WO 16-0052, Relief Request Number I4R-03, Request for Relief from Paragraph-3200(b) of ASME Code Case N-729-1 for Reactor Vessel Head Penetration Nozzle Welds and Relief Request I4R-04, Request for Relief from the Requirements of ASME Code Case N-729

Relief Request Number I4R-03, Request for Relief from Paragraph-3200(b) of ASME Code Case N-729-1 for Reactor Vessel Head Penetration Nozzle Welds and Relief Request I4R-04, Request for Relief from the Requirements of ASME Code Case N-729-1

ML16293A582
Person / Time
Site:	Wolf Creek
Issue date:	10/11/2016
From:	Reasoner C Wolf Creek
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
WO 16-0052
Download: ML16293A582 (20)

Text

...

W8LFCREEK -,NUCLEAR OPERATING CORPORATION Cleveland Reasoner Site Vice President October 11, 2016 WO 16-0052 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Reference:

Letter from J. H. McCoy to USNRC dated February 23, 2016, Wolf Creek Generating Station lnservice Inspection Plan and 10 CFR 50.55a Requests 14R-01 and 14R-02 for the Fourth lnservice Inspection Program Interval.

Subject:

Docket No. 50-482: Relief Request Number 14R-03, Request for Relief from Paragraph-3200(b) of ASME Code Case N-729-1 for Reactor Vessel head Penetration Nozzle Welds and Relief Request 14R-04, Request for Relief from the Requirements of ASME Code Case N-729-1 Gentlemen:

During the current twenty-first refueling outage the reactor vessel head penetration nozzles were examined in accordance with Code Case N-729-1 and both Wolf Creek Generating Station (WCGS) lnservice Inspection (ISi) and Boric Acid Programs. A canopy seal weld leak led to the shutdown of the plant. The resulting boric acid accumulation from the canopy seal weld leak covered a portion of the head which is the subject of the head inspection. The boric acid accumulation prevents adequate visual inspection of 12 nozzles because the canopy seal weld related boron would mask any boron from a nozzle leak. Wolf Creek Nuclear Operating Corporation (WCNOC) is confident that the observed deposits were the result of the canopy seal weld leak. Several head to nozzle interface areas were obscured such that adequate visual inspections are not possible on the top side of the head. Because of this, WC NOC will be performing a supplemental examination of the obscured nozzles from the underside of the head in accordance with Code Case N-729-1. However, WCNOC is requesting relief from the requirement to perform a surface examination of the partial penetration welds because the alternate methods proposed in the attached 14R-03 relief request provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1 ).

Therefore, pursuant to 10 CFR 50.55a(z)(1 ), WC NOC hereby requests NRC approval of the attached relief request for the WCGS, lnservice Inspection (ISi) Program, fourth ten-year interval. The attachment identifies the affected components, applicable American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME) Code requirements, reason for request, proposed alternative, and basis for proposed alternative. The alternatives are proposed to be applied during Interval 4, which began September 3, 2015 and ends September 2, 2025.

P.O. Box 411 / Burlington, KS 66839 I Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HC/VET

'* u WO 16-0052 Page 2 of 2 The provisions of this relief are applicable to the fourth ten-year ISi interval for WCGS, which commenced on September 3, 2015 and will end on September 2, 2025 (Reference 1). WCNOC requests approval of this request by October 14, 2016, to support restart from the current refueling outage.

In addition, pursuant to 10 CFR 50.55a(z)(2), Wolf Creek Nuclear Operating Corporation (WCNOC) hereby requests Nuclear Regulatory Commission (NRC) approval of 10 CFR 50.55a Request Number 14R-04 for the Fourth Ten-Year Interval of WCNOC's lnservice Inspection (ISi)

Program. The attached 10 CFR 50.55a Request (14R-04) requests relief from certain ASME Code Case N-729-1 requirements for examination of reactor vessel head penetration welds.

