DCL-14-068, Response to NRC Request for Additional Information Regarding Relief Request SWOL-REP-1 U2
| ML14217A407 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/05/2014 |
| From: | Allen B Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| DCL-14-068, TAC MF3891 | |
| Download: ML14217A407 (15) | |
Text
Pacific Gas and Electric Company Barry S. Allen Diablo Canyon Power Plant Site Vice President Mail Code 104/6 P. 0. Box 56 August 05, 2014 Avila Beach, CA 93424 805.545.4888 Internal: 691.4888 PG&E Letter DCL-14-068 Fax: 805.545.6445 U.S. Nuclear Regulatory Commission 10 CFR 50.55a ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-323, OL-DPR-82 Diablo Canyon Unit 2 Response to NRC Request for Additional Information Regarding Relief Request SWOL-REP-1 U2
References:
- 1. PG&E Letter DCL-14-028, "lnservice Inspection Program Relief Request SWOL-REP-1 U2 for Approval of an Alternative to the ASME Code,Section XI, for Preemptive Full Structural Weld Overlays," dated April 7, 2014 (ML14101A245)
- 2. PG&E Letter DCL-14-051, "Submittal of Supplemental Analysis for lnservice Inspection Program Relief Request SWOL-REP-1 U2," dated June 11, 2014 (ML14171A236)
- 3. NRC Letter, "Diablo Canyon Power Plant, Unit No. 2- Request for Additional Information RE: Relief Request SWOL-REP-1 U2, Alternative Acceptance Criteria for Flaws in Pressurizer Nozzle Welds (TAG No. MF3891), dated July 21, 2014.
In Reference 1, Pacific Gas and Electric Company (PG&E) submitted Relief Request SWOL-REP-1 U2 for approval of an alternative to the ASME Code,Section XI, Repair/Replacement rules as applied to the Diablo Canyon Power Plant Unit 2 pressurizer structural weld overlays. In Reference 2, PG&E submitted the supplemental analysis that evaluated the reported flaw sizes with additional margin to account for possible flaw sizing variations that are associated with the repeatability of manual ultrasonic examination results.
The NRC Staff provided a request for additional information (RAI), via letter dated July 21, 2014 (Reference 3). The Enclosure to this letter provides PG&E's response to the NRC RAI.
A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
- Comanche Peak
- Diablo Canyon
- Palo Verde
- Wolf Creek
Document Control Desk PG&E Letter DCL-14-068 August05,2014 Page 2 PG&E makes a new regulatory commitment to submit revised proprietary and non-proprietary versions of AREVA Calculations no later than August 20, 2014. AREVA calculations are being revised to show data associated with flaw length and certain other parameters as non-proprietary information.
If you have any questions or require additional information, please contact Mr. Tom Baldwin at (805) 545-4720.
Sincerely, Barry Site Vice President RNTT/4231 /50033145 Enclosure cc: Diablo Distribution cc/enc: Peter J. Bamford, NRC Project Manager Marc L. Dapas, NRC Region IV Administrator Thomas R. Hipschman, NRC Senior Resident Inspector Gonzalo L. Perez, Branch Chief, California Department of Public Health State of California, Pressure Vessel Unit
- A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
- Comanche Peak
- Diablo Canyon
- Palo Ve r de
- Wolf Creek
Enclosure PG&E Letter DCL-14-068 PG&E Response to NRC Request for Additional Information Regarding Relief Request SWOL-REP-1 U2 NRC Question 1:
Attachment 1 to the letter dated April 7, 2014, contains a root cause summary for the missed flaws. The submitted information focuses on the deficiency of ultrasonic testing and not the deficiency in the welding of the overlay. Please discuss the cause of fabrication defects in the weld overlays of the pressurizer nozzles.
PG&E Response:
Structural weld overlays (SWOLs) are applied to nozzles in both the 6G (approximately 45° angle weld position), and the 2G (approximately horizontal weld position). In the 2G position, the weld pool maintains a consistent relationship with respect to gravity, thus minimizing the potential fora discontinuity to form as the weld application is uniform during the evolution of the SWOL.
In the 6G position, the weld is deposited in varying positions, ranging from flat to horizontal as the weld is applied around the nozzle circumference. Thus, the weld pool is continuously altering its orientation relative to gravitational forces.
