ML092940701

Exelon Slides for October 22, 2009, Public Meeting, Buried Piping Experience

ML092940701
Person / Time
Site:	Oyster Creek
Issue date:	10/21/2009
From:	Exelon Generation Co
To:	Office of Nuclear Reactor Regulation
Miller G, NRR/DORL, 415-2481
References
Download: ML092940701 (11)

Text

Oyster Creek I Buried October 22, 2009 Exe Its n. Oyster Creek I Exelon ./ Agenda

• Overview

• Oyster Creek Underground Piping Leaks

• Buried Piping Program

• Exelon Experience & Plan

• Technical Discussion of Lessons Learned for Buried Piping Experience 1

Overview ./ Exelon has changed approach-more proactive

./ Exelon is inspecting buried piping at all sites with a formal program consistent with industry approach ./ Long term repair/replacement projects being identified to improve the reliability of high risk piping ./ No public health or safety consequences

./ Affected public perception /

confidence April 2009 Tritium Leak ./ Leaks in the 8-inch and 10-inch carbon steel Condensate Transfer System lines

./ 8-inch line understood to be Stainless Steel

./ 10-inch line under vacuum during power operation

./ No plant operational or nuclear safety issues associated with the leaks 2

Exelon. April 2009 Tritium Leak ./ Causes

• Root Cause 1: "anodic dissolution" in conjunction with a susceptible material

• Root Cause 2:

erroneous assumptions in program basis led to flawed tritium mitigation strategy

• Contributing Cause 1: improperly applied coatings during repairs in the early 1990s

• Contributing Cause 2: change management processes were inadequate

• Contributing Cause 3: 100%

verification of integrity is not Exelon. April 2009 Tritium Leak ./ Corrective actions to prevent recurrence Move affected dlrectburled piping either above ground or in monitored trenches Perform a thorough program assessment and update the program based on the results 3

Exelon. August 2009 Tritium Leak ,/ Six-inch aluminum Condensate Transfer line ,/ Piping leak occurred inside the Turbine Building wall penetration

,/ Identified through Turbine Building sump pump-down rate ,/ No plant operational or nuclear safety issues associated with the leak Exelon. August 2009 Tritium Leak ,/ Causes

• Root Cause 1:

galvanic corrosion resulting from a coating breach

• Contributing Cause 1: incomplete extent of condition reviews

• Contributing Cause 2: buried piping program does not include piping internal to penetrations and the conditions of the penetrations are typically unknown 4 Exelen. August 2009 Tritium Leak ../ Corrective actions to prevent recurrence

• Implement a risk-based strategic inspection plan including all piping traversing though piping penetrations

../ Additional corrective actions

• Institutionalize guidance to document as-left conditions following excavations

• Inspect all piping penetrations and document the as-found and as-left conditions . ----__ ",11 __ Buried Piping Program Goal: Ensure structural integrity, prevent forced outages, avoid emergent repairs, eliminate environmental impact and enable sites to implement well planned repairs in a timely manner. Process is 4 steps Pre-Assessment Analysis Indirect Assessment Direct Examination Post Assessment 5

Exelon. Exelon Buried Piping Program Approach ./ The original approach for the Exelon Buried Piping Program was to categorize the high risk piping, perform inspections, and repair/replace based on unacceptable inspection results and/or actual leakage .

./ The approach has changed to add a proactive replacement or containment strategy to the Buried Piping Program as a Strategic Capital Project Buried Piping Program Scope .Il!R.IlIr.n Direct E:umlneUon ftgme 1: Four -Step Process for the B..-ied Pipe and Raw W"l8f Piping Program 6 Step 1 Pre-Assessment Analysis ,/ Buried Pipe Governing Procedures

• Buried Piping Program Guide

• Raw Water Corrosion Program Guide

• Buried Piping Exam Guide

• Buried Piping Performance

,/ Risk {R} defined as: R

=Susceptibility x

o Susceptibility factors: Is cathodic protection applied Leak history Age of coating, condition of coating Location: Under tracks, roadway, building penetration (depth) Process fluid Soil o Consequence Factors: Safety Piping contains environmentally sensitive fluids (Rad-Waste, tritium, fuel 011) LCO associated with the piping (SR Service Water)

Lost production required to repair (high repair cost)

