On August 9, the Tokyo Electric Power Company(Tepco) revealed thata “water leak was detected in unit 2” of the Fukushima Daiichi nuclear power plant. This incident involved the loss of about 25 tons of water, coming from both the spent fuel cooling system pump room and the heat exchanger room.
Controlled leak at Fukushima Daiichi nuclear power plant
According to official reports, at 1:05 p.m. that same day, a Tepco employee observed a reduction in the water level in the unit 2 spent fuel pool skimmer compensation tank. This tank functions to verify that the spent fuel pool is adequately filled. To determine the cause of the water level decrease, at 16:36 hours the main pump of the pool cooling system was deliberately turned off.
Tepco assessed that “shutting down the cooling system” would cause the water temperature in the Unit 2 spent fuel pool to initially increase by approximately 0.06 °C per hour, reaching an estimated maximum temperature of 46 °C. This temperature would remain below the 65 °C operating limit set for the pool.
The leaking water was directed to a floor drain, and at the same time, a collection well located in a room on the second floor of the basement was connected. At 6:52 a.m. on August 10, Tepco confirmed that the standing water level in the room had stopped rising, indicating that the leak had stopped. In addition, it was verified that the leaking water had not exceeded the level of the secondary drains near the building, remaining contained within the reactor.
Tepco announced on August 13 that it would continue to monitor the water level and temperature in the unit 2 spent fuel pool(SFP). The company will remain vigilant to activate circulation cooling if necessary while further investigations are conducted and additional measures are developed. In its statement, Tepco also indicated that it plans to use a remotely operated robot (SPOT) to investigate the field dose and examine the leaked water. Depending on the findings, future corrective actions will be deliberated.
The Director General of the International Atomic Energy Agency (IAEA), Rafael Mariano Grossi, reported on August 15 that Tepco had notified the IAEA about the leak. Grossi further mentioned that the incident was not related to the discharge of treated water from ALPS and assured that the IAEA had not detected any violation of radiation protection standards. The IAEA undertook to keep member states informed of any relevant developments.
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Photo: Tepco
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