ML20234C561
| ML20234C561 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/10/1987 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 5211-87-2170, IEB-87-001, IEB-87-1, NUDOCS 8709210335 | |
| Download: ML20234C561 (11) | |
Text
f _,
GPU Nuclear Corporation G. u Nuclear
- ers:r8o o
Middletown, Pennsylvania 17057 0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number:
September 10, 1987 5211-87-2170 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Response to IEB 87-01 NRC Bulletin No. 87-01 (Thinning of Pipe Walls in Nuclear Power Plants) requested information concerning licensee programs for monitoring the thickness of pipe walls in high energy single phase'and two phase carbon steel piping systems. This letter responds to this request.
i Item 1 Identify the codes or standards to which the piping was designed and fabricated.
Item 1 Response TMI-l piping (for purposes of this response) is designed and fabricated in accordance with the following:
Design Codes:
USAS B31.1 Power Piping Code,.1967 Edition.
Fabrication, testing, and erection:
- 1) Subsection 1, Draft USA Standard B31-7, dated Feb.1968 for nuclear class piping only.
8709210335 870910
- 2) USAS B31.1,1967 - for all
$DR ADOCK 0500 9
non-nuclear class piping..
l l
Item 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:
a.
selecting points at which to make thickness measurements b.
determining how frequently to make thickness measurements i
c.
selecting the methods used to make thickness measurements '
d.
making replacement / repair decisions
/h GPU Nuclear Corporation is a subsidiary of the General Public Utlllties Corporation j
l.
1 i
.5211-87-2170 Item 2 Response The scope of the existing program is the identification and inspection of secondary plant Carbon Steel piping systems affected by Erosion / Corrosion l
(E/C); evaluation of E/C status; corrective action required.
The extent of the program is inspections which will cover the following steam, two-phase, and liquid systems:
Turbine Drains I
Main Steam (including turbine related piping)
Steam Dump and Bypass Extraction Steam Condensate (downstream of 10th stage heater)
Feedwater Feedwater Heater Drains Aux Steam Main Steam to Relief Yalve Post Supports Steam Generator Secondary Side a.
Component selection of thickness measurements is based on the following criteria:
l Process Fluid-temperature - 195-440*F
-pH - All systems included - No exclusions made
-Oxygen Content - All systems included -
No exclusions made
-Moisture Content - 2% and above Pipe Material-plain Carbon Steel (CS) -
(Lack of alloying metals; Cr, Mo, Cu)
Piping Geometry-Each system is evaluated for arrangement of components (tees, elbows, pipe, etc.) for configurations that are inducive to flow disturbances.
Especially combinations of components which are close together F1uid Velocity -All velocities are con 5idered.- priority placed on piping with higher velocity Additional inspection prioritization criteria:
System Category
- required for shutdown or for prevention of challenges to Safety Systems Component location - as related to Safety Equipment
- as related to Personnel Hazard Design Margin
- accounts for the Ratio between Nominal and Design pipe wall thicknesses Scope of inspections may be expanded to similar components in same system based on engineering evaluation.
5211-87-2170 b.
Thickness measurement frequency:
Components for first - scheduled for inspections during E/C inspection refueling outages Re-inspected
- scheduled for inspections during components refueling outages, or at earliest '
windows of opportunity, based on evaluation (see Table below COMPONENT EVALUATION CRITERIA BASED ON REMAINING SAFE OPERATING LIFE (SOL) l l
1 I
l ACCEPTANCE CATEGORY l Criteria (1) l COMMENTS l
lAl Immediate Replacement 0 cycles (2) l' Additional Evaluation l
-l l 1 of Component l
l by Engineering Optional l
l l l
l (Technical Functions Div)]
lBI Engineering fless than one cycle I" Evaluation Required for l l Evaluation l
l Component Reassignment ll l
l into Category A or C-lCl Potential Next lLess than two cycles
..l' Red Alert Status (R/A)
I l Outage Replacement l
l-Next Outage Inspection l l l
l-CONTINGENCY REPLACEMENT ll l
l' Yellow Alert Status (Y/A)
)
lDI Next Outage ILess than three cycles l-2nd Outage Insp. Req'd l l Inspection Suggested I l-Contingency Replacement I
l ll l
l Preparation Following l
ll l
l 1st Outage I
lEl Component Re-lMore than three cycles l
Component Reassignment l
l l Scheduling for Later l I
into Category D Required l 4
l l Inspections l
l when SOL 5.5 Yrs l
NOTES:
i (1)
Engineering evaluation of remaining years before pipe wall will reach minimum wall thickness.
