Development and observations on the multi-legged structural integrity safety case

Area of Science:

• Nuclear Engineering
• Structural Integrity Assessment
• Safety Case Development

Background:

• The UK's Technical Assessment Guide for Safety Integrity (TAGSI) published principles for nuclear component structural integrity in 2001, introducing a multi-legged approach.
• This approach was developed to support UK 'conceptual defence in depth' safety cases for 'incredibility of failure' components, building on 1990s research.
• Since 2001, multi-legged assessments have been applied to the design, construction, and operation of UK nuclear power plants and proposed new designs.

Purpose of the Study:

• To review the evolution and application of the multi-legged approach for nuclear component structural integrity assessments since its inception in 2001.
• To evaluate the impact of advancements in nuclear design and construction codes on the assessment methodology.
• To propose an updated model for current and future nuclear power plant safety cases.

Main Methods:

• Review of historical development of the multi-legged approach by TAGSI.
• Analysis of improvements in nuclear design and construction codes over time.
• Examination of recent generic design assessments and their safety case structures.

Main Results:

• Nuclear design and construction codes have advanced, strengthening arguments for design and manufacture.
• The reduced likelihood of defects in modern components lessens the reliance on proof testing.
• Recent generic design assessments show a trend towards rearranging the scope and number of legs in safety cases.

Conclusions:

• A generalized three-legged model is considered more appropriate for new nuclear power plant safety cases.
• This updated model remains consistent with the original TAGSI principles and the multi-legged proposal.
• The evolution reflects advancements in component manufacturing and safety assessment methodologies.