FUKUSHIMA Lives on the Line

231chap.IVPatient Relief Activity Records [Essays and Research Publications]FUKUSHIMA: Lives on the Lineobservation, gamma radiation showed the most drastic change, i.e., peak value of 9.3 times as usual level occurred on March 16, and exponentially decreased to 1.5 times of usual level after five months. A nonlinear least squares regression to these data indicated short half-life of 3.6 days and long half-life of 181 days. The first apparently short half-life (later referred as HL) is attributed to the ex­istence of I-131 (HL : 8 days), while the second long HL may be contributions from nuclides of Cs-134 (HL : 2 years), Cs-137(HL : 30 years) and Sr-90 (HL : 28.1 years). Also, the atmospheric radon concentration at the other place became high because of a stop of ventilation. Atmospheric radon at other places and second cosmic rays did not show any distinct response.Third, several weeks after the accidents, a team of radiation dosimetry under the direct control of Dean, School of Medicine, Prof. Hitoshi Ohto, was established for the continuation of radiation survey in FMU.Material and Methods1. Radiation surveillance right after the magnitude 9.0 earthquakeAssociate Dean, School of Medicine, Professor H. Yaginuma supervised radiation surveillance groups of interested people mentioned above. An NaI(Tl) scintillation counter surveyed radiation in several places in Fukushima Medical University hospital, i.e, ICU, NICU and pediatric ward. In the early stage, Japanese Self-Defense Force officials conducted patients screening with Geiger counters at the entrance of hospital with the help of this surveillance team.2. Serial natural-radiation measurements from Septermber 2010NaI scintillation counterA3″×3″ NaI(Tl) scintillation detector (Teledyne S-1212-T, 7% resolution for Cs-137) was observing gamma radiation in air at the author's office since October 2010. Every four hour counting data was stored in a personal computer. The present report discusses only gross dose rate expressed as a unit of cps. The office room was on the fourth floor of the five storied concrete building built in 1988.Radon detectorPassive type detectors (Pylon, AB-5) had been measuring atmospheric radon concentration at three places, i.e., the author's office room, students' lab and the Radioisotope Center. Another active type radon detector (Durridge, RAD7) had been detecting atmospheric radon in the author's room. Both types of detector were acquiring every one-hour data and stored in memories and/or printed out to papers. All these detectors safely continued measurements in spite of the magnitude 9.0 earthquake.Second cosmic raysFor the observation of cosmic rays, a 1″×1″ NaI(Tl) scintillation detector (Harshaw 905-3, 7% resolution for Cs-137) had been counting radiation whose energy is over 3 MeV. These data were also stored in a personal computer.3. The team of radiation dosimetry under the direct control of Dean, School of MedicineThe team of radiation measurement under the direct control of Dean, School of Medicine, used mainly NaI(Tl) scintillation counter for hospital and campus surveillance, and again Geiger counters checked mats in entrance hall and shoes-soles of students after exercise of sports in the ground of the campus.Results1. Radiation surveillance right after the magnitude 9.0 earthquakeFrom the beginning stage of the power plant crisis, Associate Dean, School of Medicine, Professor H. Yaginuma emitted the information of radiation surveillance, acquired from his teams, to FMU staff. In particular, outdoor gamma radiation results were reported on a bulletin board up to the present. Maximum of the observed value was 11.9μSv/h at 11:30 on March 16, 2011. The outdoor gamma values are around 0.4 μSV/h nowadays.Ward surveys were not announced officially, however ward members were able to have no worries about indoor radiation.Patients screening services at the entrance of the hospital continued until March 25, 2011. People whose cps exceeded 10,000 cpm were required decontamination at the separate 'decontamination tent.' The maximum value found was 100, 000 cpm. All members of FMU appreciate the aid of the staff of Japanese Self-Defense Force officials.2. Serial natural-radiation measurements from September 2010Gamma radiation in airFigure 1 shows gamma radiations with the NaI(Tl) scintillation detector. Just when the magnitude 9.0 earthquake happened, there was no change for the counts. As indicated in the figure, radiation dose reading began to elevate about 18:00 on April 15 and reached the