Forced convection degraded core cooling in light water reactors

Includes bibliographical references (pages 135-141)Work performed with support from E.G. & Idaho, In

Experimental investigation of the thermal-hydraulics of gas jet expansion In a two-dimensional liquid pool

"October 1978."Also issued as an M.S. thesis by the first author and supervised by the second author, MIT Dept. of Nuclear Engineering, 1978Includes bibliographical references (pages 115-117)Gas jet blowdown in a two-dimensional liquid pool has been experimentally investigated. Two sets of experiments were performed: a set of hydrodynamic experiments, where a non-condensible gas is injected into a subcooled liquid pool; and a set of thermal-hydraulic experiments, where a non-condensible heated gas is injected into a near saturated liquid pool. Liquid entrainment by the gas, bubble growth characteristics, and the potential for vaporization, were investigated for a variety of experimental pressures (3 to 10 bars) and two liquid types (water and R-113). Liquid entrainment increased with increasing pressure. The fraction of the jet volume which is liquid is relatively the same for all pressures and decreases with time of expansion. A Taylor instability mechanism for entrainment is found to under predict the entrained volume. In the initial stages of the expansion, higher entrainment is experienced for more dense fluids. For the same fluid, the entrainment rate was slightly higher for the heated experiments compared to the unheated experiments. Both lateral and vertical growth rates increased with pressure. Vaporization may have occurred for the 4 bar initial pressure, 12 °C superheat condition in freon R-113.Report issues under contract with the U.S. Nuclear Regulatory Commission NRC-04-77-12

Failure of Buildings Founded on Fills

A number of cases have come to light in Delhi recently where partial or total failure of buildings has occurred. Two cases of failures due to excessive settlement are discussed. The nature of distress and the geotechnical factors leading to failures were investigated. It was found that in both cases the foundations were resting on fills, resulting in excessive settlement. Remedial measures were considered and in one case, these have been successfully implemented. A large number of structures were thus rehabilitated

Theoretical studies on some aspects of molten fuel-coolant thermal interaction.

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1973. Ph.D.Includes bibliographical references.Ph.D

Modeling of fuel-to-steel heat transfer in core disruptive accidents

"June 1980."Also issued as a Ph. D. thesis by the first author, MIT Dept. of Nuclear Engineering, 1980Includes bibliographical references (pages 110-111)A mathematical model for direct-contact boiling heat transfer between immiscible fluids was developed and tested experimentally. The model describes heat transfer from a hot fluid bath to an ensemble of droplets of a cooler fluid that boils as it passes through the hot fluid. The mathematical model is based on single bubble correlations for the heat transfer and a drift-flux model for the fluid dynamics. The model yields a volumetric heat transfer coefficient as a function of the initial diameter, velocity and volume fraction of the dispersed component. An experiment was constructed to boil cyclopentane droplets in water. The mathematical and experimental results agreed reasonably well. The results were applied to investigate the possibility of steel vaporization during a hypothetical core disruptive accident in a liquid metal fast breeder reactor. The model predicts that substantial steel vaporization may occur in core disruptive accidents, if the steel reaches its saturation temperature rapidly enough. The potential importance of steel vaporization is dependent on the accident scenario.Report issued under contract with the U.S. Nuclear Regulatory Commission NRC-04-77-12

Bunch Length Measurements at the CEBAF Injector at 130 kV

In this work, we investigated the evolution in bunch length of beams through the CEBAF injector for low to high charge per bunch. Using the General Particle Tracer (GPT), we have simulated the beams through the beamline of the CEBAF injector and analyzed the beam to get the bunch lengths at the location of chopper. We performed these simulations with the existing injector using a 130 kV gun voltage. Finally, we describe measurements to validate these simulations. The measurements have been done using chopper scanning technique for two injector laser drive frequency modes: one with 500 MHz, and another with 250 MHz

Production of highly-polarized positrons using polarized electrons at MeV energies

The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-$Z$ target. Positron polarization up to 82\% have been measured for an initial electron beam momentum of 8.19~MeV/$c$, limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.Comment: 5 pages, 4 figure

CEBAF Injector Model for K\u3csub\u3eL\u3c/sub\u3e Beam Conditions

The Jefferson Lab KL experiment will run at the Continuous Electron Beam Accelerator Facility with a much lower bunch repetition rate (7.80 or 15.59 MHz) than nominally used (249.5 or 499 MHz). While the proposed average current of 2.5 - 5.0 µA is relatively low compared to the maximum CEBAF current of approximately 180 µA, the corresponding bunch charge is atypically high for CEBAF injector operation. In this work, we investigated the evolution and transmission of low-rep-rate, high-bunch-charge (0.32 to 0.64 pC) beams through the CEBAF injector. Using the commercial software General Particle Tracer, we have simulated and analyzed the beam characteristics for both values of bunch charge. We performed these simulations with the existing injector using a 130 kV gun voltage. We have calculated and measured the transmission as a function of the photocathode laser spot size and pulse length. We report on the findings of these simulations and optimum parameters for operating the experiment

High Current High Charge Magnetized and Bunched Electron Beam From a DC Photogun for JLEIC Cooler

A high current, high charge magnetized electron beamline that has been under development for fast and efficient cooling of ion beams for the proposed Jefferson Lab Electron Ion Collider (JLEIC). In this paper, we present the latest progress over the past year that include the generation of picosecond magnetized beam bunches at average currents up to 28 mA with exceptionally long photocathode lifetime, and the demonstrations of magnetized beam with high bunch charge up to 700 pC at 10s of kHz repetition rates. Detailed studies on a stable drive laser system, long lifetime photocathode, beam magnetization effect, beam diagnostics, and a comparison between experiment and simulations will also be reported. These accomplishes marked an important step towards the essential feasibility for the JLEIC cooler design using magnetized beams

Compact \u3cb\u3e-300 kV\u3c/b\u3e dc Inverted Insulator Photogun With Biased Anode and Alkali-Antimonide Photocathode

This contribution describes the latest milestones of a multiyear program to build and operate a compact −300  kV dc high voltage photogun with inverted insulator geometry and alkali-antimonide photocathodes. Photocathode thermal emittance measurements and quantum efficiency charge lifetime measurements at average current up to 4.5 mA are presented, as well as an innovative implementation of ion generation and tracking simulations to explain the benefits of a biased anode to repel beam line ions from the anode-cathode gap, to dramatically improve the operating lifetime of the photogun and eliminate the occurrence of micro-arc discharges