Immobilization of radioactive fluoride waste in aluminophosphate glass:a molecular dynamics simulation

Molecular dynamics(MD) simulations were conducted to investigate the structural and chemical environment of aluminum in aluminophosphate glasses.Such glasses have the potential for application in the disposal of radioactive fluoride waste from molten salt reactors(MSR).Due to the risks of studying these materials and the limitations of realistic research conditions,MD simulations were used as an alternative method to study the vitrification of radioactive fluoride waste.In the past decades,aluminophosphate glasses have been studied and they exhibit certain favorable properties for high-level radioactive waste management.This work focuses on the effects of fluorine addition on structural changes in the glass.We observed that glass with composition P_2O_5–Al_2O_3–Na_2O–CaO exhibited a good performance in immobilizing fluoride at low F concentrations(approximately under25 mol%).Significant changes were observed where PO_3F_2 units replaced PO_3F units in the glass.The fourcoordinated AlO_4 units were increasingly converted into five-coordinated [AlO_xF_y] with the increasing F content.The radionuclide Sr in the simulation had the tendency to form six-coordinated octahedrons in the glass.We conclude that the structural changes resulting from the fluoridewaste added to aluminophosphate glasses does not adversely affect their chemical stability at relatively low F concentrations,i.e.,under 25 mol%.Hence,the use of phosphate glasses is a potential alternative method of fluoride waste disposal.

Radiological environmental impact analysis of a 2-MW thorium molten salt reactor during an accident

The thorium molten salt reactor–liquid fuel(TMSR-LF1) has inherent safety features. The accident occurrence possibility and their consequences are much lower for the TMSR-LF1 than that of traditional reactors.Based on accident analysis, the maximum credible accident and the radioactive source terms of the TMSR-LF1 were first estimated. Then, the total effective dose of the maximum credible accident was calculated. Based on calculations, the cover gas flow rate can significantly affect the radiation consequences of the maximum credible accident when it changes from 0 to 10 L/min. If no cover gas is flowing, a site-area emergency would be required within the range of 50–73 m from the reactor. In the case of cover gas flow, only an abnormal notification and an alert two emergency class would be required within the range of 50 m.

Analysis of tritium production in a 2 MW liquid-fueled molten salt experimental reactor and its environmental impact

Tritium release is one of the most concerning topics in nuclear power plants. Here, the tritium production in a 2 MW liquid-fueled molten salt experimental reactor(TMSR-LF1) was calculated by ORIGEN-S with an updated cross-section library generated by TRITON in SCALE 6.1.3 code system. The results show that the tritium production rate and normalized tritium production rate of TMSR-LF1 are 8.90x10^(11)Bq/day and4.45x10^(11)Bq/(MW day), respectively. The environmental impact of tritium was analyzed via PC-CREAM 08 with an assumed 36 % release rate of tritium referring to the molten salt reactor experiment. During normal operations, the maximum tritium concentration is 1.4 Bq/m^3 under normal condition, and the corresponding individual dose to the public is about 1 μSv/a; under extreme conditions, the maximum concentration and corresponding individual doses are 11.8 Bq/m^3 and 9 μSv/a, respectively.Ingestion is the main exposure pathway and accounts for62 % of the total dose. Of this, 35 % is from organically bound tritium.