ML20236W344

Safety Evaluation Accepting Relief Requests for Second 10-yr ISI for Plant,Units 1 & 2

ML20236W344
Person / Time
Site:	Hatch
Issue date:	07/30/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20236W339	List: ML20236W336 ML20236W344
References
NUDOCS 9808050222
Download: ML20236W344 (17)

Text

_ _ - _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ - _ - - - - _ __

patrg g i UNITED STATES O

NUCLEAR REGULATORY COMMISSION E WASHINGTON, D.C. 20066 4001

\*****/

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUESTS FOR RELIEF FOR SECOND 10-YEAR INTERVAL INSERVICE INSPECTION SOUTHERN NUCLEAR OPERATING COMPANY. INC.

EDWIN 1. HATCH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-321 AND 50-366

1.0 INTRODUCTION

The Technical Specifications (TS) for Edwin 1. Hatch Nuclear Plant (Hatch), Units 1 and 2, state that the inservice inspection of the American Society of Mechanical Engineers (ASME) Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (ASME Code) and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(6)(g)(i). Section 50.55a(a)(3) states that attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed attematives would provide an acceptable level of quality and safety, l or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Saction XI of the ASME Code for Hatch Units 1 and 2 second 10-year inservice inspection (ISI) interval is the 1980 Edition through Winter 1981 Addenda.

Pursuant to 10 CFR 50.55a(g)(5), if Southem Nuclear Operating Company, Inc. (the licensee) l determines that conformance with an examination requirement of Section XI of the ASME Code

! is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief.

Enclosure 1 9008050222 PDR 980730 G ADOCK 05000321 PDR

- 2.0 EVALUATION By letter dated December 17,1996, the licensee submitted its second 10-year interval inservice inspection program plan requests for relief for Hatch, Units 1 and 2. In addition, the licensee provided additional information in its letters dated August 29 and October 6,1997.

The NRC staff, with technical assistance from its contractor, the Idaho National Engineering and Environmental Laboratory (INEEL), has evaluated the information provided by the licensee in' support of its Second 10-Year Interval Requests for Relief Nos. RR-2.1.3, Rev 1; RR-2.1.11; RR-2.1.12; RR-2.1.13; and RR-2.1.14 for Hatch, Units 1 and 2. Based on the results of its review, the staff adopts the contractor's conclusions and recommendations presented in the Technical Letter Report (Enclosure 2).

Reauest for Relief No. RR-2.1.3 (Rev. ik The ASME Code,Section XI, requirements for Examination Category B-D, item B3.90 requires 100 percent volumetric examination of all reactor pressure vessel nozzle-to-vessel welds as defined by Figure IWB-2500-7. Additionally,Section XI, Paragraph IWA-2232 requires ultrasonic examination of vessels greater than 2-inch thickness in accordance with the ASME Code,Section V, Article 4. Article 4 requires two-directional coverage when practical. Pursuant to 10 CFR 50.55a(g)(6)(i), the licensee requested relief from performing the volumetric examination to the extent required by the ASME Code for the following reactor pressure vessel (RPV) nozzle-to-vessel welds.

@ t , X ,.  % q 9H 4 Table tiY@ 1;nM% MM$Wh$fM IM9  % i Unit!1MM M *DidC Unit- 2W43

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• Dese,;p;;er,0 .i1 WaldNumbers JCoverage s Wold Numbers iCoverage 1 l

Recirculation Outlet Nozzle N1 A, 8 60 % 2N1A,B 80 %  !

Recirculation inlet Nozzle N2A-H, J-K 35% 2N2A-H, J-K 60 % i Main Steam Nozzle N3A,B,C 75 % 2N3A-D 60 % i N3D 45 %

Feedwater Nozzle N4A-D 45% 2N4A-D 60 %

Core Spray Nozzle N5A,B 45 % '2NSA,B 65 %

l Head Spray Nozzle N6A,B 45 % 2N6A,B 45% i Head Vent Nozzle N7 50 % 2N7 50 %

l Jet Pump Instrument Nozzle N8A,B 55 % 2N8A,B 55 %

CRD Inlet Nozzle N9 50 % 2N9 50 %

1 U-__-_-____-_. ._.

j

t The Code requires 100 percent ultrasonic examination of nonle-to-vessel welds during each

inspection interval. However, as explained in the licensee's submittals, the nonles' geometric configurations limit the cumulative ultrasonic coverage for the subject nonle-to-vessel welds to between 35 percent and 80 percent of the Code-required volume, as shown in Table 1.

