2. france guideline review step1 -fac mechanisms

8/19/2019 2. France Guideline Review Step1 -FAC Mechanisms

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Chapter 3

FAC Mechanisms,

Stressors and Operating conditions,FAC related ageing mechanisms,

Sites of Degradation

S. Trévin, Electricité de France (EDF) - France

G. Tomarov & A Shipkov, Geotherm EM – Russia


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Division Production Ingénierie Hydraulique - DTG

Chapter 3 – Understanding Flow Accelerated Corrosion

3.1 – FAC PROCESS

Effect of temperature

Effect of Chemistry

Oxygen

pH and chemical conditionning

Effect of hydrodynamic

fluid velocity

fitting geometry

void fraction and moisture

Effect of Alloy

2


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Division Production Ingénierie Hydraulique - DTG3

3.1 – FAC PROCESS

Chemical conditioning in liquid one phase flow to mitigate FAC

Under reducing feedwater

conditions AVT(R)

Under oxydative

feedwater conditions AVT(O)



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3.1 – FAC PROCESS

Chemical conditioning in two phase flow to mitigate FAC

Under reducing AVT(R) or oxydative AVT(O) feedwater conditions

Effect of pH on

Fe solubility



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3.1 – FAC PROCESS

3.1.1 Classification of wall thinning degradation

Flow Accelerated Corrosion (FAC)

General Corrosion

Cavitation Erosion (CavE)

Liquid Droplet Impingement (LDI)

Solid Particle Erosion

Steam or Liquid Erosion



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3.1 – FAC PROCESS

3.1.2 Affected Locations in NPPs • Feedwater lines;

• Condensate lines;

• Extraction lines;

• Discharge lines;

• Moisture separator and reheater drainage lines;

• Condensate drain lines and drain valves;

• Cold crossover lines from HP-turbine to reheater;

• Connection lines and nozzles on the feedwater tank;• Blow-down lines;

• Reactor water clean-up system

• Feeder tubes (CANDU);

• Heat exchangers such as the feed water heaters (shell, tube bundles), moisture

separator reheaters (shell, internal components and tube bundles), condensers;

• Vessels such as drain tanks;

• Turbines (if unalloyed or low-alloyed steels are exposed to wet steam flow).

• other areas ????



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3.1 – FAC PROCESS

3.1.2 Affected Locations in NPPs

Other Events Reports ???



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3.1 – FAC PROCESS

3.1.3 Material non-susceptible to FAC

J. Ducreux’s relationship:



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3.1 – FAC PROCESS

3.1.3 Material non-susceptible to FAC


•EPRI-guidelines

• systems made of stainless steel piping, or low-alloy steel piping with nominal

chromium content equal to or greater than 1.25% may be excluded from further

evaluation (with respect to FAC).

• If no significant wear is found during the first inspection, components with chromium

content greater than 0.10 % need not be re-inspected.

• AREVA states that FAC rate decreases starting with a threshold value of approximately

0.1% Cr. For steels with a chromium content of 2.1 % or more, FAC rates can be

considered negligible.

•For a long time, EDF considered 0.1 % Cr content in steel as a good protection against

FAC for 20 to 25 year old NPPs. In order to reach lifetimes up to 60 years, as is the case

for the Flamanville EPR, EDF has imposed 0.7 % Cr minimum requirement in the turbine

hall

•Geotherm EM recommendations …..


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3.2 – Stressors and operating conditions

3.2.1 Hydrodynamics

3.2.1.1 Fluid velocity


Mass lost per cm2 per hr

Reynolds’s number

F A C r a t e x d h / D

104

Temperature : 180°C

105 106 107

103

104

105

dh = 4mm

dh = 8mm

dh = 10mm

k = A.(e/dh)0.2.Re. Sc0.4.D/dh


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3.2.1 Hydrodynamics

3.2.1.2 Component geometry

3.2.1.3 Adjacent Element



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3.2.1 Hydrodynamics

3.2.1.4 Surface roughness

3.2.1.5 Steam Quality

To be re-write


Reynolds’s number

F A C

r a t e x d h / D

104

Temperature : 180°C

105 106 107

103

104

105

dh = 4mm

dh = 8mm

dh = 10mm

k = A.(e/dh)0.2.Re. Sc0.4.D/dh


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3.2.2 Environmental

3.2.2.1 Temperature

3.2.2.2 Water Chemistry

Oxygen effect (O2 concentration, Redox Potential)


Organization Range Adopted

Areva 40°C to 270°C

EDF 75°C to 300°C

EPRI 100°C to 250°C(no upper temp exclusion for single phase)

V = 35 m/s

P = 40 b

T = 200 h

[O2] < 40 µg/kg

< 1 µS/cm

Organization FAC Exclusion Range Adopted

Areva > 80 μg /kg in water phase for BWRs with neutral pH

EDF > 5 to 10 μg /kg, in water phase depending on flow velocity for

PWR with pH > 9.

EPRI > 1000 μg /kg (e.g. circulating water, service water, fire protection)


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3.2.2 Environmental

3.2.2.2 Water ChemistrypH effect (ammonia, amine, concentration)

Hydrazine concentration


Effect of pH on

Fe solubility


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3.4 – Sites of Degradation

3.4.1 Welds joints

local turbulencenon-steady state ?

alloying contents between

welds and pipes


-0.5

0

0.5

1

1.5

2

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475

Length (µm)

S i

&

M n

C o n t e n t s ( % )

0

0.04

0.08

0.12

0.16

C r c o n t e n t s ( % )

Mn Si Cr 140µm 190µm Pipe Material

Cr Average

= 0.148%

Weld Material

Cr Average

= 0.025%


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Division Production Ingénierie Hydraulique - DTG

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3.4 – Sites of Degradation

3.4.2 Entrance effect

3.4.2 Small Bore pipingdata are missing

Socket welded

Low risk


2. france guideline review step1 -fac mechanisms

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