CNRO-2002-00016, Entergy Operations Inc., Use of Mechanical Nozzle Seal Assemblies for Arkansas Nuclear One, Unit 2

Entergy Operations Inc., Use of Mechanical Nozzle Seal Assemblies for Arkansas Nuclear One, Unit 2

ML021080271
Person / Time
Site:	Arkansas Nuclear
Issue date:	04/04/2002
From:	Krupa M Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNRO-2002-00016
Download: ML021080271 (18)

Text

S~1340 Entergy Operations, Echelon ParkwayInc.

Jackson, MS 39213-8298 Tel 6013368 5758 Michael A. Krupa Director Nuclear Safety &Licensing CNRO-2002-00018 April 4, 2002 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Entergy Operations, Inc.

Use of Mechanical Nozzle Seal Assemblies Arkansas Nuclear One, Unit 2 Docket No. 50-368 License No. NPF-6

REFERENCE:

1. Letter CNRO-2002-00012 from Entergy Operations, Inc. to the NRC, "Use of Mechanical Nozzle Seal Assemblies," dated March 15, 2002

2. Letter CNRO-2002-00010 from Entergy Operations, Inc. to the NRC, "Use of Mechanical Nozzle Seal Assemblies," dated March 6, 2002

Dear Sir or Madam:

In Reference Letter #1, Entergy Operations, Inc. (Entergy) submitted to the NRC staff a request (ANO2-R&R-002) to use the new design of the Mechanical Nozzle Seal Assembly (MNSA-2) In applications at Arkansas Nuclear One, Unit 2 (ANO-2). To assist the staff with its review of the request, Entergy Is submitting via this letter the revised stress report, Westinghouse Design Report No. DAR-CI-02-2, "Addendum to CENC-1224 Analytical Report for the Arkansas Nuclear One Unit 2 Pressurizer." This report, contained in , provides methodology used to determine acceptable application of the MNSA-2 in conformance with ASME Code requirements. It also reflects information regarding finite element analysis resulting from questions raised by the staff during the review of a similar request made by the Waterford Steam Electric Station, Unit 3 (see Reference Letter #2).

Entergy considers the Information contained In Enclosure 2 to be proprietary and confidential pursuant to 10 CFR 2.790(a)(4) and 10 CFR 9.17(a)(4). As such, Entergy requests this information be withheld from public disclosure. The affidavit supporting this request Is provided in Enclosure 1. Because the vast majority of the information contained in is considered proprietary, Entergy considers it Impractical to provide a nonproprietary version.

CNRO-2002-00018 Page 2 of 2 Entergy is also providing responses to questions raised by the NRC staff at a meeting held on January 31, 2002, at which Entergy representatives discussed the MNSA-2 design and application with staff representatives and during conference calls held on March 15 and March 26, 2002, to discuss Request ANO2-R&R-002. Responses to these questions are contained in Enclosure 3.

In the March 26, 2002, telephone conference call, NRC staff requested that Entergyagree to visually Inspect for leakage the counter-bore/annulusregion of each Installed MNSA-2 device during each refueling outage. Entergy agrees to perform this visual inspection and also, upon discovering leakage that occurred during the operating cycle, to remove the MNSA-2 and Inspect it and the surroundingpressurizersurface for corrosion.

This letter contains one commitment as denoted above in bold, italicized text.

Should you have any questions regarding this request, please contact Guy Davant at (601) 368-5756.

Very truly yours, MAK/GHD/baa

Enclosures:

1. Affidavit for Withholding Information from Public Disclosure

2. Westinghouse Design Report No. DAR-CI-02-2, "Addendum to CENC-1224 Analytical Report for the Arkansas Nuclear One Unit 2 Pressurizer"

3. Responses to NRC Questions Regarding the MNSA-2 Design cc: Mr. C. G. Anderson (ANO) (wlo)

Mr. W. R. Campbell (ECH) (w/o)

Mr. J. K. Thayer (ECH) (wlo)

Mr. G. A. Williams (ECH) (w/o)

Mr. T. W. Alexion, NRR Project Manager (ANO-2)

Mr. R. L. Bywater, NRC Senior Resident Inspector (ANO) (w/o)

Mr. E. W. Merschoff, NRC Region IVRegional Administrator (w/o)

ENCLOSURE I CNRO-2002-00018 AFFIDAVIT FOR WITHHOLDING INFORMATION FROM PUBLIC DISCLOSURE to CNRO-2002-00018 Page 1 of 2 AFFIDAVIT FOR WITHHOLDING INFORMATION FROM PUBLIC DISCLOSURE I, Michael A. Krupa, Director, Nuclear Safety and Licensing, of Entergy Operations, Inc.

