Advanced manufacturing techniques have the potential to bring great efficiency gains to the nuclear industry. They enable more complex designs, can improve the quality and safety of components, and reduce the time and cost involved in the manufacturing of components. The approaches afforded by advanced manufacturing can also strengthen supply chains against obsolescence and reduce the need for large inventories in storage. The factory-based deployment model proposed for small modular reactors (SMR) is also dependent on the introduction of several key advanced manufacturing techniques. Recently, the World Nuclear Association’s (WNA) Cooperation in Reactor Design and Licensing (CORDEL) working group produced a report based upon member feedback identifying the most promising techniques in this domain.
While some components produced using advanced manufacturing have been placed into service, these are small items that do not have safety functions and are therefore subject to far less stringent regulations. Further development of regulations and codes and standards to support the introduction of Class One components produced via advanced manufacturing into the nuclear sector is needed.
National regulators have shown interest in the topic of advanced manufacturing and are aiming to set requirements and guidelines to review the emerging applications of the technologies to the nuclear industry. The codes and standards are used by nuclear safety authorities as a technical basis for their regulation, but they currently present gaps with regards to advanced manufacturing techniques. Some techniques are covered within codes and standards, such as electron beam welding in ASME’s Boiler & Pressure Vessel Code (BPVC). However, many gaps exist for other techniques. Examples include a lack of specifications for raw materials, and the absence of adequate qualification methodologies for personnel.
Qualification of additive manufacturing techniques, principally laser powder bed fusion, is a notable gap as it is the most widely and commonly used technique across several industries. As such, the Nuclear Components Based on Additive Manufacturing (NUCOBAM) was launched by SNETP (Sustainable Nuclear Energy Technology Platform) in 2020 to develop a qualification methodology. At the end of the project, NUCOBAM plans to submit the completed and final version of the qualification methodology to nuclear code and standards committees and working groups with the aim of incorporating the qualification methodology into nuclear codes and standards. Approaching the challenge with this goal and aligning the qualification with requirements from existing Design and Construction Rules for Mechanical Components of PWR Nuclear Islands (RCC-M) and ASME BPVC Section III codes should ensure that approaches to qualification for advanced manufacturing are harmonised across the two codes from the start.
However, to be truly impactful, industry initiatives such as NUCOBAM must be welcomed by standard-developing organisations (SDOs) too. Approaches such as that proposed by French Association for Design, Construction and In-Service Inspection Rules for Nuclear Steam Supply System Components (AFCEN), the RCC-M code developer – which has allowed the specific use of a manufacturing process not currently referenced in the code as long as it is supported by specific documentation – will be essential. The feedback and experience then gathered from the use of the techniques will enable the introduction of technical specifications into the code for the advanced manufacturing processes. This pathway to codification will enable the processes to be introduced more quickly and let the nuclear industry benefit sooner from advanced manufacturing.
The challenges of exporting reactor designs to new markets while minimising design changes due to differences in national regulatory requirements are well known and features in the WNA CORDEL “Different Interpretations of Regulatory Requirements” report. These challenges are magnified when it comes to SMRs, however, as one of their main value propositions is factory-based manufacturing. Such an approach will only be possible if the standards to which they are manufactured are aligned.
The combination of growing interest in SMRs and gaps in codes and standards for advanced manufacturing therefore present a rare opportunity for the nuclear industry to harmonise before the technologies are commercialised.
Organisations engaged in reactor design and reactor materials research should therefore dedicate more resources to the development of codes and standards as it is their staff that contribute to code development committees. Such organisations should also look to contribute to collaborative international projects that develop harmonised submissions to SDOs. Finally, SDOs should adopt a similar approach to AFCEN to enable their codes to use unreferenced advanced manufacturing processes supported by specified documentation.
Author informaton: Ronan Tanguy, World Nuclear Association CORDEL Programme Lead
