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As part of the Department of Energys Light Water Reactor Sustainability Program (LWRSP), tools and methodology for risk-informed characterization of safety margin are being developed for use in supporting decision-making on plant life... more
As part of the Department of Energys Light Water Reactor Sustainability Program (LWRSP), tools and methodology for risk-informed characterization of safety margin are being developed for use in supporting decision-making on plant life extension after the first license renewal. Beginning with the traditional discussion of margin in terms of a load (a physical challenge to system or component function) and
Research Interests:
Following completion of the full-power operation probabilistic risk assessment (PRA) for the Advanced Test Reactor (ATR), a shutdown PRA was initiated to provide coverage of operating configurations not previously analyzed. As has been... more
Following completion of the full-power operation probabilistic risk assessment (PRA) for the Advanced Test Reactor (ATR), a shutdown PRA was initiated to provide coverage of operating configurations not previously analyzed. As has been typical, full-power operation was the primary focus of previous PRA activities; however, recent nuclear industry interest in non-full-power operation prompted the effort. Because of the many variables
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The increase in systemic blood pressure after an obstructive apnea is due, in part, to sympathetically mediated vasoconstriction. We questioned whether upper airway (UA) receptors could contribute reflexly to this vasoconstriction. Four... more
The increase in systemic blood pressure after an obstructive apnea is due, in part, to sympathetically mediated vasoconstriction. We questioned whether upper airway (UA) receptors could contribute reflexly to this vasoconstriction. Four unanesthetized dogs were studied during wakefulness and non-rapid-eye-movement (NREM) sleep. The dogs breathed via a fenestrated tracheostomy tube sealed around the tracheal stoma. The snout was sealed with an airtight mask, thereby isolating the UA when the fenestration was closed and exposing the UA to negative inspiratory intrathoracic pressure when it was open. The blood pressure response to three UA perturbations was studied: 1) square-wave negative pressures sufficient to cause UA collapse with the fenestration closed during a mechanical hyperventilation-induced central apnea; 2) tracheal occlusion with the fenestration open vs. closed; and 3) high-frequency pressure oscillations (HFPO) with the fenestration closed. During NREM sleep, 1) blood ...
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To determine the effect of upper airway (UA) negative pressure and collapse during inspiration on regulation of breathing, we studied four unanesthetized female dogs during wakefulness and sleep while they breathed via a fenestrated... more
To determine the effect of upper airway (UA) negative pressure and collapse during inspiration on regulation of breathing, we studied four unanesthetized female dogs during wakefulness and sleep while they breathed via a fenestrated tracheostomy tube, which was sealed around the permanent tracheal stoma. The snout was sealed with an airtight mask, thereby isolating the UA when the fenestration (Fen) was closed and exposing the UA to intrathoracic pressure changes, but not to flow changes, when Fen was open. During tracheal occlusion with Fen closed, inspiratory time (TI) increased during wakefulness, non-rapid-eye-movement (NREM) sleep and rapid-eye-movement (REM) sleep (155 +/- 8, 164 +/- 11, and 161 +/- 32%, respectively), reflecting the removal of inhibitory lung inflation reflexes. During tracheal occlusion with Fen open (vs. Fen closed): 1) the UA remained patent; 2) TI further increased during wakefulness and NREM (215 +/- 52 and 197 +/- 28%, respectively) but nonsignificantly...
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The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) refers to a set of computer programs that were developed to create and analyze probabilistic risk assessment (PRAs). Herein information is provided on... more
The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) refers to a set of computer programs that were developed to create and analyze probabilistic risk assessment (PRAs). Herein information is provided on the principles used in the construction and operation of Version 8.0 of the SAPHIRE system. This report summarizes the fundamental mathematical concepts of sets and logic, fault
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The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) suite of programs can be used to organize and standardize in an electronic format information from probabilistic risk assessments or individual plant... more
The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) suite of programs can be used to organize and standardize in an electronic format information from probabilistic risk assessments or individual plant examinations. The Models and Results Database (MAR-D) program of the SAPHIRE suite serves as the repository for probabilistic risk assessment and individual plant examination data and information. This report demonstrates by examples the common electronic and manual methods used to load these types of data. It is not a stand alone document but references documents that contribute information relative to the data loading process. This document provides a more detailed discussion and instructions for using SAPHIRE 5.0 only when enough information on a specific topic is not provided by another available source.
Research Interests:
As part of the Department of Energys Light Water Reactor Sustainability Program (LWRSP), tools and methodology for risk-informed characterization of safety margin are being developed for use in supporting decision-making on plant life... more
As part of the Department of Energys Light Water Reactor Sustainability Program (LWRSP), tools and methodology for risk-informed characterization of safety margin are being developed for use in supporting decision-making on plant life extension after the first license renewal. Beginning with the traditional discussion of margin in terms of a load (a physical challenge to system or component function) and
Research Interests:
Research Interests:
In six dogs studied in nonrapid eye movement (NREM) sleep, we found that the frequency, volume, and timing of application of mechanical ventilator breaths had marked and sustained inhibitory effects on diaphragm electromyogram (EMG(di)).... more
In six dogs studied in nonrapid eye movement (NREM) sleep, we found that the frequency, volume, and timing of application of mechanical ventilator breaths had marked and sustained inhibitory effects on diaphragm electromyogram (EMG(di)). Single ventilator breaths of tidal volume (VT) 75-200% of control caused apnea (up to three times eupneic expiratory time [TE]) when applied during the initial 25-65% of expiratory time. When continuous controlled mechanical ventilation (CMV) was applied with ventilator frequency increased as little as 1 cycle/min > eupnea and Pa(CO(2)) and VT maintained at near eupneic control levels, EMG(di) was silenced and triangularis sterni EMG (EMG(ts)) became tonic within 2 to 5 ventilator cycles. On cessation of normocapnic CMV, apnea ensued with TE ranging from 1.2 to five times eupneic TE. The spontaneous VT and EMG(di) determined immediately after these prolonged apneas were also markedly reduced in amplitude. The larger the VT applied during the isocapnic CMV (120-200% of eupnea) and the longer the duration of the CMV (3-90 s), the longer the duration of the postventilator apnea. Significant postventilator apneas and postapneic hypoventilation also occurred even when end-tidal CO(2) pressure (PET(CO(2))) was raised 3-5 mm Hg > eupnea (and 7-10 mm Hg > normal apneic threshold) throughout CMV trials at raised frequency and VT. Our findings demonstrate that the increased frequency of CMV was critical to the elimination of inspiratory motor output and the onset of tonic expiratory muscle activity; furthermore, once EMG(di) was silenced, the tidal volume and duration of the passive mechanical ventilation determined the magnitude of the short-term inhibition of inspiratory motor output after cessation of CMV.