(Entergy) do hereby affirm and state:

1. Entergy is providing information in support of a request made to the NRC staff. The document being provided in Enclosure 2 (Westinghouse Design Report No.

DAR-CI-02-1, uAddendum to CENC-1224 Analytical Report for the Arkansas Nuclear One Unit 2 Pressurizer") of this letter contains technical information developed by Entergy and Westinghouse and owned by Entergy regarding the Improved Mechanical Nozzle Seal Assembly (MNSA) design.

Enclosure 2 contains proprietary commercial information that should be held in confidence by the NRC pursuant to 10 CFR 9.17(a)(4) and the policy reflected in 10 CFR 2.790, because:

1. The information Is being held in confidence by Entergy. Because of the substantial investment made to develop this information and its commercial viability, Entergy has not released it to the'public.

ii. The Information Is of a type that is customarily held in confidence by Entergy and not disclosed to the public.

ii.1 The information reveals distinguishing aspects of the improved MNSA design where its use by other companies without license or agreement from Entergy would prevent Entergy from recouping its investment in developing the component.

ii.2 The information contains supporting data relative to the improved MNSA design, the application of which increases Entergy's ability to recoup its investment in developing the component.

ii.3 The use of the Information by another company would reduce its expenditure of resources In the design or licensing of a similar product.

iii. The information is being transmitted to the NRC in confidence with the understanding that the NRC will hold the information in confidence while determining if it meets the requirements of 10 CFR 2.790(b)(4). If the NRC determines that the Information does not meet the requirements of 10 CFR 2.790(b)(4), the Information will be returned to Entergy.

Enclosure 1 to CNRO-2002-00018 Page 2 of 2 iv. The information is not available in public sources and could not be gathered readily from other publicly available information. The information has been developed by Entergy and Westinghouse and has not been made available to the public by either company.

v. The information sought to be withheld is that which Is contained in Enclosure 2 of this submittal. This information is submitted for use by the NRC staff and is expected to be applicable in other license submittals for justification of the use of the Improved MNSA design. The information provided in this document represents a substantial Investment, public disclosure of which would reduce Entergy's ability to recoup part or all of that Investment.

2. Accordingly, Entergy requests that the designated document be withheld from public disclosure pursuant to 10 CFR 2.790(a)(4) and 10 CFR 9.17(a)(4).

I declare under penalty of perjury that the foregoing is true and correct.

Executed on April 4, 2002 Michael A. Krupa

ENCLOSURE 3 CNRO-2002-00018 RESPONSES TO NRC QUESTIONS REGARDING THE MNSA-2 DESIGN to CNRO-2002-00018 Page 1 of 12 RESPONSES TO NRC QUESTIONS REGARDING THE MNSA-2 DESIGN BACKGROUND On January 31, 2002, representatives from Entergy Operations, Inc. (Entergy) met with representatives of the NRC staff to discuss Entergy's intent to request use of an improved Mechanical Nozzle Seal Assembly (MNSA-2) design at Arkansas Nuclear One, Unit 2 (ANO-2) and Waterford Steam Electric Station, Unit 3 (Waterford 3). In telephone conference calls on March 15 and March 26, 2002, representatives from Entergy and the NRC staff discussed Request ANO2-R&R-002 pertaining to use of the MNSA-2 device.

During these discussions, the staff raised several questions regarding the MNSA-2 design and requested that Entergy respond in order to support their review of the request. These questions and their associated responses are provided below.

