Balance of plant | Emergency backup generators

The power behind power

6 October 2010

Emergency diesel backup generators are vital for safety; every nuclear power reactor has at least two of them. So as new-build begins to take off and the market for replacements heats up, suppliers are gearing up and battling for orders. By Claire Maden

Within a nuclear power plant, emergency diesel backup generators (EDBGs) are a vital part of plant safety systems. In normal operation, a nuclear plant produces the power needed to operate its coolant circulation system and other safety critical systems. In the event that power from the plant itself, or from the electricity grid, should not be available, EDBGs spring into action to ensure that coolant circulation is maintained and the reactor can be safely shut down. So crucial are EDBGs that every nuclear reactor has at least two of them, ready to start at a moment’s notice.

As well as being present in duplicate to ensure redundancy at all times, nuclear power plant EDBGs are subject to rigorous regulatory control to ensure their availability and reliability. They must meet strict technical requirements, typically being able to reach their rated voltage and frequency within ten seconds of startup.

Standards are set by national bodies and codes including the IEEE, ASME (USA), RCCE and RCCM codes (France), the CSA (Canada), KTA (Germany), GOST and ROSTECHNADZOR (Russia) and YVL (Finland). The Institute of Electrical and Electronics Engineers (IEEE) Standard 387-1995 is a benchmark that is widely referenced for principal design criteria and qualification and testing guidelines, to ensure that generators meet performance requirements.

After installation, EDBGs must pass frequent and stringent tests as prescribed by the relevant national regulator to ensure their availability and reliability. The US Nuclear Regulatory Commission, for example, requires each EBDG to be started up and loaded at least once every 31 days, with additional tests required at six-monthly intervals, plus further extensive tests at every refuelling outage (or at least once every two years). Once every ten years, when the plant is in outage, the NRC requires all redundant EBDG units to be started simultaneously in order to identify any common failure modes that have gone undetected in tests of the single units.

Diesel pedigrees

EDBGs in use in nuclear power plants around the world are typically small capacity (1MW to 25MW) medium-speed four-stroke diesel engines, started by compressed air. Most of the major diesel generator manufacturers that are actively promoting their EDBGs for use in nuclear power plants today can trace their pedigree back over many decades, often to diesel engines developed initially for marine propulsion or railway locomotives. The much talked-of nuclear renaissance, and the ever approaching likelihood of new orders for nuclear plants, has led to a trend for increasing internationalisation in the nuclear component supply industry, and EDBGs have been no exception.

Alstom Power, working through a consortium with MAN Diesel SE, claims to be the world leader in the supply of EDBGs, having installed over 50% of the world’s integrated EBDG packages for nuclear reactors over the past decade. The company boasts a history of 31 projects on 50 reactors around the world, including power plants in China, Korea, India, Africa and Europe. MAN Diesel & Turbo bills itself as the world market leader for large diesel engines, designed and manufactured both by the company itself and by its licensees around the world. The Germany based company acquired French diesel engine manufacturer SEMT Pielstick SA, in 2006.

Alstom offers EBDG packages based on MAN Diesel’s PA6-B engine, providing 3-7MW of power generating up to 7MWe, and its PC2-6B engine, offering up to 15MW and generating up to 9MWe. They can reach their rated speed and voltage within ten seconds of start up. Alstom offers EBDG packages based on MAN Diesel’s PA6-B engine, providing up to 7 MWe, and its PC2-6B engine, offering up to 9 MWe. They can reach their rated speed and voltage within ten seconds of start up. . Its EDBGs are certified for nuclear use in countries including China, the USA, France, India, Japan and Korea. With an eye to the Chinese market, with its project localisation requirements, Alstom Power has set up facilities in Wuhan through which it is working to supply its generators to the country’s burgeoning nuclear power sector.

Current projects include the supply of 35 EDBGs for Chinese nuclear power plants and four engines for both the Olkiluoto 3 and Flamanville 3 EPRs in Europe (see Table 1). Alstom has also, over the past decade, delivered integrated packages to various types of power plants including PWRs, PHWRs (Qinshan 1&2, China), ABWRs (Lungmen 1&2, Taiwan) and VVERs (Tianwan 1&2, China and Kudankulam 1&2, India).

