ML20234D487

Rev 0 to Departmental Instruction 1-ENG-6.09, Balance-of- Plant Piping Inservice Insp Program

ML20234D487
Person / Time
Site:	Millstone, Haddam Neck, 05000000
Issue date:	07/06/1987
From:	NORTHEAST UTILITIES
To:
Shared Package
ML20234D443	List: A06665, Forwards Response to NRC Bulletin 87-001, Thinning of Pipe Walls in Nuclear Power Plants. Util Intends to Meet NUMARC Guidelines on Pipe Wall Thinning in high-energy Piping Sys ML20234D464 ML20234D474 ML20234D487 ML20234D504 ML20234D512
References
1-ENG-6.09, NUDOCS 8709220105
Download: ML20234D487 (11)

Text

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,T0: DISTR:5. !;N DEPARTMENTAL h INSTRUCTION NO.-1-ENG-6.09 FROM: d' i -,

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REVISION 0 DE TWINT HEAD DATE 7/06/87

SUBJECT:

BALANCE OF PLANT PIPING INSERVICE PAGE 1 of 5 INSPECT:GN PROGRAM

1. PLRPOSE This instruction implements a prc; ram for determining the -

status and prediction of integrity for balance cf plant piping.

2. DISCUSSION 4 The failure of the main feedwater system piping at Surry Unit 2 from erosion / corrosion res;1ted in personnel injuries including four fatalities. Review of programs.

verified that weld and pipe exami ations have never been performed on similar piping at MP-1. An informal' inspection program had been ongoing in systers identified as high pipe thinning areas which were to: phase flow regions, su:h as extraction steam.

As information became available t e specific mechanism for tra Surry mechanism were identif f t:. Contributors. include:

1) fluid temperature, 2) oxygen ::-. ant, 3) flow patterns .

at: velocity, 4) geometry, 5) sus:i:tible ' pipe material, and 6) steam quality,- It is rec:;*':ed that' other mechanisms fcr pipe thinning exist and tha: the plant ages, it wi'l be necessary to identify ha :-are for early replacement g to prevent. losses in availability  : -d to ensure personnel Ea#ety, m

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INSTR.CTIONS

~ 3. 1 3.1 The Engineering Supervisor is responsible for seministrating the program.

A pre-outage inspection' list will be developed.

3. 2 3.2.1 . 5ystem conditions shall be identified and a list of potentialsproblem areas will be #

predicted using Generation Engineering wear.

models (MIT or EPRI).

NOTE:

The system list will only be required initially unless system conditions change. When sufficient'-

data points are identified, then f the mode 1~will be used for total

$. wear predictions. )

.Ij 3.2.2 Based upon plant records, INP0 reports, l i

NRC information, NUSCo input and plant drawings, inspection plans will be' developed.

3.2.2.1 All susceptible locations will be evaluated for inspectionj priority based upon: 1) personnel safety, Personnel l

2) plant availability. i safety takes precedence over plant availability if. resources are limited.

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NOTE: Initial runs of the MIT model indicate. highest }

il- susceptibility downstream of HIP heater (FW and f

HD). Personnel safety issues require inspection of piping in the feed pump alley to be high )

priority.

3.2.2.2 Chose the ten (10) most susceptible l locations from the list chosen in l Step 3.2.2 above, plus an f additional 5 (five) locations for initial sample. Subsequent sampling will be modified based upon initial results. Locations

() and intervals will vary.

orming applicable test or inspection.

Data collection will be through visual internal examination or pipe wall thickness measurement.

Visual examination will indicate whether wear has been experienced. If wear has been experienced, then the use of thickness measurement will be evaluated.

.1 Visual Internal.

3.3.1.1 OPEN an accessible portion of the system.

3.3.1.2 Use sufficient lignting on equipment such as fiber optics or a boroscope to examine G internal pipe.

3.~ Record resu :: : r. A::achment 1.

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l 3.3.2 Ultrasonic Test. ]

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Select spots on pipe walls downstream of j 3.3.2.1 elbows, flow changes, discontinuities j l

and turbulence. i

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Determine thickness using ultrasonic 3.3.2.2 l methods. 1 I

j 3.3.2.3 Use grid methods where applicable in j

order to provide reTerence to inspection points.