QUESTIONS

1. The telltale leak-off connection of the MNSA-2 will allow oxygen ingress to the cavity/crevice between the seals. Please address corrosion of all parts. Note the similarity of environment to the control rod drive mechanism (CRDM) corrosion issues and potential for accelerated corrosion of Alloy 600 in potentially oxygenated crevice.

Response

The MNSA-2 design has a primary Grafoil seal that is maintained under constant load using the Belleville washer stacks as a preloading mechanism that can accommodate a fair amount of temperature differential growth between the bolts and compression collar.

In the unlikely event of leakage past the primary seal, fluid enters an annulus between the sleeve/nozzle either directly along the sleeve outer diameter (OD), or seeps through the primary seal outward into a narrow passage that is blocked to the outside region by a secondary Grafoil tape seal. The fluid then would be channeled through passages into the previously mentioned cavity between the sleeve/nozzle and compression collar inner diameter (ID). From there, the fluid will escape through a small fitting into a telltale tube. Failure of the secondary seal is unlikely since it is not subjected to any pressure, except in the case of completely clogged leak-off channels, which could only occur if the primary seal failed. A discussion dealing with the specific corrosion issues was provided in Appendix I of Request ANO2-R&R-002, Rev. 01.

To ensure any leakage is discovered, Entergy will visually inspect each installed MNSA-2 device during each refueling outage. This inspection will include the leak-off line and the counter-borelannulus region. Upon discovering leakage that occurred during the operating cycle, Entergy will remove the MNSA-2 and inspect it and the surrounding pressurizer surface for corrosion.

Letter CNRO-2002-00012 from Entergy to the NRC, "Use of Mechanical Nozzle Seal Assemblies,"

dated March 15, 2002 to CNRO-2002-00018 Page 2 of 12

2. Reinforcement calculations should show compliance to Code.

Response

The reinforcement calculations are in strict compliance with the ASME Code and are presented as such in the new stress calculations for the pressurizer. The calculations are located in Section 6.3.2 of Attachment C (Calculation No. CN-CI-02-12, Rev. 0) of the ANO-2 design report addendum.

3. Regarding the limit of compression, what are the limits for maximum torque and what part(s) are limiting (weakest link)?

Response

The stress calculations document the installation torque values (e.g. 17 ft-lbs.). The tolerance is +/- 1 ft-lb., which is less than 4% of nominal. Most of the calculation procedures utilize nominal values combined with conservative assumptions; thus, use of nominal figures is justified. Because of different diameters in heater sleeves and in instrument nozzles, different torque values are used for the MNSA-2 attachment points.

The weakest areas of the design are the threaded rods (thus also tapped holes in the vessel shell) and the compression collar. For the larger diameter pressurizer penetrations (heater sleeves) the threaded rods are limiting; for the smaller diameter instrument nozzles, the compression collars are limiting.

For the ANO-2 MNSA-2s, the following installation torque values are specified and will be incorporated into the installation procedures.

LOCATIONS TORQUE VALUES Heater Sleeve MNSA-2 17 ft-lbs. + 1 ft-lb.

Side Shell Pressurizer MNSA-2 27 ft-lbs. + 1 ft-lb.

Lower Level Instrument MNSA-2 24 ft-lbs. + 1 ft-lb.

Upper Level Instrument MNSA-2 24 ft-lbs. + 1 ft-lb.

Upper Pressure Instrument MNSA-2 24 ft-lbs. + 1 ft-lb.

Upper Vent MNSA-2 24 ft-lbs. + 1 ft-lb.

4. What is the increase in cumulative usage factor?

a. MNSA-2 vs. original design?

b. MNSA-2 vs. original MNSA-1?

to CNRO-2002-00018 Page 3 of 12

Response

LOCATIONS USAGE FACTORS MNSA-2 OriginalDesign MNSA-1 Half Nozzle Counter-bore/Bore 0.799 0.279 N/A 0.106 Tapped Hole 0.606* N/A 0.539* N/A

• The usage factor of 0.606 is determined for the outermost heater sleeve in the ANO-2 pressurizer due to installing a MNSA-2, in the tapped hole region, for a conservative number of 500 heat-up and cool-down cycles. The usage factor would be similar for an original MNSA-1. The usage factor of 0.799 occurring in the counter-bore region of the side shell temperature nozzle location is not applicable for the original MNSA-1.