With the weld pool's centroid continually changing position as it traverses around the 6G nozzle orientation, there is more risk of discontinuity formation versus the 2G welding positions.
Even though more welding discontinuities might be expected when welding in the 6G position compared to the 2G position, as discussed below, when using Alloy 52/52M filler metal, discontinuities may occur regardless of welding position.
As discussed, the 6G weld position poses a higher potential for discontinuity formation due to the continuing positional relationship changes of the weld pool with respect to gravity, particularly in the transition radius of the nozzle. In the SWOL, the discontinuities are likely depicting incomplete fusion between the first weld layer weld and base material or interbead incomplete fusion. The basis for this conclusion is discussed below.
The ASME Section XI Working Group Welding Committee, who developed Code Case N-7 40 used as a basis for this relief request, recognized and acknowledged the challenge of welding 30 percent chromium welding filler metal alloys (i.e., 52, 52M fillers), as being very sluggish (low fluidity) filler metals to weld. This sluggishness is due to its higher viscosity creating an inherent slower response of the filler metal to changes normally occurring during welding. This sluggishness is more noticeable on first layer welds due to the dilution of the low alloy steel substrate of the component, and may even be apparent on the 1
Enclosure PG&E Letter DCL-14-068 second layer until the weld chemistry becomes more consistent on the third and remaining layers of the SWOL.
In order to address these concerns, the ASME working group recognized the challenge of preventing or eliminating the occasional interlayer or interbead incomplete fusion defect. A typical overlay contains hundreds of weld beads and the Code Case was developed to ensure these small, incomplete fusion (i.e.,
minimal through thickness dimension) discontinuities are not detrimental to the structural integrity of the SWOL and are mitigated through the robust overlay design criteria of the Code Case. The Code Case further specifies ultrasonic testing (UT) acceptance criteria to permit laminar type flaws thus addressing the welding challenge of the 30 percent chromium alloys.
NRC Question 2:
Section 5.3 (page 18) of the Enclosure to letter dated April?, 2014, states that the initial planar flaw depth is 0.08 inches. This flaw depth is about 5 percent of the wall thickness. The NRC staff requests the following information regarding this small flaw depth: (a) please discuss how 0.08 inches was obtained, and (2) discuss the accuracy of the measurement of this flaw.
PG&E Response:
a) The 0.080 inches dimension was obtained using the Phased Array Ultrasonic (UT) procedure EPRI-WOL-PA-1, Revision 2, "Procedure for Manual Phased Array Ultrasonic Examination of Weld Overlaid Similar and Dissimilar Metal Welds." As noted in Section 5.3 of the April 7, 2014, submittal, the indications in Safety Nozzle A are primarily laminar in nature and conservatively assigned a through-wall dimension. The indications were characterized by the UT Levell II examiner as two distinct laminar reflectors, resulting from two separate weld bead non-fusion areas in close proximity to each other. Ultrasonic data plots position the indications on either side of the transition to the nozzle boss shoulder, resulting in a slight difference in measured depth due to location of one indication on the tapered shoulder (see sketch in PG&E response to NRC Question 12) . .Although no planar content was detected, due to their close proximity, the indications were assigned the 0.080 inches through-wall dimension used for the analysis.
b) As the indications are laminar and parallel, or close to parallel, to the outer diameter surface, the depth is best measured with the lower angles of the phased array probe. Since the beams used for measurement are essentially .
normal to the reflector, the process closely resembles a straight beam thickness measurement. Similar to straight beam thickness measurements, the instrument simply uses signal transit time to calculate depth. This process is inherently more accurate and repeatable as compared to the length sizing process, which is amplitude based and relies on examiner interpretation of signal response characteristics.
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Enclosure PG&E Letter DCL-14-068 NRC Question 3:
Section 7.0 of the Enclosure to letter dated April 7, 2014, states, in part, that "The alternate examination qualification requirements will be applied until the end of the SWOL subsequent examination schedule." It is not clear to the NRC staff what is me,ant by applying the alternate examination qualification requirements until the end of the SWOL subsequent examination schedule.
Please explain the above statement in detail. In particular, include the following:
(a) an *explanation of why PG&E proposes to wait until at the end of three successive examinations to apply the alternate examination qualification requirements, and (2) a description of the alternate examination qualification requirements. Also, please discuss the future examination schedule and technique that will be used after the three successive examinations are completed.
