ML080650059

Relaxation of the First Revised Order EA-03-009 TAC No. MD8204)

ML080650059
Person / Time
Site:	Watts Bar
Issue date:	03/12/2008
From:	Catherine Haney Plant Licensing Branch III-2
To:	Campbell W Tennessee Valley Authority
Chernoff M, NRR/DORL, 415-4041
References
EA-03-009, TAC MD8204
Download: ML080650059 (11)

Text

March 12, 2008 Mr. William R. Campbell, Jr.

Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

WATTS BAR NUCLEAR PLANT, UNIT 1 - RELAXATION OF THE FIRST REVISED ORDER EA-03-009 (TAC NO. MD8204)

Dear Mr. Campbell:

By letter dated March 3, 2008, Tennessee Valley Authority (TVA, the licensee), requested relaxation from certain inspection requirements of the First Revised Order EA-03-009, dated February 20, 2004 (ADAMS Accession No. ML040220181). TVA has requested relaxation from the Order for the inspection at Watts Bar Nuclear Plant (WBN), Unit 1, to the specific examination criteria applicable to penetration nozzle number 74.

The NRC staff has reviewed and evaluated the information provided by TVA in support of this request. The staff concludes that the licensees proposed alternative inspection, to perform the ultrasonic testing of penetration nozzle Number 74 at WBN, Unit 1, to the maximum extent practical below the J-groove weld, with a minimum inspection distance of 0.91-inch, provides reasonable assurance of the structural integrity of the RPV upper head, associated penetration nozzle and J-groove weld. Further inspections of this penetration nozzle in accordance with Section IV.C.(5)(b), of the First Revised NRC Order EA-03-009 dated February 20, 2004, would result in hardship without a compensating increase in the level of quality and safety. Therefore, the staff has determined that the licensee has demonstrated good cause for relaxation, and pursuant to Section IV.F, of the First Revised Order EA-03-009 dated February 20, 2004, the staff authorizes the proposed alternative inspection until the First Revised NRC Order EA-03-009 is replaced or rescinded.

W. Campbell, Jr. The NRC staff's review is provided in the enclosed Safety Evaluation. If you have any questions, please contact L. Raghavan, 301-415-2429.

Sincerely,

/RA/

Catherine Haney, Director Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-390

Enclosure:

Safety Evaluation cc: See next page

ML080650059 NRR-088 OGC DORL/D OFFICE DORL/PM WBSPB /LA DCI/BC WBSPB/BC NAME BClayton TChan DRoth - NLO LRaghavan CHaney MChernoff 03 / 12 /08 Memo dated 03 / 12 /08 DATE 03 / 12 /08 03/04 /08 03/07/2008 03 / 12 /08 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FIRST REVISED ORDER EA-03-009 RELAXATION REQUEST, ALTERNATE EXAMINATION COVERAGE FOR REACTOR PRESSURE VESSEL HEAD PENETRATION NOZZLES WATTS BAR NUCLEAR PLANT, UNIT 1 TENNESSEE VALLEY AUTHORITY DOCKET NUMBER 50-390

1.0 INTRODUCTION

The First Revised Nuclear Regulatory Commission (NRC) Order EA-03-009 (Order), issued on February 20, 2004, requires specific examinations of the reactor pressure vessel (RPV) head and RPV head penetration nozzles of all pressurized water reactor plants.Section IV.F of the Order states that requests for relaxation of the Order associated with specific penetration nozzles will be evaluated by the NRC staff using the procedure for evaluating proposed alternatives to the American Society of Mechanical Engineers Code in accordance with Title 10 of the Code of Federal Regulations, Part 50, Section 55a(a)(3).Section IV.F of the First Revised Order states that a request for relaxation regarding inspection of specific nozzles shall address the following criteria: (1) the proposed alternative(s) for inspection of specific nozzles will provide an acceptable level of quality and safety, or (2) compliance with this First Revised Order for specific nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Watts Bar Nuclear Plant (WBN), Unit 1, station susceptibility category is classified as low based on a calculated value of less than 8 effective degradation years and no previous findings as of the beginning of the Cycle 8 Refueling Outage. For plants determined to have a low susceptibility to primary water stress corrosion cracking in accordance with Sections IV.A, IV.B, and IV.C.(3) of the Order, the following inspection is required to be performed by February 11, 2008, in accordance with Section IV.C.(5)(b) of the First Revised Order. (Note: By letter dated January 27, 2006, the NRC staff approved an alternative inspection schedule to meet the Order for Watts Bar Unit 1. Specifically, the nonvisual nondestructive examination in accordance with the requirements of Paragraph IV.C.(5)(b) of the Order are to be completed prior to restarting the facility from the Cycle 8 refueling outage (current outage).