5. Address life extension considerations, if applicable. Is the number of fatigue cycles chosen for analysis consistent with life extension? Include Part 54 analysis.

Response

An application for license renewal for ANO-2 is planned for fall of 2003. Before a license renewal application Is submitted for ANO-2, Entergy must address aging effects for the MNSA-2 (if installed) and the pressurizer. If either is qualified based on the end of the 40-year license term, the qualifying analyses will be evaluated as time-limited aging analyses in accordance with IOCFR54.21. The most likely option to show the analyses acceptable for the period of extended operation is to show that the analyses remain valid for the period. It is anticipated that during the integrated plant assessment for license renewal, the projection of design cycles through the period of extended operation will remain less than the original number of design cycles for the pressurizer.

Therefore, if the MNSA-2 and the pressurizer are qualified to the original number of design cycles, the analyses will remain valid for the period of extended operation.

As applicable to ANO-2, the MNSA-2 component, vessel threads, counter bore, etc. are being qualified for fatigue cycles consistent with the original 40-year design basis for the reactor coolant system. This qualifies the MNSA-2 component, for the period of license renewal since after Refueling Outage 15, there are slightly over 36 years remaining on the 60-year license term assuming license renewal.

Re-analyses are being completed that will verify the pressurizer, as modified to support the MNSA-2, remains acceptable for the full number of cycles assumed in the original design basis for ANO-2. Therefore, this modification is not expected to reduce the number of allowable cycles for the pressurizer.

6. Provide and compare values of coefficlent of thermal expansion for the MNSA-2 clamp and pressurizer vessel materials.

to CNRO-2002-00018 Page 4 of 12

Response

The stress calculations include, in tabular form, thermal expansion coefficients from the ASME Code for the pressurizer vessel material and for all MNSA-2 materials. These tables are included in Section 6.2.4.1 of Attachments A and B of the design report addendum for the ANO- pressurizer.

7. Address and justify stress concentration values for the counterbore region. Are these values taken from Peterson or finite element analysis (FEA)? Why not use limiting stress concentration factor (SCF) of 5 from ASME?. It appeared the January 31, 2002, presentation was inconsistent. Apparently for some calculations, the ASME limiting value was used, for others Peterson, and for others FEA. Entergy should select, use, and defend the appropriate value.

Response

Section 3.1 of Attachment C of the ANO-2design report, Assumption 4 (page 12) states that the fatigue strength reduction factor (FSRF) for the counterbore region is 3.558 for a spherical shell and 3.01 for a cylindrical shell - both values which come from Peterson. However, the report also states in this same assumption that the FSRF is conservatively assumed to be 4.0. For the tapped hole region, the FSRF value of 4.0 is used, which is the maximum per Paragraph NB-3232.3 (c) of the ASME Code Section Ill, as recommended by the NRC on the Calvert Cliffs MNSA project.

For the grooved section in the MNSA-2 clamp a FSRF from Peterson was unknown.

Thus, a very conservative FSRF of 5 was used, which is the maximum value per Paragraph NB-3222.4 (e) (2) of the ASME Code Section III for fatigue evaluation. The table below specifies the FSRFs used for the different locations.

FATIGUE STRENGTH REDUCTION FACTORS Location Peterson ASME Code Values Used Counter Bore Region 3.558 4 4 Tapped Hole Region N/A 4 4 Nozzle Groove <<5 5 5

8. If FEA was used to determine the stress concentration factor, show that the mesh was fine enough to accurately determine the value.

Response

The intent of the FEA was not to determine the FSRFs. The intent was to use either the ASME Code or the Peterson values to determine the FSRF. The FEAs were performed to determine the interaction between the counterbore and tapped hole stresses, as well as between adjacent MNSA-2 stresses. The current model is a flat plate model used to CNRO-2002-00018 Page 5 of 12 strictly to determine interaction stresses. The FSRF numbers are explained in the response to Issue #7, above.

