ML20012C974

Nonproprietary Rev 0 to Methodology for Identifying Potential Fluid Component Age-Related Degradation at Yankee Nuclear Power Station

ML20012C974
Person / Time
Site:	Yankee Rowe
Issue date:	03/31/1990
From:	YANKEE ATOMIC ELECTRIC CO.
To:
Shared Package
ML20012C971	List: ML20012C970 ML20012C974
References
YAEC-1727, YAEC-1727-R, YAEC-1727-R00, NUDOCS 9003260225
Download: ML20012C974 (40)

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I YAEC NO.1727 il-REVISION 0 MARCH 1990

I Il METHODOLOGY FOR IDENTIFYING POTENTIAL

[l FLUID COMPONENT AGE-RELATED DEGRADATION lg AT THE YANKEE NUCLEAR POWER STATION g

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YAEC No. 1727 Revision 0 March 1990 I

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Methodology for Identifying Potential Fluid Component Age-Related Degradation At the Yankee Nuclear Power Station I

Prepared by l

YANKEE ATOMIC ELECTRIC COMPANY I

580 Main Street Bolton, Massachusetts 01740-1398 l ~

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DISC 1 AIMER OF RPRPONSIBILITY I

- This. document was prepared by Yankee Atomic Electric Company

-(" Yankee"). The use of inf ormation contained in this document by anyone other I,

than Yankee, or the Organization for which this document was prepared under contract, is not authorized and, with resoect to any *=muthorir.ed use, neither Yankee nor its officers, directors, agents, or employees assume any obligation, responsibility, or liability or make any warranty or representation as to the accuracy or completeness of the material' contained in this document.

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ABSTRACT This report gives the methodology and key decision parameters used to predict the potential for fluid system pressure boundary age-related degradation. The methodology and key decision parameters for fatigue and wear-related mechanisms will be addressed separately.

-Many programs are currently in place to monitor and manage the offects cf fluid system pressure boundary degradation. - These include periodic ASME XI examinations, inspections for erosion / corrosion, eddy current exams of heat

'I-exchangers, hydrostatic and inservice leak tests, and others. These programs have demonstrated effectiveness in managing degradation and are continuously upgraded t'o meet anticipated needs based on-industry experience and research.

I For license renewal, the licensee is required to demonstrate the effectiveness of its programs in assuring a component's continued capability to perform its intended safety function. The demonstration must include an evaluation of the component's applicable degradation mechanisms.

Yankee has developed a personal computer (PC) based expert system to evaluate the Yankee fluid system components for potential age-related The expert system uses industry experience and research degradation.

information to establish a conservative logic and rule base for determining The expert the potential for degradation mechanisms acting on a component.

system accesses component databases to retrieve component material, process, and environmental data.

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-The information obtained from this expert system review is then

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-evaluated further to determine if the identified-degradation issue is real and if the current programs acceptably manage the issue. J.ugmentation of the current programs or other actions will be taken, as necessary.

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I IABLE OF CONTENTS I

hac DISCLAIMER OF RESPONSIBILITY......................................

11 iii ABSTRACT..........................................................

vi LIST OF TABLES....................................................

1 1.0 PURP0SE...........................................................

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g METHODOLOGY FOR IDENTIFYING AGE-RELATED DEGRADATION...............

2 2.0

_3.0 SCOPE AND LIMITATIONS OF REP 0RT...................................

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-4.0 IDENTIFICATION OF POTENTIAL AGE-RELATED DEGRADATION MECHANISMS 4

AND KEY DECISION PARAMETERS.......................................

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5.0 DESCRIPTION

OF DEGRADATION MECHANISMS.............................

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-5.1 General Corrosion...........................................

8 5.2 Microbiological 1y Influenced Corrosion......................

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5.3 Transgranular Stress Corrosion Cracking...........,.........

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~g-5.4-Intergranular Attack........................................

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5.5 Hydrogen Damage /Embritt1ement...............................

10 5.6 Selective Leaching..........................................

-g 5.7 Galvanic Corrosion..........................................

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5.8 Irradiation Assisted Stress corrosion Cracking..............

10 lJ 5.9 I r ra dia t ion Emb ri t t1emen t...................................

11 5.10 Thermal Embritt1ement.......................................

11 11 5.11 Crevice / Pitting Corrosion...................................

5.12 Erosion / Corrosion (Single Phase)............................

12 5.13 Two-Phase Erosion...........................................

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E 3 5.14 ~Intergranular Stress. Corrosion Cracking.....................

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6.0 KEY DECISION PARAMETER SCREENING VALUES...........................

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7.0 ASSUMPTIONS BY DEGRADATION MECHANISM..............................

14 7.1 General Corrosion Assumptions.............................

14 7.2 Microbiological 1y Influenced corrosion Assumptions........

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I 7.3 Transgranular Stress Corrosion Cracking Assumptions.......

15 7.4 Intergranular Attack Assumptions..........................

15 15 7.5 Hydrogen Damage / Embrittlement Assumptione.................

!I 7.6 Selective Leaching Assumptions............................

16 7.7 Galvanic Corrosion Assumptions............................

16 7.8 Irradiation Assisted Stress Corrosion Cracking 18

.l Assumptions...............................................