Additionally, the Code-required two-directional coverage of the examination volume could not be obtained due to the complex curvature of the nonle and only one directional coverage from the vessel (or head) side was feasible. Therefore, the 100 percent volumetric examination coverage is impractical for the subject RPV nonle-to-vessel welds. To gain access for the Code-required examination, the RPV would have to be redesigned and modifed. Imposition of this requirement would cause a considerable burden on the licensee.

The most probable failure mechanism for the subject RPV nonie-to-vessel welds involves a radial flaw propagating from the vessel inner diameter (ID) surface. The limited one-directional examinations performed have provided coverage of the portion of the weld volume nearest the vessel ID; therefore, existing flaws would have been detected.

The licensee has ultrasonically examined a cumulative volume of approximately 35 percent to 80 percent of respective RPV noule-to-vessel welds. These examinations, in addition to the visual examination of the vessel ID, provide reasonable assurance that any pattoms of degradation would have been detected.

The staff determined that it is impractical to meet the Code requirements for the subject welds and that the examinations completed on the ID of the RPV provide reasonable assurance of operational integrity of the subject components. The staff determined that relief is granted <

pursuant to 10 CFR 50.55a(g)(6)(i). I l

Raouest for Relief No. RR-2.1.11 (Unit 1 on!vt ASME Code,Section XI, Examination Category B-G-1, item B6.40 requires volumetric examination of the threads in the RPV flange during l each inspection interval as defined by Figure IWB-2500-12. Pursuant to 10 CFR 50.55a(g)(6)(i), the licensee requested relief from the volumetric examination coverage requirements defined in ASME Section XI, Figure IWB-2500-12, for the RPV flange ligaments l for Hatch, Unit 1.

The Code requires that the ultrasonic examination of the R?V flange threads includes the volume 1 inch from the threaded bushings. However, for the RPV fitnge ligaments for Hatch, I Unit 1, the ultrasonic examination is limited by 0-ring grooves located both inside and outside of

, the bolting ring. Therefore, examination of the Code-required volume is impractical for the l Hatch, Unit 1, RPV flange threads. To achieve the Code-required examination coverage, the l RPV would have to be redesigned and modified. Imposition of this requirement would cause a  !

considerable burden on the licensee.

The licensee has completed a significant portion (75 percent) of the Code-required volumetric examination of the RPV flange threaded ligaments, including all of the volume adjacent to the threaded bushings. Therefore, the staff determined that any existing pattems of degradation would have been detected and the licensee's coverage provides reasonable assurance of structuralintegrity of the subject components.

l

4 Based on the impracticality of meeting the Code-coverage requirements for the subject examination, and the reasonable assurance provided by the examination that was performed, the staff determined that relief is granted pursuant to 10 CFR 50.55a(g)(6)(i).

Reauest for Relief No. RR-2.1.12: ASME Code,Section XI, Examination Category B-H, item B8.10 requires a volumetric or surface examination, as applicable, of 100 percent of the length of RPV integral attachment welds during each inspection interval as defined by Figures IWB-2500-13, -14, and -15. Pursuant to 10 CFR 50.55a(g)(6)(i), the licensee requested relief from the surface examination requirements defined in ASME Section XI, Figure IWB-2500-15, for four RPV stabilizer brackets for Hatch, Unit 1, and six RPV stabilizer brackets for Hatch, Unit -2.

~

l The Code requires 100 percent ultrasonic or surface examination of the RPV integrally welded attachments during each inspection interval. However, the examination is limited by RPV design and restricted access between the bracket and the shield wall. Therefore, the Code-required examination is impractical for Hatch, Unit 1 and Unit 2 RPV stabilizer brackets.

To achieve the Code-required examination coverage, the RPVs would have to be redesigned and modified. Imposition of this requirement would cause a considerable burden on the licensee.

The licensee has completed a significant portion (30-35 percent for Unit 1; 65-70 percent for Unit 2) of the Code-required surface examination. Therefore, any existing pattems of degradation would have been detected and reasonable assurance of structural integrity has been provided.

The staff determined that meeting the Code-coverage requirements for the subject examination is impractical, and the licensee's attemative of taking credit for examinations that were performed, provides reasonable assurance of structuralintegrity of the subject components.

The staff has determined that relief is granted pursuant to 10 CFR 50.55a(g)(6)(i).

