L-PI-12-078, PWR (Pressurized Water Reactor) Vessel Internals Program for Fulfillment of License Renewal Commitment 25

PWR (Pressurized Water Reactor) Vessel Internals Program for Fulfillment of License Renewal Commitment 25

ML12276A041
Person / Time
Site:	Prairie Island
Issue date:	10/01/2012
From:	Sorensen J Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-PI-12-078
Download: ML12276A041 (18)

Text

@ Xcel Energym U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 PWR [Pressurized Water Reactor1 Vessel lnternals Program for Fulfillment of Prairie Island Nuclear Generating Plant (PINGP) License Renewal Commitment 25 By letter dated April 11,2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML081130666), the Nuclear Management Company, LLC, (NMC') submitted an Application for Renewed Operating Licenses (LRA) for PINGP, Units 1 and 2. The LRA included commitment 25 related to the submittal of the PINGP PWR Vessel lnternals Program (PVIP) for NRC review and approval. In a letter dated May 12,2009 (ML091470263), NSPM updated the LRA to incorporate information regarding the new PWR vessel internals program. Renewed operating licenses DPR-42 and DPR-60 were issued June 27,201 1 including commitment 25.

The implementation schedule for part B of commitment 25 was August 9, 201 1 (Unit 1) and October 29,2012 (Unit 2). The NRC issued Regulatory Issue Summary (RIS) 201 1-07, "License Renewal Submittal Information for Pressurized Water Reactor lnternals Aging Management," (MLI 11990086) on July 21, 201 1. In accordance with the guidance of RIS 201 1-07, by letter dated August 8, 201 1 (MLI 12210299), NSPM revised the date for submittal of the PINGP PVlP to October 1, 2012., "PWR Vessel lnternals Program", provides the PINGP PVlP in fulfillment of commitment 25, part B.

The PINGP PVlP is based on ERPl Report 1016596, "Materials Reliability

• On September 22, 2008, NMC transferred its operating authority to Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"). By letter dated September 3, 2008 (ML082470648), NSPM assumed responsibility for actions and commitments previously submitted by NMC.

171 7 Wakonade Drive East e Welch, Minnesota 55089-9642 Telephone: 651.388.1 121

Document Control Desk Page 2 Program (MRP): Pressurized Water Reactor lnternals Inspection and Evaluation Guidelines" (MRP-227-A), which has been endorsed by the NRC (ML120270374). The NRC December 16, 201 1 safety evaluation for MRP-227, Rev 0 (MLI 1308A770),

contained eight licensee action items for licensees to consider. NSPM will provide the considerations of these eight licensee action items to the NRC by April I, 201 3.

If there are any questions or if additional information is needed, please contact Mr. Dale Vincent, P.E., at 651-388-1 121, Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.

This letter fulfills the requirements of license renewal commitment 25, part B.

L Joel P. Sorensen Acting Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosures (1) cc:

Administrator, Region Ill, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC Prairie Island Nuclear Generating Plant, Units 1 and 2 PWR Vessel lnternals Program Page 1 of 16 MRP-227-A Primary Inspection Components Page 2 of 16 Item Control Rod Guide Tube Assembly Guide plates (cards)

Control Rod Guide Tube Assembly Lower flange welds Core Barrel Assembly Upper core barrel flange weld Core Barrel Assembly Upper and lower core barrel cylinder girth welds Applicability All Plants All Plants All Plants All Plants Effect (Mechanism)

Loss of Material (Wear)

Cracking (SCC, Fatigue)

Aging Management (IE and TE)

Cracking (SCC)

Cracking (SCC, IASCC, Fatigue)

Expansion Link (Note 1)

None Bottom-mounted instrumentation (BMI) column bodies, Lower support column bodies (cast)

Upper core plate Lower support forginglcasting Lower Support column bodies (non cast)

Core barrel outlet nozzle welds.

Upper and lower core barrel cylinder axial welds Examination MethodlFrequency (Note 1)

Visual (VT-3) examination no later than 2 refueling outages from the beginning of the license renewal period, and no earlier than two refueling outages prior to the start of the license renewal period.

Subsequent examinations are required on a ten-year interval.

Enhanced visual (EVT-1) examination to determine the presence of crack-like surface flaws in flange welds no later than 2 refueling outages from the beginning of the license renewal period and subsequent examination on a ten-year interval.

