Advanced Nuclear Power Sept2001

Advanced Nuclear Power - The Magazine of Framatome ANP

Framatome ANP has upgraded the entire reactor protection system at a Westinghouse-built plant with digital instrumentation and control (I&C) equipment. The successful upgrading of both units of Switzerland's Beznau nuclear power plant once again impressively demonstrated why Framatome ANP is the world leader in modernizing reactor I&C. In the last 10 years, the company has won well over half of all I&C modernization contracts awarded worldwide - an impressive customer vote of confidence - for the digital safety I&C platform, TELEPERM™ XS, that is currently in use or on order at 23 reactors, including PWRs, BWRs and VVERs, in seven countries.

Fit for the Future with TELEPERM XS
By deciding to upgrade the I&C equipment for reactor scram and engineered safety feature actuation, the company that operates Beznau - Nordostschweizerische Kraftwerke AG (NOK) - took an important step toward ensuring that the plant reflects the latest state-of-the-art technology and can operate economically for many years to come. Replacement of these systems became necessary as spare parts procurement and component maintenance were increasingly difficult. Another aim was to improve ease of testing equipment.

In TELEPERM XS, Beznau now has a digital safety I&C platform that is fully qualified for nuclear applications. Other key features include low inspection and maintenance, and optimized diagnostics capabilities.

Scope of the Project
The contract for backfitting Beznau Units 1 and 2 with new safety I&C equipment was awarded by NOK in 1998. The following enhancements were made along with installing the new equipment:

Significantly better fault diagnosis in the safety I&C systems
Stricter physical separation of redundant trains
Functional improvements to closed-loop controls.

The former operating and monitoring concept was retained, meaning that operating personnel were not faced with significant changes.

The new safety I&C equipment is designed with quadruple redundancy and physical separation of all redundant trains, with the individual safety functions of each train being further divided among two so-called Diversity Groups (A and B). Also, each train has two independent TELEPERM XS computers: one for Diversity Group A and another for Group B.

The new closed-loop controls for the reactor are of dual redundancy.

Key Steps of the Project:
From Design to Installation and Startup
In accordance with Swiss regulatory guides, the project was divided for both plant units into four hierarchical levels consisting of a basic design phase, a detailed design phase, an engineering phase, and an installation and startup phase.

During the basic design phase, with NOK's assistance, the scope of I&C equipment requiring replacement was determined and process requirements were analyzed and classified according to their relevance to safety. They then were broken down into individual I&C functions for the various safety objectives.

NOK personnel participated in a complete integral functional test that was performed for both plant units on the fully assembled equipment, using a simulator at a test facility in Erlangen. This enabled the startup tests performed during the refueling outages to be restricted to only those that involved the plant periphery as well as process-related tests.

Integration of the new I&C equipment at Beznau was performed during the refueling outages scheduled for each of the two units.

Enhanced Plant Operation
The operating experience gained at Unit 1 demonstrated that the new TELEPERM XS safety I&C equipment facilitates optimization of plant operation. Improved control parameters, for example, enable systems to be operated in such a way that process components are not subjected to unduly severe stresses. Due to the intrinsic features of the new I&C equipment, more functions now can be performed with less hardware, freeing cabinet space for other tasks.

The heart of the new safety I&C - the TELEPERM XS equipment - is automatically cyclically tested during plant operation. Thus the number of in-service tests routinely required during a plant outage has been reduced to just those needed for checking interfaces with the plant periphery.

Dr. Urs Weidmann, Head of the Electrical Department at Beznau Nuclear Power Station, expressed his satisfaction as follows: "Our experience so far has confirmed that the TELEPERM XS safety I&C system meets all of the technically demanding goals set for the project in full. We are convinced that, by choosing TELEPERM XS, we have opted for a state-of-the-art, trendsetting reactor protection system."