The centre would be built on the Powys and Neath Port Talbot boundary. Neath Port Talbot Council granted conditional approval to the application to the planning application, submitted by Welsh ministers, earlier this week.
The train, rail infrastructure and technology testing facility known as the Global Centre for Rail Excellence (GCRE), is intended to support innovation in the UK and international rail industry, including the testing of cutting-edge, green technologies.
The GCRE will cover an area of around 475 hectares and will consist of two looped test tracks, one being an electrified high speed rolling stock track (6.9km long) and the other being a low-speed infrastructure test track (4.5km). There will also be a dual platform test environment, operations and control offices, staff accommodation, shunter cabins and facilities for research and development, education and training.
The Welsh Government has been working in partnership with Powys and Neath Port Talbot councils to develop proposals for the GCRE, which will be located on the site of the Nant Helen open cast mine operated by Celtic Energy and the Onllwyn Washery Distribution Centre.
Councillor Rosemarie Harris, leader of Powys County Council, said: "This marks a vital step forward in this fantastic opportunity for jobs and technology in Powys and South-West Wales. The centre has the potential to boost investment and the economic well-being of the area. It supports our need to move to a low carbon society and bring more environmentally friendly industries to the area."
Councillor Iain McIntosh, cabinet member for economic development, added: "The planning decision paves the way for a possible £150 million investment in the region creating high quality jobs for the region with potential for a real jobs boost during the construction phase and beyond.
Members of the council's planning committee, which granted conditional approval of the GCRE yesterday (29th July) were told in a report the proposal had the full support of the council's Economic Development Service and that financial support that has been committed by both the UK and Welsh governments.