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The Gas Cooled Fast Reactor Project

Final Report Summary - GCFR (The Gas Cooled Fast Reactor Project)

Fast reactors (FRs) have a unique capability as sustainable energy sources both from the point of view of utilisation of natural uranium resource and minimisation of nuclear waste, as well sharing with other nuclear energy systems the benefits from avoiding production of greenhouse gases. The current interest is in exploring the particular advantages of the gas-cooled fast reactor (GCFR) primarily as an economic electricity generator, with good sustainability and safety characteristics, but also capable of minimising nuclear waste via transmutation of minor actinides. GCFR could also support hydrogen production.

There has been a significant evolution in the goals affecting all nuclear systems in each of the key areas of safety, economics, proliferation resistance and sustainability. These have a particularly important impact on the fast reactors (not just gas cooled fast reactors) but the GCFR characteristics can have advantages that can be exploited in satisfying these goals. At the time of the early GCFR studies the requirements could be summarised as follows:
-High breeding gain and short doubling time required for rapid introduction of FR;
-High power densities and high coolant pressures;
- Commercial FR required on a very short timescale.

The consequence of these requirements was as follows:
- Core technology relied on LMFR development;
- Reactor used thermal reactor technology;
- Development requirements were limited to the extrapolation in the parameters e.g. higher pressures, higher pumping power, and for the core the changes for the gas coolant.

The GFR is one of six reactor concepts selected within the GIF, three of which are dedicated fast reactors that are attractive because of their potential to meet the Gen IV sustainability goal by both dramatically improving the utilisation of fissile material and by substantially reducing the quantity and radiotoxicity of radioactive waste.

The Gen IV goals and their influence on the GFR concept are identified in the GFR system research plan and are summarised as follows:

- Sustainability
This is the key objective for the GFR system. This means full utilisation of uranium resources and calls for the recycling of plutonium, uranium and actinides in a closed cycle.
- Non-proliferation
The necessity to avoid, as far as possible, separated materials in the fuel cycle potentially implies minimising the use of fertile blankets. The objective of high burn-up together with actinide recycling results in spent fuel characteristics (isotopic composition) that are unattractive for handling.
- Economics
A high outlet temperature (850 degrees Celsius or more) is selected for high thermal efficiency, with the use of gas turbine or combined (gas turbine + steam turbine) power conversion cycle and the potential for hydrogen production via the thermo-chemical splitting of water. Gen IV objectives for construction time and costs and design for cost effective decommissioning are also considered.
- Safety
The design objective is for no off-site radioactivity release and it requires effectiveness, simplicity, robustness and reliability of systems and physical barriers. The main development challenges, therefore, are refractory fuels with good fission product retention capability at high temperature (1 600 degrees Celsius or above), the selection of robust structural materials, and the design of effective and highly reliable decay heat removal systems.

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