Measurement of neutron dose under criticality accident conditions at TRACY using TLDs

Applicability of a neutron dose equivalent monitor with thermoluminescence dosimeter (TLD monitor) as an area dosimeter for criticality accidents was studied through measurements at Transient Experiment Critical Facility (TRACY). The TLD monitor is composed of two TLD badges and a cubical polyethylene case, and has a response similar to the values of the conversion coefficients for the ambient dose equivalent in the energy range from 0.1 to 10 MeV. TRACY was operated with and without a water reflector when irradiating the TLD monitors. The neutron doses measured with the TLD monitors were converted into tissue kerma using dose conversion factors calculated with MCNP5. Factors to correct for the difference between responses of the TLD monitor to the spontaneous fission spectrum of a 252Cf calibration source and to spectra of TRACY were also calculated with MCNP5 and applied to the tissue kerma. The values of tissue kerma were proportional to the integrated power of TRACY. The measured tissue kerma ranged from 0.034 to 16 Gy, which covers the range from 0.1 to 10 Gy specified as important in criticality accident dosimetry by the IAEA. The presented method of measurement also satisfies the time limit on dose determination. (author)