PG&E Response:
The "alternate examination qualification requirements" refers to the use of the Performance Demonstration Initiative (PDI) program qualification process in lieu of ASME Section XI Appendix VIII requirements. This was previously approved for Diablo Canyon Power Plant (DCPP) in the Safety Evaluation Report (ADAMS Accession No. ML080110001 ), dated February 6, 2008, as part of Relief Request REP-1 U2 for the Application of Weld Overlay on Dissimilar Metal Welds of the Pressurizer Nozzles. The alternate qualification requirements will be applied for the next and all subsequent examinations. This will allow the continued application of the currently approved examination procedures by qualified personnel. PG&E understands that new rulemaking or regulatory actions affecting the use of the above noted procedures or qualification program during the duration of the SWOL subsequent examination schedule must be addressed as applicable. Examinations will commence in the Unit 2 eighteenth refueling outage and continue as per previous commitment without delay.
At the conclusion of the required examinations in the next three periods, if the flaws remain essentially unchanged, the examination schedule will revert to the original schedule of successive inspections per ASME Section XI IWB-2420(c).
NRC Question 4:
Please provide the beginning and end dates of the third inservice inspection interval.
PG&E Response:
The DCPP Unit 2 third inservice inspection interval commenced on July 1, 2006, and is nominally scheduled to end on March 16, 2016.
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Enclosure PG&E Letter DCL-14-068 NRC Question 5:
Section 4.4 of Attachment 2 (Calculation No. 32-9215965-001, "Diablo Canyon Unit 2 Pressurizer Safety/Relief Nozzles Laminar/Planar Flaw Analysis") to the letter dated April 7, 2014 (Attachment 2 is proprietary, a non-proprietary version available as Attachment 9), states that the number of reactor coolant system transients is" .. . established for 60 years of design life"; however, it is not clear whether this statement applies to Table 4-4. Please confirm whether the design transient cycles shown in Table 4-4 of Calculation No. 32-9215965-001 are for 60 years of plant life.
PG&E Response:
The design transient cycles shown in Table 4-4 of Calculation No. 32-9215965-001, for DCPP Unit 2, are for 60 years of plant life. These are consistent with the transient cycles as reflected in Table 4.3-2 in Section 4 of the license renewal application for DCPP Unit 1 and Unit 2 (ML093340086) .
NRC Question 6:
Attachment 5 to the letter dated April 7, 2014, Calculation 32-9049062-004, "Diablo Canyon Unit 2 Pressurizer Safety/Relief Nozzle Weld Overlay Residual Stress Analysis" (a non-proprietary version of Attachment 5 is available as Attachment 12), indicates that the safety/relief nozzle weld overlay residual stress analysis simulated a weld repair as result of a fabrication defect during construction. Please discuss the flaw depth as a percent of the wall thickness that the weld repair was simulated. Also, please justify the flaw depth used in the simulation (e.g., was the flaw depth simulated based on records showing the actual depth of the weld repair during construction?)
PG&E Response:
Based on limited weld fabrication records that were foun,d during the original performance of the weld residual stress (WRS) analysis conducted in the 2007 time-frame, it appeared that some repairs were performed as reflected in radiograph data sheets. A weld repair that is 33 percent of the original dissimilar metal weld (DMW) wall thickness was used in the analysis. The assumed weld repair maximizes the welding stresses incurred in the DMW prior to applying the overlay. EPRI's MRP-287 guidelines (issued in 201 0) suggest assuming a 50 percent inside diameter (I D) repair when no fabrication records are available. It is noted that the WRS analysis for the spray nozzle, which has a similar diameter to the safety/relief nozzles, used a 50 percent through-waiiiD repair.
To assess the impact that the depth of the weld repair may have on the WRS, a comparative evaluation is made between the WRS calculated for the safety/relief nozzles with the 33 percent through-wall repair (Calculation No. 32-9049062-4
Enclosure PG&E Letter DCL-14-068 004) and the spray nozzle with 50 percent through wall repair (Calculation No.
