ML080250142

Request for Relaxation from First Revised Nuclear Regulatory Commission Order EA-03-009

ML080250142
Person / Time
Site:	South Texas
Issue date:	02/06/2008
From:	Hiltz T NRC/NRR/ADRO/DORL/LPLIV
To:	Sheppard J South Texas
Thadani, M C, NRR/DORL/LP4, 415-1476
References
EA-03-009, TAC MD7322, TAC MD7323
Download: ML080250142 (17)

Text

February 6, 2008 Mr. James J. Sheppard President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - REQUEST FOR RELAXATION FROM FIRST REVISED NRC ORDER EA-03-009 (TAC NOS. MD7322 AND MD7323)

Dear Mr. Sheppard:

By letter dated November 7, 2007, STP Nuclear Operating Company (STPNOC, the licensee),

requested relaxation from certain requirements of the First Revised Nuclear Regulatory Commission Order (NRC Order) EA-03-009, issued on February 20, 2004, establishing interim inspection requirements for reactor pressure vessel (RPV) heads at pressurized-water reactors.

For South Texas Project (STP), Unit 1 and similar plants determined to have a low susceptibility to primary water stress-corrosion cracking (PWSCC) in accordance with Sections IV.A, IV.B, and IV.C.(3) of the NRC Order, the inspection is required to be performed by February 11, 2008, in accordance with Section IV.C.(5)(b) of the NRC Order. For STP, Unit 2 and similar plants determined to have a moderate susceptibility to PWSCC in accordance with Sections IV.A, IV.B, and IV.C.(3) of the NRC Order, the inspection is required to be performed every refueling outage, in accordance with Section IV.C.(5)(b) of the NRC Order.

The licensee stated that full compliance with the NRC Order for certain reactor vessel head nozzles poses a hardship or unusual difficulty without a compensating increase in the level of quality and safety. Because full compliance is not possible, the licensee requests relaxation of certain nondestructive examination requirements described in the NRC Order and proposes an alternative to change the required ultrasonic (UT) examination range to the following: from 2 inches above the J-groove weld down to the lowest elevation that can be practically inspected on each nozzle with the UT probe.

The NRC staff has reviewed the licensees request. Based on the information provided by the licensee, the NRC staff finds that the licensees proposed alternative examination is acceptable, as it provides a reasonable assurance of structural integrity of the RPV head, control rod drive mechanism penetrations, and welds. Further, the inspections to comply with the NRC Order requirements for certain nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Therefore, the NRC staff concludes that the licensee has demonstrated good cause for relaxation, and pursuant to Section IV.F of the NRC Order EA-03-009 dated February 20, 2004, the NRC staff authorizes the proposed alternative inspection at STP, Units 1 and 2 for the second inspection interval or until the NRC Order EA-03-009 is replaced or rescinded,

J. Sheppard whichever occurs first. The NRC staffs authorization is subject to the condition, agreed to by the licensee in its November 7, 2007, letter to the NRC, and described as follows:

STPNOC understands that, should the NRC staff find that the crack-growth formula in industry report MRP [Materials Reliability Program]-55 is unacceptable, the analysis justifying relaxation of the NRC Order will be revised within 30 days after STPNOC is notified of an NRC-approved crack-growth formula.

• If the results from the revised analysis exceed the crack-growth acceptance criteria prior to the end of the current operating cycle, this relaxation request will be rescinded and STPNOC will, within 72 hours3 days <br />0.429 weeks <br />0.0986 months <br />, submit to the NRC written justification for continued operation.

• If the revised analysis shows that the crack-growth acceptance criteria are exceeded, during the subsequent operating cycle, STPNOC will, within 30 days, submit the revised analysis for NRC review.

• If the revised analysis shows that the crack-growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, STPNOC will submit a letter to the NRC within 30 days confirming that the analysis has been revised.

