CSAMT-Driven Feasibility Assessment of Beishan Underground Research Laboratory

TL;DR

This study assesses the feasibility of using CSAMT geophysical methods to evaluate a site for radioactive waste disposal in China's Beishan area.

Contribution

The study demonstrates CSAMT's effectiveness in high-resistivity environments for deep geological repository site evaluation.

Findings

A 600-meter-thick intact rock mass was identified at the Xinchang site.

CSAMT proved reliable for characterizing high-resistivity terrains in HLW repository assessments.

The study provides a technical framework applicable to similar geological settings globally.

Abstract

The safe disposal of high-level radioactive waste (HLW) is imperative for sustaining China’s rapidly expanding nuclear power sector, with deep geological repositories requiring rigorous site evaluation via underground research laboratories (URLs). This study presents a controlled-source audio-frequency magnetotellurics (CSAMT) survey at the Xinchang site in China’s Beishan area, a region dominated by high-resistivity metamorphic rocks. To overcome electrical data acquisition challenges in such resistive terrains, salt-saturated water was applied to transmitting and receiving electrodes to enhance grounding efficiency. Using excitation frequencies of 9600 Hz to 1 Hz, the survey achieved a 1000 m investigation depth. Data processing incorporated static effect removal via low-pass filtering and smoothness-constrained 2D inversion. The results showed strong consistency between observed and modeled data, validating inversion reliability. Borehole correlations identified a 600-m-thick intact rock mass, confirming favorable geological conditions for URL construction. The study demonstrates CSAMT’s efficacy in characterizing HLW repository sites in high-resistivity environments, providing critical geophysical insights for China’s HLW disposal program. These findings advance site evaluation methodologies for deep geological repositories, though integrated multidisciplinary assessments remain essential for comprehensive site validation. This work underscores the feasibility of the Xinchang site while establishing a technical framework that is applicable to analogous challenging terrains globally.

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