Periodic enhanced visual (EVT-1) examination, no later than 2 refueling outages from the beginning of the license renewal period and subsequent examination on a ten-year interval.

Periodic enhanced visual (EVT-1) examination, no later than 2 refueling outages from the beginning of the license renewal period and subsequent examination on a ten-year interval.

Examination Coverage 20% examination of the number of CRGT assemblies, with all guide cards within each selected CRGT assembly examined.

100% of outer (accessible)

CRGT lower flange weld surfaces and adjacent base metal on the individual periphery CRGT assemblies.

(Note 2).

100% of one side of the accessible surfaces of the selected weld and adjacent base metal (Note 4).

100% of one side of the accessible surfaces of the selected weld and adjacent base metal (Note 4).

MRP-227-A Primary Inspection Components Page 3 of 16 Examination Coverage Item Core Barrel Assembly Lower core barrel flange weld (Note 5)

Baffle-Former Assembly Baffle-edge bolts Baffle-Former Assembly Baffle-former bolts Applicability Effect (Mechanism)

All plants All plants with baffle-edge bolts All plants Expansion Link (Note 1)

Cracking (SCC, Fatigue)

Cracking (IASCC, Fatigue) that results in:

Lost or broken locking devices Failed or missing bolts Protrusion of bolt heads Aging Management (IE and ISR) (Note 6)

Cracking (IASCC, Fatigue) Aging Management (IE and ISR)

(Note 6)

Examination MethodlFrequency (Note 1)

None None Lower support column bolts, Barrel-former bolts Periodic enhanced visual (EVT-1) examination, no later than refueling outages from the beginning of the license renewal period and subsequent examination on a ten-year interval.

Visual (VT-3) examination, with baseline examination between 20 and 40 EFPY and subsequent examinations and a ten-year interval.

Baseline volumetric (UT) examination between 25 and 35 EFPY, with subsequent examination on a ten-year interval.

100% of one side of the accessible surfaces of the selected weld and adjacent base metal (Note 4).

Bolts and locking devices on high fluence seams. 100% of components accessible from core side (Note 3).

100% of accessible bolts (Note 3). Heads accessible from the core side. UT accessibility may be affected by complexity of head and locking device designs.

MRP-227-A Primary Inspection Components Page 4 of 16 Item Baffle-Former Assembly Assembly (includes: Baffle plates, baffle edge bolts and indirect effects of void swelling in former plates)

Alignment and Interfacing components Internals hold down spring Applicability Effect (Mechanism)

All plants All plants with 304 stainless steel hold down springs Expansion Link (Note 1)

Distortion (Void Swelling),

or Cracking (IASCC) that results in:

• Abnormal interaction with fuel assemblies

• Gaps along high fluence baffle joint

-Vertical displacement of baffle plates near high fluence joint Broken or damaged edge bolt locking systems along high fluence baffle joint Distortion (Loss of load)

Note: This mechanism was not strictly identified in the original 'list of age-related degradation mechanisms' [7].

Examination MethodlFrequency (Note 1)

Examination Coverage None None Visual ((VT-3) examination to check for evidence of distortion, with baseline examination between 20 and 40 EFPY and subsequent examinations on a ten-year interval.

Direct measurement of spring height within three cycles of the beginning of the license renewal period. If the first set of measurements is not sufficient to determine life, spring height measurements must be taken during the next two outages, in order to extrapolate the expected spring height to 60 years.

Core side surface as indicated.

Measurements should be taken at several points around the circumference of the spring, with a statistically adequate number of measurements at each point to minimize uncertainty.

MRP-227-A Primary Inspection Components Notes to Table 4-3:

1. Examination acceptance criteria and expansion criteria for the Westinghouse components are in Table 5-3.

2. A minimum of 75% of the total identified sample population must be examined.

3. A minimum of 75% of the total population (examined + unexamined), including coverage consistent with the Expansion criteria in Table 5-3, must be examined for inspection credit.

4. A minimum of 75% of the total weld length (examined + unexamined), including coverage consistent with the Expansion criteria in Table 5-3, must be examined from either the inner or outer diameter for inspection credit.

5. The lower core barrel flange weld may be alternatively designated as the core barrel-to-support plate weld in some Westinghouse plant designs.

6. Void swelling effects on this component is managed through management of void swelling on the entire baffle-former assembly.

