Utilization of IEC 61508 in the nuclear domain

Licensing and qualifying nuclear domain instrumentation and control systems and equipment has traditionally been extremely expensive and time-consuming. In Finland, this has been partly due to regulatory requirements demanding compliance against nuclear specific standards such as (IEC 61513, IEC 62138, IEC 60880, and IEC 60987). Demonstrating compliance with the standards is difficult, and there has been declining interest from suppliers to take part in nuclear projects.

The Finnish nuclear sector, however, has taken steps towards simplifying the qualification process. The Finnish regulator STUK has recently updated its requirements allowing standards used in other fields of industry also to be utilized in qualification. The KELPO project is a joint venture launched by Finnish nuclear utilities and STUK that focuses on new ways to streamline the qualification process, and to ensure the use of standardized, serially produced equipment and components to be used in lower safety classes. KELPO also aims to develop a shared digital platform to be utilized by power companies, harmonize qualification procedures, and reduce redundant qualification efforts.

Due to these advancements, the utilization of generic IEC 61508 compliant equipment is now possible in lower safety classes in, e.g., modernization projects in Finnish nuclear power plants. It is even possible to define the entire instrumentation and control system development life cycle according to the generic IEC 61508 standard.

Nuclear sector experts may not be fully accustomed to using IEC 61508. The IEC 61508 standard has a few differences when compared to nuclear specific standards that should be paid attention to. At least the following should be considered:

• Safety integrity levels: Nuclear specific standards do not recognize safety integrity levels, even though a graded approach is also used in nuclear domain.
• Techniques and measures: IEC 61508 lists techniques that should be used in different safety life cycle phases. Nuclear specific standards do not explicitly mention the techniques that should be used.
• Organization: IEC 61508 requires that safety management responsibilities are specified, typically by appointing a safety manager.
• Functional safety assessment: Even though reviews, audits, and assessments are familiar to the nuclear sector, an all-encompassing functional safety assessment performed independently from system design is not required by nuclear specific standards.

Huld has experience on the application of IEC 61508 in several domains including nuclear, and can assist in functional safety management, and independent safety assessments. Read more about Huld’s safety offering.

Text: Jussi Lahtinen