This paper presents the CEN WS064 Prospective Group 2, a project involving different European stakeholders from more than 20 organizations with the objective to identify the needs and propose code developments research for the nuclear design and construction code RCC-MRx for innovative reactors with more onerous operational conditions: i) reactor components are generally exposed to higher temperatures; ii) have innovative and more corrosive coolants such as liquid lead or molten salt; iii) materials and components are generally exposed to higher radiation levels than light-water reactors. The main outputs of the CEN WS064 are code evolution proposals and proposals for pre-normative research in support of code evolution. The code evolution is driven by further improving safety and cost reduction. Nuclear Design Codes are robust engineering tools but should incorporate new technologies and research. The paper describes the adopted methodology and the rationale for identifying code evolution needs. Code evolution and research proposals will be discussed. Examples of proposals that will be discussed include: Guideline for design of material/components with innovative coolants, extension of design life to 60 years; qualification of new materials and components with advanced manufacturing. A general requirement is that code evolution and associated material and component qualification and codification need to be significantly accelerated for which new approaches such as AI tools will play an important role.

There is an increased interest in miniature testing to determine material properties. The small punch test is one miniaturized test method that has received much interest and is now being applied to support the design and life assessment of components. This paper presents the results of a test program for a small punch creep test at 650°C of 316L stainless steel produced from additive manufacturing. A major finding is that the deflection rate curve versus time may have multiple minima as opposed to forged 316L with only one minimum. This is believed to be due to microcracking and has direct consequences on the determination of the creep properties that that are based on a single minimum value in the CEN Small Punch Standard. In the paper, aged and nonaged materials are compared, and small punch creep results are also compared with standard uniaxial creep tests. The multiple minima feature means that the approach to determine equivalent stress and strain rate from the minimum deflection rate needs to be modified. Some approaches for this are discussed in the paper. Under the assumption that the multiple minima represent cracking, it opens up opportunities to quantify reduced creep ductility by the small punch test.