Improving personnel neutron dosimetry at the INEL

The personnel neutron dosimeter used at the Idaho National Engineering Laboratory (INEL) was modelled after the Hankins style albedo dosimeter and uses six thermoluminescence dosimeter (TLD) chips encased in a cadmium box. Personnel neutron dosimeters are assembled, disassembled and analyzed manually and the neutron dose equivalent is determined by dividing the difference of the average signals from the irradiated6LiF chips and the irradiated 7LiF chips by a calibration factor. The neutron dose equivalent result is adjusted to account for differences between the field neutron energy spectrum and the calibration neutron energy spectrum using a Field Neutron Correction Factor (FNCF). The FNCF's have been determined for approximately 15 locations at the INEL by applying the ratio of responses from 9 inch and 3 inch spheres to the calibration curve determined by Hankins. The application of small FNCF's has resulted in a significant number of false positive neutron dose equivalent results. The Radiological Sciences Branch intends to perform a variety of neutron dose and energy spectral measurements at the previously identified locations to improve the assessment of personnel neutron dose equivalent. Using the results of those measurements, (1) new FNCF's will be developed, (2) a practical field technique will be developed to verify the FNCF's and to identify new areas of concern and (3) the lower limit of detection for neutron dose equivalent will be determined as a function of the neutron energy spectrum