ML15334A200
| ML15334A200 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 11/18/2008 |
| From: | Riverkeeper |
| To: | Atomic Safety and Licensing Board Panel |
| SECY RAS | |
| References | |
| RAS 27919, ASLBP 07-858-03-LR-BD01, 50-247-LR, 50-286-LR | |
| Download: ML15334A200 (80) | |
Text
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aterial Aging lnstitu International Conference on Plants aterials Dearadations i
RIV000149 Date Submitted: June 9, 2015 United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of:
Entergy Nuclear Operations, Inc.
(Indian Point Nuclear Generating Units 2 and 3)
ASLBP #: 07-858-03-LR-BD01 Docket #: 05000247 l 05000286 Exhibit #:
Identified:
Admitted:
Withdrawn:
Rejected:
Stricken:
Other:
RIV000149-00-BD01 11/5/2015 11/5/2015
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- I jecti A poor chemistry may, on a rather long term, induce corrosion The effect is detrimental for components Adequate Chemistry 1 of the Circuits Long term availability of Units Safety of the plant lncreas Minimum of incidents
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The NPP strategy is adding new challenges to the most crucial previous weakness of Alloy lnconel 600:
SCC (Stress Corrosion Cracking).
~ Optimization of the primary water chemistry for dose rates minimization and high performance fuel operation (PWR and BWR).
~ Economical, environmentally sustainable and reliable operation of the circuits
~ Very high safety and availability levels of the NPP rm r
po r
I n r I i
II
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- 1970s: Major ingresses of sea water, oil, ion exchange resins, etc. caused corrosion and fuel problems.
Impurities contributed to IGSCC of BWR piping.
Phosphate dosing of PWR steam generators caused wastage or IGA/SCC, leading to "all-volatile treatment" in 1974, which caused denting.
- 1980s: "Purer is Better" was the theme-it helped a lot but was not sufficient to eliminate problems in presence of Alloy 600.
- 1990s: BWR hydrogen water chemistry, zinc injection, pH control in PWR primary and secondary systems for FAC and SCC
- 2000s: Noble metal chemical addition in BWRs, PWR primary zinc injection, elevated pH or amine in most secondary systems of PWR for SG deposits and FAC mitigation, dispersants trial.
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CJl Fuel Performance and behavior SG tubes: IGA/SCC, pitting, denting,...
Condenser tubes degradation
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Fuel Performance and behavior Reactor components 304 steel : sec Condenser tubes dearadation
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- PWSCC, fuel behavior
- Amine, ammonia, corrosion inhibitors
- Copper alloys corrosion
- IGA/SCC (mainly lnconel 600 MA), low Accelerated orrosion of carbon steel, corrosion products deposition and low Induced ibration
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..... I Objective :
Neutralization of Boric acid in order to be in a slightly alkaline environment Optimum pH Low generalized corrosion
- minimize generation and transport of corrosion products
- minimize dose rates I Alkaline reagent selection I
- NaOH => 24Na
- KOH
=> 42K Acceptable, used in VVER
- NH40H low stability
- n '
- Low corrosion risk due to limited solubility and concentration Li-7 also produced from boron neutronic reaction 108 (n, a)?Li I
Radiochemistry I
Li natural :
6Li :
7.42 °/o 7Li : 92.58 °/o 6
3Li + 1 0n => 4 2 He + 3 1 H (tritium) 6Li (n, a) T
=> use of 7Li enriched to 99.9 o/o
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(J) 3 main questions for Primary Water Chemistry options (I
)
- Dose rates,
- CIPS (AOA) 41 (I *
- Dose rates
- CIPS (AOA)
)
i/Dose rates,
- CIPS (AOA),
- Safety, design
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Typical pH 300oc range 7.2 to 7.4
- BOC, 1""""-ll"l.il"!>l 1n
- Dose rate Impact, Target pH has been progressively increased in many cases, (calculation codes, feedback)
Limited impact within this range
- risk of Cl PS
- But more impact if pH too low Boron-Li precipitation, other factors (Ni)
- K (VVER) versus Li difference,
- Compromise with 7Li cost (load follow, transients, shutdown) under investigation (IAEA/FUWAC)
PWR: Typical Li max= 2.2 or 3.5 ppm Some cases with even higher values No benefit expected for PWSCC, but potentially for dosimetry
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- 2 71
)
""'"~"'~
least 3.5 oom Typical Li max= 2.2 or 3.5 ppm, some cases higher No benefit of higher value expected for PWSCC, but potentially for dosimetry
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- Subcooled nucleate boiling and associated crud deposits
- Boron content + Li Impact of new fuel options, longer fuel cycles ~ Higher B at BOC Boron precipitation in crud.
- pH influence on corrosion product transport, deposition, crud thickness
=>
I i
- Nickel content in Materials lnconel 600 the worse. 690 better.
lncoloy 800 (Germany) satisfying 18-1 0 (WER) the best.
- Optimum pH with limited B
- ? Li also limited
- May avoid design modification
- Highly advisable to consider for new plants
- *u*in r i although more beneficial relative to zircaloy corrosion and ~ B in crud
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4,0 I Lim ax = 3.5 ppm I:
3,5 3,0 2,5
~2,0
- .J 1,5 1,0 0,5 0,0 1800 1600 1400 Under itnplementation on 4 EDF
-I-------- -------
-~---------I--------
pH 3oooc target= 7.2 target= 7.0 I
I
1--------~-----
________ l ________ j _______ _
I I
________ l ________ j _______ _
I I
1200 1000 800 600 400 200 Boron (ppm) 450Me Alcade) 0
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~60 c ro 0:::
-~50
..c
+-'
maximum
~ 40
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full power
~
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equilibrated
())
lithium 0>
~ 20 c
())
()
I....
()) 10 0...
0 2000 2001 2002 2003 2004 2005 2006 2007 EOC Year I
<3 ppm
- 3.0-3.5 ppm D >3.5 ppm I
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- This is of potential interest in a few cases Y Postponing or avoiding SG Replacement in presence 600 TT Y Mitigating SCC of components lnconel 600 other than SG tubing
- Dose rate limitation:
lower content 0..
More and more used, Inhibiting Co incorporation in corrosion products. Potential interactions to be considered
- Usually depleted Zinc added
- Easy method
- Limited associated risk for the fuel due to low Zn
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.. I WeibullFit (Least Squares) 90
% ~
I I
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I I I II
~~~ r::-:_-- =--::-:_-- r-::-:_--t-t-l =t:_-l j_:t j ~
20%
fl
~
10%b---------r---~--~--~~--~-+~------~~----~L_~--r-+-~4-+-
~
5%
~
~
2%
~
1 Zinc
-~
0.5%
1 °.2%
-+
-~- t-1-1 to= 0.00 EFPY ~
0°0::
b:~0.90:--I---~--
0.02%
o.o1% f-~~~~r-~~--,----i~~~--,--j--rl--rtrl-~~~H~--~4-~4-~h--h-+-c-h+,-j 3
4 5
6 8
10 20 30 40 50 60 80 100 Service Time (EDY@ 607°F)
Cumulative % of failed tube versus time with or without 35 ppb Zinc.
I (
Zinc Impact on PWSCC What is the impact of zinc injection on PWSCC initiation and crack growth rate(s).
1 US Utility has experienced a 79% reduction in the Weibull Slope with a target zinc level of 35 ppb.
A comprehensive EPRI review of US plants consistently demonstrated a significant benefit of zinc Reduced crack growth benefit of zinc shown for A600 SG tubes does not necessarily transfer to thick-wall RCS components and to A82/182 welds
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<D Laboratory tests not all in agreement.
Higher influence on lnconel 600 crack propagation than initiation
- Elimination duration at shutdown
- Gaseous wastes e.g. Factor 2 from 20 to 5 cc EPRI: either low or high but large scatter, limited impact
- Risk of radiolysis 5 ml/kg sufficient, always achieved 4D l!ooii!'IC::M"'
r-nrrnc;:
n See belOW
- Low value control low pressure difficult to keep constant
- Start to decrease before shutdown I PWSCC Propagation I Sweden : select either low < 1 0 cc or High > 30 cc (low impact)
EPRI: would need <5 impractical thus higher H2 is better
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0 1----**
- Zinc is Beneficial
-Increases PWSCC initiation time, but beneficial effect on crack growth rates is uncertain
- May need to remove hydrogen sooner in shut down process D Going to lower hydrogen may increase crack propagation at lower RCS temperatures (e.g. 290°C)
D Operation at low hydrogen increases the risk of going to oxidizing conditions in the event of a plant transient, e.g. loss of letdown flow.