Item Thermal Shield Assembly Thermal Shield Assembly Applicability Effect (Mechanism)

All plants with thermal shields Expansion Link (Note 1)

Cracking (Fatigue) or Loss of Material (Wear) that results in thermal shield flexures excessive wear, fracture, or complete separation.

Examination MethodlFrequency (Note 1)

Examination Coverage None Visual (VT-3) no later than 2 refueling outages from the beginning of the license renewal period. Subsequent examinations on a ten-year interval.

100% of thermal shield flexures.

MRP-227-A Primary Inspection Components Examination Coverage 100% of accessible surfaces (Note 2).

100% of accessible surfaces (Note 2).

100% of accessible bolts.

Accessibility may be limited by presence of thermal shields or neutron pads (Note 2).

100% of accessible bolts or as supported by plant-specific justification (Note 2).

Examination MethodlFrequency (Note 1)

Enhanced visual (EVT-1) examination.

Re-inspection every 10 years following initial inspection.

Enhanced visual (EVT-1) examination.

Re-inspection every 10 years following initial inspection.

Volumetric (UT) examination.

Re-inspection every 10 years following initial inspection.

Volumetric (UT) examination.

Re-inspection every 10 years following initial inspection.

Expansion Link (Note 1)

CRGT lower flange weld CRGT lower flange weld Baffle-former bolts Baffle-former bolts Item Upper lnternals Assembly Upper core plate Lower lnternals Assembly Lower support forging or castings Core Barrel Assembly Barrel-former bolts Lower Support Assembly Lower support column bolts Applicability All plants All plants All plants All plants Effect (Mechanism)

Cracking (Fatigue, Wear)

Cracking Aging management (TE in Casting)

Cracking (IASCC, Fatigue)

Aging Management (IE.

Void Swelling and ISR)

Cracking (IASCC, Fatigue)

Aging Management (IE and ISR)

MRP-227-A Primary Inspection Components Page 7 of 16 Item Core Barrel Assembly Core barrel outlet nozzle welds Core Barrel Assembly Upper and lower core barrel cylinder axial welds Lower Support Assembly Lower support column bodes (non cast)

Lower Support Assembly Lower support column bodes (cast)

Applicability All plants All plants All plants All plants Effect (Mechanism)

Cracking (SCC, Fatigue)

Aging Management (IE of lower sections)

Cracking (SCC, IASCC)

Aging Management (IE)

Cracking (IASCC)

Aging Management (IE)

Cracking (IASCC) including the detection of fractured support columns Aging Management (IE)

Expansion Link (Note 1)

Upper core barrel flange weld Upper and lower core barrel cylinder girth welds Upper core barrel flange weld Control rod guide tube (CRGT) lower flanges Examination MethodlFrequency (Note 1)

Enhanced visual (Em-1) examination.

Re-inspection every 10 years following initial inspection.

Enhanced visual (EVT-1) examination.

Re-inspection every 10 years following initial inspection.

Enhanced visual (EVT-1) examination.

Re-inspection every 10 years following initial inspection.

Visual (Em-1) examination.

Re-inspection every 10 years following initial inspection.

Examination Coverage 100% of one side of the accessible surfaces of the selected weld and adjacent base metal (Note 2).

100% of one side of the accessible surfaces of the selected weld and adjacent base metal (Note 2).

100% of accessible surfaces (Note 2).

100% of accessible support columns (Note 2).

MRP-227-A Primary Inspection Components Notes to Table 4-6:

1. Examination acceptance criteria and expansion criteria for the Westinghouse components are in Table 5-3.

2. A minimum of 75% coverage of the entire examination area or volume, or a minimum sample size of 75% of the total population of like components of the examination is required (including both the accessible and inaccessible portions).

Item Bottom Mounted Instrumentation System Bottom-mounted instrumentation (BMI) column bodies Applicability All plants Effect (Mechanism)

Cracking (Fatigue) including the detection of completely fractured column Aging Management (IE).

Expansion Link (Note 1)

Control rod guide tube (CRGT) lower flanges Examination MethodlFrequency (Note 1)

Visual (VT-3) examination of BMI column bodies as indicated by difficulty of insertion/withdrawal of flux thimbles.

Re-inspection every 10 years following initial inspection.

Flux thimble insertion/withdrawal to be monitored at each inspection interval.

Examination Coverage 100% of BMI column bodies for which difficulty is detected during flux thimble insertionlwithdrawal.

