How coolers keep nuclear power generators safe
Nuclear power is a significant component in the UK government’s ambition for net-zero carbon emissions. Alongside wind, nuclear power is the lowest carbon electricity source currently available.
Within nuclear power, heat exchangers are essential to maintain operating temperatures. They keep generators running efficiently and ensure nuclear power is able to generate affordable electricity.
Sterling TT produces products for the renewable and low carbon nuclear power industry.
The generation process
Nuclear power generation does not differ greatly from a typical steam plant that uses coal or oil. However, rather than a boiler, there is a nuclear reactor.
Nuclear power harnesses the energy from fission and utilises the steam cycle – as found in most oil and coal fired plants – to produce kinetic energy. This drives near-conventional alternators, producing electricity.
Pressurised water reactor & steam generator
The precise technology to harness the heat energy differs from one manufacturer to another, but the most popular is a pressurised water reactor (PWR). Here, high temperature, pressurised water circulates between the reactor core and a steam generator.
The steam generator is a very specifically designed form of shell and tube heat exchanger. It removes the heat from the water to produce steam in a secondary circuit.
This all takes place within the containment structure designed to isolate and contain all nuclear components.
The steam is then used in much the same way as in a typical thermal plant. It drives steam turbines which are mechanically coupled to electrical alternators.
The entire process is designed to be highly efficient. However, due to the vast capacity of the system, the unwanted heat generated is significant.
Heat exchangers are present to carry the energy flow – such as the steam generator in the reactor. They are also required to reject unwanted heat as it accumulates in the system, such as through condensers, lubrication coolers and alternator coolers.
Older generators circulate an air / hydrogen mix in their cooling system, whilst modern generators use only air.
Hydrogen cooled generators particularly demand precision-made coolers in order to remain gas tight. All generators for this market are physically large.
For example, Sterling TT has manufactured coolers up to 8 meters long for nuclear power clients. Read one of the case studies: hydrogen cooler case study.
Impact of size
The considerable size of generator coolers in large power plants requires specific considerations to control destructive vibrations, the leak potential of both water and hydrogen, and reduced performance from fouling.
The size of coolers for power generators not only impacts the safety of staff assembling the cooler, but also can cause material torsion and twisting.
Because of the potential harm from radiation, the nuclear industry is highly regulated. The closer proximity of the equipment to the reactor, the more stringent the requirements in both design and execution.
In addition, hydrogen coolers for large generators are a small but highly specialised market. Previous experience is essential.
Sterling TT has experience manufacturing most applications within the power generation industry, including in nuclear.