(Attachment 2) This request is similar to that requested in the Third Ten Year Interval of WCNOC's lnservice Inspection (ISi) that was accepted by ML12353A241.

The Code of Federal Regulations 10 CFR 50.55a(g)(6)(ii)(0)(1) requires that examinations of the reactor vessel head be performed in accordance with ASME Code Case N-729-1 subject to conditions specified in paragraphs 10 CFR 50.55a(g)(6)(ii)(0)(2) through (6). The vendor chosen by WCNOC to perform these examinations is unable to meet required examination coverage below the J-groove weld on two control rod drive mechanism (CROM) penetrations.

Both of these CROM penetrations are configured such that the volumetric examination distance required by N-729-1 cannot be met. Attachment 2 to this letter, 10 CFR 50.55a Request 14R-04, documents the ultrasonic coverage limitations.

WCNOC had intended to request this relief prior to planned inspections in Refueling Outage 23 but the circumstances described above have required that the examination of one of the subject penetrations be performed at this time during Refueling Outage 21. Therefore, WCNOC requests approval of the attached 10 CFR 50.55a Request 14R-04 by October 14, 2016, to support inspection and restart from Refueling Outage 21, which is now scheduled to complete November 14, 2016.

This letter contains no commitments. If you have any questions concerning this matter, please contact me at (620) 364-4171, or Cynthia R. Hafenstine (620) 364-4204.

Cleveland Reasoner COR/rlt Attachments: 1) 10 CFR 50.55a Request Number 14R-03

2) 10 CFR 50.55a Request Number 14R-04 cc: K. M. Kennedy (NRC), w/a B. K. Singal (NRC), w/a N. H. Taylor (NRC), w/a Senior Resident Inspector (NRC), w/a to WO 16-0052 Page 1 of 5 Wolf Creek Nuclear Operating Corporation 10 CFR 50.55a Request 14R-03 Relief Requested In Accordance with 10 CFR 50.55a(z)(1)

(5 Pages) to WO 16-0052 Page 2 of 5 10 CFR 50.55a Request Number 14R-03 Relief Requested In Accordance with 10 CFR 50.55a(z)(1)

Alternative provides an acceptable level of quality and safety

• ASME Code Component(s) Affected Component: Reactor Vessel Closure Head (RVCH) Nozzles Code Class: Class 1 Examination Category: B-P Code Item Number: B4.10 (Code Case N-729-1, Alternative Examination Requirements for PWR Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division 1)

==

Description:==

Control Rod Drive Mechanism (CRDM) Nozzles Core Exit Thermocouple Nozzle Assv (CETNA) Nozzles Size: 4.00 Inch (Nominal Outside Diameter)

Material: RVCH SA533 Grade B, Class 1 Nozzle SB 167 N06600 (Alloy 600)

Alloy 82/182 weld material

2. Applicable code Edition and Addenda

• American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)Section XI, 2007 Edition through 2008 Addenda

• Code Case N-729-1 as conditioned by 10 CFR 50.55a(g)(6)(ii)(D)

3. Applicable Code Requirement

10 CFR 50.55a(g)(6)(ii)(D)(1) requires that examinations of the reactor vessel head be performed in accordance with ASME Code Case N-729-1 subject to the conditions specified in paragraphs 10 CFR 50.55a(g)(6)(ii)(D)(2) through (6).

Paragraph -3200(b) of code Case N-729-1 states:

The supplemental examination performed to satisfy-3142.2 shall include volumetric examination of the nozzle tube and surface examination of the partial-penetration weld, (emphasis added)or surface examination of the nozzle tube inside surface, the partial penetration weld, and nozzle tube outside surface below the weld, in accordance with Fig. 2, or the alternative examination area or volume shall be analyzed to be acceptable in accordance with Appendix I. The supplemental examinations shall be used to determine the extent of the unacceptable conditions and the need for corrective measures, analytical evaluation, or repair I replacement activity.