Reauest for Relief No. RR-2.1.13

ASME Code,Section XI, Examination Category B-A, l Item B1.40 requires volumetric and surface examinations of the RPV head-to-flange welds during each inspection interval as defined by Figure IWB-2500-5. Pursuant to 10 CFR 50.55a(g)(6)(i), the licensee requested relief from meeting the volumetric examination coverage requirements for the RPV head-to-flange welds.

l The Code requires ultrasonic and surface examination of the RPV head-to-flange welds.

However, the ultrasonic examination volume is limited by reactor vessel geometry and weld configuration. Therefore, examination of the Code-required volume is impractical for the Hatch, Units 1 and 2, RPV head-to-flange welds. To achieve the Code-required examination coverage, the RPV head would have to be redesigned and modifie;d. Imposition of this requirement would cause a considerable burden on the licensee.

The licensee has completed a composite coverage of approximately 84 percent of the Code-required volume for RPV head-to-flange welds. Therefore, any existing pattems of degradation would have been detected and the licensee's coverage of 84 percent provides reasonable assurance of structuralintegrity of the subject componen"s.

The staff determined that based on the impracticality of meeting the Code-coverage requirements and that examinations that were performed provide reasonable assurance that the subject components have structural integrity, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i).

Reauest for Relief No. RR-2.1.14 (Unit 2 oniv): ASME Code,Section XI, Examination Category C-G, item C6.10 requires a 100 percent surface examination of Class 2 pump casing welds during each inspection interval as defined by Figure IWC-2500-8. Pursuant to 10 CFR 50.55a(g)(6)(i), the licensee requested relief from meeting the surface examination coverage ,

requirements for the residual heat removal (RHR) pump inlet nozzle-to-casing weld and core j spray (CS) pump inlet nozzle-to-vessel weld for Hatch, Unit 2.

The Code requires surface examination of Class 2 pump casing welds. However, access to the I Hatch, Unit 2, RHR and CS pump inlet nozzle-to-casing welds is restricted by the surrounding concrete support structure. Therefore, the Code-required surface examination is impractical to perform to the extent required by the Code. To achieve the Code-required examination  ;

coverage, the pumps and their surrounding support structure would have to be redesigned and modified. Imposition of this requirement would cause a considerable burden on the licensee. {

i i

The licensee has completed a s'ignificant portion (60 percent) of the Code-required surface examination br the subject Class 2 pump inlet nozzle-to-casing welds. In addition,100 percent of the outlet nozzle-to-vessel welds have been completed. Therefore, the staff determined that any existing pattems of degradation would have been detected and the licensee's completed examinations provide reasonable assurar,ce of structuralintegrity of the subject components.

Furthermore, the staff determined that based on the impracticality of meeting the Code-coverage requirements and that examinations that were performed provide reasonable assurance that the subject components have structural integrity, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i).

3.0 CONCLUSION

The staff has evaluated the licensee's submittals and concludes that certain inservice examinations cannot be performed to the extent required by the Code at Hatch, Units 1 and 2.

In Requests for Relief Nos. RR-2.1.3 (Rev.1), RR-2.1.11, RR-2.1.12, RR-2.1.13, and -

RR-2.1.14, the licensee has provided information to support the determination that the Code examination coverage requirements are impractical. It is also concluded that reasonable assurance of component structuralintegrity has been provided by the examinations that have been performed. Therefore, the requirements of the Code are impractical and relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for Requests for Relief Nos. RR-2.1.3 (Rev.1). RR-2.1.11, RR-2.1.12, RR-2.1.13, and RR-2.1.14.

l The reliefs granted are authorized by law and will not endanger life or property or the common l

defense and security, and are otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

i Principal Contributor: T. McLellan  !

l Date: July 30, 1998 j l

l

)

i TECHNICAL LETTER REPORT ON SECOND 10-YEAR INTERVAL INSERVICE INSPECTION REQUESTS FOR RELIEF j EDE \

SOUTHERN NUCLEAR OPERATING COMPANY EDWIN 1. HATCH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NUMBERS: 50-321 AND 50-366

1.0 INTRODUCTION

By letter dated December 17,1996, Georgia Power Company submitted Relief Requests RR-18 through RR-22 for the Edwin 1. Hatch Nuclear Plant, Units 1 and 2, for closeout of the second 10-year interval examinations as well as the Third 10-Year Interval lSI Program update. By letter dated August 1,1997, NRC requested additionalinformation regarding these relief requests. By letter dated August 29,1997, Southem Nuclear Operating Company (SNC) withdrew RR-18 through RR-22 for the third interval and committed to submit new relief requests to close out the second interval. By letter dated October 6,1997, SNC, submitted one relief request revision and four new relief requests for the second 10-year inservice inspection (ISI) interval. The Idaho National Engineering and Environmental Laboratory (INEEL) staff has evaluated the subject requests for relief in the following section.

