JCO Tokai-mura criticality accident (September 30, 1999)               [2] Low-level Exposures
 

JCO emergency actions

    Criticality accident occurred at 10:35 a.m. of September 30, 1999. Because the gamma-ray monitors in the JCO site remained high level, residents (about 200 residents) were recommended to evacuate from the area within 350 m radius of the conversion facility at 3:00 p.m. The residents within 10 km were recommended to remain in their houses at 10:30. By draining of cooling water from the cooling jacket of the precipitation tank and injection of boric acid solution into precipitation tank made the reaction to the end. Persons involved in the recovery action and rescue task, other emergency personnel, JCO employees, residents, and their estimated exposure levels have been reported by S. Tanaka (2001). The cytogenetic survey was carried out for those persons who agreed to the informed consent. In addition, lymphocyte chromosomes were also studied in remote residents who showed severely suppressed lymphocyte counts in the hematological examinations carried out on October 2-4, 1999 for residents (M. S. Sasaki et al. 2001).

Refs:

Tanaka, S. (2001): Summary of the JCO criticality accident in Tokai-mura and dose assessment. J. Radiat. Res., 42(Suppl): S1-S9.

Sasaki, M. S., Hayata, I., Kamada, N., Kodama, Y. and Kodama, S. (2001): Chromosome aberration analysis in persons exposed to low-level radiation from the JCO criticality accident in Tokai-mura. J. Radiat. Res., 42(Suppl):S107-S116.

  

[II] Persons exposed to low-level radiation (collaborative study)

Collaborative study:
         Hayata, I. (National Institute of Radiological Science) *Chairman
         Sasaki, M. S. (RBC, Kyoto University)		 Kamada, N. (Hiroshima University)
Kodama, Y. (Radiation Effects Research Foundation, Hiroshima)
Kodama, S (Osaka Prefectural University) 		 Kanda, R. (National Institute of Radiological Science)
Furukawa, A. (National Institute of Radiological Science)
Minamihisamatsu, M. (National Institute of Radiological Science)
Reference:
Sasaki, MS, Hayata, I., Kamada, N., Kodama, Y. and Kodama, S.: Chromosome aberration analysis in persons exposed to low-level radiation from the JCO criticality accident in Tokai-mura.
J. Radiat. Res., 42 (suppl.):S107-S116.


(1) Summary of the exposure conditions and blood sampling of persons studied for chromosome aberration analysis.

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Study populations
Categories Exposure conditions No. of Doccumented Blood sampling
persons dose (mSv)1) Number Date
(A) Local residents (I) Remote residents diagnosed to have low lymphocyte counts 180 ND 7 1999.10.18
(B) Local residents (II) Residents exposed at the vicinity of the site (about 80 m) 7 6.7-16 7 1999.10.21 1999.10.22
(C) JCOemployees (I) JCO employees in the facility 49 0.6-48 18 1999.10.21 1999.10.22
(C) JCO employees (II)2) JCO employees in the facility 96 0.06-17 0
(D) JCO employees (III) Workers involved in water draining from the tank 18 3.8-48 8 1999.10.21 1999.10.22
(E) Emergency personnels Firemen engaged in the rescue of severely exposed persons 3 4.6-9.4 3 1999.10.21
1): Documented effective dose equivalent including the dose estimated based on the whole-body counting of the activated 24Na., personal monitors reading and/or
    behavior after the accident in combination of the estimated neutrons and gamma-rays in the environment.
2): Dose valuation made based only on the behavior survey and estimated radiation dose in the environment.
.

(2) Summary of chromosome aberration analysis in peripheral blood lymphocytes.

