Computerized monitoring system of residual cyclic life of WWER RP equipment

Computerized monitoring system of residual cyclic life of WWER RP equipment

The computerized monitoring system of residual cyclic life (SACOR-M) is intended for in-service calculation of cumulative fatigue damage of metal and fatigue extension of defects of WWER RP equipment by actual parameters of heat-andforce loads under real operation conditions. SACOR-M monitors the cumulative fatigue damage at the most stressed points of the structure selected by the results of design strength calculations. The loading parameters are calculated by the indications of standard transducers recording the current state of RP equipment. SACOR-M carries out the stress calculation by using the functional dependences of stresses on loading parameters for each check point. During RP operation the actual course of conditions can differ from that assumed in design strength calculations both by coolant parameters, and by the number of loading cycles. The monitoring of fatigue damage by the real loading of equipment is the urgent problem. SACOR-M main characteristics ÔÔ set of check points on the RP equipment is chosen in the scope sufficient for evaluation of RP residual life by the well-known mechanisms of fatigue damage; ÔÔ conservative models applied for the calculation of loading parameters allow to use the standard transducers that essentially reduces the labour input and dose commitments during SACOR installation and operation; ÔÔ use of Duamel s integral relation in the functional dependences of stresses on loading parameters permits to perform the calculation of stresses in check points directly at NPP; ÔÔ universal methods for determination of coefficients in the functional dependences of stresses on operation parameters permits to use the earlier strength calculations made at the stage of RP design justification; ÔÔ mathematical formula for stress determination permits to take into account all loading factors: weight, pressure, temperature compensation under the conditions of stratification and without it, non-uniformity of temperature field across the component caused by thermal shocks, thermal pulsations and stratification, off-design displacement of components; ÔÔ use of two mechanisms of metal degradation during evaluation of residual life (accumulation of fatigue damage and cyclic growth of initial unsoundness) permits to check the various limiting states; ÔÔ possibility for using the material property database both by certificates, and that obtained during in-service inspection of metal. The results of SACOR-M operation can be used ÔÔ during justification of residual life of RP equipment in case of a single design condition and off-design condition (for example, failure of BRU-A to seat); ÔÔ for optimization of the program of non-destructive testing of RP equipment for the purpose of reducing the period of preventive maintenance (for example, reduction in inspection scope of MCP welded joints); ÔÔ when exceeding the design number of conditions specified in the process specifications (for example, scheduled trips of RCP sets); ÔÔ for optimization of operational conditions and detection of unfavourable loading factors (for example, thermopulsations in the injection pipeline and the connecting pipeline during malfunction of low flow injection controller in PRZ); ÔÔ inspection of damages revealed during operation (for example, area of welded joint No. 111 of SG); ÔÔ when changing over to the daily load-follow mode of operation (automatic registration of cumulative fatigue damage under conditions of power variation); ÔÔ in case of extension of RP service life.

Design basis and verification of design formulas Stresses are calculated by using the functional dependences of stresses on the loading parameters, which are verified by the data of design strength calculations of components according to representative sequence of design conditions. The fatigue damage calculated by the method of rain (GOST 25.101-83) is chosen as a comparison criterion. Calculation Design Comparison of stresses by design calculations and by SACOR for check point on the reactor instrumentation nozzle Calculation of cumulative fatigue damage for current situation No. of standard transducer Check point of equipment Fatigue damage by SACOR as of 01.06.06 YA11 1 Hot leg: weld near MCP1 Dnom850 nozzle 0,010809 YA41 13 Joint of surge line into MCP4 hot leg 0,005440 Extract from the calculation log of cumulative fatigue damage YB10 2 Feed water nozzle of SG3 0,000583 YC00 10 Reactor vessel flange 0,025634 YC00 10 Convolved cycle YC00 10 Non-convolved cycle YC00 10 Total Diagram of accumulation of fatigue damage at check point of ECCS nozzle calculated by real loading for Rostov NPP, Unit 1

Computerized monitoring system of residual cyclic life of WWER RP equipment Calculation of extension of initial unsoundness and limiting states Repair of minor unsoundness in MCP welded joints is complicated in technology, expensive and its successful realization is out of guarantee. MCP could operate throughout design service life without repair. Method of calculated estimation of extension of initial defects is proposed as a compensating measure that will enable to optimize periodic nondestructive testing of the given welded joints. SACOR-M application experience at NPPs in operation Rostov NPP, Unit 1. SACOR-M has been put into operation at Rostov NPP, Unit 1, since November, 2001. It is installed in PC of the automated workstation (PC AWS) of SACOR-M system. SACOR software was developed for operational system Windows and certified at NTC YaRB GAN of Russia (certificate for software No. 161). SACOR, as applied to Rostov NPP, Unit 1, is introduced into project V-320. Power cut of Rostov NPP, Unit 1, from the grid took place on 07.11.2003 by the protection of generator with reactor scram and failure of BRU-A to close. SACOR-M was used for calculation of cumulative fatigue damage as a result of off-design condition. SG-1 was permitted to operate without instrumentation control of metal state by the results of analysis of accident condition scenario and calculation of fatigue damage. Tianwan NPP, Unit 1 (SACOR-428). SA- COR-428 involved in MCDS has been put into operation since November 2005, it is realized on actual data base obtained from Tianwan NPP standard transducers. SACOR-428 software is developed for operational system Unix (Solaris-8). The system made it possible to execute the on-line monitoring of temperature conditions throughout commissioning work of the reactor plant, to reveal local conditions of temperature pulsations, e.g. under off-design operation of regulator for water injection into pressurizer, to assess thermal stress level of the units and to optimize operation of the regulator. This condition recorded at Tianwan NPP, Unit 1, is shown in figure wherein constant temperature in PRZ (the upper line), pulsating temperature in surge pipeline near MCP ( grey line), pulsating temperature in injection pipeline (green line) and the lower red line temperature in MCP hot leg 4.

