Environmental Contamination and Decontamination After Fukushima Daiichi Accident
Abstract In this chapter, effectiveness of the environmental decontamination is discussed from the point of view of waste management. First, the relation between the environmental contamination and the radiation dose rate to the resident is summarized. Then, a model has been developed to understand effectiveness of artificial decontamination measures to achieve the goals set by the Japanese law. The analysis revealed the importance of waste volume reduction by strategic selection of areas for decontamination and development of volume reduction technologies. Decontamination can effectively contribute to reduction of the air dose rate if it is applied in areas where natural dispersion is slow, and thus strategic prioritization of areas for decontamination is highly recommended. Because of high heterogeneity of the natural environment, an adaptive, staged approach with feedbacks from actual decontamination should be taken. Instead of constructive feedback loop, however, we observe a vicious cycle consisting of a lack of integrated scientific knowledge base about environmental contamination and deterioration in trust among stakeholders in society. To halt this vicious cycle, we need to establish a fundamental scientific basis, both natural and social, for enabling in-depth analysis about what has been the most crucial damage resulting from the accident and why that occurred, and how radiological risk can or should be compared with other risks in society.
Keywords Decontamination • Natural dispersion • Cost • Feedback from stakeholders
On September 11, 2012, 18 months after the Great East Japan Earthquake and tsunami hit Japan, I visited the towns of Kawamata, Namie, Okuma, and MinamiSoma in Fukushima Prefecture. It was a bright, sunny day.
Ever since the accident, I had been feeling that I must visit the scene of the accident and see for myself what had happened. At the same time, I did not want to create more work for those who bore the heavy responsibility of dealing with its aftermath. After some vacillation, I gingerly asked Dr. Shinichi Nakayama, a close friend of mine, if I could have an opportunity to observe the restricted areas. Before the accident, he had worked for many years at the Japan Atomic Energy Agency (JAEA) on basic research in the geochemistry of radionuclides. After the accident, JAEA established an offi in Fukushima to give scientifi advice on environmental decontamination to the Prefectural government and local communities. Dr. Nakayama was then the deputy head of this new offi He willingly agreed to my request, saying that he had already welcomed such visitors several times, including those from overseas, and arranged a 1-day tour for me with six other researchers from JAEA (Fig. 4.1). The inside of our car was fully covered with plastic sheeting to protect the vehicle from being contaminated by dirt tracked in on our shoes. Each of us had a pocket dosimeter.
Fig. 4.1 Researchers of JAEA Fukushima, who accompanied me during the 1-day tour, taken in front of Okuma Town Hall on September 11, 2012. Dr. Nakayama is second from left
Fig. 4.2 Plastic bags containing waste from decontamination, or josen, piled up in the schoolyard in the Town of Namie, Fukushima Prefecture; taken on September 11, 2012
I was nearly speechless during the day. The mountains, forests, fields, farms, school buildings, playgrounds and houses looked peaceful and intact, though unnaturally quiet (Fig. 4.2). Police cars often passed by, breaking the silence. They were patrolling empty houses to protect them from theft by intruders. Then, we stepped into the coastal area in the town of Okuma, which was inundated by the tsunami. Because the area was within a mile of the Fukushima Daiichi Nuclear Power Station and the radiation level was high, it had been left untouched since the accident. All that was displayed in front of my eyes was emptiness covered by dense summer grasses.
This view was completely different from what I had seen in Kobe in February 1995, a month after the Great Hanshin-Awaji Earthquake, when I went there to visit my late brother and his family. In Kobe I saw many heavily destroyed buildings and roads, and through my brother's work  as a psychiatrist, the difficulties and agony of survivors. But in Fukushima, it took me some time to comprehend those scenes of silence and disappearance, although they continued to gnaw on my mind long after. That night I had a late supper by myself after parting from the JAEA researchers, profoundly unsettled by the emptiness I had witnessed.
The full impact of the Fukushima nuclear disaster on Japanese society goes far beyond matters directly related to what happened within the nuclear power plant itself. From among dozens of critical issues that should be taken up, I have limited my focus in this chapter to decontamination of the environment and its consequences from the point of view of waste management.