Ya.I.Shtrombakh. «Russian nuclear power plants life time management» Finnish Nuclear Society s seminar: "Nuclear Russia today and tomorrow"

Transcription

1 Ya.I.Shtrombakh «Russian nuclear power plants life time management» Finnish Nuclear Society s seminar: "Nuclear Russia today and tomorrow" Helsinki 2009

2 Main directions of RRC Kurchatov institute activities in Nuclear Power Area Strategic system researches for development of power engineering, nuclear power engineering and fueling; Advances in water-cooled shell-type nuclear reactors (VVER); Accompaniment of operating of high-power channel-type reactors (RBMK); Activities in the area of nuclear and radiation safety of atomic engineering; Decommissioning of nuclear plants and ecological rehabilitation of the territories. Problems of radiation monitoring of environment; Development of regional power engineering on the base of small and medium power reactors; Conceptual studies of innovative reactors and fuel cycles.

3 Kurchatov Institute is scientific leader in the part of radiation and nuclear safety in the following directions : Pressurised water reactors (VVER); Channel type power reactors (RBMK); High-temperature gas cooled reactors (HTGR); Water cooling transport nuclear reactors; Floating nuclear power plants (KLT-40); Space nuclear reactors; Reactors for regional energetics.

4 Functions of scientific leader. (together with Chief designer and General Projector): Research administration of projects; Accommodation of R&D program; Definition of general safety concept; Creation and justification of active zone, including thermohydraulics, thermomechanics, fuel cycles, state diagnostics, control and protection; Solution of issues of concern, which are not foreseen by regulatory system; Creation of technical means for beyond design basis accidents control; Creation and verification of calculation codes; Accommodation of requirements to water chemistry ; Providing start-up and driving up to the rated capacity of a new NPP Designer supervision.

5 Strategic milestones of atomic power energetics development (GW), BR-S 80 BN- small range 60 VVER-S 40 BN-800 VVER- VVER VVER-1000 VVER-440 RBMK

6 End of life limiting factors for Russian NPP s NPP RBMK VVER EOL limiting features gas gap closure material properties degradation graphite bricks cracking graphite columns bowing EOL limiting features RPV radiation embrittlement Additional problems: Thermal ageing Internals Piping Concrete

7 Nuclear power plants lifetime extension Main task state control and materials properties change prediction of permanent-set structures RBMK graphite stack; VVER reactor vessel. For accomplishment of this task required is representative system of permanent-set structures state monitoring; reliable physically justified models of main characteristics change, which define life of relevant structural elements, under the action of exploitation factors.

8 REACTOR MATERIALS TESTING Hot Box Line

9 NPPs with RBMK channel type reactors NPPs with RBMK channel type reactors produce half of total Nuclear Power in Russia. RRC "Kurchatov Institute scientific leader. Smolensk NPP Kursk NPP Leningrad NPP

10 Justification of work capability of nuclear reactors permanent-set structures 11 units with RBMK-type reactors produce half of all the electric energy, produced on Russian NPPs. NPP Number of power unit Date of Commissioning graphite 1 Leningradskaya Kurskaya Smolenskaya

11 Graphite stack Graphite stack, consisting of graphite bricks, is the permanent-set element of these reactors. In the process of reactor operation there take place thermal-radiation shrinkage of graphite bricks and enlargement of fuel channel diameter by means of irradiation creep.

12 RBMK External graphite ring Internal graphite ring Technological channel Graphite block Fragment of the fuel channel-graphite stack system Graphite block

13 LIFETIME CRITERIA OF GRAPHITE STACK CRITERIA Gas gap closure radial (hoop) shrinkage of graphite bricks; Critical value of neutron irradiation critical neutron fluence (F cr ). the criterion of the ultimate irradiation loading on graphite as a material; Ultimate value of vertical shrinkage of graphite columns (not more then 225 mm); Ultimate bowing of graphite columns (not more then 50 mm).

14 Graphite brick cracking and bowing of graphite column Graphite bricks longitudinal cracking resulting from arising irradiationthermal stresses, opening of longitudinal cracks and following bending of graphite columns. Calculations have shown that size of columns deflection shouldn t exceed 50 mm.