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Ill I Corrosion Potential, mVshe
-700
-750
-800
-850
-900 9
~
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I I
I I
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I I
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Peak in Growth Rate= 8X as Expected for Alloy 82/182 Change in CGR for various step changes in Hz Hz change 600 82/182 10 ~ 20:
1.24X 1.34X 8
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2 Schematic Plot of Effect of H2 on Crack Growth Rate For 325C where potential,J...
by 59.35 mV per 10X 1' in H2
& 118.7 mV per unit 1' in pH 50 mV Full Width Half Max Peak in Growth Rate = 3X as Expected for Alloy 600 20 ~ 40:
1.61X 2.17X 40 ~ 80:
1.38X 2.11X 20 ~ 80:
2.23X 4.58X 20 ~ 200: 2.42X 5.93X 10 ~ 200: 2.99X 7.97X 0 +-----~--~--~~~~~------~--~~~~~~~----~--~~~~~~~----~--~--~~~~~
0 1
10 100 1000 Hz Fugacity, cc/kg
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I'V 600,690 High ooco All High Co I Zinc Enriched Boric Acid All ICIPS, AOA I Limited B, Li K instead Li 18-10Ti 1 Pitting, sec Avoid Cl Resins H2 instead NH3 Remedies will partially depend on the design, materials No highly efficient option for inappropriate material IN600 (600 MA or 600 TT in presence of high stress level)
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~ Keep long term integrity of components
~ Insure operation in good conditions for safety, availability, costs and maintenance The challenges include
- Avoiding ammoniacal corrosion of Cu alloys
- Mitigating IGA/SCC of Alloy 600 SG tubing
- Lowering fouling of SG tubing, heat transfer, flow
- Decreasing operating and maintenance costs
- Decreasing wastes releases into the environment
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Since the 70's, the main concern has been 0 For PWR of western design: mitigation of and then
, very sensitive to
, particularly in alkaline conditions; 0 For VVER: mitigation of stainless steel SG tubing, particularly for the newer SG with higher temperature, sensitive areas; 0 For design, important degradation (pitting, etc) on many SG with Monel400; 0 For German design, improvement of chemistry selection (limited degradation in SG with mainly in the past under P04);
For SG that will operate (mainly lnconel 600TT-690/PWR, 18-10 TiNVER) the new challenge should focus on:
FAC of (less and less used) is also solved by similar remedies.
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~ Determine the type and concentration of conditioning reagents
~ Determine the acceptable limits for impurities
- Ammonia or amine (morpholine, ethanolamine, amines mixing)
I I
- Addition of hydrazine
- Few air Ingress I
- High quality demineralized water
- Mitigate condenser leaks
- Avoid other impurities
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Acceptable H areas Hat 25°C 6
Copper Alloys Condensers Heaters Titanium Condensers Stainless Steel Condensers Heaters Carbon Steel Heater....
lnconel SG Tubes Resins (IER),
effluents i
Unacceptable
_ H areas 1
9 1
10 I
- In presence of copper alloys, limitation of pH25oc"' 9.2 with NH3 (or higher with amine)
- Without copper, more open choice, with increased pH (optimum close to 1 0) and upper limit from economical and environmental constraints acceptable if other constraints
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ni Ammoniacal Corrosion (or similar with amines) of copper alloys pH < 9.3 with ammonia (potentially slightly more with amines)
Limitation of pH or reagent concentration depending on the operating mode of condensate polishers and SG Slowdown res1ns Flow Accelerated Corrosion of Carbon Steel Necessity of a sufficient pHT at operating temperature Limitation of reagent concentration due to operating costs and wastes releases into the environment Selection of ammonia, amines or amines mixing able to protect the whole steam-water system, with acceptable costs, operating constraints and liquid effluents or solid wastes releases
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nd ill n1 Ammonia NH3,H20 H~/H N+
OH-
/
~
H OH-CH2 -CH2 ""-.
/
H H
Morpholine C4H9NO,H20
/~/H 0
N+-OH-
"_/"
H
/
N+-OH-H Mainly Ammonia (most of German units), morpholine (most of French units), ethanolamine (most of US units)
Few other amines used, frequently mixed with one of the above ones
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HYDRAZINE: - Reduction of 0 2 and oxides N2H4 + 0 2 --+
N2 + 2 H20
- Thermal Decomposition N2H4 --+
N2, H2, NH3 Presence of copper alloys
> 10 IJ9 I kg in feedwater
~ Obtain a sufficient reducing effect
( N2H4 > 2 to 8 x 0 2 )
~ Not too high value, for not too high production of NH3 (ammoniacal corrosion)
Absence of copper alloys
~ 50 to 100 IJQ/kg in most cases EPRI > 20 and > 8 x 0 2 No benefit for values> 100 ppb Test performed with redox potential: 25 to 200 ppb N2H4 No benefit gained by an increase of hydrazine concentration for Suspended Solids mitigation (content and composition)
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yIn the USA, most units use an amine or a mixing of amines for the treatment. The most frequently used is ethanolamine (ETA), with an advantage in presence of condensate polishers and regenerated resins.
~ In Japan, half of the units are treated with ammonia at high pH and the other half with ethanolamine.
~ In Germany and some other European Countries where the units do not have copper alloys or condensate polisher in permanent use, ammonia at high pH-HAVT (ammonia at pH 25oc 9.8 to 1 0) is satisfactorily used.
~ In France, most units with morpholine
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I PEC00265883 Ill Ill Ill Ill Ill Ill Ill
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Vaporisation J
D Impurities Concentration Partition Coefficient Water concentration in SG bulk is - 100 times higher than in feedwater (Q FW/SGBD)
[ Concentration J Over concentration of impurities Concentration Factor Concentration factor is:
- ~ 1 0 to 1 02 free span ;
- ~ 103 to 106 restricted flow areas.
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0.001 to 0.00001 ~g/kg Local over concentration factor 10 3 to 10 6 Tube Support Plates Tubesheet (sludge pile)
Steam Low concentration Vaporization Concentration Factor: 100 SG Bulk Water 1 IJQ/kg Feedwater 0.01 IJQ/kg SG Slowdown 1 ~g/kg
- Very low concentration in feedwater (alimentation)
- Moderated concentration in the bulk water and SG blowdown (purge)
- Much higher concentration of impurities in area with restricted flow
- Constitutes a challenge for the secondary water chemistry, particularly with SG tubing 600 MA
.a Cl CD -
I PEC00265886
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IPEC00265887
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Most Frequent Case Na > Cl I Anions I I Cations I I
n Cl-II NaCI Neutral Na+ I HC03 -~
I Ca2+ I SQ42-I I
Ill Ill g
trable I
Ions I
I Volatile or.
I prec1-1 pitable Ions~
Non I concen-1 trable Less Frequent Case Na < Cl I Anions I I Cations I n
I NaCI II Na+
Neutral I Cl-I HCQ3-I I Ca2+
I SQ42-
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<D I Anions I Cl-S042-NaCI Neutral I Cations I Na+
I Ca2+ I Ill Ill Concentrable Ions Volatile or precipitable Ions ~
Non concentrable
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SODIUM (J,Jg/kg) 150 50 10 0
Operation< 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> River ZONE2 Acceptable limits 0.05 0.3 0.5 1.0 4
7 PIIIICIIIIIIICIII,..Ir8 Action Levels when Power > 25o/o CATION CONDUCTIVITY at 25°C, J,JS/cm
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<D Conden-Feed-Blow down Steam Parameters sate water water 9,0 +/- 0,2 8,0-9,2 pH at25°C, Electric conductivity, IJS/sm
<0,35
<0,3
<5,0
<0,3 Sodium, m kg/kg
<2,0
<300 Chloride, mkg/kg
<100 Sulfate, mkg/kg
<200 Iron, m kg/kg
<15 Copper, m kg/kg
<5 Oxygen, m kg/kg
<30
<10 Hydrazine, mkg/kg
> 40 (1 0)
Morpholine, mg/kg 3-6 Specifications at SG Slowdown are also much less restrictive than on PWR of Western countries. Different design, lower temperature and power, less sensitive SG tubing materials as compared to lnconel 600, but also some observed corrosion in some cases.
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- In France: Some flexibility in case of specific condenser sea water ingress with none localisable leaks
- In France: Some flexibility for sodium in zone 2 if sodium is coming from sea water and is not present in alkaline condition
- In the USA: more stringent limits due to past history and important degradation of OD SG tubes with lnconel 600MA.
But possibility to continue operation in AL 1 Y Whatever the specification severity: will hardly get rid of 600 MA corrosion YAIIoy 690 does not present the same sensitivity and does not require those unnecessary limits, as shown by laboratory tests and feedback since 1990
- The international feedback with other Alloys lncoloy 800 or stainless steel 18 o/o Cr-1 Oo/o Ni on VVER evidenced the absence of corrosion albeit much less stringent specifications and more important impurity levels.
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- Condenser water
- auxiliary circuit
- Make up water Condenser water
- Condenser water
- SG Slowdown resin
- F: welding
-Sulphur compounds; resin deterioration
' I, May concentrate Alkaline environment Non volatile, May precipitate in SG May concentrate Sulphates may also precipitate and adsorb on metal wall No corrosion risk since cannot concentrate But risk of heat transfer decrease from deposition in case of important quantities c1, F: sec Cl: pitting of SG tubes Cl +oxygen: denti at Tube Support Plate level Sulphur compounds from resins: very detrimental for SG tube corrosion
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in Organic
- Morpholine Partially volatile Increase of cation conductivity I Decomposition in SG and other parts of the Anions 1 (mainly in 0 2 Weak Acid system presence)
Low noxiousness for SG
- Oils and greases Uncertain for turbine Oxygen Air ingress Strong Oxidizer SG tubes SCC at high I (depending on Increases temperature
- pressure, Morpholine Risk denting, pitting..
condenser,...