'N 7.9 Irradiation Embrittlement Assumptions..'...................

18 7.10 Thermal Embrittlement Assumptions.........................

18 18 7.11 Crevice / Pitting Corrosion Assumptions.....................

I 7.12 Erosion / Corrosion (Single-Phase) Assumptions..............

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. I TABLE OF C.QNTENTS (Continued) 1 19 7.13 Two-Phase Erosion Assumptions.............................

7.14 Intergranular Stress. Corrosion Cracking Assumptions.......

19 20 8.0 DEVELOPMENT AND REVIEW OF LOGIC DIAGRAMS.........................

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9.0 CONCLUSION

23 10.0 DEFINITIONS.......................................................

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11.0 REFERENCES

-ATTACHMENTS I

30 1.

General Corrosion Logic Diagram..................................

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31 2.

Microbiological 1y Influenced Corrosion Logic Diagram.............

3.

Transgranular Stress Corrosion cracking Logic Diagram............

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Intergranular' Attack Logic Diagram...............................

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' Hydrogen Damage / Embrittlement Logic Diagram......................

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Selective Leaching Logic _ Diagram..................................

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.Calvanic Corrosion Logic D1agram.................................

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Irradiation Assisted Stress Corrosion Cracking Logic Diagram.....

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Irradiation Embrittlement Logic Diagram..........................

38 39 10.

Thermal ~ Embrittlement Logic Diagram..............................

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Crevice / Pitting Corrosion Logic Diagram..........................

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Erosion / Corrosion (Single-Phase) Logic Diagram...................

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Wo-Phase Erosion Logic Diagram..................................

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Intergranular Stress Corrosion Cracking Logic Diagram............

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LIST OF TABLES.

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Humhgr 1

s Fluid, Component Degradation Mechanisms Covered L

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.In This Report 7-4-2.

Degradation Mechanism Key Decision Parameters-

~17 Material and Adjacent Material' Solution Potential Ratings

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1.0 H!RPOSE The purpose of this report is to describe the methodology and decision I

criteria used to review fluid system pressure boundary components for potential pressure boundary age-related degradation. Our intent is to demonstrate the acceptability of this methodology and obtain its approval f or use at the Yankee Nuclear Power Station.

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2.0 METHODOLOGY FOR IDENTIFYING AGE-RE1ATED DEGRADATION There are presently several industry and NRC-sponsored research programs directed toward component age-related degradation. The goal of these research programs is to increase power plant reliability and public safety by

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I improving component reliability. Yankee based its methodology for finding potential fluid component pressure boundary age-related degradation upon these I

research programs and Yankee's own operating experiences.

Listed below are the major tasks associated with this methodology:

Identification of potential degradation mechanisms (see Section 4).

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Identification of key decision parameters (see Section 4).

Development of key decision parameter screening values (see 3.

Section 6).

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Development and review of logic diagrams (see Section 8 and Attachments 1 through 14).

Yankee has developed a personal computer (PC) based expert system called CoDAT (Component Degradation Assessment Tool).

Its program code

' emulates the logic diagrams presented in Attachments 1 through 14 of this g.

The program accesses information contained in several component and-

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system environment databases to do component screening evaluations and re-evaluations, as necessary.

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'3.0 SCOPE AND LIMITATIONS OF REEDIT This report describes the screening evaluation process used to identify

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those fluid system pressure boundary components at Yankee that require

' detailed evaluations for age-related degradation. This report identifies the methodology and key decision parameters

• developed for the 20 degradation mechanisms listed in Table 4-1 (fatigue and wear mechanisms addressed separately). This report does not: consider routinely replaced fluid i

'I components (gaskets, packing, filter cartridges, etc.) or other nonmetallic 1

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The methodology contained within this report covers normal plant operations, only.' Transient conditions or abnormal plant operations are generally not significant from an age-related degradation perspective due to j

their infrequent and temporary nature.

If determined significant, however, they will be addressed. separately. Also, this report gives.no consideration to degradation caused'by abnormal stressors, such as design errors, I

fabrication defects,' improper welding, etc.

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IDENTIFICATION OF POTENTIAL Af;E-REIATED DECRADATION MECHANISMS AND KEY 4.0 IdCISION PARAMETERS I

Listed in Table 4-1 are the 20 pressure b'oundary age-related degradation mechanisms that could cause degradation of the fluid system I

components at the Yankee Nuclear Power Station. An EPRI Report titled, Component Life Est'mmt'.on:

IRR Etructural Materials

Dearadation Mechanisms,

NP-5461 (Reference 13; and Yankee's operating experiences were the primary pources for identification of the applicable mechanisms.

I After determining the potential degradation mechanisms applicable to the Yankee environment, Yankee performed a search of industry documents to I-gain'a better understanding of each degradation mechanism.

The search produced a list of documents that were helpful in prediccing degradation of These documents are listed in Section 11 of-this report.

fluid components.

This review also served to verify the applicability of the pressure boundary degradation mechanisms given in Table 4-1.

The Yankee operating environment does not support the existence of all the mechanisms listed in EPRI Report NP-5461. For example, Material Creep _

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will not' occur at operating temperatures less than 700'F (Reference 29).

Since the highest operating temperatures at the Yankee Nuclear Power Station do not exceed 660'F, Materini Creep is not a concern.

