Occupational ALARA Planning for Reactor Pressure Vessel Dismantling at Kori Unit 1

Abstract

Assessing workers’ safety and health during the decommissioning of nuclear power plants (NPPs) is an important procedure in terms of occupational radiation exposure (ORE). Optimizing the radiation exposure through the “As Low As Reasonably Achievable (ALARA)” principle is a very important procedure in the phase of nuclear decommissioning. Using the VISIPLAN 3D ALARA planning tool, this study aimed at assessing the radiological doses to workers during the dismantling of the reactor pressure vessel (RPV) at Kori NPP unit 1. Fragmentation and segmentation cutting processes were applied to cut the primary component. Using a simulation function in VISIPLAN, the external exposure doses were calculated for each work operation. Fragmentation involved 18 operations, whereas segmentation comprised 32 operations for each fragment. Six operations were additionally performed for both hot and cold legs of the RPV. The operations were conducted based on the radioactive waste drum’s dimensions. The results in this study indicated that the collective doses decreased as the components were cut into smaller segments. The fragmentation process showed a relatively higher collective dose compared to the segmentation operation. The active part of the RPV significantly contributed to the exposure dose and thus the shielding of workers and reduced working hours need to be considered. It was found that 60Co contained in the stainless steel of the reactor vessel greatly contributed to the dose as an activation material. The sensitivity analysis, which was conducted for different cutting methods, showed that laser cutting took a much longer time than plasma cutting and contributed higher doses to the workers. This study will be helpful in carrying out the occupational safety and health management of decommissioning workers at Kori NPP unit 1 in the near future.

Towards a Semi-Autonomous Robot Platform for the Characterisation of Radiological Environments

“…3) Spectrum measurement: Besides the gathering of geometrical information using rotary wheel encoders mounted on the shaft of the DC motors and RGB and depth information from a LiDAR camera, the ARCHER platform is capable of obtaining radiological information from the environment by using data extracted from the Kromek GR1 CZT sensor 5 . To incorporate the radiological data stream in the ROS software framework, a ROS driver has been developed to communicate with Kromek sensors [29].…”

“…Furthermore, extensive characterisation of the environment that will be dismantled is a crucial step in keeping operator dose exposure as low as possible during the entire decontamination process. This early detection of radiological sources, and subsequent early removal of these high dose rate locations, will ensure strict compliance with the good practice of keeping radiological dose exposure as low as reasonably achievable, according to the ALARA standard [4], [5].…”