SPECIFIC DEGRADATIONS OF VVER-1000

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1 SPECIFIC DEGRADATIONS OF VVER-1000 (in view of lifetime extension) Dimitar Popov Kozloduy NPP, Bulgaria IAEA Technical Meeting on Degradation of Primary Components of PW cooled NPPs, Vienna, Nov, 2013

2 CONTENTS Introduction General info for KNPP and WWER-1000 Assessment of cyclic loading status of main primary equipment: - Pressurizer - Steam Generators - Main Coolant Pipelines - Connection pipelines Assessment of Main Coolant Pumps status Conclusion 2

3 Introduction Kozloduy NPP is situated on south bank of river Danube It is the main electricity producer in Bulgaria It has a significant importance for the country and the region 3

4 Introduction (cont d) : Units 1 & 4 - VVER-440/230 Pressurized Water Reactors, standard first generation Russian design Decommissioning 1987 & 1991: Commissioning of Units 5 & 6 respectively- VVER-1000/B320. Design Lifetime 30y, expires in 2017 and 2019 resp. Pressurized Water Reactors, standard second generation Russian design Major modernizations in the design made to improve the reliability of main mechanical, electrical and I&C equipment. 4 4

5 General Information for Unit 5, 6 Four Loops, VVER-1000/B320, Output 1000 MWte Primary pressure 15.7 MPa Inlet/Outlet Core Temperature 289/318 C Secondary Steam Generation 4x1470=5880 t/h Secondary Side Pressure 6.4MPa 5 5

6 General Information for Unit 5, 6 - Safety systems YT12P05 60 YT12B01 YT11P05 60 YT11B01 YC00B01 YB30YB40 YB20 YB10W01 YD10D01 Active part include 3 (three) Independent Channels; Every Channel equipped with sub-channels Emergency DG HP H 3 BO 3 TQ14F02 6 TQ14L01 TQ13F TQ14 TQ13 TQ13L TQ12F TQ11F TQ12 TQ11 TQ10B01 TQ10T01 25 TQ10S01 TX10B01 TX10F HP ECCS LP ECCS SS injection into containment SG EFW UT10P03 GV01UW1 BV TQ13S26 35 TQ10T02 VF VF40F01 20 VF40T01 Passive part include 4 HA (hydro accumulators) 6 6

7 General Information for Unit 5, 6 - Containment Containment 0,5MPa, 150 C; m 3 free volume 23 PARs Filtered Vent System 7

8 The analyses of calculations performed during PLEX investigation for Unit 1 of Balakovo NPP, which is identical to Unit 5 of NPP Kozloduy, have shown that the main contribution in fatigue damage of different Primary components are the cycles formed by the operational warming-up and cooling-down modes, and also modes characteristic for the considered nodes in which there is a sharp cool-down (e.g. nozzles, inserts etc). 8

9 Table 1 Primary equipment and pipes under cyclic loading (cont d) Mode Design lifetime number of cycles Factual number of cycles at Unit 1 of BNPP Factual number of cycles at Unit 5 of KNPP Calculated number of cycles for 60 years operation 1 Normal operation modes 1.2 Hydro tests: -Primary -Secondary: 1.3 Toughness (permeability) tests: -Primary -Secondary: 1.4 Planned warming up at rate 20 С/h SCRAM Planned tests of Prz Safety valves: - YP21 S01 - YP22S01 -YP23S01 According to TecSpecs

10 (cont d) Table 1 - cont d Design lifetime Factual number of Factual number of Calculated number of Mode number of cycles at Unit 1 of cycles at Unit 5 of cycles for 60 years cycles BNPP KNPP operation 1.11 Hydro-accumulators tests: - HA 1 - HA 2 - HA 3 - HA Planned warming up at rate 30 С/h 2 Normal operation violation modes 2.1 Closing of Turbine stop valves Loss of off-site power Loss of feed water for Steam Generators ( for each SG) :

11 (cont d) Mode 3.Emergency modes (only the differences between two units) 3.1. Opening and not closing of SG safety valve 3.2. Opening and not closing of BRU-A (SG steam dump to atmosphere) 3.3. Opening and not closing of BRU-K (steam dump to condenser) Design lifetime number of cycles Factual number of cycles at Unit 1 of BNPP Factual number of cycles at Unit 5 of KNPP Calculated number of cycles for 60 years operation * ** * for each BRU-A ** for each BRU-K 11

12 (cont d) The analysis of the data presented in Table 1, shows: no on one of design modes on the Unit No. 5 of NPP Kozloduy there was no excess in comparison with the provided ones in the Design; on the Unit No. 5 of NPP Kozloduy there was no emergency modes; the quantity of last warming up-cooling down modes makes about a half, from the quantity provided in the Design taking into account number of cooling-downs with a rate of 60 C/h; the quantity of last modes with violation of normal service conditions in which there can be a local cooling down of the nodes, also makes less than a half, provided in the Design; 12

13 (models of pipelines) To define tensions in Main Coolant Pipelines (MCP) ASTRA-AES'2009 code was used Models were built - examples - Main coolant pipeline; - Relief pipeline; - Spray pipeline 13

