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Mohammed A Quaiyum – One of the best experts on this subject based on the ideXlab platform.

  • contact conductance between cladding Pressure tube and Pressure tube calandria tube of advanced thermal reactor atr
    Journal of Nuclear Science and Technology, 1994
    Co-Authors: Hiroyasu Mochizuki, Mohammed A Quaiyum
    Abstract:

    In some postulated accidents with coincident loss of emergency coolant injection of the Advanced Thermal Reactor (ATR), the rate of heat transfer to the heavy water moderator that acts as heat sink for the decay heat depends on the contact conductance between cladding and Pressure tube, and the same between Pressure and calandria tubes. Experiments were performed to assess these contact conductances for clean plates and plates with simulated crud of Fe2O3 powder that is the main ingredient of the crud, and the applicable correlations were also studied. Test specimens were cut from Actual Pressure tube made of Zr-2.5%Nb and calandria tube made of Zircaloy-2 and flattened to sizes. The artificial waviness of various kinds of height and wave length of 10 mm was machined on the surface of the Pressure tube specimen. The ranges of contact Pressure, roughness, specimen temperature and gas Pressure were from 0.5 to 7 MPa, 4.8 to 100 μm, 400 to 840 K and 0.001 Torr to atmospheric respectively. The experimental re…

  • Contact Conductance between Cladding/Pressure Tube and Pressure Tube/Calandria Tube of Advanced Thermal Reactor (ATR)
    Journal of Nuclear Science and Technology, 1994
    Co-Authors: Hiroyasu Mochizuki, Mohammed A Quaiyum
    Abstract:

    In some postulated accidents with coincident loss of emergency coolant injection of the Advanced Thermal Reactor (ATR), the rate of heat transfer to the heavy water moderator that acts as heat sink for the decay heat depends on the contact conductance between cladding and Pressure tube, and the same between Pressure and calandria tubes. Experiments were performed to assess these contact conductances for clean plates and plates with simulated crud of Fe2O3 powder that is the main ingredient of the crud, and the applicable correlations were also studied. Test specimens were cut from Actual Pressure tube made of Zr-2.5%Nb and calandria tube made of Zircaloy-2 and flattened to sizes. The artificial waviness of various kinds of height and wave length of 10 mm was machined on the surface of the Pressure tube specimen. The ranges of contact Pressure, roughness, specimen temperature and gas Pressure were from 0.5 to 7 MPa, 4.8 to 100 μm, 400 to 840 K and 0.001 Torr to atmospheric respectively. The experimental re…

Hiroyasu Mochizuki – One of the best experts on this subject based on the ideXlab platform.

  • contact conductance between cladding Pressure tube and Pressure tube calandria tube of advanced thermal reactor atr
    Journal of Nuclear Science and Technology, 1994
    Co-Authors: Hiroyasu Mochizuki, Mohammed A Quaiyum
    Abstract:

    In some postulated accidents with coincident loss of emergency coolant injection of the Advanced Thermal Reactor (ATR), the rate of heat transfer to the heavy water moderator that acts as heat sink for the decay heat depends on the contact conductance between cladding and Pressure tube, and the same between Pressure and calandria tubes. Experiments were performed to assess these contact conductances for clean plates and plates with simulated crud of Fe2O3 powder that is the main ingredient of the crud, and the applicable correlations were also studied. Test specimens were cut from Actual Pressure tube made of Zr-2.5%Nb and calandria tube made of Zircaloy-2 and flattened to sizes. The artificial waviness of various kinds of height and wave length of 10 mm was machined on the surface of the Pressure tube specimen. The ranges of contact Pressure, roughness, specimen temperature and gas Pressure were from 0.5 to 7 MPa, 4.8 to 100 μm, 400 to 840 K and 0.001 Torr to atmospheric respectively. The experimental re…

  • Contact Conductance between Cladding/Pressure Tube and Pressure Tube/Calandria Tube of Advanced Thermal Reactor (ATR)
    Journal of Nuclear Science and Technology, 1994
    Co-Authors: Hiroyasu Mochizuki, Mohammed A Quaiyum
    Abstract:

    In some postulated accidents with coincident loss of emergency coolant injection of the Advanced Thermal Reactor (ATR), the rate of heat transfer to the heavy water moderator that acts as heat sink for the decay heat depends on the contact conductance between cladding and Pressure tube, and the same between Pressure and calandria tubes. Experiments were performed to assess these contact conductances for clean plates and plates with simulated crud of Fe2O3 powder that is the main ingredient of the crud, and the applicable correlations were also studied. Test specimens were cut from Actual Pressure tube made of Zr-2.5%Nb and calandria tube made of Zircaloy-2 and flattened to sizes. The artificial waviness of various kinds of height and wave length of 10 mm was machined on the surface of the Pressure tube specimen. The ranges of contact Pressure, roughness, specimen temperature and gas Pressure were from 0.5 to 7 MPa, 4.8 to 100 μm, 400 to 840 K and 0.001 Torr to atmospheric respectively. The experimental re…

Guy R. Heyndrickx – One of the best experts on this subject based on the ideXlab platform.