4. Reason for Request

Based on visual examination (VE), deposits resulting from leakage in the canopy seal weld on penetration 77 were found on the Reactor Vessel Head. These deposits were found in locations consistent with leakage from the canopy seal weld traveling down onto the RVCH to WO 16-0052 Page 3 of 5 and penetration nozzles. WCNOC will perform supplemental examinations of the obscured penetrations.

Twelve penetrations require supplemental examination in accordance with code requirements. Per paragraph -3200(b) of N-729-1 these supplemental examinations

" ... shall include volumetric examination of the nozzle tube and surface examination of the partial-penetration weld, ... ".

WCNOC does not have the internal resources to conduct the volumetric and surface examinations as required by Code Case N-729 3200(b). A third party vendor has been contracted to perform the examinations. The options for the surface examination of the partial penetration weld are : 1) the dye penetrant technique or 2) the eddy current technique. The dye penetrant technique carries an estimated dose of proximately 1500 mRem (1.5 REM) per nozzle, approximately 18 REM for the entire task. The vendor selected to perform the volumetric examination of the. nozzle tube has remotely operated tooling available to perform the surface examination of the partial penetration weld using the Eddy Current technique; however, there are few personnel qualified to operate this equipment. It is estimated that the surface examination of the partial penetration weld using the Eddy Current technique would result in approximately 2.5 Rem of additional exposure.

The volumetric examination of the nozzle tube will be performed with remotely operated tooling that is mounted on a manually positioned tool stand. In order to perform the supplemental volumetric examination of 12 penetrations, 13 entries under the RV closure head are required. The first entry is estimated to take approximately 10 minutes accumulating 408 mRem of exposure. The remaining entries are estimated to take approximately 2 minutes each yielding 81 mRem of exposure or 979.2 mRem for a total of 1387.2 mRem. In order to perform the surface examination of the partial penetration weld using the Eddy Current technique, an additional 13 entries under the RV closure head would be required, resulting in a projection of two times the dose accumulated for the leak path assessment and volumetric exam approach.

The vendor has estimated the time required to perform the volumetric examinations as 7 days (3 days of equipment set up, 2 days to perform examinations [12 nozzles at 6 nozzles per day], and 2 days of equipment teardown). In order to perform the surface examination of the partial penetration weld with Eddy Current, an additional 6 days would be required, as the process can only complete 2 examinations per 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> shift. (there are only enough qualified personnel to cover one shift).

5. Proposed Alternative and Basis for Use WCNOC proposes to perform a demonstrated volumetric leak path assessment (in addition to the volumetric examination) in lieu of the surface examination of the partial penetration weld. The leak path assessment can be performed in tandem with the nozzle tube volumetric exams and will not add any additional dose. This combination (volumetric examination of the nozzle tube and volumetric leak path assessment) will provide confirmation that all of the deposits observed on the RV closure head were a result of the canopy seal weld leak. WCNOC believes that the combination of the volumetric exams and the leak path assessment will provide an acceptable level of confidence in the condition of each penetration. This is because, as shown in the figure below, the two examinations will verify there are no indications in the nozzle tube and verify that there has been no leakage in the penetration tube to RVCH interface.

to WO 16-0052 Page 4 of 5 AllOV fi00,'690 nozzle I

I I

I A*****-J********A The volumetric exam is the area from points A-8-C-D. The leak path assessment will cover the interface between the nozzle and the carbon steel head above the J-groove weld within the extent of the volumetric exam. Performing the leak path assessment in lieu of the surface examination of the J-groove weld will demonstrate that the boric acid deposits observed on the exterior of the head were a result of the canopy seal weld leak.

Therefore, WCNOC believes that the estimated additional dose (2.5 - 18 REM depending on method used), the added time, and cost associated with the surface examination of the partial penetration welds will not provide any additional benefit over the proposed Leak Path Assessment and Volumetric examination.

