On March 17, 2025, Chubu Electric Power made history by commencing the dismantling of the reactor pressure vessel at Unit 2 of the Hamaoka Nuclear Power Plant located in Omaezaki City, Shizuoka Prefecture. This process marks the first time dismantling has begun at any commercial reactor within Japan, setting the stage for what many are calling the dawn of a 'major decommissioning era.'
During the initial dismantling process, the upper lid of the reactor pressure vessel, which weighs approximately 55 tons and measures about 8 cm thick, was carefully removed using crane equipment. According to Chubu Electric, this significant first step involves cutting the lid down to smaller sections of approximately 4 meters long and 1 meter wide. This more granular dismantling is set to begin on March 27, 2025, with the overall removal process expected to conclude by July 2025.
Unit 1 and Unit 2 of the Hamaoka Nuclear Power Plant are both boiling water reactors, with Unit 1 commencing operations back in 1976 and having an output capacity of 540,000 kilowatts. Meanwhile, Unit 2 entered service two years later and boasted greater power output at 840,000 kilowatts. Due to updated seismic regulations introduced after the 2006 earthquake, which increased the financial burden of required safety upgrades, the decision to decommission these reactors was officially taken by Chubu Electric Power in 2008. Dismantling operations began relatively soon after, with the groundwork laid for completing the task.
While this dismantling operation has gained attention for its historic significance, underlying technical challenges remain. The decommissioning of the reactor—being the most delicate phase of the entire procedure—will demand advanced techniques, especially considering the high radiation levels present. To manage the hazardous conditions, specialized robots will be deployed to operate remotely, ensuring the safety of the workers involved during the project.
Chubu Electric remains focused not only on safely dismantling the reactors but also on managing the resulting waste effectively. The entire process is expected to generate around 450,000 tons of metal and concrete waste. Out of this, approximately 20,000 tons will be classified as 'low-level radioactive waste.' The waste generated during decommissioning will be structured according to contamination levels: L1 (control rods), L2 (parts of the reactor pressure vessel), and L3 (peripheral piping). Chubu Electric notes, though, as of now, the disposal site for this waste generated by the two units remains undecided, causing concern about the environmental impact.
Once dismantling is completed, radioactive waste materials will remain on-site until the disposal methods can be finalized. Regulations necessitate monitoring for several hundred years after burial, emphasizing the long-term responsibilities involved.
Looking back at the national scene, Japan has around 57 operational nuclear reactors, though only one facility—namely the Japan Atomic Energy Research Institute’s small research reactor 'JPDR', located in Ibaraki Prefecture—has completed its decommissioning, resulting in approximately 3,770 tons of low-level radioactive waste, which continues to be managed within the research institute's grounds.
Chubu Electric began work on Units 1 and 2 of the Hamaoka Nuclear Power Plant back in 2009. To date, fuel from the reactors has been transferred to Units 4 and 5 on-site, with unused fuel already removed from the property. The facility has undergone extensive decontamination work, including decommissioning turbines, generators, and some reactor building components since 2015.
Despite the challenges facing Chubu Electric and nuclear energy across Japan, the company remains dedicated to successfully managing these complex procedures with transparency and safety at the forefront. The completion of the dismantling of Unit 2 is set as the third phase of decommissioning, with Unit 1 scheduled for similar attention within fiscal year 2025. The reactor building’s removal is slated to kick off the fourth phase, anticipated to begin by fiscal year 2036, with total decommissioning expected to be finalized by 2042.
It’s evident through these efforts at the Hamaoka Nuclear Power Plant how the industry witnesses moments of reckoning—far from just histories of powering cities, this transition reflects the shifting narratives around nuclear energy and the commitment to safe decommissioning practices moving forward.