The Safety measures for Tokai Reprocessing Plant under the Decommissioning Stage in line with the upgraded regulatory standards

TRP Decommissioning Technology Development Department

After the Tokai Reprocessing Plant (TRP) has received approval for its decommissioning plan in June 2018 and transferred to the decommissioning stage, it still remains an amount of high active liquid wastes. Because it takes a considerable amount of time to complete the vitrification of the high active liquid wastes, and because the plant is located near the Pacific coast and is at risk from earthquakes and tsunamis, appropriate Safety Measures were implemented in accordance with the present risks on TRP and the upgraded regulatory standards which was revised in July 2013 based on lessons learned from TEPCO's Fukushima Daiichi Nuclear Power Station accident in 2011. Most of the radioactivity inventory in the TRP is involved in the high active liquid waste and these wastes are stored in two facilities. The high active liquid wastes have a relatively high decay heat, and therefore there is a risk of releasing radioactive materials outside the facility due to leakage or boiling. In addition, since the location of TRP is near the Pacific coast and there is a risk of earthquakes and tsunamis. Thus, for the two facilities which treat the high active liquid waste, the High Active Liquid Waste Storage Facility (HAW) and the Tokai Vitrification Facility (TVF), we decided to enhance those safety features in line with the upgrade regulatory standards. The notable safety measures include ground reinforcement work and exhaust pipe reinforcement work to improve earthquake resistance, installation of tsunami debris protection fences as a tsunami countermeasure, installation of protective doors against tornado debris, setting of wildfire prevention line, and strengthened measures against internal fires and internal flooding events. These construction works began in July 2020 and were completed in five years, by March 2025. Those provide great improvement in the safety of TRP for future vitrification processing.