Temelin's hard-earned success3 July 2002
Several obstacles had to be overcome during the Temelin upgrade project, including language and cultural differences, but the biggest challenge was the integration of Western I&C technology with Russian plant design. By James F Mermigos
Cooperation between utility CEZ, general contractor Skoda Praha, general designer Energopraha (EGP) and Westinghouse has led to the successful completion of a unique project. As the Temelin nuclear power station continues to prove itself to be a successful integration of Western instrumentation and control (I&C) systems and Russian reactor technology, the benefits of this combination of technologies will be clear.
One of Westinghouse's objectives from the beginning of this contract was to successfully prove the installation of modern, Western microprocessor control systems in Russian-designed nuclear power stations. Now that this has been achieved, the knowledge base developed there can be applied to current Westinghouse contracts in Russia, Ukraine and Bulgaria. The utilities in these countries have now seen the benefits of microprocessor-based control systems as a part of their modernisation plans. The implementation of modern I&C systems at Russian-designed VVERs will bring these reactors in line with safety enhancements recommended by the IAEA and other international agencies.
New I&C at Temelin
In 1993, Westinghouse was awarded multiple contracts for work at the two VVER-1000 units of the Temelin nuclear power station in the Czech Republic. The contracts were in the two main areas of I&C and supply of nuclear fuel. The fuel contract scope consisted of nuclear fuel fabrication of the first core load and four reloads of Western-designed fuel. As a complement to the nuclear fuel supply, Westinghouse also provided technical services to optimise operating efficiency and safety at Temelin. Online monitoring systems, which provide precise knowledge of current core power, flux distribution and core peaking factors, help to optimise operation of the plant. In the I&C area, Westinghouse was selected to replace the entire I&C system, and radiation monitoring and diagnostic systems.
The scope of the Temelin I&C project was all-inclusive. Westinghouse was responsible for providing reactor protection, reactor control, balance of plant control, and information systems for the plant. Westinghouse also was responsible for providing emergency operation procedures (EOPs), accident analyses, and licensing support as part of the I&C contract. The I&C system consists of more than 600 control cabinets covering several hardware platforms and software coding languages.
The Westinghouse-designed protection system is responsible for protecting the nuclear fuel and ensuring that there are no radiological releases to the environment. It consists of two parts: a primary reactor protection system (PRPS) and a secondary or backup system called the diverse protection system (DPS). The PRPS is built around the proven Eagle technology family of hardware, while the DPS is a newly-designed system based on different hardware and software than the PRPS. Both systems run in parallel to protect the reactor. This design concept of diverse protection systems provides another level of fault and failure tolerance.
The reactor control and limitation system (RCLS) controls the nuclear reactor and provides essential monitoring and limitation functions. The limitation system automatically reduces reactor power based on plant conditions to keep the unit online, even at reduced power levels. The WDPF II distributed process control family of hardware and software, and the newer Westnet III for data transfer are the basis for the plant control and unit information system. These systems control, monitor and assist operators using modern man-machine interface guidance and human engineering. The information system is also capable of extremely high data-transfer capability. In addition, the system brings large amounts of plant and process information together while providing it to the operation, maintenance and management staff of the utility in an operator-friendly format. Based on the fiber distributed data interchange (FDDI), the system can handle more than 200,000 data points per second. This extremely high transfer rate enables the updating of data once per second, helping to ensure that the operator receives the most up-to-the-minute plant data.
Westinghouse also was responsible for licensing the I&C that it supplied, a first-of-a-kind effort. The I&C system was designed and built to ensure compliance with US, international and Czech safety, quality and design standards. While many of these standards overlap, special consideration had to occur in order to be successful in this area. With the introduction of US Nuclear Regulatory Commission practices, the licensing process for the upgraded Temelin I&C and fuel designs were enhanced. To plant designers, these standards provided a detailed listing of regulatory criteria and industry standards which plant designs, analyses and programmes must comply with. To the writers of licensing documentation, the standards provided a structured, well-defined plan for the format and content of a safety analyses report. The standards also provided the same guidance for the licensing of large plant upgrades or modifications.
East meets West
The Temelin project's construction phase emphasised the integration of Western I&C technology and Russian plant design. Westinghouse invested time and resources in the beginning of the project to visit other VVER-1000s in the Ukraine and Russia, and to meet with Russian plant designers. These meetings helped expand the foundation of Westinghouse's knowledge of plant operations and expectations of the operators in the VVER plant design. While the VVER-1000 is a Russian plant design, it is still a pressurised water reactor with some of the same design attributes as Western PWRs. Westinghouse also worked closely with the general designer for the Temelin plant to enhance its knowledge of VVER technology and Russian design philosophy.
The testing programme for the I&C and plant culminated with the plant performance test (PPT). During this test the unit runs for 144 hours and must operate without failure or event. However, the extensive testing programme for I&C begins in the factory location and continues once the system is part of the site environment. Integrating the testing programme of the I&C system with the entire plant testing programme tests the I&C with the fluid systems that it is controlling or monitoring.
As a part of the technology transfer agreements between Westinghouse and the utility, Westinghouse sponsored more than a dozen Czech nationals at its Pittsburgh, Pennsylvania headquarters to work with Westinghouse design engineers in an on-the-job training programme. Westinghouse invited engineers in the areas of functional design, hardware design, software design, and verification and validation. These engineers stayed in Pittsburgh for up to one year and interfaced with Westinghouse engineers on a daily basis. This programme enabled CEZ to have local engineers available with the skills necessary to understand and assist with the design process after CEZ controls the Westinghouse-supplied systems.
Temelin and its owners CEZ have begun to enjoy the benefits resulting from the hard work and cooperation of a long and challenging project. Unit 1 has recently completed the 144-hour PPT, which signifies the end of the project's construction and testing phases. After receiving approval from Czech nuclear regulator SUJB, the 18-month period of trial operation commenced on 10 June. Throughout the trial operation, the unit will be connected to the power grid and will produce 1000MWe at 100% for the Czech Republic. Temelin 1 is now officially one of the "productive units" of CEZ.
While not garnering as much attention as initial criticality for unit 1, unit 2 achieved initial criticality at the end of May 2002. The second unit now will begin power ascension testing with plant performance testing conducted in late 2002 or early 2003.
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