ML021500453
| ML021500453 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 04/20/2002 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| Download: ML021500453 (6) | |
Text
NRC Questions and Comments I Responses (April 10, NRC/FE mtg) 4/20/2002 Question /Issue Response What is the distance from the wastage edge to nozzle #11 (Outside Circumference)? The distance is 2" -2.5" Has the wastage (at nozzle #3) been fully characterized? Yes, Liquid Pen of bore upon removal of cavity to ensure.
Is analysis completed to meet Section III? The Calc is in progress, the plate thickness has not yet been determined.
Why did you use '89 Section III? This was the first edition to address ambient temper bead welding.
Who is performing the welding (for nozzle #3 repair)? FTI will do a portion of the welding & Weld Services. Inc. for the plate installation.
We are using the same What is the track record of the repair organization with this type of repair?prcs;temkupwldmotaethwlinapoc. material as used at VC Summer. Alignment is suitable for the process; the mock up will demonstrate the welding approach.
Are you using full scale mock up? Yes.
What type of mock up will be used? Full scale for cutting, repair, NDE.
How realistic is the mock up (Include Nozzles, etc)?nuersiebedostssaays 36" x 36" x 7" ; full thickness w/clad, flanges & nozzles in place; same material & heat number; size based on stress analysis 2
We plan to take dimensions before & after welding on the mock up to check for Are you measuring residual stresses since the weld area is bigger than 100~in ? nozzle distortion.
Are The dimensions taken for nozzle distortion could be used as part of the justification Are the residual stress measurements part of the justification for greater than 100in2? for this item.
There is a 11/16" ligament between nozzles #3 & #11, does the mock up include a Do not know yet; no appreciable effect on nozzle #11 as assumption.
plug for nozzle #11 position?
Are you doing a procedure qualification test for the mock up (Tensile, Bend & Notch FTI has a number of procedures (available to NRC) which include this; No actual Toughness)? mechanical specimens; Tests will be to code req'ts Page 1
NRC Questions and Comments / Responses (April 10, NRC/FE mtg) 4/20/2002 Question /iIssue Response Are you radiographing the mock up? Yes, PT, UT and RT will be done.
Maybe you can reconsider on the PQRs? No Response.
How will you qualify the UT on mock up? It will be discussed later in the presentation.
Are you submitting a Design Report? We will be submitting a repair plan with details for the repair based on CAL.
Are you submitting a stress analysis? Yes we can, to whatever detail required.
In the transient, normal & off-normal design conditions will you consider as-found Analysis is on going. The as found condition will be addressed.
condition effect including fatigue on nozzle, penetration & welds?
Will the remaining transients, normal and off normal design condition, be included in Analysis will be applied to all remaining cycles for 15 year duration.
repair / replacement?
FTI design(stress analysis) is the design agent; SIA is a independent third party What is the "third party design"? 10OCFR50 App B applies, design analysis; reviews of SIA Calc will be done by FENOC.
Is this analysis done per approved calc procedure and are you including analysis and We are not planning to submit entire package but can discuss to decide.
calculation?
Since this weld is thick (nozzle #3 repair), will heat input be controlled in mock up? The mock up will be treated as safety related with all requirements of actual.
How do you accommodate for radiation field in the mock up? We will be using the same automated machinery.
Are the examinations automated? PT & UT are not (Exposure limits will not be exceeded).
UT on buttered surface; RT for main structural weld for code; final inspection still Is code UT possible? under consideration.
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NRC Questions and Comments / Responses (April 10, NRC/FE mtg) 4120/2002 Question / Issue Response Is UT proposed for the ISI baseline of the structural weld? This is still under consideration; it could be a RT.
Will the qualification for ISI baseline be appropriately demonstrated? Yes.
For nozzle #2 & #11, how are the plugs fabricated? One piece of bar stock with core machined out.
How will you repair nozzle #2 damage? Blend the area for stress analysis, so there are no stress risers in the area.
Is there a gap at corrosion area (#2 nozzle)? A structural weld will secure the plug outside the gap area.
Hlow big is the cavity for nozzle #2?ar. It starts at 1-1/2" - 2" from bottom/clad; attachment weld will not infringe on waste area.
No actual physical samples; We have dental molding, chemical scrapings and the Are you taking samples from nozzle #2? nozzle has been retained; We have everything we need from nozzle #2.
The weld is the same as #1, 5 & 47, so the same equipment will be used; no Will you do a mock up for nozzle #2? additional mock up.
Root cause identified if no oxygen is present, corrosion is not a concern. No change Are you concerned about ferritic exposure in head? to design.
Will there be any analysis of nozzle #2 grooves? This will be addressed.
Will the design condition consider the past operation and the as found impact on We will verify that we have not exceeded the plant design specification. We will look future operation? at accummulated fatigue and will consider past ops on future ops (15yrs).
Will new plug installed at nozzle #3 distort adjacent control rod drives? Will you Photogrametry will be used before & after the repair is completed.
measure distortion in control rod drives?
