Passive TLD Based System for Characterisation of Spectral and Anglular Properties of High Dose Rate Workplace Fields

In order to address the problem of characterisation of high dose rate workplace fields, unique techniques and devices have been developed and tested. The kit of devices comprises a passive spectrometric system and six-vector collimator with thermoluminescent detectors (TLDs) inside, allowing determination of the anisotropy of the radiation field, both horizontal and vertical. The passive spectrometric system makes use of simultaneous exposure of several TLDs placed inside spherical attenuators. Deconvolution of gamma spectra is performed by solving a system of simultaneous linear equations. The problem of solving ill-defined systems of simultaneous equations was addressed by a system regulatisation method. The energy resolution of the system is not high (seven to ten energy bins can be distinguished), yet is sufficient for practical needs. After several benchmark tests, the discussed experimental set-up was extensively tested in various locations within Object 'Shelter'. Results of both energy spectrum and exposure geometry characterisation demonstrated the feasibility of the proposed approach.