This request for relaxation applies to the duration of the second inspection interval or until the NRC Order EA-03-009 is replaced or rescinded, whichever occurs first. However, it is only needed until the RPV heads of STP, Units 1 and 2 are replaced. The Unit 1 head is to be replaced during the refueling outage scheduled for October 2009 and the Unit 2 head will be replaced during the refueling outage scheduled for March 2010.

The NRC staffs safety evaluation is enclosed.

Sincerely,

/RA/

Thomas G. Hiltz, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

Safety Evaluation cc w/encl: See next page

ML080250142 *SE input OFFICE NRR/LPL4/PM NRR/LPL4/LA DCI/CPNB/BC OGC, NLO w/Cmts NRR/LPL4/BC NAME MThadani JBurkhardt TChan* MSpencer THiltz DATE 2/1/08 2/1/08 1/9/08 2/4/08 2/6/08 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO RELAXATION OF REQUIREMENTS OF REVISION 1 OF NRC ORDER EA-03-009 FACILITY OPERATING LICENSE NOS. NPF-76 AND NPF-80 STP NUCLEAR OPERATING COMPANY, ET AL.

SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499

1.0 INTRODUCTION

The First Revised Nuclear Regulatory Commission Order EA-03-009 (NRC Order), issued on February 20, 2004, requires specific examinations of the reactor pressure vessel (RPV) head and vessel head penetration (VHP) nozzles of all pressurized-water reactor plants.Section IV.F of the NRC Order states that requests for relaxation of the NRC 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 Boiler and Pressure Vessel Code (ASME Code) in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3).Section IV.F of the NRC 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 Order for specific nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

For South Texas Project (STP) Unit 1 and similar plants determined to have a low susceptibility to primary water stress-corrosion cracking (PWSCC) in accordance with Sections IV.A, IV.B, and IV.C.(3) of the NRC Order, the following inspection is required to be performed by February 11, 2008, in accordance with Section IV.C.(5)(b) of the NRC Order:

(b) For each penetration, perform a non-visual NDE [nondestructive examination] in accordance with either (i), (ii) or (iii) [below]:

(i) Ultrasonic testing of the RPV head penetration nozzle volume (i.e., nozzle base material) from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 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 2 inches [see Figure IV-1]); OR from 2 inches above

the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0-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 (see Figure IV-2). 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 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 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 2 inches [see Figure IV-3]); OR from 2 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 (see Figure IV-4).

(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.

For STP Unit 2 and similar plants determined to have a moderate susceptibility to PWSCC in accordance with Sections IV.A, IV.B, and IV.C.(3) of the NRC Order, the following inspection is required to be performed every refueling outage, in accordance with Section IV.C.(5)(b) of the NRC Order:

(a) Bare metal visual examination of 100 percent of the RPV head surface (including 360º [degrees] around each RPV head penetration nozzle). For RPV heads with the surface obscured by support structure interferences which are located at RPV head elevations downslope from the outermost RPV head penetration, a

bare metal visual inspection of no less than 95 percent of the RPV head surface may be performed provided that the examination shall include those areas of the RPV head upslope and downslope of boron or corrosive product. Should any evidence of boron or corrosive product be identified, the licensee shall examine the RPV head surface under the support structure to ensure that the RPV head is not degraded.

OR (b) For each penetration, perform a nonvisual 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 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 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 2 inches [see Figure IV-1]); OR from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0-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 (see Figure IV-2). 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 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 2 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 2 inches [see Figure IV-3]); OR from 2 inches above the highest point of the root of the J-groove weld (on a horizontal plane perpendicular to the nozzle axis) to 1.0-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 (see Figure IV-4).

(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.

Option (i) is the criterion applicable to STP, Units 1 and 2.

By letter dated November 7, 2007, South Texas Project Nuclear Operating Company (STPNOC, the licensee) requested relaxation to implement an alternative to the requirements of Section IV.C.(5)(b)(i) of the NRC Order for RPV head penetration nozzles at STP, Units 1 and 2.

