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Details of Grant 

EPSRC Reference: EP/R001618/1
Title: Feasibility of the use of frozen walls in molten salt fast reactors (MSFR-FW)
Principal Investigator: Moulinec, Dr C
Other Investigators:
Emerson, Professor D Merk, Professor B Rolfo, Dr S
Skillen, Dr A S
Researcher Co-Investigators:
Project Partners:
EDF (International) Helmholtz Association National Nuclear Laboratory
STFC Laboratories (Grouped)
Department: Scientific Computing Department
Organisation: STFC Laboratories (Grouped)
Scheme: Standard Research
Starts: 03 July 2017 Ends: 02 July 2018 Value (£): 201,736
EPSRC Research Topic Classifications:
Energy - Nuclear
EPSRC Industrial Sector Classifications:
Energy
Related Grants:
Panel History:
Panel DatePanel NameOutcome
16 Feb 2017 Energy Feasibility 2017 Announced
Summary on Grant Application Form
The overall challenge for the future energy supply is given in UN Goal 7: Ensure access to affordable, reliable, sustainable and modern energy for all is one of the major challenges for the future of human being. The Research Councils UK Energy Research Program describes the problem as the energy 'trilemma' consisting of the challenges to reduce emissions, enhance security of supply, and reducing the cost. Disruptive innovation seems to be the only way to tackle the energy 'trilemma'.

Nuclear reactor technologies have the potential to deliver a promising solution for this challenge. However, the current nuclear energy system is dominated by Light Water Reactors which are not ideal for the required growth in energy production, since their long term operation is not sustainable due to the insufficient use of the natural uranium. The spent nuclear fuel from these reactors still contains ~95% of its original energy content when it is unloaded and considered as waste further on. Making use of the energy content remaining in the spent fuel by closing the nuclear fuel cycle can provide an almost unlimited energy resource. In addition, it can provide a promising use of the Pu stockpile, an unused energetic asset, which is a leftover from the first attempt to achieve a closed fuel cycle in the nuclear system in UK. From an economic point of view, the Pu stockpile is seen as burden due to the requirement of safeguarded storage. Pu utilization could transform this still existing energetic asset into an economic asset.

The objective of this feasibility study is to assess the applicability of frozen wall technology to molten salt fast reactors which is a key technology for this kind of highly innovative reactors. The core of molten salt reactors is designed such that there are no internal vessel structures and that the fuel dissolved in the salt to achieve a critical mass therein. The fuel is pumped through a number of external heat exchangers to extract the heat to be converted to electrical power. Small quantities of fuel salt are continuously fed and withdrawn from the reactor to allow the separation of unwanted fission products from the salt before being recycled into the core. Consequently, as the fuel salt is liquid, it requires less processing before and after use with smaller on site inventories of fuels and waste. A 3 GWth (1-1.5 GWe) reactor is proposed as a direct burner of the spent nuclear fuel accumulated from 60+ years of nuclear power generation in the UK. Thus, the MSFR is intended as an affordable, reliable and sustainable supply of low carbon electrical power that can convert an economic and social burden into an economic asset.

One of the key technical challenges in developing molten salt reactor concepts is that the molten salt corrosively attacks almost all materials at the operating temperatures expected in the reactor. The high neutron flux expected in the MSFR is also known to embrittle structural materials. This study is intended to determine whether the use of frozen wall technology is feasible method of protecting the reactor vessel from corrosive attack, before we can proceed with further studies of design concepts.

To assess the feasibility of frozen wall technology, numerical models of the turbulent thermal hydraulics of the 3 GWth reactor vessel will be coupled to structural models of the vessel wall and the neutron transport. The coupled models will enable us to make observations of regions where the power production contributes to the temperature of the molten salt, which in turn will influence the temperature at the interface between the salt liquidus and solidus interfaces. We will be able to determine regions of thick and thin frozen film depths in order to specify how much cooling is required to maintain the salt film to protect the materials and to propose design modifications that can stabilise the flow and reduce the influence of strong temperature gradients expected over the reactor height.
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