Chinese finally sign up for the VVER-91

At a time when orders for new nuclear plants are very thin on the ground, the Russian nuclear industry ended 1997 in triumph with the final signing in Beijing of a multibillion dollar contract for the supply of two 1000 MWe PWRs to China (see NEI, February 1998, p2). The signatories of the contract were AO Atomenergoexport (AEE) and VPO Zarubezhatomenergostroy (ZAES) of Russia and Lianyungang Nuclear Power Corporation of China. An earlier contract covering design of the plant had been signed in June 1997.

The reactors in question are VVER-91s and will be built in Jiangsu province at Lianyungang , which is about 250 km north of Shanghai. The project is unusual in that it has survived a change of site. The plant was originally planned for a site in Liaoning province, but financing proved a problem for that region and the site was changed in 1996.

The VVER-91 concept (described in NEI, March 1991, pp 19-22) is the fruit of the long-standing collaboration between the Atomenergoproekt research and design institute in Saint Petersburg, Russia, and Imatran Voima Oy (IVO), Finland. An agreement between the two organisations specifically on developing the VVER-91 was signed at the beginning of 1990, but early work on the concept goes back as far as

1977 (the year which saw the commissioning of unit 1 of Loviisa, IVO’s highly successful VVER-440 station). In succeeding years the design, which builds on experience with VVER-1000s (the first of which entered service in 1980), has been modernised in compliance with evolving codes and standards.

The lead designer of the VVER-91 is St Petersburg Atomenergoproekt, the lead designer of the reactor and primary circuit is OKB Gidropress, while IVO Power Engineering acts as a consultant contracted by Atomenergoexport.

SAFETY AND ECONOMY

The VVER-91 is an evolutionary advanced version of the VVER-1000, and with the Russian nuclear industry still having the matter of Chernobyl inescapably in its curriculum vitae, safety engineering has of course been paramount.

VVER-91 safety features include:

• Reactor building with double containment.

• Safety systems with four completely independent trains.

• Functional and physical separation of safety system trains.

• Provisions to manage primary-to-secondary leaks.

• Leak-before-break approach, avoiding abrupt pipe break.

• Integration of severe accident management into the plant design (including measures to prevent severe accidents and mitigate consequences).

The design is based on the safety criteria included in the Russian and Finnish regulations and guidelines. Where there are differences, the stricter requirement is adopted. The design also takes on board International Atomic Energy Agency recommendations.

The safety train characteristics (eg capacities and rates of response) are selected to ensure nuclear and radiation safety under any initiating events envisaged in the design and particular emphasis is placed on achieving a very high level of physical separation between trains. In addition the safety system trains have fire-resistant physical barriers along their whole length, isolating them from each other.

Special attention has also been paid to economics. A relatively small construction volume has been achieved, reducing capital cost and construction time.

The whole project will take about eight years to complete.

FINNISH CONTRACT

In February IVO Power Engineering and the Russian organisations AEE and ZAES signed a contract in Moscow covering IVO PE’s participation in the Lianyungang twin-VVER-91 project. The contract includes checking the layout plans of certain buildings, including the reactor building, revisions to earlier plans, and preparation of detailed structural drawings of the buildings up to ground level. All this will be done during 1998.

IVO PE describes the new contract as a continuation of design work it did on the VVER-91 during the period 1990-96. The value of the contract is initially about FIM 14 million (the structural design component accounting for FIM 10 million), but IVO PE is currently in negotiations on expanding its scope.

The VVER-91 is also a contender in the Indian nuclear power market, and discussions between Russia and India continue. In the longer term it may even be a candidate in the Finnish domestic market should plans for a fifth unit be resuscitated.