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1 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

2 Flow-induced material degradation Basics, Effects and Countermeasures The reproduction, transmission or use of this document or its contents is not permitted without express written authority. Offenders will be liable for damages. All rights, including rights created by patent grant or registration of a utility model or design, are reserved. Helmut Nopper Areva NP, NTCMM-G AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

3 Flow-induced material degradation - Content Introduction Flow-induced material degradation mechanism Flow-accelerated corrosion (Introduction, Corrosion process, Influence parameter) Cavitation erosion (Introduction, Mechanism, Risk determination) Droplet impingement erosion (Introduction, Mechanism, Sensebility) Prediction of risk Countermeasures (FAC program, Optimized water chemistry, Material concept, Repair technologies) AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 3

4 Flow-induced material degradation - Types, definitions, influencing parameters Introduction AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 4

Flow-induced material degradation - Types, definitions, influencing parameters Flow-Induced Material Degradation Single-Phase Flow ( Water ) Cavitation Erosion Definition: Deep localized degradation

5 Flow-induced material degradation - Types, definitions, influencing parameters Flow-Induced Material Degradation Single-Phase Flow ( Water ) Cavitation Erosion Definition: Deep localized degradation in pumps, but also downstream of internals and valves, caused by cavitation, i.e. violent collapse of steam bubbles in water flow near solid parts, governed by physical fluid and material properties Flow-Accelerated Corrosion Definition: Erosive destruction of oxide layers due to turbulent water or wet steam flow followed by corrosion and dissolution of the unprotected wall, leads to a coherent area of degradation, governed by thermalhydraulic properties, water chemistry, composition of material Steel FeOH Fe(OH) 2 Turbulent boundary layer Flow core Metal loss caused by erosion corrosion (mass transfer) Two-Phase Flow ( Water / Steam) Droplet Impingement Erosion Definition: Deep localized degradation due to the impact of liquid drops carried by wet steam flow, governed by physical fluid and material properties Droplets Flow Water film Area of high metal loss Droplet impingement Area of high metal loss Water streaks due to secondary flow AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 5

6 Flow-induced material degradation - Basics, effects and countermeasures Flow-accelerated corrosion (Erosion corrosion) AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 6

Flow-accelerated corrosion - Introduction (1) FAC is a chemical corrosion process assisted by fluid dynamic mechanisms FAC results in wall thinning from piping, vessels, and equipment made of carbon

7 Flow-accelerated corrosion - Introduction (1) FAC is a chemical corrosion process assisted by fluid dynamic mechanisms FAC results in wall thinning from piping, vessels, and equipment made of carbon steel FAC occurs only under certain conditions of flow, temperature, chemistry, geometry and material Unfortunately, those conditions are common in most of the high-energy piping in power plants. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 7

Consequently, FAC is a major issue for safety, reliability and costs Due to FAC four men were killed in 1986, two workers in

8 Flow-accelerated corrosion - Introduction (2) FAC is one of the most frequently experienced causes of component failures for power plants Undetected, FAC will cause leaks and ruptures without preceding leak before break indication. Consequently, FAC is a major issue for safety, reliability and costs Due to FAC four men were killed in 1986, two workers in 1995 and a failure in 2004 caused five fatalities. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 8

9 Flow-accelerated corrosion - Corrosion process (1) > A protective oxide layer is formed by the chemical reaction of the water flow at the inner piping material Magnetite Fe 3 O 4 (tri iron tetra oxide) oxidized Fe with water below 560 C, forms the thermo-solidly oxide Fe 3 O 4 3Fe + 4H 2 O Fe 3 O 4 + 4H 2 Hematite a, b, g - Fe 2 O 3 (di iron trioxide) - this occurs with O 2 under pressure 2Fe + 1 ½ O 2 a - Fe 2 O 3 - dehydration of Fe(OH) 2 at high temperature 2Fe(OH) 2 + ½ O 2 b - Fe 2 O 3 + 2H 2 O - or oxidation of Fe 3 O 4 to g - Fe 2 O 3 Base Metal Oxide Water Flow Fe 3 O 4 Fe 2 O 3 Oxide layer protects against erosion corrosion AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 9

10 Flow-accelerated corrosion - Corrosion process (2) > On carbon or low-alloyed steel the oxide layer is porous and Fe 2+ can diffuse into a stream of flowing water or water-steam mixture > The oxide layer becomes thinner and less protective against wall thinning > For Ni/Cr/Mo-Steels and stainless steels the layers are more protective as continuous oxide layers exist. This fact strongly limits the diffusion of ferrous ions through the pores of the oxide layer. > The hydrogen produced at the metal-oxide interface can diffuse into water or through the metal. Base Metal H 2 Oxide Water Flow Fe 3 O 4 H 2 Fe 2+ Oxide layer protects against erosion corrosion AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 10