The RVCH will be cleaned and examined so that any additional indications discovered in the future can be properly dispositioned.

Therefore performing leak path assessment in lieu of the surface examination of the partial penetration welds provides an acceptable level quality and safety.

6. Duration of Proposed Alternative The proposed alternative will be utilized during ISi Interval 4, which began September 3, 2015 and ends on September 2, 2025.

to WO 16-0052 Page 5 of 5

7. References

1. ASME Boiler and Pressure Vessel Code Case N-729-1 "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration WeldsSection XI, Division 1" to WO 16-0052 Page 1 of 13 Wolf Creek Nuclear Operating Corporation 10 CFR 50.55a Request 14R-04 Request for Relief from the Requirements of ASME Code Case N-729-1 (13 Pages) to WO 16-0052 Page 2 of 13 10 CFR 50.55a Request 14R-04 Request for Relief from the Requirements of ASME Code Case N-729-1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)

Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety

1. ASME Code Components Affected Code Class: 1

Reference:

ASME Code Case N-729-1/10 CFR 50.55a(Q)(6)(ii)(D)

Item No.: 84.20

Description:

UNS N06600 Nozzles and UNS N06082 or UNS W86182 Partial-Penetration Welds in Head.

Reactor vessel head control rod drive mechanism (CROM) penetration nozzle base material and J-groove weld that attaches the nozzle base material to the underside of the head for penetration nozzles 77 and 78.

2. Applicable Code Edition and Addenda ASME Code Section XI, 2007 Edition through 2008 Addenda, as augmented by ASME Code Case N-729-1 (Reference 1), "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration WeldsSection XI, Division 1," as amended by 10 CFR 50.55a(g)(6)(ii)(D).

3. Applicable Code Requirement 10 CFR 50.55a(g)(6)(ii)(D)(1) requires that examinations of the reactor vessel head be performed in accordance with ASME Code Case N-729-1 subject to the conditions specified in paragraphs 10 CFR 50.55a(g)(6)(ii)(D)(2) through (6).

Paragraph -2500 of Code Case N-729-1 states, in part:

If obstructions or limitations prevent examination of the volume or surface required by Figure 2 for one or more nozzles, the analysis procedure of Appendix I shall be used to demonstrate the adequacy of the examination volume or surface for each such nozzle. If Appendix I is used, the evaluation shall be submitted to the regulatory authority having jurisdiction at the plant site.

Figure 2 in ASME Code Case N-729-1, as referenced by paragraph -2500, requires that the volumetric or surface examination coverage distance below the toe of the J-groove to WO 16-0052 Page 3 of 13 weld (i.e. dimension "a") be 1.5 inches for incidence angle, 9, less than or equal to 30 degrees; 1 inch for incidence angle, 9, greater than 30 degrees; or to the end of the tube, whichever is less. These coverage requirements are applicable to Wolf Creek Generating Station (WCGS) reactor vessel head penetrations as shown in Table 1.

Table 1: WCGS Reactor Vessel Head Penetration Coverage Requirements Penetration Numbers Incidence Angle, 9 Required Coverage, "a" (degrees) (inches) 1to29 ~ 30 1.5 30 to 78 > 30 1.0

4. Reason for Request Due to physical configuration of certain reactor vessel head penetration nozzles, full examination volume required by ASME Code Case N-729-1 Table 1 cannot be achieved for reactor vessel head penetration nozzles 77 and 78, therefore, use of Mandatory Appendix I is requested in accordance with 10 CFR 50.55a(g)(6)(ii)(D)(6).

Reactor vessel head CROM penetrations at WCGS have two styles of ends, referred to as Type "X" and Type "Y" (Figure 1). Penetrations 1 through 73 are Type "Y" that are essentially a smooth wall cylinder with a radius at the outer diameter and inner diameter.

Penetrations 74 through 78 have a threaded outside diameter and an internal taper.

