SummaryThe Pacific Northwest National Laboratory (PNNL) has used two types of instruments, the tissue equivalent proportional counter (TEPC) and the multisphere spectrometer for characterizing neutron radiation fields in support of neutron dosimetry at the Hanford site. The US Department of Energy recently issued new requirements for radiation protection standards in 10 CFR 835 which affect the way that neutron dose equivalent rates are evaluated. In response to the new requirements, PNNL has upgraded the analyses used in conjunction with the TEPC and multisphere.The analysis software for the TEPC was modified for this effort, and a new analysis code was selected for the multisphere. These new analysis techniques were implemented and tested with measurement data that had been collected in previous measurements. In order to test the effectiveness of the changes, measurements were taken in PNNL's Low Scatter Room using 252 Cf sources in both unmoderated and D 2 O-moderated configurations that generate wellcharacterized neutron fields. The instruments were also used at Los Alamos National Laboratory (LANL), in their Neutron Free-in-Air calibration room, also using neutron sources that generate well-characterized neutron fields. The results of the software modifications and the measurements are documented in this report.The TEPC measurements performed at PNNL agreed well with accepted dose equivalent rates using the traditional analysis, agreeing with the accepted value to within 13% for both unmoderated and moderated 252 Cf sources. When the new analysis was applied to the TEPC measurement data, the results were high compared to the new accepted value. A similar pattern was seen for TEPC measurements at LANL. Using the traditional analysis method, results for all neutron sources showed good agreement with accepted values, nearly always less than 10%. For the new method of analysis, however, the TEPC responded with higher dose equivalent rates than accepted, by as much as 25%. The reason for the overresponse is that there is very little attenuation of the neutrons by tissue, so it cannot match the effect of attenuation by 1 cm of tissue called for in the new standards. This could be corrected with a modified instrument with a thicker wall, or by analytical means that would need to be developed.The multisphere spectrometer performed reasonably well both at PNNL and at LANL. It could produce a neutron spectrum that was similar to the accepted spectrum, and total flux values were usually within 15% of the accepted values. Dose equivalent rates were usually within 18% of the accepted values. The average energies, however, were usually lower than the accepted values. The performance of this instrument could be much better than seen in this study. If PNNL were to add some moderating spheres to its measurement set and calculate a new set of instrument response functions, performance could be improved. The multisphere could then be a more useful instrument for assessing the dose equivalent rate in the workplace.iii

This document was printed on recycled paper. SummaryThe Pacific Northwest National Laboratory (PNNL) conducted neutron measurements at Hanford's Plutonium Finishing Plant (PFP). The measurements were performed to evaluate the performance of the Hanford Standard Dosimeter (HSD) and the 8816 TLD component of the Hanford Combination Neutron Dosimeter (HCND) in the neutron fields responsible for worker neutron exposures.For this study, TEPC detectors and multisphere spectrometers were used to measure neutron dose equivalent rate, and multispheres were used to measure average neutron energy. Waterfilled phantoms holding Hanford dosimeters were positioned at each measurement location. The phantoms were positioned in the same location where a multisphere measurement was taken and TEPCs were also positioned there. Plant survey meters were also used to measure neutron dose rates at all locations.Three measurement locations were chose near the HC-9B glovebox in room 228A of Building 234-5.The multisphere spectrometers measured average neutron energies in the range of 337 to 555 keV at these locations. Personal dose equivalent, H p (10) n , as measured by the multisphere and TEPC, ranged from 2.7 to 9.7 mrem/h in the three locations. Effective dose assuming a rotational geometry (E ROT ) was substantially lower than H p (10), ranging from 1.3 to 3.6 mrem/h. These values were lower than the reported values from dosimeters exposed on a rotating phantom. Effective dose assuming an AP geometry (E AP ) was also substantially lower than H p (10), ranging from 2.3 to 6.5 mrem/h. These values were lower than the reported values from the dosimeters on slab phantoms. Since the effective dose values were lower than reported values from dosimeters, the dosimeters were shown to be conservative estimates of the protection quantities.iii

This document reports the results of testing of the Hanford Personnel Nuclear Accident Dosimeter (PNAD) during a criticality accident dosimeter intercomparison exercise at the CEA Valduc Center using the CALIBAN test reactor on September 20-23, 2010.KEY WORDS: personnel nuclear accident dosimeter; PNAD; CALIBAN test Reactor;intercomparison. PNNL Results from 2010 CALIBAN Criticality Accident Dosimeter Intercomparison Exercise