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Digital safety instrumentation and control important to safety in nuclear power plants

Safety instrumentation and control (I&C) systems automatically control and limit safety parameter values like

  • pressures,
  • temperatures and
  • neutron flux densities.

If limits are exceeded, safety functions like

  • power limitation,
  • turbine trip or
  • reactor trip

are actuated.

At the time of plant construction hardwired I&C equipment based on analogue relay and transistor technology was installed. Today the maintenance and, if necessary, the replacement of analog equipment requires a significant effort. Thus, in German nuclear power plants it is being replaced with software-based equipment that processes measured values and data digitally. Particularly, non-safety related systems but also equipment of lower safety significance is affected by replacement programs. The part of the reactor protection system that processes safety critical data and actuates corresponding safety functions is, however, still hard-wired and processes measured values and data in a purely analogue way.

The Federal Office for the Safety of Nuclear Waste Management (BfE) supports the Federal Environment Ministry (BMU)

  • in setting up the the requirements for safety related applications of digital I&C equipment in nuclear power plants,
  • in evaluating the industry-developed methods for demonstrating compliance and
  • if necessary, in the preparation of federal positions on licensing issues, especially for I&C functions with high safety significance.

For this purpose, BfE initiates and controls associated research projects. In addition, BfE participates in meetings of national and international working groups and contributes to their discussions and progress. Currently, the focus is on I&C equipment which – outside of the central I&C –

  • gathers and processes measured values in the plant,
  • protects or actuates safety-relevant systems, and
  • secures the energy supply of the safety-relevant systems.

Safety and security requirements for digital I&C

At present, BfE is involved in developing and defining the safety and security requirements for software-based I&C:

  • at national level as

    • nuclear regulatory framework (safety requirements for nuclear power plants),
    • Standards of the German Nuclear Safety Standards Commission (KTA-Kerntechnischer Ausschuss) in the form of the KTA standards of the 350x series,
    • Guidelines of the Association of German Engineers (VDI-Verein Deutscher Ingenieure) and
  • at international level as

    • Safety standards of the International Atomic Energy Agency (IAEA),
    • Guidelines of the European Commission (EC) and
    • Standards of the International Electrotechnical Commission (IEC).

Results of international working groups

The report "Licensing of safety critical software for nuclear reactors - Common positions of international nuclear regulators and authorised technical support organisations. Revision 2018" describes the work of a group of I&C experts from the following regulators and technical support organizations:

  • BEL-V (Belgium),
  • BfE (Germany),
  • CNSC (Canada),
  • CSN (Spain),
  • ISTec (Germany),
  • KAERI (South Korea),
  • KINS (South Korea),
  • NSC (China),
  • ONR (United Kingdom),
  • SSM (Sweden), and
  • STUK (Finland).

The report provides common technical positions on a set of important licensing issues in connection with the design and operation of safety critical software in nuclear power plants. A revision of the common position and recommended practices of the European Commission consensus document published in May 2000: "Common position of nuclear regulators for the licensing of safety critical software for nuclear reactors (EUR 19265)" is part of this report.

State of 2018.07.31

© Federal Office for the Safety of Nuclear Waste Management