Decomposition At low concentration, beneficial Reacts with metals for FAC
- ? oxides
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<D CJl 1 N2H4 ppb 1 NH3 ppb 1 Morpholine 1 pH 25°C 1 02 ppb I Cu ppb ppm 7
I 275 0
9.0 6
0.55 45 855 0
9.35 7
1.75 100 955 0
9.40 9
1.70 7
155 5
9.15 8
0.40 50 605 9.35 5
85 1175 6.4 9.50 7
1.90 0
80 4
9.10 4
0.30 Ref. Ph. Berge. The Use, Need, and Desirable Properties of Amines for Use in Steam-Water Circuits.
CEGB-Amine Workshop Proceedings SWR/SSD 0791/N/96. Bristol, England, 29 April-1 May 1986.
- Copper corrosion depends on pH25oc => Limited to 9.2 with ammonia
- Lower copper corrosion (-%)for same pH 25oc with morpholine
=> possibility of operating at a slightly higher pH with an amine.
IPEC00265896
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Type I
c I
Cr Fe I
Ni I
Co Usual Name Stainless Steel (> 13 % Cr) 13% Cr I
- 0.12 I 12-14 Balance (AISI) 304L
- 0.03 I 18-20 Balance I 8-12 (AISI) 316L I
- 0.03 I 16-18 Balance I 10-14 Nickel base Alloy
- 0.05 6-10
< 0.1
- 0.05 7-11
< 0.035
- 0.10 1
Balance Alloy 18-10 Ti (VVER)
- 0.08 17-19 Balance 10-11.5
< 0.05
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(
Chemical Environment
)
Results from 3 factors.
For a sensitive material, key factor:
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<D Corrosion and remedies related to tubing sensitivity to various impurities
- Excellent chemistry, absence of alkalinity may slow it down.
- Addition of inhibitor in some cases.
- Remedies +/-efficient
- No need for intensive constraints of 600MA
- Less restrictive chemistry ~ many advantages.
- WER had mainly corrosion on recent units with higher 8,
- Avoid acidic condition and heavy deposits
- Something intermediate may be considered
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0 Minimum time (h) for obtaining a 500 1-1m deep crack Alloy 600 TT 1......
4000 -+---------+JIIi:---------,
After Ph. BERGE et J.R. DONATI, Nuclear technology, October 1981, vol.55 ll 0 1, pp.88 to 104 Alloy 800 3000 I I
'\\
I I 2000 Alloy 600 IMA Alloy 690 TT 1000 I I "'=
I
\\: \\:
I Concentration of sodium hydroxide (g/1) 0 ----~-~--~-~---+------__.
1 4
10 40 100 500
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- OH intergranular generalized corrosion (IGA) in alkaline environment
- lntergranular stress corrosion cracking (presence of stresses)
- Cracking in oxidizing environment Other impurities:
- Oxides (Fe20 3, CuO... ) in alkaline environment. IG SCC 11 :.ru'\\nor
- o:~n Cracking of mixed mode type (intergranular and transgranular) when important pollutions
- C02 in OH environment in acidic or alkaline t II environment i
and their decomposition products (
r i:ll
-~i:ll)
- Complex environments uncertain P04 + Si02+AI20 3+ may be organic
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I 0 Lead has frequently been considered as the cause of cracking, particularly at the beginning of laboratory tests with cracking on Alloy 600, in 1959.
0 Lead is indubitably a detrimental parameter for SG tube cracking.
0 Lead is found in most of SG tubes and in sludge 0
In most cases, it has not been possible to draw any correlation between presence of lead and an increased risk of cracking (for amount close to typical value or slightly higher, i.e. 1% Pb/deposits and 0.1 %/sludge) 0 Only important lead pollution cases were clearly identified at the origin of specific and quick degradations in a few cases (Belgium, Canada).
0 Several American experts consider that lead is a significant contributor to IGA/SCC 0 According to a French study on many units, lead is not at the origin of most of degradations on Alloy 600MA. Key factors: caustic environment and material sensitivity.
0 Alloy 690 better resists to plausible lead pollution than 600, particularly in environments close to neutrality.
0 Alloy 690 may crack in strongly alkaline environments polluted by lead.
0 Some part of lead will deposit in feedwater train materials 0 SG Slowdown only eliminates a fraction of lead.
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Ill Ill Corrosion inhibitors selection depends on material and cooling water
- 1 st use for denting (70's)
- Alternate
- For a few
- Molar Ratio
- Efficient in Lab. condition with inhibitor WER Control NaOH for IGA/SCC
- Less efficient, Acid
- CI addition,
- Efficient in NPP, depends on according to neutralization brings an impurity penetration capacity within Lab
- Should not
- Alkalinity limitation crevices (good soak, after
- No clear replace a (e.g. no polishers) chemical cleaning).
advantage as good looks safer More efficient in sludge pile compared to chemistry
- A few acceptable drawbacks BAT
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Nbr Tubing TSP (Tube Support Cooling SCC Level units Plate) water Design Material 6
600MA Circular Carb S River High 2
600MA Circular Carb S Sea/Estuary Low 1
600MA Broached Carb S Loire M/H 2
600MA Broached Carb S Estuary
~a 1
600MA Broached 13%Cr Loire
~a 1
600MA Broached 13%Cr Estuary
~a 26 600TT Broached 13°/oCr Any No 19 690TT Broached 13%Cr Any No
- SG tubes on the secondary side are only affected for 600 MA, and mainly on river water cooled units with an alkaline trend.
- SG tubes 600 MA of sea water cooled units are very slightly affected.
- Only 600 MA tubing with carbon steel Tube Support Plates, easily corroded and creating an environment where impurities may concentrate, are significantly affected.
- No tube with 600 TT or 690 TT is cracked on the secondary side.
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- Poor Lay up
- Other (resins, metallic shots) i its EXTERNAL ORIGIN
- Cooling water (compounds with low solubility, e.g. Ca, Mg, 504)
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The most important and challenging issue for many units Loss of heat transfer, Pressure and Power May be limited by selecting adequate chemistry and operation practices:
~
(ammonia pH almost 1 0)
(mandatory with copper),
~
permanent use of selection or replacement,
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Li Linked to Corrosion product transport - Deposition
~
~
Minimize production Minimize deposition
- High pH
- Amine selection
- Amine selection with specific properties
- Same objective as for FAG
- Dispersant addition PAA
- N2 H4 limited to 50 - 1 00 ppb
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Fl I
~-,
i
- - 500 1/h on SG2 - R08C4 7 on cold leg
- On 11 Feb 2006, at night: 12 min. from 11 1/h (0.05 gpm) to-500 1/h
- Early detection by N16 +quick shutdown
- SG isolated, no environmental impact
- Tube non supported by AVB (Design only to Row 11)
- 21 0 o circumferential crack at upper face of Sth TSP
- Tube identified by water test
- No Eddy Current bobbin coil indication at Nov. 2005 forced outage
- Central area of tube bundle with specific local thermohydraulical conditions due to :
- important deposits on broached upper TSP
- TSP with holes w/o tube in central part
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- North Anna 1: July 15, 1987: Rupture of R9-C11 - SGC-model 51 A
- AVB misplaced. Design to Row 1, some cases to Row 8. This R9: no AVB
- Stress level increased by denting + U-Bend deflection = High cycle fatigue.
- Leak increase during 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> before rupture.
- Indian Point 3: Oct 19, 1988: R44-C50. SG Model44. Cause= Denting
(+minor IGA/SCC?). Circumferential Crack near the top of the upper TSP (#6).
- Three Mile Island 1990 (OTSG)
- Mihama 2: Feb 9, 1991. SG 44. AVB misplaced in central area of bundle.
Manufacturing anomaly non detected. Fatigue cracking at upper TSP.
- Cruas 1: Feb 4, 2004. R08-C49-SG2-51 B. See details UER of April 2004.
Leak of 3.8 1/h (0.017 gpm). Immediate shutdown. Circumferential 90 o signal.
Lack of material at upper TSP (#8). Wrongly attributed to loose part.
- Cruas 4: Nov 7, 2005. R08-C48-SG 2 -51 B : See details UER of Dec 2005.
Leak of 9 1/h (0.04 gpm). Shutdown before reaching the limit of 20 1/h.
Again Circumferential 90 o signal at upper TSP (#8).
Reason not accurately known.
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Fl II II TV Inspection at TSP# 8 - Blockage of water pass Deposits common Characteristics:
- Builds up from bottom part of water pass of quatrefoil area
- On the tube as well as in the quatrefoil area, almost centripetal progression
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<D illil illil I
I illil illil I
D Among all the units with SG 51 B, no treatment parameter has a value that may explain a TSP blockage difference, expect potentially lower hydrazine and thus ammonia values.
D The units of CRUAS 1 and 4 have, as compared to other units with low pH morpholine treatment and SG 51 B, a higher average sodium value at SG blowdown.
