Nuclear power: keeping to the maintenance plan

Paul Boughton

In the nuclear industry safety is paramount and the design and specification used for equipment involved in generating plants are governed by a series of stringent regulations. Graeme Robertson reports

The maintenance programmes in nuclear generating plants follow strict timetables with only certified contractors permitted to provide products and services, so when it comes to high-voltage motors and generators, it is important to ensure that any repairs are going to make the grade.

Nuclear power generation makes up an important part of meeting the global demand for energy, with 31 countries across the world using over 430 nuclear power plants to meet close to 14% of global electricity demand, a similar proportion to that developed by the hydro industry. With so many people relying on the nuclear industry, it is essential that it operates faultlessly, which means strict adherence to maintenance programmes.

The typical nuclear power plant is segregated between the conventional island and the nuclear island, with the former containing the steam turbine generator and water-cooling systems, which require large high voltage motors to ensure the huge volumes of cooling water are successfully circulated around the plant.

As with any large rotating machine, condition monitoring offers a very useful insight into the performance status as well as the expected service life of the equipment.

Turbines and pumps

The turbine within a nuclear power plant requires considerable support from a number of pumps and motors that ensure the condensate water and cooling water systems are maintained properly. In addition to the regular pumps, auxiliary pumps are required to provide support in the event of a breakdown, ensuring there is always sufficient capacity to maintain safe operation of the plant.

The required capacity of these pumps leads to the majority being powered by high voltage motors and many of them are now in excess of 20 years old. After so many years of continual stress, the regular testing regime can start to indicate problems within the insulation system. Initially, these can be monitored without cause for alarm, but plans for a major overhaul should start to be put in place in order to manage the project effectively and efficiently.

Most equipment of this size contains built-in vibration and temperature sensors to provide live data, while periodic maintenance, inspection and testing can provide some further insight into the integrity of the windings in these machines. Much of this preventative work can be completed by in-house engineers, but in some cases it may be necessary to call in expert engineers to carry out a complete suite of tests and to produce a definitive status report.

Refurbished motor

Since they were originally built, the technology used in the coil insulating systems has moved on considerably, which means that when a complete overhaul is planned, the refurbished motor will not only provide another long period of service, but it can also operate more efficiently, reducing running costs and increasing the return on investment.

Graeme Robertson is head of operations - UK for Sulzer.

Nuclear global capacity must more than double by 2050

The International Energy Agency’s (IEA) new Nuclear Energy Technology Roadmap says nuclear energy allows countries to build scalable, efficient and long-term power sources that can serve as a base to underpin other forms of low-carbon generation.

The report says nuclear global capacity must more than double by 2050, with nuclear supplying 17% of global electricity generation by then, to meet the IEA 2 Degree Scenario for the most effective and efficient means of limiting global temperature rise.

The IEA's report highlights the need for stable, long-term investment frameworks to allow capital-intensive low carbon projects, such as nuclear power plants, to be developed.

The roadmap also emphasises the need for greater certainty in electricity prices, including the cost of carbon emissions.

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