Quarterly progress report on Accurate Nuclear Fuel Burnup Analysis project.

A potential performance limitation of superheat fuel is the susceptibility of the fuel cladding to low cycle fatigue failure. Two simplified analytical methods are presented to estimate the cyclic lifetime of circular superheat fuel cladding. One failure relation is based on a displacement method. The other failure relation is based on a stress method. These relations were compared with data from the literature, and with data involving damage obtained by Reynolds. A recommended design procedure involving the relations is presented. The technique was applied to the SADE 4B experiment with moderate success. These cycling relations involve only mechanical damage imposed by cycling, with a modification for additional damage caused by radiation; they do not include any other potential performance limiting mechanisms, such as stress corrosion, which are normally factored into the over-all fuel design. This work work done under Task C (Materials Development) of the Nuclear Superheat Project, AEC Contract AT(04-3)-189 - Project Agreement 13.

Tests were run at the General Electric Company, Atomic Power Equipment Department, to determine the burnout conditions for a non-uniformly heated rod in an annular geometry.

A process was developed in which stainless steel-clad UO2 fuel rods are fabricated by high-temperature coextrusion. The process has a potential of being a more economical method for the preparation of stainless steel-clad UO2 fuel rods than the conventional pellet process. Consequently, it was considered advantageous to evaluate the irradiation characteristics of fuel rods fabricated in this manner. Therefore, 24 coextruded fuel rods were manufactured for evaluation in a reactor. The required amounts of UO2 and clad were soaked in separate containers at 1875 and 760 degree C, respectively. The containers were removed from their respective furnaces and were coextruded in one pass. A force of 450 to 475 tons was used, and a reduction ratio of 18 to 1 was obtained. The coextruded rods were cut to the approximate length, and the ends were sealed with an acid-resistant tape. The carbon steel can covering the stainless steel clad was removed by immersion in 1:1 nitric acid for 20 minutes. The rods were visually inspected, the specified lengths of clad and fuel were obtained by machining, and the correct diameter was obtained by belt sanding. The fabrication of the fuel rods was completed by inserting the plenum support tubes and …

The nuclide Cs-137 is a fission product commonly used for measurement of uranium burnup in irradiated uranium fuel by the fission product to uranium ratio method. In the application of this method, the largest single error introduced in the measurement of burnup is the uncertainty in the half-life of Cs-137. Because of the uncertainty in this value and its importance in nuclear fuel burnup analysis, a reinvestigation was undertaken to obtain a more accurate value using the mass spectrometric method.

Work performed during the quarter is summarized by direct measurement of fission gas pressure, loop modifications, UO2 fuel performance

Introduction: The object of Project Agreement 22, Task 1, is to develop improved detectors which can operate up to 1000 F for in-core power monitoring. Several ideas have been developed to achieve this goal: (1) root mean square fluctuation voltage measurement of ion chamber signals, (2) thermocouple-type detectors, and (3) fabrication developments.

From introduction: "This is the ninth of a series of quarterly reports which will cover the progress and results from the conceptual design, economic evaluations and research and development work performed by the General Electric Company as part of the Nuclear Superheat Project."

The General Electric Company is designing and building a 180,000 kilowatt nuclear power plant for the Commonwealth Edison Company at a site 47 miles southwest of Chicago. The construction permit was issued on May 4, 1956 but is subject to submittal to the Commission of a final hazards summary report and a finding by the Commission that the final design provides reasonable assurances that the health and safety of the public will not be endangered by operation of the reactor in accordance with the specified procedures.

This report describes progress made in the study of the feasibility of the concept, plant arrangement studies, and considerations pertaining to partial plant attendance. It is concluded that both the indirect and direct boiling cycles are feasible. The recommended reference design is the direct cycle, in a single capsule, with the turbine, generator and pumps on a single shaft.

The pressure drop of a new fuel element design concept of spacing rods by means of helical wire springs was investigated experimentally and analytically.

Task A: Modification and Preparation of Experimental Facility. Facility engineering and layout is about seventy-five percent complete. Task B: Design and Construction of Test Sections. The major dimensions and characteristics of the metal and glass test sections have been calculated. One feasibility test of the electrically conducting coating on samples of glass tubing has been completed. Task C: Design and Construction of Test Stand, Task E: Pressure and Temperature Instrumentation for Test Section and Task F: Power Supply for Test Section. Preliminary engineering has been initiated on these tasks. The planned approach has been defined in each case. For Task E the transducer specifications have been defined and quotations on and/or sample units of the transducers have been requested. Tasks C and F can proceed with detailing as soon as drafting on Task B is about 50 percent complete. This point is scheduled to be reached during the first part of July. Task D: Void Fraction Instrumentation. The requirements for the x-ray instrumentation have been considered in the course of Task B and the x-ray power supply is presently on hand. The detailed engineering effort on this task is not scheduled to begin before July.

A code (RAPTURE) was programmed for the Philco TRANSAC 2000 computer to perform calculations needed for the evaluation of Doppler Coefficients in fast reactors with degraded neuron spectra. This code computes resonance integrals, averages them over resonance parameter distributions, and computes fission and capture cross sections as a function of fuel temperature and of potential scattering cross section per absorber isotope.

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.

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.

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