Other age-related degradation' mechanisms excluded from'this review are listed below:

1.

Thermally Induced Stress Relaxation (excluded by Reference 13).

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Irradiation Induced Stress Relaxation (occurs only inside reactor g

vessel - not within scope of this report).

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Swelling (occurs only in fuel elements - not within scope of this report).

Plastic Deformation (proper design and fabrication by ANSI b31.1 4..

prevents reaching yield point of materials).

'A key decision parameter is a material or environmental characteristic that by itself or with other key decision parameters provides definite exclusion or. definite inclusion of potential degradation mechanisms. The loS e diagrams (see Attachments 1 through 14) and Table 4-2 summarize the key.

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. decision parameters deemed important to the prediction of fluid component degradation.

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-TABLE 4-1 Fluid Component Derradation Mechaniams Covered In This Report i

. General Corrosion Erosion / Corrosion (Single Phase)

I Two-Phase Erosion i

Microbiological 1y Influenced Corrosion

~Intergranular Stress Corrosion Cracking Transgranular Stress Corrosion Cracking

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Irradiation Assisted Stress Corrosion Cracking Intergranular Attack Knifeline Attack Weld Decay 5

Crevice / Pitting Corrosion h

Thermal Embrittlement 885 F Embrittlement Strain Age Embrittlement l-Blue Brittleness Temper Embrittlement Quench Age Embrittlement Irradiation Embrittlement I

Hydrogen Embrittlement-Selective Leaching l:

Dezincification Graphitization Galvanic Corrosion oI I

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TABLE 4-2 i

Dagradation MechanismLKev Decision Parameters

' Environmental Parameters-e Process. Fluid Type.

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.. System Treated for'MIC l

Fluid pH Range:

Potential for-Impurity Concentration I,

Saturation Pressure Operating Pressure Maximum Temperature-j;

' Minimum Temperature.

X Fluid Velocity:

Lifetime Neutron Exposure

,1 Chemicals Added-to System i

Cathodic Protection Used i.

Fluid Chloride Content Fluid Fluoride Content I

Fluid Oxygen Content Fluid. Chromate Content Component-Insulated Stagnant Flow Conditions LI

Protective Coatings Used L

Buried Component Location Outdoors Material Parameters iR "ateriat cia==itication Galvanic Potential Rating

-gi Material Heat Treatment-Aojacent Material Classification I

-Material Solution Treatment Welded Component-Material Type Materia 1' Grade Material Copper Content Material Aluminum Content Material Carbon Content' I

Material' Molybdenum Content

' Material Ferrite Content Material Zine Content I

' Material Chromium Content

' Material Yield Strength Material Cladded

. Material Hardness

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1 5.0 DESCRIPTibN OF DEchinAT10N MECHANISMS This section of the: report presents a brief description of the applicable Yankee Nuclear Power Station pressure boundary age-related degradation mechanisms. For a more detailed description, refer to the specific-logic diagram in Attachments 1 through 14 and the references given on

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'the logics.-

5.1 General Corrosion I

General Corrosion occurs to some extent in all metals.

Still, a recent-study done for the Electric Power Research Institute (EPRI-Report NP-5461, Reference 13) suggests only certain materials are significantly influenced by Listed below are the materials that may be influenced:

Ceneral Corrosion.

I Carbon Steel-Cast Iron Ferritic' Stainless Steels Low Alloy Steels Martensitic Stainless Steels Aluminum I

The concerns with General Corrosion are thinning of the pressure boundary wall beyond code allowable and exceeding the component's' allowable The rate of thinning.due to General Corrosion can be_ predicted.

stress..

Other nonuniform types of corrosion can occur with General Corrosion.

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such degradation mechanism is_ Erosion / Corrosion. Section 5.12 gives a discussion on Erosion / Corrosion.

5.2 Microbiolonically Influenced Corrosion I

The corrosion rate of 'a material can be accelerated by microbiological This acceleration in corrosion is due to the severely corrosive activity.

Some of these environment resulting from micrcbiological waste products.

The bacteria require oxyge, to survive and colonize, while others do not.

I most. common bacteria associated with Microbiological 1y Influenced Corrosion MIC is (MIC) are sulfate reducers and sulfur, iron, and manganese oxidizers.

usually restricted to systems'that contain river, lake, potable, or sea water.

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'5.3 Transaranular stress cerrosion cracking The aggressive attack of halogens (chlorides, fluorides, etc.) on a sensitized austenitic stainless steel component causes Transgranular Stress-Corrosion Cracking (TCSCC). TCSCC results in cracks proceeding across the

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material grain boundaries.through slip planes. An environment containing amonia causes another form of TGSCO to occur in copper alloys. This type of I

TGSCC, sometimes called ammonia grooving, is most prevalent in'feedwater heaters and condensers containing admiralty brass tubes that use hydrazine (amonia) as a secondary chemical additive.

'5.4 Intergranular Attack Intergranular Attack (IGA) results in localized corrosion at or near the grain boundaries.

Intergranular corrosion can be caused by impurities, enrichment of one alloying element, or depletion of one alloying element in I-IGA usually occurs in harsh acidic environments.

the grain boundary areas.

Knif eline Attack, which is one form of Intergranular Attack, occurs in It is stabilized austenitic stainless steels in'the-heat affected zone.

