Safety features of SMRs

The safety aspects of SMRs have been intensively discussed in several recent publications, mostly originating from the International Atomic Energy Agency (IAEA), which are summarised below. However, one should keep in mind that the safety features of SMRs will be re-analysed following the Fukushima Dai-ichi accident in order to take into account the lessons learnt from it.

The major findings regarding SMR safety are the following:

• The designers of advanced SMRs aim to implement safety design options with maximum use of inherent and passive safety features (also referred to as “by design” safety features).

• On their own, the “by design” safety features used in SMRs are in most cases not size — dependent and could be applied in the reactors of larger capacity. However, SMRs offer broader possibilities to incorporate such features with higher efficacy.

• In the case of some technologies (such as high-temperature gas reactors), the incorporation of passive safety features limits the reactor capacity.

• All of the SMR designs considered here aim to meet international safety norms, such as those formulated in the IAEA Safety Standard NS-R-1 Safety of the Nuclear Power Plants: Design Requirements, regarding implementation of the defence-in-depth strategy and provision of redundant and diverse, active and passive safety systems.

• The available information on safety features of advanced SMRs for plant protection against the impacts of natural and human-induced external events is generally sparser compared to that on internal events.

• The core damage frequencies (CDFs) indicated by the designers of advanced SMRs are comparable to, or even lower than the ones indicated for the state-of-the-art, large water — cooled reactors.