This is being evaluated; We may use cameras, European air humidity sampling Are you performing a leak test in addition to code min Enhanced VT?sytmoprintepes.hladtenekcekex.
system, operating temp, press. hold and then leak check exam.
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NRC Questions and Comments / Responses (April 10, NRC/FE mtg) 4/20/2002 Question /IIssue Response Do you plan on preparing the surface prior to PT with regard to nozzle #3? Yes.
Text books will be consulted for calculating factors; calculate based on known factors How do you treat finite element discontinuity strength reduction factor/SIF and are & increase finite element results by same; The justification will be available for staff you submitting for comment? review.
How are you treating root condition/consumable insert (at nozzle #3)? Ceramic backing; full penetration weld; semi automated grinding; PT; RT.
The weld will not be incomplete; backgrind, PT, may be accepted as is; We will fully So you have limits on grinding/lack of penetration - What is your approach? define limits; the weld will be a full penetration weld; This will be demonstrated in the full mock up.
Are you doing anything more than code min. in-process req't for examination (of Could be; We will have more detail in the work plan; use mock up for RT; progressive nozzle #3 repair)? volumetric inspection; do surface exam prior to volumetric each time.
and beyond code Geometric vertical lines on RT are a challenge for inspection; incomplete fusion; how We will do RT in 4 quadrants; determine plane & distance; above do you distinguish between geometry or incomplete fusion? req't; established by mock up.
Do you have a contingency plan if you find additional missing material (at nozzle #3) We have a contingency plan - fill & machine before weld; start-stop areas will be during water jet? removed.
What is your plan for problems with disc installation and additional repair if required? We will fully repair the hole prior to machining the disk to final dimension.
Do you have concerns with cracks propagating from exist J-groove weld to UT'd area not removed, there is no PWSCC concerns; We considered worst case buttering/new weld or plug? flaw in existing J-groove weld.
The plug is near full thickness; That is not a concern: Root cause shows that cracks Why not butter to the top on the uphill side; It may collect boric acid? from below caused the wastage.
Do you consider fatigue crack growth rate & usage factor? Usage factor will be used; no crack growth rate analysis.
Something causes cracks through the nozzle wall. If you find the cause will you The new material is different than original, therefore there is no cracking concern; consider it in new analysis? results of root cause will be addressed in design.
Will you justify why the crack growth is not included in design? Yes.
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NRC Questions and Comments / Responses (April 10, NRC/FE mtg) 4/20/2002 Question/Issue Response You do not have to analyze fatigue crack growth. Address why there is no longer a Understand.
concern?
The repair sequence is nozzles #2 &11 then 3; does your analysis look at residual The sequence is due to possible distortion at nozzle #3; There is no reason to be stresses at nozzle #11 in above sequence? You may want to go #3 then 2 & 11. concerned about residual stresses.
Suggest to PT nozzle #11 when nozzle #3 is complete. Sounds like good suggestion; We will consider.
Your repair is designed for 15 yr but you only plan to use it for one cycle? We have not committed to one cycle.
bead welding has been used in many applications on highly restrained You want approval for nozzle #3 repair weld relief since weldment is massive; how do Temper apply thermocouples & monitor mock up as demo-reduces dose in you justifyeanta you fontrnozzlcomponents;We'll justify heat control?aculwilsbtdt.
actual; will submit data.
Other welding is done to what? Preheat for shielded metal arc manual welding.
Do you need relief for thickness of base metal (Ref. code case N-638)? Thickness of buttering applies - ref. VC Summer - Not thru wall thick.
Code case N-638 was not written for thru wall configurations. Code case N-638 does not address configuration.
It is still being discussed in code committee; The limit is an arbitrary number. There is 100 sq. in. limitation issue is in the code committee, what is the basis of yournotcialbs;SAmdednzleuto10q.n.-orcnevtvehn no technical basis; SIA modeled nozzle up to 130 sq. in. - more conservative than justification for exceeding code limit? 100sq. in; EPRI investigating up to 500sq. in. limit.
Is the mock up going to provide adequate justification for going over 100 sq. in? The mock up will provide detailed justification.
Provide evidence (per mock up & other detailed data) in lieu of code. We Agree.
RT qualified per mock up; how confident are you of achieving good RT without film Should be do-able; discussed with Level IIl has been done before.
modeling and back scatter; how will radiation environ, affect real results?
Are fatigue considerations, thermal expansion and ligaments remaining at nozzles #3 Analysis is ongoing at FTI; SIA has not started.
& #11 being submitted in summary or detail?
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NRC Questions and Comments / Responses (April 10, NRC/FE mtg) 4/2012002 Question/i IssueResponse What is your time frame (for submitting analysis information)? We need several weeks to establish date.
Camera, European air humidity sampling system, operating pressure & temp. then go How are you leak checking? down and inspect.
Have you considered pressure testing head? Not practical.
Is humidity sensing equipment sensitive enough? Still working, no answer to date.
Are any tests being done on penetrations which may be affected by repairs? Drop time test at full temp. & press.
Is there an effect on peaking factor? No; slight at low power but within tech specs.
Do you verify individual Rod position indications? Yes.
Flux distribution at vessel wall will not change? Correct.
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