Knifeline Attack can occur caused by the depletion of alloying elements.

because of improper heat treatment after welding. Weld decay, which is another; type of Intergranular Attack, occurs in nonstablized, sensitized austenitic stainless steel. 1,owering the material's carbon content reduces

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_the likelihood of weld decay.

5.5 Hydronen Damage /hbrittlement Hydrogen Embrittlement occurs because of atomic hydrogen, produced during all corrosion processes, becoming trapped within a material's lattice The trapped hydrogen often prevents plane slippage, which structure.

decreases the toughness of the material. Hydrogen Embrittlement can increase the potential for cracking.

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Atomic hydrogen also can cause Hydrogen Damage. However, it usually occurs-in lower strength meterials and results in blistering of the material instead of cracking.

5.6 Selecti' e Leachine

' Selective Leaching is a corrosion process that results in the removal

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Graphitization and Dezincification.

I Graphitization occurs when a corrosion process removes the iron matrix from a component fabricated of gray cast iron. The leaching removes the fron leaving behind the insoluble graphite, which lacks strength. This process only occurs under harsh conditions (i.e., buried piping).

Dezincification is the selective removal of zine from brass A harsh-environment and zine concentrations greater than 207,can components.

result in dezincification of brass.

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5.7 Galvanic Corrosion l

Galvanic Corrosion is a process that occurs between electrically connected dissimilar metals.

It results in an increased corrosion rate of the L

more anodic material-and a decreased corrosion rate-for the cathodic material.

Galvanic Corrosion progresses rapidly in process fluids that have lg

'W high conductivities such as sea water.

In good quality water, where the conductivity is much lower, the process may occur but it would impact a much smaller area and occur at'a slower rate.

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5.6 _ Irradiation Assisted Stress Corrosion Orackine-Irradiation Assisted Stress Corrosion Cracking (IASCC) results in

..I' material cracking that follows the grain boundaries'. -It is different from L'

Intergranular Stress Corrosion Cracking (IGSCC), discussed later in this I

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report, because'all that is necessary is a high fluence of ionizing radiation in an oxygenated water environment. Austenitic stainless steel, Inconel and Monel are the materials susceptible to IASCC.

I 5.9 -IIIAdiation Fmbrittlement Neutron radiation causes Irradiation Embrittlement. The amount of embrittlement increases with increasing exposure, but is insignificant below 1 x 10 neutrons per square centimeter. This embrittlement process causes a decrease in the material's toughness and promotes cracking.

5.10 IhtImal Fabrittiement

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Thermal Embrittlement also results in a significant reduction of the material's toughness.

There are several types of Thermal Embrittlement: 885'F Embrittlement of cast austenitic stainless steels, Temper Embrittlement, Strain Aging Embrittlement, Quench-Age Embrittlement, and Blue Brittleness..

The type of embrittlement experienced is dependent upon the material, special treatments done to the material during fabrication, and the system operating I

temperature.

5.11 flevice/ Pitting Corrosion Crevice / Pitting Corrosion results in a very localized corrosion.

It occurs in stagnant or low flow areas that allow material or environmentally produced impurity concentrations. The impurity concentration may be caused by alternate wetting and drying on the component'a surface, by precipitation of a chemical species, or the collection of insoluable impurities found in fluid I

systems. Crevice Corrosion, as ths name implies, occurs in crevices, such as those formed between a flange face and its gasket. Pitting Corrosion usually

-occurs on the lower surface of horizontal runs of piping or other fluid component surfaces that allow the collection of impurities.

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U 15.12 Erosion / Corrosion (Sinnie Phase)

Erosion / Corrosion (E/C) results in the physical loss of fluid component material. The material loss is the result of the relative movement between a 1

single-phase process fluid and the material. The rate of other corrosions can i

influence Erosion / Corrosion.

Erosion / Corrosion is characterized in appearance by grooves, gullies, rounded holes, and valleys and usually exhibits a directional pattern.

Erosion / Corrosion may be found in systems containing liquids (Surry incident) k-or a vapor, such as steam. A system's geometry, temperature, fluid oxygen content, and fluid velocities influence the rate of the E/C mechanism, 5.13 Two-Phase Erosion t

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Two-Phase Erosion, like E/0, is the physical loss of material due to the relative motion between the component aad the process fluid..Still, in Two-Phase Erosion, the vapor portion of the process fluid causes very high L

velocities in the liquid portion. Therefore, Two-Phase Erosion can cause

' quicker deterioration of the material. Two-Phase Erosion also generally exhibits directional flow patterns.

5.14 Interrranular Stress Corrosion Cracking Intergranular Stress Corrosion Cracking (IGSCO) occurs in austenitic stainless steels when chromium carbides form in the grain boundaries of the material. Chromium carbide formation depletes the chromium concentration 1

around the grain boundary and reduces the material's resistance to localized I'

corrosive attack. The cracking process, as the name implies, proceeds along-p I

the material grain boundaries. Improper welding or cooling can produce internal-stresses that cause IGSCC. Corrosive environments, such as process fluids containing halogens, accelerate IGSCO. IGSCC also occurs in Inconel I

through a process similar to the process that occurs in austenitic stainless steel. Like TGSCC, environments containing mannonia also can cause IGSCC in copper alloys. l 8461R

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6.0' KEY DECISION PARAMETER EnRK5NING VALUES A thorough review of the references listed in Section 11 of this report resulted in identification of the key decision parameter screening values for each_ degradation mechanism. ' Therefore, this report is a sunnary of those

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references. Where the key decision parameter screening values were not definitively given in the references, taking an appropriately conservative view of the degradation mechanism allowed Yankee to assign,these values.

