Environmental impact on the Korean peninsula due to hypothetical accidental scenarios at the Haiyang nuclear power plant in China

Analysis of the impact of various vertical release patterns on the atmospheric dispersion and total deposition of 137Cs from Chernobyl Nuclear Power Plant accident

The Chernobyl Nuclear Power Plant (NPP) catastrophe of 1986 has been a milestone in the use of nuclear power for energy generation. After the accident, various topics have been discussed to evaluate the details of occurrence of the event and to understand its impacts on human, animal and plant life. One of the most controversial topics is the release height and homogeneity of radionuclides at release point in the atmosphere. Currently, there exists no definitive decision on the release height and vertical distribution pattern of radionuclides released from the Chernobyl accident. Based on this premise, this study focuses on the analysis of various possible release patterns along the vertical dimension and the potential influences on the atmospheric dispersion and total deposition with particular reference to ¹³⁷Cs. For this purpose, some release pattern functions following uniform, Dirac delta, exponential, log-Pearson type III, and cumulative distribution functions along the z-axis were used to simulate the dispersion of ¹³⁷Cs released from the accident site. A total of 22 release patterns are produced using different maximum release heights (2000, 3000, and 4000 m). A Lagrangian particle dispersion model, FLEXPART, was then used to conduct simulations for these conditions to assess most coherent dispersion and deposition patterns. Model results from each release function were plotted, compared with each other and verified with measured data. In the functions where the release predominantly existed at lower levels, more extreme values were observed in the close vicinity of the source. Consequently, Dirac delta, log-Pearson type III (1), and exponential functions can be used as worst-case conditions at local scale. On the other hand, simulations also revealed that contamination spread to wider areas in cases where the release occurred from higher levels of the atmosphere. Therefore, log-Pearson type III (2) and cumulative distribution function can be considered more significant concerning a wider distribution of affected areas.

Dose and risk estimation of Cs-137 and I-131 released from a hypothetical accident in Akkuyu Nuclear Power Plant

The construction of Akkuyu Nuclear Power Plant (NPP) was launched in 2018 and the plant is expected to be operative by the year 2023. Being situated in the Mediterranean coastline, Akkuyu NPP will be the first nuclear power generation facility in Turkey. The plant will have four Russian VVER-1200 type pressurized water reactors with a total installed capacity of 4800 MW. In this study, atmospheric dispersion and ground level deposition of Cs-137 and I-131 released from a possible accident in Akkuyu NPP was estimated using a Lagrangian particle dispersion model, FLEXPART, for different time periods representing relatively extreme meteorological conditions for Mersin. The source term used in simulations was assumed the same with that of the Chernobyl NPP accident that occurred in 1986. In addition, cumulative dose and risk values were calculated from FLEXPART output datasets considering potential exposure pathways such as inhalation, ground-shine exposure and cloud-shine exposure. The results were further analyzed with python codes and dose and risk maps were created for local and regional scales. According to results of the study, it was found that the vicinity of Mersin and Central Anatolia were simulated to be the most significantly affected areas from the accident under both scenario conditions. The northern and western parts and all coastlines of Turkey were simulated to be more contaminated in the simulations conducted under December 2009 conditions, whereas southern and western parts of Turkey and some parts of Middle East countries like Syria, Iraq and Lebanon were simulated to be comparatively more contaminated under August 2010 conditions. The results indicated that radioactivity levels exceeding 100 kBq/m² were observed near the accident site under both scenario conditions. Values exceeding 10 kBq/m² level were simulated in western Turkey in the first scenario whereas similar values were found in eastern Turkey in the second scenario. Furthermore, the results indicated 7-day thyroid dose values ranging between 0.10 mSv and 10.0 mSv in western and eastern parts of Mediterranean region for the first and the second scenario, respectively. Similarly, 1-year effective dose of only Cs-137 ranged between 0.1 mSv and 1.0 mSv around Akkuyu NPP site in both scenarios. The results revealed that meteorological conditions were among the most important parameter for the fate and transport of radioactivity originating from such a catastrophic event.