Work began in August to dismantle a highly contaminated exhaust stack at the Fukushima Daiichi nuclear plant in Japan.
The unstable exhaust stack is highly contaminated by radiation ao work is being undertaken by remote control. The work was originally planned to start in March, but the project faced delays, in part due to a failure to confirm design plans that led operator Tokyo Electric Power Company (Tepco) to deploy a crane that was not suitable for the task. The exhaust stack, which is 120m tall and 3.2m in diameter, served Fukushima Daiichi 1 and 2.
At the time of the March 2011 accident, vapour containing highly radioactive substances was released through the exhaust stack. Later, metal poles used to support the chimney were found to have been damaged following a hydrogen explosion at the unit 1 reactor.
Immediately after accident at Fukushima, radiation levels at the base of the chimney exceeded 10 sieverts per hour. By 2015, radiation levels were still around 2Sv/hr, the highest among all outdoor areas of the plant. Radiation levels at the base of the stack are still believed to be too high for human exposure. There are also concerns that the chimney could collapse.
The dismantling system was developed and is being operated by construction company Able Co, based in Okuma, Fukushima Prefecture. It was hoisted into place by a 750-ton crane.
A remote control room has been set up in a large remodelled bus located about 200m from the site. Workers will operate the cutting equipment while watching footage from 140 video cameras.
The dismantled pieces of the chimney will be stored in the grounds of the Fukushima Daiichi.
The work began at noon on 1 August. The goal is to complete dismantling the upper part of the stack by the end of March 2020, but strong winds and other weather conditions could cause delays.
Photo: Exhaust stack at Fukushima Daiichi 1&2 pictured during a radiation survey in 2016 (Credit: TEPCO)
