1)Background
Russian VVER 1000 NPPs are equipped with horizontal steam generators (SG). In comparison to vertical SGs their water volume is larger. Therefore major water volume changes have a relatively low impact on the SG water level. On the other hand flow changes induce longitudinal waves of water/steam level which significantly perturb the water level measurement, and density differences in the steam/water area where the level is measured have direct influence on the measured water level. Therefore, the correct and precise measurement and control of the level is of high importance for proper NPP operation. Some unplanned shutdowns of the Unit 1 and 2 have been triggered by un-proper functioning of the level measurement in transient operational mode and as a result, the Main Coolant Pumps have been switched off. Besides loss of power production, the SG collectors are subject to hydro shocks in such situations. Therefore a this project was launched in order to improve the water level control system of the SGs.
2)Objectives
The main objective of this project was to modernise and improve the water level control system of the SGs in order to avoid unplanned shut downs and unnecessary loading and ageing of the SG collectors.
3)Project results–achievements
This OSA project included supply and installation of a new control system for optimising the feed water flow system from the feed water pumps to the SGs by replacing of the original feed water control valves and bypasses for both Units 1 and 2 in SUNPP.
The project started in June 1995 with the tender process, which finalised in June 1996 with the contract signature; this fact caused a delay of 1 year for the whole project. Since the project launching in August 1996, the design activities were in progress, as well as the corresponding manufacture activities. A licensing meeting took place in Madrid in April 1997 in order to get the position of the Ukrainian Safety Authority (NRA. During the meeting the available technical design documentation was reviewed. The NRA requested a 3N Qualification for the equipment. This request increased the demands and caused an increase in the budget. The EC did not accept the budget amendment, which caused a setback for the project. EC recommended the plant owner supplementing with own funds in order to have the project completed. At that moment 75% of the equipment had already been manufactured.
In a meeting held the 27th of May 1998 with the Task Manager the project was reviewed. It was decided to reduce the scope of the project, in order to fit it to the available budget. For this, some part of the equipment and the amendment requested for the general coordination were eliminated. It was also agreed to request necessary funds for the 3N qualification by a specific TOR under the new Tacis 96 programme. Considering the potential reactivation of the programme in a limited period of time, DTN continued with the implementation of the scheduled activities, in order to complete the foreseen planning and meet SUNPP’s expectations and needs.
The Procurement Agent (PA) prepared in January 1999 an Addendum to Supply Contract with the supplier Westinghouse Electric Europe, containing all the requirements stipulated by the NRA for higher qualification of the systems to be supplied (3N qualification). Finally, in December 1999, the Commission approved this Addendum No.1 to the Westinghouse contract, and after getting the approval of all involved parties, it was agreed to hold the Kick-off Meeting in March 2000 for the re-launching of the project.
Finally, in October 2000, the acceptance test of the feed water control valves and transmitters took place at SUNPP. At the same date, the control cabinets were received at SUNPP, and later on transported to their Facilities, in order to complete the equipment assembly. The final certification summary report was completed by Wese in December 2000 and the new passports were submitted in January 2001.
4)Comments
No information could be found in the archive of IE/JRC on how the project and especially the licensing of the new equipment was carried out.
Further Information
Further information on the project results could be sought from the beneficiary organizations.