China has achieved a major engineering milestone in the construction of the Beishan Underground Research Laboratory (URL) for geological disposal of high-level radioactive waste (HLW). On December 26, 2025, the project team successfully completed the excavation of the world's first deep, continuous small-radius, steep spiral ramp by a tunnel boring machine (TBM) named Beishan No. 1, which marked the completion of the underground main structure of Beishan URL. The Beishan URL, comprising “one spiral ramp + three vertical shafts + two horizontal experiment levels” (Figure 1), is a flagship scientific facility to develop geological disposal technology for HLW—a fundamental challenge of nuclear energy development. As an important component of China's closed nuclear fuel cycle innovation system, the Beishan URL will fill the gap in China's underground in-situ research and development platform and equipment for HLW disposal technology after its completion. Thus, the Beishan URL can serve as an experimental platform and a foundation for overcoming the global challenge of geological disposal of HLW.

China has built industrial-scale disposal facilities for low- and intermediate-level radioactive wastes at three sites: the Longhe repository at Jinta in northwestern Gansu province; the Beilong repository near the Daya Bay nuclear plant in Guangdong province; and the Feifengshan repository in Sichuan province. The Beishan URL is located in the remote Beishan area of the Gobi Desert in northwestern Gansu province. Thus, the Beishan URL and the abovementioned facilities form China's closed nuclear fuel cycle technology innovation system.

The safe disposal of nuclear wastes, particularly the high-level waste, is a real challenge in the world, although nuclear energy is considered a clean and efficient energy source. The radioactive waste is classified as low- and intermediate-level wastes, which account for about 99% in volume. Those wastes can decay to harmless levels in several hundred years. The high-level radioactive waste shares only 1% in volume, but its decay time to a harmless level is hundreds of thousands of years. Thus, safe and permanent disposal of the HLW is required in a deep underground geological formation. The best solution is to isolate the high-level waste in 500–1000 m underground.

The Beishan URL is one of China's major national scientific projects listed in the 13th 5-Year Plan and was approved by the China Atomic Energy Authority in 2019. It is an area-specific URL or a 3rd Generation URL. Its primary mission is to evaluate the site suitability to develope disposal technology for the long-term, safe isolation of HLW at depths of 500–1000 m. The ground surface facilities of this laboratory cover 247 ha. The underground complex has a total structural volume of 514,200 cubic meters, with 13.4 km of tunnels.

China has been conducting site selection for a geological repository for HLW since 1986, culminating in the confirmation of the Xinchang granite site in the Beishan area of northwestern Gansu province as the site for URL in 2018. More than 100 boreholes have been drilled to understand the complex geology of the Beishan area. A ground-breaking ceremony for the construction of the Beishan URL was held in June 2021; the URL is scheduled for completion in 7 years (2021–2028), followed by a 30-year operational period for in-situ experiments and technology development. A full-scale HLW geological repository could be constructed nearby by 2050 if the research outcome confirms the site suitability.

The underground facility of this laboratory comprises one spiral ramp, three vertical shafts, and two horizontal experiment levels at depths of 280 and 560 m. The newly excavated spiral ramp represents a formidable engineering feature. The spiral ramp descends to a planned maximum depth of 560 m with a diameter of 7.03 m, a total length of 7000 m, and a gradient of about 1:10. The construction of the ramp faced multiple world-class challenges: excavating through extremely hard granite rock (130–260 MPa in uniaxial strength); navigating the tight turns with a 100-m-long TBM (Figure 2); managing the steep slope demands on descending, muck transportation, and directional control; and ensuring worker safety at great depths.

In order to excavate the steep and curved spiral tunnel in the extremely hard granite rock with a limited excavation damage zone at Beishan URL, the TBM “Beishan No. 1” (Figure 3), a first-of-its-kind, ultra-hard rock TBM was developed by a Chinese consortium led by the Beijing Research Institute of Uranium Geology (BRIUG) and China Railway Construction Heavy Industry Corporation. Since the official commencement of tunneling on January 1, 2023, the Beishan No. 1 TBM has continuously operated for over 1000 days and successfully completed all seven 255-m small-radius turning sections and eight straight sections, achieving a cumulative advance of nearly 7000 m. The highest daily advance reached 21.6 m and the highest monthly advance reached 342 m. Remarkably, the tunneling process has achieved centimeter-level damage control to the surrounding rock, which can ensure the long-term integrity of the host rock and reduce the potential for future radionuclide migration through the excavated damage zone (EDZ) (Figure 4).

The Beishan URL has been constructed through wide collaborations and parallel scientific experimentation. The team has adopted a “strong core, extensive collaboration” approach, involving over 40 domestic and international research institutes and university teams. This approach has yielded internationally leading innovations in highly efficient hard rock excavation, high-performance tunneling with small-radius curves, continuous muck transportation by belt conveyor, and precise three-dimensional directional control during the spiral ramp excavation. The Beishan URL not only fills a critical gap in China's infrastructure for HLW disposal R&D but also serves as a collaborative hub. In October 2021, the International Atomic Energy Agency (IAEA) designated BRIUG as its first collaborative center on geological disposal of HLW, underscoring the global significance of this project. In September 2024, the China Atomic Energy Authority announced that it would open 12 nuclear research facilities to the international community, and Beishan URL is one of them.

By tackling the “hard, curved, steep, and deep” engineering challenges of spiral ramp excavation, the Beishan project has provided a replicable and scalable solution for future deep geological research and construction projects worldwide, contributing substantially to the ultimate goal of safe and permanent nuclear waste isolation for tens of thousands of years.