South Korea’s Doosan Engine Co is licensed to produce MAN Diesel’s engines and is likely to play an increasingly important role in supplying EDBGs to nuclear new build projects. Doosan Engine forerunner Hanjung signed a technical licence contract with SEMT Pielstick (now part of the MAN Diesel Group) to produce its four-stroke medium speed diesel engine in 1984 and has supplied EDBGs to all of South Korea’s nuclear power plants that have started up since 1990. South Korea’s earliest nuclear power plants were of course built by foreign suppliers under turnkey contracts; subsequent plants were built with input from South Korea’s evolved industry. PC2.5 engines have been delivered for Shin Kori 1&2 and Shin Wolsong 1&2, while PC2-6B engines are being supplied by Alstom for Shin Kori 3&4, the first-of-a-kind third generation APR-1400 reactors.

Another long-established diesel generator manufacturer, Wisconsin-based Fairbanks Morse Engine has been supplying diesel generators to the North American nuclear power industry since 1968, with 104 units installed at 38 reactors in the USA and one in Canada. It offers four types of generator set to the nuclear industry: the Colt-Pielstick PC2 series, with an output range of 5.6-14.5MWe; the Colt-Pielstick PA6-B (2.0-6.8MWe) (both manufactured under licence from MAN Diesel); the Opposed Piston 38 8 1/8 (1.5-3.0MWe); and the Alco 251F (0.7-2.7MWe).

In April 2010, the company signed contracts to supply six emergency diesel generator sets to Toshiba America Nuclear Energy Corp for installation at the South Texas Project units 3&4.

Fairbanks Morse has a signed letter of intent from Areva NP, Inc. for the EDBGs for their first four US-EPR projects to be completed in the United States and has also received a contract from Shaw Areva MOX Services, for the two EDBGs at the Savannah River mixed oxide fuel fabrication facility.

Renewal and new build

The Tognum group is another of the world’s leading suppliers of engines, propulsion systems and distributed energy systems, with a global revenue of EUR2.5 billion (against MAN Diesel and Turbo’s sales of around EUR3.8 billion) in 2009. Tognum’s MTU Onsite Energy brand includes in its remit the provision of EDBGs to nuclear power plants. The first nuclear power plant to be supplied with MTU EBDG backup gensets was a research reactor at the Paul Scherrer Institute in Wurenlingen, Switzerland, in 1962. Today the company claims to EDBGs installed in over 40 nuclear power plants around the world.

In July 2009, Tognum signed a EUR11.25 million contract with E.On to supply two emergency gensets as part of a new emergency power system at Germany’s Unterweser. With emergency power systems in several German nuclear plants getting ready for replacement, Tognum described the strategic significance of the order as ‘enormous’. In May 2010, Tognum won a similar contract worth EUR11 million for the supply of two replacement EBDG gensets for Isar 1. The plant’s original EDBGs were supplied by the company in the 1970s.

Tognum is not concentrating on the replacement generator market. The first-of-a-kind EPR, currently under construction at Olkiluoto in Finland, is being fitted with station black out (SBO) generators driven by MTU’s Series 4000 P63 engines in two of its four independent emergency backup systems.

Over recent years the company has been consolidating its position in Asia, with the establishment in 2007 of a joint venture with China North Industries Group Corporation (Norinco) enabling it to access the Chinese market. The JV set up a factory in Datong, China, to manufacture gensets, and led a consortium, which received a EUR6.5 million order for ten emergency gensets for new nuclear power plants at Fuqing and Fangjiashan in late 2008. This was followed by an EUR85 million order for a further 13 gensets for the Yangjiang power plant. The 23 gensets are scheduled for delivery between 2011 and 2013.

Tognum has also been working to get a toehold in the Russian new build market. Late in 2009, it announced that it had won a EUR26 million order to supply gensets to supply emergency power at the Novovoronezh II nuclear power station. Tognum’s Christof von Branconi described the order as a ‘breakthrough’ in the market for emergency power in Russian nuclear power plants, as previously only locally manufactured gensets had been used in Russian nuclear power plants.

Russia’s own engineering sector is not neglecting the opportunities to supply EDBGs to new nuclear projects. Kolomensky Zavod, part of the Transmashholding group has had its D49 diesel engines approved by Russian standards organisation Rosstandart and nuclear regulator Rostechnadzor for use in nuclear power stations. The company manufactured the four 6.2MW EBDG sets for Iran’s Bushehr nuclear power plant.

FilesTable 1: recent EBDG orders

Isar Isar

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