(b) For each penetration, perform a nonvisual nondestructive examination (NDE) in accordance with either (i), (ii), or (iii):

(i) Ultrasonic testing of the RPV head penetration nozzle volume (i.e., nozzle base material) from two inches above the highest point of the root of the

J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to two inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than two inches); or from two inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to one inch below the lowest point at the toe of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) and including all RPV head penetration nozzle surfaces below the J-groove weld that have an operating stress level (including all residual and normal operation stresses) of 20 ksi tension and greater. In addition, an assessment shall be made to determine if leakage has occurred into the annulus between the RPV head penetration nozzle and the RPV head low-alloy steel.

(ii) Eddy current testing or dye penetrant testing of the entire wetted surface of the J-groove weld and the wetted surface of the RPV head penetration nozzle base material from at least two inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to two inches below the lowest point at the toe of the J-groove weld on a horizontal plane perpendicular to the nozzle axis (or the bottom of the nozzle if less than two inches); Or from two inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to one inch below the lowest point at the toe of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) and including all RPV head penetration nozzle surfaces below the J-groove weld have an operating stress level (including all residual and normal operation stresses) of 20 ksi tension and greater.

(iii) A combination of (i) and (ii) to cover equivalent volumes, surfaces, and leak paths of the RPV head penetration nozzle base material and J-groove weld as described in (i) and (ii). Substitution of a portion of a volumetric exam on a nozzle with a surface examination may be performed with the following requirements:

1. On nozzle material below the J-groove weld, both the outside diameter and inside diameter surfaces of the nozzle must be examined.

2. On nozzle material above the J-groove weld, surface examination of the inside diameter surface of the nozzle is permitted provided a surface examination of the J-groove weld is also performed.

By letter dated March 3, 2008, Tennessee Valley Authority (the licensee) requested relaxation to implement an alternative to the requirements of Section IV.C.(5)(b) of the Order for RPV head penetration nozzles at WBN, Unit 1.

2.0 FIRST REVISED NRC ORDER EA-03-009 RELAXATION REQUEST FOR EXAMINATION COVERAGE FOR REACTOR PRESSURE VESSEL HEAD PENETRATION NOZZLES 2.1 Order Requirements for Which Relaxation is Requested Section IV.C of the Order requires, in part, that inspections of Section IV.C.(5)(b) of the Order be performed by February 11, 2008, for low susceptibility plants similar to WBN, Unit 1. By letter dated January 27, 2006, the NRC staff approved an alternative inspection schedule to meet the Order for Watts Bar Unit 1. Specifically, the nonvisual NDE in accordance with the requirements of Paragraph IV.C.(5)(b) of the Order are to be completed prior to restarting the facility from the Cycle 8 refueling outage (current outage).

The licensee has requested relaxation from Section IV.C.(5)(b) of the Order EA-03-009. The specific relaxation requested is identified below.

2.2 Licensees Proposed Alternative The licensee seeks relaxation from the Order to revise the minimum volumetric inspection coverage requirement below the J-groove weld for penetration nozzle number 74 at WBN, Unit 1, to the lowest elevation that can be practically inspected to a minimum of 0.91-inch below the J-groove weld. During the current refueling outage for WBN, Unit 1, the licensee performed volumetric examinations to the maximum extent practical to meet all requirements of the Order.

The inspection distance below the J-groove weld for penetration nozzle number 74 did not meet the full requirements of the Order. The specific coverage obtained was 0.91-inch below the J-groove weld.

2.3 Licensees Basis for Proposed Alternative The licensees proposed alternative is to perform the volumetric examination required by the Order to the lowest elevation that can be practically inspected for penetration nozzle number 74.

The licensee will utilize inspection option (b)(i) and will achieve volumetric and surface coverage 2 inches above the J-groove weld down to the lowest elevation that can be practically inspected with a minimum distance below the J-groove weld for penetration nozzle number 74 of 0.91-inch.

The licensee states that the bottom of each RPV upper head penetration nozzle includes a threaded guide cone attached to the bottom of the penetration nozzle via a threaded connection and tack welds. This design creates a physical restraint to full effective coverage of the Order required volumetric inspection area with ultrasonic examination probes.

The licensee notes that while the Order allows provisions for dye penetrant inspection, it would require extensive work under and around the RPV upper head. The licensee estimates the general area radiation level under the WBN, Unit 1, RPV upper head at 3 R/hr. In addition, the threaded region of the penetration nozzles would make a dye penetrant inspection impractical.

