Fukushima Daiichi NPS Prompt Report 2013

This is follow-up information regarding the water leak from the underground reservoirs at Fukushima Daiichi NPS.

In response to the leakage from the underground reservoirs, the water stored in the underground reservoir No.1 is planned to be transferred to the filtrate water tank No.1.

Currently, the filtrate water tank No.1 and No.2 are connected with the buffer tank used for reactor water injection for emergency use. In order to prepare for the water transfer, the filtrate water tank No.1 will be detached from the transfer line between the buffer tank and the filtrate water tanks tomorrow (April 19).

The amount of time necessary for the work is estimated to be about 6 hours. Since water supply from the filtrate water tank (emergency water supply for the reactor water injection system) will be disabled during the work which will not fulfill the operational requirement stipulated by Article 139 of the technical specification^*, Article 136, Section 1 (intentional transition out of the scope of operational requirement for maintenance work) will be applied.

Though filtrate water supply from the filtrate water tank will be disabled during the work, there will be no impact on the reactor water injection as the freshwater treated by the water treatment facility is planned to be supplied to the buffer tank. Since there are raw water tanks in addition to the filtrate water tanks prepared for emergency use, it is confirmed that the amount of water required for the buffer tank is available.

*Article 139 of the technical specification requires that "the amount of stored water equivalent to the capacity of a filtrate water tank (916m³ or more) must be secured". Since the water supply from the filtrate water tank will be disabled during the work, the condition will not fulfill the operational requirement.