2.0 FIRST REVISED NRC ORDER EA-03-009 RELAXATION REQUEST FOR EXAMINATION COVERAGE FOR REACTOR PRESSURE VESSEL HEAD PENETRATION NOZZLES 2.1 NRC Order Requirements for Which Relaxation is Requested Section IV.C of the NRC Order EA-03-009 dated February 20, 2004, requires, in part, that inspections of Section IV.C.(5)(b) of the NRC Order be performed by February 11, 2008, for low-susceptibility plants similar to STP Unit 1. Additionally,Section IV.C of the NRC Order EA-03-009 dated February 20, 2004, requires, in part, that inspections of Section IV.C.(5)(b) of the NRC Order be performed every refueling outage for moderate susceptibility plants similar to STP Unit 2.

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

The specific relaxation requested is described below.

2.2 Licensees Proposed Alternative The licensee seeks relaxation from certain requirements in Section IV.C.(5)(b)(i) of the NRC Order EA-03-009. The proposed alternative is to change the required ultrasonic (UT) examination range to 2 inches above the J-groove weld down to the lowest elevation that can be practically inspected on each nozzle with the UT probe. The licensee also requests this relaxation be granted for the duration of the second inspection interval. However, the change in requirements is needed only until the RPV heads of both STP Units 1 and 2 are replaced. The STP Unit 1 head is to be replaced during the refueling outage scheduled for October 2009.

Replacement of the Unit 1 head will occur at an effective degradation years (EDY) of 7.87 years, while still having a low susceptibility. The STP Unit 2 head is to be replaced during

the refueling outage beginning in March 2010. STP Unit 2 EDY at that time is expected to be 8.66, with the head then being classified as having moderate susceptibility.

2.3 Licensees Basis for Proposed Alternative It is the licensees intent to perform the ultrasonic (UT) examination to the maximum extent possible. The licensee will utilize inspection option (b)(i) and will achieve UT coverage 2 inches above the J-groove weld down to the lowest elevation that can be practically inspected on each nozzle with the UT probe being used. Specific inspection results for each unit are discussed below.

Inspection Results (As Stated By Licensee)

Unit 1 During 1RE13, STPNOC performed a non-visual nondestructive volumetric examination of the reactor head penetration tubes in compliance with Section IV.C.(5)(b)(i) of Revision 1 of the

[NRC] Order. No reportable indications were found.

Of the 79 penetrations:

• 75 were examined from the underside of the reactor vessel head using ultrasonic test equipment maneuvered into place using a remote positioning manipulator;

• One penetration (head vent) was examined using both automated ultrasonic testing and manual eddy current testing; and

• Three penetrations were not included because they are not attached to the head with J-groove welds.

In accordance with Paragraph IV.C(5)(b)(i), the affected penetrations were scanned starting from the taper-to-cylinder transition at the bottom of each nozzle up to at least two inches above the highest point of the J-groove weld. [The Westinghouse report] WCAP-16636, Structural Integrity Evaluation of Reactor Vessel Upper Head Penetrations to Support Continued Operation: South Texas Units 1 & 2, documents an analysis which supports limiting the examination zone to 1-inch below the lowest point of each J-groove weld. UT coverage of most of the penetrations with J-groove welds addressed at least the specified zone to one inch below the lowest point of the penetration with J-groove.

There were two exceptions:

• One Control Rod Drive Mechanism penetration (#69) had examination coverage less than one inch because the penetration length only allowed examination to 0.73-inch below the weld toe.

• The de-gas penetration has an unchamfered end-piece extending to 0.67-inch below the lowest point on the J-groove weld. Because it was unchamfered, scanning coverage extended to the end of the de-gas penetration nozzle.

Consequently, relaxation for Unit 1 is only required for reactor head penetration #69.

Unit 2 During 2RE12, STPNOC performed a bare metal visual of the RPV head surface in compliance with Section IV.C.(5)(a) and a non-visual nondestructive volumetric inspection of the reactor head penetration tubes in compliance with Section IV.C.(5)(b)(i) of Revision 1 of the NRC Order.