The design of reactor vessel head penetration nozzles 74 through 78, referred to as Type "X", (Figure 1) includes a threaded section, approximately 1.19 inch in length at the bottom of the nozzles. These penetrations are located at the 48.7 degree location. The

.dimensional configuration at this location is such that the distance from the lowest point at the toe of the J-groove weld to the top of the threaded region could be less than the required coverage dimension "a" shown in Figure 2 of ASME Code Case N-729-1.

Therefore, deviation from the required inspection coverage is sought for reactor vessel head penetrations 77 and 78, as the required coverage for these two penetrations cannot be obtained.

to WO 16-0052 Page 4 of 13 The table below lists the coverage obtained on nozzles 74-76 during the 2006/2013 exams performed per NRC Order EA-03-009 (2006) and N-729-1 (2013).

Note: The lower measurement in 2006 was performed using circumferential shooting TOFD transducers while the 2013 measurements were accomplished using axial shooting TOFD transducers. While the table below shows different coverage values it is noted in the 2013 exam report that the "Lower extent comparison using Channel 2 data shows no change from 2006 to 2013 measurements."

Penetration 9 (degrees) N-729-1 Required 2006 Inspection 2013 Inspection No. Exam Coverage Coverage Coverage (inches) Obtained Obtained (inches) (inches) 74 48.7 1.0 1.04 1.00 75 48.7 1.0 1.08 1.08 76 48.7 1.0 1.12 1.00 The physical process of welding results in slightly different weld sizes/contours being applied to each component. (This was a manual welding process, and it is not physically possible for a human to apply the exact same amount of weld metal to each component.) This is acceptable as long as the minimum design weld size or contour is met. When access is limited (as the case on the downhill side of the peripheral penetrations), this condition is magnified. This is the case in penetrations 77 and 78, as more weld metal was applied to the downhill portion of the weld, resulting in less of the penetration (below the toe of the weld and above the threads) being* available for examination.

For the initial examinations of reactor vessel head penetration welds performed in accordance with Reference 6, a similar request was previously submitted for inability to examine the required examination volume (References 3 and 4). This previous request was approved by the NRC in Reference 5. For the examinations performed in 2013 in accordance with Reference 1, as conditioned by 10 CFR 50.55a, another similar request was submitted and approved (references 7, 8, & 9).

5. Proposed Alternative and Basis for Use As an alternative to the volumetric and surface examination coverage requirements shown as dimension "a" in Figure 2 of ASME Code Case N-729-1, WCGS proposes the use of attainable ultrasonic examination distances shown in Table 2. The required examination coverage dimension for the other penetrations will be met or exceeded.

to WO 16-0052 Page 5of13 Table 2: WCGS Inspection Coverage Obtained for CROM Penetrations Having Limited Coverage Penetration 9 (degrees) N-729-1 2006 Inspection 2013 Inspection No. Required Exam Coverage Coverage Coverage Obtained Obtained inches inches inches 77 48.7 1.0 0.6 .6 78 48.7 1.0 0.88 .64 Appendix I of ASME Code Case N-729-1 provides the analysis procedure for evaluation of an alternative examination area or volume to that specified in Figure i of Code Case N-729-1 if impediments prevent examination of the complete zone. Section 1-1000 of ASME Code Case N-729-1 requires, for alternative examination zones below the J-groove weld, that analyses shall be performed using at least the stress analysis method (Section 1-2000) or the deterministic fracture mechanics analysis method (Section 1-3000) to demonstrate that the applicable criteria are satisfied. The techniques described in Section 1-2000 were validated in WCAP-16589-P (Reference 2). The stress analysis in WCAP-16589-P was reviewed. The stress analysis was performed using the design weld dimensions specific to Wolf Creek. This analysis demonstrated that the hoop and axial stresses on the nozzle inside and outside surfaces remain below 20 ksi (tensile) over the entire region outside the alternative examination zone. When the WCAP-16589-P analysis was compared to the requirements of Section 1-2000, Stress Analysis, it was determined that the requirements of 1-2000 were met. The fracture mechanics analysis in WCAP-16589-P was also reviewed and compared to the requirements of 1-3000. Since the alternative examination zone is below the J-groove weld, the applicable requirements are those of 1-3200. The operating temperature of the head has not changed since the analysis in WCAP-16589-P was performed. After the review and comparison, it was determined that the technique described in Method 1 of 1-3200 was met by the WCAP, except that the source used for crack growth rate was EPRI MRP-55, Revision 1, not Appendix O of the 2004 Edition of Section XI. However, since the same formula for crack growth rate is used in both EPRI MRP-55 and Appendix 0, there is no technical difference, and WCAP-16589-P does meet the technical requirements for l-3200(a).

