Reviewing modernisation work

All Swedish nuclear power plants have undergone modernisation since being commissioned. Further and extensive modernisation work to improve the level of safety is now in progress. Modernisation work is often run in the form of large-scale projects taking many years. Our role is to review these efforts and conduct follow-ups to ensure that the modifications are undertaken in a way that is sound in terms of nuclear safety and radiation protection.

There are several reasons as to why the nuclear power plants are undergoing modernisation. The Swedish Radiation Safety Authority has imposed more stringent requirements on safety. As a result, Swedish nuclear power plants must implement technical, organisational and administrative improvements raising the level of safety and their resilience against various kinds of transients and accident conditions. The power uprates carried out or planned by the nuclear power plants mean that the facilities need to carry out modernisation work for operation at the higher power level.

Modernisation work is particularly important now as the reactors are planned to be operational over a more extended period of time than they were originally designed and analysed for. For example, equipment is becoming obsolete and it is difficult to find spare parts or difficult to maintain expertise in old areas of technology.

Authority imposing more stringent requirements

On 1 January 2005, new regulations entered into force pertaining to the design and construction of nuclear power reactors–SSMFS 2008:17 (formerly SKIFS 2004:2). The aim of these regulations is to raise the level of safety and update the requirements imposed. The Authority imposed more stringent requirements for safety through the new regulations. Since then, Swedish nuclear power plants have needed to take wide-ranging measures to fulfil the requirements and have for each reactor drawn up a transitional plan specifying the kinds of measures to be taken and the schedule.

Multi-year process

Safety modernisation programmes take several years to complete. We review this work in stages. The same rules, regulations and procedures apply to extensive modernisation of nuclear power plants as to their plans to raise their power output (power uprate). We must approve each stage on the part of a nuclear power plant before it may move on to the next stage of the process. Our review process consists of the following stages:

  • Before the nuclear power plant may begin modernisation work, we review a preliminary safety analysis report (PSAR).
  • Before the nuclear power plant may begin the reactor’s test operation following completion of modernisation work, we review an updated safety analysis report.
  • Before the nuclear power plant may begin the reactor’s routine operation (usually after at least one year of test operation), we review a supplemented safety analysis report.

All aspects are examined

Our initial reviews focus on assessing whether the assumptions and preconditions are sufficient for a successful modernisation project. In particular, we examine modifications and principal changes having a major impact on safety. Here, examples include the transition from analogue to digital technology and the implementation of more up-to-date control equipment.

Our reviews encompass several areas, for example to check whether:

  • the technical solution meets requirements
  • the quality standard of the modification is assured
  • the requirements imposed for safety are met while the modification work is in progress
  • the work procedures of personnel have been adapted to the modernisation work
  • the personnel working in the control room have been trained in a simulator
  • other personnel have received sufficient education and training