Monte Carlo dose reconstruction in case of a radiological accident: application to the accident in Chile in December 2005

Following a radiological accident caused by a gamma-graphy source in Chile in December 2005 involving one victim, I.R.S.N. was contacted to perform the dosimetric reconstruction of the accident using numerical simulation. Tools developed in the laboratory, associating anthropomorphic mathematic or voxel phantoms with the Monte Carlo calculation code m.c.n.p.x., were used in order to determine the dose distribution on the left buttock and absorbed doses to critical organs. The dosimetric mapping show that the absorbed at the skin surface is very high (1900 Gy) but drops rapidly at deep. At a depth of 5 cm, it is 20 Gy. Calculations performed with a mathematical phantom indicate that average doses to the critical organs are relatively low. Moreover, possible bone marrow sites for puncture are identified. Based on the dosimetric mapping, an excision measuring 5 cm in depth by 10 cm in diameter was performed on the left buttock of the victim. (authors)