9. Regarding the thermal model was the model axy-symmetric? Was the bolting material considered as a heat sink? Is insulation required?

Response

The thermal model used for "steady-state" and "transient" thermal analyses of the pressurizer shell and the MNSA-2 components is an axis-symmetric model. The MNSA-2 was adequately modeled as a symmetric structure. A thin tube section with heat transfer characteristics that simulated those of four "fins" each modeled the four tie rods and the four threaded rods. The pressurizer vessel acts as the heat source with the MNSA-2 components (compression collar, heater sleeve, flanges, tie rods, threaded rods, impact plate, Belleville washers) thermally interconnected where they are in contact with each other. The model permitted heat transfer due to axial conduction and due to radial convection with the environment at 1200 F. Based on the spreadsheet computations, it was verified that the non-insulated MNSA-2 would result in less desirable temperature differentials than the insulated MNSA-2 design. Since Entergy desired to have the option of not insulating the MNSA-2 after installation, this more conservative situation was used as the basis for the analyses. The case of insulated MNSA-2 installations is bounded. The comparisons between the spreadsheet computations and the FEA results can be found in Appendix B-5 of Attachments A and B of the ANO-2 design report.

10. Address the effect on the thermal analysis of the studs bottomed into the tapped holes.

The stud is torqued Into the hole and stud expansion is greater than the pressurizer creating interference stresses in the hole.

Response

The differential thermal expansion stress due to dissimilar materials is now being considered in the stress and fatigue evaluation of the tapped holes with the threaded rods inserted. Utilizing the more conservative stress results from the classical methodology, a maximum usage factor of 0.606 is obtained for a conservative number of 500 heat-up and cool-down cycles combined with 200 leak test cycles. A significant reduction in the usage factors would be realized if the currently specified number of cycles are reduced to reflect actual plant operations. The usage factor calculations for the tapped holes in the pressurizer can be found in Sections 6.3.6, 6.3.10, 6.3.14, 6.3.18, and 6.3.21 of Attachment C of the ANO-2 design report addendum. The corresponding usage factor calculations for the threaded rods of the MNSA-2 are contained in Section 6.3.4 of both Attachments A and B of the report addendum.

11. Address preload credited to reduce ejection impact.

to CNRO-2002-00018 Page 6 of 12

Response

Each MNSA-2 stress analysis Is quite specific about the gap or preload conditions at the anti-ejection plate and the changes of these conditions as a result of heat-up. Typically the worst impact load results when the MNSA-2 assembly is hot since this causes either the gap to increase or the preload to decrease. In case of an initial preload (ANO-2 heater sleeve MNSA-2), a moderate load of 3,623 lbs. (Section 6.3.1.2.3 of Attachment A of the ANO-2 design report) is transmitted into the J-weld that is fully accounted for in the evaluations of the pressurizer shell, attachment locations/heater sleeve. At cold conditions this pre-load would reduce based on the ratio of cold versus hot bolt pre-load (2,100 I 3,050 = 0.689). An allowable load of 4,770 lbs. is determined in Section 6.3.25.3 of Attachment C of the design report addendum. This allowable load is based on a minimum weld shear length and a maximum shear stress allowable of 10% of Yield (based on 1983 conservative directive to utilities to protect J-weld from cracking, with copy included in Appendix B of Attachment C).

The gap/pre-load conditions determined for the MNSA-2 are being addressed by the installation procedures.

12. Provide an analysis to show the effect of the J-weld present and not present.

Response

The MNSA-2 stress analyses consider the loads throughout the MNSA-2 and those into the pressurizer attachment points for both situations, prior to heater/sleeve or nozzle ejection and after complete failure of the J-weld.

13. Provide or justify Grafoil compression curves used for compression loading.

Response

The Grafoil compression curves are included in the MNSA-2 stress analyses, Appendix B-2 for Attachments A and B of the Design Report. Their use is discussed in the calculation sections of Attachments A and B of the Design Report.