15 RBMK reactors graphite stacks lifetime prolongation After the assumed 30-year reactor operation commission inspection is executed that includes: measurement of cells geometrical parameters; sampling of trepans (cores) from 5 cells with different energy production along the whole height of graphite cells with diameter 10 mm and length 40 mm, and research of their physical-mechanical properties; execution of calculation of crack resistance of graphite bricks aimed at definition of time-point of their massive cracking. Subsequent to the results of research conclusion on the condition of graphite stack and its maximum lifetime is made.

16 CONCLUSION (RBMK) After the graphite stacks inspection, core graphite properties definition and stress-strain state of graphite stack definition conclusion on the condition of graphite stack and its maximum lifetime was made. At the present moment integrated survey of Units 1 and 2 of Leningrad NPP and Units 1 and 2 of Kursk NPP has been conducted. Subsequent to the results of conducted investigations a conclusion on working capacity of these reactors stacks within years has been made and permission of the Russian Rostekhnadzor for their exploitation continuation has been received.

17 Nuclear Power Plants with VVER reactors (PWR type) VVER reactors the basis of Russian Nuclear Power Industry. Totally 65 units have been put in operation. RRC "Kurchatov Institute scientific leader of all projects Tianwan NPP, China Balakovskaya NPP Kalinin NPP Kola NPP NPP-2006 new project

18 Three types of VVER units are in operation VVER-440/230 Generation 1 VVER RPV EOL basically depends on weld seam Radiation Embrittlement (RE) High P and Cu contents: Up to % P Up to 0.22 % Cu < 0.3 % Ni VVER-440/213 Up to % P RE depends on P and Cu contents Generation 2 VVER-1000 Low P and Cu contents: ~0.009 % P ~0.04 % Cu Up to 1.9 % Ni RE depends on Ni All units were annealed EOL depends on reirradiation EOL depends on the primary RE

19 VVER-440/230,179 reactor pressure vessel materials state evaluation

20 Radiation Embrittlement of the First Generation of VVER RPV Steels (VVER-440/179 and VVER-440/230) Unit Start Annealing Templet cutting Weld 4 P, % Cu, % NVNPP , , 1995, NVNPP , 1995, Kola Kola The absence of surveillance programs was compensated by taking templets

21 Templets irradiation in VVER-440/213 surveillance channels along with periodical RPV sampling has been accepted in Russia as RPV RE monitoring programs for VVER-440 units of the 1st generation Unit Start Annealing Templet cutting Designed EOL // 5 years PLEX license Weld 4 P, % Cu, % NVNPP , , 1995, NVNPP , 1995, Kola Kola The studies made within the last 10 years enables NPPs to extend the lifetime of annealed units for 15 years with licensing for each 5 years and RE monitoring using templets

22 Radiation Embrittlement of the VVER-440/213 RPV Steels Unit Kola-3 Kola-4 Start P, % Weld 4 Cu, % Ni, % <0.2 Tested surveillance sets The standard reference dependence specified in the Russian Guide for VVER-440 RPV welds is not conservative

23 VVER-1000 reactor pressure vessel materials state evaluation

24 International programs directions TACIS-94 and TACIS-96 - validation of neutron fluence three-dimension calculations (change of spectral indexes up to two times) - creation of Russian VVER-1000 surveillance specimens database TACIS-95 TACIS-96 - irradiation temperature and measurement and neutron dosimetry. It has been ascertained that irradiation temperature doesn t exceed 300. TACIS-96 - reconstruction method validation - validation of methods of fracture toughness determination.

25 TAREG-2000 Development of database on surveillance specimens, including revaluation of fluences and research results; Development of additional test technics, enabling to raise surveillance specimens program representativity; Development of new normative dependences on the basis of a representative database on VVER-1000 reactor vessel material irradiation embrittlement; Evaluation of VVER-1000 reactors vessels integrity, including reference units calculation.

26 The reconstitution technique enables to provide the representativeness of the VVER-1000 surveillance programmes 1 the fragment under reconstitution (insert); 2 corner tip; 3 joint made using method of pulsed arc welding.