  • Percutaneous transluminal coronary angioplasty catheters versus fluid-filled Pressure monitoring guidewires for coronary Pressure measurements and correlation with quantitative coronary angiography
    The American journal of cardiology, 1993
    Co-Authors: Bernard De Bruyne, Stanislas U. Sys, Guy R. Heyndrickx
    Abstract:

    Abstract The functional significance of a coronary stenosis can be assessed by measuring the translesional Pressure gradient. Thirty-four patients were studied in the setting of percutaneous transluminal coronary angioplasty (PTCA) to evaluate the clinical relevance of the Pressure gradient measurements by means of a PTCA balloon catheter. Both before and after PTCA, the mean Pressure gradient across the stenosis was measured by means of a newly developed, 0.015-inch Pressure-monitoring guidewire, first with only the wire across the stenosis (ΔP W , considered as the Actual gradient), and second with the deflated balloon catheter advanced over the wire in the stenosis (ΔP b ). Pressure gradients were correlated with quantitative coronary angiography of the stenotic segment. Before PTCA, mean ΔP b was larger than ΔP W (62 ± 14 vs 30 ± 20 mm Hg; p b remained systematically higher than ΔP W (23 ± 14 vs 3 ± 5 mm Hg; p 2 . A significant correlation was found between ΔP W and percent area stenosis (r 2 = 0.66), with a marked increase after percent area stenosis reached 80%. The correlation between ΔP b and percent area stenosis was weaker (r 2 = 0.53), the scatter of the data was larger, and the inflection point of the curve was shifted toward less severe degrees of stenosis severity. The relation between the percent overestimation produced by the presence of the PTCA balloon catheter and either ΔP W or the ratio between catheter and obstruction cross-sectional area suggested that in intermediate lesions and post-PTCA segments, the overestimation was poorly predictable. Thus, the presence of a PTCA catheter through a coronary stenosis causes a systematic and unpredictable overestimation of the Actual Pressure gradient. Even after PTCA, the Pressure gradient measured with the balloon catheter does not reflect the hemodynamic significance of the dilated segment.

  • transstenotic coronary Pressure gradient measurement in humans in vitro and in vivo evaluation of a new Pressure monitoring angioplasty guide wire
    Journal of the American College of Cardiology, 1993
    Co-Authors: Bernard De Bruyne, Guy R. Heyndrickx, Stanislas U. Sys, Walter Paulus, Pascal J Vantrimpont, Nico H J Pijls
    Abstract:

    Objectives. The present study was designed to investigate 1) the feasibility and accuracy of coronary Pressure measurements with a novel 0.015-in. (0.038 cm) fluid-filled guide wire, and 2) the effect of the guide wire itself on stenosis hemodynamics. Background. To assess the functional results of coronary angioplasty, measurements of the transstenotic Pressure gradient have been advocated. However, this is no longer routinely measured because it is not reliable when determined with the angioplasty catheter. Methods. A fluid-filled 0.015-in. guide wire to be connected to a conventional Pressure transducer was developed. Five wires were tested for their frequency response characteristics and for their accuracy in measuring hydrostatic Pressure. In an in vitro model of stenosis (reference diameter 4 mm), the Pressure gradient was determined at incremental flow levels for varying stenosis severity with and without a 0.015-in. guide wire through the narrowing. In 37 patients, the transstenotic Pressure gradient was measured before and after angioplasty and compared with obstruction area and percent area stenosis as determined by quantitative coronary angiography. Results. The correlation between the Actual Pressure and the Pressure recorded by the guide wire was excellent (r = 0.98) despite a slight underestimation (−3 ± 5%). Phasic Pressure recordings were precluded by a long time constant of 16 ± 4 s. The presence of the guide wire produced a significant overestimation (>20%) of the Pressure decrease only in cases of tight stenosis (>90% area reduction). Furthermore, a theoretic model based on the fluid dynamic equation predicted that this overestimation was inversely proportional to the reference diameter of the vessel, yet was only slightly influenced by the flow. The lesion was crossed in all but one (97%) and Pressure gradient was recorded throughout the study in 34 (94%) of 36 patients. The mean Pressure gradient decreased from 30 ± 19 before to 3 ± 5 mm Hg after angioplasty (p < 0.01). A curvilinear relation was found between the Pressure gradient and both percent area stenosis (r2= 0.67) and obstruction area (r2= 0.72). A sharp increase in Pressure gradient was noted once the stenosis exceeded 75% area reduction. Conclusions. Mean transstenotic Pressure gradients can be easily and reliably recorded with a 0.015-in. fluid-filled guide wire. This ability should facilitate the functional assessment of coronary stenoses of intermediate severity and of immediate postangioplasty results.