Structural integrity

High temperature assessment methodology development and application

Situation

High temperature design and assessment standards typically have a limited set of supporting material information and are validated for common operating environments only. The designers of new, novel power plants are responsible for producing sufficient evidence that their choice of material, fabrication methods and operating environment can be safely assessed using the available standardised methods.

Approach

Frazer-Nash Consultancy has a multidisciplinary engineering team across UK industry, developing and applying assessment methods for materials operating in the creep regime. The company is a key member of the EDF R5 Development Panel, contributing updates, amendments and new methods to the UK’s national code for the assessment of high temperature nuclear plant.

Frazer-Nash supports several gas-turbine manufacturers in the development and management of material test programmes, material characterisation, assessment methodology development and validation through to application of the methods in the design of new systems and the life extension of existing plant.

AMR generic design assessment (GDA) high temperature structural integrity support

Situation

A reactor design is only viable to operate in the UK market if regulatory requirements, including the generic design assessment (GDA), are met that underpin it as being safe for commercial use. These requirements are the most stringent in the world and require operators to claim their designs are resilient to normal and fault conditions.

The safety cases that underpin these claims have multiple 'legs', one of which is structural integrity. Components with high reliability claims must demonstrate they will not fail with the presence of defects. This is beyond the remit of design codes such as ASME III. Therefore, the UK regulator fully endorses using the R5 high temperature assessment procedure for demonstrating damage tolerance of high temperature plant.

Approach

At first glance, considering structural integrity at this early stage appears premature. However, a substantial amount of supporting data, knowledge and experience are required to perform R5 assessments and this takes many years to acquire. Furthermore, government funded R&D work has not considered specific environments to date, so AMR vendors will need to fill this gap for their designs. Withholding these considerations now leads to a risk of being unable to demonstrate a timely route to design substantiation during GDA, causing a delay to implementation and risking de-valuation of the business.

We can identify the training needs, knowledge, and performance gaps in your structural integrity substantiation route to identify what you need to put in place now in order to ensure you have an adequate route to satisfying the regulator during GDA. By demonstrating this now, you will be able to claim a position to prove a viable reactor design at the time it is needed. We therefore believe this will enhance the value and attractiveness of your business.

Design code assessment methodology for LWR plant

Situation

The desire for longer Light Water Reactor (LWR) plant design lives, and the potential for civil LWR plants to adopt flexible modes of operation, has increased the urgency to adopt more accurate life assessment methods. The traditional design margins and acceptance criteria embodied within international codes and standards may not be fit for purpose when considering modern plant performance requirements and economic constraints.

Approach

Frazer-Nash Consultancy’s Asset Integrity group has a wealth of experience in structural assessment of high integrity components of LWR plants, including design substantiation against nuclear codes and standards and fitness for purpose assessments to support life extension.

Frazer-Nash is a key supporter of code development activities of several SDOs (ASME, AFCEN and JSME) through the UK’s CORDEL Mechanical Codes and Standards Task Force (MCSTF).

Low temperature defect tolerance assessment

Situation

For some systems, structures and components (SSCs) of LWR plant the consequences of gross failure may be significant, with implied structural integrity claims beyond what may be inferred from satisfying the requirements of an established design and construction code (e.g. ASME III, RCC-M, etc.). In these situations, and in absence of engineering redundancy, measures over and above normal practice are required to underpin the structural integrity claim. In this scenario, the plant designer or equipment operator may employ defect tolerance arguments as a supporting leg of a safety case.

Approach

Frazer-Nash has considerable experience in performing defect tolerance assessments to support the design and in-service assessment of civil nuclear plant structures. Frazer-Nash is also a key contributor to EDF Energy’s R6 Development Programme, exercising several streams of research and development work to further validate and improve the UK’s existing procedure for the assessment of structures containing defects.