It has previously been highlighted (see FESI Bulletin, Autumn/Winter 2019) that various key “themes” have been identified as part of a more structured approach going forward on the way we go about organising FESI-related events for the increased benefit of our members and for the structural integrity community in general.
During a FESI Council meeting held on February 27, 2020 at the University of Leicester, the “champions” of four of the themes presented initial information they had each compiled on providing an introduction of their theme and potential planned events to be held over the next year or so aimed at progressing the theme. We will publish their conclusions as each theme progresses over the coming months.
Below, Mike Martin of Rolls-Royce outlines the FESI Theme of “Probabilistic Methods”.
BACKGROUND
Introduction
As described in the Nuclear Structural Probabilistics Working Principles document available on the FESI website, the nuclear industry has typically not used probabilistic methods in structural integrity assessment as they are perceived to be less safe than deterministic design-code methods, although there are some notable precedents such as application to AGR graphite. Improved knowledge in the structural integrity field continues to highlight that the unquantified margins associated with current design-codes do not provide a consistent measure of component risk. Consequently, optimal designs and the focus of resources are constrained. Whilst safety remains the number one priority, availability and affordability are increasingly significant. The benefit of probabilistic methods, in conjunction with target reliability acceptance criteria, is considered to be a more consistent approach for quantifying component margin. Subsequently, valuable opportunities exist to focus resources where they are most effective, allowing an informed balance of margin throughout the life cycle, including design, manufacture, Non-Destructive Examination, operation and decommissioning.
Routine application of probabilistic structural integrity approaches not only requires the development of codes and standards and acceptance by regulatory authorities but also a change in culture within the organisations responsible for design and structural integrity assessment. There is some tendency for individual technical disciplines to protect their margin resulting in the accumulation of pessimism when data is passed between different disciplines. Improved interaction and integrated approaches between traditionally in-silo technical disciplines is needed to alleviate this. To enable cultural change, there is a general requirement to improve awareness of the benefits and limitations of probabilistic structural integrity approaches within the operator, manufacturer and regulator base. Routine adoption and acceptance of probabilistic structural integrity approaches requires the development of capability and understanding throughout the analyst, operator and regulatory communities.
Probabilistic structural analysis is well-established in other high-integrity industries, often referred to as structural reliability analysis. Although the primary focus of this FESI theme is nuclear, there are clear opportunities to learn from and collaborate with other industry sectors. This theme is well-aligned with current BEIS initiatives including EASICS (Establishing AMR Structural Integrity Codes and Standards), research programmes at TWI, the activities supporting the R5 and R6 panels and related initiatives in the ASME community.
Objectives
The Nuclear Structural Integrity Probabilistics Working Principles document recommends that the various nuclear structural integrity industry forums and conferences continue to be used to build awareness, noting that events that bring together the full range of stakeholders including operators, manufacturers, regulators and analysts are welcomed. FESI has a clear role and opportunity to assist here—the key FESI objective is to help facilitate such events.
SEMINARS/WORKSHOPS
(1) TAGSI–FESI Symposium, April 30, 2020. Confirmed agenda item relating to this FESI theme.
(2) IMechE STMG event late 2020. Not yet confirmed.
(3) ASME PVP2021: dedicated session related to this FESI theme possible. Not yet discussed with ASME.
(4) ISPMNA4 (Fourth International Seminar on Probabilistic Methods for Nuclear Applications). Plan to host in Derby UK in October 2021. Opportunity for FESI to be involved.
MIKE MARTIN
Engineering Associate Fellow–Structural Integrity
Rolls-Royce