Background

Vibration monitoring and diagnostic are based on identification, characterisation and monitoring of the frequency spectrum peaks corresponding to the structures and equipment vibratory modes. Because of the large size of the structures and equipments, vibratory peaks to be monitored were in the low frequency range. Taking into account that the existing AKNP (Ex-Core) and SVRK (In-Core) systems perform a permanent control and taking also into account the fact that the observed phenomena evolve slowly in time, the system to be installed will allow to monitor and assess the state of the structures and equipment on a periodical base (once a week). The possibility to increase this frequency in case of abnormal situation was foreseen.

The diagnostic system will be used to improve the NPP operation safety through early detection of the equipment defects and discovery of the deviations from equipment normal operation as well as through the confirmation of the mechanical integrity and strength of fastening of the reactor equipment including reactor internals and other primary equipment.

Objectives

The aim of the project was to equip KNPP Unit 2 with a diagnostic system allowing to detect abnormal situation inside of the reactor vessel.
The diagnostic system was intended to carry out monitoring/ diagnostic of the vibratory conditions/ behaviour of the reactor installation including the reactor with its internals and main circulating circuit. Monitoring is carried out to discover abnormal vibration conditions of the reactor installation equipment, as a result of appearance of defects in the reactor installation equipment, changing of its fixing conditions or increase of the dynamic hydraulic forces as a consequence of the influence of the primary coolant flow on the primary equipment.
System was designed to operate during all design modes of the power unit operation.

Project Results

The diagnostics system registered the following signals:
• Signals of the vibration displacement of the controlled reactor installation primary equipment.
• Pressure fluctuation signals.
• Alternative and constant components of the signals of the ionizing chambers.
• Alternative and constant components of the signals of the direct charge detectors and thermocouples.

The analysis of the measurement results and the issuance of the final diagnosis were performed automatically.

Monitoring was carried out automatically according to preliminary established algorithms. Measurements were executed in two frequency ranges, namely: 0.01-2 Hz and 1-100 Hz.

The system fulfilled diagnostics and issued an expert conclusion about the following phenomena:

1. Oscillations of the main primary equipment such as steam-generators, MCP, reactor vessel.
2. Vibration of the core barrel and reactor vessel.
3. Vibrations of the fuel assemblies.
4. Vibrations of the reactor internals which appear as a result of the existence of the coolant acoustic standing waves.
5. Value of the forces inducing a vibration (acoustic standing waves, dynamic hydraulic head of MCP).
6. Collisions of the reactor internals.
7. Boiling of the coolant.

The diagnostic system fulfilled noise assessment of the following parameters:

• Temperature and coolant pressure reactivity coefficients.
• Local and global axial unevenness of the field of the reactor core power release (offset).
• Assessment of the coolant flow rate through the core.
• Time constants of the thermocouples; efficiencies of the direct charge detectors and thermocouples.

Within the frame of present contract, the Supplier subcontracted part or all of following activities:

• development of the technical tasks and projects according to the needs;
• development, testing and validation of system’s diagnostic algorithms;
• preparation of instructions for installation, documentation and start-up of the system;
• training and translation activities.

Final versions of Technical Specification and Evaluation Criteria were approved on August 29, 2001.

Draft tender dossier has been sent to EC for approval mid of November, and the Procurement Agent, Italtrend, has sent a final version of the tender file on April 5, 2002 to EC for approval.

The publication of the tender file occurred in June with a deadline for the tenders on September 9, 2002. A clarification meeting was held at KNPP on July 25, 2002, with only one potential supplier. The evaluation session was held on September 16-20, 2002. Two bids were received and one has been proposed for awarding the contract. EC agreed on the conclusion of the evaluation committee and Italtrend started the contract negotiations.

A draft contract was received in February 2003 and commented, the issue related to the additional spare parts proposed by the evaluation committee was not yet settled.

The contract, including additional spare parts was signed by the Supplier on July 17, 2003. The kick-off meeting was organized at KNPP on September 11-12, 2003.Rosenergoatom and KNPP made complementary resources available in order to allow complete implementation of this project.

The supplier had foreseen the training of operation and maintenance teams of the End User.

Installation was planned in Spring of 2005, during outage of Unit 2.

The factory acceptance inspections and tests demonstrated that the monitoring system integrating all hardware and software met the set-up requirements. Factory acceptance tests were carried out at Contractor’s premises with Russian representatives involvement.

The site acceptance inspections and tests intended to verify that:

• the system, equipment and sensors were correctly installed;
• the system functioned 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 system during this period).

Definitive acceptance was pronounced 12 months after provisional acceptance (based on the condition of correct function of the system for 6 consecutive months).

Warranty period took place in-between provisional and definitive acceptance.