The river water leaks at the condenser may thus have a deleterious effect on TSP blockage by hardening the magnetite deposits.
D However, the TSP blockage started before the most important condenser leaks and potential correlation should be further evaluated before firm conclusion.
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Correlation TSP blockage/integrated sodium 7000 Q) >-c 6000 -
+CRU4
- River water o_
cooled units,
.c 0 CRU3 CRU1 CO.t: 5000 -
low FWpH ns tn z
~ 4000 -
River water "C.t:
BLA4
+CHB2 cooled units, Q)...., 3000 -
BLA3 CRU2 high FW pH
.......c ns c.
Sea water c, c. 2000 -
Q)M DAM1 CHB3 Cooled units, 1000 -
CHB4 high FW pH c: -
0 Low or None Medium High TSP # 8 HL Blockage
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isoersan Principle
- Permanent addition at low concentration of a polyacrylic acid reagent (PAA) in the secondary system during normal power operation Action
Expected Advantages of the process
- No corrosion of materials,
- Compatible with SG blowdown treatment on lon Exchange Resins,
- Low impact on cation conductivity at SG Slowdown,
- Possible release of the chemical product into the environment.
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- Metal affected :
CARBON STEEL Addition of some chromium slows down the phenomenon starting from 0.01 o/o Cr with an improvement factor - 5 for 0.1 o/o Cr.
- Chemical Conditions:
Acidic and reducing environment If pH or 0 2 content (few ppb) increases, phenomenon decreases
- Location :
- Separators-reheaters
- HP Heaters
-Drains
-Valves
-Tanks
- SG Internals
- Thermodynamic Conditions:
-Wet steam
- Water at high temperature
- High velocity
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- Units with copper alloys: treatment with sufficiently high pHt
- Units without copper alloys: ammonia treatment at pH25oc > 9.8 (-10) or amine treatment (pH 25oc > 9.4)
- Do not trv to excessivelv lower 0') (unnecessarv with lnconel 690..
- Selection of stainless or low alloyed steels
- Velocity Limitation.
- Protection against jet impact.
- Reduction of humiditv fraction
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Carbon Steel corrosion rate (mg/dm2/month) 10000 4000 2000 1000 800 600 400 200 100 80 60 40 20 10 2
5.65 Neutral pH at 300 oc Alkaline pH of minimum corrosion 3
4 5
6 7
8 9
10 11 12 pH at 300°C
IPEC00265917
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)
1. Steel oxidation by water at the Steel/Oxide interface, soluble Fe++ and magnetite formation Fe + 2H20 ~ Fe(OH)2 + H2 3 Fe + 2H20 ~Fe304 + 2 H2
- 2. Diffusion of soluble species (soluble Fe++ and H2) through the porous oxide layer
- 3. Reduction of the oxide at water/oxide interface 1/3Fe30 4 + (2-b)H+ + 1/3H2 ~
Fe(OH)b(2-b)++ (4/3-b)H20
- 4. Transfer of soluble species in water
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Main Feedwater Piping Rupture Piping: 560 mm - 150 oc -21st cycle of operation 9 August 2004.
KEPCO Information 1st U
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Temperature pH NH3 pH NH3 pH NH3 pH NH3 oc 8.3 9.2 9.5 9.7 140 24 10 4,3 2,1 185 11 6
2,8 1,3 205 7
4 2,3 1,1 225 5
3 2,1 1,0 In two phases environment, with a humidity rate of 10% in steam (weight basis)
The operating temperature pH is important.
A pH2soc of at least 9.7 must be selected to be equivalent to Morpholine 9.2. Ammonia at low pH is not acceptable.
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Oxyg~D Influence: Relative FAC Velocit EDF Tests - Les Renardieres Oxygen Concentration (~g/kg)
Some local oxygen (a few ppb) may be beneficial and kept on purpose. Applied in some cases (MSR, Germany with success)
Oxygen elimination before final feedwater and SG
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<D I'V I'V Portion of fragmented TSP ~-
4 corroded zones
- FAC:
Eliminated metal Dissolution -?fragmentation of TSP ligaments Concerning:
external zone, upper TSP, old design (Carbon steel, drilled holes), ammonia treatment (Gravelines in 96)
- Remedy - switching to morpholine treatment
-7 stopped phenomenon
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Sea water cooled All I Pollution All Corrosion All I products 18-1 OTi II I
Remed Boric Acid BAT Titanium, etc Molar Ratio MRC No permanent use of condensate polishers Avoid using polishing plant Tiaht condensers High pHT (High AVT or amine)
Keep some 02 High pHT Dispersant Clean the SG Avoid Cl, acids Add LiOH (+B)
Remedies can slightly compensate wrong old design (ln600,... )
Sophisticated, severe chemistry, polishing not necessary for 690, 800 New challenge is corrosion products deposition
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One of the main questions: mitigation of Stress Corrosion Cracking (SCC)
BWR treatment in Europe is based on various options:
- ru*vn = (Normal Water Chemistry) with a good water quality, thus a low concentration of Cl (< 1 ppb), S04, (< 3 ppb) and a low conductivity(< 0.1 !JS/cm)
- Hvv* = (Hydrogen Water Chemistry)
- NIVU =n (Noble Metal Chemical Addition) ~ minimize sec
Years 1970's, the neutral oxygenated treatment was applied.
SCC of piping induced replacement of AISI 304 stainless steel components A chemistry with less impurities has been implemented.
After SCC of core internals in the 1990's, hydrogen has been added to be in a reducing environment.
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- Similar corrosion Steam product transport and Dryer activation as for PWR, except corrosion Feedwater products come from the Top guide Sparger steam cycle Core Core Spray
- Deposition occurs in shroud Sparger recirculation piping I
Core Plate systems and reactor lfl_P~SLC water cleanup system Jet pump piping
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- H2 ::::? reducing environment ~ SCC
- But a high hydrogen addition 71 16N radioactive i during operation
- It is possible to alternatively keep a reducing environment with less hydrogen with Noble Metals Chemical Addition (NMCA), injected for the first time in 1996 (Duane Arnold) and presently used on 27 American units and 1 in Europe (Muehleberg).
- Uncertainties remain on NMCA efficiency toward dosimetry and deposits on fuel.
The continuous addition is under development.
- Iron concentration mitigation is important to avoid detrimental deposits on fuel.
In addition, iron oxides decrease zinc efficiency.
Thus, zinc is less in solution to bring its efficiency for dose rate.
- Copper elimination applied on BWR allows increasing H2 efficiency to decrease electro-chemical potential and also allows contributing at decreasing dose rates.
- As for PWR, keeping a sufficient oxygen concentration in the feed water for mitigating carbon steel FAC.
~
~
I 0 0
~
m
~
m
~
~
iti i
- Hydrogen Water Chemistry
- Noble Metal Application 1-oL'!:anl I
i I
- Zinc Injection 1-1 u::11l
- Uprating
- Crud (Iron, zinc, noble metals) 1-<!:al I t
- Flow-Accelerated Corrosion
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International Conference on Water Chemistry of Nuclear Reactors Systems-Jeju Island - Korea, October 20068. Stellwag, J. Lejon. BWR Water Chemistry Data Survey of European BWR Plants
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~*--fl~*111f1111.41Ni Control IGSCC of Piping Systems
~~~~Mitigate IGSCC of Reactor Internals Control Radiation F Avoid Fuel Crud Concerns Hydrogen Water Chemistry Low levels controls piping IGSCC I
Moderate HWC Noble Metals Increases N-16 in Refuel Outage Turbine Application I
I Zinc Injection Limit Feedwater Zinc and Reduce Iron Ingress
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0
--*l"'llrB
!!!II>'IP..... i 1977: Neutral, oxygenated water
~
1980s: Purer is better
~
Late 1980s -1990s: HWC, Zinc 2000s: Noble Metal Chemical Addition
~
2006-2008 On-line Noblechem
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i--
- IGSCC reduced by lowering the electrochemical corrosion potential of the coolant HWC demo started in 1982 at Dresden-2 Noble metal demo at Duane Arnold started in 1996
- Increases the effectiveness of low levels of hydrogen
- Change in structure of crud in the core, and oxide films on out-of-core surfaces, as a result of more reducing conditions
- Causes big increase in radiation fields, to a large extent mitigated by zinc Even more zinc required to avoid increased fields with noble metals - feedwater zinc limited by fuel concerns
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- The extensive use of lnconel 600 instead of traditional Stainless Steel {304) for avoiding SCC in presence of Chloride {and/or oxygen) induced extremely important degradation by sec even in pure water.
- Chemistry optimization for dose rates limitation in Primary coolant of PWR had to avoid any slight increase of such a corrosion, already problematic
- Chemistry severity and complexity have been implemented for secondary water of PWR to mitigate IGA/SCC of lnconel 600 MA with limited efficiency
- Amine treatment or high pH has been widely used in the secondary water of PWR to mitigate FAC of carbon steel
- Chemistry has been permanently upgraded {NMCA) in US BWR to mitigate sec of core components.
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aterial Aging lnstitu International Conference on Plants aterials Dearadations i
RIV000149 Date Submitted: June 9, 2015 United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of:
Entergy Nuclear Operations, Inc.
