[en] Investigatins into the welding of alloy 800 at the Reactor Fuel Element Laboratories, Springfields, commenced about three years ago following an extended development programme on tube to tube plate welding of low alloy and stainless steels for the Prototype Fast Reactor. The techniques and approach developed for critical fuel element welding applications had proved equally suitable for the precision welding requirements on the much heavier sections of heat exchangers. It had been demonstrated that the same control of weld quality and profile could be achieved with consistency and the permissible range of critical parameters could be readily defined. Because of this, development work was continued to include other materials, such as alloy 800, which might be of potential use. The tungsten inert gas (T.I.G.) arc welding process is used, and the equipment, including the control system, is described. Tube to tube-plate welding, and tube to tube butt welding, are discussed. (author)

[en] Welding investigations at Springfields are primarily concerned with development of jointing procedures for nuclear fuel elements, where high standards of integrity are required. Equipment and work which developed from a pulsed TIG-welding technique, set up in 1963 for welding of 0.4 mm thick tubing are described. A computer based control system, which is illustrated, can provide direct digital control of continuous or pulsed TIG or plasma welding. The work has been mainly concerned with stainless and low alloy steel between 0.4 and 4 mm thick. Some applications are mentioned. Tentative conclusions are drawn and it is felt that because of development at Springfields in continuous TIG-welding there is no advantage in using pulsed TIG on materials thinner than about 2 mm. (U.K.)

[en] The development at the Reactor Fuel Element Laboratories, UKAEA Springfields, of a computer-based welding process control system, was aimed initially at the TIG welding of the end seals of nuclear fuel elements. The system provides for mixed multi-station operation with on-line real-time capability and can be used either as a research tool or for production requirements at competitive costs. The operation of the control system, the form of power source and servo motor control units are described. Typically, continuous or pulse-arc welding sequences can be digitally programmed on 0.1 sec increments, with current in 0.5 A increments up to a maximum of 256 A; up to three servo motors can be operated with speeds selected in 0.1% increments of their maximum. Up to six welding parameters can be monitored digitally at speeds from once every 10 msec. Some applications are described and it is shown that the equipment has wider uses outside the nuclear fuel element field. High quality industrial welding requirements can also be met and the system is not limited to the TIG process. (author)

[en] This chapter deals with the control of arc welding processes considered as an integral part of overall quality control. A wide range of variables must be considered in order to ensure a satisfactory system and these are discussed. Methods of control are considered covering both open loop and closed loop systems. Practical working systems are shown to include elements of both types and requirements for adequate monitoring are specified. Examples of recent equipment and applications are outlined to show the current state of the art. These show the growing impact of electronic developments and the increasing use of computer techniques. Trends show that microprocessors will become essential components of any future control systems. (author)

[en] The design life of steam generator units for future LMFBRs is 30 years and one of the features governing long term performance is rubbing/fretting wear of tubes at spacer grids, resulting from shell side flow induced vibration of the tubes. The theoretical and experimental route adopted for the assess-ment of tube vibration and the determination of the tube support spans is described. The final design of a bundle is being endorsed for vibration behaviour by testwork on a full scale detailed replica of a sector of the bundle operating in water. Early results broadly support the theoretical predictions. (author)

[en] A systematic approach is described for selecting the correct joining processes for the special components which are required for the special performances demanded in the nuclear industry. The main factors are grouped under headings which include properties of the materials, features of the joints, equipment requirements, quality control, and in-service inspection. Each group is then considered in more detail. (U.K.)

[en] An extensive, two-year development program is now coming to a close. The basic process details necessary to obtain high integrity brazed joints for heat exchanger applications have been defined and are now being verified on a production basis by a leading UK Boilermaker. Replacement tube bundles are currently in manufacture and will be installed in the Prototype Fast Reactor at Dounreay in Scotland during 1981. The use of brazed joints in a sodium-heated steam generator may appear an exacting requirement. However, a comprehensive evaluation program has indicated that they will meet the stress and corrosion conditions anticipated in service. Confidence gained during the testing program has led to a further application at present under development. This is to exploit the technique in the repair of leaking tube-to-tube plate welds in current heat exchangers; the procedures being developed could have application to heat exchanger designs involving closely pitched smaller bore tubes

[en] Results of vibration tests carried out on the centre group of core sub-assemblies in the PFR during sodium commissioning are described. Signals were obtained at 1, 4 and 10Hz approximately with a total RMS amplitude of 0.005 in. This result is compared with measurements on a group of sub-assemblies and carrier in a water loop where a total amplitude of 0.002 in. was measured with dominant frequencies of 3, 5, 7 and 10Hz approximately using similar instrumentation. The 1Hz signal, which is dominant in the reactor has not been satisfactorily explained. (author)

[en] The development at the Reactor Fuel Element Laboratories, UKAEA Springfields, of a computer-based welding process control system, was aimed initially at the TIG welding of the end seals of nuclear fuel elements. The system provides for mixed multi-station operation with on-line real-time capability and can be used either as a research tool or for production requirements at competitive costs. The operation of the control system, the form of power source, and the servo motor control units are described. Typically, continuous or pulse-arc welding sequences can be digitally programmed on 0.1 sec increments, with current in 0.5 A increments up to a maximum of 256 A; up to three servo motors can be operated with speeds selected in 0.1 percent increments of their maximum. Up to six welding parameters can be monitored digitally at speeds from once every 10 msec. Some applications are described and it is shown that the equipment has wider uses outside the nuclear fuel element field. High quality industrial welding requirements can also be met and the system is not limited to the TIG process

[en] This paper summarises a study which has been carried out to determine whether a hydroelastic model using water can be built to reproduce realistically combined flow and acoustic induced vibration amplitudes. This problem, is examined in three parts. Firstly the driving forces are considered which are entirely a function of the fluid, and simple mathematical equations are derived which include the geometrical scale, velocity scale and frequency scale. These equations can be simultaneously satisfied and they determine the absolute values of the principal scales. For example the geometrical scale must be 0.392. Later in the paper the detailed effects of departing from these ideal values are considered. Secondly the structure is examined to see how it should be designed to have the correct resonant frequencies. This is most important because some of the driving forces are sinusoidal or narrow band random so that maximum vibration is critically dependent on the coincidence of driving frequency and structural resonance frequency. Thirdly the vibration amplitudes at resonance are checked. There is no freedom to adjust the design at this point since all aspects are determined by the previous arguments. (Auth.)