These conservative' assignments are identified as assumptions in Section 7 and also are listed on the logic diagrams given in Attachments 1 through 14.

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E 7.0 ASSUMPTIO!iS_)Y DECRADATION MECHANISM Provided below are the major assumptions used in the development'of the' logic diagrams (see Attachments 1 through 14). These assumptions are identified on the specific logic diagram as A1, A2, etc.

General Corrosion Assumotions (see Attachment 1)-

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Unless'specified otherwise (e.g., Selective Leaching of cast iron),

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low alloy steel and cast iron degrade in the same manner as the

'.5 material classification carbon steel. This assumption is conservative because the alloying elements making up low alloy steels improve corrosion resistance. Also, cart iron has been used extensively in buried conditions because of its resistance to soil corrosions.

A All thermal Insulation systems may allow the intrusion of 2.

moisture. Therefore, all insulated components are subject to General Corrosion under the insulation provided the system temperature is lower than the building average temperature and the fluid is not stagnant.

3.

No credit is taken for protective coatings.

4.

The relative humidity is assumed to be 100%. This results in a dew--

I point temperature equivalent to the building temperature.

7.2 ' Microbiologically Influenced Corrosion Annuentions (see Attachment 2)

All buried fluid components (except titanium and concrete) are

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susceptible to MIC (References 14 and 38). This assumption is conservative because MIC requires moisture (as generally associated with a high water table) to survive. Most fluid system components at Yankee are installed above the water table.

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Systems containing quality water and fluids derived from quality water (steam systems) are hydrostatically tested with quality water

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'h* "** " ' **Perience MIC. Yankee operating.

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5' practices provide the basis for this assumption.

3.

Process fluids that normally do not contain moisture will not 4

support MIC organisms. Although MIC can colonize very quickly when moisture is available, they will die or go dormant without a constant moisture source (Reference 12).

7.3 Transgranular Stress Corroalon Assumptions (see Attachment 3) 1.

As with'other corrosion processes, TGSCC is not likely without a good conducting electrolyte (Reference 17, Page 45).

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-7.4 initIgranular Attack Corrosion Assumptions (see Attachment 4)

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Since the production of steam is a purifying process (water vapors form without insoluble impurities), IGA is not likely in the Yankee steam systems (Reference 20 Page 15-13).

2.

As with other corrosion processes, IGA is not likely without a good conducting electrolyte (Reference 17, Page 45).

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Since most of the laboratory tests use acids to determine if IGA is a concern (Reference 9, Page 187), an assumption can be made that the mechanism is partially based on exposure to acidic pHs.

Further studies by Yankee in 1990 should confirm this assumption.

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7.5 Hydronen D---ee/F=hrittlement Assumotions (see Attachment 5)

For normal PWR operating conditions, Hydrogen Attack (caused by the' 1.

disassociation of hot hydrogen gas) is not a concern (Reference 19, Page 143).

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Cathodic protection can cause Hydrogen Damage / Embrittlement because 2.

of the potential to overcompensate'for the voltage required to minimize other corrosions. Since the voltage potential for cathodic protection is closely monitored, this is a conservative assumption.

3.

Hydrogen Damage / Embrittlement is significant in corrosive It environments, such as exist in untreated raw or potable water.

may also be significant when lubricating fluids have corrosive chemical additives (Reference 15, Page 66).

1 7.6 Selective Leachine Assumptions (see Attachment 6) i 1.

As with other corrosion processes, Selective Leaching is not l

8 possible without a good conducting electrolyte (Reference 17, Page 45).

2.

All concrete undergoes Selective Leaching. This is conservative ij because not all concrete is exposed to moisture, which is~ required l

for. Selective Leaching (Reference 17, Page 135).

I 7.7 Galvanic Corrosion Assumptions (see Attachment 7) i 1.

References 19 and 21 identify the galvanic series for typical metals. The tables in these references provide guidance for

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determining the potential of Galvanic Corrosion. Based upon these tables, a ranking (see Table 7-1) was made using the

-j It is classifications of materials described in this report.

assumed that although some galvanic potential exists with an issnediately adjacent (in the table) material, the af fect is small in high quality, monitored process fluids.

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TABLE 7-1 a

Hattrial and Adiacent Material Solution Potential Ratinen j

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' Material or Material or Adjacent l}

AdjtCEnt Material-

'Materini Ratine (Reference 19)

'g GRAPHITE 1

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TITANIUM 2-l HASTELLOY C 3

AUS SS' 4

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TER SS' 4

. MAR SS 4

CARP.20-4 1

l; INCONEL 5

.i MONEL 6

'C0FFER BASED 6

lg l?4 HASTELLOY B 7

NI RESIST 8

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CARBON STEEL 9

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CAST IRON 9

LOW ALLOY STEEL' 9

ALUMINUM 10 ZINC 11

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w 7.8 Irradiation AasiatrA strema corremf on crackinn Ana*==ptinne j

(see Attachment 5) i 4

I None.

