Treatments and conditioning of radioactive wastes

With the rapid development of its nuclear industry, China’s RAW manage­ment has gradually been improved over the past 20 years. In the 1950s, when the country’s nuclear industry had just begun to develop, the Chinese gov­ernment put forward the policy that radiation protection should be devel­oped before the nuclear industry became operational, which required that any work involving radioactivity must be accompanied by waste treatment capability and that any RAW discharge complies with the required stand­ards. Therefore, nuclear industry production and research facilities were all equipped with RAW treatment and storage installations for storage of dif­ferent categories of wastes in accordance with the categorization given in Table 22.4.

In the early years, the liquid and gaseous radioactive waste treatment processes, as part of nuclear production and research activities and as a component associated with the main production process, employed purifica­tion filtration, evaporation, and ion exchange among other practices. Such wastes were discharged into the atmosphere and surface water after meeting the national standards — ‘Radiation Protection Regulations’ (GBJ8-74) [11,12]. This standard was issued by the State of Ministry of Nuclear Indus­try, targeting the national regulations on the treatment and disposal of radioactive wastes. Those liquid and solid radioactive wastes that could not be discharged were stored. In general, in the process of nuclear facility construction and operation, the treatment of gaseous and liquid radioactive waste generally received due attention with practical treatment technology being employed. This played an important role in ensuring normal operation as well as environmental protection. All sorts of liquid wastes generated in the processes operating at each nuclear facility underwent solidification treatment. Evaporator residues of liquid LLW underwent bituminization and the resultant solidified forms, after packaging, were sent to a storage facility near Beijing. The programme for dealing with China’s legacy HLW is based on joule heated ceramic melters (JHCM) such as those used in Germany, Japan, the US and Russia operating at well over 1,100°C. However, opportunities exist in the future that waste streams from NPP from China may be more applicable to cold crucible induction melting (CCIM) technol­ogy, which has been developed intensively by France and Russia. From a materials point of view, selected glass compositions will be within the boro — silicate range adapted for current wastes and the envisaged future HLW streams. Large-scale research programmes and investment are also under way on the development of glass composite and ceramic waste forms.

With the construction and expansion of NPPs and the development of the radioactive waste management concepts of making safe disposal central, progress has been made in RAW treatment and conditioning technology and installation. NPPs in China now have liquid and solid RAW treatment facilities installed during their construction. NPP operators prepare RAW management programmes, which specify the assignment of responsibility for RAW management within each NPP. The Chief Manager of each nuclear operational organization acts as the primary person responsible for RAW management. The Chief Manager is responsible for providing suffi­cient resources to ensure effective implementation of the RAW manage­ment programme, and to ensure the national limits of radioactive effluents are complied with. This RAW management arrangement can be maintained and modified in a sustainable manner.

RAWs are managed according to their categories at NPPs. Based on the features of each NPP, the specific categorization schemes are developed and applied to the management of RAW arising from NPP operations. In general, concentrated liquid and spent ion exchange resins are solidified in cement, the waste arising from technology processes is held in storage after sorting and compression. Cement solidification proc­esses have been established in Daya Bay, QNPP II and Ling-ao NPPs to carry out cement solidification of liquid LILW, spent exchange resins and spent filter cartridges. Spent ion exchange resins produced at QNPP and QNPP III are currently stored temporarily and cemented waste forms are stored in waste storage facilities at such NPPs. The solid RAW gener­ated at NPPs is mainly stored in on-site facilities and the liquid wastes are stored in tanks. On the whole, the facilities for waste storage at NPPs are well constructed and in a good condition, and comply with current requirements.

In China, the NPP operators continue to carry out technology modifica­tions. QNPP upgraded the cement solidification installation and as a result the waste drum-filling coefficient increased from less than 79% to more than 90%. Guangdong Daya Bay NPP continues testing to improve the formula for cementation of its spent ion exchange resin so as to raise the waste loading capacity. Daily operational practices include measures to control waste generation. Personnel awareness of waste minimization is reinforced through training and education activities. Suitable operational processes are employed and technological and administrative measures are envisaged to make waste generation ALARA. Moreover, detailed work plans and arrangements to control waste generation during maintenance include: [37]

• enhanced recovery and re-use by dismantling the disused intermediate and high efficiency filters, and returning metal frameworks to manufac­turers when the contamination is below clearance levels.

As of December 2006, the volume of solid LILW generated from China’s NPPs was 4773 m3.

Tracking solid RAW is an important aspect in its safety RAW manage­ment. Each NPP writes specific management procedures to require the tracking of its RAW. Each waste package is tracked by establishing a unique RAW record. The relevant information of the record includes origin of waste, type of waste, date of waste generation, radioactivity level in waste, quantity/volume of waste, temporary storage location, etc.

A main objective of RAW management is to minimize the generation of RAW in China. Compared with some countries, there is still potential to reduce waste generated at China’s NPPs. However, the minimization of RAW is a combined effort balancing factors of technology, safety and economy. China is taking additional actions in controlling the generation of the wastes, upgrading management practices, introducing advanced waste reduction technologies, promoting specialization and socialization in RAW treatment services.

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