27 Main results of international programs 1. Surveillance specimens programs are representative on irradiation temperature; 2. Use of three-dimension calculations enables to conduct correct evaluation of fluences on surveillance specimens using the - scanning of each specimen; 3. Implementation of reconstruction method enables to increase number of test specimens and provide representivity of VVER-1000 surveillance specimens programs; 4. Implementation of reconstruction method enables to produce new specimens for tests on crack resistance.

28 Additional problem of VVER-1000 surveillance specimens sets 4-6 single-store and are irradiated without advance compared to reactor vessel Unit Start P, % Weld 4 Cu, % Ni, % 1 Tested (withdrawn) sets BalakovoNPP-1 BalakovoNPP-2 BalakovoNPP-3 BalakovoNPP-4 KalininNPP-1 KalininNPP-2 NV NPP Double-store + + Single-store

29 Radiation embrittlement of VVER-1000 RPV welds increases with Ni contents

30 Application of modern calculation-experimental methods of neutron dosimetry is necessary for confident interpretation of results of surveillance specimens research and their transfer to a reactor vessel NEUTRON FLUENCE Proper definition of neutron fluence on surveillance specimens and reactor vessel is possible only via calculation-experimental method

31 Neutron dosimetry. Definition of neutrons fluence on surveillance specimens of VVER-1000 reactor vessels Experimental research of surveillance specimens: - Gamma scanning of each specimen in three points; - Measurement of neutron monitors; - Extraction of niobium from specimens and containers material Neutron calculations of surveillance specimens : -3D calculation model; - Specified network approximation of calculation model; - Pin by pin model for calculation of neutron sources. Calculation-experimental method of fast neutrons fluence definition on surveillance specimens of VVER-1000 reactor vessels

32 Neutron dosimetry. Monitoring and control of radiation resource of VVER-1000 reactor vessel Measurements outside reactor vessel VALIDATION Taking of the cladding samples from reactor vessel inner surface Neutron calculations Calculation-experimental definition of fast neutrons fluence on reactor vessel inner surface at lifetime extension

33 Specification of fast neutrons fluence on VVER-1000 reactor vessel wall is necessary to: Specify surveillance specimens advance coefficient; Reduce evaluation conservatism of reactor vessel radiation loading; Define reactor vessels service time limit with regard to lifetime extension. Activities: - Regular monitoring of radiation load on reactor vessel outer surface; - Sampling of cladding on reactor vessel inner surface.

34 Life time extension strategy for VVER-1000 Measurement range of Ni content in WM Service time extension? Radiation loading control to provide design service time and, possibly, annealing for service time extension Radiation loading control and pre-certification for service time extension Pre-certification for service time extension

35 REACTOR VESSEL STEEL OF Cr-Mo-V COMPOSITION WITH MODIFICATION OF FINE TEXTURE AT NANOSCALE - Provides high characteristics of steel strength, plasticity and ductility within the whole range of thickness, necessary for atomic reactors vessels ( mm); - Provides unprecedentedly high radiation stability of steel., Overload capacity Used steel of Cr-Ni-Mo-V composition EUR requirements: K = 30 C 0 New nanomodified steel of Cr-Mo-V composition -40 T 0 = -35 C years Service time, years

36 General conclusions Justification of exploitation safety of NPP permanent-set structures beyond design lifetime leads to necessity of: 1) development and implementation of principally novel means of their state control: cut out of small metal pieces (templates) from the internal surface of 1 st generation VVER reactors non-clad vessels; reampouling of single-store 4-6 sets of VVER-1000 surveillance specimens, and creation of novel, modernized surveillance specimens programs; drilling-out of specimens from graphite stack bricks. 2) implementation of a complex system of specification of irradiation loading on nuclear power plants elements, in particular, installation of dosimetric monitors system in off-vessel space. 3) conduction of additional research for justification of models of structural elements materials exploitation properties change beyond designed lifetime and introduction of relevant additions to accreditation reports for these materials, confirming possibility of the use of materials beyond previously defined maximal fluences and materials exploitation time.