3/23/2023 0 Comments Fukushima nuclear reactor meltdown![]() ![]() In March, not all workers possessed an alarm pocket dosimeter as many alarm pocket dosimeters were swept away by the tsunami. 5 The workers subjected to such exposure may inhale radiation particles due to respirator leakage, or may not have worn respirators because of inaccurate exposure assessments or inadequate emergency operations. 7 The maximum estimated exposure per worker was 670.4 mSv. In March, six workers received a high internal exposure of over 200 mSv as measured by a whole-body counter. 4 Table 1 shows the external, internal and total exposure of the workers to radiation from March to May 2011. The highest level of environmental exposure of radiation was recorded as 3130 μSv/h at the monitoring post at the central gate of Fukushima Dai-ichi NPP. 5 Women were not allowed to enter the plant after the accident.Īfter the explosion of reactor 1 on March 12, reactor 3 on March 14, reactor 4 on March 15 and the exposure of the fuel rods at reactor 2, radioactive materials were released into the immediate environment and surrounding areas of Fukushima Dai-ichi NPP. Approximately 2000 to 3000 emergency response technical workers employed by TEPCO and technical-support companies were on the accident site daily until the end of year 2011. 4 Reactor stabilisation and water decontamination became the next priority. In the early phase of the accident, the first priority was to minimise the risk of reactor explosion and restore the cooling system by ensuring electrical power that was achieved on March 26. These tasks were part of a preliminary process towards the decommissioning of the Fukushima Dai-ichi nuclear power station which could take from 30 to 40 years. 3 To achieve these objectives, radiation levels at the site were monitored to avoid any additional release of radioactive materials, and clean-up of rubble was implemented while ensuring the safety and health of workers. ![]() The tasks of disaster response technical workers in Fukushima Dai-ichi NPP after the tsunami were to restore the cooling of reactors and the fuel pools, containment and treatment of water contaminated by radioactive materials, and mitigation of radioactive materials emission in the environment eventually achieving the cold shutdown of the NPP. ![]() The aim of this paper is to describe the greatly increased risk from hazards that disaster response technical workers faced because of the Fukushima Dai-ichi NPP disaster. During this period, numerous efforts were made to protect disaster response technical workers. On 16 December 2011, the Japanese government, the Tokyo Electric Power Company (TEPCO) and technical-support companies achieved cold shutdown of all the reactors stricken by the tsunami. 2Įfforts were made to achieve stable cooling of the nuclear reactors, and the release of radioactive materials was brought under control. The nuclear accident was assigned the maximum severity level of 7, which is equal to that of the Chernobyl disaster that occurred in 1986. Hydrogen explosions destroyed two reactor buildings and there was meltdown of the reactor cores. 1 The loss of all alternating current (AC) electrical power, even from emergency generators, disabled cooling functions and the supply of recycled water. Fukushima Dai-ichi nuclear power plant (NPP) was heavily damaged by the tsunami that resulted from the 9.0-magnitude earthquake which occurred off the coast of eastern Japan on 11 March 2011. ![]()
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