Technical/Upgrading Activities
Following an analysis of Dukovany's Soviet-designed instrumentation and control (I&C) system, plant management recommended replacement with a Western-designed system. Siemens/KWU was awarded a contract in 1990 to supply a new I&C system. However, the CSFR government said in April 1992 that a study of I&C system replacement in VVER-440 Model V213 reactors would be carried out under the European Communities' PHARE program. The study found that extensive I&C refurbishing or replacement was needed at Dukovany, and a contract was signed with the U.K.'s NNC Ltd. in 1993 to provide full technical specification of the I&C system. The replacement itself will be funded by CEZ, which expects to complete the work before the year 2000.
Also under the PHARE program, NNC Ltd. is leading a consortium that will prepare the data packages needed to develop software for a simulator. Data packages for Dukovany, together with six other V213 reactors in five countries, were completed in mid-1995. The simulator is expected to be supplied by 1998.
Operational Safety
A major overhaul of Dukovany Unit 3, including a number of modifications to upgrade operational safety, was completed in 1992. Between 1994 and 1996, the plant evaluated the integrity of all of the units' primary circulation, steam, and feedwater piping. According to plant management, major upgrading of all four units, based on a probability safety assessment, is under way. The plant is also carrying out extensive reconstruction of electrical supply and distribution systems, replacing some equipment.
In addition, Dukovany's control room operators are writing more than 200 new operating procedures. Because the four units vary somewhat from one another, each unit will have its own documentation. Plant operators are writing the emergency operating procedures in cooperation with the U.S. firm Westinghouse.
CEZ, has bought some 400 unused fuel assemblies from the closed Greifswald plant in eastern Germany. About 200 of the assemblies will be used at Dukovany.
A Dukovany-specific maintenance database, which will be used to support the Dukovany probabilistic risk assessment effort, was developed and completed in March 1995. Using the database, plant staff can predict reactor system performance under various conditions.
A Level 2 probabilistic risk assessment has been completed for the Dukovany reactors. The purpose of the assessment was to study the effectiveness of the accident localization system under various off-normal conditions.