32-9049061-005). Recognizing that there are differences between the safety/relief and spray nozzle geometries, a straightforward comparative assessment is made for the calculated WRS that are listed in Table A-1 in each of Calculation No. 32-9049062-004 (safety/relief nozzles with 33 percent through-wall repair) and Calculation No. 32-9049061-005 (spray nozzle with 50 percent through-wall repair). The WRS at the overlay/original material interface, which is the location of the reported laminar indications, for both the Spray nozzle (50 percent ID repair) and the safety/relief nozzles (33 percent ID repair),
are best estimated from the nozzle-side stress results reported along path lines FR_1 and FR 1, respectively. By reviewing the axial and hoop WRS, it is concluded that the hoop stresses were within 10 percent and the axial stresses were within 15 percent for the two repair weld scenarios. This shows that the depth of the repair weld will have a very small impact on the evaluation of the laminar indications.
NRC Question 7:
Attachment 5 to the letter dated April 7, 2014, Calculation 32-9049062-004, "Diablo Canyon Unit 2 Pressurizer Safety/Relief Nozzle Weld Overlay Residual Stress Analysis," Table C-1, presents bounding radial and shear stresses for interfacial path lines. However, the bounding radial and shear stresses in Table C-1 are different from the bounding radial and shear stresses in Table B-1 in Calculation No. 32-9215965-002 in the June 11, 2014, supplement. Please clarify why the stresses in these two tables are not the same.
PG&E Response:
Stresses reported in these two tables were sampled along two different path lengths. The stresses in Table C-1 in Calculation No. 32-9049062-004 were sampled for analyzing the as-measured indications with no allowance made for flaw-size measurement uncertainty. The stresses in Table B-1 of Calculation No. 32-9215965-002 were ~amp led for longer path lines that account for uncertainty in the flaw-size measurements. The stresses from the longer path lines were used to analyze the wider flaws, which include uncertainty in the flaw-size measurements.
NRC Question 8:
Attachment 4 to the letter dated April 7, 2014, Calculation No. 32-9049114-003, "Diablo Canyon Unit 2 Pressurizer Safety/Relief Nozzle Weld Overlay Structural
. Analysis," page 11 (a non-proprietary version of Attachment 4 is available as Attachment 11 ), states, in part, that the barrier layer "is not modeled in detail in this analysis and is covered by the weld overlay filler material. The effect on the results is negligible ... " The impact of the barrier layer on the original weld and weld overlay may result in fabrication defects in the overlaid weld, thermal stresses due to differences in thermal expansion of different weld materials, and 5
Enclosure PG&E Letter DCL-14-068 weld shrinkage. Please explain why the effect of the barrier layer on the results is negligible. Also, please discuss the length and thickness of the barrier layer.
PG&E Response:
The weld overlay (including the barrier layer volume) is modeled as an Alloy 52M weld. The barrier layer, as illustrated in the sketch below, is primarily stainless steel (SS) weld that only covers the SS portions of the underlying materials, namely the safe end, the SS weld and the SS pipe. From the stress analysis view point, the thermal expansion of the barrier layer is similar to those of the SS safe end, the SS weld and the SS pipe. Modeling the barrier layer as Alloy 52 increases the Alloy 52's volume slightly compared to the actual design configuration. Since the volume of the barrier layer is small (length is limited to the region as shown in the sketch below and the thickness of the barrier layer is a single bead layer) in comparison with the volume of Alloy 52M weld, this assumption is justified.
Extent of Barrier Layer
- Barrier Layer SS Pipe
- Illustration of Barrier Layer Extent End of Overlay at Pipe to OM Weld Actual Length Varies from Nozzle to Nozzle Not to Scale NRC Question 9:
Attachment 4 to the letter dated April 7, 2014, Calculation No. 32-9049114-003, Section 4. 5, page 18, states, in part, that "External forces and moments are evaluated by hand calculation and added to the results from the finite element analysis." Please clarify whether the external forces and moments as shown in Tables 8 and 9 refer to the forces and moments from the pipe that exert onto the nozzle. Also, please discuss why pressure is not an applied load in Tables 8 and 9.
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Enclosure PG&E Letter DCL-14-068 PG&E Response:
The external forces and moments as shown in Tables 8 and 9 refer to the forces and moments applied at the safe end to pipe weld. The pressure forces are not part of the external loads described in Tables 8 and 9. The pressure forces were calculated as an endcap pressure load, which is calculated and applied to the finite element model as a boundary condition. The endcap force is a function of pressure and the magnitude changes as the pressure fluctuates during a transient. Thus, the endcap pressure could not be conveniently listed in Tables 8 and Table 9. Refer to Figure 4 on page 17, which illustrates the endcap pressure. The end cap pressure ( p*) is defined on page 15 of Calculation No. 32-9049114-003.
