Fourth Generation Nuclear Reactors: Defining Real 21st Century Nuclear Energy
The science and principle of nuclear fission has been known for many decades. Ever since the establishment of the very first nuclear reactor for public use in 1954 at Obninsk, Russia, we have started building and designing nuclear reactors to help us eventually find a way to both end our use of fossil fuels and meet the ever increasing energy demands of our modern world.
True, we are still far from perfecting the technology of harnessing nuclear energy, but we have come a long way. In fact, a couple of decades from now, we might see the development of highly advanced fourth generation nuclear reactors, new powerhouses of energy that are very far from the dangerous and inefficient reactors that we are using today.
Fourth Generation = Advanced Third Generation?
Each generation of nuclear reactors presents different designs and configurations that are usually graded with higher overall efficiencies at each succeeding generation. Today, we are currently using second generation reactors, have been adopting third generation designs, and are well on our way to generation III+ reactors. Unlike previous generations however, fourth generation reactors are not distinctively categorized according to their basic energy generation principle. They can simply be considered as a full-step upgrade to other relatively older designs that have already proven their service reliability.
In other words, there is actually no specific physical design for a fourth generation nuclear reactor; it could simply be a highly advanced version of a generation III or III+ reactor. At the baseline concept however, fourth generation designs must at least adhere to these four basic standards:
- It must be highly economical. Startup and maintenance costs are the primary reasons why nuclear reactors are traditionally costly to build and operate. Fourth generation reactors need to be easier to build, simpler to set up and more uncomplicated to maintain.
- It must be vastly safer to operate. Factors for operational safety are another one of the key concerns whenever reactor designs are considered. A fourth generation reactor should provide simpler but more sound safety mechanisms that would keep its workers from harm and allow the reactor to stay in operation.
- It must produce waste at an extreme minimum. Nuclear reactors actually only use up around 1-3% of the energy available in a fuel rod before it is too irradiated to be used properly. While traditional breeder-type reactors are already capable of recycling spent nuclear fuel, newer fourth generation designs should push the fuel to energy ratio significantly higher than what we can do today.
- It must be proliferation resistant. Technology exploitation has been one of the worst fears in nuclear energy. Terrorists and other independent groups might attempt to use the newly developed nuclear technology for their own personal gain. A fourth generation reactor must at least have a degree of resistance to proliferation to prevent this. For example, a new nuclear fuel that produces very little plutonium (a weapon-grade radioactive element) could be developed.
Sample Fourth Generation Reactors
Of course, even if fourth generation designs are just technically advanced versions of older designs, there is still a considerable amount of distinction that we could classify them into several new configuration types, some of which are:
- Molten Salt Reactor (MSR) – A molten-salt reactor is a type of thermal reactor that uses a salt mixture as the primary coolant or, depending on the specific configuration, as the fuel itself. The fluid molten salt mixture is designed flow into a core made of graphite as the reactor reaches critical mass (as graphite could also be used as a moderator/fission reaction controller). The advantage of this configuration is that it allows cooling at significantly lower pressures and temperatures, which also greatly reduces the risk of failures due to operational complexity. One of the most promising sub-configurations of this design is the reactor that primarily uses thorium instead of uranium as its fuel.
- Sodium-cooled Fast Reactor (SFR) – This fourth generation reactor also omits the use of water as the primary coolant, opting instead to use liquid sodium to regulate the reactor’s temperature. Just like the molten salt reactor, the coolant does not need to be pressurized. What’s unique about its design is the automatic passive shutdown capability of the reactor. In case the fission reaction goes out of control and the reactor overheats, the uranium-plutonium fuel rods (which are also filled with liquid sodium) would simply expand, stopping the fission chain reaction short. Like breeder reactors, its nuclear fuel cycle is closed, meaning that it is capable of reprocessing spent nuclear fuel to be reused again in the reactor.
Though the feasibility of fourth generation designs can be proven by building a prototype, actual commercial use for fourth generation reactors is still far ahead in the future. Like what was mentioned earlier, we are just in the process of testing and adopting generation III+ reactors. We might not see a working fourth generation reactor until at least the year 2030.
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