Therefore, the licensee concludes, that additional manual inspection of the uninspected regions of each penetration nozzle for which full Order coverage could not be met would result in significant radiation exposure to personnel without a compensating increase in the level or quality or safety.

The licensee further states that testing of portions of the nozzle significantly below the J-groove weld is not significant to the phenomena of concern. The phenomena that are of concern are leakage through the J-groove weld and circumferential cracking in the nozzle above the J-groove weld. The nozzle is essentially an open-ended tube, and the nozzle wall below the J-groove weld is not part of the reactor coolant system pressure boundary. The licensee believes the proposed inspection coverage does not preclude full UT examination coverage of the portions of these nozzles that are of primary interest.

The licensee, in their March 3, 2008 submittal, provided a stress analysis of the WBN, Unit 1, RPV upper head penetration nozzles. For the downhill side of penetration nozzle number 74, at a distance of 0.91-inch to 1-inch below the J-groove weld, the hoop stress is below 0 ksi. This hoop stress demonstrates that the area of missed inspection coverage is in compression in the axial plane, and axial flaws would not initiate or grow through this area. As such, the pressure boundary formed by the J-groove weld would not be challenged by the licensees proposed alternative for the life of the plant.

These results demonstrate that the extent of the proposed inspection coverage would provide reasonable assurance of the structural integrity of WBN, Unit 1, RPV head penetration nozzles and the J-groove welds.

3.0 STAFF EVALUATION The NRC staffs review of this request was based on criterion (2) of Section IV.F of the Order, which states:

Compliance with this Order for specific nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Full inspection coverage is not achievable at WBN, Unit 1, for all RPV upper head penetration nozzles, because of nozzle end geometry. Specifically, the bottom end of nozzle number 74 is externally threaded with a funnel attached with welds. Thus, the geometry of the nozzle end makes inspection in accordance with the Order difficult and would involve a hardship including increased personnel radiation dose due to possible surface examination options. This evaluation focuses on the issue of whether there is a compensating increase in the level of quality and safety such that these nozzles should be inspected in accordance with the Order despite this hardship.

The alternative inspection proposed by the licensee for penetration nozzle number 74 is to volumetrically examine the nozzle from two inches above the weld down to the maximum extent practical with a minimum required inspection distance below the J-groove weld of 0.91-inch.

Previous inspections at WBN, Unit 1, including bare metal visual inspection above the RPV head and the current nonvisual NDE below the RPV upper head, indicate no evidence of head material wastage, leaking penetrations or reportable indications in the penetration nozzles.

The NRC staff reviewed evaluations and analyses performed by the licensee in support of this request, as described below.

Based on the finite element analysis, provided by the licensee in their March 3, 2008, submittal, as shown in Calculation Number C-3217-00-01, most residual stresses decrease significantly at short distances, less than one-half inch, below the J-groove weld. For penetration nozzle number 74 the hoop stress level at the unexamined area is below zero, and the area is in compression along the axial plane. While the accuracy of residual stress modeling has its limitations, operating experience indicates that locations with this low of a calculated residual stress level are not susceptible to primary water stress corrosion cracking. In addition, if examination of the high stress locations of these nozzles (i.e., nozzle locations adjacent to the J-groove weld and associated heat affected zone areas) finds no cracks, then cracking at the low stress locations of the same nozzles is unlikely.

As the licensee concluded that the area of missed coverage is in compression such that no axial flaw would initiate or grow through this area, the staff reviewed the licensees stress analysis.

The staffs assessment of the licensees conclusion is based on review of the licensees supporting data of the stress analysis for various nozzle angles, the conservative analysis performed to support Materials Reliability Program Report, MRP-95R1, Generic Evaluation of Examination Coverage Requirements for Reactor Pressure Vessel Head Penetration Nozzles, Revision 1, dated September 2004 [ADAMS Accession Number ML043200602].

WBN, Unit 1, is in the low-susceptibility category. Nonvisual NDE will be performed every four (4) refueling outages or seven (7) calendar years, whichever is less. The NRC staff finds this inspection frequency, with the licensees stress analysis conclusions above, provides a reasonable basis for the licensees proposed alternative inspection.

The results of the NRC staff review support the licensees stress analysis and conclusions.

Therefore, NRC staff concurs with the licensees conclusion, and the NRC staff finds that there is reasonable assurance of the structural integrity of penetration nozzle number 74 for the time interval between required inspections under the Order.