7 NOTE:

When identifying spots for f

reinspection, select previous l

spots in order to collect data f

for wear rate prediction, fg v

.t 3.3.2.4 Acceptance is defined as Tnom - Total Wear > Code allowable + 10% projected through the next cycle. Wear Rate =

Total Wear =

(Tnom - Tmeasured)/ Time.

(Wear Rate) x (Time). I NOTE: Tnom is defined as the ncminal pipe wall thickness.

3.3.3 Hydrostatic Test.

3.3.3.1 When required, at the direction of the Engineering Supervisor, a hydrostatic test may be performed.

3.3.4 Br, sed upon the above results, trouble reports shall O)

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be initiated and corrective action taken.

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3.3.5 Sample Expansion - If locations are discovered which l will exceed Tmin + 10% over the next cycle, then the

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sample plan will be revised to include ALL of the $

similiar highly susceptible locations.

3.3.6 Records will be retained as part of this program by  ;

the Engineering Department. i EA:1fg

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Attachment I r.

BALANCE OF PLANT WEAR PROGRAM CATA SHEET { '

I SYSTEP LINE N0, MAT'L SIZE MATERIL.

PROD FORM OATE METHOD: VISUAL

• THICKNESS HYORO

• For :-ickness measurement attach Data Sheet Irit. Number Calibrated MINIMIF MEASURED THICKNESS AVERAGE THICKNESS MINIMUM WALL THICKNESS PREDICTED TIME TO REACH MINIMUM WALL THICKNESS **

• • If required i

SKETCH:

(Note dimensions or indications of wear)

(Indicate direction of flow) ,

HYORO ??.E55URE (If applicable)

RESULT:

Engineer

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Docket No. 50-336 A06665' 1

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l Attachment 3 i

Response to NRC Bulletin-87-01 Millstone Nuclear Power Station, Unit No. 2 i

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September 1987 1

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NRC ACTIONS / QUESTIONS

1. Identify the codes or standards to which the piping was designed and fabricated.

NNECO Response:

The sections of piping in the main steam, feedwater, and blowdown between the steam generators and.the outside containment isolation valves are designed to ASME B. & P . V.

Code Section III, Class 2. All other portious of these systems are designed to ANSI /ASME B 31.1.

2. Describe the scope and extent of your programs for ensuring that pipe wall thicknesses are not reduced below the minimum allowable thickness. Include in the description the criteria ,

that you have established for: 1

a. selecting points at which to make thickness measurements i

b. determining how f requently to make thickness measurements l

c. selecting the methods used to make thickness measurements i

d. mak ing replacement / repair decisions  ;

NNECO Response:

NNECO Procedure EN 21153, " Thickness Testing of Secondary l Piping ," is used to survey the condition of secondary piping '

systems which is provided for your information.

l The extent of the testing performed on each of these systems varies with the length of time it has been included in the prog ram . For example, the feedwater, condensate and the heater drain systems were added as a result of the Surry i event and limited testing has been performed on these i systems.

Unit 2 first performed inspections of wall thickness in response to the pipe leaks which occurred in the extraction steam piping system during the course of unit operation.

Thickness testing then evolved into a normal plant surveillance to predict the potential for pipe failures so that replacement could be accomplished prior to failure during the upcoming refueling. Pipe replacement is recommended if a wall loss of greater than 49 percent of nominal wall occurs. Areas of wall loss which falls between 30 and 49 percent may be tested on a quarterly basis to track the potential progression.

Points are selected for thickness testing based on past experience, and known problem areas.

Page 2 The frequency of examinations is based on the unit's outage j schedule and the time available for insp'ection-and repair. I The criteria which are used to perform the inspection are: I

a. Piping which was replaced during the previous refuel is i inspected to determine the extent of wall loss during one cycle of operation.

b. Piping which has shown wall loss of 15 to 20 percent during a previous inspection period will normally be reinspected during the next. inspection interval.

I c. Problem areas which have a known wall loss rate are inspected based on this anticipated rate of degradation. j Once the area of interest has been determined-then the inspection is performed utilizing a grid pattern around the j subject area of the pipe. This. inspection is performed per the requirements of Procedure NU-UT-1 which is attached for 3 your information.

