In concurrent flow of two phase mixtures there exists a velocity difference between the vapor and liquid phases. This difference in velocity is known as the slip velocity. The prediction of slip is the subject of Part I. In boiling systems there is some heat transfer rate at which nucleste boiling becomes unstable. At this point the separate bubbles coalesce forming an insulating vapor film on the heat transfer surface resulting in the destruction, or burnout, of the heater. The prediction of the conditions causing burnout is the subject of Part II.

This report is a supplement to GEAP-3759, Plastic Strain In Thin Fuel Element Cladding Due to UO2 Thermal Expansion. Cladding growth results are reported for repetitively irradiated, UO2 pellet-filled, annular capsules: for two UO2 powder-filled, annular capsules: and for six solid cylindrical pellet-filled capsules. Dimensional changes of the capsules irradiated during the entire program were analyzed, and the relationship of these results to the over-all fuel development program were evaluated.

Task II-B of the High Performance UO2 Program calls for testing a series of UO2 fuel rods in the PW loop of the GETR. The purpose of the tests is to obtain a relationship between the extent of central melting and the length of time before the fuel rod fails as a result of interaction between the fuel and the cladding.

This report supersedes the similarly titled report dated December 31, 1958. It describes briefly features of the Dresden plant and proposes technical specifications.

This report contains technical specifications and supporting data for the Critical Experiment Facility, information to justify operation of the facility, procedural control to be used to ensure safe operation, changes in neutron instrumentation and safety system, an evaluation of the safety of the Facility. It also contains descriptions of the site, the facility and the Critical Assemblies, operating standards and procedures. Amendment no.18 to license application for Critical Experiment Facility is also attached.

This study was designed to determine how swaging stainless steel over unground pellets will affect the integrity of fuel rods, and to find maximum pellet diameter variation that can be tolerated.

Summary: Data were obtained in a two-road test section which consisted of two 7/16-inch diameter heater rods inside a roughly rectangular flow area. The heated length of the rods was 30 inches, with a 15-inch unheated calming length preceding it. Heater wall temperatures were recorded while the heater tubes were trans-versing the critical heat flux and transition boiling; these temperatures were used to calculate heat transfer coefficients. The following general results were obtaining: (a) Pressure has very little effect on the heat transfer coefficient in transition an film boiling. (b) Heat transfer coefficients during film boiling increase with mass velocity and steam quality. (c) The range of film boiling convective heat transfer coefficients observed was 364 to 1150 Btu/h-ft(2)-degrees F. (d) Temperature oscillations occur during transition boiling with a magnitude of as much 700 degrees F, at a frequency of about 1/2 cps. These temperature oscillations are reduced in magnitude as the steam quality and mass velocity are increased, becoming small (~20 degrees F) at high qualities and mass velocity. (e) A preliminary correlation of heat transfer coefficient data correlates the experimental data within about 20 percent. (f) Temperatures rises during transition boiling can be described analytically.

Summary: Tests with the two-rod assembly were performed with liquid film trippers attached to the unheated wall, and a variation in rod spacing. Experimental data and improved high-speed motion pictures have been obtained of transition boiling behavior. The changes of the local heat transfer process between nucleate and film boiling can be readily distinguished i the motion pictures. Observational test performed with very short fins on the heated surface resulted in essentially eliminating transition boiling temperature fluctuations and doubling the film boiling coefficient. These gains were attained without reduction of the critical heat flux

Introduction: The Transition Boiling Heat Transfer Program is sponsored jointly by the USAEC and Euroatom and is being conducted by the General Electric Company. The work commenced on this program February 11, 1963. The objective of this program is to perform basic investigation and measurement of the transition boiling regime in high pressure bulk boiling water flows, with particular emphasis i the high range of steam qualities.

Summary: Heat transfer tests employing the two-rod test section without film tripping devices have been completed. Representations defining critical heat flux, transition boiling and film boiling behavior at high pressures and over a steam quality range of 25 to 90 percent are shown. Fabrication of a new observational test section was completed and initial test results with high-speed motion pictures were obtained. A test loop instability which was found to affect transition boiling behavior was detected and partially eliminated.

Introduction: The Transition Boiling Heat Transfer Program is sponsored jointly by the USAEC and Euroatom and is being conducted by the General Electric Company. The work commenced on this program February 11, 1963. The objective of this program is to perform basic investigation and measurement of the transition boiling regime in high pressure bulk boiling water flows, with particular emphasis i the high range of steam qualities.

Summary: Transition boiling data was taken with an improved flow loop, to explore the influence of loop characteristics on rod temperature fluctuations the transition region was found to be much smaller than for comparable conditions with a different loop. Also the amplitude, and frequency of the temperature oscillations, were significantly less than before. These results indicate that loop characteristic and flow disturbance parameters play a prominent part in governing the transition temperature fluctuations. Additional two-rod transition boiling data are presented. The results include data taken at high wall temperature levels during a demonstration test at low steam qualities, and the effect of a change in rod spacing on heat transfer performance.

Summary: Initial critical heat flux, transition boiling temperature fluctuation, and film boiling coefficient data have been obtained on a two-rod cluster assembly at 1000 psia and 25 to 90 percent steam qualities. A representation showing the range of critical heat flux data is presented. Typical temperature recordings which indicate transition and film boiling behavior are shown. Fabrication of a new high pressure observational test section is nearly complete. An optical table and illumination system has been build and operationally tested for photographic use on the new observational section.

