Fukushima Daiichi NPS 1/2 exhaust stack drain sump pit water level decline
Nov 28, 2019
Tokyo Electric Power Company Holdings, Inc.
Fukushima Daiichi Decontamination & Decommissioning Engineering Company
Regarding Unit 1/2 exhaust stuck drain sump pit (hereinafter referred to as “the pit”*), its water level was found, on November 26, to have the tendency to drop to a certain level (approximately 325 mm), even when no water was transferred. Through the retroactive check of water level data, it was also found, on November 27, that there has been a downward trend in water level since the hit by Typhoon No. 19 on October 12.
At this moment, there are no significant fluctuations in the radioactive concentration of the on-site drainage channel monitor, seawater radiation monitor, and surrounding sub-drain pits, and no impact on the external environment has been confirmed.
* The pit has been installed to collect rainwater that enters the Unit 1/2 exhaust stack, and when the water level exceeds 400 mm, the pump is designed to automatically transfer the water to decrease the water level to 330 mm each time.
[Reference] Latest radioactivity analysis results of the pit water (March 5)
・ Cesium-134: 1.5 million Bq / L
・ Cesium-137: 20 million Bq / L
・ Gross beta: 28 million Bq / L