ML20055D893

Fracture Mechanics Evaluation:Haddam Neck Pressurizer

ML20055D893
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	06/30/1990
From:	Palusamy S, Schmertz J WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML20055D881	List: B13564, Provides NRC W/Info Re Plant Pressurizer as follow-up to 900607 Meeting.Info Particularly Concerns Disposition of Three Indications on Pressurizer Inner Surface & Discussion of Resolution of Previous Indication ML20055D893 ML20055D929
References
MT-SMDT-276(90), NUDOCS 9007100122
Download: ML20055D893 (5)

Text

...

j's

~,.

• a.

+8 MT-SMDT-276(90)

FRACTURE MECHANICS EVALUATION:

HADDAM NECK PRESSURIZER W. H. Bamford Y.

S. Lee June 1990 Reviewed by:

(T

f. C. Schmertz

/

AY, As Approved by:

'S. S. Palusamy7 Manager Structural Mechanics and-Diagnostics Technology Westinghouse Electric Corporation Nuclear and Advanced Technology Division P. O.

Box 2728 Pittsburgh, PA 15230-2728 9007100122 90062?z13 PLIR ADOCK 05000 P

PDC

>.,4 FrCature Hochaal@O RvalCCtions-Baddas Rock Preocuriser i

The single-indication which was not acceptable to the standards of section XI, IWB 3500, was subjected to a fracture mechanics evaluation.

This evaluation was carried out using the methods and approach of

-Appendix A of Section XI.

The results were presented in the form of a handbook chart, prepared in the same manner of a number of previous submittals, e.g. [1].

The single indication which exceeded the standards

-was plotted on the Chart in Figure 1, and was found to be acceptable, without repair.

The actual deepest penetration into the base metal is 0.35 inches, which the clad depth has been determined to be about 0.40 inches. The flaw depth a/t has boen determined to be 0.75/5.9 = 0.127, while the flaw shape has been determined to be a/1 = 0.5.

Plotting this point on the chart, we see that the indication is acceptable by a large margin.

The flaw evaluation chart has been developed based on the operational transients for a modern pressurizer, which are both more realistic and comprehensive than those originally specified.

The transients are listed in Table 1, and include multiple cycles during heatups and cooldowns, to account for insurges, outeurges, and spray actuations.

The stress analysis has been adapted to account for the larger vessel thickness.($.5" vs the modern 3.5"), which lowers the pressure stress and elevates the thermal stresses. The fatigue crack growth and fracture evaluations have been carried out using state-of-the-art methods, similar to those used in Reference 1.

The likelihood of stress, corrosion or cracking occuring in the pressurizer has been shown to be very low, as discussed-in detail in the= Appendix.

Therefore, the indication has been shown to be acceptable by a wide margin, and therefore may remain in service without repair.

A detailed report providing the technical basis of the chart and the details of its construction is in preparation.

References 1.

Lee, Y. S. and Bamford, W.

H., " Handbook on Flaw Evaluation for Byron and Braidwood Units 1 and 2 Steam Generators and Pressurizers" Westinghouse Electric Corp.

WCAP 11063, March' 1986.

.f., 1. - ;,

TABLE 1 SUW4ARY OF PRESSURIZER TRANSIENTS GROUP #

TRANSIENT NO. CYCLES-1

.Heatup/Cooldown 200 2

Heatup 1/Cooldown 6 400 3

Heatup 2/Cocidown 5 400 4

Heatup 3/Cooldown 4 400 5

Heatup 4/Cooldown 3 400 6

Heatup 5/Cooldown 2 400 7

Heatup 6/Cooldown 1 400 8

Cooldown 7 1200 9

Unit Load /Unioad 36600 10 Group #1 4280 Loss of Flow large Step Load Decr.

Small. Step Load Incr.

Small Step Load Decr.

11 Loss of Load 120 Loss of Power 12 Reactor Trip

'400 13 Boron Concentration 36600 14 Inadvertent Auxiliary Spray 10 15 Primary Hydro 5

16 Primary' Leak 60 Turbine Roll 17 OBE 50 330eal11000:10..... _. _

,,,. I s \\.,.,

~

LtCE180

._{

ac b

f aw its.

e I cc table

'*$s[$@$$$$q$$$$@{@{h$$h U'=#'

$$MEWMB iMdHE

' =:'r'~

~

!,JiMMEMMMMMMM. EMn}

i 94 B

7

!,,U M M M E R M $ hf M E N E M h

!,$5pM$d4h0SJENEW 6

4

'MMR$lNEMdHMMlMM II -

y i I il 0

0.1 0.2 0.3 0.4 9.5 FLAW SHAPE (d).

Figure 1 Flaw Evaluation Chart: Circumferential Surface Flaws in the Shell of the Haddam Neck Pressurizer e

..N WSSTINGHoUSE CLASS 3 APPENDIX STRESS CORROSION CRACKING SUSCEPTIBILITY In evaluating flaws, all mechanisms of suberitical crack growth must be evaluated to ensure that proper safety margins are maintained during service. "

Stress corrosion cracking has been observed to occur in stainless steel in operating BWR piping systems; the discussion presented here is the technical basis for not considering this mechanism in the present analysis.

For all Westinghouse plants, there is no history of cracking failure in the reactor coolant primary loop.

For stress corrosion cracking (SCC) to occur, the following three conditions must exist simul'taneously:

high tensile stresses, a susceptible material, and a corrosive environment.

Since some residual stresses and some degree of material-susceptibility exist in stainless or ferritic steel, the potential for stress corrosion is minimized by proper selection of a material immune to SCC as well as preventing the occurrence of a corrosive environment.

The material specifications consider compatibility with the system's operating environment (both internal and external) as well as other materials in the system, applicable ASME Code rules, fracture toughness, welding, fabrication, and processing.

The environments known to increase the susceptibility of austenitic or ferritic steel to stress corrosion are oxygen, fluorides, chlorides, hydroxides, hydrogen peroxide, and-reduced forms of sulfur (e.g., sulfides, sulfites, and thionates). Strict cleaning standards prior to operation'and careful control of water chemistry during plant operation are used to prevent the occurrence of a corrosive environment.

Prior to being put into service, the system is cleaned internally and externally.

During flushes and preopera-tional testing, water chemistry is controlled in accordance with written specifications.

External cleaning for Class 1 stainless steel piping includes patch tests to monitor and control chloride and fluoride levels.

For preoperational flushes, influent water chemistry is controlled.

A-1 3453s/041290 to

A

~

.m.

.,~ _

z, := :

wesTIN0 MOUSE CLASS 3

,ac' 4

- g During plant operation, the reactor coolant system (RCS) water chemistry is monitored and maintained within very specific limit:

Contaminant concentrations are kept below the thresholds known to be conducive to stress-corrosion cracking with the major water chemistry control standards being included in the plant operating procedures as a condition for plant operation.

For example, during normal power operation, oxygen concentration in the RCS is expected to be less than 0.005 ppm by controlling charging flow chemistry and maintaining hydrogen in the reactor coolant at specified concentrations.

Halogen concentrations are also stringently controlled by maintaining concentrations of chlorides and fluorides within the specified limits.

This is assured by controlling charging flow chemistry and specifying proper wetted surface materials.

i

(

l l

l l

l L

A-2 3653s/061290 to

.p..,,:,

a Docket No. 50-213 B13564-Attachment No. 2 Haddam Neck Plant Pressurizer Flaw Evaluations by Northeast Utilities Service Company i

i June 1990 i