Despite the increasing popularity of hybrid electric vehicles (HEVs), few studies have compared the real-world particle emissions of HEVs from internal combustion engine (ICE) reignition events with that of a conventional vehicle (CV) during real-world driving. Reignition events occur under unstable combustion conditions and frequently result in particle number (PN) emission rates (PNERs) that exceed those for stabilized engine operation. Tailpipe PNERs from a CV and an HEV 2010 Toyota Camry were quantified on a 32-mi route over rural, urban, and freeway roadways in Chittenden County, Vermont, with the total onboard tailpipe emissions measurement system. This study directly compared the CV and HEV PNERs and characterized the operation of the HEV in a new HEV ICE operating mode framework. Mean PNER for reignition events (7.19 pM 11.8 × 1010 particles/s) were on average four times greater than for stabilized HEV operation (1.79 ± 3.99 × 1010 particles/s). Under urban, rural, and freeway driving, HEV reignition event operation accounted for 58.7%, 44.6%, and 5.0%, respectively, of the total PN inventory. Mean HEV PNER was 1.8 times greater than that of the CV in urban driving, while under freeway driving, where the two vehicles operated similarly, average CV PNER was 2.4 times greater than that of the HEV. The data show that the typical fuel consumption benefits of HEVs in urban driving are associated with a trade-off in PN emissions. The HEV ICE operating behavior has implications for the spatial distribution of PN hot spots as well as the associated microscale modeling of alternative vehicle technology emissions.
The Nuclear Materials Identification System (NMIS), developed by the Oak Ridge National Laboratory and Oak , has been successfully used at Y-12 for nuclear material control and accountability (NMC&A). It is particularly useful in the high gammaray background of storage arrays and for shielded HEU. With three systems in use at Y-12, NMIS has enhanced the NMC&A capability for verification and for confirmation of materials in storage and for HEU receipts by providing capability not available or practical by other NDA methods for safeguards. It has recently costeffectively quantified the HEU mass and enrichment of hundreds of HEU metal items to within a total spread of ± 5% (3 sigma) with and mean deviations for all HEU verified of + 0.2% for mass and -0.2% for enrichment. Three cart portable systems are easily moved around with minimal impact on facility operations since no permanent dedicated floor space is required. The positive impact of NMIS at the Oak Ridge Y-12 Plant is improved and more cost effective NMC&A as well as the resolution of NMC&A findings. Its operation at the Y-12 Plant is essential for compliance with the NMC&A requirements of the U. S. Department of Energy. NMIS portability has allowed one system to be moved temporarily to the former K-25 Gaseous Diffusion Plant for characterization of a large deposit of hydrated uranyl fluoride. The impact of this NMIS application was enhanced and verified nuclear criticality safety that led to the safe removal of a large deposit originally estimated by gamma-ray spectrometry and neutron counting to contain 1300 kg of 3.3 wt% 235 U material. NMIS has also been operational at Los Alamos National Laboratory and Pantex.
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