Regulatory Aspects and Siting
Reactor Safety - Passive Safety Systems
Passive Decay Heat Removal
In case of accident, the core needs to be cooled. The core geometry coupled with the pebble power density is optimized to ensure efficient removal of heat. This coupled with the high temperature resistance of the TRISO particles and the high heat capacity of the pebbles allow for efficient cooling through natural convection and radiation.
An external component providing natural convective circulation of air or water in case of accidents can also be used through a Reactor Cavity Cooling System (RCCS).
This simplified passive heat removal decreases drastically the number of pipes made for emergency cooling that could break, or the number of pumps that are impacted by a loss of power.
Negative Temperature Reactivity Coefficients
The fuel and coolant temperature coefficients are strongly negative, which ensure that when the core temperature increases, the reactivity naturally decreases. The power then decreases, naturally bringing the temperature down to a safe value.
TRISO particle fission products retainment: TRISO particles can handle a temperature of 1800 degrees Celsius, far above the operational temperature and provide a barrier avoiding releases. In the event of an accident, this resistance coupled with the negative reactivity coefficient makes fuel melt physically impossible.
Speeding Up the Licensing
All those passive safety system ensure the safe operation or shutdown of the reactor without the need of electricity or operators. This enhances the overall safety of the system while making the design simpler. The demonstration of safety is then less complex, requires fewer steps, which should make the Pebble-Bed reactor faster to license.
Defense in Depth
Defense in depth is implemented primarily through the combination of a number of consecutive and independent levels of protection that would have to fail before harmful effects could be caused to people or the environment.
Depressurization Accident
In the event of a loss of pressure in the reactor, the nuclear chain reaction stops on its own due to fuel temperature limitations.
Overpressure
The pebble that contains the fuel experiences stress when it is exposed to radiation. The pebbles are coated with a protective layer to be able to withstand these stresses so that it will not fail. This ensures that the radiation is contained within the pebble during normal and accident conditions.
Irradiation Induced Cracking
Irradiation induced cracking is a form of corrosion that occurs when a material is exposed to radiation. The radiation causes the coating on the pebble to shrink. Extensive research has been committed to improving the coating to prevent excessive shrinkage.
Loss of Coolant
In the event of a loss of Helium coolant due to piping ruptures, the heat produced by the core will be removed by heat dissipation from the reactor pressure vessel. Therefore the fuel will not fail.
Site Selection
Environmental Assessment
Evaluate the impact of the reactor on the environment. All large infrastructure projects require an EA prior to construction. The EA would assess the weather patterns, geology and natural hazards in the area.
An EA has been completed for the extraction of oil and contains a lot of background data for the project. The EA can be found here.
Emergency Response
Nuclear Reactors require sophisticated emergency response plans with the well being of people, animals and the environment at their core. Working alongside the oil extraction means that there are highly trained and competent safety professionals including fire fighters, medical professionals and OSH professionals available to react to emergencies.
Mining Induced Hazards
Being co-located with mining poses some additional hazards- such as fires, flooding, seismic disruptions, and other geological instabilities. For this reason, policies and safety measures will be updated to ensure hazards are minimized and workers are kept safe.
Severe Weather
Forest fires are becoming more common on the plains in Canada. The reactor is walk-away safe and due to normal high temperatures in operation is able to handle the intense temperatures of a forest fire.
Flooding
Due to ice damming on the Athabasca River, flooding is a common spring occurrence. The nuclear reactor would be situated out of the flood plain.
Grid Infrastructure
Electrical grid infrastructure would need to be developed or improved to effectively use the electricity generated by the reactor. Alberta has had a lot of success with these types of projects.
Property Rights
The reactor would be a joint venture between the oil company and the Province of Alberta, as the majority of titles are held by oil companies in the Athabasca basin.
Measures for Site Protection
Siting Considerations
The minimum safe operating distance between the plants will be at least 100 meters, depending on the industrial safety factors of the facilities. In addition, the SMR's control room would be separated from the rest of the plant, so that it would be further away in the case of an accident. The nuclear site would also have protective structures in place to withstand aircraft crashes or earthquakes.
Monitoring
An active environmental monitoring program will be developed to ensure no releases exceed regulatory limits. This will include monitoring of airborne and liquid releases.