Assessment of tephra fallout hazard for the nuclear facilities of China - a case study of Taishan Nuclear Power Plant (TNPP)

Xu, Jiandong

Abstract:

In 2012 the Atomic Energy Commission issued the specific guide for volcanic hazards in site evaluation for nuclear installations (No. SSG-21), which was prepared under the IAEA’s programe for safety standards. It supplements and provides recommendations for meeting the requirements for nuclear installations established in the safety requirements publication on site evaluation for nuclear installations in relation to volcanic hazards.

Starting from the 80’s of last century, China launched the national plan of constructing nuclear power plants along the coastline region in east China. Currently, for some of these candidate sites, nuclear facilities have been installed and in operation, but for some others nuclear power plants are still under construction or in site evaluation. To meet the safety standards for volcanic hazard, we followed the IAEA SSG-21 guidelines, and developed a technical method in order to evaluate the potential volcanic hazard caused by tephra fallout from the explosive eruptions which are within the distance from which the candidate site is likely effected during the potential eruption in the future.

Taishan Nuclear Power Plant (TNPP) is geographically located at Yaogu village of Chixi town at Taishan city, Guandong Province, China. Qiongbei volcano field is situated at the northwest corner of the South China Sea and in about 350 km SW to the TNPP with a total coverage of more than 7000 km² of lava flows. Qiongbei volcanic rocks are basalt in composition and most of the eruptions belong to Stromboli type and thus the scales of the explosive eruption are generally small. Based on the previous studies, the last eruption occurred in about 2,000 years ago with the estimated eruption column of about 5 km high.

Using the tephra diffusion model and the high-altitude wind dataset for the period 2000 to 2015 from Haikou Meteorological Station, we performed simulations of tephra deposits by using parallel computing technique and constructed the tephra fallout probability maps for thickness thresholds at 1 cm. We selected 10^-4 (the Holocene volcanoes of 10,000 years) as the occurrence probability of future volcanic eruption events. Finally, we obtained the risk probability graph of tephra thickness of 1 cm in Qiongbei volcanic field.