(2) External Exposure Due to Natural Radiation Tokai. Tozan {National
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(2) External Exposure due to Natural Radiation Tokai. Tozan {National Institute of Radiological Sciences) A field sunny of exposure rates due to natural meter were used in 22 sites and their readings were radiation has teen conducted throughout the Tokji. compered for drawing a relationship between them. Tozan district of Japen during both September end Practically the direct reeding of the surveymeter October 1974. were reduced into the corresponding velue of the plastic The situation of the Tohei. Tozen district in chamber through the relationship of linear proportion. Japan is shown in Figure 3. Distribution of observed Systematic error at calibration (60Co) and reeding locations in the district is indicated in Figure 4. In error (radon) nf the plastic chamber were within each location, measurements of exposures it one to + EX (maximum over all error) and within ± 3.5% fifteen sites, one of where contained 5 rations et (standard error for 6p fl/hr) respectively. Reeding least, were mode. A total of 154 answers meesured. error of the surveymeter is ebout ± 3% (standard Observations were made using a sphericel error for B/iR/hr). ionization chamber and several scintillation survey- Measurements in open bare field were made at meters. The spherical plastic ionization chamber of one meter above the ground end outdoor gamma- which Hiner diameter and wall thickness are 200 mm rays exposure rates(uR/hr) were due to cosmic rays end 3 mm (acrylate) respectively has adequate sensitivi as well as terrestrial radiation, as it may be considered ty for field survey. The chamber was used es e standard that the contribution of fehbut due to artificial origin of apparatus, but it ft difficult to use the apparatus in was very small. ell locations only by the apparatus, so that a survey- Gammo-ray exposure rates due to natural meter with e Nel(TI) 1"0 x 1" scintillator was used for radiations in each location are shown in Table 3, end regular measurements. Two types of surveymetirs, the population exposure due to natural radiations in one with a 2"<P x 2" Nal(TI) scintillator and the other each prefecture of the Tokai. Tozan district is shown in with e 3"<p x 3" Nal(TI) scintillator, were used es Table 4. auxiliary devices. Both the chamber end the survey- Taiie 3. Gamma-ray Exposure Rates due to Natural Radiations in each Location of the Tokai-Tozan District - - October 1974 by S. Abe, K. Fuj'rtaka end K. Fujimoto (National Institute of Radiological Sciences) Exposure Rate Number of Sites Humbeir of Stations Prefecture Location * Apparatus ** OiR/hr) In each Location in aach Location YAMANASHI 1 OUuki 6.4 1 9 A,B,C 2 Enzun 9.1 1 5 B.C 3 Yamutuhi 8.4 1 5 B,C 4 Koto 6.8 2 10 A.B.C 5 Nirasaki 6.4 1 5 B,C (7) ExposunKat* Numbar of Sites Nttmbar of Stations Apparatus** tftfVhr) in cadi Location 6 Kamikuiahfki B,C 7 Fujiyoatuda B,C 8 Tiuro B,C NAGANO 9 liyama B,C 10 Nakano B.C 11 Suuka