11 Flow-accelerated corrosion - Corrosion process (3) > For a steady state process the Fe 3 O 4 dissolution rate must be equal to the Fe 3 O 4 growth rate. > The dissolution rate depends on the ph-value. > A further process is the mass transfer of the Fe 2+ - Ions into the water flow. The removal of ferrous ions strongly depends on how the water flow (velocity, local turbulence of flow) passes the oxide-water interface > Damage caused by FAC can be characterized as a general reduction of wall thickness rather than a local attack Base Metal Oxide H 2 H 2 Fe 2+ FeOH Fe(OH) 2 Water Flow Turbulent boundary layer Metal loss caused by erosion corrosion (mass transfer) Velocity profile Flow core AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 11

12 Flow-accelerated corrosion - Characterization Horse shoe pits in single phase flow Tiger striping in two-phase flows 100 µm AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 12

13 Flow-accelerated corrosion - Influencing parameters (1) Material Operation Chemistry Flow-induced material degradation AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 13

14 Flow-accelerated corrosion - Influencing parameters (2) > ph value (of the water flow) Wall thinning rate wall thinning is constant on a high level up to a value of 8.0 mm/a in the range between 8.0 and 9.0 wall thinning is reduced markable above a value of 9.0 thinning rates decrease drastically above a value of 9.7 FAC wall thinning can be neglected The ph has a significant impact on the solubility of magnetite. High ph values reduce the potential for chemical dissolution ph 25 C 14 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

15 Flow-accelerated corrosion - Influencing parameters (3) *Source: Heitmann and Kastner: Proceedings of the International Specilist s Meeting on FAC of Steels in High Temperature Water and Wet Steam The chart represents the specific material loss rate for different materials and flow conditions versus the ph value. These are experimental results from our Benson test facility in Erlangen. The curves for 13CrMo44 or 15Mo3 show that a strong diffusion of ferrous ions is not given due to a distinctive and more protective oxide layer. Note: Under two-phase conditions, the important parameter is the ph of the liquid phase, which can be different from the bulk ph due to partitioning of the species involved. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 15

16 Flow-accelerated corrosion - Influencing parameters (4) > Oxygen concentration mm/a Wall thinning rate highest thinning rates are observed below 10 ppb (parts per billions; µg/kg) in the range between 10 and 40 ppb wall thinning is reduced drastically above a value of 90 ppb wall thinning can be neglected The oxygen has a beneficial effect, as oxygen promotes the transformation of magnetite to hematite Oxygen concentration ppb AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 16

17 Flow-accelerated corrosion - Influencing parameters (5) X10 CrNiTi 18 9 G-X8 CrNiMo 12 X20 Cr CrMo 9 10 GS-18 CrMo CrMo CrMoNiV NiCrMoV 11 5 Austenitic stainless steels > Material (alloy content) Ferritic steels Coated steels highest wall thinning is observed with non-alloyed materials (carbon steel) increasing contents of chromium, copper and molybdenum decrease the thinning rates a chromium content of 2.5% reduces wall thinning drastically stainless steel is resistant against FAC St mm Metco 33 layer St mm Ni layer 15 NiCuMoNb 5 15 Mo 3 RSt 37.2 ph O ppb 9.5 < 5 ppb Material 0 max 7 < 5 ppb Wall thinning mm/a AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 17

18 Flow-accelerated corrosion - Influencing parameters (6) > Velocity of flow thinning rates are correlated to flow velocity mm/a Wall thinning rate highest wall thinning is observed at high flow velocities but wall thinning occurs already with low flow velocities The flow velocity influences the mass transfer between the metal surface and the fluid. The FAC rate increases proportionally with increasing flow velocity Flow velocity m/s 18 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

19 Flow-accelerated corrosion - Influencing parameters (7) > Temperature Wall thinning max below 40 C and above 260 C thinning rates are low mm/a highest thinning rates are observed at some 150 C The temperature affects the solubility the oxide layer. It also influences thermodynamic parameters, which have an impact on the mass transfer C 250 Water temperature 19 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

20 Flow-accelerated corrosion - Influencing parameters (8) > Geometry Wall thinning thinning rates are correlated to the local turbulence of the flow mm/a Valves Bends Orifice geometrical arrangement influences the local turbulence of the flow geometrical arrangements which induce high turbulence into the flow lead to higher thinning rates The geometry effect on FAC is caused by the local intensity of turbulence, which enhances the mass transfer between the oxide film and the water. 0.0 Pipe Geometry factor k c AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 20