NRC Question 10:
Attachment 3 to the letter dated April 7, 2014, Calculation No. 32-9213780-001, "Diablo Canyon Unit 2 Pressurizer Spray Nozzle Laminar Flaw Analysis, "Section 3.3, page 15 (a non-proprietary version of Attachment 3 is available as Attachment 10), states, in part, that "Multiple laminar flaws in Reference [1] are combined into larger, bounding flaws and extended to include a complete 360° arc length for crack growth calculations." Tables 7-5 and 7-6 provide initial flaw length and flaw width. Please discuss how the laminar flaws are combined into the bounding flaws.
PG&E Response:
On page 15, the flaw combination to include 360° arc length was made to calculate the stress intensity factor (K) used in the crack growth calculations. For crack growth calculations, the bounding flaw size was established based on the combined flaws width and the full 360° arc length. Tables 7-5 and 7-6 of Calculation No. 32-9213780-001, show the bounding laminar flaws based on the bounding flaw width and the bounding flaw length. The laminar flaws were combined into the bounding flaws using the rules illustrated in ASME Figure IWA-3360-1. Flaws that overlap or are within a distance of 1 inch (25 mm) of one another are combined to form a bounding flaw. The flaw interaction rule was considered for both the axial width and circumferential length of the flaws.
NRC Question 11:
Table 4-2 of Attachment 3, Calculation No. 32-9213780-001, shows the bounding flaws for laminar indications numbers 1 through 4. Note 5 to Table 4-2 explains how the short indications were combined into two groups of bounding flaws. In Table 1 (page 34) of the April 7, 2014 submittal, Indication 4 has a length of 20.1 inches. However, the length of 20.1 inches is not considered in Table 4-2 of Calculation No. 32-9213780-001 and appears to be not considered 7
Enclosure PG&E Letter DCL-14-068 in the analysis. Please explain why the 20.1-inch length is not considered in the flaw analysis.
PG&E Response:
For the stress intensity factor calculations, used in the crack growth analysis, a two-dimensional center-cracked plate model was used, which conservatively represents the flaw as infinitely long in the circumferential direction of the nozzle.
Thus the flaw length was fully bounded by the model geometry in the crack growth calculations and the 20.1 inch length is not explicitly used.
As a matter of clarification, the 20.1 inch length for indication 4 in Table 1 (page 34) of the April 7, 2014 submittal was conservatively estimated as the difference between the start and stop positions on the flaw size measurement.
Calculation No. 32-9213780-001 attempts to remove conservatism in the previously reported 20.1 inch flaw length by taking advantage of the rules in ASME Figure IWA-3360-1 for combining the flaws. In Calculation No. 32-9213780-001, the flaws that are separated by a distance greater than 1 inch were not combined. This flaw length is only used for the purpose of calculating the laminar flaw area.
The following questions relate to the supplement dated June 11, 2014.
NRC Question 12:
Attachment 1, Calculation No. 32-9215965-002, "Diablo Canyon Unit 2 Pressurizer Safety/Rerief Nozzles Laminar/Planar Flaw Analysis," Table C-2, (a non-proprietary version of Attachment 1 is available as Attachment 4), indicates that the measurement uncertainty was added to the flaw width. Please discuss why the measurement uncertainty was not added to the flaw length. Also, the measurement uncertainty was added to the laminar flaw lengths, but not to the planar flaw lengths. Discuss why the planar flaw lengths were not added with the measurement uncertainty and analyzed for crack growth.
PG&E Response:
Laminar Flaw Length Evaluation For laminar crack growth analysis, a two-dimensional model is used and as such the length is considered to be infinitely long. Consequently, the flaw uncertainty did not need to be considered for the laminar flaw length for the purpose of crack growth analysis. The actual length of laminar flaw is only used in the calculations for the flaw area. The laminar flaw area was not used to demonstrate structural integrity of the weld overlay. Thus, considering the flaw uncertainty in the laminar flaw length measurements is inconsequential to the conclusions made in the document.
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Enclosure PG&E Letter DCL-14-068 Postulated Planar Flaw Evaluation There was no actual planar (through-wall) content reported in the Unit 2 seventeenth refueling outage (2R 17) examination of Safety Nozzle A overlay.