B,C 12 Nagano 10.1 A,B,C 13 Otari 10.3 B.C 14 Koahoku B,C 15 Oraachi B,C 16 Ueda B,C A.B.C 18 Kaniizawa B,C 19 Saku 6.2 20 Wada 8.0 B,C 21 Matsumoto 11.4 A,B,C 22 Shiojirl 10.0 B.C 23 Chino 10.1 B,C 24 Suwa 7.9 25 Okaya 10.6 26 Muiamimafci 7.3 B,C 27 Ina 10.1 B,C 26 Kifofukuahima 12.4 A.B.C 29 Komtgmt 9.2 B.C 30 Uda 10.3 A.B.C -IFU 31 Kamftakara 13.5 B.C 32 Takayama 13.0 A.B.C 33 ShoJuwa 13.0 B.C 34 Osaka 13.7 B.C 35 Shiratori 12.1 B.C 36 Gero 14.0 37 Hachlman 11.1 B.C 38 Nakatiugawa 16.3 B.C 39 Ena 13.6 B.C 40 Mizunamt 14.8 B.C (8) Exposure Rat* Number of Sitet Number of Stations Prafactun Location* (JOt/hr) in *aen Location in *acn Location 41 Toki US 1 5 42 Tajimi 11.6 1 6 43 Minokamo 12.6 1 5 44 Mtao 11.9 1 5 45 Seki 12.B 1 5 B.C 46 Kagamiian 10.3 1 5 B.C 47 Gifu 10.6 4 20 A.P.C 48 Haahtoa 12.2 1 5 B.C 49 Ogaki . 10.5 3 17 B,C SHIZUOKA 30 Gotanba 5.2 1 5 B,C 51 Fujinomiya 6.1 1 5 B.C 52 Nakakawane 11.6 1 S B.C 53 Haruno 11.1 1 5 A.B.C 54 Tentyu 10.4 1 5 B,C 55 Kocai 9.5 1 5 B.C 56 Hamamatni 9.7 4 20 A.B.C 57 Hamakita 10.0 1 5 B,C 58 Iwata 9.9 1 5 B,C 59 Fukuroi 9.5 1 5 B.C 6D Kakegawa 9.6 1 5 61 Hamaoka 9.3 I 4 62 Omae*akl 9.7 1 6 63 Sagara 10.2 1 5 64 Sbimada 10.2 1 5 65 Fujieda 10.2 1 5 B,C 66 Yaizu 10.8 1 5 B.C 67 Shlzuoka 9.7 4 21 B.C 68 Sbimizu 8.8 3 IS B.C 69 Fuji 7.8 1 4 B.C 70 Humazu 5.7 2 10 A.B.C 71 Toi 7.4 1 5 B.C 72 Shirnoda 6.6 1 6 A.B.C 73 Ito 5.4 1 6 B.C 74 Atami 5.7 1 6 B.C 75 Miihima 5.3 1 5 AICHt 76 Inabu 9.8 1 5 B.C 77 Seto 13.1 1 5 B.C 78 [nuyama 11.1 1 5 B.C 79 Konan 12.6 1 5 80 Ichfnomlya 12.1 3 15 (9) Expontn Rate Number of Site* Number of Stations Prefecture Location* Apparatus** UtfUhr) in each Location in each Location 81 Bitai 12.9 5 B,C 82 KomaH 12.1 5 B,C 83 Iwakura 11.8 5 B.C 84 Inasaw* 11.8 5 B,C 65 Tsushima 12,0 5 B,C 86 Nagoya 10.0 24 123 A.B.C 87 Kasugal 12.7 2 12 A.B.C 88 Toyou 12.0 2 10 A.B.C 89 Toyoake 9.5 5 B,C 90 Tokal 11.3 5 B,C 91 Cbityo 10.6 5 B,C 92 Kariya 10.4 5 B.C 93 Obu 10.0 5 B.C 94 Chit* 10.7 5 B.C 95 Tokoname 10.0 5 A,B,C 96 Handa 9.0 5 B,C 97 Takahama 10.2 5 B.C 98 Hekinan 10.7 5 B.C 99 Anjo U.4 5 B.C 100 Okazaki 10.9 15 A.B.C 101 Nubia 10.9 5 B,C 102 Gamagori 10.0 5 B.C LOS Toyohaahi 9.2 15 A.B.C 104 ToyoJcawa 10.5 6 B,C 105 Shinshiro 6.9 5 B,C * C.F. Fig. 4 ** A = Spherical Ionization Chamber B = Surveymeterwith2%t2WHaI(TC| Scintillator C = Sutveymeter with l'Vul'toalfrft Scintillator (10) Trtlt 4. FtpilMiM ExitmriaMto Natural Radiations in Eaxk Frafactan) of thl Tokri-Tozi* District ky S. Aki, K. Fujrtaka and K. Fujimoto fNetionel Institute offtediotogicet Sciences! Exposure Rate ± Standard Deviation Population * Number of (iiR/hr) (X100O) Sites YAMANASHI 7.3 ± 1.4 783 9 NAGANO 9.4 ± 2.0 2,018 25 GIFU 12.2 ± 1.6 1,868 24 SHIZUOKA 8.8 ± 1.9 3,309 35 AICHI 10.6 ± 1.4 5,923 61 TOKAI • TOZAN 13,901 1975 National Census (11) Figure3. ThtSitmtionofthtTOKAI-TOZAN District in Japin Prefecture 1. YAMANASHI 2 NAGANO 3 GIFU 4 SHIZUOKA 5 AICHI (12) Figurt 4. Distribution of Observtd Locations In the TOKAI-TOZAN District (cf. Tiblt 3) ,<? (13) .