Temelin’s virtual refit

The Temelin nuclear power plant in the southern Bohemia region of the Czech Republic is yet to produce a single watt of electricity 12 years after construction began. In 1982 CEZ, the then Czechoslovak power generating company, placed a contract for a Soviet technical design including a reactor building, auxiliary buildings and the diesel generator station. In 1985 design company Energoproject Praha (EGP) processed the initial design for two VVER 1000 MWe units and construction began in February 1987.

In November 1989 the Velvet Revolution took place in Czechoslovakia; the Russian military withdrew and the country embraced capitalism. The economics and politics surrounding the Temelin plant had changed entirely. In 1990 the new government decided to complete only two of the four 1000 MWe units originally planned. For two years construction almost completely stopped. OSART carried out a safety audit in 1991-2 with the aim of ensuring Temelin would meet safety standards demanded of Western reactors and the subsequent report highlighted 300 changes that were necessary. CEZ brought in Westinghouse to refit the instrumentation and control and to ensure all safety criteria were achieved.

However, partly as a result of the Russian departure, the design drawings and data were far from complete. Many drawings were inaccurate or did not exist. In order to integrate new safety systems into the original design required detailed and accurate models and design data.

EGP had first had dealings with the Cambridge UK based company CADCentre through Electricité de France in 1989. CADCentre offers a series of computer generated design and visualisation software products which provide an integrated solution to problems throughout the engineering life-cycle from conceptual design through to decommissioning and the software programmes can provide intelligent 2D logical process models, 3D plant space modelling and interactive viewing where it is possible to ‘walk through’ a virtual plant.

The process by which Temelin construction data has been generated is effectively the reverse of a normal engineering construction project. Rather than starting with design drawings and building a plant based on them, EGP had to establish design information by examining the already built plant. Traditionally this problem would have been solved by design engineers using tape measures to construct the drawings. EGP commissioned Skoda Praha to carry out a pilot project; the former state engineering firm chose seven rooms within Temelin where the design drawings were created using the traditional hand measurement technique and one using CADCentre’s photogrammetry solution.

Using CADCentre’s DIGI-AB software, Skoda was able to photograph a room from a variety of different positions using a theodolite to ensure accurate camera positioning was known. The images were then scanned into digital format and the data entered into the DIGI-AB programme. DIGI-AB and another CADCentre product, its Plant Design Management System (PDMS) are designed to interact freely and by doing this both two and three dimensional design models were created. Originally developed to create design data in hazardous conditions where human access is impossible, the photogrammetry system proved faster, more accurate and cheaper than the traditional technique. A third integrated CADCentre product, Review Reality, allows an operator to use PDMS data to create a 3D computer generated animated model, a virtual plant through which he or she can move in real time.

Skoda carried out the photogrammetry work. An early challenge for the company was to accurately map the geometry of a series of pipes to connect them to the steam generators through feed pipes. An added complication was that the pipes were connected to temporary piping which provided fluid through the system, preventing corrosion from taking place. Skoda had to measure the pipe positions to within a 4 mm accuracy and within a time frame of 14 days so that the pipes did not become rusty.

By using the CADCentre system Skoda managed to create a 3D PDMS model of pressure vessels, feed piping, steel platforms and fittings within a 2 mm accuracy. The engineers were then able to simulate the final assembling process and calculate the most efficient method for carrying out the work.

“Implementation of DIGI-AB technology proved to be an enormous success,” said Eduard Vambera, leader of the photogrammetry team. “It is a very innovative and creative tool for us and we can now do projects which would otherwise be unimaginable.”

Improving Safety

Following the success of this pilot project, Skoda began a more comprehensive project to create PDMS design data for all the important areas of the Temelin plant, including the reactor building which will, of course, not be accessible once the plant goes critical. The main reason for the work was to provide Westinghouse with design data so that it could introduce the changes necessary to establish Western safety criteria in a manner which was feasible and affordable.

Following the Russian withdrawal, the plant found itself with almost no electrical documentation. One of Westinghouse’s key tasks was to re-cable the plant, separating cables for fire, noise and electrical impacts. This task gave Westinghouse some headaches, according to plant manager Mike Kominski.

“The Czech’s had to do a lot of homework before they approached us,” he said. “We had to know what they wanted.” As a result of the Westinghouse upgrade there are now more cables than originally planned and more requirements for control. The positioning of the cables had to be highly specific and working out where they could go required detailed design data.

In order to tell Westinghouse what needed to be done, and how it could be achieved, EGP contracted Skoda to carry out a comprehensive photogrammetry survey of Unit 1 and from that to construct the computer generated models.

Skoda has photographed 100 rooms out of a total of about 300 within the Unit. EGP cannot afford to photograph every room in the building and is concentrating on those that are thought to be most important, including the area within the containment structure. The density of photographic points within a room depends on the complexity of equipment within it. The photographer has to have a full understanding of the photogrammetry process in order to work out how many photographs and from what positions are necessary to provide the information necessary.

The DIGI-AB programme can calculate distances between objects through establishing a common point from a number of different images and through the positioning of a standard metre within the photographic frame. Once the data has been processed the designer can ‘walk through’ the image data base, effectively creating a virtual plant which anyone, anywhere in the world, can explore. By converting the images to a computer generated model it is possible to test various design changes to establish whether they are possible given the plant dimensions and criteria such as health and safety.

The upgrades to Temelin have cost CEZ, between 40-100 billion Kr ($1.14 -2.84 billion) over five years. CEZ is wary of giving accurate figures. The photogrammetry itself has cost around 20 billion Kr ($569 million).

The Temelin project has proved to be a standard bearer for CADCentre’s photogrammetry based solution and it is now being used for a number of other problems in power generation and process plants throughout Eastern Europe.

“Eastern Europe has a host of plants with no documents,” says CADCentre marketing manager for Eastern Europe, Alexis Boseley. “When they come to do maintenance work, where do they start?” The Paks NPP in Hungary has taken up the technology, as has Mohovce in Slovakia.

Integrating Worldwide

A fourth CADCentre product, Hyper Plant, adds further value to the company’s integrated solution. Hyper Plant is an Internet based product which provides users throughout the world with access to the data generated through DIGI-AB, PDMS and Review Reality. An operator can view a room from any desired angle, either using the original photography or the computer images, and by clicking the mouse on any component can access design and performance data. The software also provides searches for certain types of instruments as well as maintenance records. With a complete record of maintenance and modification, the problems the operator faces when decommissioning a plant can be minimised.

The development of Hyper Plant reflects the globalisation of engineering design and construction. Many major companies have opened offices in developing nations such as India and South Korea as well as Eastern Europe, to take advantage of lower labour costs. Accessing data from anywhere in the world is therefore of prime importance.

“CEZ has to be able to demonstrate the safety of the site. By using CADCentre products it can present the database to anyone in the world,” says Boseley.

The Temelin plant posed CEZ with unique problems. Almost no other plant in the world has attempted to integrate a Soviet design with Western safety principles. Despite the huge efforts made by CEZ, EGP, Skoda Praha, Westinghouse and CADCentre to ensure it is as safe as Western reactors, the plant’s future remains uncertain. Whether a political decision is made to start up the plant or not, Temelin is likely to become a monument to the development of photogrammetry techniques. The monument may exist for decades in physical reality, but if electricity is never generated at Temelin, it will still virtually exist on computer screens throughout the world.