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Fukushima Daiichi - Drop in Water Levels


On February 18, as parameters, such as primary containment vessel water levels and temperature, were being monitored, the Unit 1 primary containment vessel experienced a drop in water level.

As a result, other parameters were checked and it was found that some of the temperature gauges in the primary containment vessels for Unit 1 and Unit 3 have been showing decreasing trends since February 15 and February 17, respectively.

Therefore, we have been assessing related parameters since February 18, and today February 19 we determined that water levels in the Unit 1 and Unit 3 primary containment vessels are decreasing.

Furthermore, since no significant fluctuations have been seen with temperatures at the bottom of the primary containment vessels, containment vessel gas management system radiation (including noble gas monitors), monitoring post and dust monitors at site borders, or on-site dust monitors, we have determined that there is no off-site impact.

During inspections on February 13 following the earthquake, no abnormalities were found with reactor cooling water injection equipment parameters or during visual inspections, and we confirmed that cooling water is being injected into reactors in a suitable manner.

It is possible that the cause of the drops in primary containment vessel water levels may be the result of changes to damaged portions of the primary containment vessel caused by the earthquake, so we will continue to watch and monitor parameters.

Furthermore, at current time no significant fluctuations have been seen in reactor buildingwater levels, but we are conducting a detailed assessment of, and monitoring, parameters.

Topics: NPP Fukushima Daiichi, Japan

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