It is also noted that for alternative examination zones that eliminate portions of Figure 2 examination zone below the J-groove weld, that 1-1000 requires only the analysis method of either 1-2000 or 1-3000 to be performed Although not required, the deterministic fracture mechanics analysis described in Section 1-3000 was also validated in Reference 2.

5.1 Stress Analysis in Accordance with ASME Code Case N-729-1 Section 1-2000 Section 1-2000 of ASME Code Case N-729-1 requires that plant-specific analysis demonstrate that the hoop and axial stresses remain below 20 kips per square inch (ksi)

(tensile) over the entire region outside the alternative examination zone but within the examination zone defined in Figure 2 of the Code Case.

to WO 16-0052 Page 6of13 The distance below the J-groove weld that requires examination, as determined by the point at which the CROM penetration hoop stress distribution for the operating stress levels is less than 20 (ksi) tension, was obtained from Appendix A of Reference 2. Note that hoop stresses during steady state operation are much greater than the axial stresses.

The hoop stress distribution plots for penetrations 77 and 78 are provided in Figure 2 of this submittal. The hoop stress distribution plots in Figure 2 indicate that the minimum achievable inspection coverage below the bottom of the J-groove weld insures stresses remain below 20 ksi tensile over the entire region outside the alternative examination zone but within the examination zone defined in Figure 2 of ASME Code Case N-729-1.

The hoop stress distribution plots display the downhill side as this is more limiting. Also, stress distribution plots shown are for the inside and outside surface. Table 3 summarizes the distance from below the toe of the downhill side J-groove weld to where both the inside and outside surface hoop stress drops below 20 ksi for penetrations 77 and 78.

Table 3: Distance Below Toe of Downhill Side J-Groove Weld Where Hoop Stress is Less Than 20 KSI Penetration Source Distance Below Toe of Nozzle No. Downhill Side J-Groove Weld Where Hoop Stress

< 20 ksi (inch}

77 and 78 Figure 2 0.30 5.2 Deterministic Fracture Mechanics Analysis in Accordance with ASME Code Case N-729-1 Section 1-3200, Method 1 A fracture mechanics analysis was performed and documented in Reference 2. The analysis demonstrates that a potential axial crack in the unexamined zone will not grow to the toe of the J-groove weld prior to the examination frequency specified in Table 1 of ASME Code Case N-729-1.

(NOTE: WCAP-16589-P was prepared prior to approval to use Code Case N-729-1.

WCAP-16589-P referenced EPRI MRP-55 as the source for the crack growth formula used in the analysis, not Appendix 0 as required by Code Case N-729-1. However, since the same formula for crack growth rate is used in both EPRI MRP-55 and Appendix 0, there is no technical difference, and WCAP-16589-P does meet the technical requirements for 1-3200(a).)

