Estudo do processamento de rejeitos radioativos sólidos compactáveis por plasma térmico/ Study of compactable solid radioactive waste processing by thermal plasma

O uso de radioisótopos para as mais diversas finalidades tem se intensificado e destacado pelos benefícios que proporcionam. A geração de energia elétrica, a indústria, a agricultura, a medicina diagnóstica e terapêutica, são alguns exemplos. Porém, essas aplicações têm como desvantagem gerar rejeitos radioativos e estes requerem tratamento apropriado para deposição final. Neste âmbito, entre as tecnologias promissoras para o tratamento de rejeitos radioativos sólidos compactáveis, a utilização de plasma térmico para gerar uma descarga de arco transferido por meio de eletrodos de grafite se mostra uma tecnologia capaz de reduzir substancialmente a massa e o volume de rejeitos radioativos após expô-los a temperaturas superiores a 3.000ºC. Os resultados obtidos se mostraram bastante satisfatórios, alcançando aproximadamente 100% de redução em 30 min de processo. Esforços futuros devem ser empregados para maior confiabilidade do sistema, eliminação de radionuclídeos voláteis no efluente gasoso e otimização completa da operação.

Radiation survey around “the 30th shipyard” company: 30 years after the accident

Introduction. The objective of this work was the radiation survey in the vicinity of “The 30th Shipyard” Company. The studies were carried out during the period between 2014 and 2016 within the supervision area and in the area of the radioactive trace formed after the accident of 1985 in the nuclear submarine.Material and methods. The following methods were used in the course of the survey: pedestrian gamma surveys, gamma spectrometry measurements of radionuclides using a gamma spectrometer, and radiochemical extraction of 90Sr, followed by measurement of its activity at radiometric installations.Results. Gamma ambient dose equivalent rate within the supervision area beyond the radioactive trace varies within the range between 0.09 and 0.18 µSv/h. The specific activities of 90Sr, 137Cs, and 235U in soil do not exceed 11, 34, and 5.8 Bq/kg, respectively. The specific activity of 60Co in the soil of the Dunay village is lower 0.42 Bq/kg and does not exceed 4.9 Bq/kg at the rest part of the supervision area. The area of the radioactive trace limited by 0.13 µSv/h iso-line does not exceed 0.5 km2, while that limited by 0.3 µSv/h iso-line - 0.0063 km2. Within the area of the trace, the highest value of the gamma dose rate accounts for 0.60 µSv/h. Soils contaminated with emergency radionuclides do not belong to solid radioactive waste. Emergency radionuclides migrated in soil up to 20 cm depth. Today, 137Cs is firmly fixed in the soil. 40-45% of 60Co activity is in acid-soluble form. Under specific conditions, it can migrate deep into the soil and be accessible to plants.Conclusions. Within the supervision area of “The 30th Shipyard” Company, except for the area of the radioactive contamination trace induced by the accident, the radiation situation is the same as that in the area of the Primorskiy Krai. The soil of the radioactive trace does not belong to solid radioactive waste. In the future, the improvement of the radiation situation on the trace will be mainly due to the physical decay of radionuclides.

New methodological approaches in solving certification problem of historical solid radioactive waste sent for burial from Chornobyl Nuclear Power Plant

Two methodological approaches for radioactive waste (RAW) certification used in RAW management systems in Italy and France, are addressed. Their applicability was assessed in solving certification problem of historical waste accumulated at the Chornobyl NPP in comparison with the standard methods recommended by the IAEA. Testing new methodological approaches was carried out on the example of solid RAW (SRW) of operational origin, which were previously studied for the content of 24 radionuclides within their composition. The procedures for testing researchable methods have used the criteria for SRW acceptance for burial valid in SRW Treatment Plant, which met their current provisions and those ones planned for approval. It was established that the use of quantitative criteria applied in the algorithms of studied methodological approaches for radwaste certification can significantly reduce overestimation degree of summary activity of waste packages by way of removing from the list of difficult-to-measure radionuclides, whose presence can be neglected in view of negligible risk of exceeding the activity limits established for them. The methodological approaches addressed in this work allow optimizing radionuclide contents subject to mandatory measurement, or calculated determination of their activity in waste packages, and can be recommended to solve the problems when characterizing ChNPP’s historical waste transported for their final disposal.

Conditioning of Solid Radioactive Waste Using Cement Matrix

The article discusses solid radioactive waste conditioning using cement matrix. It considers grouting methods for the waste of different composition and fragment size. It provides cement formulations for various types of waste being cemented by mixing, impregnation and pouring. The study shows that the impregnation method can be considered as a most effective option for solid waste conditioning using cement mortars.