SSM perspective
Background
Small Modular Reactors (SMRs) are typically presented as a solution for safe and reliable energy, requiring less time to construct than the traditional large reactors. The inherent safety features, higher levels of automation and increased reliance on passive safety are often held as reasons for fewer operators being needed in the daily operations and for handling emergencies. However, there are not yet any reliable data (operational experience) to support this assumption.
This report is the first of two, establishing a background for developing a HRA (Human Reliability Analysis) taxonomy, consisting of a literature review and interviews
with subject matter experts. This is done to collect information on potential operator roles, responsibilities and tasks in SMRs, as well as on factors that may affect operator performance, that will inform the further development of the taxonomy.
Drawing on experiences from workshops based on the background provided here, a second (final) report will present a taxonomy for HRA of SMRs and give suggestions for further developments.
Results
The results indicate that the level of automation will have a great impact on what role and tasks the human will have in SMRs.
From the literature review and the interviews, it is clear that there is not much publicly available experience from operating SMRs. It is also a challenge that there is a lack of official information regarding how future SMRs are intended to be operated.
In preparation for gathering experience from operating SMRs it could be useful to develop a common understanding of the challenges for vendors, licensees and regulators.
Relevance
Much of what is known about human reliability in the NPP domain is derived from manual operations in a central control room, dedicated to one reactor. It is important to identify what tasks SMR operators are likely to perform and how their performance might be affected by plant design and operating paradigms. Common tools, like a HRA taxonomy, could be useful for different stakeholders in comparing designs and assessments of them.
The report concludes that HRA for SMRs will need to account for latent errors to a higher degree than is needed traditionally. As the human role shifts from actively operating the plant to monitoring and maintaining the plant (making sure that the conditions for the automated functions and passive safety features are upheld), other human errors might need more attention. Without the human in active control, perhaps fewer human errors are made at the sharp end – consequently, the human
operator could have less opportunity to compensate for latent errors. Also, the field work and maintenance that still needs to be done could have a larger impact on safety
than today due to SMR reliance on automation and passive safety features. The tasks performed by field workers and maintenance personnel need further attention.
The shortage of operating experience from SMRs and empirical data on human interaction with highly automated systems makes it challenging for licensees and regulators to assess if an SMR design, including business model and operating regime, is sufficiently safe.
Need for further research
Given the findings in the report there is a need for deeper understanding of the human role in SMRs and other highly automated designs, including remote and multi-module operation. Until we have more operating experience, further work on an HRA taxonomy can help in understanding the potential human tasks in SMRs, what their impact could be and what scenarios could be relevant for licensees and regulators to use in assessing a proposal.