The safety issues that are addressed by the Order are degradation (corrosion) of the low-alloy steel RPV upper head, reactor coolant pressure boundary integrity and ejection of the RPV upper head penetration nozzle due to circumferential cracking of the nozzle above the J-groove weld. The licensees proposed alternative inspection, to perform the UT examination below the J-groove weld for penetration nozzle number 74 to the maximum extent practical with a minimum inspection distance below the J-groove weld of 0.91-inch, provides reasonable assurance that these safety issues are addressed at WBN, Unit 1. The licensee has noted that while surface examination could be performed to increase the inspection coverage for the nozzle, these additional inspections would be of limited value and require extensive work in very high radiation fields. The staff finds that performing these additional surface examinations would result in hardship through significant radiation exposure without a compensating increase in the level of quality or safety.

Based upon the information above, the staff finds that the licensees proposed alternative examination is acceptable as it provides reasonable assurance of the structural integrity of the RPV upper head, associated penetration nozzles and J-groove welds. Further inspections to meet the volumetric inspection requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, the licensee has demonstrated good cause for relaxation from the requirements of the Order.

4.0 CONCLUSION

The staff concludes that the licensees proposed alternative inspection, to perform the ultrasonic testing of penetration nozzle number 74 at WBN, Unit 1, to the maximum extent practical below the J-groove weld, with a minimum inspection distance of 0.91-inch, provides reasonable assurance of the structural integrity of the RPV upper head, associated penetration nozzle and J-groove weld. Further inspections of this penetration nozzle in accordance with Section IV.C.(5)(b) of the Order would result in hardship without a compensating increase in the level of quality and safety. Therefore, the licensee has demonstrated good cause for relaxation, and pursuant to Section IV.F of the Order the staff authorizes the proposed alternative inspection as stated above at WBN, Unit 1, until the Order is replaced or rescinded.

Principal Contributor: Jay W. Collins Date: March 12, 2008

Page 1 of 2 William R. Campbell, Jr.

Tennessee Valley Authority Mr. Larry E. Nicholson, General Manager cc: Performance Improvement Mr. Gordon P. Arent Tennessee Valley Authority New Generation Licensing Manager 3R Lookout Place Tennessee Valley Authority 1101 Market Street 5A Lookout Place Chattanooga, TN 37402-2801 1101 Market Street Chattanooga, TN 37402-2801 Mr. Michael A. Purcell Senior Licensing Manager Mr. Ashok S. Bhatnagar Nuclear Power Group Senior Vice President Tennessee Valley Authority Nuclear Generation Development 4X Blue Ridge and Construction 1101 Market Street Tennessee Valley Authority Chattanooga, TN 37402-2801 6A Lookout Place 1101 Market Street Ms. Beth A. Wetzel, Manager Chattanooga, TN 37402-2801 Corporate Nuclear Licensing and Industry Affairs Mr. James R. Douet Tennessee Valley Authority Vice President 4X Blue Ridge Nuclear Support 1101 Market Street Tennessee Valley Authority Chattanooga, TN 37402-2801 3R Lookout Place 1101 Market Street Mr. Masoud Bajestani, Vice President Chattanooga, TN 37402-2801 Watts Bar Unit 2 Watts Bar Nuclear Plant Mr. H. Rick Rogers Tennessee Valley Authority Vice President P.O. Box 2000 Nuclear Engineering & Technical Services Spring City, TN 37381 Tennessee Valley Authority 3R Lookout Place Mr. Michael K. Brandon, Manager 1101 Market Street Licensing and Industry Affairs Chattanooga, TN 37402-2801 Watts Bar Nuclear Plant Tennessee Valley Authority General Counsel P.O. Box 2000 Tennessee Valley Authority Spring City, TN 37381 6A West Tower 400 West Summit Hill Drive Mr. Michael J. Lorek, Plant Manager Knoxville, TN 37902 Watts Bar Nuclear Plant Tennessee Valley Authority Mr. John C. Fornicola, Manager P.O. Box 2000 Nuclear Assurance Spring City, TN 37381 Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Senior Resident Inspector

Page 2 of 2 Watts Bar Nuclear Plant U.S. Nuclear Regulatory Commission 1260 Nuclear Plant Road Spring City, TN 37381 County Executive 375 Church Street Suite 215 Dayton, TN 37321 County Mayor P. O. Box 156 Decatur, TN 37322 Mr. Lawrence E. Nanney, Director Division of Radiological Health Dept. of Environment & Conservation Third Floor, L and C Annex 401 Church Street Nashville, TN 37243-1532