(1) The following table provides the dimensions for nozzles 77 and 78 for both the designed and as-built configurations. The actual weld height was measured using the ultrasonic test data and is listed for the as-built dimension.

to WO 16-0052 Page 7 of 13 Penetration Nozzle Number As-designed As-built (inches) inches 77 1.46 1.98 78 1.46 2.04 The flaw evaluation in WCAP-16589-P is based on the as-designed J-groove weld dimensions which assumed a smaller weld throat than the as-built condition. Often, the as-built fillet weld dimension on the downhill side of the CROM nozzle is larger than the as-designed dimension because of access issues during fabrication. When the weld extends further down the outside surface of the head penetration nozzle due to a larger than as-designed fillet, it does not negatively affect the distance below the J-groove weld required for coverage. An assessment was performed on similar CROM design/configuration and showed that larger as-built J-groove welds have a reduced stress profile relative to smaller welds and also required lesser distance below the weld bottom for a transition to below 20 ksi. The cases considered were for weld heights of 1.46", 2.35" and 2.97" which were analyzed to determine their resulting stress profiles below the weld. The 20 ksi criterion is reached in shorter distance for the larger fillet welds. Therefore, the 1.46" as-design dimension bounds the as-built dimensions of the CROM nozzles for the current flaw evaluation.

The fracture mechanics analysis was performed using input from the previously discussed stress analysis. The results of the analysis are shown as flaw tolerance charts, which can be used to determine minimum required inspection coverage. This insures that any flaws initiated below the weld, in the region of the penetration nozzle not being inspected, would not reach the bottom of the weld before the next inspection. The flaw tolerance chart for penetrations 77 and 78 is presented in Figure 3.

The flaw tolerance chart in Figure 3 demonstrates that a postulated through-wall flaw at the bottom edge of the proposed alternative examination zone will not grow to the toe of the J-groove weld within_ an inspection interval of four refueling cycles. The crack growth prediction shows greater than six effective full power years (EFPY) of operation required to grow the postulated flaw to the toe of the weld. Additionally, the assumed initial upper extremity locations of axial through-wall flaws are conservative based on achievable inspection coverage, because the assumed upper crack extremities are located within the achievable inspection zone.

Examination of portions of the nozzle significantly below the J-groove weld is not pertinent to the phenomena of concern, which include leakage through the J-groove weld and circumferential cracking in the nozzle above the J-groove weld. In all cases, the measured coverage is adequate to allow WCGS to continue to operate prior to the hypothetical flaws reaching the J-groove weld. In accordance with 10 CFR 50.55a(g)(6)(ii)(O) requirements, the next required examination would be completed prior to potential flaw propagation into the J-groove welds.

5.3 Surface Examination 10 CFR 50.55a(g)(6)(ii)(0)(3) states in part that "if a surface examination is being substituted for a volumetric examination on a portion of a penetration nozzle that is to WO 16-0052 Page 8of13 below the toe of the J-groove weld, the surface examination shall be of the inside and outside wetted surface of the penetration nozzle not examined volumetrically."

To reduce personnel radiation exposure, the nozzles are typically inspected using remotely operated volumetric examination equipment. Although dye penetrant testing of threaded surfaces is possible, it is not practical. The threaded outside diameter (OD) makes a dye penetrant examination on the lower section of the penetration impractical because of excessive bleed out from the threads. Eddy current examination would similarly not be effective due to the threaded configuration. Current known radiation levels under the reactor vessel head are 4.5 Rem/hr at the bottom of 1 CROM nozzle.

This could result in an exposure of approximately 1.5 Rem per nozzle using 4500 mRem/hr and 20 minutes/nozzle. At this time our estimates of dose rates (based on recent measurements in the area) range from 4.5 Rem/hr to 1O Rem/hr at the bottom of the CROM nozzles, the expected dose ranges from approximately 1.5 Rem to 3.3 Rem per nozzle to perform surface examination.

Therefore, no alternative is proposed for the two CROM nozzles with limited examination coverage below the J-groove weld.

Shielding to some extent is possible but would do little to reduce the overall whole body submersion exposure of 2400 mRem/hr as shown in survey WCNOC-1610-0192.