14. Provide a commitment to inspect the MNSA-2 leak-off as part of Generic Letter (GL) 88-05 walkdown.

Response

Entergy agrees to perform, during each refueling outage, a visual inspection of each installed MNSA-2 device. This inspection will include the leak-off line and the counter bore/annulus region. Upon discovering leakage that occurred during the operating cycle, Entergy will remove the MNSA-2 and inspect it and the surrounding pressurizer surface for corrosion.

15. Regarding flaw analysis, justify flaw growth from fatigue and stress corrosion cracking.

Include life extension, if applicable. If analysis in the topical report is used, must justify applicability. Address differences from topical report.

to CNRO-2002-00018 Page 7 of 12

Response

Bounding flaw evaluations will be performed for all pressurizer nozzles in accordance with the 1992 ASME Code Section XI, IWB-3600 to address MNSA-2 installation.

Existing site-specific heater sleeve flaw evaluations are being updated to address the installation of the MNSA-2 clamp. Flaw growth due to fatigue and stress corrosion cracking has been previously considered and will be re-evaluated for potential MNSA-2 installation effects.

16. Provide information to justify expedited review by NRC based on mfour pillars". Address man-rem savings as result of MNSA use and any cost savings.

Response

The nuclear utility industry has experienced primary water stress corrosion cracking (PWSCC). This cracking phenomenon occurs near the J-groove weld on small bore penetrations on the NSSS. With time, a crack propagates from the ID of the nozzle to the OD causing a primary pressure leak that could potentially result in forced or extended outages. The predictability of these leaks is not well defined. Some industry experts on the subject have stated that the time-to-failure can only be predicted within a 10 to 15-year band. Therefore, it is difficult to determine when and if the existing nozzles should be replaced. The only advantage replacement nozzles have over the original nozzles is the quality of the material used in the replacement nozzles. The replacement nozzle material, Alloy 690, is less susceptible to PWSCC than the original Alloy 600 material.

Replacement/repair methods require at least 5 to 10 days to implement, leave high residual stresses, are very labor intensive, involve high radiation exposure, and are extremely costly. Although the original MNSA design could have been qualified and applied to the ANO-2 pressurizer nozzles and heater sleeves, Entergy desires a more reliable, standardized design that can be pre-manufactured and ready to install, as opposed to the custom design and machining required on the original MNSA. The benefits to Entergy, and the industry, in approving the MNSA-2 relief request are described below:

1. Installation time Installation time should be reduced from 5 to 10 days on a welded repair to approximately I day utilizing the proposed MNSA-2. Tooling and equipment can be pre-staged, and maintenance personnel trained in advance for this task. In contrast to the MNSA-2, the original MNSA requires as-built dimensions of the vessel to heater sleeve interface, and for nozzles, the dimensions of connected piping or tubing to allow design of the anti-ejection provisions and seating components. Typical practice is to take action to acquire a MNSA once a leaking nozzle is discovered. Such action involves:

0 Obtaining field measurements of the nozzle area 6 Preparing custom design drawings for the specific application to CNRO-2002-00018 Page 8 of 12

"* Machining the MNSA components

"* Shipping the MNSA tooling to the site

"* Installing the MNSA With the MNSA-2, as-built dimensions are not required, the components can be pre-fabricated and shipped to the site and available for installation prior to an actual need. Therefore, several days can be saved using the MNSA-2 versus the original MNSA.

2. Labor man-hours Current nozzle weld repair methods are labor intensive, requiring separate crews for welding, field machining, insulating, scaffolding, HP and QA support. The MNSA-2 design eliminates some field machining and all welding, and reduces the overall repair/replacement period from a maximum of 5 to 10 days to approximately 1 day. This dramatically decreases the required man-hours.

3. Costs The cost for repairing 12 heater sleeves at ANO-2 during a mid-cycle outage was approximately $2,000,000, or $166,667 per nozzle. These costs included the stress analyses, Section Xl flaw analysis, design change package preparation, and installation costs. Lost generation revenues are not included.

