Background
The feedwater control valves ensured, together with the variable speed feedwater pumps, the control of the feedwater flow to - and of the level in - the Steam Generators (SG’s).
The valves were driven by a control system which delivers a level/ flow demand signal that had to be translated into an equivalent position demand.
During transients affecting the NPP’s operation, these valves had to react (following the control system valve position demand) in order to keep the level in the SG’s between the normal operational limits allowing to avoid reactor trip signals.
Because these valves are important for normal operation of the plant they should be designed in such a way that:
• to be available as required
• no cavitation nor capacity limitation possible in the various plant operating conditions (normal, transient, incidental).

Objectives
The aim of this project was to equip a unit of KNPP with reliable Steam Generator feedwater control valves avoiding downstream cavitation phenomena.
Present project was intended for the basic supply of four main feedwater control valves intended to replace the motorised ones that were then installed at one unit of Kalinin NPP (VVER 1000 type NPPs - small series). The tenderer quoted as an option the supply of four additional main feedwater control valves for the second unit of Kalinin NPP.
In the frame of present project, the associated by-pass control valves were not intended to be replaced, but the characteristics (capacity, rangeability, stroke time) of the new main control valves to be proposed nevertheless allowed for any future options to be taken in case of further replacement or revamping of instrumentation, of control system or of any mechanical equipment associated with the Steam Generators feedwater supply system of the plant.
Project Results
The control valves (or their various constituting parts) were designed for a lifetime operation.
Per valve the supply included:
• The main equipment (control valve itself and its associated actuator).
• The packing with all protections for the transportation and long term storage.
• The accessories (position indicator)
The control valve and its components had to be operable and had to perform their functions on the following conditions:
- normal operation
- normal operation with seismic impacts up to maximal design earthquake
- breakdown of normal operation and in emergency situation
- environmental characteristics corresponding to the emergency conditions
The equipment was able to fulfil its functions during one year without interruption.
Final version of Technical Specifications for main feedwater control valves was issued in September 2001 and sent for approval on the Russian side. GAN approval was received on December17, 2001 with two comments, taken into account in the tender file. A new version 1 of the Evaluation Criteria was issued on February 23, 2001. Final approval was received from JRC on March 8, 2001.
The tender file issued by the Procurement Agent, Italtrend, was approved for publication in May, 2002 and evaluation was held on August 19, 2002. Three bids have been received, and the EC awarded the contract to the successful tenderer. The Procurement Agent prepared a contract for comments.
Contract was endorsed by EC on July 28, 2003 and was signed in Russia in December 2003 and by the Supplier on March 29, 2004. Installation was planned in 2005-2006.
The supplier ensured the necessary training of maintenance personnel of the End User.
Programme and procedure of acceptance tests was developed by the Supplier and approved by the Beneficiary and GAN RF. The programme of acceptance tests included the tests, confirming the calculated discharge characteristic or discharge coefficient and also the definition of the valve speed of response.
Each control valve of the delivery underwent approval tests according to a programme, which included the following tests:
- Strength and tightness tests of the parts and welds operating under fluid pressure;
- Leak-tightness in closing members of the valves;
- Quick action test;
- Other tests, stated in the programme of approval tests of the Supplier.
The approval tests were carried out at Supplier’s premises in the presence of the Beneficiary and the Gosatomnadzor RF representatives. The site acceptance inspections and tests were intended to verify that the valves function properly when connected to- and integrated in-existing Kalinin NPP systems.
Provisional acceptance occurred two months after acceptance at the NPP (following correct operation of the valves during this period).
Definitive acceptance was given 24 months after provisional acceptance (based on the condition that during this period the valves functioned correctly for 6 consecutive months).
Warranty period took place in-between provisional and definitive acceptance.