[en] The Advanced Test Reactor (ATR) is a research reactor at the Idaho National Laboratory is primarily designed and used to test materials to be used in other, larger-scale and prototype reactors. The reactor offers various specialized systems and allows certain experiments to be run at their own temperature and pressure. The ATR Canal temporarily stores completed experiments and used fuel. It also has facilities to conduct underwater operations such as experiment examination or removal. In reviewing the ATR safety basis, a number of concerns were identified involving the ATR canal. A brief study identified ergonomic issues involving the manual handling of fuel elements in the canal that may increase the probability of human error and possible unwanted acute physical outcomes to the operator. In response to this concern, that refined the previous HRA scoping analysis by determining the probability of the inadvertent exposure of a fuel element to the air during fuel movement and inspection was conducted. The HRA analysis employed the SPAR-H method and was supplemented by information gained from a detailed analysis of the fuel inspection and transfer tasks. This latter analysis included ergonomics, work cycles, task duration, and workload imposed by tool and workplace characteristics, personal protective clothing, and operational practices that have the potential to increase physical and mental workload. Part of this analysis consisted of NASA-TLX analyses, combined with operational sequence analysis, computational human performance analysis (CHPA), and 3D graphical modeling to determine task failures and precursors to such failures that have safety implications. Experience in applying multiple analysis techniques in support of HRA methods is discussed.

[en] The phase diagram of a single component Bose system in a lattice at zero temperature is obtained. We calculate the variational energies for the Mott insulating and superfluid phases. Below a certain critical density the Mott insulating phase is stable over the superfluid phase for low enough tunneling amplitude regardless of whether the number of bosons is or is not incommensurate with the lattice. The transition is discontinuous as the superfluid order parameter jumps from a finite value to zero at the Mott transition

[en] This paper introduces a novel augmentation to the current heuristic usability evaluation methodology. The SPAR-H human reliability analysis method was developed for categorizing human performance in nuclear power plants. Despite the specialized use of SPAR-H for safety critical scenarios, the method also holds promise for use in commercial off-the-shelf software usability evaluations. The SPAR-H method shares task analysis underpinnings with human-computer interaction, and it can be easily adapted to incorporate usability heuristics as performance shaping factors. By assigning probabilistic modifiers to heuristics, it is possible to arrive at the usability error probability (UEP). This UEP is not a literal probability of error but nonetheless provides a quantitative basis to heuristic evaluation. When combined with a consequence matrix for usability errors, this method affords ready prioritization of usability issues

[en] The level structure of ⁸⁹Nb has been investigated using the (¹⁹F, xnγ) reaction and gamma-ray spectrosocpy. The measurements were performed with the γ-γ coincidence technique using Ge(Li)-detectors. The direct feeding excitation functions of the quasirotational band levels and the angular distribution of gamma-rays have been measured in the ion energy range from 50 MeV to 70 MeV. New energy levels, their spins and parities are indicated. The data are explained on the basis of the shell model

[en] Electrons on helium form a unique two-dimensional system on the interface of liquid helium and vacuum. A small number of trapped electrons on helium exhibits strong interactions in the absence of disorder, and can be used as a qubit. Trapped electrons typically have orbital frequencies in the microwave regime and can therefore be integrated with circuit quantum electrodynamics (cQED), which studies light–matter interactions using microwave photons. Here, we experimentally realize a cQED platform with the orbitals of single electrons on helium. We deterministically trap one to four electrons in a dot integrated with a microwave resonator, allowing us to study the electrons’ response to microwaves. Furthermore, we find a single-electron-photon coupling strength of $g/2\mathrm{\pi <!--\; ??\; -->}=4.8\pm <!--\; ??\; -->0.3$ MHz, greatly exceeding the resonator linewidth $\mathrm{\kappa <!--\; ??\; -->}/2\mathrm{\pi <!--\; ??\; -->}=0.5$ MHz. These results pave the way towards microwave studies of Wigner molecules and coherent control of the orbital and spin state of a single electron on helium.

[en] Purpose: Asymmetric collimation is a relatively new method of junctioning abutting fields with non-diverging beam edges. When this technique is used at the junction of lateral and low anterior fields in three field head and neck set ups, there should, in theory, be a perfect match. There should be no overdose or underdose at the match line. We have performed dosimetric measurements to evaluate the actual dosimetry at the central axis. Materials and Methods: X-ray verification film was placed in a water-equivalent phantom at a depth of 4 cm, corresponding to an isocentric distance of 100 cm. A double exposure technique was used to mimic two half-beam blocked fields abutting at the central axis. Each half of the film was irradiated with 50 monitor units using a 6 MV photon beam. One of the collimators was set to an off-axis position to force a gap or overlap of the radiation fields at the isocenter in increments of 1 mm. The films were scanned with a laser densitometer with a resolution of 300 μm. The beam profiles were evaluated at the region of overdose or underdose around the match line. Results: The dose on the central axis varied linearly from - 50% (field gap of 3 mm) to + 50% (field overlap of 3 mm). Surprisingly, the width (defined as a full-width, half-maximum, FWHM) of the region of overdose or underdose around the match line is 3 mm for field gaps or overlaps of 1 and 2 mm. The width of the region is 4.5 mm for field gaps or overlaps of 3 mm. The larger than expected width of this region is due to the addition of the two abutting penumbras. Conclusion: Asymmetric collimation with half-beam blocks may overdose the spinal cord. Calibration specifications generally allow for a 1 mm tolerance in the position of each independent jaw. In a calibrated machine, this could lead to a 2 mm field overlap. A field overlap of just 1 mm results in a FWHM region of overdose measuring 3 mm with a maximum dose of 140%. To our knowledge, there are no current recommendations for the quality evaluation of independent jaws. We recommend 1) that a block ≥ 5 mm be placed over the spinal cord in one of the abutting fields to prevent spinal cord overdose, or 2) that independent jaws should be evaluated as part of a quality assurance program