21 Flow-accelerated corrosion - Influencing parameters (9) > Upstream flow effect (UFE) Piping element A geometry factor kc, A (kc, B)total = kc, B +Dkc, A (kc, B)total < 1.0 Geometry factor Piping element B geometry factor kc, B z / D AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

22 Flow-accelerated corrosion - Influencing parameters (10) > Flow type (water-steam flow) water-steam flow influences directly water chemical parameters because of the different distribution behaviour of alkalizing agents and oxygen flow type also influences local turbulence of the flow NH 3,steam distribution coefficient [ - ] bubbly flow stratified flow wavy flow slug flow annular flow NH 3,total O 2,total operating temperature [ C ] O 2,steam NH 3,water O 2,water AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 22

23 Flow-accelerated corrosion - Influencing parameters (11) Single-phase steam flow Drop flow Annular flow with water entrainment Slug flow Bubbly flow Single-phase flow - saturated - sub cooled Potential for droplet impingement erosion Combined effects possible AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 23 Potential for flow-accelerated corrosion Potential for cavitation erosion

increase of flow velocity due change in distribution of oxygen and / or alkalizing agent in the water phase Flashing

24 Flow-accelerated corrosion - Influencing parameters (12) > Flashing - effect on FAC Calculation of wall thinning taking into account the formation of vapor bubbles caused by flashing Cavitation Vapor bubbles form & collapse increase of flow velocity due change in distribution of oxygen and / or alkalizing agent in the water phase Flashing Vapor bubbles form & remain 24 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

Flow-accelerated corrosion - Influencing parameters (13) > Water chemistry ph

content molybdenum content > Thermal-hydraulics relevant velocity geometry

Exposure / operating time Operation Material Chemistry FAC AREVA NP > AREVA

25 Flow-accelerated corrosion - Influencing parameters (13) > Water chemistry ph value oxygen concentration > Material composition chromium content copper content molybdenum content > Thermal-hydraulics relevant velocity geometry and dimensions fluid temperature steam quality (void, flow pattern) > Exposure / operating time Operation Material Chemistry FAC AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 25

26 Flow-induced material degradation - Basics, effects and countermeasures Cavitation erosion AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 26

27 Cavitation Erosion - Introduction > Cavitation erosion is a commonly experienced problem in power plants, causing serious wear and damage. Under specific conditions, cavitation will reduce the components life time dramatically. > Cavitation may occur when the local static pressure in a fluid reaches a level below the vapor pressure of the liquid at the actual temperature. According to the Bernoulli Equation this may happen when the fluid accelerates e.g. in a control valve. The damage is not caused by vaporization itself, the damage rather occurs when the vapor spontaneously collapses at the inside wall of a pressure retaining structure. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 27

28 Cavitation erosion - Mechanism The degradation rate strongly depends on the intensity of jet formation. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 28

29 Cavitation erosion - Risk determination Temperature in C Depending on the expected severity of the jet formation and collapse intensity, the cavitation erosion model included with COMSY computes wall thinning rates for the individual material properties given. For determining the basic risk due to cavitation erosion, a multi-parameter model is used, considering specific flow conditions for the respective element. The above diagram indicates the intensity of jet formation. 29 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

30 Flow-induced material degradation - Basics, effects and countermeasures Droplet impingement erosion AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 30

Droplet impingement erosion - Introduction > Although all nuclear utilities have programs in place to protect against flow-accelerated corrosion (FAC), there has

impingement erosion > This degradation mechanism has caused wall loss, leaks, and ruptures and resulted in unplanned shutdowns in NPPs.

31 Droplet impingement erosion - Introduction > Although all nuclear utilities have programs in place to protect against flow-accelerated corrosion (FAC), there has been only little effort to protect nuclear piping from droplet erosion damage > One of the most common forms of erosion is liquid droplet impingement or droplet impingement erosion > This degradation mechanism has caused wall loss, leaks, and ruptures and resulted in unplanned shutdowns in NPPs. Repair and replacement of damaged piping and equipment have been a continuing expense AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 31

32 Droplet impingement erosion - Mechanism Droplet Droplets Droplet impingement Impact Radial flow Flow Water film Area of high metal loss Secondary flow in a bend Area of high metal loss Water streaks due to secondary flow Fracture in weak brittle metal Normal and shear forces Depression in ductile metal AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 32

33 Droplet impingement erosion - Sensibility annular flow wavy flow stratified flow bubbly flow slug flow COMSY utilizes the modified Taitel & Dukler flow chart to reliably compute the individual flow regime for given system operation conditions and geometries. The flow chart model was validated using Benson hydraulic test data. Droplet impingement erosion is found only for annular/droplet flow regimes. Unfortunately, these flow regimes are commonly found in NPPs (main steam, extraction lines, drainage lines, venting lines etc.) AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 33