(Indian Point Nuclear Generating Units 2 and 3)
ASLBP #: 07-858-03-LR-BD01 Docket #: 05000247 l 05000286 Exhibit #:
Identified:
Admitted:
Withdrawn:
Rejected:
Stricken:
Other:
RIV000149-00-BD01 11/5/2015 11/5/2015
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tio :
- I jecti A poor chemistry may, on a rather long term, induce corrosion The effect is detrimental for components Adequate Chemistry 1 of the Circuits Long term availability of Units Safety of the plant lncreas Minimum of incidents
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CJl CJl 1......
The NPP strategy is adding new challenges to the most crucial previous weakness of Alloy lnconel 600:
SCC (Stress Corrosion Cracking).
~ Optimization of the primary water chemistry for dose rates minimization and high performance fuel operation (PWR and BWR).
~ Economical, environmentally sustainable and reliable operation of the circuits
~ Very high safety and availability levels of the NPP rm r
po r
I n r I i
II
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CJl (J) 1......
......,...j
- 1970s: Major ingresses of sea water, oil, ion exchange resins, etc. caused corrosion and fuel problems.
Impurities contributed to IGSCC of BWR piping.
Phosphate dosing of PWR steam generators caused wastage or IGA/SCC, leading to "all-volatile treatment" in 1974, which caused denting.
- 1980s: "Purer is Better" was the theme-it helped a lot but was not sufficient to eliminate problems in presence of Alloy 600.
- 1990s: BWR hydrogen water chemistry, zinc injection, pH control in PWR primary and secondary systems for FAC and SCC
- 2000s: Noble metal chemical addition in BWRs, PWR primary zinc injection, elevated pH or amine in most secondary systems of PWR for SG deposits and FAC mitigation, dispersants trial.
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CJl Fuel Performance and behavior SG tubes: IGA/SCC, pitting, denting,...
Condenser tubes degradation
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Fuel Performance and behavior Reactor components 304 steel : sec Condenser tubes dearadation
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- PWSCC, fuel behavior
- Amine, ammonia, corrosion inhibitors
- Copper alloys corrosion
- IGA/SCC (mainly lnconel 600 MA), low Accelerated orrosion of carbon steel, corrosion products deposition and low Induced ibration
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(J) 0 Ill
..... I Objective :
Neutralization of Boric acid in order to be in a slightly alkaline environment Optimum pH Low generalized corrosion
- minimize generation and transport of corrosion products
- minimize dose rates I Alkaline reagent selection I
- NaOH => 24Na
- KOH
=> 42K Acceptable, used in VVER
- NH40H low stability
- n '
- Low corrosion risk due to limited solubility and concentration Li-7 also produced from boron neutronic reaction 108 (n, a)?Li I
Radiochemistry I
Li natural :
6Li :
7.42 °/o 7Li : 92.58 °/o 6
3Li + 1 0n => 4 2 He + 3 1 H (tritium) 6Li (n, a) T
=> use of 7Li enriched to 99.9 o/o
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(J) 3 main questions for Primary Water Chemistry options (I
)
- Dose rates,
- CIPS (AOA) 41 (I *
- Dose rates
- CIPS (AOA)
)
i/Dose rates,
- CIPS (AOA),
- Safety, design
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Typical pH 300oc range 7.2 to 7.4
- BOC, 1""""-ll"l.il"!>l 1n
- Dose rate Impact, Target pH has been progressively increased in many cases, (calculation codes, feedback)
Limited impact within this range
- risk of Cl PS
- But more impact if pH too low Boron-Li precipitation, other factors (Ni)
- K (VVER) versus Li difference,
- Compromise with 7Li cost (load follow, transients, shutdown) under investigation (IAEA/FUWAC)
PWR: Typical Li max= 2.2 or 3.5 ppm Some cases with even higher values No benefit expected for PWSCC, but potentially for dosimetry
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V>
- 2 71
)
""'"~"'~
least 3.5 oom Typical Li max= 2.2 or 3.5 ppm, some cases higher No benefit of higher value expected for PWSCC, but potentially for dosimetry
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1--~
) -
- Subcooled nucleate boiling and associated crud deposits
- Boron content + Li Impact of new fuel options, longer fuel cycles ~ Higher B at BOC Boron precipitation in crud.
- pH influence on corrosion product transport, deposition, crud thickness
=>
I i
- Nickel content in Materials lnconel 600 the worse. 690 better.
lncoloy 800 (Germany) satisfying 18-1 0 (WER) the best.
- Optimum pH with limited B
- ? Li also limited
- May avoid design modification
- Highly advisable to consider for new plants
- *u*in r i although more beneficial relative to zircaloy corrosion and ~ B in crud
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CJl F
4,0 I Lim ax = 3.5 ppm I:
3,5 3,0 2,5
~2,0
- .J 1,5 1,0 0,5 0,0 1800 1600 1400 Under itnplementation on 4 EDF
-I-------- -------
-~---------I--------
pH 3oooc target= 7.2 target= 7.0 I
I
1--------~-----
________ l ________ j _______ _
I I
________ l ________ j _______ _
I I
1200 1000 800 600 400 200 Boron (ppm) 450Me Alcade) 0
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(J) 70 (J)
~60 c ro 0:::
-~50
..c
+-'
maximum
~ 40
(/)
full power
~
c Xe-
'+- 30 0
equilibrated
())
lithium 0>
~ 20 c
())
()
I....
()) 10 0...
0 2000 2001 2002 2003 2004 2005 2006 2007 EOC Year I
<3 ppm
- 3.0-3.5 ppm D >3.5 ppm I
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(J) i--
I I
- This is of potential interest in a few cases Y Postponing or avoiding SG Replacement in presence 600 TT Y Mitigating SCC of components lnconel 600 other than SG tubing
- Dose rate limitation:
lower content 0..
More and more used, Inhibiting Co incorporation in corrosion products. Potential interactions to be considered
- Usually depleted Zinc added
- Easy method
- Limited associated risk for the fuel due to low Zn
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.. I WeibullFit (Least Squares) 90
% ~
I I
I I
I I I II
~~~ r::-:_-- =--::-:_-- r-::-:_--t-t-l =t:_-l j_:t j ~
20%
fl
~
10%b---------r---~--~--~~--~-+~------~~----~L_~--r-+-~4-+-
~
5%
~
~
2%
~
1 Zinc
-~
0.5%
1 °.2%
-+
-~- t-1-1 to= 0.00 EFPY ~
0°0::
b:~0.90:--I---~--
0.02%
o.o1% f-~~~~r-~~--,----i~~~--,--j--rl--rtrl-~~~H~--~4-~4-~h--h-+-c-h+,-j 3
4 5
6 8
10 20 30 40 50 60 80 100 Service Time (EDY@ 607°F)
Cumulative % of failed tube versus time with or without 35 ppb Zinc.
I (
Zinc Impact on PWSCC What is the impact of zinc injection on PWSCC initiation and crack growth rate(s).
1 US Utility has experienced a 79% reduction in the Weibull Slope with a target zinc level of 35 ppb.
A comprehensive EPRI review of US plants consistently demonstrated a significant benefit of zinc Reduced crack growth benefit of zinc shown for A600 SG tubes does not necessarily transfer to thick-wall RCS components and to A82/182 welds
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(J)
<D Laboratory tests not all in agreement.
Higher influence on lnconel 600 crack propagation than initiation
- Elimination duration at shutdown
- Gaseous wastes e.g. Factor 2 from 20 to 5 cc EPRI: either low or high but large scatter, limited impact
- Risk of radiolysis 5 ml/kg sufficient, always achieved 4D l!ooii!'IC::M"'
r-nrrnc;:
n See belOW
- Low value control low pressure difficult to keep constant
- Start to decrease before shutdown I PWSCC Propagation I Sweden : select either low < 1 0 cc or High > 30 cc (low impact)
EPRI: would need <5 impractical thus higher H2 is better
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0 1----**
- Zinc is Beneficial
-Increases PWSCC initiation time, but beneficial effect on crack growth rates is uncertain
- May need to remove hydrogen sooner in shut down process D Going to lower hydrogen may increase crack propagation at lower RCS temperatures (e.g. 290°C)
D Operation at low hydrogen increases the risk of going to oxidizing conditions in the event of a plant transient, e.g. loss of letdown flow.
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Ill I Corrosion Potential, mVshe
-700
-750
-800
-850
-900 9
~
I I
I I
I I
I I
I I
I I
I I
I I
Peak in Growth Rate= 8X as Expected for Alloy 82/182 Change in CGR for various step changes in Hz Hz change 600 82/182 10 ~ 20:
1.24X 1.34X 8
7 a>
1U 6 0:::
J:
j 5
e
(!)
