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New IAEA NEXSHARE Network Promotes Cooperation on Code Validation for SMR Design and Licensing


Representatives from experimental facilities, developers of small modular reactors (SMRs), technical support organizations and international organizations established the Network for Experiment and Code Validation Sharing (NEXSHARE) in a first-of-a-kind interregional workshop held at the IAEA in Vienna last month. (Photo: OECD-NEA)

As part of the IAEA’s Nuclear Harmonization and Standardization Initiative, the Agency is facilitating global collaboration on computer codes to check the safety and performance of advanced nuclear reactors.

In a first-of-a-kind interregional workshop held at the IAEA in Vienna last month, representatives from experimental facilities, developers of small modular reactors (SMRs), technical support organizations and international organizations established the Network for Experiment and Code Validation Sharing (NEXSHARE).

The network is the latest product of the IAEA’s Nuclear Harmonization and Standardization Initiative (NHSI), which was set up in 2022 to facilitate the deployment of safe and secure SMRs and other advanced reactors by harmonizing regulatory activities and standardizing industrial approaches.  NEXSHARE will connect users with all relevant information, including the database of SMR experimental facilities while promoting more efficient use of resources for experiments and a more harmonized approach in code validation.

“Modelling software and experimental data are essential for the rigorous testing and validation procedures needed to finalize design and licensing steps for advanced reactors including SMRs,” said Aline des Cloizeaux, Director of the IAEA’s Division of Nuclear Power. “Collaboration and knowledge sharing in this area has the potential to further reduce both the costs and time required to deploy SMRs, and NEXSHARE is well designed to facilitate this cooperation.”

The design and licensing of new reactors relies heavily on computer codes used to define the boundaries of safe operation and confirm systems will work as intended. These codes must be verified and validated to work with new components, systems and behaviours not previously modelled. Some SMR concepts have design features that require modelling capabilities outside existing datasets or include physical phenomena for which the existing experimental data is inadequate. These are time-consuming tasks which constitute a challenge to the quick rollout of SMRs, which have the potential to play a key role in the clean energy transition.

“The NEXSHARE network is crucial for achieving global cooperation in code validation efforts to help facilitate the deployment of SMRs and other advanced reactors in the near future. Sharing resources and collaborating to demonstrate components and performance at the required operating conditions is essential to address the needs of licensing, design and operation,” said Piyush Sabharwall,  Distinguished Senior Scientist and Department Manager for Irradiation Experiment Thermal Hydraulics Analysis at the US Department of Energy’s Idaho National Laboratory. “Additionally, demonstrating coupled dynamic behaviour and overall system performance provides necessary data for code validation and identifies needs for further development that will be well accepted by industry and regulators to inform critical decisions on components and the system as a whole.”

The workshop, entitled ‘Experimental Testing and Validation for Design and Safety Analysis Computer Codes for SMRs’, was jointly organized with the Organization for Economic Cooperation and Development’s Nuclear Energy Agency (OECD-NEA) from June 18-21 and attended by 77 participants from 29 countries and 3 international organizations. It featured presentations on topics such as experimental testing and code validation programmes, including similarities, gaps and potential for collaborations, as well as common approaches and best practices in testing and code validation. The event included group sessions on recommendations for future work on various reactor types. The information compiled will be used to scope upcoming publications and collaborative activities within the framework of NEXSHARE.

“We need new data and methodologies to ensure the safety of new reactor designs and long-term operation of the current fleet,” said Martina Adorni, a Nuclear Safety Specialist at OECD-NEA. She noted that the NEA’s CSNI Code Validation Matrix “needs to be updated for existing reactors and related technologies and extended to emerging challenges of evolutionary and innovative reactor designs and nuclear technologies, including SMRs. And for this the cooperation with the IAEA NEXSHARE initiative is crucial.”

To address the challenges of safety demonstration for advanced reactors including SMRs, the IAEA is developing a dedicated safety guide as a part of the IAEA Safety Standards framework. The outcomes of the workshop will be utilized to further develop the safety guide in the form of specific recommendations on the use of experimental data for computer codes to assist in SMR safety assessments. The IAEA also offers Technical Safety Reviews for SMRs (including those in the conceptual design stage), which can also address aspects related to the experimental support to the safety analysis computer codes.

“Further development of the computer codes is aimed to support the claims on safety advantages of SMRs. These claims must be backed by robust safety demonstrations, which are a crucial prerequisite for the deployment of SMRs,” said Anna Bradford, Director of the IAEA’s Division of Nuclear Installation Safety.

NHSI’s Industry and Regulatory Tracks have both made advances since the initiative’s inception in 2022. Key achievements on the industry side include the development of a generic high-level user requirement document specific to SMRs as well as the inclusion of additional perspectives on how nuclear infrastructure can be accelerated to facilitate deployment of SMRs and the creation of the Management, Supply Chain and Quality (MSCQ) network. The Industry Track has also produced working papers on topics including serial reactor component manufacturing and the role of non-nuclear codes in standardizing SMR deployments.  On the regulatory side, NHSI has developed a framework for sharing information among regulatory bodies during reviews of advanced reactors and a process for collaborative reviews that allows regulators to work together in parallel, among other accomplishments.

The next NHSI plenary meeting is scheduled for 21 October in Vienna during the International Conference on Small Modular Reactors and their Applications

Professionals with relevant expertise may register for the network here and questions may be addressed to NEXSHARE.

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