No reportable indications were found.

Of the 79 penetrations:

• 74 were examined from the underside of the reactor vessel head using ultrasonic test equipment maneuvered into place using a remote positioning manipulator;

• Two penetrations (head vent and de-gas) were examined using both automated ultrasonic testing and manual eddy current testing; and

• Three penetrations were not included because they are not attached to the head with J-groove welds.

In accordance with Paragraph IV.C.(5)(b)(i), the affected penetrations were scanned starting from the taper-to-cylinder transition at the bottom of each nozzle up to at least two inches above the highest point of the J-groove weld. WCAP-16636 documents an analysis which supports limiting the inspection zone to 1-inch below the lowest point of each J-groove weld. UT coverage addressed at least the specified one inch of most of the penetrations with J-groove welds. The exceptions were eight Control Rod Drive Mechanism penetrations with inspection coverage less than one inch because the inside diameter chamfer on the end of each nozzle precluded coverage to the very end of the nozzle below the J-groove weld. The following penetrations had limited examination coverage below the weld toe due to their insufficient penetration length:

Table 1: Limited Examination Coverage for Unit 2 AXIAL COVERAGE BELOW LOWEST POINT PENETRATION FUNCTION OF J-GROOVE WELD (inches) 65 [CRDM] Spare 0.74 66 [CRDM] 0.63 68 [CRDM] 0.71 69 [CRDM] 0.89 70 [CRDM] 0.81 71 [CRDM] 0.78 72 [CRDM] 0.76 73 [CRDM] 0.63

The head and de-gas lines were examined with both ultrasonic testing (UT) and eddy current testing (ET) to satisfy the requirements of the [NRC] Order. These penetrations were scanned starting from the taper-to-cylinder transition at the bottom of the weld to at least two inches above the highest point of the J-groove weld. The vent and de-gas lines are flush with the inside contour of the head and the chamfer on the corner of these penetrations prevents full coverage to the very end of the nozzle. Consequently, the configuration of the weld at the base of these lines is not suitable for inspection by UT. The J-groove weld surface for these penetrations was examined using ET. No recordable indications were found using either method.

WCAP-16636 Relaxation of the examination requirements is consistent with the analysis submitted in industry topical report MRP-55, Materials Reliability Program (MRP) Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Materials, Revision 1, and the site-specific analysis in WCAP-16636-P, Revision 0.

Five rows of penetration nozzles were analyzed for WCAP-16636. The magnitude of the hoop stress at a distance of one inch or more below the toe of the downhill side of the J-groove weld is less than 20 ksi for the analyzed penetrations. The required inspection coverage for those penetration nozzles not being analyzed can be determined using the bounding results from those analyzed penetrations with bounding nozzle angles. The inspection requirements of the

[NRC] Order are satisfied provided that minimum inspection coverage of one inch is achieved.

The major inherent conservatisms in WCAP-16636-P, Revision 0, are summarized below:

• Conservatism in Assumed Crack Geometry:

High stresses, on the order of the material yield strength, are necessary to initiate PWSCC. There are no known cases of PWSCC of Alloy 600 occurring below the yield stress. The yield strength for wrought Alloy 600 head penetration nozzles is in the range of 37 ksi to 65 ksi. Weld metal yield strengths are generally higher.

The yield strengths of the head penetration nozzles for South Texas Project Unit 1 and Unit 2 vary from 35.5 ksi to 55 ksi. At a stress level less than 20 ksi, PWSCC initiation is extremely unlikely. The assumption of a through-wall flaw in these unlikely PWSCC initiation regions of the head penetration is an important additional conservatism because the penetration tubes will be inspected with maximum achievable coverage on the tube ID [inside diameter].

The axial blade probe is used in the thermally sleeved penetrations between the penetration ID and the thermal sleeve OD [outside diameter]. The axial blade probe propagates ultrasound circumferentially rather than axially and as such does not require additional axial length to support the ultrasonic wave propagation. Thus, data can be collected very close to the penetration end.