~ 4 e -:e 3
<(
2 Schematic Plot of Effect of H2 on Crack Growth Rate For 325C where potential,J...
by 59.35 mV per 10X 1' in H2
& 118.7 mV per unit 1' in pH 50 mV Full Width Half Max Peak in Growth Rate = 3X as Expected for Alloy 600 20 ~ 40:
1.61X 2.17X 40 ~ 80:
1.38X 2.11X 20 ~ 80:
2.23X 4.58X 20 ~ 200: 2.42X 5.93X 10 ~ 200: 2.99X 7.97X 0 +-----~--~--~~~~~------~--~~~~~~~----~--~~~~~~~----~--~--~~~~~
0 1
10 100 1000 Hz Fugacity, cc/kg
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I'V 600,690 High ooco All High Co I Zinc Enriched Boric Acid All ICIPS, AOA I Limited B, Li K instead Li 18-10Ti 1 Pitting, sec Avoid Cl Resins H2 instead NH3 Remedies will partially depend on the design, materials No highly efficient option for inappropriate material IN600 (600 MA or 600 TT in presence of high stress level)
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V>
~ Keep long term integrity of components
~ Insure operation in good conditions for safety, availability, costs and maintenance The challenges include
- Avoiding ammoniacal corrosion of Cu alloys
- Mitigating IGA/SCC of Alloy 600 SG tubing
- Lowering fouling of SG tubing, heat transfer, flow
- Decreasing operating and maintenance costs
- Decreasing wastes releases into the environment
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Since the 70's, the main concern has been 0 For PWR of western design: mitigation of and then
, very sensitive to
, particularly in alkaline conditions; 0 For VVER: mitigation of stainless steel SG tubing, particularly for the newer SG with higher temperature, sensitive areas; 0 For design, important degradation (pitting, etc) on many SG with Monel400; 0 For German design, improvement of chemistry selection (limited degradation in SG with mainly in the past under P04);
For SG that will operate (mainly lnconel 600TT-690/PWR, 18-10 TiNVER) the new challenge should focus on:
FAC of (less and less used) is also solved by similar remedies.
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~ Determine the type and concentration of conditioning reagents
~ Determine the acceptable limits for impurities
- Ammonia or amine (morpholine, ethanolamine, amines mixing)
I I
- Addition of hydrazine
- Few air Ingress I
- High quality demineralized water
- Mitigate condenser leaks
- Avoid other impurities
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Acceptable H areas Hat 25°C 6
Copper Alloys Condensers Heaters Titanium Condensers Stainless Steel Condensers Heaters Carbon Steel Heater....
lnconel SG Tubes Resins (IER),
effluents i
Unacceptable
_ H areas 1
9 1
10 I
- In presence of copper alloys, limitation of pH25oc"' 9.2 with NH3 (or higher with amine)
- Without copper, more open choice, with increased pH (optimum close to 1 0) and upper limit from economical and environmental constraints acceptable if other constraints
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ni Ammoniacal Corrosion (or similar with amines) of copper alloys pH < 9.3 with ammonia (potentially slightly more with amines)
Limitation of pH or reagent concentration depending on the operating mode of condensate polishers and SG Slowdown res1ns Flow Accelerated Corrosion of Carbon Steel Necessity of a sufficient pHT at operating temperature Limitation of reagent concentration due to operating costs and wastes releases into the environment Selection of ammonia, amines or amines mixing able to protect the whole steam-water system, with acceptable costs, operating constraints and liquid effluents or solid wastes releases
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nd ill n1 Ammonia NH3,H20 H~/H N+
OH-
/
~
H OH-CH2 -CH2 ""-.
/
H H
Morpholine C4H9NO,H20
/~/H 0
N+-OH-
"_/"
H
/
N+-OH-H Mainly Ammonia (most of German units), morpholine (most of French units), ethanolamine (most of US units)
Few other amines used, frequently mixed with one of the above ones
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HYDRAZINE: - Reduction of 0 2 and oxides N2H4 + 0 2 --+
N2 + 2 H20
- Thermal Decomposition N2H4 --+
N2, H2, NH3 Presence of copper alloys
> 10 IJ9 I kg in feedwater
~ Obtain a sufficient reducing effect
( N2H4 > 2 to 8 x 0 2 )
~ Not too high value, for not too high production of NH3 (ammoniacal corrosion)
Absence of copper alloys
~ 50 to 100 IJQ/kg in most cases EPRI > 20 and > 8 x 0 2 No benefit for values> 100 ppb Test performed with redox potential: 25 to 200 ppb N2H4 No benefit gained by an increase of hydrazine concentration for Suspended Solids mitigation (content and composition)
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0 Ill I
yIn the USA, most units use an amine or a mixing of amines for the treatment. The most frequently used is ethanolamine (ETA), with an advantage in presence of condensate polishers and regenerated resins.
~ In Japan, half of the units are treated with ammonia at high pH and the other half with ethanolamine.
~ In Germany and some other European Countries where the units do not have copper alloys or condensate polisher in permanent use, ammonia at high pH-HAVT (ammonia at pH 25oc 9.8 to 1 0) is satisfactorily used.
~ In France, most units with morpholine
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tn Q)
C) ns
+"' c ns >
"'C
<(
tn Q)
C) ns
+"' c ns >
"'C ns tn *-c I
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I'V tn Q)
C) ns
+"' c ns >
"'C
<(
tn Q)
C) ns
+"' c ns >
"'C ns tn *-c 41"11 fiiV't.II"\\II'!!Jr.ll!!"'o
.c "
c !
- u.
I PEC00265883 Ill Ill Ill Ill Ill Ill Ill
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[
Vaporisation J
D Impurities Concentration Partition Coefficient Water concentration in SG bulk is - 100 times higher than in feedwater (Q FW/SGBD)
[ Concentration J Over concentration of impurities Concentration Factor Concentration factor is:
- ~ 1 0 to 1 02 free span ;
- ~ 103 to 106 restricted flow areas.
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0.001 to 0.00001 ~g/kg Local over concentration factor 10 3 to 10 6 Tube Support Plates Tubesheet (sludge pile)
Steam Low concentration Vaporization Concentration Factor: 100 SG Bulk Water 1 IJQ/kg Feedwater 0.01 IJQ/kg SG Slowdown 1 ~g/kg
- Very low concentration in feedwater (alimentation)
- Moderated concentration in the bulk water and SG blowdown (purge)
- Much higher concentration of impurities in area with restricted flow
- Constitutes a challenge for the secondary water chemistry, particularly with SG tubing 600 MA
.a Cl CD -
I PEC00265886
()}
()}
"1-..c 0
f/)
()}
- a...0 0
- J I-I-
c...
IPEC00265887
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Most Frequent Case Na > Cl I Anions I I Cations I I
n Cl-II NaCI Neutral Na+ I HC03 -~
I Ca2+ I SQ42-I I
Ill Ill g
trable I
Ions I
I Volatile or.
I prec1-1 pitable Ions~
Non I concen-1 trable Less Frequent Case Na < Cl I Anions I I Cations I n
I NaCI II Na+
Neutral I Cl-I HCQ3-I I Ca2+
I SQ42-
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<D I Anions I Cl-S042-NaCI Neutral I Cations I Na+
I Ca2+ I Ill Ill Concentrable Ions Volatile or precipitable Ions ~
Non concentrable
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<D 0
SODIUM (J,Jg/kg) 150 50 10 0
Operation< 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> River ZONE2 Acceptable limits 0.05 0.3 0.5 1.0 4
7 PIIIICIIIIIIICIII,..Ir8 Action Levels when Power > 25o/o CATION CONDUCTIVITY at 25°C, J,JS/cm
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<D Conden-Feed-Blow down Steam Parameters sate water water 9,0 +/- 0,2 8,0-9,2 pH at25°C, Electric conductivity, IJS/sm
<0,35
<0,3
<5,0
<0,3 Sodium, m kg/kg
<2,0
<300 Chloride, mkg/kg
<100 Sulfate, mkg/kg
<200 Iron, m kg/kg
<15 Copper, m kg/kg
<5 Oxygen, m kg/kg
<30
<10 Hydrazine, mkg/kg
> 40 (1 0)
Morpholine, mg/kg 3-6 Specifications at SG Slowdown are also much less restrictive than on PWR of Western countries. Different design, lower temperature and power, less sensitive SG tubing materials as compared to lnconel 600, but also some observed corrosion in some cases.
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- In France: Some flexibility in case of specific condenser sea water ingress with none localisable leaks
- In France: Some flexibility for sodium in zone 2 if sodium is coming from sea water and is not present in alkaline condition
- In the USA: more stringent limits due to past history and important degradation of OD SG tubes with lnconel 600MA.
But possibility to continue operation in AL 1 Y Whatever the specification severity: will hardly get rid of 600 MA corrosion YAIIoy 690 does not present the same sensitivity and does not require those unnecessary limits, as shown by laboratory tests and feedback since 1990
- The international feedback with other Alloys lncoloy 800 or stainless steel 18 o/o Cr-1 Oo/o Ni on VVER evidenced the absence of corrosion albeit much less stringent specifications and more important impurity levels.