(2)
Minimum wall thickness already reached or is less than minimum wall thickness.
j
6211-87-2170 c.
Methods used to make thickness measurements:
GPUN Engineering has specified these inspection requirements:
area of 11 erest, NDE method, grid size, accuracy, repeatability, and data handling. Manual ultrasonic examination utilizing a hand' held digital measurement and recording system is currently being
)
used.
l Automatic scanning was considered and found unsuited for use on fittings.
Further evaluations of ID and OD scanners are made as industry advancements are made, f
Radiography has been considered and found unsuited due to personnel traffic in the areas of inspections.
The manual ultrasonic method presents the following advantages:
I Minimal personnel training l
Meets accuracy requirements i
Minimizes personnel errors Allows rapid measurements of large number of points l
Automatically transfers data to computer data base Stored data manipulation allows visual effects and comperison to previous and subsequent data sets, d.
Repair / replacement scope and extent are based on Component Evaluation Criteria (Ref. Subsection 2b.).
Item 3 For liquid-phase systems, state specifically whether the following factors have been considered in establishing your criteria for selecting points at which to monitor piping thickness (Item 2a):
a.
piping material (e.g., chromium content) b, piping configuration (e.g., fittings less than 10 pipe diameters apart) c.
pH of water in the system (e.g., pH less than 10) d system temperature (e.g., between 190 and 500*F) e.
fluid bulk velocity (e.g., greater than 10 ft/s) f.
oxygen content in the system (e.g., oxygen content less than 50 ppb) i I
L
1 1
5211-87-2170 1 Item 3 Response The principal factors considered for Liquid-phase systems are:
Pipe Material-plain CS - Lack of alloying metals; Cr, Mo, Cu Piping Geometry - Each system is evaluated for arrangement of l
components (tees, elbows, pipe, etc.) for configurations that are inducive to flow disturbances.
Especially combinations of components which are close together.
- pH - All systems included I
- 0xygen Content - All systems included System Temperature - 195-440 deg. F 1
Fluid Bulk Velocity - All velocities are considered - priority j
placed on piping with higher velocity.
- 0xygen content and pH have not been used to prioritize inspection locations.
Future use of the CHEC E/C computer program, currently under evaluation, may j
account for these factors.
Future inspections will be based on inspection results and may affect system selections.
Item 4 Chronologically 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 thickness or whether wall thickness measurements were an incidental determination, b.
Describe what piping was examined and how (e.g., describe the inspection instrument (s), test method, reference thickness, locations examined, i
means for locating measurement point (s) in subsequent inspections).
c.
Report thickness measurement results and note those that 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 materials.
Item 4 Response GPUN's program was specifically formulated for pipe E/C inspections. The following information addresses the inspections performed to date.
a 5211-87-2170- i J
I.
1983Inspegions The first pipe wall thinning inspection program was ' issued in 1982 Land covered steam systems only and was based on EPRI's recommendations:
High Moisture Content High Fluid Yelocity Multiple Flow Directional Changes Review of Failures and Inspections Reported by Industry Carbon Steel Piping Acceptance criteria for UT inspection results:
Acceptable readings
- Minimum Manufacturing Tolerance (Nominal Wall minus 12.5%)
[
Rejectable readings
- Below Minimum Design Wall Thickness Engineering Evaluation - Readings Falling Between Acceptab1e
~
and Rejectable f]
NOTES: ANSI B31.1 formula for internal pressure (Hoop Stress) is used to calculate the Minimum Design Wall.
NO ALLOWANCE for additional thickness is made (A=0) q 1983 INSPECTION SCOPE
-)
l INSPECTIONS l
STEAM /TWO-PHASE I
LIQUID l
l l
l l-1 INITIAL SCOPE I
- 3. LOCATIONS (6th Stage Extraction), l~ 0 LOCATIONS l
I I
I I
INCREASED SCOPE l 27 LOCATIONS 0 LOCATIONS l
l Based on evalua-I l
l tion of initial l
l-l I
scope.
l l
l l
l l
l l
I I
TOTALS l 30 LOCATIONS 0 LOCATIONS l
l l
l l'
- _ _-_ ____ -_ w __ __ --_
5211-87-2170 I l
1983 INSPECTION LOCATIONS i
l SYSTEM I NO.0F l TYPES OF COMPONENTS I
RESULTS l
l l LOC'S I l
I l
l I
I I
I 6th Stg. Extrct!