• Conservatisms in Flaw Propagation Calculations:

STPNOC has calculated the susceptibility of the Unit 1 and Unit 2 RPV heads to PWSCC, as represented by effective degradation years (EDY) at the end of each operating cycle. Unit 1 EDY is projected to be 7.37 by Spring 2008 (refueling outage 1RE14) and 7.87 in Fall 2009 (1RE15). Unit 2 EDY is projected to be 8.16 in Fall 2008 (2RE13) and 8.66 in Spring 2010 (2RE14). Examination criteria consistent with the Moderate category are applicable to Unit 2 when EDY is 8 or higher until the head is replaced.

Crack growth evaluation for partial through-wall flaws is based on the worst-case stress distribution through the penetration wall in the immediate vicinity of the penetration welds. A series of crack growth calculations presume a flaw where the lower extremity of this initial through-wall flaw is conservatively postulated to be located on the penetration nozzle where either the inside or outside surface hoop stress decreases below 0 KSI.

The methodology and the technical basis of the crack growth calculation, which is based on the hoop stress distribution and the PWSCC crack growth rate recommended in MRP-55 Revision 1, are provided in WCAP-16636-P.

The calculation demonstrates that a flaw in an unexamined area of the penetration nozzle would require more than one operating cycle to elapse before propagating into the pressure boundary formed by the J-groove weld. The operating cycles for Unit 1 and Unit 2 are approximately 18 months, or 1.5 Effective Full Power Years (EFPY). The minimum time for a flaw to propagate from 0.63 inches (minimum length examined) below the weld to the bottom of the J-groove weld is greater than 6 EFPY (approximately 4 operating cycles); this exceeds the projected operating time until the reactor vessel heads are projected to be replaced. Therefore, the extent of the available inspection coverage provides reasonable assurance of the structural integrity of the RPV head penetrations.

STPNOC understands that, should the NRC staff find that the crack-growth formula in industry report MRP-55 is unacceptable, the analysis justifying relaxation of the NRC Order will be revised within 30 days after STPNOC is notified of an NRC-approved crack-growth formula.

• If the results from the revised analysis exceed the crack-growth acceptance criteria prior to the end of the current operating cycle, this relaxation request will be rescinded and STPNOC will, within 72 hours3 days <br />0.429 weeks <br />0.0986 months <br />, submit to the NRC written justification for continued operation.

• If the revised analysis shows that the crack-growth acceptance criteria are exceeded, during the subsequent operating cycle, STPNOC will, within 30 days, submit the revised analysis for NRC review;

• If the revised analysis shows that the crack-growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating

cycle, STPNOC will submit a letter to the NRC within 30 days confirming that the analysis has been revised.

The licensee states that the proposed inspection coverage is adequate because the cited inspection limitation for the nozzles does not preclude full UT examination coverage of the portions of the nozzles that are of primary interest. That is because:

• UT of the most highly stressed portion of the nozzle (the weld heat-affected zone) is unaffected by this limitation.

• UT of the interference fit zone above the weld (for leakage assessment) is unaffected by this limitation, and cracks initiating in the unexamined bottom portion (non-pressure boundary) of the nozzle would be of minimal safety significance with respect to pressure boundary leakage or nozzle ejection, since this portion of the nozzle is below the pressure boundary. Any cracks would have to grow through a significant examined portion of the tube to reach the pressure boundary.

The licensee goes on to state that zones of inspection selected are such that the stresses in the un-inspected zones are at levels for which PWSCC is considered highly unlikely. Operating experience also indicates that locations with low-stress levels are much less susceptible to PWSCC. 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 is unlikely.

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

Compliance with this NRC Order for certain 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 STP, Units 1 and 2 for all RPV head penetrations, because of nozzle-end geometry. Specifically, STPNOC is not able to completely comply with the requirements of Section IV.C.(5)(b)(i) of the NRC Order for UT inspection of the RPV head penetration nozzles below the J-groove weld due to the physical configuration of the nozzles and the limitations of the test equipment.

Though the NRC Order allows for eddy current testing or dye penetrant examination (Section IV.C.(5)(b)(ii)) to be used as an alternative to UT, neither is a suitable substitute for this application on tubes with coverage less than 1.0-inch below the J-groove weld because:

• The bottom of each nozzle terminates in a chamfered surface below the downhill side of the J-groove weld.

• Eddy current probes do not maintain adequate contact with the nozzle at its lower end due to this nozzle geometry and so cannot perform a complete examination.

• Dye penetrant testing requires extensive work under and around the RPV head where radiation levels are anticipated to be between 4000 and 9000 millirems per hour.

• Performing dye penetrant testing on the bottom nozzle area would result in significant radiation exposure to personnel without a compensating increase in the level of quality or safety.

The alternative proposed by the licensee is for the relaxation of the requirements specified in the NRC Order under Section IV.C. (5)(b)(i) for examination of STP Unit 1 and Unit 2 RPV head penetrations such that the required UT examination range is changed to the following: from 2 inches above the J-groove weld down to the lowest elevation that can be practically inspected on each nozzle with the UT probe. The NRC staff reviewed the evaluations and analyses performed by the licensee in support of this request, as described below.

STPNOC has calculated the susceptibility of the STP Unit 1 and Unit 2 RPV heads to PWSCC, as represented by EDY at the end of each operating cycle. Unit 1 EDY is projected to be 7.37 by spring 2008 (refueling outage 1RE14) and 7.87 in fall 2009 (1RE15). Unit 2 EDY is projected to be 8.16 in fall 2008 (2RE13) and 8.66 in spring 2010 (2RE14). Examination criteria consistent with the Moderate category are applicable to Unit 2 when EDY is 8 or higher until the head is replaced.

The licensees crack-growth evaluation for partial through-wall flaws is based on the worst-case stress distribution through the penetration wall in the immediate vicinity of the penetration welds.

The crack-growth calculations presume a flaw where the lower extremity of this initial through-wall flaw is conservatively postulated to be located on the penetration nozzle where either the inside or outside surface hoop stress decreases below 0 ksi.

The methodology and the technical basis of the crack-growth calculation, is based on the hoop-stress distribution and the PWSCC crack growth rate recommended in MRP-55, Revision 1, are provided in WCAP-16636-P, Revision 0 Structural Integrity Evaluation of Reactor Vessel Upper Head Penetration to Support Continued Operation: South Texas Units 1

& 2.

The licensee states that the proposed inspection coverage is adequate because the cited inspection limitation for the nozzles does not preclude full UT examination coverage of the portions of the nozzles that are of primary interest. That is because:

• UT of the most highly stressed portion of the nozzle (the weld heat-affected zone) is unaffected by this limitation.

• UT of the interference fit zone above the weld (for leakage assessment) is unaffected by this limitation, and cracks initiating in the unexamined bottom portion (non-pressure boundary) of the nozzle would be of minimal safety

significance with respect to pressure boundary leakage or nozzle ejection, since this portion of the nozzle is below the pressure boundary. Any cracks would have to grow through a significant examined portion of the tube to reach the pressure boundary.

The licensee goes on to state that zones of inspection selected are such that the stresses in the un-inspected zones are at levels for which PWSCC is considered highly unlikely. Operating experience also indicates that locations with low-stress levels are much less susceptible to PWSCC. The NRC staff agrees that 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 is unlikely.

The licensees calculation demonstrates that a flaw in an unexamined area of the penetration nozzle would require more than one operating cycle to elapse before propagating into the pressure boundary formed by the J-groove weld. The operating cycles for Unit 1 and Unit 2 are approximately 18 months, or 1.5 EFPY. The minimum time for a flaw to propagate from 0.63 inches (minimum length examined) below the weld to the bottom of the J-groove weld is greater than 6 EFPY (approximately four operating cycles); this exceeds the projected operating time until the reactor vessel heads are replaced. Therefore, the NRC staff concludes that the extent of the available inspection coverage provides reasonable assurance of the structural integrity of the RPV head penetrations until the reactor vessel heads are replaced.

The licensees analysis incorporates a crack-growth formula as provided in the EPRI Report, Material Reliability Program (MRP) Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of This Wall Alloy 600 Material (MRP-55), Revision 1. The NRC staff has completed a preliminary review of the crack-growth formula, but has not yet made a final assessment regarding the acceptability of the report. Therefore, a condition has been included regarding the approval of the proposed relaxations. The condition was agreed to by the licensee in its November 7, 2007, letter to the NRC and is as follows:

STPNOC understands that, should the NRC staff find that the crack-growth formula in industry report MRP-55 is unacceptable, the analysis justifying relaxation of the NRC Order will be revised within 30 days after STPNOC is notified of an NRC-approved crack-growth formula.

• If the results from the revised analysis exceed the crack-growth acceptance criteria prior to the end of the current operating cycle, this relaxation request will be rescinded and STPNOC will, within 72 hours3 days <br />0.429 weeks <br />0.0986 months <br />, submit to the NRC written justification for continued operation.

• If the revised analysis shows that the crack-growth acceptance criteria are exceeded, during the subsequent operating cycle, STPNOC will, within 30 days, submit the revised analysis for NRC review.

• If the revised analysis shows that the crack-growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, STPNOC will submit a letter to the NRC within 30 days confirming that the analysis has been revised.

The safety issues that are addressed by the NRC Order EA-03-009 are degradation (corrosion) of the low-alloy steel RPV head, reactor coolant pressure boundary integrity and ejection of the VHP 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 to the maximum extent possible with a minimum inspection distance below the J-groove weld (0.73 inches for penetration #69 for Unit 1 and as defined by Table 1 for Unit 2) provides reasonable assurance that these safety issues are addressed. The licensee has noted that dye-penetrant testing could be performed to increase the inspection coverage for each nozzle.

However, these additional inspections would require extensive work in very high radiation fields.

The NRC staff finds that performing these additional surface examinations would result in hardship through significant radiation exposure without a compensating increase in the level or quality or safety. Additionally, the NRC staff finds that the licensees proposed alternative examination provides reasonable assurance of the structural integrity of the RPV head, CRDM penetrations and welds. Further, the NRC staff finds that further inspections to comply with the NRC Order requirements for certain nozzles would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. This request for relaxation applies to the duration of the second inspection interval or until the NRC Order EA-03-009 is replaced or rescinded, whichever occurs first. However, it is only needed until the RPV heads of both Unit 1 and Unit 2 are replaced. The Unit 1 head will be replaced during the refueling outage scheduled for October 2009 and the Unit 2 head will be replaced during the refueling outage scheduled for March 2010.

4.0 CONCLUSION

The NRC staff concludes that the licensees proposed alternative inspection of STP Units 1 and 2 CRDM penetrations, to perform the UT examination below the J-groove weld to the maximum extent possible with a minimum inspection distance below the J-groove weld defined as 0.73 inches for penetration #69 for Unit 1, and as defined in Table 1 for Unit 2, provides reasonable assurance of the structural integrity of the RPV head, CRDM penetrations and welds. Further, the inspections of these CRDM penetrations in accordance with Section IV.C.(5)(b) of the 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 licensee has demonstrated good cause for relaxation.

Accordingly, pursuant to Section IV.F of the NRC Order EA-03-009 dated February 20, 2004, the licensees request for relaxation is authorized for the duration of the second inspection interval or until the NRC Order EA-03-009 is replaced or rescinded, whichever occurs first. The NRC staffs authorization is subject to the following condition agreed to by the licensee in its November 7, 2007, letter to the NRC and is as follows.

STPNOC understands that, should the NRC staff find that the crack-growth formula in industry report MRP-55 is unacceptable, the analysis justifying relaxation of the NRC Order will be revised within 30 days after STPNOC is notified of an NRC-approved crack-growth formula.

• If the results from the revised analysis exceed the crack-growth acceptance criteria prior to the end of the current operating cycle, this

relaxation request will be rescinded and STPNOC will, within 72 hours3 days <br />0.429 weeks <br />0.0986 months <br />, submit to the NRC written justification for continued operation.

• If the revised analysis shows that the crack-growth acceptance criteria are exceeded, during the subsequent operating cycle, STPNOC will, within 30 days, submit the revised analysis for NRC review.

• If the revised analysis shows that the crack-growth acceptance criteria are not exceeded during either the current operating cycle or the subsequent operating cycle, STPNOC will submit a letter to the NRC within 30 days confirming that the analysis has been revised.

The relaxation is effective only until the RPV heads of both Unit 1 and Unit 2 are replaced. The Unit 1 head will be replaced during the refueling outage scheduled for October 2009 and the Unit 2 head will be replaced during the refueling outage scheduled for March 2010.

Principal Contributor: C. Nove Date: February 6, 2008

South Texas Project, Units 1 and 2 12/5/2007 cc:

Senior Resident Inspector Ms. Marilyn Kistler U.S. Nuclear Regulatory Commission Senior Staff Specialist, Licensing P.O. Box 289 STP Nuclear Operating Company Wadsworth, TX 77483 P.O. Box 289, Mail Code 5014 Wadsworth, TX 77483 C. M. Canady City of Austin, Electric Utility Department Environmental and Natural Resources 721 Barton Springs Road Policy Director Austin, TX 78704 P.O. Box 12428 Austin, TX 78711-3189 J. J. Nesrsta/R. K. Temple E. Alercon/Kevin Pollo Mr. Jon C. Wood CPS Energy Cox, Smith, & Matthews P.O. Box 1771 112 East Pecan, Suite 1800 San Antonio, TX 78296 San Antonio, TX 78205 INPO, Records Center Director, Division of Compliance & Inspection 700 Galleria Parkway Bureau of Radiation Control Atlanta, GA 30339-3064 Texas Department of State Health Services 1100 West 49th Street Regional Administrator, Region IV Austin, TX 78756 U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Mr. Ted Enos Arlington, TX 76011 4200 South Hulen Suite 422 Steve Winn/Christie Jacobs Ft. Worth, TX 76109 Eddy Daniels/Marty Ryan NRC Energy, Inc. Mr. Brian Almon 211 Carnegie Center Public Utility Commission of Texas Princeton, NJ 08540 P.O. Box 13326 Austin, TX 78711-3326 Mr. Nate McDonald County Judge for Matagorda County Ms. Susan M. Jablonski 1700 7th Street, Room 301 Office of Permitting, Remediation Bay City, TX 77414 and Registration Texas Commission on Environmental Quality A. H. Gutterman, Esq. MC-122 Morgan, Lewis & Bockius P.O. Box 13087 1111 Pennsylvania Avenue, NW Austin, TX 78711-3087 Washington, DC 20004 Mr. Ken Coates, Plant General Manager E. D. Halpin, Site Vice President STP Nuclear Operating Company STP Nuclear Operating Company South Texas Project Electric Generating Station South Texas Project Electric Generating Station P.O. Box 289 P.O. Box 289 Wadsworth, TX 77483 Wadsworth, TX 77483 Mr. Anthony P. Jones, Chief Boiler Inspector S. M. Head, Manager, Licensing Texas Department of Licensing and Regulation STP Nuclear Operating Company Boiler Division P.O. Box 289, Mail Code: N5014 E.O. Thompson State Office Building Wadsworth, TX 77483 P.O. Box 12157 Austin, TX 78711 C. T. Bowman, General Manager, Oversight STP Nuclear Operating Company P.O Box 289 Wadsworth, TX 77483