7.9 IIIAdjgtion rakrittlement Anaumptions (see Attachmer.t 9) i None.

7.10 Ihrrmal e-brittlement Assumplinns (see Attachment 10) 1.

It is assumed, by the nature of production of a cast stainless I

steel component, that calculating the ferrite content using the l

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.Schaffler Diagram (used to calculate the' ferrite content of deposited weld metal) represents the actual ferrite content in the

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l casting. Further studies by Yankee in 1990 should confirm this assumption.

7.11 Crey.lce/ Pitting corrosionJLsaumplions (see Attachment 11) 1.

Unless specified otherwise (e.g., Selective Leaching of cast iron),

i low alloy steel and cast iron degrade in the same manner as the-classification carbon steel. This assumption is considered conservative because the alloying elements making up low alloy l

steels improve corrosion resistance. Also, cast iron is used 1

extensively in buried conditions because of its resistance to soil corrosions.

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'w 2.

As with other corrosion processes, Crevice / Pitting Corrosion is not likely without a good conducting electrolyte (Reference 17 Page 45).

3.

No credit is taken for protective coatings.

a

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7.12 Erosion / corrosion (single-Ihae) Amaumptions (see Attachment 12) l 1.

It is assumed that system geometry will always support I

Erosion / Corrosion.

2.

Aluminum and concrete are assumed to experience Erosion / Corrosion.

3.

Fluid velocities for all in-line fluid components, except tanks and heat exchangers, are the same as the piping in which they are located. Velocity assignment for tanks and heat exchangers is by reference. Turbulent flow in pumps and valves may af fect their velocity assignments. However, current surveillance practices 8

morsitor ior the affects of high velocities in these components.

7.13 h o-Phase _ Erosion _ Assumptions (see Attachment 13) 1.

If the saturation pressure is within $1 of the operating pressure, the potential for the fluid to become two phase, due to system pressure losses, is high enough to consider the fluid as two phase.

7.14 Interar. anular _.Sitess_COII.011on_AsAumplions (see Attachment 14) 8 1.

As with all other corrosion processes, IGSCC is not likely without I,

a good conducting electrolyte (Reference 17, Page 45).

2. 'Any exposure to phosphate / sulfate chemistry control can lead to IGSCC of Inconel (References 13 and 16).

I If the Inconel was heat treated or the austeuitic stainless steel 3.

was solution treated, it is assumed to have been done af ter any I

shop welding. Therefore, only Liald welding could change the properties developed by heat treating or solution treating the material.

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8.0 MYE1SfMENT AND REVIEW OF LOGIO DIAG),& tis The logic disgrams in Attachments 1 through 14 were developed from the i

references identified in Section 11 and the assumptions listed in Section 7.

The top-down logic diagram approach provided a consistent method of handling the wide range of materials and environmental conditions that exist in the r

Yankee. fluid systems.

Each question on the logic diagram identifies one or more key decision parameters and their screening values.

i Development of the logic diagrams included completing the following tasks for each potential degradation mechanism:

1.

Determining the order in which the questions should be asked. The order is based on a prioritization of the key decision parameters.

L Their prioritization is based upons The key decision pe eeter's ability to singularly provide a a.

l conclusion, and I

b.

The key decision parameter's dependance on the values of other key decision parameters.

2.

Ensuring that each question answered "YES", "NO", or " UNKNOWN" directs the evaluator to the appropriate conclusion.

i 3.

Ensuring that each key decision parameter screening value lists a reference and any assumptions used in its development.

4.

Ensuring that each of the material classifications and procesa l

fluid types (see definitions, Section 10) are properly covered on I

the logic diagram.

l lT 5.

Ensuring that material classifications and process fluid types not meeting the descriptions above reach a conclusion of " RULES I

REQUIRED."

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The development and review of these logic diagrams are documented in I<

accordance with Yankee's Engineering Manual.

Included in the review is an independent review for technical adequacy and the basis for all assumptions.

I This independent review was done by Stone and Webster Engineering Corporation material specialists.

The conclusions that can be reached on the logic diagrams are described below No Issue

- Degradation mechanism does not significantly I

impact component reliability.

Issue

- Degradation mechanism may significantly impact component reliability.

Data Required - Information required to complete evaluation is not available.

I Rules Required - Description of the specific component material or its environment is missing in the decision w

criteria.

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9.0 CQ!iCLUSION i

I This report describes the basis for the screening evaluation I

methodology used by Yankee to identify fluid system pressure boundary f

components that require further evaluation for age-related degradation. This

[

report also provides a brief description of the expert system (CoDAT). CoDAT f

emulates the screening criteria and, based upon that criteria, predicts the likelihood of age-related degradation.

Further evaluations are scheduled for those components having a I

potential for_ age-related degradation. These evaluations will include an assessment of the effectiveness of current plant programs to monitor and manage degradation. The evaluations also may include one-time examinations to coniirm the presence'of potential age-related degradation. Depending upon the evaluation results, program upgrades may be implemented.

Components found not to be subject to age-related degradation will not j

I be reviewed further for license renewal. However, coverage by any existing programs will continue.

