Process Control and Instrumentation Can Improve Efficiency

The Plutonium Facility (Pu Facility) at Los Alamos National Laboratory is the premiere facility in the nation for process-scale plutonium research and development. The projects and processes ongoing at this facility require a wide variety of instrumentation and electronic configurations. Frequently, systems require some type of computer control or monitoring, sometimes a complete process control system. Instrumentation- and wiring-related problems occur, especially as equipment ages.

The Nuclear Materials Technology Division has a Process Control and Instrumentation (PC&I) Team that addresses these issues for the entire Pu Facility. This team provides electronics and instrumentation support, a vital part of keeping the facility functional. This support includes supplying and ordering parts, hardware, and software, wiring, electronic design and fabrication work, panel construction, electrical and electromechanical drawings (including those required for the facility), making and installing feedthroughs and cables, and responding to a wide variety of troubleshooting and repair scenarios. A significant amount of this work requires our workers to be certified to perform work on energized systems. The team also provides advice on electronics, instrumentation, electrical systems, instrumentation, electrical safety, computers, and computer networking.

Nitric acid evaporators showing a process control screen in the foreground. The Process Control and Instrumentation Team provides a variety of computerized process-monitoring and control systems for this and various other projects.

The PC&I Team has developed a Windows NT computer network for the transfer of process and project data between the process facilities within the Plutonium Facility and the surrounding administrative buildings and has recently created an interface between this network and the popular Web browsers. The team provides a variety of computerized process-monitoring and control systems for various projects. The figure shows one such process, nitric acid evaporators, and the attendant process control screen. Data archival and tracking trends in real-time, along with the actual control of various aspects of a process, are very important because they usually lead to improved process efficiencies. These systems typically consist of programmable logic controller (PLC) hardware for data acquisition and control, software to program these controllers using "ladder logic" programming, human-machine interface (HMI) that provides the operators with an easy-to-use comprehensive interface to their sensors and process as a whole, and a personal computer that interfaces all the pieces of the control system together. The components are not the only important parts of a successful control system. Initially, what the customer wants in a control system must be interpreted and documented. In addition, the overall control system must be well documented for operators as well as for control system developers.

The following are examples of control system projects completed by the PC&I Team. A new furnace controller system has been developed for use in the Pu Facility. Furnace controllers are widely used for various operations that require heating of material or objects to high temperatures (e.g., 800°C). Historically, the Pu Facility has used a wide variety of furnace controllers. Some of these are old and are in frequent need of repair. There are also some newer furnace controllers, but unfortunately they are typically difficult to configure and operate.

The NMT-2 Process Control and Instrumentation Team developed this furnace control system to be easy to operate, flexible, reliable, and capable of modifications for specific applications. It allows for the control of up to 16 furnaces.

The first furnace controller system the team developed was a box that contained all the necessary components to carry out simple, semimanual furnace control. This system was much easier to configure and operate, and it was much more compact in size. The newer furnace control system (see photo at left) uses a combination of PLC hardware and HMI software to create an easy-to-operate, yet flexible furnace control system. The approach was to develop a generic, core-control system that will be usable for virtually every furnace control scenario at the facility. The system allows for the control of up to 16 furnaces and up to 16 temperature steps for each furnace. Furnace operation can be controlled unattended for more than four days. Application-specific needs and requirements can be incorporated in addition to the core system. Another example was a control system developed for nitric acid evaporators. This process distills nitric acid from a brine solution leaving a concentrated, contaminated salt residue. This control system also consists of PLC hardware and HMI software. For more efficient operations, a PID (proportional, integral, and derivative) control loop is utilized to ensure tight control of the liquid level within the evaporators automatically. Control of the level helps ensure higher-quality nitric acid distillate. Further, PLC ladder logic was written to prevent the abrupt "foaming-over" of bottoms solution into the clean overhead line. Foaming-over sometimes occurs when salts become excessively concentrated in the evaporator. When initial signs of foaming-over are detected the system shuts down automatically in an orderly fashion.

The PC&I Team also developed a control system for the facility's waste monitoring system. Liquid waste from the Pu Facility is sent to another facility for further processing once the radioactivity of the waste solutions is low enough. Gamma radiation levels are monitored in sanitary, industrial, acid, and caustic waste lines to help ensure a radioactive release does not occur. For the latter three waste lines, waste solution flow rates and temperatures are also acquired. Temperature- and flow-rate data are used to track the dates and times when solutions are dumped. Enough sensors are present also to help to determine where the waste originated within the Pu Facility. This system has networking/Internet browser capabilities systems (as do the previously mentioned control systems) that allow the various data to be tracked from another location within the Pu Facility or from one of the administrative buildings.

The PC&I Team has completed many other projects, and is currently working on several control systems: electrorefining, cementation, the new gamma monitors for the ion exchange process, nitric acid distillation, the hot bake oven, video monitoring of the Pu Facility basement, and the 40-mm launcher. As the mission of the Pu Facility evolves, the mission of the PC&I Team will also evolve to meet the facility's needs. This team is currently working on integrating process control operations, where appropriate. The future may also dictate that we increase our efforts in areas such as process automation and robotics, more advanced control strategies for better process optimization, and the development of a more-encompassing process database to better follow the intricacies and trends of process batches.

This article was contributed by Howard Nekimken, NMT-2.

NMT | LANL | DOE
Phone Book | Search | Help/Info

L O S  A L A M O S  N A T I O N A L   L A B O R A T O R Y
Operated by the University of California for the US Department of Energy