[en] I use a stochastic production frontier to model energy efficiency trends in 85 countries over a 37-year period. Differences in energy efficiency across countries are modeled as a stochastic function of explanatory variables and I estimate the model using the cross-section of time-averaged data, so that no structure is imposed on technological change over time. Energy efficiency is measured using a new energy distance function approach. The country using the least energy per unit output, given its mix of outputs and inputs, defines the global production frontier. A country's relative energy efficiency is given by its distance from the frontier—the ratio of its actual energy use to the minimum required energy use, ceteris paribus. Energy efficiency is higher in countries with, inter alia, higher total factor productivity, undervalued currencies, and smaller fossil fuel reserves and it converges over time across countries. Globally, technological change was the most important factor counteracting the energy-use and carbon-emissions increasing effects of economic growth.

[en] Purpose: 1.) To describe the phenomenon of respiratory glottic motion, and evaluate its effect on dosimetry during small volume radiation therapy (XRT). 2.) To describe the new technique of video-cine fluoroscopy. Materials and Methods: Glottic motion was documented with serial static Eigen images in twelve (12) patients undergoing simulation for head and neck cancer XRT. Fluoroscopic imaging of glottic motion was recorded by video-cine in real-time. Snapshot images were obtained with the glottis in a neutral position, on maximum excursion during both normal and deep inspiration, and swallowing. A reference point on the laryngeal cartilage was identified, and displacement from the baseline measured with metric calipers. Computerized dosimetry was performed for 4, 5 and 6 cm² field sizes, and the effect of motion on dose distribution was calculated. Results: The glottis moves primarily in the cephalo-caudad plane during XRT in the supine position despite head immobilization. There is also a minor and dosimetrically insignificant antero-posterior component to glottic motion. Previously recognized cephalad motion during swallowing was noted to average 1.81cm (range 0.57-3.03cm, standard deviation 0.736). The glottis moved caudally during respiration: normal inspiration, average 0.42cm, (range 0.00-0.94cm, standard deviation 0.242), and deep inspiration, average 0.84cm, (range of 0.22-1.42cm, standard deviation 0.396). At the point of maximum excursion there was a calculated decrease in dose to the true vocal cord in the plane of the anterior commisure for swallowing as follows: approximately 95%, 90%, and no change, range 10-100%, for 4, 5 and 6 cm² field sizes respectively. For normal inspiration, there was no dose decrement for the average or extreme values. For deep inspiration, there was no dose decrement for the average values, but for the extremes, there was a decrement of 10%, 5%, and 3% for 4, 5 and 6 cm² field sizes, often within 1-2mm of very steep dose gradients. Video fluoroscopy measurements indicate that the glottis dwells in the depressed position up to approximately 50% of the respiratory cycle. The combined effects of treatment duration, respiratory glottic displacement and its duration lead, can lead to a dose decrease of 5% or more. Conclusions: Glottic displacement during breathing is less than during swallowing, but occurs more frequently. The edge effect of small field dosimetry becomes important, with no tolerance for set up variation. The effect can be minimized if patients are instructed to relax, and breathe shallowly, and if the immobilization mask covers the thyroid cartilage, if prominent. The assessment of glottic motion during fluoroscopic simulation and the patient's respiratory rate may be helpful in the selection of field size, and potentially decrease treatment failure in some patients with early glottic cancer

[en] This paper describes a cognitively based human reliability analysis (HRA) quantification technique for estimating the human error probabilities (HEPs) associated with operator and crew actions at nuclear power plants. The method described here, Standardized Plant Analysis Risk-Human Reliability Analysis (SPAR-H) method, was developed to aid in characterizing and quantifying human performance at nuclear power plants. The intent was to develop a defensible method that would consider all factors that may influence performance. In the SPAR-H approach, calculation of HEP rates is especially straightforward, starting with pre-defined nominal error rates for cognitive vs. action-oriented tasks, and incorporating performance shaping factor multipliers upon those nominal error rates

[en] Computerized procedures (CPs) are recognized as an emerging alternative to paper-based procedures for supporting control room operators in nuclear power plants undergoing life extension and in the concept of operations for advanced reactor designs. CPs potentially reduce operator workload, yield increases in efficiency, and provide for greater resilience. Yet, CPs may also adversely impact human and plant performance if not designed and implemented properly. Therefore, it is important to ensure that existing guidance is sufficient to provide for proper implementation and monitoring of CPs. In this paper, human performance issues were identified based on a review of the behavioral science literature, research on computerized procedures in nuclear and other industries, and a review of industry experience with CPs. The review of human performance issues led to the identification of a number of technical gaps in available guidance sources. To address some of the gaps, we developed 13 supplemental guidelines to support design and safety. This paper presents these guidelines and the case for further research.