AGR Technologies for Enabling Molten Salt-cooled Reactor Designs

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

High temperature reactors most commonly use He gas as a coolant. The main disadvantage of gases however is their low, compared to liquid coolants, volumetric heat capacity, which ultimately leads to low reactor power density and hence inferior economics. Molten salts are leading candidates to replace the helium coolant in high temperature reactors due to superior heat transfer properties that would allow substantial increase in the core power density. In addition, operation at high temperature (around 700 C) would lead to high power conversion efficiency and allow the use of the reactor heat for various industrial processes. Moreover, high boiling point of molten salts (>1,200 C) would allow designs that operate at low pressure, which should reduce the cost of the reactor vessel, further contributing to economic attractiveness of the concept. Another common feature of molten salt-cooled high temperature reactor designs is the use of highly robust coated-particle TRISO fuel and a graphite moderator. In combination with chemical inertness and high heat capacity of the salt coolant, these features make excellent safety case.
One of the recently proposed variants of such system is Fluoride salt-cooled High temperature Reactor (FHR). Many options exist for the implementation of the concept which rely on combining different fuel forms, coolant salts and configurations of key components. Only a small fraction of this vast design space has been explored so far. FHRs with certain fuel designs can potentially adopt many features from the Advanced Gas cooled Reactors (AGRs) designed and being successfully operated in the UK for many years. Taking advantage of the existing AGR technology and operating experience would substantially reduce the development costs of FHRs and improve their economic attractiveness.
This project will develop a high thermal power commercial-scale FHR leveraging and adapting existing technology from the AGR, such as refuelling strategy, layout of components and maintenance approaches, as well as adapting the use TRISO particles fuel from the High Temperature Gas-cooled Reactors.
The project will identify the most attractive combination of fuel, salt coolant and core configuration with respect to economic performance and safety.
The project will be led by the University of Massachusetts at Lowell in collaboration with Massachusetts Institute of Technology, University of Cambridge, UK and AREVA as an industrial partner. The US Universities will perform the design space exploration for core and fuel cycle strategies for the base line design, while the University of Cambridge will focus on alternative options with AGR-type fuel configurations. The industrial partner will lead the economic analysis effort and contribute to the development of refuelling and maintenance strategies as well as the safety analysis tasks.

Planned Impact

Fluoride salt-cooled High temperature Reactor concept can potentially become more cost effective alternative to the existing Light Water Reactors for a number of reasons.
- Heat transport properties of molten salts are supperior to those of gases, therefore allowing to achieve similar to LWRs power density.
- Near atmospheric pressure operation, large thermal inertia and chemical intertness of molten salts lead to simpler safety systems with enhanced performance and less costly reactor components.
- High temperature operation allows high power conversion efficiency and possibility of using the heat in energy intensive industrial processes. Both of these features will increase the nuclear energy contribution to global reduction of CO2 emissions.
This project will develop a high power comercial scale FHR design variant which will make use of the UK Advanced Gas Cooled Reactor design features. Leveraging AGR technology and experience will dramatically reduce the development costs, improve the chances and speed up the path to commercialisation of FHRs paving the way to global deplyment.
Success of this and the follow up projects could lead to worldwide dissemination of the UK indiginous AGR technology and expertese, dramaticaly increasing its value, since, currently, the knowledge of AGRs is of little practical use outside the UK. Commercialisation of this type of FHR will create multiple research opportunities for the UK academic community and commercial opportunities for the UK nuclear industry.

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