Digital: accelerating the pathway

Abstract

The Spherical Tokamak for Energy Production (STEP) programme is an ambitious but challenging endeavour to design and deliver a prototype fusion power plant. It is a rapid, fast-moving programme, designing a first of a kind device in a Volatile, Uncertain, Complex and Ambiguous (VUCA) environment, and digital tools play a pivotal role in managing and navigating this space. Digital helps manage the complexity and sheer volume of information. Advanced modelling and simulation techniques provide a platform for designers to explore various scenarios and iteratively refine designs, providing insights into the intricate interplay of requirements, constraints and design factors across physics, technology and engineering domains and aiding informed decision-making amidst uncertainties. It also provides a means of building confidence in the new scientific, technological and engineering solutions, given that a full-scale-integrated precursor test is not feasible, almost by definition. The digital strategy for STEP is built around a vision of a digital twin of the whole plant. This will evolve from the current digital shadow formed by system architecting codes and complex workflows and will be underpinned by developing capabilities in plasma, materials and engineering simulation, data management, advanced control, industrial cybersecurity, regulation, digital technologies and related digital disciplines. These capabilities will help address the key challenges of managing the complexity and quantity of information, improving the reliability and robustness of the current digital shadow and developing an understanding of its validity and performance.This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.

Keywords: design; digital twin; extrapolation; modelling; multi-scale; step.

Figure 1.

Schematic diagram of the evolving interface between the real-world (blue) and virtual environment (orange) (Reproduced from [1]). Note BIM stands for Building Information Modelling.

Figure 2.

Building towards a digital twin.

Figure 3.

The STEP workflow for plasma flat-top design. (Reproduced from [11]).

Figure 4.

The in-vessel system workflow for analysing design concepts.

Figure 5.

How systems simulation and explicit full-physics simulation complement each other throughout the design process in a programme such as STEP, where concept design occurs alongside physics discovery.

Figure 6.

In silico validation of a model of the pressure drop for a liquid metal flowing through a rectangular, conducting channel in an inclined magnetic field (angles between 0° and 90°). Results from CFD simulations (dashed line and filled circles) are compared with the predictions of the model (solid line) for three different aspect ratios of the channels and three different magnetic field strengths. The model reduces to the non-inclined case at both 0° and 90°, where it is validated against experimental data.

Figure 7.

Developments in digital technologies between JET and STEP. The increase in (measured) compute power of the fastest machine or facility at the time in floating point operations per second (FLOPS) is shown as a dark grey line, and the increase in AI training compute in neural net operations per second × days (FLOPS—days) is shown as the light grey line. The timescales for the design (dark band) and operation (light band) of JET and STEP are both illustrated. Compute power data primarily from the Top500 [56], AI compute data from OpenAI [57]. Plasma simulation capabilities at different scales following [58].