Parametric Analysis of Radiological Impact from Hypothetical Accident Scenario at the Sanmen Nuclear Power Plant

Growing demand for energy has positioned nuclear power as a crucial alternative, yet radionuclide emissions present significant environmental and health risks, necessitating precise radiological assessments. Previous studies have emphasized stability class effects, but have often neglected key parametric factors, such as stack height, stack diameter, source geometry, and effluent temperature.

This study employs the HotSpot code to simulate the total effective dose (TED), target organ committed dose equivalent (TOCDE), and ground deposition under a hypothetical loss-of-coolant accident at the Sanmen Nuclear Power Plant. Elevated area sources provide the highest mitigation efficacy near the release point, increasing the mitigation ratio from 0.003 at 0.1 km to 0.114 at 10 km, as the effectiveness declines with distance. Point sources yielded the highest TED, with the thyroid receiving 25 Sv unmitigated and 4.5 Sv mitigated of ¹³¹I within 0.1 to 0.8 km. TED strongly inversely correlates with stack height, peaking at 0.32 Sv at 30 m for a 10-m stack, while a 100-m stack significantly reduces exposure (3.14 × 10^–4 Sv at 10 km). Increasing the stack diameter from 1 to 5.5 m decreased TED from 1.23 × 10^–1 Sv to 9.45 × 10^–2 Sv over 10 km.

Higher effluent temperatures enhance dispersion, reducing TED and TIAC. Cesium-134 dominates TED, while noble gases exhibit minimal deposition. A TOCDE analysis highlighted ¹³⁴Cs as the primary skin dose contributor (12 Sv) and ¹³¹I as the thyroid dose contributor. These findings provide critical insights for optimizing emission controls, mitigation strategies, and nuclear emergency planning.