The South Ukraine nuclear station unit I became the first plant of its type to be backfitted with an advanced computerized operator information system. The new distributed control and information system installed on the VVER 1000 unit, is designed to improve plant safety by providing operators with detailed high resolution displays of operating conditions.
The safety of nuclear power plant in the former Soviet Union is often the subject of much debate. In an effort to bring the safety of these stations up to western standards, many of these have programmes for the installation of modern instrumentation and control (I&C) equipment. One project which has recently come to fruition, is the installation of an advanced computerized operator information system at the South Ukraine VVER 1000 Unit 1. The unit is believed to be the first operating VVER to have such a system installed.
The foundations for the project were laid in 1994 when Westinghouse was awarded a $5 million grant by the US Department of Defence for the first defence conversion project in the Ukraine under the Nunn-Lugar programme for the newly independent states of the former Soviet Union. This programme was essentially the result of an agreement between the US and the Ukraine to assist in the conversion of military-industrial enterprises to civilian activities.
The grant was used to help fund the startup of Westron, a joint venture between Westinghouse and the Ukrainian enterprise Hartron Production Association. Hartron is a major Ukrainian enterprise that formerly developed, produced and installed control systems for missiles and space systems. It is one of 26 Ukrainian firms identified as Nunn-Lugar programme defence conversion candidate companies.
Westron's aim is to initially focus on sup plying advanced instrumentation and control systems to 14 VVER units in the Ukraine. VVER nuclear power plants are pressurized water reactors, similar in design to western PWRs. However, the drawback with these plants at the moment, is that they lack the advanced control systems such as those required in the US and the rest of the western world.
The South Ukraine project, according to Westinghouse, marks the first full integration of western technology with Ukrainian engineering. The contract for the project was signed in February 1995 and the new equipment was shipped in July this year. The new system was installed during an annual refuelling outage and was put into operation in August. Hardware for the system was manufactured by the Westinghouse Process Control Division in Pittsburgh, Pennsylvania, and shipped to Kharkov where Westron engineers developed the software and performed extensive testing before delivering the final system to the plant.
The new system replaces an old centralized plant computer data acquisition system. This old system was basically a data acquisition system which only had the ability to print out paper records of historical events. This meant that it was difficult to compare trends in order to perform any trend analysis. Also, being a centralized system, it represented a possible single point of failure i. e. a system shut down could be caused by failure of this computer. Even with a back-up computer, data could still be lost since there would be a lag on start-up of the back-up computer.
The new system utilizes Westinghouse's WDPF II distributed control and information system technology. This system now provides operators with the ability to plot trends against each other on any desired time-scale or measurement parameter. This simplifies the process of making correlations so that operators can better understand the process.
Ultimately, safety is improved since parameters like temperature, pressure or flows can be easily seen in graphical form. In addition, being a distributed system, there is no single point of failure. In the event of a failure, this ensures there is a "bumpless" transfer without any loss of data.
The computer information system (CIS) now on-line is Phase 1 of the project. The CIS is essentially "the window into the plant" for the operations staff. It includes two redundant WDPF distributed processing units (DPUs) and a custom datalink called WestGate for data acquisition, a WEStation Engineers station, two WEStation Operators stations (one for reactor operations and the second for turbine and balance of plant operations). The delivery also includes redundant computational servers and redundant Historical Storage & Retrieval units (HSR) and Loggers (used to compile print reports).
A more detailed description of the CIS is as follows:
* Operators workstation - WEStations based on the Sun Microsystems Sparc 20 workstation. These provide the high resolution, multi-window environment for the man-machine interface to the I&C systems via colour graphics video display units. Control functions can also be performed via the VDU and keyboard/trackball.
* Computational servers - carry out most of the specialized calculations associated with the nuclear plant systems. All the programmes run on the Sun Microsystems computers which use the Unix operating system.
* Historical storage and retrieval - support the collection, storage and archiving of the plant data. This subsystem collects and stores the real-time data including pre- and post-trip data and the sequence of events during the trip occurrence.
* Data link server - provides the software required to communicate to from "outside" systems such as radiation monitoring and other computer based systems.
* Software and development stations - gives the software engineer the capability to perform software and system maintenance in addition to the ability to create and test software for the CIS.
* Log servers - primary and secondary log servers provide the ability to present data in a report format, either manually requested or event driven, and also provide the ability to capture hard copies of displayed screens.
All of these WDPF devices or "drops" reside on a redundant Westnet real-time data highway. All of the drops, with the exception of the DPUs, are also connected to a redundant ethernet information highway for passing of files and non real-time data between drops.
The Phase 1 configuration is designed to operate in parallel with the existing plant computer through the initial shake down operations. Phase 2 is scheduled for implementation next year, will expand the system with three additional operator stations and 20 additional DPUs for data acquisition. At that point, the old plant computer will be disconnected.
In addition to the standard operating system software included with WDPF, several additional application programmes will be installed at South Ukraine. These include:
* Time averaging: A routine that measures various operating parameters to develop trending data.
* Redundant measurements: A programme that monitors sensor readings and makes comparisons of actual readings versus expected readings and inferential data from other measurements to ascertain "health" or accuracy of key process instruments.
* Flow and level corrections: This programme supplies operators with corrections for tank level measurements based on actual pressure and temperature that compensate for "shrink and swell" effects.
* Plant and system status: Provides automatic adjustments to computer system parameters and notification routines based on actual plant status (i. e. full power, shut down, hot standby, refuelling etc.). This programme supports a "Technical & Economic Parameters" programme and a "Water Chemical Treatment" programme which coordinate actual plant status or mode with the plant technical specifications, efficiency models and water treatment requirements for that particular plant status.
The South Ukraine upgrade is the first of many that will take place in the former eastern bloc countries over the next several years. Westron is currently developing a similar system for the Zaporozhye nuclear power station which is scheduled for completion in 1997. There are nine other VVER 1000 units in operation in the Ukraine, as well six in Russia and two in Bulgaria-all potential upgrade projects.