MRP-227-A Primary Inspection Components Notes to Table 4-9:

1. XL = "Extra Long" referring to Westinghouse plants with 14-foot cores.

2. Bolt was screened in because of stress relaxation and associated cracking; however, wear of the clevislinsert is the issue Item Core Barrel Assembly Core barrel flange Upper lnternals Assembly Upper support ring or skirt Lower lnternals Assembly Lower core plate XL lower core plate (Note

1)

Lower lnternals Assembly Lower core plate XL lower core plate (Note

1)

Bottom Mounted Instrumentation System Flux thimble tubes Alignment and Interfacing Components Clevis insert bolts Alignment and Interfacing Components Upper core plate alignment pins Applicability All plants All plants All plants All plants All plants All plants All plants Effect (Mechanism)

Loss of material (Wear)

Cracking (SCC, Fatigue)

Cracking (IASCC, Fatigue)

Aging Management (IE)

Loss of material (Wear)

Loss of material (Wear)

Loss of material (Wear)

(Note 2)

Loss of material (Wear)

Expansion Link (Note 1)

ASME Code Section XI ASME Code Section XI ASME Code Section XI ASME Code Section XI NUREG-1801 Rev. 1 ASME Code Section XI ASME Code Section XI Examination MethodlFrequency (Note 1)

Visual (VT-3) examination to determine general condition for excessive wear.

Visual (VT-3) examination.

Visual (VT-3) examination of the lower core plates to detect evidence of distortion andlor loss of bolt integrity.

Visual (VT-3) examination Surface (ET) examination.

Visual (VT-3) examination Visual (VT-3) examination Examination Coverage All accessible surfaces at specified frequency All accessible surfaces at specified frequency All accessible surfaces at specified frequency All accessible surfaces at specified frequency Eddy current surface examination as defined in plant response to IEB 88-09.

All accessible surfaces at specified frequency All accessible surfaces at specified frequency MRP-227-A Primary Inspection Components Page 10 of 16 Item Control Rod Guide Tube Assembly Guide plates (cards)

Control Rod Guide Tube Assembly Lower flange welds Applicability All plants All plants Examination Acceptance Criteria (Note 1)

Visual (VT-3) examination The specific relevant condition is wear that could lead to loss of control and alignment and impede control assembly insertion.

Enhanced visual (EVT-1) examination The specific relevant condition is a detectable crack-like surface indication Expansion Link(s)

None

a. Bottom-mounted instrumentation (BMI) column bodies

b. Lower support column bodies (cast),

upper core plate and lower support forging or casting Expansion Criteria N/A

a. Confirmation of surface-breaking indications in two or more CRGT lower flange welds, combined with flux thimble insertionlwithdrawal difficulty, shall require visual (VT-3) examination of BMI column bodies by the completion of the next refueling outage.

b. Confirmation of surface-breaking indications in two or more CRGT lower flange welds shall require EVT-1 examination of cast lower support column bodies, upper core plate and lower support forginglcastings within three fuel cycles following the initial observation.

Additional Examination Acceptance Criteria NIA

a. For BMI column bodies, the specific relevant condition for the VT-3 examination is completely fractured column bodies.

b. For cast lower support column bodies, upper core plate and lower support forginglcastings, the specific relevant condition is a detectable crack-like surface indication.

MRP-227-A Primary Inspection Components Additional Examination Acceptance Criteria a and b. The specific relevant condition for the expansion core barrel outlet nozzle weld and lower support column body examination is a detectable crack-like surface indication.

Item Core Barrel Assembly Upper core barrel flange weld Expansion Link(s)

a. Core barrel outlet nozzle welds

b. Lower support column bodies (non cast)

Expansion Criteria

a. The confirmed detection and sizing of a surface-breaking indication with a length greater than two inches in the upper core barrel flange weld shall require that the EVT-1 examination be expanded to include the core barrel outlet nozzle welds by the completion of the next refueling outage.

b. If extensive cracking in the core barrel outlet nozzle welds is detected, EVT-1 examination shall be expanded to include the upper six inches of the accessible surfaces of the non-cast lower support column bodies within three fuel cycles following the initial observation.

Applicability All plants Examination Acceptance Criteria (Note 1)

Periodic enhanced visual (EVT-1) examination.

The specific relevant condition is a detectable crack-like surface indication.

