The radir package for R was written to provide a tool for radiation dose estimation, based on chromosome aberration and calibration curve data. The tool takes a Bayesian approach, providing the results in the form of a posterior 'Calibrative Density' of dose, and thus probabilities - for instance for likelihood of dose < 1 Gy - can be easily extracted.
Publication
Morina D, Higueras M, Puig P, Ainsbury EA and Rothkamm K. radir package: An R implementation for cytogenetic biodosimetry dose estimation. J. Radiol. Prot., accepted 16/6/2015.