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- Condenser water
- auxiliary circuit
- Make up water Condenser water
- Condenser water
- SG Slowdown resin
- F: welding
-Sulphur compounds; resin deterioration
' I, May concentrate Alkaline environment Non volatile, May precipitate in SG May concentrate Sulphates may also precipitate and adsorb on metal wall No corrosion risk since cannot concentrate But risk of heat transfer decrease from deposition in case of important quantities c1, F: sec Cl: pitting of SG tubes Cl +oxygen: denti at Tube Support Plate level Sulphur compounds from resins: very detrimental for SG tube corrosion
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in Organic
- Morpholine Partially volatile Increase of cation conductivity I Decomposition in SG and other parts of the Anions 1 (mainly in 0 2 Weak Acid system presence)
Low noxiousness for SG
- Oils and greases Uncertain for turbine Oxygen Air ingress Strong Oxidizer SG tubes SCC at high I (depending on Increases temperature
- pressure, Morpholine Risk denting, pitting..
condenser,...
Decomposition At low concentration, beneficial Reacts with metals for FAC
- ? oxides
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<D CJl 1 N2H4 ppb 1 NH3 ppb 1 Morpholine 1 pH 25°C 1 02 ppb I Cu ppb ppm 7
I 275 0
9.0 6
0.55 45 855 0
9.35 7
1.75 100 955 0
9.40 9
1.70 7
155 5
9.15 8
0.40 50 605 9.35 5
85 1175 6.4 9.50 7
1.90 0
80 4
9.10 4
0.30 Ref. Ph. Berge. The Use, Need, and Desirable Properties of Amines for Use in Steam-Water Circuits.
CEGB-Amine Workshop Proceedings SWR/SSD 0791/N/96. Bristol, England, 29 April-1 May 1986.
- Copper corrosion depends on pH25oc => Limited to 9.2 with ammonia
- Lower copper corrosion (-%)for same pH 25oc with morpholine
=> possibility of operating at a slightly higher pH with an amine.
IPEC00265896
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<D I
Type I
c I
Cr Fe I
Ni I
Co Usual Name Stainless Steel (> 13 % Cr) 13% Cr I
- 0.12 I 12-14 Balance (AISI) 304L
- 0.03 I 18-20 Balance I 8-12 (AISI) 316L I
- 0.03 I 16-18 Balance I 10-14 Nickel base Alloy
- 0.05 6-10
< 0.1
- 0.05 7-11
< 0.035
- 0.10 1
Balance Alloy 18-10 Ti (VVER)
- 0.08 17-19 Balance 10-11.5
< 0.05
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(
Chemical Environment
)
Results from 3 factors.
For a sensitive material, key factor:
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<D
<D Corrosion and remedies related to tubing sensitivity to various impurities
- Excellent chemistry, absence of alkalinity may slow it down.
- Addition of inhibitor in some cases.
- Remedies +/-efficient
- No need for intensive constraints of 600MA
- Less restrictive chemistry ~ many advantages.
- WER had mainly corrosion on recent units with higher 8,
- Avoid acidic condition and heavy deposits
- Something intermediate may be considered
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0 Minimum time (h) for obtaining a 500 1-1m deep crack Alloy 600 TT 1......
4000 -+---------+JIIi:---------,
After Ph. BERGE et J.R. DONATI, Nuclear technology, October 1981, vol.55 ll 0 1, pp.88 to 104 Alloy 800 3000 I I
'\\
I I 2000 Alloy 600 IMA Alloy 690 TT 1000 I I "'=
I
\\: \\:
I Concentration of sodium hydroxide (g/1) 0 ----~-~--~-~---+------__.
1 4
10 40 100 500
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r I I
- OH intergranular generalized corrosion (IGA) in alkaline environment
- lntergranular stress corrosion cracking (presence of stresses)
- Cracking in oxidizing environment Other impurities:
- Oxides (Fe20 3, CuO... ) in alkaline environment. IG SCC 11 :.ru'\\nor
- o:~n Cracking of mixed mode type (intergranular and transgranular) when important pollutions
- C02 in OH environment in acidic or alkaline t II environment i
and their decomposition products (
r i:ll
-~i:ll)
- Complex environments uncertain P04 + Si02+AI20 3+ may be organic
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I 0 Lead has frequently been considered as the cause of cracking, particularly at the beginning of laboratory tests with cracking on Alloy 600, in 1959.
0 Lead is indubitably a detrimental parameter for SG tube cracking.
0 Lead is found in most of SG tubes and in sludge 0
In most cases, it has not been possible to draw any correlation between presence of lead and an increased risk of cracking (for amount close to typical value or slightly higher, i.e. 1% Pb/deposits and 0.1 %/sludge) 0 Only important lead pollution cases were clearly identified at the origin of specific and quick degradations in a few cases (Belgium, Canada).
0 Several American experts consider that lead is a significant contributor to IGA/SCC 0 According to a French study on many units, lead is not at the origin of most of degradations on Alloy 600MA. Key factors: caustic environment and material sensitivity.
0 Alloy 690 better resists to plausible lead pollution than 600, particularly in environments close to neutrality.
0 Alloy 690 may crack in strongly alkaline environments polluted by lead.
0 Some part of lead will deposit in feedwater train materials 0 SG Slowdown only eliminates a fraction of lead.
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Ill Ill Corrosion inhibitors selection depends on material and cooling water
- 1 st use for denting (70's)
- Alternate
- For a few
- Molar Ratio
- Efficient in Lab. condition with inhibitor WER Control NaOH for IGA/SCC
- Less efficient, Acid
- CI addition,
- Efficient in NPP, depends on according to neutralization brings an impurity penetration capacity within Lab
- Should not
- Alkalinity limitation crevices (good soak, after
- No clear replace a (e.g. no polishers) chemical cleaning).
advantage as good looks safer More efficient in sludge pile compared to chemistry
- A few acceptable drawbacks BAT
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Nbr Tubing TSP (Tube Support Cooling SCC Level units Plate) water Design Material 6
600MA Circular Carb S River High 2
600MA Circular Carb S Sea/Estuary Low 1
600MA Broached Carb S Loire M/H 2
600MA Broached Carb S Estuary
~a 1
600MA Broached 13%Cr Loire
~a 1
600MA Broached 13%Cr Estuary
~a 26 600TT Broached 13°/oCr Any No 19 690TT Broached 13%Cr Any No
- SG tubes on the secondary side are only affected for 600 MA, and mainly on river water cooled units with an alkaline trend.
- SG tubes 600 MA of sea water cooled units are very slightly affected.
- Only 600 MA tubing with carbon steel Tube Support Plates, easily corroded and creating an environment where impurities may concentrate, are significantly affected.
- No tube with 600 TT or 690 TT is cracked on the secondary side.
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- Poor Lay up
- Other (resins, metallic shots) i its EXTERNAL ORIGIN
- Cooling water (compounds with low solubility, e.g. Ca, Mg, 504)
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The most important and challenging issue for many units Loss of heat transfer, Pressure and Power May be limited by selecting adequate chemistry and operation practices:
~
(ammonia pH almost 1 0)
(mandatory with copper),
~
permanent use of selection or replacement,
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Li Linked to Corrosion product transport - Deposition
~
~
Minimize production Minimize deposition
- High pH
- Amine selection
- Amine selection with specific properties
- Same objective as for FAG
- Dispersant addition PAA
- N2 H4 limited to 50 - 1 00 ppb
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Fl I
~-,
i
- - 500 1/h on SG2 - R08C4 7 on cold leg
- On 11 Feb 2006, at night: 12 min. from 11 1/h (0.05 gpm) to-500 1/h
- Early detection by N16 +quick shutdown
- SG isolated, no environmental impact
- Tube non supported by AVB (Design only to Row 11)
- 21 0 o circumferential crack at upper face of Sth TSP
- Tube identified by water test
- No Eddy Current bobbin coil indication at Nov. 2005 forced outage
- Central area of tube bundle with specific local thermohydraulical conditions due to :
- important deposits on broached upper TSP
- TSP with holes w/o tube in central part
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<D
.. I
- North Anna 1: July 15, 1987: Rupture of R9-C11 - SGC-model 51 A
- AVB misplaced. Design to Row 1, some cases to Row 8. This R9: no AVB
- Stress level increased by denting + U-Bend deflection = High cycle fatigue.
- Leak increase during 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> before rupture.
- Indian Point 3: Oct 19, 1988: R44-C50. SG Model44. Cause= Denting
(+minor IGA/SCC?). Circumferential Crack near the top of the upper TSP (#6).
- Three Mile Island 1990 (OTSG)
- Mihama 2: Feb 9, 1991. SG 44. AVB misplaced in central area of bundle.
Manufacturing anomaly non detected. Fatigue cracking at upper TSP.
- Cruas 1: Feb 4, 2004. R08-C49-SG2-51 B. See details UER of April 2004.
Leak of 3.8 1/h (0.017 gpm). Immediate shutdown. Circumferential 90 o signal.
Lack of material at upper TSP (#8). Wrongly attributed to loose part.
- Cruas 4: Nov 7, 2005. R08-C48-SG 2 -51 B : See details UER of Dec 2005.
Leak of 9 1/h (0.04 gpm). Shutdown before reaching the limit of 20 1/h.
Again Circumferential 90 o signal at upper TSP (#8).
Reason not accurately known.