3. For liquid phase systems, state specifically whether.the following f actors have been considered in establishing your l criteria for selecting points at which' to monitor piping  !

l thickness (Item 2a): j i

a. piping material ( e .g . ,. chromium content)

b. piping . config uration (e .g . , fittings less than 10 pipe diameters apart)

, c. pH of water in the system ( e .g . , pH less than 10) ,

l d. system temperature (e.g., between 190 and 500 F) 5

e. flutd bulk velocity (e .g . , greater than 10 ft/s)

f. Oxygen content in the system (e.g., oxygen content less -

l than 50 ppb) l NNECO Response:

The liquid systems, which are the most recent additions to l the program, are selected on the basis of the.following criteria:

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a. Bulk fluid velocity is the prime selection criteria for establishing which order of priority a given piping run is given.

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b. Piping configuration, two or more directional changes within 10 pipe diameters.

c. Areas in the plant where the piping system is in close i proximity to personnel transit lanes. j b

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The above criteria are the three bases used to determine the pipes which will be inspected. The higher the velocity the tighter the_ directional changes in the . flow and the greater l the priority placed on the area for inspection. l The remaining attributes listed in Action 3 were considered in the formation of the program for liquid phase piping . i Corrosion product transfer studies are planned for the near future to quantify the ef fects. of pH and oxygen on . iron dissolution. Essentially all bulk fluid downstream of the fif th point heaters is greater than 190 degrees with pH and oxygen below 10 and 50. 0 ppb, respectively. 3

4. Chronoirgically list and summarize the results of all inspections that have been performed, which were specifically conducted for the purpose of identifying pipe wall thinning, whether or not pipe wall thinning was discovered, and any other inspections where pipe wall thinning was discovered even though that was not the purpose of that inspection.

a. Briefly describe the inspection program and indicate )

whether it was specifically intended to measure wall J j thickness or whether wall thickness measurements were an l l incidental determination.

b. Describe what piping was examined and how (e.g . , describe l the inspection instrument (s), test method, reference I thickness, locations examined , means for locating l measurement point (s) in subsequent inspections). l

c. Report thickness measurement results and note those that l were identified as unacceptable and why.

d. Describe actions already taken or planned for piping that has been found to have a nonconforming wall thickness.

If you have performed a failure analysis, include the results of that analysis. Indicate whether the actions involve repair or replacement, including any change of j materials.

NNECO Response:

Response to Action No. 4 is difficult to document for the inspections performed on pipe prior to the unit's 1986 re f ueling . Inspections performed prior to this refueling had been performed on an informal basis. Inspections were performed, disposition of abnormalities completed, and the repairs completed when required. These repairs were documented on individual work orders and are not recorded in a comprehensive report. As previously mentioned, these i

Page 4' inspections did not include high-energy liquid phase systems.

The 1986 refueling inspection report (Tabs 1, 2, and 3) is attached for your review in response to yout Action.No. 4.

This report is the most comprehensive report available to date and the f ull report consisting of twenty-one . tabs ' is available if. desired. It was performed for the purpose of checking pipe wall thickness.

In addition to the inspections performed during the ref ue ling s , a section of pipe in the feedwater system was inspected during an unscheduled shutdown. This later inspection was performed in response to plant nanagement's concerns on the state of the feedwater system as a result of the Surry event. The results of this inspection showed that some minimal wall thinning , 5 percent of nominal wall, has occurred in an area of the system with velocities of more than 20 f t/sec and two direction changes within 10 pipe l diameters.

5. Describe any plans either for' revising the present or for developing new or additional programs for monitoring pipe wall thickness.

NNECO Response:

In a letter dated June 10, 1987,(1) NNECO indicated that we l are an active participant in the NUMARC Working Group on {

Piping Erosion / Control. In an effort to be consistent with .j the industry and maintain consistency within our organi- I

, zation, NNECO intends to meet the guidelines established by l this group for Millstone Unit No. 2.

l (1) E. J. Mroczka Letter to U.S. Nuclear Regulatory Commission,

" Pi pi ng Inspection Programs to Detect Erosion / Corrosion Wear," dated June 10, 1987.

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