On May 11, 2011, a worker, who was working on blockage of a vertical shaft
near the water intake of Unit 3, found water flowing into a pit (a vertical
shaft made of concrete) through the duct where electric wires were installed.
As a result of our investigation of the potential leakage of radioactive
water off the site, the outflow of the water from the pit to sea was
confirmed on May 11.
Thereafter we inserted fabrics to the duct leading to the pit and filled
concrete inside the pit. We confirmed that the outflow was stopped on May 11.
(Previously announced on May 11, 2011)
On May 11 we received following verbal instructions from Nuclear and
Industrial Safety Agency (NISA) of Ministry of Economy, Trade and Industry;
• to check whether there is any impact on the ocean,
• to take measures immediately to stop the leakage, and
• to identify the inflow/outflow routes and their condition urgently and
report them.
Then we compiled preventive measures and countermeasures to prevent the water
from spreading to the outside of port, in addition to the condition of
inflow/outflow routes and the impact on the ocean as instructed. On May 20,
we reported them to NISA.
(Previously announced on May 21, 2011)
On May 23, we received an instruction document from NISA "Regarding the
countermeasure against water outflow including radioactive materials to the
outside from Unit 3 of Fukushima Daiichi Nuclear Power Station (instruction)."
(Previously announced on May 24, 2011)
Based on the instruction document, we investigated conditions of vertical
shafts and shore protections that we had not finished confirming and made
plans for countermeasures to prevent outflows. On June 1 we put them together
and reported to NISA.
Appendix: Plan to prevent water leakage containing highly concentrated
radioactive materials to outside environment in Fukushima Daiichi
nuclear power plant (summary)
* Regarding the countermeasure against water outflow including radioactive
materials to the outside from Unit 3 of Fukushima Daiichi Nuclear Power
Station (instruction)
[May 23rd, 2011 NISA No.2]
On May 20th, 2011, NISA received a countermeasure report from TEPCO against
water including radioactive materials (hereafter called "contaminated water")
to the outside from around the intake canal of Unit3 of Fukushima Daiichi
Nuclear Power Station.
On the report, as countermeasures to prevention of recurrence, obstructing
the shaft, installing some sandbags inside the intake canal, implementing
circulating purification system, etc. will be implemented.
Nuclear and Industrial Safety Agency (hereafter called "NISA"), in addition
to countermeasures TEPCO reported, would like TEPCO to implement following
actions by each due date in order to enhance countermeasures against
prevention of recurrence of contaminated water outflow at the site.
1. On TEPCO's report, although 27 points of vertical shafts, which lead to
seawater piping trench will be obstructed using concrete etc by the end
of June, 2011, we would like TEPCO to investigate the status of vertical
shafts and seawalls (cracks of quay etc.), which has not been confirmed
the status yet. For such points that TEPCO cannot deny the possibility
of water outflow, TEPCO should take countermeasures to prevent water
outflows and report to NISA by June 1st, 2011.
2. On TEPCO's report, continuous monitoring of seawater inside/outside of
port at the site and enhancing monitoring system as same as Unit 2 for
analyzing seawater inside of the silt fences at Unit 1, Unit 3 and Unit 4
will be implemented. However, we would like TEPCO, in addition to the
above mentioned measures, if TEPCO confirms significant increase in
density of radioactive materials based on the result of monitoring inside
the port, TEPCO should immediately conduct visual investigation etc
around the port and if some water outflows are confirmed, TEPCO should
implement proper measures to stop the water outflows. Also, the results
must be reported to NISA.
3. Accumulated contaminated water should be property reduced and to decrease
the possibility of occurrence of water outflow, TEPCO should conduct
investigation to a maximum extent regarding the status of accumulated
water inside the facility. The storage and disposal plan for
contaminated water must be reported to NISA by June 1st, 2011.
Appendix: Plan to prevent water leakage containing highly concentrated
radioactive materials to outside environment in Fukushima Daiichi
nuclear power plant (summary)(PDF 21.2KB)
Reference: Plan to prevent water leakage containing highly concentrated
radioactive materials to outside environment in Fukushima Daiichi
nuclear power plant (Reference)(PDF 318KB)
* Plan to prevent water leakage containing highly concentrated radioactive
materials to outside environment in Fukushima Daiichi nuclear power plant
(PDF 972KB)