The estimated costs to design, qualify, and install MNSA-2s on 12 heater sleeves is approximately $950,000. This estimate includes the costs for design, development, and an enveloping qualification that encompasses the applicable pressurizer nozzle and heater sleeve locations for ANO-1, - 2, and Waterford 3. This represents potential savings of 50% over welded repairs. Future installations will cost even less since the one-time expenses will not be included. Therefore, total costs for fabricating and installing the MNSA-2 are expected to be less than

$13,000 per nozzle, which is significantly less than the $166,667 per welded nozzle described above. This significant cost reduction is due to the reduction in labor hours, one-time design, testing, enveloping analyses for all locations, and onsite personnel performing installation.

4. Radiation Exposure Levels of radiation exposure associated with current weld repair methods are high because the nozzle penetrations are part of the primary pressure boundary, and also due to the time required for the repair process. The "stay time" and number of personnel required is significantly reduced by eliminating welding and some field machining activities. This results In a reduced estimated radiation exposure of approximately 66%. This does not include the elimination of potential airborne contaminants since welding Is not required. Additionally, potential for personnel contamination is significantly reduced because the pressure boundary is not to CNRO-2002-00018 Page 9 of 12 breached. Specific dose information is provided in the response to Issue #17, below.

5. Forced or Extended Outages The MNSA-2 is expected to reduce outage time significantly in the event a failure were to occur on one or more of the pressurizer nozzles or heater sleeves. The schedule impact on a forced outage could be reduced from 5 to 10 days for a welded repair to approximately I day for a MNSA-2 installation.

6. Lost revenue The cost of lost generating revenue and outage expenses for a single nuclear unit may be as high as $1 million per day. Thus, the total cost impact of weld repairing a leaking nozzle could range from $5 to 10 million. Using the MNSA-2 design, the impact would be reduced substantially assuming a one-day installation period.

7. Safety The MNSA-2 is designed with redundancy, essentially eliminating concern for PWSCC. The design does not credit the J-weld, assuming that the nozzle is completely severed at or near the weld. Additionally, the design provides a reactor coolant leak-off feature diverting potential leakage that could occur if the primary seal were to degrade. The original MNSA design includes leak-off provisions.

However, leakage is significantly less likely on the MNSA-2 due to the superior seal seating design and the live loading of the seal. (See the discussion regarding the leak-off connection in the response to Issue #1, above.)

Beyond the MNSA-2 component itself, safety concerns associated with core off load or operation at reduced inventory are also minimized because the RCS does not have to be drained to Install the MNSA-2. Field machining tooling is designed to allow the counterbore for the seal to be installed without disconnecting the connected piping or tubing from instrument nozzles and without removing heater elements from heater sleeves.

17. Provide a list of previous MNSA installations, with Man-rem savings.

Response

MNSA repairs have been installed at the following plants and locations:

"* Maine Yankee - side pressurizer

"* SONGS 2 - 2 Steam Generator, 2 Bottom Pressurizer, 2 Hot Leg

"* SONGS 3 - 2 Bottom Pressurizer, Side Pressurizer

"* Waterford 3 - 3 hot leg nozzles

"* Calvert Cliffs 2 - Pressurizer side RTD nozzle, 2 Bottom Pressurizer Nozzles to CNRO-2002-00018 Page 10 of 12

"* Calvert Cliffs I - Pressurizer side RTD nozzle, 2 Bottom Pressurizer Nozzles, 4 Top Pressurizer Nozzles

"* Palo Verde 3 - 1 hot leg RTD nozzle

"* Fort Calhoun - 1 Pressurizer Upper Head RTD Nozzle Entergy does not have access to the exposure records for these plants, but for comparison purposes a simplistic dose savings analysis is performed below. The analysis uses actual data from the 12 heater sleeves repaired at ANO-2 and an assumed total of 50 man-hours/nozzle if Entergy had installed the MNSA-2 instead of the welded repair.