10 (4)18" TEE;(3)18" ELL;(2)24" ELL l COMP. REPLC'DI I
l (1)18" PIPE I
i l
l I
I
.I l 4th Stg. Extrctl 2
l(2)10" ELL lALL COMP ACCEPTED l l
l l
l l
l i
l I
I I
l 8th Stg. Extrctl 5
l (1 )30" HEADER;(1 )18" TEE; l ALL COMP ACCEPTED j
l I
l(2)18" ELL;(1)20" ELL l
l j
l l
I I
i 110th Stg. Extrcti 7
l(1)42" HEADER;(2)24" ELL lALL COMP ACCEPTED 1 1
l l(1)24" TEE;(2)26" ELL;(1)24" PIPE l
l I
I l
l
- 12th Stg. Extrctl 4
l(1)28" ELL;(1)40" header ALL COMP ACCEPTED l l
l l(1)24" TEE;(1)24" ELL i
l I
i i
l l
l MAIN STEAM l
2 l(2)24" ELL lALL COMP ACCEPTED l l
l 1
1 I
I NOTES: (1) Component replaced:
18" Dia TEE, 0.375" Wall Nominal; Minimum design wall = 0.149" thick; Minimum UT reading = 0.140".
The following information describes the NDE methods used:
The nondestructive examination method used to investigate the possible eroded piping is known as the ultrasonic method (UT).
The equipment employed was the " SONIC MARK I" ultrasonic flaw detector.
The flaw detector was calibrated to assure that linearity requirements were met prior to use. All readings taken with the " SONIC MARK I" detector were verified with a "DM-2" ultrasonic thickness gauge. This provided an extra assurance on the precision of the principal equipment employed.
The accuracy of the ultrasonic detector was found to be better than +2%.
The scanning of the selected areas for inspection was performed using a maximum grid of 2 inches on all accessible surfaces. The grid size was chosen based upon direct experience with the inspection method.
l
.m 5211-87-2170 i l
II.
1986-87 Inspections j
The inspection scope covered steam, two-phase and liquid systems. The inspection criteria was updated to incorporate the latest EPRI and industry recommendations (as described in Items 2a and 3 responses):
High Moisture Content (Steam only)
Fluid Chemistry and pH High Fluid Velocity Multiple / Abrupt Changes in Flow Direction Temperature Operating Frequency i
Reinspection of Components Previously Inspected (for E/C Rate Check) l The acceptance criteria for UT inspections included evaluation of the Safe Operating Life, based on E/C rate. Acceptable readings include minimum manufacturing tolerance of nominal wall minus 12.5%.
Evaluation of E/C rates was based on component original wall thickness l
assumed equal to 112.5% Nominal values.
(This represents a change 3
which increases the confidence margin by assuming higher E/C rates, l
therefore lower SOL's. )
1986-87 INSPECTION SCOPE I
I I
I I
l l
l l
l REINSPECTION l
l INSPECTIONS i STEAM /TWO-PHASE I LIQUID l0F 1983 POINTS l l
1 I
I l
l INITIAL SCOPE l
18 l
17 l
12 (steam) l I
l l
l
.I I
I I
I l
l INCREASED SCOPE l
1 l
27 l
0 l
l (POST SURRY l
l l
l l INCIDENT) l l
l l
l l
l l
TOTALS l
19 44 l
12 (steam) i I
l l
--.-,--,-_.-----.------_----------,,--------_x-
[.
.1 5211-87-2170 I 1986-1987 INSPECTION LOCATIONS l
l TOTAL I I
l l
SYSTEM l
NO.