Technical report describing that voids were measured in a ½-inch by 1-3/4-inch channel with the S-1 insert (B(0)/B(1) = 0.4, L(0) = 0.1 inch), at 2 inches ahead of the insert (position A), ½-inch past the insert (position B), 5 inches past (position C), and 12 inches past (position D). The conditions were: P – 1000 psia, G = 1.00 x 10(6) lb/h-ft(2), and x = 18.8 percent. Average void and void distribution at position A are the same as for flow in a straight channel. Void distribution at position B shows that the stagnation region downstream of the inserts contains a high fraction of voids. Average void and void distribution at positions C and d show that the two-phase mixture becomes strongly mixed (homogenized) as a result of passing through he contraction-expansion inserts. Distribution at position D approaches the distribution at position A; i.e., the straight channel distribution.

Technical report describing that void measurements were made in the 1/2-inch by 1-3/4-inch rectangular channel, for both flow up and flow down, at pressures of 600, 1000, and 1400 psia, and at various flows and quantities. Results at 1000 psia and 20 percent quality show that for the lowest flow both the void distribution and the average void are much different for flow down than for flow up, the void fraction for flow down being much higher. However, when the flow is increased both the void distribution and average void for flow down tend to approach the corresponding values for flow up. At 1000 psia, both flow up and flow down, the void fraction for 5 percent quality increases gradually from the wall to the center of the channel, and peaks at the center. At 20 percent quality, the void fraction increases abruptly from the wall and tends to be constant over the middle 65 percent of the channel. the void fraction for flow down is always greater than for flow up, other things being equal.

Technical report describing that the pressure drops along 3/4-inch, 1-inch, and 1-1/4 inch straight pipes and across three contraction-expansion inserts in a 1-inch pipe have been measured under both single- and two-phase flow conditions. Pressure was varied from 600 to 1400 psia, flow from 0.25 x 10(6) to 1.66 x 10(6) lb/hr ft, and quality from zero to 90 percent. The single-phase pipe friction factor agrees with the Moody value for smooth pipe. The two-phase friction for horizontal flow shows no size effect in the range of pipe sizes from 3/4 inch to 1-1/4 inch. The values lie below the Martinelli curve at the lower qualities (x<0.6), but at high qualities tend to be above the Martinelli curve. The single-phase loss coefficient for the three contraction-expansion inserts show very little Reynolds number effect in the range of channel Reynolds numbers from 3 x 10(4) to 5 x 10(5). The two-phase data for insert number 1 has not yet been reduced. The two-phase loss for insert numbers 2 and 3 lies generally below the loss prediction based on a homogeneous flow model. The two-phase loss for insert number 2 shows excellent agreement with the corresponding loss for the S-1 insert in …

This is the second quarterly report on the work done under Contract AT(04-3)-189, Project Agreement No. 27. The results reported here have to do primarily with the loss in a rectangular (1/2" x 1-3/4") channel in the horizontal orientation, without contraction-expansion inserts.

This is the third quarterly report on the work done under Contract AT(04-30-189, Project Agreement No.27, and covers the period August 12 to November 12, 1962.

Abstract: Continued irradiation experience under the AEC - Euratom, UO2 High Performance Program provided five separate and distinct sets of data on UO2 thermal conductivity. Four of these results are expressed in terms of the value of the thermal conductivity. The first two of these measurements were applicable -- strictly -- to poly crystalline UO2. Recently, three additional sets of measurements have been obtained -- all pertinent to UO2 after the formation of large columnar grains. The extent of melting in the experiments on which the results are based ranges from slight, to greater than 70 percent of the fuel cross section. The conclusions from all of these thermal conductivity measurements considered together are: (1) The true value of the UO2 conductivity integral form 0 degrees C to melting (2805 - 15 degrees C) lies in the range from 90 to 96 W/cm. The most probable value is closer to 90 W/cm. To ensure no central melting and the associated clad swelling the maximum thermal performance level for solid pellet, UO2 fuel rods should not exceed 90 W/cm. (2) Any improvement in thermal conductivity due to the formation of large, columnar UO2 grains is small and not detectable within the …

Technical report describing that as part of the AEC Fuel Cycle Program, tests are being conducted to evaluate the significance of current fuel design limitations that do not permit the maximum fuel temperature to exceed the melting point of UO2. The reliability of prediction of the fuel rod operating conditions that will cause melting of the UO2 was evaluated by means of a calibration test conducted in the Vallecitos Boiling Water Reactor. Conclusions: (a) The central portion of the 3.15-cm diameter uranium dioxide fuel column melted. It appears that the UO2 was molten to a radius of 1.22 cm in the peak power region. The maximum extent of melting probably occurred during the peak power run when the kdT in this region of the rod reached 171 watts cm. The estimated radius of melting from metallographic examination indicates the kdT for sintered UO2 is 89 watts/cm. This supports a calculated estimate for sintered UO2 thermal conductivity published by D. R. deHalas and G. R. Horn. The results of the previous calibration run and subsequent experimental data by Lyons are also consistent with the value. This conclusion is contingent on the interpretation of the post-irradiation crystal structure of the UO2. Insufficient …

Writing the VARI-II Program was motivated by the need for a method of analyzing the results for the Absorber Burn-Up Experiment in progress at the Vallecitos Atomic Laboratory.

VARI solves on the IBM-650 a system of simultaneous, first-order, ordinary, differential equations. The program was written so that a large number of calculations could be done in a reasonable length of time. The program permits the consideration of the production of the isotope by absorption and/or decay of one or more of any of the other isotopes in the chain.

The fabricability, elevated temperature strength, steam corrosion resistance, and hydrogen pickup of various binary, ternary, and quaternary alloys were studied experimentally.