KriSTail

Analysis of critical raw materials using innovative probe technology on tailings

Motivation

Critical raw materials (CRMs) such as rare earths and platinum group elements are indispensable for future technologies such as electric motors, wind turbines and battery systems. However, the European Union is heavily dependent on a few supplier countries for many of these raw materials, which jeopardises the security of supply and resilience of value chains. At the same time, tailings piles and ponds are increasingly recognised as potentially valuable secondary sources of critical raw materials, especially where historical processing methods have left significant residual contents. However, the internal structure of such tailings bodies is highly heterogeneous, meaning that conventional drilling and ex-situ laboratory analyses alone often offer only limited information and low depth resolution, while requiring considerable time and expense and involving difficult working conditions in water-bearing, unstable tailings. There is therefore an urgent need for robust, in-situ methods that can be used to characterise CRMs directly in the tailings body with high vertical resolution, reduced drilling effort and lower environmental and CO₂ impact.

Approach

Within the joint project KriSTail, J&C Bachmann is developing a high‑energy in‑situ X‑ray fluorescence (XRF) probe that can be hydraulically pressed into fine‑grained tailings material without the need to first drill a borehole. The core of this new development is a compact high‑voltage power supply (approx. 70 kV) in combination with a suitable X‑ray tube and a mechanically robust probe geometry, enabling the detection of higher‑atomic‑number elements, including rare earth elements and other critical metals. The probe will be combined with Cone Penetration Testing (CPT) technology, so that continuous geochemical profiles can be acquired directly within the tailings pond without additional drilling.

MRE will provide the scientific support and validation of the probe through comprehensive laboratory analyses (e.g. ICP‑MS, XRD, XRF) on representative tailings samples, as well as systematic comparison with the in‑situ measurement data. In a joint case study at a selected tailings pond, the prototype will ultimately be demonstrated under real operating conditions, the measurement results will be externally validated, and transferred into a geochemical model of CRM distribution with the goal of demonstrating Technology Readiness Level (TRL) 6.

Project obejctives questions

Overall objective:

Development, laboratory validation, and field validation of a high‑energy in‑situ XRF probe that enables reliable identification and quantification of selected critical raw materials in tailings ponds and is demonstrated up to TRL 6.

Specific objectives:

• Technical further development of the probe: Design of a compact high‑voltage power supply (≈ 70 kV) and integration of a suitable X‑ray tube into the existing MPT probe platform, including a mechanically robust measurement window and optimized shielding.
• Quantitative laboratory validation: Systematic laboratory investigations on certified tailings reference materials, blind samples, and site‑specific tailings in order to quantify accuracy, detection limits, and the influence of matrix, grain size, and moisture on the probe signal.
• Site selection and case study: Identification of a suitable tailings pond, conclusion of a cooperation agreement with a mining operator, and execution of a preliminary investigation including sampling and hazard assessment as the basis for the field campaign.
• Field validation and modelling: Execution of an in‑situ measurement campaign, validation of the field data by comparison with laboratory reference analyses, and development of a geochemical model of CRM distribution in the tailings pond for a first assessment of the resource potential.  
• Application, guidelines, and knowledge transfer: Development of a Standard Operating Procedure (SOP) for probe deployment, implementation of a SWOT analysis (strengths, weaknesses, opportunities, threats) including market and environmental aspects, and dissemination of results (open‑access publications, conference contributions, theses, and integration into teaching).

Work packages

• WP 1: Project management
• WP 2: Site selection for the case study
• WP 3: Development of the probe
• WP 4: Evaluation and validation of the probe in the laboratory
• WP 5: Evaluation and validation of the probe in the case study