No. Subject Age 1)Dose No. of Chromosome aberrations 2)DR-1 3)DR-2 4)Estimated dose (mGy-Eq)
ID (yrs) (mSv) cells Dic Rc Ra aM F del S del No. No. (0/00) D DL DU
1 A1801 81 0 1,391 1 2 1 1 5 2 0 0 4 3 2.16 0 0 27.6
2 A1802 31 0 1,600 2 0 0 0 3 1 0 0 2 2 1.25 0 0 24.3
3 A1803 56 1.4 1,355 4 0 0 1 7 4 0 0 4 3 2.21 0 0 28.2
4 A1804 63 0 1,227 3 0 0 0 5 3 0 0 3 2 1.63 0 0 30.9
5 A1805 86 0 1,083 1 0 0 1 5 4 2 2 1 1 0.92 0 0 34.5
6 A1806 33 0 1,600 3 0 1 1 2 1 1 0 4 3 1.88 0 0 24.3
7 A1807 26 0 1,600 1 1 0 0 4 3 0 0 2 1 0.63 0 0 24.3
8 B2101 49 6.9 1,765 0 0 0 1 1 1 0 0 0 0 0 0 0 22.2
9 B2102 74 9.7 1,015 2 0 1 0 8 6 0 0 3 3 2.96 31.7 0 117.1
10 B2103 50 12.0 1,600 2 0 0 1 5 4 0 0 2 1 0.63 0 0 24.3
11 B2104 28 15.0 1,800 1 0 0 1 5 4 1 1 1 1 0.56 0 0 21.8
12 B2201 48 6.7 1,600 2 0 1 0 9 7 1 1 3 3 1.88 19.7 0 81.3
13 B2202 25 14.0 1,600 0 0 0 0 3 3 0 0 0 0 0 0 0 24.3
14 B2203 29 16.0 1,600 4 1 0 0 9 4 1 1 5 5 3.13 80.9 26.3 155.2
15 C2108 36 1.5 1,700 5 0 0 0 7 4 0 0 5 3 1.76 28.5 0 87.9
16 C2111 36 23.0 1,341 4 0 1 0 8 4 0 0 5 5 3.73 92.5 29.9 174.6
17 C2116 34 30.0 1,700 3 0 0 0 6 3 2 2 3 3 1.76 30.6 0 90.3
18 C2117 24 23.0 1,600 0 1 0 0 4 4 0 0 1 0 0 0 0 24.3
19 C2118 36 47.0 1,700 2 0 2 0 3 2 2 2 4 3 1.76 28.5 0 87.9
20 C2119 49 5.9 1,600 1 2 0 1 7 5 1 0 3 3 1.88 18.5 0 80.1
21 C2120 42 11.0 1,600 1 0 1 3 1 1 0 0 2 1 0.63 0 0 24.3
22 C2121 41 7.0 1,600 1 0 0 0 6 5 0 0 1 1 0.63 0 0 24.3
23 C2122 31 8.5 1,578 0 0 0 2 3 3 0 0 0 0 0 0 0 24.6
24 C2123 39 13.0 1,600 5 0 0 0 6 3 0 0 5 4 2.5 51.6 3.5 120.8
25 C2124 19 32.0 1,700 2 0 0 0 5 4 0 0 2 1 0.59 1.5 0 37.7
26 C2204 52 18.0 1,600 3 1 0 1 10 6 0 0 4 4 2.5 38.5 0 107.3
27 C2205 38 0.6 1,600 1 0 0 0 5 4 0 0 1 1 0.63 0 0 24.3
28 C2206 44 6.1 1,600 1 1 0 1 6 4 0 0 2 2 1.25 0 0 24.3
29 C2207 37 4.9 1,600 0 0 1 0 0 0 0 0 1 1 0.63 0 0 24.3
30 C2208 36 2.0 1,630 1 0 0 0 2 1 0 0 1 1 0.61 0 0 23.9
31 C2211 31 1.9 1,600 1 0 0 0 1 1 0 0 1 0 0 0 0 24.3
32 C2212 37 2.0 1,374 0 0 0 1 2 2 0 0 0 0 0 0 0 27.9
33 D2109 53 13.0 1,700 2 0 0 0 2 0 0 0 2 2 1.18 0 0 23.0
34 D2110 38 14.0 1,700 4 0 0 0 3 0 0 0 4 3 1.76 26.3 0 85.6
35 D2112 36 13.0 1,700 2 0 0 0 1 0 1 0 2 2 1.18 5.5 0 54.6
36 D2113 37 19.0 1,700 2 1 1 0 7 4 0 0 4 4 2.35 48.5 2.9 115.0
37 D2114 38 9.4 1,600 4 0 0 0 7 4 1 1 4 3 1.88 30.8 0 93.0
38 D2115 35 19.0 1,600 3 1 0 0 3 2 0 0 4 1 0.63 0 0 24.3
39 D2209 35 9.8 1,600 1 1 0 0 2 0 0 0 2 2 1.25 9.6 0 61.7
40 D2210 37 14.0 1,600 3 0 1 0 6 4 0 0 4 3 1.88 31.8 0 94.1
41 E2105 43 9.4 1,600 2 0 0 1 2 1 0 0 2 2 1.25 0 0 24.3
42 E2106 27 4.6 1,800 2 0 0 1 5 3 0 0 2 2 1.11 13.4 0 61.4
43 E2107 44 8.6 1,720 2 0 0 0 5 3 2 2 2 2 1.16 0 0 22.7
Total (and average) (41.0) (10.53) 67,879 84 12 11 18 196 124 15 12 107 87 (1.28) (13.7) (1.5) (54.3)
1) Documented dose (combined neutron and gamma-ray doses).
2) Number of dicentrics and rings.
3) Number of dicentrics and rings with associated acentric frequencies in number per 1,000 cells..
4) Chromosomally estimated dose (D) with lower (DL) and upper (DU) bounds, in mGy equivalent chromosomal.
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Dose assessment by dicentrics and rings (DR-2): Dose in 60-Co gamma-ray equivalent 


(Y-C)=(2.31±0.88)×10-2D+(6.33±0.25)×10-2D2,
          in which D is dose in Gy
          C is age-dependent frequency in unexposed general populations as expressed by C=(2.92±0.52)×10-5/year.

          The age dependency was adopted from Tonomura et al. (1983).

Figure 1 (right panel) compares the dose estimated by chromosome aberrations (D2) and documented those (D1).
              The difference beween two doses could be due to the difference in neutron weighting factor for chromosome
              aberration formation and that of radiation protection quantity.