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Fl II II TV Inspection at TSP# 8 - Blockage of water pass Deposits common Characteristics:
- Builds up from bottom part of water pass of quatrefoil area
- On the tube as well as in the quatrefoil area, almost centripetal progression
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<D illil illil I
I illil illil I
D Among all the units with SG 51 B, no treatment parameter has a value that may explain a TSP blockage difference, expect potentially lower hydrazine and thus ammonia values.
D The units of CRUAS 1 and 4 have, as compared to other units with low pH morpholine treatment and SG 51 B, a higher average sodium value at SG blowdown.
The river water leaks at the condenser may thus have a deleterious effect on TSP blockage by hardening the magnetite deposits.
D However, the TSP blockage started before the most important condenser leaks and potential correlation should be further evaluated before firm conclusion.
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<D I'V II II I
Correlation TSP blockage/integrated sodium 7000 Q) >-c 6000 -
+CRU4
- River water o_
cooled units,
.c 0 CRU3 CRU1 CO.t: 5000 -
low FWpH ns tn z
~ 4000 -
River water "C.t:
BLA4
+CHB2 cooled units, Q)...., 3000 -
BLA3 CRU2 high FW pH
.......c ns c.
Sea water c, c. 2000 -
Q)M DAM1 CHB3 Cooled units, 1000 -
CHB4 high FW pH c: -
0 Low or None Medium High TSP # 8 HL Blockage
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<D V>
isoersan Principle
- Permanent addition at low concentration of a polyacrylic acid reagent (PAA) in the secondary system during normal power operation Action
Expected Advantages of the process
- No corrosion of materials,
- Compatible with SG blowdown treatment on lon Exchange Resins,
- Low impact on cation conductivity at SG Slowdown,
- Possible release of the chemical product into the environment.
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- Metal affected :
CARBON STEEL Addition of some chromium slows down the phenomenon starting from 0.01 o/o Cr with an improvement factor - 5 for 0.1 o/o Cr.
- Chemical Conditions:
Acidic and reducing environment If pH or 0 2 content (few ppb) increases, phenomenon decreases
- Location :
- Separators-reheaters
- HP Heaters
-Drains
-Valves
-Tanks
- SG Internals
- Thermodynamic Conditions:
-Wet steam
- Water at high temperature
- High velocity
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- Units with copper alloys: treatment with sufficiently high pHt
- Units without copper alloys: ammonia treatment at pH25oc > 9.8 (-10) or amine treatment (pH 25oc > 9.4)
- Do not trv to excessivelv lower 0') (unnecessarv with lnconel 690..
- Selection of stainless or low alloyed steels
- Velocity Limitation.
- Protection against jet impact.
- Reduction of humiditv fraction
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Carbon Steel corrosion rate (mg/dm2/month) 10000 4000 2000 1000 800 600 400 200 100 80 60 40 20 10 2
5.65 Neutral pH at 300 oc Alkaline pH of minimum corrosion 3
4 5
6 7
8 9
10 11 12 pH at 300°C
IPEC00265917
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)
1. Steel oxidation by water at the Steel/Oxide interface, soluble Fe++ and magnetite formation Fe + 2H20 ~ Fe(OH)2 + H2 3 Fe + 2H20 ~Fe304 + 2 H2
- 2. Diffusion of soluble species (soluble Fe++ and H2) through the porous oxide layer
- 3. Reduction of the oxide at water/oxide interface 1/3Fe30 4 + (2-b)H+ + 1/3H2 ~
Fe(OH)b(2-b)++ (4/3-b)H20
- 4. Transfer of soluble species in water
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Main Feedwater Piping Rupture Piping: 560 mm - 150 oc -21st cycle of operation 9 August 2004.
KEPCO Information 1st U
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Temperature pH NH3 pH NH3 pH NH3 pH NH3 oc 8.3 9.2 9.5 9.7 140 24 10 4,3 2,1 185 11 6
2,8 1,3 205 7
4 2,3 1,1 225 5
3 2,1 1,0 In two phases environment, with a humidity rate of 10% in steam (weight basis)
The operating temperature pH is important.
A pH2soc of at least 9.7 must be selected to be equivalent to Morpholine 9.2. Ammonia at low pH is not acceptable.
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Oxyg~D Influence: Relative FAC Velocit EDF Tests - Les Renardieres Oxygen Concentration (~g/kg)
Some local oxygen (a few ppb) may be beneficial and kept on purpose. Applied in some cases (MSR, Germany with success)
Oxygen elimination before final feedwater and SG
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<D I'V I'V Portion of fragmented TSP ~-
4 corroded zones
- FAC:
Eliminated metal Dissolution -?fragmentation of TSP ligaments Concerning:
external zone, upper TSP, old design (Carbon steel, drilled holes), ammonia treatment (Gravelines in 96)
- Remedy - switching to morpholine treatment
-7 stopped phenomenon
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Sea water cooled All I Pollution All Corrosion All I products 18-1 OTi II I
Remed Boric Acid BAT Titanium, etc Molar Ratio MRC No permanent use of condensate polishers Avoid using polishing plant Tiaht condensers High pHT (High AVT or amine)
Keep some 02 High pHT Dispersant Clean the SG Avoid Cl, acids Add LiOH (+B)
Remedies can slightly compensate wrong old design (ln600,... )
Sophisticated, severe chemistry, polishing not necessary for 690, 800 New challenge is corrosion products deposition
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One of the main questions: mitigation of Stress Corrosion Cracking (SCC)
BWR treatment in Europe is based on various options:
- ru*vn = (Normal Water Chemistry) with a good water quality, thus a low concentration of Cl (< 1 ppb), S04, (< 3 ppb) and a low conductivity(< 0.1 !JS/cm)
- Hvv* = (Hydrogen Water Chemistry)
- NIVU =n (Noble Metal Chemical Addition) ~ minimize sec
Years 1970's, the neutral oxygenated treatment was applied.
SCC of piping induced replacement of AISI 304 stainless steel components A chemistry with less impurities has been implemented.
After SCC of core internals in the 1990's, hydrogen has been added to be in a reducing environment.
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- Similar corrosion Steam product transport and Dryer activation as for PWR, except corrosion Feedwater products come from the Top guide Sparger steam cycle Core Core Spray
- Deposition occurs in shroud Sparger recirculation piping I
Core Plate systems and reactor lfl_P~SLC water cleanup system Jet pump piping
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- H2 ::::? reducing environment ~ SCC
- But a high hydrogen addition 71 16N radioactive i during operation
- It is possible to alternatively keep a reducing environment with less hydrogen with Noble Metals Chemical Addition (NMCA), injected for the first time in 1996 (Duane Arnold) and presently used on 27 American units and 1 in Europe (Muehleberg).
- Uncertainties remain on NMCA efficiency toward dosimetry and deposits on fuel.
The continuous addition is under development.
- Iron concentration mitigation is important to avoid detrimental deposits on fuel.
In addition, iron oxides decrease zinc efficiency.
Thus, zinc is less in solution to bring its efficiency for dose rate.
- Copper elimination applied on BWR allows increasing H2 efficiency to decrease electro-chemical potential and also allows contributing at decreasing dose rates.
- As for PWR, keeping a sufficient oxygen concentration in the feed water for mitigating carbon steel FAC.
~
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- Hydrogen Water Chemistry
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- Crud (Iron, zinc, noble metals) 1-<!:al I t
- Flow-Accelerated Corrosion
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International Conference on Water Chemistry of Nuclear Reactors Systems-Jeju Island - Korea, October 20068. Stellwag, J. Lejon. BWR Water Chemistry Data Survey of European BWR Plants
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~~~~Mitigate IGSCC of Reactor Internals Control Radiation F Avoid Fuel Crud Concerns Hydrogen Water Chemistry Low levels controls piping IGSCC I
Moderate HWC Noble Metals Increases N-16 in Refuel Outage Turbine Application I
I Zinc Injection Limit Feedwater Zinc and Reduce Iron Ingress
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Late 1980s -1990s: HWC, Zinc 2000s: Noble Metal Chemical Addition
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2006-2008 On-line Noblechem
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- IGSCC reduced by lowering the electrochemical corrosion potential of the coolant HWC demo started in 1982 at Dresden-2 Noble metal demo at Duane Arnold started in 1996
- Increases the effectiveness of low levels of hydrogen
- Change in structure of crud in the core, and oxide films on out-of-core surfaces, as a result of more reducing conditions
- Causes big increase in radiation fields, to a large extent mitigated by zinc Even more zinc required to avoid increased fields with noble metals - feedwater zinc limited by fuel concerns
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- The extensive use of lnconel 600 instead of traditional Stainless Steel {304) for avoiding SCC in presence of Chloride {and/or oxygen) induced extremely important degradation by sec even in pure water.
- Chemistry optimization for dose rates limitation in Primary coolant of PWR had to avoid any slight increase of such a corrosion, already problematic
- Chemistry severity and complexity have been implemented for secondary water of PWR to mitigate IGA/SCC of lnconel 600 MA with limited efficiency
- Amine treatment or high pH has been widely used in the secondary water of PWR to mitigate FAC of carbon steel
- Chemistry has been permanently upgraded {NMCA) in US BWR to mitigate sec of core components.