l TYPES OF COMP 0NENTS l
RESULTS l
I I
I l
16th STAGE EXTRCT l
7 (2) 18" TEE' (5) 18" ELL l0NECOMP0N{NTWELD l
l l
REPAIRED l
I4th STAGE EXTRCT i
2 l(2) 10" ELL '
lALL COMPONENTS ACCEPTABLE 18th STAGE EXTRCT l
2 l(1) 16" ELL; (1) 20" ELL lALL COMPONENTS ACCEPTABLEl 110th STAGE EXTRCT l 2
l(1) 12" ELL; (1) 24" N0ZZLE lALL COMPONENTS ACCEPTABLEl l MAIN STEAM l
2 l(2) 24" ELL lALL COMPONENTS ACCEPTABLEl l AUXILIARY STEAM l
2 l(1) 16" ELL; (1) 16" TEE lALL COMP 0NENTS'ACCEPTABLEl ICROSS AROUND PIPE I 2
l(1) 36" ELL; (1).42" ELL lALL COMPONENTS ACCEPTABLEl l HEATER DRAINS l 22 l(10) ELL; (3) N0ZZLE; IFOURCOMP0 GENTS I
l l
(4) PIPE I
REPLACED lHEATER DRAINS l
(3) RED; (2) TEE l0NE COMP 0NENT WELD l-l l
l REPAIRED 3 l CONDENSATE l
8 l(4) 20" ELL; (2) 12" ELL; ALL COMPONENTS ACCEPTABLE I
l l(2) 20" N0ZZLE-l FEED WATER l
14 l(9) 20" ELL; (4) 24" ELL; ALL COMPONENTS ACCEPTABLE i
l l
l(1) HEADER l
l 1
I l
l 1
NOTES:
(1) Component rejected at inspection:
18" x.375" nom. wall 45* ELL Min. acceptable wall =.328"; Min. design wall =.149", Min. UT =.214" Reason for rejection: SOL less than a full power cycle.
Component weld deposit repaired.
(2) All components rejected had SOL = 0 years (UT = Min design).
Four components have been replaced; two with 2-1/4 Cr-1 Mo alloy, two with plain CS.
(3) One component weld deposit repaired.
The following information describes the NDE methods used:
All erosion / corrosion examination activities were performed in accordance with written approved procedures utilizing Level II UT personnel.
The ultrasonic system used during Outage 6R (1986/87) consisted of a Krautkramer DMX-1 digital thickness instrument connected to a Viewsonics data logger.
The data. set for a fitting was taken manually and stored in the logger until it was transferred into a personal computer (PC). Viewsonics Ultrasonic Data Analysis (UDA) sof tware was utilized to produce a hardcopy of all readings, topographic maps if desired, and storage of readings for later comparison and trending..
,o i
i 5211-87-2170 l t
The areas examined on each point of interest are described below.
1.
Tees, wyes,. elbows, and reducers included the entire fitting and one I
foot of pipe on each end of the fitting.
2.
Nozzles included the entire nozzle and one foot of pipe on the branch I
run.
3.
Blind flanges or manholes included the blind flange or cover and l
l extended one foot back on the adjoining pipe or vessel.
j 4.
Pipe bends consisted of a distance of five nominal pipe diameters with l
the center of the examination area in the middle of the pipe bend arc.
l Each point of interest examined was laid out in a two inch or one inch I
grid size with thickness readings taken in the approximate center of the grid. The two inch grid was applied to all areas four inch nominal pipe size and greater with the smaller grid used on all nominal diameters less than four inches. Grid start and stop locations were permanently stamped j
into the pipe and a sketch of the layout included as part of the data report. This technique should allow for relatively accurate relocation of j
measurement points during subsequent examinations.
j Item 5 Describe any plans either for revising the present or for developing new or additional programs for monitoring pipe wall thickness.
I I
Item 5 Response i
A new program is currently under development for implementation at TMI-1 (and also GPUN Oyster Creek tite).
The program scheduled to become effective prior to the next inspections outlines organizational requirements for future l
inspections, incorporates comprehensive selection and prioritization criteria I
based on EPRI and industry recommendations, assures consistent interpretation of results and continuous updating and revision of data.
l l
GPUN is proceeding with an inspection program based on an expanded version of i
l the VEPC0 Component Rating Scheme.
I t
I
r
-5211-87-2170 GPUN is evaluating.the CHEC Program, which is only applicable for liquid phase systems,. and we currently. plan to perform a comparison of specific systems a
using both programs.
.q Sincerely,.
i 1
a 3
. D. Hu 11 Vice President & Director, -TMI-1 l
l j
l HDH/DVH/spb:0978A I
cc:
W. Russell R. Conte G. Edison 1
Sworn and subscribe to befor,emethipj_O day t
of JpsTinhbv,1987-
/
/-
q
/))1/Y)- f.'
11 AJ1%
f Notary Py071c i
5traic h ha&L 60Wii PUBLiC l
f4100tI700N B030. DAUP!:nt COUm i
IAY 00ritt:5510!i EXPIECS JUNE 12,1989
'{
14 ember, Paasymnia Anochtfon of Goksht i
'{
l l
i l
l
-)
i I
_ _ _ - _ _ _ _