metals, and the possibility to operate liquid metal reactors at ambient pressure and very high temperature, are the main advantages of liquid metal cooled reactors with respect to water-cooled reactor designs. These advantages result in smaller and much safer reactor designs, particularly suited for small-modular construction.
Originally developed for marine propulsion, liquid-metal-cooled nuclear reactors are currently being investigated for power production. In particular, two out of the six nuclear reactor designs identified by the Generation IV International Forum and currently being researched for near-term commercial application are liquid metal reactors: the sodium-cooled fast reactor and the lead-cooled fast reactor.
The present research study, in particular, is focused on the lead-cooled fast reactor technology. Lead-cooled nuclear reactors will be deployed in small and modular units featuring long-life, pre-manufactured cores that can run for several years before being replaced, thus making these reactors also suitable for emerging and developing countries that do not plan to build their own nuclear infrastructure. The excellent heat transfer capabilities of liquid lead, together with its high boiling point, assure that decay heat after reactor shutdown can be safely dissipated with entirely passive means, thus resulting in a particularly safe nuclear reactor design. Lead is also very dense and therefore a good shield against gamma radiations, which is a bonus for protecting the operators and the environment. Unlike sodium that burns in contact with air and that can explode in contact with water, lead does not react significantly with either air or water, allowing simpler and cheaper system design and a safer plant operation.
Currently, the main drawback of the lead-cooled nuclear reactor technology is the very limited knowledge of erosion and corrosion of materials exposed to liquid lead at temperatures representative of nuclear reactor operation. This is the knowledge gap that the present research aims to address: erosion and corrosion tests will be carried out in liquid lead at nuclear reactor operating conditions to identify the most promising materials to realize the reactor structural components. High-fidelity CFD simulations of the experimental setup, will first assist with the design of the experimental facility and then provide the missing information on the local flow and thermal fields, necessary to fully understand the implications of the experimental data and apply the experimental findings more widely to corrosion/erosion analysis of lead-cooled reactors.
Additionally, the present research will also develop an imaging technology based on ultrasounds to inspect the reactor internals during operation. Liquid metals, in fact, are opaque and conventional imaging techniques therefore not applicable. The possibility to periodically inspect the reactor internals is essential for safe and profitable operation.

Two of the main cornerstones of the UK energy policy are energy security and environmental sustainability. The UK is committed to reducing carbon emissions to 80% of their 1990 levels by 2050. The UK is decarbonising its economy with a reduction of 42% in carbon emissions while at the same time increasing its GDP by 67% (period 1990-2016). This is accomplished by replacing electricity production from fossil fuels with production from low carbon emission and renewable sources. A key point, highlighted in the Government's "Clean and Growth Strategy", is to diversify to different types of clean technologies to strengthen the power generation sector. Nuclear energy plays an important role in this energy mix to further decrease the carbon footprint of electricity production, as evidenced by the UK Government's investment in a 3.2GW nuclear power plant at Hinkley Point C, expected to supply 7% of the UK electricity demand.
The long-term disposal of spent nuclear fuel from past and current generation reactors remains a long term issue, as a solution based on deep geological disposal facilities finds little support from local communities. The UK also currently stores civilian stockpiles of separated plutonium. The proposed research supports the development of Generation IV, innovative fast reactor designs, which can use spent fuel from current reactors and also separated plutonium, thereby providing a more sustainable solution to the problem of spent fuel, as well as carbon-free power generation. These reactor designs are also relevant to naval propulsion, an area where UK needs to retain its expertise and industry. The proposed research, in the short term supports the development of lead cooled reactors by advancing current understanding of lead's corrosive characteristics, and in the longer term through facilitating the development of reliable turbulence models for the efficient and fast simulation of lead cooling processes.
Moreover, the proposed research, through its generation of high-fidelity data for low-Prandtl number thermal processes, will a) extend knowledge on the characteristics of the poorly-understood low-Prandtl-number heat convection and b) enable the development of more reliable simulation methods for heat convection in high-conductivity liquids. The proposed research thus has a fundamental scientific impact as well as impact in the more applied topic of a lead-cooled reactor design.