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10.0 DIT.lE1710HS I

Provided below are the definitions of terms used in this report:

[

Abnormal Sinssors Abnormal stressors are environments and service l

conditions caused by design errors, f abrication defects or improper installation, operation, or j

maintenance (including excessive testing).

Active Compgn al A component (or part within a component) expected j

I to move to function properly.

AdjattaLtialerial Any material that is in contact with or electrically connected to the evaluated material.

E Agins Aging is the net destadation in the physical I

condition of a component, system, or structure due to its environment and service. Aging can result in the degradation of a component, system.

l r

or structure's capability to perfonn its intended function af ter being placed in service.

Age-Related Degradation Age-related degradation is the change in the physical properties of a component. system, or structure caused by aging (such as crack gianth.

loss of ductility, fatigue capacity and mechanical or dielectric strength reductions).

Aging Streason The environments and service conditions that produce age-related degradation (e.g., beat, radiation, humidity, reactive chemicals, operational cycling, electrical / mechanical loads, s

vibration, testing).

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Antied Buried in earth or other substances that can contain moisture or chemical impurities.

)

i compenent Material One or more of the following material classifications (this list also applies to adjacent material):

i i

Carbon Steel Low Alloy Steel Cast Iron Copper Alloys Ferritic Stainless Martensitic SS Steel (SS)

Austenitic SS Titanium

[

Aluminum Concrete I

i Monel Inconel I

Degradation Mechanism Degradation mechanisms are the physical or chemical processes (such as wear, erosion, and corrosion) that result in aging degradation.

Dr.itd Air Air that bas gone through an air drier.

l Imourity concentration The ability for concentration of impurities due l

Fotential te alternate wetting and drying of a component's l.

surface or condensation and collection of low quality steam.

l Kev Decision Parameter A particular material characteristic or environmental parameter that causes or prevents degradation of a component for a specific degradation mechanism.

Low A11ov Steel An iron based material with alloying elements added not to exceed approximately 5 percent of the total (i.e., Cr, Mo, etc.).

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A process done to develop mecha.nical properties hierial Heat of materials.

Irattaeni

'I The potential voltage difference of a material.

Naterio? Solution as compared to hydrogen, used to predict the' 2s.tential I

occurrence of galvanic corrosion, hierial solution A process done to desensitize sensitized austenitic stainless steel.

Treatment I

Normal stressors are the actual environments and Nelmal_hrmassrs service conditions (including upset conditions) 1 axperienced by a component that has been properly designed, f abricated, installed, operated, I

i tested, and maintained.

A classification of fluid types taken from one of Ernctss Fluid Typs those listed below

- I Raw Water Quality Water Potable Water Saturated Steam 1

Wet Steam Two Phase Air Dried Air j

I Purifled Oil Fuel Oil Nitrogen Hydrogen j

A domineralized or distilled water source Quality Water monitored to ensure purity.

Water taken from an essentially untreated ff Raw _ Water Water sources that fall within this source.

category are lakes, rivers and ponds.

fg s-A component fluid condition that describes a j

Ragnant f

component under no flow conditions. -

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I TVo-Phase Fluids A fluid derived from quality water that operates i

or has the potential to operate in two phases.

Extraction steam, which usually contains j

moisture, or a fluid that has dropped below its saturation pressure are examples of two-phase i

fluids.

~

I A plant or system operating condition considered Deset condition not nomal but may occur once or twice a year.

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11.0 REFERENCES

1.isted below are the references used to develop this report and the logic. diagrams:

1.

Yankee Rowe Pipe Claan Specification, YS-497, Revision 1 l

2.

Ensint.tIina Materials and Their Applications, Richard A. Flinn and I

W Paul K. Trojan, Copyright 1975 by Houghton Mifflin Company.

3.

Nuclear Steam Supply Evittag Chemistry Manual, CENPD-28, I-Revision 2. Combustion Engineering Power Systems.

4.

Erosion-Corrosion Experimenta and Omleulation Model by W. Kastner, Kraftverk Union AG, presented at an EPRI sponsored i

Erosion / Corrosion Program April 1987.

5.

tianua Lior_.Ptie rmin in g _1he_Essaining_Et rana t h_o L_ Corr o d e d Pipelinea, a supplement to ANSI /ASME B31 Code for Pressure Piping.

ANSI /ASME B31G, 1984.

6.

Yankee Plant Erosion / Corrosion Program Results, YR-W1-15, Hor);

inE.tIUC11on_for InIpection_of Secnndary Plant Piping ior Ernalon/Correalon, Revision 1.

{

7.

Yankte Technical _.Specificatiom including Change No. 113. Technical Bases Section 3.4.6.

8.

NUREG-10il, Volume 1.

9.

titiallurgy of Welding, by J. F. Lancaster, 1980.

I

10. Corrosion-Related Failures in Feedwater Heaters, B. C. Syrett, EPRI l

l-Report CS-3184 July 1983.

Staam Pi insi Caust1_And

11. ErnaionLC.cIIcalon in Nuclear Plant S

Inspag.tlen Program Guidelinas, N. S. Hirota, EPRI Report NP-3944, April 1985.