2.0 EVALUATION The information provided by the licensee in support of these requests for relief from Code requirements has been evaluated and the bases for disposition are documented below.

The Code of record for the Hatch Nuclear Plant, Units 1 and 2, second 10-year ISI intervalis the 1980 Edition, Winter 1981 Addenda, of Section XI of the ASME Boiler and Pressure Vessel Code.

2.1 Raouest for Relief No. RR-2.1.3 (Rev.11 Ermmination Cateoorv B-D. Item B3.90. RPV

, Nozzle-to-Vessel Welds Code Requirement Section XI, Examination Category B-D, item B3.90 requires 100%

volumetric examination of all reactor pressure vessel nozzle-to-vessel welds as defined by Figure IWB-2500-7. Additionally,Section XI, Paragraph IWA-2232 requires ultrasonic examination of vessels greater than 2 inch thickness in accordance with the ASME Code,Section V, Article 4. Article 4 requires two directional coverage when practical.

Licensee's Request for Rehef. Pursuant to 10 CFR 55.55a(g)(6)(i), the licensee l

requested relief from performing the volumetric examination to the extent required by the j Code for the following RPV nozzle-to-vessel welds.

l Enclosure 2

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1 Unit 1 ~ 4" ^ 9 " Unit' 2 R J '

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M s p ";: Q '.3 WA q V , , . . , </ % Compositej y&L y ,y Composite

_: " Des 4h. a * - WeMNumbers Coverage J Wald Numbers - Coverage Recirculation Outlet Nozzle N1A,B 60 % 2N1A,B 80 %

Recirculation inlet Nozzle N2A-H, J-K 35% 2N2A-H, J-K 60 %

Main Steam Nozzle N3A,B,C 75 % 2N3A-D 60 %

N3D 45 %

Feedwater Nozzle N4A-D 45 % 2N4A-D 60 %

Core Spray Nozzle NSA,B 45% 2N5A,B 65%

Head Spray Nozzle N6A,B 45% 2N6A,B 45 %

Head Vent Nozzle N7 60 % 2N7 50 %

Jet Pump Instrument Nozzle N8A,B 55 % 2N8A,B 55 %

CRD Inlet Nozzle ,W9 50 % 2N9 50 %

Licensee's Prono'ed Altemative Examina' ion:

None. Examination was performed to the extent practical.

Licensee's Basis for Reauestino Relief (as stated)h

'The curvature of the nozzles generally prohibited Code examinations of the nozzle-to-vessel welds from the nozzle side. When attempting to examine the welds from the nozzle side, the complex curvature cf the nozzle mis-oriented the sound beam such that proper coverage could not be obtained; therefore, only one directional coverage from the vessel (or head) side was feasible.

"One directional coverage from the vessol side was also limited since complete coverage would require scanning from the vessel side onto the weld crown, and then onto a portion of the nozzle. However, as addressed above, once the curvature of the nozzle was reached, the sound beam was mis-oriented. In most cases, Unit I has barrel type nozzles with the weld located in the curved blend radius, while Unit 2 has flange type nozzles with the weld located in the vessel shell area. Therefore, Unit 2 welds could generally be examined from the vessel shell area, from the weld crown, and possibly from a small portion of the nozzle, while the Unit I welds could generally be examined from the vessel shell area and possibly a portion of the weld. Examples of 45.and 60 degree scan Figures furnished with the licensee's submittal are not included in this report.

t

coverage for a typical flange type nozzle are shown in Figures 21 and 22, while examples of 45 and 60 degree scan coverage for a typical barrel type nozzle ure shown in Figures 23 and 24. Specific geometry and limitations for each nozzle are listed below.

• lt should be noted that the coverage shown for each nozzle is a conservative estimate, while actual coverage may be higher. This is due to the fact that all accessible areas were generally scanned by the examiners; however, for the purpose of defining coverage, results obtained from scanning on curved surfaces were not included. It should also be noted that these limitations apply to manual techniques or automated systems. The inspection vendor has also verified that the coverage shown was typical of coverage seen at other domestic BWRs.

