Government Team Releases Draft Revisions to Mid-to-Long-Term Decommissioning Roadmap for Fukushima Daiichi NPPs

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On September 1, the Japanese government's core team dealing with the decommissioning of the Fukushima Daiichi Nuclear Power Plants (NPPs) released draft revisions to the Mid-to-Long-Term Roadmap toward decommissioning.

The last revision to the roadmap had been in June 2015. There will be no changes to the framework of the decommissioning work overall, which is to be accomplished three to four decades after Step 2 in the roadmap is completed, as described in a report from December 2011.

Target schedules for each measure and activity will be included in the roadmap after precise examinations are carried out that take various items into account, such as: (a) progress since the previous revision, (b) current status, and (c) feasibility evaluations by the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) of methods for removing fuel debris. The revised roadmap will be officially finalized at the inter-ministerial council for contaminated water and decommissioning issues.

As for the removal of fuel debris, a step-by-step approach will be taken involving gradual expansion of the work. Based on a technical proposal by NDF, an uncovered removal method will be pursued initially, rather than water-covered removal.

First, fuel debris at the bottom of the Primary Containment Vessel (PCV) will be removed from the side of the PCV. As there are many uncertainties, however, revisions to the plan will be made based on experience and new information. For example, water-covered removal (already evaluated by NDF) may be reconsidered for its shielding effects. The target for starting the removal of fuel debris from the first unit is 2021, as now stated in the roadmap.

Meanwhile, measures against contaminated water are to be implemented in accordance with the basic policy of removing the source of the contamination, isolating groundwater from contamination sources, and preventing leakage of the contaminated water. The aim is to complete the treatment of all contaminated water accumulated in the reactor buildings by 2020.

As for the removal of fuel in the fuel pools at Units 1 to 3, schedules will be reviewed in light of immediate on-site work. The timing of the start and completion for each reactor is now being considered.