34 34 Droplet impingement erosion - Influencing parameters (1) Wall thinning > Classic droplet impingement erosion is found only in the region of droplet flow > In the annular flow region an enhanced FAC wall thinning is induced by droplets Steam Quality AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

35 Droplet impingement erosion - Influencing parameters (2) > Degradation rates strongly correlate with flow velocity > Beyond a threshold value, the degradation rate is negligible AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 35 Wall thinning 0 20% 40% 60% 80% 100% Velocity Typical steam lines operation Drainage lines, pressure reduction systems

36 Droplet impingement erosion - Influencing parameters (3) AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 36 Wall thinning 0 Temperature Wall thinning 0 Pressure The degradation rate due to droplet impingement erosion increases with temperature and pressure and reaches a maximum at approx. 300 C / 85 bar.

37 Droplet impingement erosion - Influencing parameters (4) 0 The computation of wall thinning rates requires the knowledge of the specific material property strain work. In order to correctly resemble this parameter, a model which relates to commonly available parameters was developed. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 37 X5 CrNi Ck 45 GGG 40 St CrNiMo 6 34 CrNiMo 6 X22 CrNi CrMo 4 max. Wall thinning rate Material types Computed by COMSY Experimental results Material alloys and strength properties significantly influence the evolution of wall thinning.

38 Droplet impingement erosion - Influencing parameters (5) v VAPOR 220 m/s p = 3.75 bar T = C x = p = 20.8 bar T = C x = 0 The severity of wall thinning strongly depends on the individual system geometry. Specifically vulnerable to droplet impingement erosion attacks are bends, tee-fittings, pipes behind offices or behind throttling valves. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 38

39 Flow-induced material degradation - Basics, effects and countermeasures Prediction of risk AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 39

Flow-induced corrosion - history of FAC model development Benson test facility Water flow experiments FAC theoretical study and development of empirical model Water flow experiments DASY -

40 Flow-induced corrosion - history of FAC model development Benson test facility Water flow experiments FAC theoretical study and development of empirical model Water flow experiments DASY - development and application WATHEC - development and application COMSY Condition Oriented ageing and plant life Monitoring SYstem FAC-Model Update COMSY development and application AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 40

41 Flow-accelerated corrosion - Model validation / verification / optimization > Continuation of studies on FAC > Collection of FAC cases for validation / optimization of the prediction model in a database > Application of the model to BWRs (GE, ABB, KWU), PWRs (Westinghouse, KWU), VVERs and fossil-fired power plants (CCPP, coal-fired) worldwide FAC cases for validation Kastner model WATHEC V 2.0 WATHEC V 1.0 WATHEC V 3.0 COMSY V 1.0 COMSY V year AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 41

42 Flow-accelerated corrosion - Model validation / verification / optimization safety margin wall thinning rate predicted > Uncertainties on wall thinning computation are considered via a safety margin in order to ensure safe operation of element. > The computed wear is considered the maximum probable wall thinning rate for element under specified operating conditions. Hence, the corresponding recommended inspection date (RecUT) indicates the minimum life expectancy of the element. wall thinning rate measured >The safety margin is reduced after measurement results are available AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 42

Flow-accelerated corrosion - FAC prediction

43 Flow-accelerated corrosion - FAC prediction with COMSY Obviously, a specifically designed software tool shall be used to consider all affecting parameters with a reasonable effort. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 43

44 Flow-induced corrosion - COMSY characteristics > COMSY copes with the large number of parameters affecting flow-induced corrosion (FAC, droplet impingement erosion and cavitation erosion) as well as the complexity of their functional interdependencies. > COMSY allows the reliable identification of piping elements which may suffer material loss due to FIC, to calculate the minimum residual lifetime of piping elements affected by FIC to streamline inspection effort and to check countermeasures prior to their implementation. COMSY is a proven and ready-to-use tool with user interfaces in different languages and provides common materials and stress calculation for various countries AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 44

45 COMSY References Service Applications Software Licenses Philippsburg 1+2 Krümmel Isar 1+2 Brunsbüttel Biblis A+B Gundremmingen B Borssele Beznau 1 Gösgen Leibstadt Almaraz 1+2 Oskarshamn 3 Forsmark 1+2 Fukushima 2-1 Different fossil fired plants OL3 lifetime design services Chinshan 1 Spain : Asco 1+2 Almaraz 1+2 Cofrentes St. Maria de Garona Finland : Loviisa 1+2 Hungary : Paks 1 to 4 Bulgaria : Kozloduy 1 to 4 Ukraine : Khmelnitski 1+2 Rowno 1 to 4 Japan : Tomari 1+2 Brazil : Angra 1&2 Belgium: 8 fossil fired plants AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 45