MRP-227-A Primary Inspection Components Lower core barrel flange weld (Note 2)

Upper core barrel cylinder girth welds Applicability The specific relevant condition is a detectable crack-like All plants Periodic enhanced visual None (EVT-1) examination All plants Periodic enhanced visual Upper core barrel (EVT-1) examination cylinder axial welds Examination Acceptance Criteria (Note 1)

None The specific relevant condition is a detectable crack-like surface indication.

The confirmed detection and sizing of a surface-breaking indication with a length greater than two inches in the upper core barrel cylinder girth welds shall require that the EVT-1 examination be expanded to include the upper core barrel cylinder axial welds by the completion of the next refueling outage.

Expansion Link(s)

Additional Examination Acceptance Criteria Expansion Criteria None The specific relevant condition for the expansion upper core barrel cylinder axial weld examination is a detectable crack-like surface indication.

Page 12 of 16 MRP-227-A Primary Inspection Components Page 13 of 16 Item Core Barrel Assembly Lower core barrel cylinder girth welds Baffle-Former Assembly Baffle-edge bolts Applicability All plants All plants with baffle-edge bolts Examination Acceptance Criteria (Note I)

Periodic enhanced visual (EVT-1) examination The specific relevant condition is a detectable crack-like surface indication.

Visual (VT-3) examination.

The specific relevant conditions are missing or broken locking devices.

failed or missing bolts, and protrusion of bolt heads.

Expansion Link(s)

Lower core barrel cylinder axial welds None Expansion Criteria The confirmed detection and sizing of a surface-breaking indication with a length greater than two inches in the lower core barrel cylinder girth welds shall require that the EVT-1 examination be expanded to include the lower core barrel cylinder axial welds by the completion of the next refueling outage.

N/A Additional Examination Acceptance Criteria The specific relevant condition for the expansion lower core barrel cylinder axial weld examination is a detectable crack-like surface indication.

N/A MRP-227-A Primary Inspection Components Page 14 of 16 Additional Examination Acceptance Criteria a and b. The examination acceptance criteria for the UT of the lower support column bolts and the barrel-former bolts shall be established as part of the examination technical justification.

Item Baffle-Former Assembly Baffle-former bolts Expansion Link(s)

a. Lower support column bolts

b. Barrel-former bolts Expansion Criteria

a. Confirmation that more than 5% of the baffle-former bolts actually examined on the four baffle plates at the largest distance from the core (presumed to be the lowest dose locations) contain unacceptable indications shall require UT examination of the lower support column bolts within the next three fuel cycles.

b. Confirmation that more than 5% of the lower support column bolts actually examined contain unacceptable indications shall require UT examination of the barrel-former bolts.

Applicability All plants Examination Acceptance Criteria (Note 1)

Volumetric (UT) examination.

The examination acceptance criteria for the UT of the baffle-former bolts shall be established as part of the examination technical justification.

MRP-227-A Primary Inspection Components Page 15 of 16 Additional Examination Acceptance Criteria NIA NIA Expansion Criteria NIA NIA Expansion Link@)

None None Item Baffle-Former Assembly Assembly Alignment and Interfacing Components lnternals hold down spring Applicability All plants All plants with 304 stainless steel hold down springs Examination Acceptance Criteria (Note I)

Visual (VT-3) examination.

The specific relevant conditions are evidence of abnormal interaction with fuel assemblies, gaps along high fluence shroud plate joints, vertical displacement of shroud plates near high fluence joints, and broken or damaged edge bolt locking systems along high f l uence baffle plate joints.

Direct physical measurement of spring height.

The examination acceptance criterion for this measurement is that the remaining compressible height of the spring shall provide hold-down forces within the plant-specific design tolerance.

MRP-227-A Primary Inspection Components Notes to Table 5-3:

1. The examination acceptance criterion for visual examination is the absence of the specified relevant condition(s).

2. The lower core barrel flange weld may alternatively be designated as the core barrel-to-support plate weld in some Westinghouse plant designs.

Page 16 of 16 Additional Examination Acceptance Criteria N/A Item Thermal Shield Assembly Thermal shield fixtures Applicability All plants with thermal shields Examination Acceptance Criteria (Note 1)

Visual (VT-3) examination.

The specific relevant conditions for thermal shield flexures are excessive wear, fracture, or complete separation.

Expansion Link@)

None Expansion Criteria N/A