The Pacific Northwest National Laboratory (PNNL) participated in a criticality accident dosimetry intercomparison exercise held at the Nevada National Security Site (NNSS) May 24-27, 2016. The exercise was administered by Lawrence Livermore National Laboratory (LLNL) and utilized the Godiva-IV critical assembly housed in the Device Assembly Facility (DAF) situated on the NNSS site. The exercise allowed participants to test the ability of their nuclear accident dosimeters to meet the performance criteria in ANSI/HPS N13.3-2013, Dosimetry for Criticality Accidents and to obtain new measurement data for use in revising dose calculation methods where appropriate. PNNL participated with new prototype Personal Nuclear Accident Dosimeter (PNAD) and Fixed Nuclear Accident Dosimeter (FNAD) designs as well as the existing historical PNAD design. The results indicated that the effective cross sections and/or dose conversion factors used historically for calculation of neutron dose from activation foils in PNADs and FNADs needed to be updated to effectively measure the operational quantities recommended for nuclear accident dosimetry in ANSI/HPS N13.3-2013 and to ensure that performance meets the performance criteria given in the standard. The measurement results obtained during the exercise are used in this report to establish a new dose calculation methodology to be used with PNNL’s new PNAD and FNAD designs. The report describes the methods used to derive new cross sections, dose conversion factors and a new dose calculation algorithm. The report also describes the algorithnm used to calculate gamma and neutron dose from OSL and OSLN elements in the PNAD and FNADs. The report demonstrates that the new methodology provides accurate dose results that meet the performance criteria in ANSI/HPS N13.3-2013 when applied to the dosimeters exposed during the exercise.
Revised: November 6, 2017 |
Published: October 31, 2017