" Composite coverage in this relief request was calculated using the average coverage of four scans: (1) shell side coverage for reflectors oriented parallel to the weld seam, (2) nozzle side coverage for reflectors oriented parallel to the weld seam, (3) clockwise coverage on the weld crown for reflectors oriented transverse to the weld seem, and (4) counter-clockwise coverage on the weld crown for reflectors oriented transverse to the weld seam. (it should be noted that all utilities do not calculate coverage using the same methodology; therefore, percent of Code coverage reported to the NRC for the same actLal coverage, may vary from utility to utility).

" UNIT 1

• N1 A, B - Recirculation Outlet Nozzle-To-Vessel Welds - For this nozzle configuration, the weld adjoins the curved, blend radius of the nozzle; therefore, ultrasonic scanning could only be performed on the RPV vessel and the weld. Additionally, further limitations occurred due to the proximity of the welded insulation ring. A composite coverage of approximately 60% of the required examination volume was obtained. (See Figures 1 and 3).

'N2A-H, J-K - Recirculation inlet Nozzle-To-Vessel Welds - For this nozzle configuration, the weld is located in the curved, blend radius of the nozzle; therefore, ultrasonic scanning could only be performed on the RPV vessel up to the point where the curvature starts. Additionally, severe limitations existed due to the welded insulation ring that is located just above the nozzles. A composite coverage of approximately 35% of the required examination volume was obtained. (See Figures 1,2, and 4).

1 "N3A, B, C - Main Steam Nozzle-To-Vessel Welds - For this nozzle configuration, the j geometry is similar to that of the main steam nozzles for Unit 2, in that, the weld is  ;

located such that ultrasonic scanning could be performed on the RPV vessel, on the l weld, and on a small portion of the nozzle. A composite coverage of approximately 75%

l of the required examination volume was obtained. Note: Even though there are differences (e.g., extent of cladding), Figure 10 which depicts the Unit 2 nozzles can also be used to adequately depict the geometry for this nozzle. (Also see Figure 1). .

"N3D - Main Steam Nozzle-To-Vessel Wolds - For this nozzle configuration, the weld is located in the curved, blend radius of the nozzle; therefore, ultrasonic scanning could only l

4 I

1

. l l be performed on the RPV up to the point where the curvature starts. A composite l coverage of approximately 45% of the required examination volume was obtained. (See

{ Figures 1 and 5).

l l *N4A D - Feedwater Nonle-To-Vessel Wolds - For this nonle configuration, the weld is i

located in the curved, blend radius of the nonle; therefore, ultrasonic scanning could only be performed on the RPV vessel up to the point where the curvature starts. A composite coverage of approximately 45% of the required examination volume was obtained. (See Figures 1 and 6).

'N5A, B - Core Spray Nonie-To-Vessel Welds - For this nonle configuration, the weld is located in the curved, blend radius of the nonle; therefore, ultrasonic scanning could only be performed on the RPV vessel up to the point where the curvature starts. A composite coverage .of approximately 45% of the required examination volume was obtained. (See Figures 1 and 7).

l

• N6A, B and N7 - RPV Head Nonles - An evaluation of the nonle configuration shows that these small nonles located on the RPV head have a very short radius. With the N6A, B configuration, scanning could only be performed on the head and for the N7 nonle configuration, scanning could only be performed on the head and a portion of the weld. A composite coverage of approximately 45% of the required examination volume was obtained for the N6A, B noules and 50% for the N7 nonle. (See Figures 1,13 and 14).

'N8A-B - Jet Pump instrument Nonies - An evaluation of the configuration shows that the nonle weld is adjacent to a sharply curved radius. With this configuration, scanning could only be performed on the shell and the weld. A composite coverage of approximately 55% of the required examination volume was obtained. (See Figures 1 and 15).

• N9 - CRD Nonie-To-Vessel - For this nonle configuration, the weld is located in the i curved blend radius, such that, ultrasonic scanning could only be performed on the RPV l and a portion of the weld. A composite coverage of approximately 50% of the required examination volume was obtained. (See Figures 1 and 16).

UNIT 2

• 2N1 A, B - Recirculation Outlet Nonie-To-Vessel Wolds - For this nonle configuration, the weld is located such that ultrasonic scanning could be performed on the RPV vessel, on the weld, and on a portion of the nonie. A composite coverage of approximately 80% of the required examination volume was obtained. (See Figure 8).

• 2N2A-H, J-K - