contamination and similar challenges posed by the radioactive materials derived from the accident. For further details on the accident and its development, see June 2011 Report of the Japanese Government to the IAEA Ministerial Conference on Nuclear Safety covering the situation through May 31, 2011, and Additional Report of the Japanese Government to the IAEA – The Accident at TEPCO's Fukushima Nuclear Power Stations (Second Report), published September in of the same year, covering the situation through August 31, 2011.

In this section, the term “radioactive cesium” is used to refer to cesium 134 and cesium 137, which are radioactive materials involved in the accident.

## 1 Evacuation in Response to the NPS Accident and the Situation Immediately Following the Accident

In response to the loss of all AC power, the inability to inject water in the emergency core cooling system, and other dire concerns at the TEPCO Fukushima Daiichi NPS, then Prime Minister Naoto Kan declared a nuclear emergency at 19:03 on March 11 and established the Nuclear Emergency Response Headquarters in the Office of the Prime Minister. At the Fukushima Nuclear Emergency Response Headquarters, the Fukushima prefectural governor issued an evacuation order for Okuma-machi and Futaba-cho. The order was issued in response to the declaration of a nuclear emergency in Fukushima at the Fukushima Daiichi NPS at 20:50 of the same day, and urged residents of the two towns within a two-kilometer radius of Fukushima Daiichi NPS to evacuate.

At 21:23 on the same day, the Nuclear Emergency Response Headquarters (NERHQ) instructed the Fukushima prefectural governor and relevant local governments to call for the evacuation of residents living within a three-kilometer radius of the Fukushima Daiichi NPS and issued a "stay indoors" order for residents within a 10-kilometer radius.

Ministerial colleagues then reviewed the evacuation area. At 05:44 on the following day, March 12, the NERHQ and the Fukushima prefectural governor instructed local governments to call for an evacuation of residents within 10 kilometers of the Fukushima Daiichi NPS. In response to an explosion that occurred at 15:36 on the same day (March 12) at the Unit 1 nuclear reactor building, NERHQ instructed the Fukushima prefectural governor and local governments to call for an evacuation of residents within 20 kilometers at 18:25.

After a series of incidents, the NERHQ Director-General instructed the Fukushima prefectural governor and relevant local governments to issue a "stay indoors" order to residents within 20-30 kilometers of the Fukushima Daiichi NPS at 11:00 on March 15. The incidents leading up to this order included: an explosion at Unit 3 at 11:01 on March 14; an impulsive sound generated from the direction of Unit 4 around 06:00 on March 15; confirmation of damage in the vicinity of the fifth-floor roof of the Unit 4 nuclear reactor building around 08:11 that same day; and a fire outbreak in the northwest vicinity of the third floor of the same nuclear reactor building at 09:38 on the same day.

Furthermore, to further ensure the safety of residents within 20 kilometers of the TEPCO Fukushima Daiichi NPS, the NERHQ Director-General instructed the Fukushima prefectural governor and heads of local governments to designate the area as an alert zone on April 21.

Meanwhile, environmental monitoring data had revealed that there were areas where radioactive materials had accumulated at high levels even outside a 20-kilometer radius from the TEPCO Fukushima NPS. As a result, heads of local governments were instructed on April 22 to newly designate two specific areas: an area within a 20-kilometer radius, which was designated as an Emergency Planning Zone (EPZ); and an area between a 20-kilometer and 30-kilometer radius (which had been set as a "stay indoors" evacuation area, excluding the areas within it qualifying as deliberate evacuation areas), which was renamed as an Evacuation-Prepared Area in Case of Emergency, since the residents there could possibly be instructed to stay indoors or evacuate in case of future emergencies. In this way, residents inside the deliberate evacuation area were directed to evacuate in a systematic manner, and residents inside the area were prepared for evacuation in case of emergency, and directed to prepare for evacuation or in-house evacuation in case of an emergency. Among these evacuation directives, the Evacuation-Prepared Area in Case of Emergency was lifted on September 30, 2011.

Furthermore, since there were some areas with a predicted accumulated per-year exposure dose of 20 mSv or higher in the year following the accident—even outside the EPZ—the NERHQ on June 16 issued a policy to designate the areas in question as Specific Spots Recommended for Evacuation. The aim of this move was to call attention to the situation and provide support for and encourage residents to evacuate.

As these evacuation directives had a major impact on the livelihood of residents, on August 9, 2011, the NERHQ issued their perspective on reviewing the evaluation areas. Their approach was based on the idea that evacuation directives should be reviewed as soon as possible if there were major changes in the situation. Assessment of changes should be based on an understanding of reduced radiation dosages identified via safety checks of nuclear reactor installations and the accumulation of detailed monitoring results.

On December 16, the NERHQ concluded that comprehensive safety in the entire Fukushima Daiichi NPS had been secured and the Step 2 goal had been accomplished, which meant that the radiation leak was under control and the amount of radiation was kept extremely low, judging from the following circumstances: the reactors were reaching cold shutdown (CSD) conditions; the spent fuel pools were being kept in a stably cool condition; there was

a decreasing amount of stagnant water; and radiation leaks from reactors were being controlled. On March 30, 2012, as the Step 2 goal had been achieved, the NERHQ decided to

## 2 Monitoring for Radioactive Contamination

From the accident that occurred at TEPCO Fukushima Daiichi NPS, massive amounts of radioactive materials were discharged into the air, which lead to concern about their influence on the nation's health. To cope with this situation, a number of measures were considered regarding healthcare for small children and other citizens and decontamination to be done in future. Also, in order to provide well-organized information, a Monitoring Plan in the Area was mapped out at a monitoring coordination meeting held by the government in August 2011. In this plan, monitoring related to radioactive materials is clarified with respect to the division of roles to each governmental department, and each department conducts monitoring according to the plan. In addition, the results of the monitoring conducted by the related ministries and agencies are integrated, and are being provided on the radiation monitoring portal site.

(1) Environmental monitoring in general, airborne monitoring, marine areas, schools and public facilities.

Air dose rates were measured by each prefecture and an environment improvement sample analyzer was made, review the designation of evacuation zones and emergency evacuation preparation zones.

With regard to the ocean, the level of radioactive material was measured in ocean water, on the ocean floor, and

which is to be used to analyze radioactive materials contained in the soil and so on. Also, in the area surrounding TEPCO Fukushima Daiichi NPS, the air dose rate has been measured continuously using monitoring vehicles, transportable monitoring posts, and integrating dosimeters (glass badges) since March 2011. In emergency evacuation preparation zones, in order to support restoration, detailed monitoring, in addition to regular monitoring, was conducted, including surface monitoring, such as a vehicle-borne survey, or monitoring of well water and rivers, focused on living areas in response requests from local government, and a radiation distribution map was produced. In Alert zones and Emergency Planning Zones, detailed monitoring of the air dose rate, such as vehicle-borne surveys, was conducted. In addition, Tokyo and 21 prefectures in eastern Japan were monitored by aircraft; specifically, for the area within an 80-kilometer radius of TEPCO Fukushima NPS, the monitoring was conducted five times (one time of them conducted only in the Emergency Planning Zone and the Evacuation-Prepared Area in Case of Emergency) to detect the air dose rate and radiocesium level.

Figure 2-4-1 A Part of Survey by Aircrafts

Source: The result of 4 $ ^{th} $ survey by aircraft