Dr. LIU Chunli is a professor from Peking University, College of Chemistry and Molecular Engineering. Besides teaching Radiochemistry and General Chemistry, he conducts research in nuclear environmental chemistry, so he has an in-depth understanding of adsorption, diffusion, migration and species distribution of radioactive isotopes in the environment.
Is uranium pollution common in the outside environment? Are there such areas in China? Are there any research institutes that specialize in this field.
Uranium, which is an element distributed in earth’s crust, is not so rare as we once thought. Both geological activities and human disturbances may result in changes in uranium distribution, so that some areas show relatively higher uranium contents. A case in point is Punjab in India. In China, the contents of uranium are higher than background values around the uranium mines in Jiangxi and Hunan and around rare earth mines in Inner Mongolia and Guangdong.
The research institutes that have deep insights into uranium and uranium pollution in China include the Uranium Geology and Mining Department of East China University of Science and Technology, the Institute of Nuclear Industry Geology, and the Beijing Research Institute of Chemical Engineering and Metallurgy that engages in uranium exploration, uranium mining and industrial applications.
During the entire process, from uranium mining, processing and utilization to reprocessing, at which step is uranium leakage and uranium pollution most likely to occur? What threat does uranium pose to humans?
Generally speaking, it is during uranium mining and reprocessing of high-level radioactive waste that uranium leakage is most likely to occur. For uranium mines, uranium concentrations are naturally higher, and the introduction of water in the process of exploitation further aggravates uranium leakage into the biosphere. As for reprocessing plants, they usually deal with high-level radioactive waste, so large amounts of low-level radioactive water and waste are released, which are prone to enter the environment.
In terms of radiation threats, since uranium mainly produces α-radiation, whose penetrating power is the lowest of all radioactive rays, uranium does not pose severe threats as long as it does not enter the body. But once having entered the human body, uranium, whether as a heavy metal or as an internal radioactive source, may well result in severe damage to various organs, including the liver and kidneys.
What kind of controls does the Chinese government impose over radioactive elements such as uranium?
The control is extremely strict—the whole process, from exploitation and utilization to reprocessing, is completely carried out or supervised by national institutions.
For research purposes, only those laboratories which have a qualification higher than “radiochemistry lab” are allowed to conduct experiments with uranium. For every step from purchasing to waste recycling, experimenters need to report and strictly control the radiation dosage. Take our own laboratory as an example, before purchasing uranyl ions, we need to report to higher authorities half a year in advance and the amount of uranyl ions we acquire is very limited, only barely covering the basic research needs.
Currently, what methods are employed to deal with uranium pollution? What are their pros and cons?
Both physical and chemical methods are adopted. For instance, with cement solidification, uranyl ions could be immobilized in cement; with the soil replacement method, the polluted soil surface layer is replaced by clean topsoil and the contaminated soil is buried deeper. The costs of these methods are so high that only national institutions could afford them. Other methods, such as plant adsorption, are not ideal despite their comparatively low costs because they are quite time-consuming.
For the institutes whose uranium consumption is low, a common method for coping with uranium waste is to solidify substances that contain uranium and pass them on to professionals for centralized processing.
Not only could uranium and its radiation cause damage to human health, they may also arouse social unrest. Judging by the wave of panic buying of iodised salt after the Fukushima Daiichi nuclear disaster in 2011, we could see that the general public is ignorant of uranium and its threats. So what do you think of the work on popularization of such knowledge in China? Have you carried out any popular science work?
Admittedly, the popularization work in China is far from satisfactory. On one hand, the number of researchers in China is limited so there are not enough people to do such work; on the other hand, the average knowledge level of the general public is comparatively low (from the Internet you could see that many people only have a poor scope of knowledge, no higher than secondary school) so it takes a long time for them to understand this.
For popularization, we offer a radiochemistry course in Peking University and hold lectures in other schools, which all receive good feedbacks.
What’s the frequency of safety training about uranium and other radioactive substances in your lab? Have there been any accidents in your lab or in the Department of Applied Chemistry? Would you please introduce the plans in place for cases of emergency?
We are very strict with safety training. Every new student is required to pass the theoretical and experimental courses in radiochemistry, and they need to receive safety training. After they enter the lab, we will supervise and examine the experiments from time to time. Every year we organize two large-scale safety trainings.
So far, there haven’t been any accidents. In case of emergency, whoever notices the situations should inform the teacher immediately, who will arrange proper treatment measures according to the level of radiation.
If the situation is beyond our handling ability, we will report to the college and the college will then report to the Radiation Protection Group, ensuring that professionals will come to deal with the accident within 8 hours.
Dr. LEI Yi’an is an associate professor from Peking University, School of Physics. He specializes in nuclear theory, quantum mechanics, computational physics and so on. What’s more, he has popularized nuclear power and nuke industry in public and has a unique view on the relevant questions.
China now has several nuclear power stations in service, such as the Daya Bay Nuclear Power Station. Would you please introduce some basic information about the construction, operation and retiring of domestic nuclear facilities? How are they retired?
There is a lot of confidential data about this, but you could find some general information about it too. When a nuclear power station is retired, high-level radioactive waste is taken out first and buried deep in the soil where there is no underground water. The low-level radioactive waste generated during construction and production is kept for several years until most of their radioactive components decay, after which it is demolished and buried.
Nuclear power is a kind of clean energy, why do you not have an optimistic perspective about it?
The word ‘clean’ you mentioned simply refers to not emitting greenhouse gases into the atmosphere, but the use of nuclear energy often generates lots of radioactive waste. Could this be called ‘clean’? Whether a technique could be applied for long depends on the economic profits it brings. Nuclear power stations need to be planned, constructed, operated and maintained. After retirement, they also need complex processes to dispose of the accumulated waste. The whole process requires lots of human and material resources; so the cost is very high. Although the field of nuclear power is quite mature in many western countries, we could look at their newly constructed nuclear facilities. Take the United States as an example, no more than ten stations have been constructed in the past several decades. In other words, the United States also does not think nuclear energy is the trend for future developments. So the development of nuclear energy is grinding to a halt.
Is nuclear pollution an urgent problem?
There is a non-negligible amount of uranium contained in earth’s crust. Many associated uranium deposits in mines are brought to the surface by humans. Uranium itself is not an important source of pollution, but its decay products such as radon are much more alarming. Owing to the low abundance of radon, there are no satisfying disposal measures for it. Therefore, radon is more of a potential threat than uranium. Under the influence of these decay products, the background radiation in human settlements has been increased significantly. The decay products of uranium are more worth being concerned about.
