centerline temperature
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Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1460
Author(s):  
Ruibang Sun ◽  
Xing Yang ◽  
Juncai Wang ◽  
Peng Chen ◽  
Liusuo Wu

With the widespread use of substations around the world, oil jet fire accidents from transformer oil-filled equipment in substations caused by faults have occurred from time to time. In this paper, a series of transformer oil jet fire experiments are carried out by changing the external heat source (30 cm and 40 cm) and the inner diameter of the container (5 cm, 8 cm and 10 cm) to study the axial centerline temperature distribution of the transformer oil jet fire plume of the transformer oil-filled equipment in the substation. The experiment uses K-type thermocouple, electronic balance and CCD to measure and assess the temperature distribution of the axial centerline of the fire plume of the transformer oil jet. The result demonstrates that the axial centerline temperature of the fire plume increases with the external heat release rate and the inner diameter of the container. In addition, a novel axial temperature distribution prediction model of the transformer oil jet fire plume is established. This model can effectively predict the oil jet fire plume temperature of transformer oil- filling equipment in substations, and provide help for substation fire control.


2021 ◽  
Vol 9 ◽  
Author(s):  
Shengyu Liu ◽  
Rong Liu ◽  
Chengjie Qiu ◽  
Wenzhong Zhou

Using the finite element multiphysics modeling method, the performance of the thorium-based fuel with Cr-coated SiC/SiC composite cladding under both normal operating and accident conditions was investigated in this work. First, the material properties of SiC/SiC composite and chromium were reviewed. Then, the implemented model was simulated, and the results were compared with those of the FRAPTRAN code to verify the correctness of the model used in this work. Finally, the fuel performance of the Th0.923U0.077O2 fuel, Th0.923Pu0.077O2 fuel, and UO2 fuel combined with the Cr-coated SiC/SiC composite cladding and Zircaloy cladding, respectively, was investigated and compared under both normal operating and accident conditions. Compared with the UO2 fuel, the Th0.923U0.077O2 and Th0.923Pu0.077O2 fuels were found to increase the fuel centerline temperature under both normal operating and reactivity-initiated accident (RIA) conditions, but decrease the fuel centerline temperature under loss-of-coolant accident (LOCA) condition. Moreover, compared to the UO2 fuel with the Zircaloy cladding, thorium-based fuels with Cr-coated SiC/SiC composite cladding were found to show better mechanical performance such as delaying the failure time by about 3 s of the Cr-coated SiC/SiC composite cladding under LOCA condition, and reducing the plenum pressure by about 0.4 MPa at the peak value in the fuel rod and the hoop strain of the cladding by about 16% under RIA condition.


Kerntechnik ◽  
2021 ◽  
Vol 86 (3) ◽  
pp. 202-209
Author(s):  
M. Ghasabian ◽  
F. Mofidnakhaei ◽  
S. Talebi

Abstract The fuel burn-up rate has been raised in recent years to improve the efficiency of nuclear LWRs (light water reactors). Therefore, surveying and estimating changes in fuel properties and structural materials during radiation exposure is of paramount importance. In the present study, the researchers focused on analyzing the role of LWR fuel rod initial gap pressure (initial gas pressure when a fuel rod is fabricated) on the rod’s thermal and mechanical performance. FRAPCON-4.0 steady-state fuel performance code was used to simulate the effect of initial gap pressure on the behavior of a specific BWR-type fuel rod that was irradiated under the HALDEN research program. This fuel rod is similar to commercial BWR fuel rods in all respects, except that the research reactors have a height limit. The important fuel design criteria, such as the centerline temperature, effective stresses, total released fission gas to the fuel rod’s void volumes, and the cladding strains, were included in the analysis. According to the present study, a potential initial gap pressure range could be suggested to increase fuel rods’ lifetime by improving the safety criteria margins, especially fuel centerline temperature and the released amount of gaseous fission products. As we know, lower fuel temperature leads to having a reactor with a higher power density and, consequently, a maximum fuel burn-up rate, which can affect the economy and safety of nuclear power plants.