12. /L. Study. of Microbiologica11v InLusaced. Corrosion _in_ Nuclsar_foEtt I

Planta mud a Practical Guide for Countermeasures, D.

Cubicciotti, EPRI Report NP-4582, May 1986.

13. Component Life Estimation: IMR Structural Materials Degradation e

Mechmai===, M. E. Lapides, EPRI Report NP-5461 September 1987.

l

14. Microblal corrosion in Foamil-Fired Power Planta - A Study of Microbioloeically Influenced Correalon and a Practical Guide for I.'

November 1987.

Ita Treatment and Prevention, J. A.

Barts, EPRI Report CS-5495 84b1R I

I

15. Environ==ntal Effects on Ca=nonentar C - ntary for ABME section III, S. W. Tagart, Jr., EPRI Report NP-5775 Areil 1988.

16. ftsattdings t Workshop on IDiliation of Stress _CDIrDUDn_CIaChing Under IMR Conditions, D. Cubicciotti, EPRI Report NP-5828, May 1988.

17. Corrosion Control in the Chemical Process Industries, by C. P. Dillon, Copyright 1986 by McGraw-Hill, Inc.

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18. Correalen Data Survey, National Association of Corrosion Engineers, Copyright 1974.

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19. Cntrosion Engineering by Mars G. Fontana, Copyright 1986 by McGraw-Hill, Inc.

l L

20. Metals Handbook __ Desk Edition, by the American Society For Metals, Copyright 1985.

I

21. Calvani d orrosion - Electrochamleal Theory of Calvanie CorrosioDs by-Harvey P. Hack, editor, Copyright by American Society of Testing and Materials, 1988.

22. 1987 EPRI Workshop on Secondary - Side Intergranular Corrosion l

Mechanisms! Proceedings, J.P.N. Paine, EPRI Report NP-5971, Volumes I and II, April 1987.

23. HUREC/CR-4652. Concritt_Copponent_ Aging And Its_.31gniligants Eglative to Life Extension of Nuclear Power Plants.

I-.

24. LWR Experience With Centrifuga11v Cast Stainless Steel Pipe, S. N. Liu. EPRI Report NP-4996-1.te, December 1986.

25. Stress Corrosion Cracking of A11 ova 600 and 690 in All - Volatile -

D ated Water at Elevated Temperatures, by C. E. Shoemaker, EPRI Report NP-5761SP, May 1985.

26 1DCFR50 Appendix C. Fracture Tonehness and Appf;. dix H. RametDr Vessel Material Surveillance Pronram Reanir-nts.

'I

27. Regulat.ory Culde 1.99. Revision 2. Radiation Bahrittlement of Eggetor Vessel Material.

28. VP-EXPERL f/11..nmaed Expert svatem Develonment Tool, by Brian Sawyer, Published by Paperback Sof tware International 1987.

29. ARME section III, Paragraph 2110c, 1983.

30. Corrosion Of Stainless Eteels, by Sedricks, John Wiley & Sons.

31. Materini Specification For A11ov X-750 in IRR Internal Ca=aonents, EPRI Report NP-6202, January 1989.

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32. Proceedinant 1985 Workshop On Primary Elde Strema Correalon I

Crackinn of PWR Steam Generator Tubine, EPRI Report NP-5158, j

)

June 1987.

33. Optimir.ation of Metallurnical Variables To f= proper CorIn&inD Resistance On inconel A11ov 600, EFRI Report NP-3051, July 1983.

34. Mechani--- of Stress corrosion Crackine of A11ov X-750 In Blah I'

Purity Water, by C. A. Grove, L. D. Petrold, Symposiur.I n Nickel O

Based Alloys ASM, Cincinnati Ohio, October 1984.

35. J.nAulation Desian Practices For Mitimation Of Ploe And Eauinment Corrosion, by J. B. Bhsyson of Lumous Crest, Inc. Presented at the NACE Conference in New Orleans, April 1989.

I

36. The Corrosion Handbook, by M. H. Uhlig J. Wiley & Sons, 1948.

i i

37. EracitAings:

1986 Workshop On Advanced Blah Strenath_Mg:erials, I

EPRI Repor NP-6363, May 1989.

38. LL Corrn11on B7. The Influentt_0f_Sulphalt_EsAuring_ Bacteria On g'g Hydrogen Absorption by Cathodically Protected Steel, by M. J. Robinson, et al.

i

39. Microbial

Dearadation of Pjarine Lubricating oil,

j' R. A. King, et al., The Institute Of Marine Engineers, 1976.

40. Corrosion Data Survey. Metals Section, NACE, 1981.

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41. HRC Inf2IIpation Notice No.86-116. Supolement 3 -Teedwater Line Break, November 10, 1988.

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I ATTACIEMENT I i

General corrosion Irmie Diantam

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P.

ATTACIRMENT 2 g,terebiolonically influenced corrosion ionic Dimeram I

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l ATTACllPIENT 4 I

-interaranular Attack haie Dimyram

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ATTAC1 DENT 7 Calvanic Corrosion 1 male Dimatas 4

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ATTAcMMENT 11 i

i CrevicdPitt4ne Corroainn bgle Diagr a I

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ATTACIDGENT 12 l

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'I-ATTACIDENT 14 A gggranular Str. gas._ Corrosion Crack 4ne immie Dimeram i

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