Zwentendorf NPP

A nuclear power plant (NPP) was built from 1972 to 1977 in Zwentendorf, Lower Austria, in the 1970s. On 5th of November 1978, a referendum against the NPP succeeded. After that, the technically finished reactor never supplied electricity to the grid. Today it is a training site for nuclear employees from foreign countries and open for civil visitors.

Zwentendorf NPP was the first of 3 nuclear power plants supposed to be built in the 1970s in Austria. The other proposed sites were St. Pantaleon-Erla/St. Valentin at the Lower Austrian/Upper Austrian border and St. Andrä in Kärnten. The initial cost of the plant was around 14 billion Austrian schillings (some 1 billion Euros).

There are two types of referendum in Austria - the not binding type called "Volksbefragung" in German, and the binding one called "Volksabstimmung". The 1978 referendum was of the binding type, and soon a law ("Atomsperrgesetz") was introduced to put the results into effect. 64,1% of Austrian voters had participated in the referendum, of whom a slight majority (50,47%) voted against bringing the NPP into service. The referendum was the maybe biggest political success of Chancellor Kreisky who had pushed it personally and experienced his biggest election results afterwards (1979).

In consequence of the referendum the nuclear power plant was brought into conservation. The conservation ended in 1986 and Zwentendorf NPP was used as a depot for other Boiling Water Reactors (BWR), for instance the German reactors Isar 1, Brunsbüttel and Philippsburg 1. It is since 2003 also in use for educational issues of foreign nuclear industry like the German Kraftwerksschule e.V. in Essen. The NPP was step by step transformed into a school reactor providing exercises and trainings for reactor personnel in a realistic environment, which usually would not be possible due to the radiation. In 1989 a study for transforming the NPP into a gas-fired power station was finished - but this project was never put into practice.

A gendarmerie school was located in the administrative building from 1995 to 2001. Electricity supplier EVN AG company bought the buildings and land of Zwentendorf NPP in 2005 setting up a security training center there. They placed a 1.2 million Euro photovoltaic facility on site in 2009. Eventually, annually 180,000 kWh will be generated from solar energy. Solar panels of different types are in operation being long-term tested and improved in cooperation with the Vienna Technical University.

Since 1999 several environmental music festivals took place on the closed NPP site - for instance the "Nuke" festival in the years 1999-2002. Several film shootings too place at the reactor for movies and documentaries after the decommissioning.

As a replacement the coal-fired Dürnrohr Power Station was built nearby using the grid access constructed for the nuclear power plant.

Design of the plant
The chimney is 109,80 m high and was made with sliding formwork. For the physical protection of the reactor building a	predetermined breaking point was applied in 50 m height to prevent damages of the building in case of earthquakes. The reactor building itself has a height of 64 m. It is covered by 1,2 m of ferro-concrete. The base plate has a size of 3 m. The pressure vessel's wall thickness is 132 mm.

The globe in the reactor scheme is called containment building. It has a height of 36 m and a diameter of 26 m. The pieces of the containment have been welded together right in place. During the operation of the reactor they couldn't be accessed and would be filled with nitrogen for protection against hydrogen explosions. The containment of Zwentendorf NPP includes the reactor pressure vessel and the condensation chamber (blue area in the scheme), which is necessary to deal with in Boiling Water Reactors possible sudden increases of pressure in case of leakages. The escaping steam would flow to the condensation chamber and condensate when conveyed through water basins. The containment building can be accessed through locks and includes many penetrations for tubes and cables, which are possible sites of fracture.

The reactor pressure vessel cap has a weight of 60 t and a diameter of six meters. At the non-operational Zwentendorf NPP it is exhibited in the reactor hall next to the platform for loading the fuel assemblies.

In 1972 the construction of Zwentendorf NPP started, after the 1971 decision of the general assembly of the GKT Gemeinschaftskraftwerk Tullnerfeld company. The construction was finished in 1976, then the required tests were started. 200 personnel had been employed already.