2020 ◽  
Vol 6 (4) ◽  
Author(s):  
Jason J. Song ◽  
Paul K. Chan ◽  
Hugues W. Bonin ◽  
Mahesh Pandey

Abstract A novel method of assessing the reliability of 37-element Canada deuterium uranium (reactor) (CANDU) fuel bundle was explored. The method implements a “best-estimate plus uncertainty” (BEPU) approach where a probabilistic treatment of manufacturing and operating inputs is used to predict fuel performance. The fuel performance was predicted using the Canadian industry standard codes for fuel performance, ELESTRESS and ELOCA, which, respectively, model fuel behaviors during normal and transient conditions. The outputs of the codes were compared against failure criteria from industry norms to determine the probability of failure. A Monte Carlo simulation method was applied to analyze this problem. Probability distributions of manufacturing input variables were estimated from real data, which were then randomly sampled. The inputs for fuel burnup and power were simulated using core-following data generated using a three-dimensional diffusion code, the Reactor Fuelling Simulation Program (RFSP), which were also then randomly sampled. The results of the simulations predict significant improvements in margins to limits for all performance parameters. An average improvement of 500 °C in centerline temperature, 10 °C in sheath temperature, 12 MPa in element internal pressure, and 0.8% in pellet end sheath hoop strain was predicted for the highest-powered region of the core, during normal operations, in comparison with the limit-of-envelope (LOE) benchmark. An 80% reactor overhead break (ROH) transient simulation was also simulated, and an average improvement of 500 °C in centerline temperature, 150 °C in sheath temperature, 6.5 MPa in internal pressure, and 2% in sheath hoop strain was predicted.


Author(s):  
Rong Liu ◽  
Jie-Jin Cai ◽  
Wen-Zhong Zhou ◽  
Ye Wang

ThO2 has been considered as a possible replacement for UO2 fuel for future generation of nuclear reactors, and thorium-based mixed oxide (Th-MOX) fuel performance in a light water reactor was investigated due to better neutronics properties and proliferation resistance compared to conventional UO2 fuel. In this study, the thermal, mechanical properties of Th0.923U0.077O2 and Th0.923Pu0.077O2 fuel were reviewed with updated properties and compared with UO2 fuel, and the corresponding fuel performance in a light water reactor under normal operation conditions were also analyzed and compared by using CAMPUS code. The Th0.923U0.077O2 fuel were found to decrease the fuel centerline temperature, while Th0.923Pu0.077O2 fuel was found to have a bit higher fuel centerline temperature than UO2 fuel at the beginning of fuel burnup, and then much lower fuel centerline than UO2 fuel at high fuel burnup. The Th0.923U0.077O2 fuel was found to have lowest fuel centerline temperature, fission gas release and plenum pressure. While the Th0.923Pu0.077O2 fuel was found to have earliest gap closure time with much less fission gas release and much lower plenum pressure compared to UO2 fuel. So the fuel performance could be expected to be improved by applying Th0.923U0.077O2 and Th0.923Pu0.077O2 fuel.


2018 ◽  
Vol 36 (4) ◽  
pp. 362-375 ◽  
Author(s):  
Cong Li ◽  
Rui Yang ◽  
Yina Yao ◽  
Zhenxiang Tao ◽  
Hui Zhang

This article presents an experimental investigation on the pool fire plume characteristics in a full-scale depressurized aircraft cargo compartment. The effects of decreasing pressure and vent flow rate on the fire characteristics such as flame shape, flame puffing, flame height, and centerline temperature were analyzed. The results show that during the depressurization process, the ventilation had an activation effect on the mass loss rate, and its increment had a linear relationship with the dimensionless ventilation factor. In addition, the larger depressurized rate caused the larger dimensionless ventilation factor and further resulted in the larger increment of mass loss rate. The flame puffing frequency was determined by the ratio of the gas density in the flame area of that in the ambient air, which increased with the drop of pressure. For flame centerline temperature, there was a counteraction area in the flame intermittent region, where the centerline temperature had almost no difference before and after the depressurization. The conclusions could provide the theoretical base and reference materials for the fire disaster in the cargo compartment of real aircrafts.


Author(s):  
Jayangani Ranasinghe ◽  
Barbara Szpunar ◽  
Ericmoore Jossou ◽  
Linu Malakkal ◽  
Jerzy A. Szpunar

In this study, we analyze and compare the temperature profiles, and temperature gradient profiles of UN, U3Si2 and U3O8 aluminum (Al) dispersed nuclear fuels to propose safer nuclear fuels with enhanced thermal conductivity. To calculate the electronic and lattice thermal conductivities, we use EPW, BoltzTrap and ShengBTE codes implemented with Quantum Espresso. Maxwell-Eucken approximation is used to get the effective thermal conductivity of the considered dispersed fuels. The temperature and temperature gradients are calculated by solving the steady state heat conduction equation for a cylindrical fuel rod. Results show that these fuels have reduced the centerline temperature which will prevent fuel melting, as well it will reduce the thermal stress which leads to cracking the pellet.


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