In-phantom measurement of H(E) for neutron protection dosimetry

An accurate estimate of the primary limiting quantity, H{dollar}rmsb{lcub}E{rcub},{dollar} in radiation protection is required in lieu of the new ICRP-60 recommendations especially for neutrons. In this regard, a 3-D In-Phantom Dosimetry System aimed to give accurate estimates of H{dollar}rmsb{lcub}E{rcub}{dollar} was designed and constructed. The 3-D In-Phantom Dosimetry System consists of a 40 cm x 40 cm x 15 cm polymethylmethacrylate (PMMA) phantom (water-filled or solid), the Freon-12-based Superheated Liquid Drop Detectors (SLDDs), and a data acquisition system. The design of the PMMA phantom was based on the ICRP-60's list of significant organs and the ANSI N.13.11 recommended dimension for the slab phantom used in the calibration of neutron personnel dosimeters. The assignment of the organ location was based on the MIRD-5 mathematical model of man. The Freon-12 based SLDDs were manufactured and tested in the laboratory.; The 3-D In-Phantom Dosimetry System was experimentally tested using the bare and D{dollar}sb2{dollar}O-moderated {dollar}sp{lcub}252{rcub}{dollar}Cf sources at the Georgia Tech Neely Nuclear Research Center. The experimental procedure involved a preliminary in-air calibration and the main phantom measurements. Monte Carlo simulations using MCNP4A were conducted to calculate H{dollar}rmsb{lcub}E{rcub}{dollar} using the PMMA slab phantom and the renormalized ICRP-60 tissue weighting factors. H{dollar}rmsb{lcub}E{rcub}{dollar} values based on the MCNP calculations using the PMMA phantom are 14-17% lower when compared to Morstin et al.'s H{dollar}rmsb{lcub}E{rcub}{dollar} calculations based on an anthropomorphic phantom and using the ICRP-60 tissue weighting factors.; Results show that both experimental and calculational estimates of H{dollar}rmsb{lcub}E{rcub}{dollar} based on the ICRP-60 tissue weighting factors agree to within {dollar}pm{dollar}35% with an associated systematic error of 30%, for both the unmoderated and D{dollar}sb2{dollar}O-moderated {dollar}sp{lcub}252{rcub}{dollar}Cf sources and using 4 irradiation geometries. These results are well within the {dollar}pm{dollar}50% allowable uncertainty described in ANSI N.13.11. Thus, this study proves that the 3-D In-Phantom Dosimetry System can successfully estimate H{dollar}rmsb{lcub}E{rcub}{dollar} to within a {dollar}pm{dollar}35% accuracy. With these results and some refinements, this 3-D dosimetry system can potentially be used to calibrate personnel dosimeters directly to the estimated H{dollar}rmsb{lcub}E{rcub}.{dollar}...