46 Flow-induced material degradation - Basics, effects and countermeasures Countermeasures AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 46

47 Flow-induced material degradation - Countermeasures > The establishment and implementation of an effective plant FAC program (e.g. using of a software tool) > Optimizing the water chemical treatment > Apply improved material concepts for replaced components or lines and/or sufficient wall thickness margins > Apply qualified repair technologies (e.g. METCO spraying, sheet metal cladding) AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 47

48 Flow-induced material degradation - Effective plant FAC program The six parameters form the columns of an effective FAC program. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 48

49 Flow-induced material degradation - Optimized water chemistry (1) The ph value is one of the chief parameter affecting the FAC rate. To control the ph is important in that it provides a way of globally reducing the rate of FAC in power plants. High alkalizing levels reduce the FAC risk, but, are aggressive to copper. For copper based materials like e.g. brass tubing of condensers or feedwater heaters, a high ph values > 9.3 is not favorable, as it may accelerate wall thinning. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 49

50 Flow-induced material degradation - Optimized water chemistry (2) Influence of ph on solubility of base material AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 50 *Source: R. Freier, Aqueous Solutions Data for Inorganic and Organic Compounds, Vol.2 The solubility of ferrous ions strongly depends on the ph-value of the water phase. For High-AVT, that means a ph value of approx. 9.8, the solubility amounts to only mg/l.

ingress was reduced down to 1ppm after switching over from AVT water chemistry to High AVT treatment.

51 Flow-induced material degradation - Optimized water chemistry (3) Experience: solubility of Fe on ph Experience: KWU-PWR Obrigheim with High-AVT Average value 1 ppb The plot indicate, that the iron ingress was reduced down to 1ppm after switching over from AVT water chemistry to High AVT treatment. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 51

52 52 Flow-induced material degradation - Optimized water chemistry (4) Plant N: measured iron concentration dependence on the ph value in final feedwater 8 10, ph(nh3) Fe Fe filt. [ppb] 4 9,5 ph-value 2 Average value Average value: 0.6 0,6 ppb ppb 9 0 8,5 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia Jan 88 Sep 90 Jun 93 Mrz 96 Dez 98 Sep 01 Jun 04

53 53 Flow-induced material degradation - Optimized water chemistry (5) Plant E: measured iron concentration dependence on the ph value in final feedwater 20 10, ph(nh3) Fe Fe filt [ppb] 10 9,5 ph-value 5 Average value Average value: 1 ppb 1 ppb 9 0 8,5 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia Jan 76 Sep 78 Jun 81 Mrz 84 Dez 86 Sep 89 Jun 92 Mrz 95 Nov 97 Aug 00 Mai 03

54 Flow-induced material degradation - Material concept (1) The stability and solubility of the oxide layer is governed by the composition and amount of the alloying material (Cr, Mo, Cu) present. The most beneficial alloying element is chromium. For steels with a Cr-content of 2.1% or more, FAC rates can be considered negligible. 54 AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia

55 Flow-induced material degradation - Material concept (2) The results obtained from the AREVA BENSON test rig represent the effect of different steel compositions on FAC rate. AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 55

Flow-induced material degradation - Repair

Application range METCO spraying (2 layer)

Layer: Cr-Ni-Alloy Inner surface of turbine

56 Flow-induced material degradation - Repair technologies (1) Methode Welding material Application range METCO spraying (2 layer) ARC spraying (3 layer) undercoating: Ni-Al protective coating: Cr-Ni-Fe-Alloy 1. Layer: Ni-Al 2. Layer: Cr-Alloy 3. Layer: Cr-Ni-Alloy Inner surface of turbine casing, vessels, heater, large bore piping AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 56

57 Flow-induced material degradation - Repair technologies (2) Repair with METCO flame spraying AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 57

58 Flow-induced material degradation - Repair technologies (3) Repair with METCO flame spraying AREVA NP > AREVA NP GmbH < NTCMM-G, A. Nopper, Regional Workshop South America, December 2008 Argentinia 58

1. Scaling. H.O.: H-5/21, KRISHNA NAGAR, DELHI Tel.: , Fax:

1. Scaling. H.O.: H-5/21, KRISHNA NAGAR, DELHI Tel.: , Fax: Boiler Water Problems and Its Causes Water is the essential medium for steam generation. Conditioning it properly can increase the efficiency of boiler and as well as extend the boiler s life. Treating