Chernobyl: Complex Task Group (Russia) Sevan'kaev et al. 1995

Scenario 

     In order to limit the release of radioactivity into environment and to prevent the disturbances by weather, the steel and concrete sheltering structure, called ‘sarcophagus’, was constructed to cover the struck reactor unit No. 4 of Chernobyl NPP. Several hundreds of persons worked in and around the ‘sarcophagus’. Aabout 15 engineers and scientists, so-called ‘Complex Task Group’, regularly entered the highly radioactive area in order to carry out number of tasks inside the ‘sarcophagus’. Lymphocytes chromosome aberrations were examine in 6 persons among those participated in the task group.

     They live and hold professional appointments in Moscow, where essentially no radioactive contamination, and periodically traveled to Chernobyl (Ukraine) to perform tasks. Generally they worked for 1-2 months at Chernobyl in every half-year. During this duty time, they live outside the 30-km exclusion zone and traveled daily to the reactor site.

     While working inside the ‘sarcophagus’ they have not officially monitored with their dose, but they were provided with quartz fiber electrometer (QFE) and the dose recorded by ‘do-it-yourself’ procedure. The QFE is worm in the pocket of their protective overalls. Above the overalls they wear plastic suits which were sufficient to prevent beta particles to reach to the body and QFE. They wear masks or respirators which prevent the inhalation of particlate matters. The QFE displays the dose in Roentgen (R), which was treated here as 1R=10mGy for the purpose of comparative effective assessment of chromosome aberrations.

     Much of the work was carried out below the base of the former reactor in which molted fuel had flowed. The fuel exists in three forms such as: (a) pellets of 2% enriched uranium dioxide plus some fission products (essentially unchanged fuel rods), (b) hot particles with various size of uranium dioxide which distributed throughout the ‘sacophagus’, and (c) lava-like flow of fuel which had mixed with sand. 

Reference 

     Sevan’kaev, A. V., Lloyd, D. C., Edwards, A. A. and Moiseenko, V. V. (1995): High exposures to radiation received by workers inside the Chernobyl sarcophagus. Riat. Prot. Dosimet., 59:85-91. 

Chromosome aberration analysis 
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Person Year of Previous dose Blood sampling QFE dose to blood No. of No. of Chomosome aberrations Time compensation Chromosomally estimated
birth (mGy) Sample No. Date sampling (Gy) cells Cu cells** Dic cR xAce factor*** dose (Gy)****
1 1958 60 1 6 Oct. 1992 9.2 200 74 54 22 12 1.46 13.1±1.8
2 12 Jan. 1993 10.4 80 31 20 7 14 1.46 12.2±2.7
3 13 May 1994 11.6 300 86 61 24 21 1.86 12.6±1.6
2 1947 50 1 30 Oct. 1992 10.3 200 47 33 10 11 1.53 8.4±1.5
2 4 Apr. 1994 17.1 300 51 43 8 10 1.67 8.0±1.2
3 1933 87 1 7 Jun. 1991 2.8 200 26 19 6 3 1.28 4.1±0.9
2 4 Sep. 1992 3.1 200 23 12 3 9 1.64 3.3±0.9
3 6 Oct. 1992 3.6* 300 57 36 16 17 1.50 6.0±1.0
4 3 Dec. 1993 3.6* 300 35 21 6 17 2.00 4.7±1.0
4 1955 unknown 1 13 May 1991 1.2 400 55 26 5 29 1.26 2.7±0.5
2 20 Sep. 1992 2.0 200 32 23 6 5 1.43 5.5±1.1
5 1956 0 1 7 Jun. 1991 1.5 120 11 3 1 7 1.25 1.0±0.6
6 1946 150 1 15 May 1991 0.9 200 3 2 0 2 1.38 0.5±0.4
*) Added dose should be greater than 0.5 Gy because of saturation of QFE (quartz fiber electrometer).
**) Cu cells: cells containing one or more of the types of aberrations listed.
***) Correction factor accounting of the loss of lymphocytes with time assumed to be with a half-life of 3 years.
****) The dose estimation was made using linar terms of dicentric yield of acute gmma and 250 kV X-rys in vitro experiments (i.e., 0.03 dicentric per Gy) and time compensation factors.
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