Dose Received 27,345 milli-rem (mr)

Radiation Work Permit Hours 1,748 man-hrs Hours / Nozzle 1,748 man-hrs / 12 nozzles = 145 man-hr/nozzle Dose Rate 27, 345 mr / 1,748 man-hr = 15.64 mr/man-hr Dose / Nozzle 15.64 mr/man-hr x 145 man-hrs/nozzle =

2,267.8 mr/nozzle Estimated Time to Install a 50 man-hrs MNSA-2 Dose per Nozzle for MNSA-2 15.64 mr x 50 man-hrs = 782 mr/nozzle Dose Savings using MNSA-2 2,267.8 mr/nozzle - 782 mr/nozzle =

1,485.8 mr/nozzle Total Dose using MNSA-2 782 mr/nozzle x 12 nozzles = 9,384 mr Instead of Welded Repair If the MNSA-2 design had been available at ANO-2, a total dosesavings of 17,961 mr (27,345 mr - 9,384 mr) would have been realized. This is approximately a 66% saving in radiation exposure.

18. The use of the counter-bore hole has the potential for problems to occur since there is no way to do visual inspections of the area. One problem is for corrosion of the pressurizer material and cracking of the bolts if leakage occurs in the annulus region on the external edge of the hole. Explain how the design eliminates leakage in the annulus region between the pressurizer and the MNSA-2.

I. --

to CNRO-2002-00018 Page 11 of 12

Response

Unlike the original MNSA design, the MNSA-2 has a secondary seal. Ifthe primary seal were to fail, the secondary sea? would channel any leakage through the leak-off tube away from the bolting and pressurizer surface. Additionally, even if there were leakage in the annulus region or around the bolting, the area is open and available for visual inspection. As discussed in the responses to Questions 1 and 14, above, Entergy will visually inspect for leakage each installed MNSA-2 device during each refueling outage.

19. Regarding the installation of the MNSA, what steps will Entergy take to assure that the area of the pressurizer adjacent to the annulus is in a condition to assure that the MNSA will seal correctly?

Response

The MNSA-2 seating surface Is machined to a 125 finish.

20. What inspections will Entergy perform to verify pressurizer thickness prior to drilling for the counter-bore and the four tie rod holes?

Response

Insulation will be removed for installation allowing the surface to be inspected for any degradation. By design the MNSA-2 is qualified to meet minimum wall thickness requirements. Installation procedures require inspections to verify that the bolt hole depth and counter-bore are within design depths.

Calculation No. CN-CI-02-12, Rev. 0, Section 6.3.2, beginning on page 23 of 245, addresses the reinforcement requirements for modification to the pressurizer to account for the additional area removed by machining the tapped holes and the counter-bore.

This report updates the reinforcement calculations in the original ANO-2 pressurizer stress report (CENC-1224).

The updated reinforcement calculations use the minimum vessel tolerances on design thickness (the same as was performed in the original stress report CENC-1224) and the maximum tolerances on the machined tapped holes and counter-bore. The minimum required thickness of the pressurizer bottom head and shell is used in the calculations in accordance with the ASME Section III NB-3332 and the original pressurizer stress report, CENC-1224.

The resulting calculations show that substantial margin exists between the area available for reinforcement compared to the area required for reinforcement, taking into account material removal due to the introduction of the tapped holes and counter-bore required for MNSA-2 installation.

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21. If leakage occurs, what is the impact on the Grafoil seal?

Response

None. The Grafoil seal is designed to come in contact with the RC. Additionally if the primary seal were to degrade, leakage would only be seepage, since the through wall flaws due to PWSCC are very tight. No steam cuffing would occur. Grafoil seals are used all over the plant and is a proven sealing material (e.g. ICI Nozzles).

22. Appendix I states that the corrosion rate data and the bounding allowable material loss calculations for repair life is 56 years for a pressurizer nozzle. The report that was referenced did not consider the impact of the counter-bore. Does the counter-bore effect the calculations for determining the impact of corrosion on the integrity of the pressurizer?

Response

The counter-bore does not effect the calculations and has no impact on the integrity of the pressurizer due to corrosion. The counter-bore area contains a seal, as discussed in the response to Question 1, above. Therefore, this area is expected to remain dry; hence no corrosion is expected. However, as discussed in Questions 1 and 14, above, Entergy will visually inspect for leakage each installed MNSA-2 during each refueling outage. This inspection will include the leak-off line and the counter-bore/annulus region. Upon discovering leakage that occurred during the operating cycle, Entergy will remove the MNSA-2 and inspect It and the surrounding pressurizer surface for corrosion.