Therefore it would be impractical to install shielding at this location, due to the additional dose consumed installing being greater than the resultant savings.

6. Duration of Proposed Alternative The alternative requirements of this request will be applied for the remaining duration of the current 4th 10-year lnservice Inspection (ISi) Interval which ends on September 2, 2025.

7. Precedents Similar relief requests have been granted to the following plants:

• NRC Safety Evaluation dated December 22, 2009, for San Onofre Nuclear Generating Station, Units 2 and 3, "Relief Request ISl-3-29, Request for Relief from Inspection Requirements of ASME Code Case N-729-1 for Control Element Drive Mechanism Penetrations (TAC Nos. ME0768 and ME0769)"

(ML093441035)

• NRC Safety Evaluation dated March 3, 2011, for Braidwood Station Units 1 and 2, and Byron Station Units 1 and 2, "Relief Request from ASME Code Case N-729-1 Requirements for Examination of Reactor Vessel Head Penetration Welds (TAC Nos. ME3510, ME3511, ME3512 and ME3513)" (ML110590921) to WO 16-0052 Page 9of13

• NRC Safety Evaluation dated January 4, 2013, for Wolf Creek Generating Station, 'Wolf Creek Generating Station - Request for Relief No. 13R-07 for the Third 10-Year lnservice Inspection Program Interval (TAC No. ME9078) to WO 16-0052 Page 10of13

8. References

1. ASME Code Case N-729-1, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division 1," March 28, 2006.

2. WCAP-16589-P, Revision 0, "Structural Integrity Evaluation of Reactor Vessel Upper Head Penetrations to Support Continued Operation: Wolf Creek," August 2006.

3. WCNOC letter ET 06-0035 from T. J. Garrett, WCNOC, to USNRC, "Relaxation Request from the First Revised NRC Order EA-03-009 Regarding Requirements for Nondestructive Examination of Nozzles Below the J-Groove," October 5, 2006.

4. WCNOC letter ET 06-0048 from T. J. Garrett, WCNOC, to USNRC, "Additional Information Related to the First Revised NRC Order EA-03-009 Regarding Requirements for Nondestructive Examination of Nozzles Below the J-Groove,"

November 1, 2006.

5. NRC letter from D. Terao, USNRC, to R. A. Muench, WCNOC, "Wolf Creek Generating Station - Request to Relax Nondestructive Examination of Reactor Pressure Vessel Head Penetration Nozzles in First Revised Order EA-03-009 (TAC NO. MD3210)," December 7, 2006.

6. NRC letter EA-03-009, "Issuance Of First Revised NRC Order (EA-03-009)

Establishing Interim Inspection Requirements For Reactor Pressure Vessel Heads At Pressurized Water Reactors," February 20, 2004.

7. WCNOC letter ET 12-0010 from J. P. Broschak, WCNOC, to USNRC, "10 CFR 50.55a Request Number 13R-07, Relief from ASME Code Case N-729-1 Requirements for Examination Of Reactor Vessel Head Penetration Welds," July 2, 2012.

8. WCNOC letter ET 12-0024 from J. P Broschak, WCNOC, to USNRC, "Response to Request for Additional Information Regarding 10 CFR 50.55a Request Number 13R-07 " Relief from ASME Code Case N-729-1 Requirements for Examination of Reactor Vessel Head Penetration Welds," October 15, 2012.

9. NRC letter from M. T. Markley, USN RC, to M. W. Sunseri, WCNOC, "Wolf Creek Generating Station - Request for Relief No. 13R-07 for the Third 10 Year lnservice Inspection Program Interval (TAC NO. ME9078)," January 4, 2013.

to WO 16-0052 Page 11 of 13 Figure 1 WCGS Reactor Vessel Head Penetration Ends 3.572":*°9"'. DIA.

R.060" 3. 75"-BN-2A

. 203" '.*'!!',~.:* R 20*

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