Exelon.FIgUre4B. Buried Pipe SusceptibtlityFlow Chari 7 Step 2 Indirect Assessment Met '-. Inspection Purpose Key Conditions Method Under Shielded NeM Cased Parallel Stray Deep Under pevcd corrosion River/ piping pipe-Current HighAC roads activity were-line voll Close lute-val Assess 3 3 2 3 2 2 2 2 Survey(CIS) effectiveness ofCP system Electro-magnetic Locate coating 2 3 2 3 2 2 2 3 defects Pearson Locale coating 3 3 3 3 3 2 2 2 defects CUITaltVoltage Locate coating 3 3 3 3 1,2 1,2 2 1,2 GraWml(ACVG defects DCVG) C*Sc<ln (AC) Locale coaling 2 3 2 3 1,2 1,2 2 3 CICOS detects Torsional Guided Wall thickness 4,6 4,6 3,6 4,6 4,6 4,6 4,6 4,6 Wave survey RemoteField Pinillg& Wall 4,5 4,5 4,5 4,5 4,5 4,5 4,5 4,5 Eddy Current thickness (RFEC) 1=Applicable: capableoflocatingsmallholidaysincoatlng(Isolatedand

<11n 2),andconditionathatdonotcauseCP 2 =Applicable: capable of detecting large (isolated or continuous) coaUng 3 =Not applicable to this method without additional 4 = Wall thickness survey G-wave and RFEC 5 =RFEC requires access to (pitch), pipe Internal, and needs an exit point. Tool must traverse the length of pipe inspected. Pipe may need to taken out of 6=The G-wave signal becomes more attenuated eeoverburden becomes greater; therefore, the effectiveness Step 3 Direct Assessmel,ts

./ Buried Piping: External Corrosion

• Excavations have significant impact on plant operations

• Coating evaluation

• NDE: Piping Prep, UT, Pit depth, ./ Raw Water: Internal

• NDE Piping Prep, UT, RT

• Plant OE; external corrosion above ground

./ Contingencies required to be in

• Pre-assessment corrosion (flaw) handbook

• Parts / materials 8

Exelori.7 Step 4 Post Assessment

./ Corrosion Rate is the key

./ Remaining Life ./ Time to next inspection

./ Effectiveness of inspection methods

./ Update the Database & Program documents

./ Repair/Replace Recommendations Exe10 ri.8 Exelon Experience 2009 ./ Experience in proactively identifying degraded piping using indirect assessment methods. ./ Failures related to:

• Age of piping

• Coating condition

• Initial construction backfill conditions

• Effectiveness of cathodic protection

./ Development

& application of new NDE techniques and associated limitations

./ Repair technologies

• Cured in place

• Carbon fiber wrap

• Traditional methods 9 Short and Long Term Plans Short Term (<3 years): Continue with program of indirect assessment and follow-up direct assessment as degraded segments are identified Optimize Cathodic Protection Systems Mitigation of known buried piping system vulnerabilities Initiate use of high density polyethylene (HDPE) on buried piping for long term corrosion prevention Plan for proactive replacemenUmitigation of high risk buried piping segments Long Term (>3 years): New Technology Inspection Applications to complete initial indirect assessment of high risk buried piping Incorporate use of high density polyethylene (HDPE) on Buried ASME Class 3 piping for long term corrosion prevention and to minimize risk Plan for large scale repairs/replacements projects with corrosion resistant materials and to improve operational flexibility ExeIOtf.O Challenges/Barriers/Gaps

./ Original Design Practices

• Building construction over piping, inaccessible piping Poor original cathodic protection design Piping not designed for current inspection -No access to piping -Concrete -Piping depth up to 35 -Insulated

./ Importance of Cathodic Protection not

./ Contingencies for Buried Piping Applying new inspection technologies (non-code) effectively inspect buried

• Challenge for timely repair of degraded piping 10 Summary ./ Exelon has changed approach-more proactive

./ Exelon is inspecting buried piping at all sites with a formal program consistent with industry approach ./ Inspections of buried inaccessible piping is a challenge and new technology is being developed

./ Approval of corrosion resistant material for repairs and replacements needed for long term plans

./ Long term repair/replacement projects being identified to improve the reliability of high risk piping 11