Computerized monitoring system of residual cyclic life of WWER RP equipment Equipment monitored and check points SACOR-M monitors RP equipment residual life in the following scope - reactor vessel and top head, SG, PRZ, MCP, pressurizing system and ECCS pipelines. Maximum design basis damage, welded joints with initial presence of defects, areas of cold coolant injection, damage areas as per operational feedback are assumed as the criteria for choosing check points. Figure shows a part of check points for assessment of SG fatigue damages. Their total number in V-320 RP equipment amounts to 118. Transfer of transducer indication data to SACOR-M server involved in MCDS In calculating loading factors by indications of standard transducers there are used immerse standard resistance thermometers, pressure pickups in the primary and secondary circuits, displacement transducers on shockabsorbers, indications of flowmeters, position indicators of the valves and surface resistance thermometers. NPP is possible to be additionally equipped with hardware components, placing of transducers and computer aids. TLS-U data collection Standard transducers and SG displacements ICIS transducers TLS-U top level system of the Unit, MCDS monitoring, control and diagnostics system, ICIS - in-core instrumentation system. ICIS server Rejection of error values SACOR-320 server (data sampling and calculation) Consideration of loading factors by indications of standard transducers In calculating stresses the following loading factors are taken into account: from weight, primary and secondary pressure, temperature compensation of pipelines under actual displacement of the equipment, thermal shocks, thermal pulsations and coolant stratification under all operating conditions. New position of MCP nozzle Integration of monitoring of SG actual displacements together with available SACOR-M aids makes it possible to diagnose the stressed state in the area of hot collector nozzle-to-sg vessel welded joint (area of welded joint No.111). Figure shows the example of calculation of displacement of MCP hot nozzle on SG vessel calculated by indications of displacement transducers on shock-absorbers.

21, Ordzhonikidze Street, 142103 Podolsk, Moscow region, Russian Federation Tel.: (495) 502-79-10, (4967) 54-25-16 Fax: (495) 715-97-83, (4967) 54-27-33 Http://www.gidropress.podolsk.ru Email: grpress@grpress.podolsk.ru The following references can be used for more detailed acquaintance with the issue: 1. N.V. Shary, V.P. Semishkin, V.A. Piminov, Yu.G. Dragunov, «Strength of main equipment and pipelines of WWER reactor plants» M.: IzdAT, 2004. Chapter 10. 2. Operating experience of system of the automated control of a residual cyclic resource for RP with WWER-1000. Bogachev A.V., Bakirov M.B. (VNIIAES), Dranchenko B.N., Semishkin V.P. (OKB Gidropress ). 18th International Conference on Structural Mechanics in Reactor Technology (SMiRT 18). Beijing, China, August 7-12, 2005. 3. Development of system SACOR-M. A.V. Bogachev, B.N. Dranchenko, V.P. Semishkin, V.Ya. Berkovitch. Issues of nuclear science and engineering. Series «NPP safety assurance». Scientific and technical collection. Issue 15. WWER reactor plants. Podolsk. 2006. 4. A.V. Bogachev. Lecture «Implementation of systems of calculated - experimental diagnostics of residual cyclic life of NPP equipment and pipelines». The 2-nd Russian interbranch school - seminar «Operational stability of nuclear power plant components». Collection of summaries of lectures, FSUE «NIIP», Lytkarino-2006. 5. V.P. Semishkin, A.V. Bogachev, B.N. Dranchenko. Calculations of RP equipment stressed state performed by using FEM within the framework of creating the computerized monitoring system of residual cyclic life for AES-2006. The 5-th International scientific and technical conference Safety assurance of NPP with WWER», Podolsk. May 29 June 1, 2007. 6. A.V. Bogachev, V.Ya. Berkovitch, B.N. Dranchenko, V.P. Semishkin. Determination of the loading factors for calculation of stresses by SACOR as applied to AES-2006 RP design. The 5-th International scientific and technical conference «Safety assurance of NPP with WWER», Podolsk. May 29 June 1, 2007.