At Fukushima Daiichi Nuclear Power Station, we are working on the 
stabilization of the reactor of Unit 1 by continuing the nitrogen gas 
injection to the reactor containment vessel and adjusting the water 
injection rate to the reactor monitoring several parameters.
In order to solidify these efforts, we need to install and calibrate a new
reactor water level gauge. Also, we need to install a circulating cooling 
system to improve the status of the reactor to a more stable cooled 
condition. To do so, we have to improve the working environment inside the
reactor building.

At this moment, in preparation for the improvement, we are conducting the 
visual inspection and measuring the radiation dose and the density of 
radioactive substances by a remote controlled robot inside the reactor 
building. From now on, we will install an ambient air filtration system*, 
circulate air inside the reactor building for a while, filter the 
radioactive substances and lower the density. After that, in order for 
workers to enter the reactor building and conduct necessary works, we will
open the airlock. Before opening the airlock, we will monitor the density 
of the radioactive substances within the reactor building and confirm that
the influence to the outside is low enough.
We will announce beforehand in opening the airlock of the reactor 
building. At the same time, we will closely monitor figures at monitoring 
posts and announce these.
                                                    (Previously announced)
On May 2nd, we received the instruction from the Minister of Economy, 
Trade and Industry to report the work detail of the Improvement of the 
working environment inside the reactor building of Unit 1, Fukushima 
Daiichi Nuclear Power Station, as well as the evaluation of the impact 
outside due to radioactive materials. 
On May 3rd, we organized the information based on this instruction, and 
reported to the Minister of Economy, Trade and Industry. The detail of the
report is as attached.

Attachment
 - Improvement of the environment within the Reactor Building of Unit 1 
                                                               (PDF 342KB) 

* Ambient air filtration system
This system vacuums up the ambient air at the work area by a fan, filters 
impurities and cleans the air.