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 …

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.

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.

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.