The original planar flaw evaluation was conservatively performed since there was a 0.080-inch difference in depth of the two adjacent laminar indications due to the underlying parent component geometry (see sketch on following page). The planar flaw evaluation assumed the theoretical planar flaw to have a through-wall dimension of 0.080 inch and a circumferential length of 360°. The structural calculations, predict very small planar (through-wall) flaw growth (essentially no real flaw growth) assuming an initial planar flaw of 0.080 inch depth.
Accuracy of UT Depth Sizing vs. Length Sizing Laminar Reflectors As discussed in request for additional information response 2b, the phased array UT depth sizing process is time based while the length sizing process is amplitude based. The accuracy of the time based depth measurements is not affected by several process variables that influence the amplitude based length measurements. Consequently, depth measurements are inherently more accurate than length measurements.
Margin Discussion The additional structural calculations performed by PG&E to incorporate axial length margin are intended to allow for potential minor axial length measurement differences in future inspections that may arise from manual phased array UT length sizing process variables.
Since phased array depth sizing of laminar reflectors is accurate and no actual planar content was detected in the 2R 17 examinations, margin for depth sizing measurement is deemed unnecessary. In the event that an actual planar flaw developed in the future, the phased array UT process is well suited to detect that condition and the indication(s) would be re-assessed at that time.
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Enclosure PG&E Letter DCL-14-068 Laminar Ind. 1a Safety Nozzle A Laminar (lack of bond) Indications 1&1A Illustration of Relative Positions and Depths Not to Scale 4- Pressurizer SA-508 Nozzle Forging 10
Enclosure PG&E Letter DCL-14-068 NRC Question 13:
Attachment 1, Calculation No. 32-9215965-002, Table C-2, shows that the flaw in safety nozzle A exceeded the allowable flaw area limit. The submittal states that flaw acceptance by analytical evaluation is permitted by the ASME Code,Section XI, IWB-3132.3 when acceptance standards are exceeded. IWB-3132.3 requires that the analytical evaluation be performed in accordance with IWB-3600. However, the submittal states that it used the design rules of the ASME Code, Section Ill, to establish the weld overlay length. Please discuss why ASME Code,Section XI, IWB-3600 was not used to accept the flaw in safety nozzle A when it exceeded the allowable limit of IWB-3514.6. This question also applies to Indications 1 and 4 in Table A-2 of Calculation No. 32-9213780-002, "Pressurizer Spray Nozzle Laminar Flaw Analysis" (Attachment 2 to the letter dated June 11, 2014, with a non-proprietary version available as Attachment 5).
PG&E Response:
In lieu of not meeting the nondestructive examination acceptance standards of IWB-3514.6 (Table IWB-3514-3), flaw acceptance was evaluated by analysis using ASME Section XI IWB-3600 acceptance criteria. Flaw acceptance by analytical evaluation is permitted by IWB-3132.3 when acceptance standards are exceeded. In this application, the nozzle indications were evaluated to IWB-361 0 as applied to Class 1 vessels. The flaw acceptance requirements of IWB-361 O(d) state that the flaw is acceptable for continued service for the evaluated period if the following are satisfied:
- 2) The primary stress 'limits of NB-3000 assuming a local area reduction of the pressure retaining membrane Because the laminar indications are contained within the ductile austenitic weld overlay material, the structural margins of IWB-3612 for normal/upset and emergency/faulted conditions do not need to be explicitly determined due to the high fracture toughness properties of the Alloy 52 weld metal. The stress limits under NB-3000 were addressed by the referenced analytical evaluation using ASME Section Ill design rules to establish the allowable overlay weld length. The actual overlay length minus the flaw length was determined to exceed the minimum required overlay length to meet the NB-3000 stress limits as required by IWB-361 O(d)(2).
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Enclosure PG&E Letter DCL-14-068 Thus it was concluded that the laminar indications in the safety/relief and spray nozzles are acceptable to IWB-361 0 flaw acceptance requirements for the evaluation period of 38 years of plant operation .
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Attachment 1 PG&E Letter DCL-14-068 Commitment PG&E makes a new regulatory commitment to submit revised proprietary and non-proprietary versions of AREVA Calculations no later than August 20, 2014. AREVA calculations are being revised to show data associated with flaw length and certain other parameters as non-proprietary information.