Models were built to define temperature fields and

14 (equipment models) ANSYS code has been used to define tensions in the equipment nodes and in the inserts of Main Coolant Pumps Models were built to define temperature fields and tensiondeformation status of equipment Example: SG and its Primary collector 14

(fatigue calculation of Prz) 0, 484 0,548 0,350 Definition of the Calculated fatigue accumulated fatigue of different parts of damage to equipment Prz nodes, as well as in

15 (fatigue calculation of Prz) 0, 484 0,548 0,350 Definition of the Calculated fatigue accumulated fatigue of different parts of damage to equipment Prz nodes, as well as in pipelines, is carried out according to provisions and recommendations of PNAEG Some examples of the calculated fatigue in different equipment is given 0,571 0,

16 (fatigue calculation of important pipes) 0,10 Calculated fatigue of different parts Prz spray line 0,09 0,04 0,05 0,06 0,05 16

17 (fatigue calculation of important pipes) 0,05 0,04 0,03 0,04 Calculated accumulated fatigue of different parts of the relief line 17

18 (fatigue calculation of important pipes) 0,19 Calculated accumulated fatigue of different parts of the surge pipeline of Prz 0,46 0,37 0,06 18

the Primary Pipeline (4 th Hot Leg) 0, 045 Calculated

19 (fatigue calculation of inserts) 0,486 Calculated accumulated fatigue of the insert of the nozzle of Prz surge line into the Primary Pipeline (4 th Hot Leg) 0, 045 Calculated accumulated fatigue of the insert of the nozzle of Prz spray pipeline 19

Circuit 0, 287 0, 373 Calculated accumulated fatigue of the

20 (fatigue calculation of inserts) Calculated accumulated fatigue of the insert of the nozzle of make-up pipeline to the Primary Circuit 0, 287 0, 373 Calculated accumulated fatigue of the insert of the nozzle of ECCS low pressure pipeline to the Primary Circuit 20

21 (fatigue calculation of SG) Calculated accumulated fatigue of different parts of`sg 0,008 0,048 0,058 0,05 0,076 21

22 (fatigue calculation of SG) 0, 170 Calculated accumulated fatigue of different parts of`sg 0, 160 Section A-A of the figure on previous slide 0, 365 0, 104 0,

metal Anticorrosive layer Welds Base metal Anticorrosive layer Welds Base metal Welds Anticorrosive layer Welds Base

23 Assessment of Main Coolant Pump Status model on ANSYS A Strains on the main sealing; B forces by the studs; C,D reactions to the pressure and tensions by the MC Pipelines; F forces from hangers Aging Mechanisms Component Welds Base metal Anticorrosive layer Welds Base metal Anticorrosive layer Welds Base metal Welds Anticorrosive layer Welds Base metal Anticorrosive layer Aging mechanism Thermal aging Fatigue Stress corrosion Inter-crystallyne corrosion Plastic deformation 23

24 Assessment of Main Coolant Pump Status cont d Results from the strength calculation Warming up Cool down Fatigue damage of MCP corpus, except main sealing Hydro-tests Normal operation modes Violation of normal operation modes Accident modes Accumulated usage factor Cycles for 30y 0,0001 0,0012 0,0188 0,0097 0,1011 0,13 Cycles for 60 y 0,0002 0,0023 0,0418 0,0305 0,2022 0,28 Tightening Warming up Cool down Hydro-tests Fatigue damage of sealing Normal operation modes Violation of normal operation modes Accident modes Accumulated usage factor Cycles for 30y 0,615 0,311 0,033/0,230 0,071 0,048 0,031 0,94 Cycles for 60 y 1,281 0,648 0,063/0,459 0,071 0,152 0,062 2,74 24

25 Assessment of Main Coolant Pump Status cont d Conclusion on MCP: The main sealing of MCP should be moved to another place, what is approved technology yet А Сигма, Па 25

26 Conclusion on cyclic loading status of Primary equipment From the presented results it is visible that the accumulated fatigue damage to the considered equipment and pipelines of reactor installation doesn't exceed the allowed value according to the normative on accepted life extension till 60 years in view of quantity of cycles for different modes. Thus the maximum fatigue damage for the considered units of equipment and pipelines is equal to: Prz: amax= 0,713; Prz pipelines: - surge line: amax= 0,460; - spray line: amax= 0,100; - relief line: amax= 0,050; Relief tank: amax= 0,021; Hydro Accumulators: amax= 0,046; HA hot pipeline: amax= 0,120; Main Coolant Pipelines: amax= 0,142; Steam Generators: amax= 0,365; Inserts of nozzles into the Primary : - nozzle of Prz surge line : amax= 0,486; - nozzle of Prz spray line: amax= 0,045; - nozzles of make-up line: amax= 0,287; - nozzles of ECCS LP pipeline: amax= 0,287 CONCLUSION: POSITIVE RESULTS FROM CALCULATIONS ON THE CYCLIC LOADING GIVE THE GROUNDS TO ASSUME THAT LIFETIME EXTENSION OF UNIT NO. 5 OF NPP KOZLODUY TILL 60 YEARS IS POSSIBLE. 26

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