Enhancement of disposal efficiency for deep geological repositories based on three design factors − Decay heat optimization, increased thermal limit of the buffer and double-layer concept

IF 6.7 1区 工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY
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Abstract

This study investigates the enhancement of disposal efficiency for deep geological repositories (DGRs) based on three design factors: decay heat optimization, increased thermal limit of the buffer, and double-layer concept using coupled thermo-hydro-mechanical (THM) numerical simulations. Decay heat optimization is achieved by iteratively emplacing spent nuclear fuels having the maximum and minimum decay heat in a canister. Disposal areas can be reduced by 20 % to 40 % compared to the current reference disposal system in Korea (KRS+) in accordance with the combinations of the three design factors, alleviating challenges in site selection for the DGR. This study additionally identifies an optimal layer spacing of 500 m for the double-layer concept in the viewpoint of the buffer temperature, where thermal interaction between the upper and lower layers nearly disappears. However, determining the ultimate disposal and layer spacing requires engineering judgement, considering not only the thermal performance of the DGR but also various factors such as cost and difficulties of the construction and rock mass stability. DGRs designed with an increased thermal limit of the buffer poses a greater probability of rock mass failure around disposal tunnels and deposition holes due to elevated thermal stresses. Densely arranged heat sources for the DGRs with enhanced disposal efficiency lead to larger temperature increase even at the far-field scale, raising a possibility of thermally driven fracture shear activation with associated hydraulic, mechanical, and seismic changes.

基于三个设计因素--衰变热优化、缓冲区热极限提高和双层概念--提高深层地质处置库的处置效率
本研究利用热-水-机械(THM)耦合数值模拟,研究了基于三个设计因素(衰变热优化、缓冲器热极限提高和双层概念)的深地质处置库(DGRs)处置效率的提高。衰变热优化是通过迭代将具有最大和最小衰变热的乏核燃料放置在筒中来实现的。根据三个设计因素的组合,与韩国目前的参考处置系统(KRS)相比,处置面积可减少 20% 至 40%,从而缓解了 DGR 选址方面的挑战。这项研究还从缓冲温度的角度为双层概念确定了 500 米的最佳层间距,在这个层间距内,上层和下层之间的热相互作用几乎消失。然而,确定最终的弃置方式和层间距需要工程判断,不仅要考虑 DGR 的热性能,还要考虑施工成本和难度以及岩体稳定性等各种因素。在设计时提高了缓冲区热极限的 DGR,由于热应力升高,导致弃置坑道和沉积孔周围岩体破坏的可能性更大。为提高弃置效率而密集布置的 DGRs 热源,即使在远场尺度上也会导致更大的温度升高,从而有可能产生热驱动的断裂剪切活化以及相关的水力、机械和地震变化。
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来源期刊
Tunnelling and Underground Space Technology
Tunnelling and Underground Space Technology 工程技术-工程:土木
CiteScore
11.90
自引率
18.80%
发文量
454
审稿时长
10.8 months
期刊介绍: Tunnelling and Underground Space Technology is an international journal which publishes authoritative articles encompassing the development of innovative uses of underground space and the results of high quality research into improved, more cost-effective techniques for the planning, geo-investigation, design, construction, operation and maintenance of underground and earth-sheltered structures. The journal provides an effective vehicle for the improved worldwide exchange of information on developments in underground technology - and the experience gained from its use - and is strongly committed to publishing papers on the interdisciplinary aspects of creating, planning, and regulating underground space.
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