Safety Evaluation Study On The Geological Disposal Of High-level Radioactive Waste

Nuclear power,which is a kind of efficient and clean energy resource,but the operation of nuclear power plants produces a large amount of nuclear wastes(also called radioactive wastes).These nuclear wastes can cause great harm to the environment if they are not handled properly.Thus,how to deal with these radioactive wastes remains a challenging problem.At present,there are considerable suitable disposal methods for low-and middle-level radioactive wastes,but it is still difficult to dispose the high-level radioactive wastes(HLWs)because of their toxicities and long duration of hazards.Whether high-level radioactive waste can be safely disposed is not only the world problem,but also the key to the sustainable development of China's nuclear industry.The disposal of high-level radioactive waste is a huge and complicate system engineering,which involves the interdisciplinary integration of many disciplines.At present,all the countries with nuclear industry in the world are actively exploring new high-tech research topicson the safe disposal of HLWs,but there are no HLWs repositories in operation so far.The disposal method most commonly used is the deep geological disposal,i.e.,solidifying the waste and then burying it deeply in the underground repository of multi-layer barrier system.The safety assessment is an important part of geological disposal of the HLWs,and also the key to building public confidence.The construction of underground laboratory in China is being started,thus it is urgent to carry out the safety assessment study,which will lay a good foundation for the subsequent safety assessment of the repository.Based on the latest progress at home and abroad,in this paper,we focused on the key scientific issues,and summarized the related characteristics of the safety assessment of geological disposal of the HLWs.Furthermore,with aims to provide suggestions and references for further development of safety evaluation of HLWs in China,we took Beishan pre-selection area of Gansu province as an example to conduct the safety assessment simulation study,which was based on the geological,hydrological and humanistic economic conditions of Beishan.In this simulation study,we used the Goldsim software that is a generally-used international safety assessment software of radioactive waste transport,and the Monte Carlo random simulation method to model the damage situation,and to estimate the radiation levels during the period of 1 million years after the closure of disposal repository with thestorage of 60000 waste tanks.Our results show that the effective dose of the Beishan disposal repository within one million years is lower than the international dose limit required,suggesting that this repository meets the safety requirements.However,it is worth noting that the research of China's safety evaluation of the geological disposal is still far from the international level,and cannot meet the needs of long-term geological disposal because of relatively weak foundation and lack of the key technology.Therefore,further studies are needed.