Roadmaps for Bringing Nuclear Power Station Accident under Control Revised; Goal of Settlement in 6-9 Months Retained

May 20, 2011

Tokyo Electric Power Co. (TEPCO), operator of damaged Fukushima Daiichi Nuclear Power Station, announced on May 17 a revised version of the roadmap for bringing it under control. The revision was made after the operator's discussion with the Government. The revised roadmap retained the target of bringing the release of radioactive materials under control and radiation dose being significantly held down in the first six to nine months since the publication of original timetables a month ago.

Two Major Changes

The revised plan retains the goal of restoring the damaged nuclear reactors to a state of stable cooling within three months, and henceforth bringing them to a state of "cold shutdown" within three months hopefully and within six months at the latest -- as envisioned in the original plan announced on April 17. However, there are two major changes between the original and the revised roadmap. Following is an overview of the changes:

"Big Loop" Cooling System

One change is the method of cooling. "A few days ago, it came to light that the water level within the No.1 unit was lower than we had initially anticipated," said Mr. Goshi Hosono, Advisor to the Prime Minister, referring to the level of cooling water inside one of the stalled reactors. This came to light because workers were able to enter into the building the No.1 unit and curry out the calibration of the gauges. Judging from the temperature in the reactor's pressure vessel, which was not so high despite the low water level, the Government also, concluded that there was a meltdown of the reactor core or fuel rods.
It was initially planned to cool hot water inside the reactor by allowing it to travel through a heat exchanger and then return to the reactor. This method is "very attractive and easy to understand," but TEPCO and the Government decided not to stick to this method. What they are opting to do instead is a "big loop" in which leaked water inside a turbine building is led to another facility for decontamination and desalination and then returned to the reactor. The Government hopes this cooling system can be completed within June and, within three months since the issue of the original roadmap, that is, by July 17, it will have the system in place for the Nos. 1 to 3 reactors.

Better Working Environment Eyed

The other major change is an improvement in the working environment as clearly set out in the new roadmap. The Government has instructed TEPCO to ensure the proper health of workers and control the level of radiation they are exposed to. In this connection, it has decided to introduce two methods.
1. (i) One is that in case there is a possibility of workers being exposed to 1 millisievert of radiation or more per day, TEPCO will be required to notify the Government beforehand.
2. (ii) As for the health management for workers, the Government will set up a database so that it can trace the amount of radiation that workers were exposed to. Therefore, the Government will be responsible directly for managing the health of these workers in the long term.

Independent Team to Investigate Nuclear Accident

In the meanwhile, the Government of Japan has launched an investigation into the accident to report to the IAEA ministerial meeting slated for June 20. Mr. Hosono is responsible for this investigation and it will look into the response measures that have been taken. Japan will also conduct a comprehensive verification into what has happened, in parallel to this work for the IAEA meeting. This will be conducted by a third-party verification group independent of the Government, examining various responses including government's. In any case, be it at the IAEA meeting or on other international occasions, Japan is going to share the information obtained through these activities with the international community so as to make sure the country is open to the rest of the world.

For further details, please see the following TEPCO's and Government's documents:

【TEPCO documents】

【Government documents】

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