Uncertainty and sensitivity analysis of radionuclide migration through fractured granite aquifer

Zhengyang Du; Zhenxue Dai; Zhijie Yang; Sida Jia

doi:10.1016/j.jenvrad.2022.107020

Uncertainty and sensitivity analysis of radionuclide migration through fractured granite aquifer

J Environ Radioact. 2022 Dec:255:107020. doi: 10.1016/j.jenvrad.2022.107020. Epub 2022 Oct 1.

Authors

Zhengyang Du¹, Zhenxue Dai², Zhijie Yang³, Sida Jia¹

Affiliations

¹ College of Construction Engineering, Jilin University, Changchun, China; Institute of Intelligent Simulation and Early Warning for Subsurface Environment, Jilin University, Changchun, China.
² College of Construction Engineering, Jilin University, Changchun, China; Institute of Intelligent Simulation and Early Warning for Subsurface Environment, Jilin University, Changchun, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, China.
³ College of Construction Engineering, Jilin University, Changchun, China; Institute of Intelligent Simulation and Early Warning for Subsurface Environment, Jilin University, Changchun, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, China. Electronic address: yangzhijie@jlu.edu.cn.

PMID: 36194969
DOI: 10.1016/j.jenvrad.2022.107020

Abstract

The radionuclide migration in the high-level radioactive waste (HLW) disposal is usually predicted by numerical simulations for risk analysis of radionuclide contamination in a large scale of time and space. However, the uncertainties in radionuclide migration models and their associated parameters significantly affect the simulation results. In the present study, we first selected certain parameters and output data as independent parameters and risk metrics and performed a series of radionuclide transport models at a research site in Northwestern China. The models considered radionuclide migration in the equivalent porous medium with the mechanism of nuclide decay in an arbitrary-length decay chain, adsorption, advection, diffusion, and dispersion. Then 3000 Monte Carlo (MC) simulations were performed to carry out a set of uncertainty and global sensitivity analysis by coupling an uncertainty quantification tool with a radionuclide migration simulator. The results indicated that both hydraulic gradient and hydraulic conductivity significantly influenced the risk metrics. Thus, it is critical to obtain hydraulic gradient and hydraulic conductivity data under the same economic conditions. We applied the multivariate adaptive regression spline (MARS) method to generate response surface models representing the relationships among independent parameters and risk metrics. Calculations of the risk metric distribution ranges revealed that the peak release doses would appear at 0.40 and 0.79 million years, and their values will be in the range of 4.7 × 10^-7-1.93 × 10^-6 Sv/a. Uncertainty and sensitivity analysis results of radionuclide contamination in the fractured granite upon which HLW is disposed can improve simulation and prediction accuracy for radionuclide migration.

Keywords: High-level radioactive waste; Monte Carlo simulation; Radionuclide migration; Sensitivity analysis; Uncertainty analysis.

MeSH terms

Groundwater*
Models, Theoretical
Radiation Monitoring*
Radioisotopes
Refuse Disposal* / methods
Uncertainty
Water Movements

Substances

granite
Radioisotopes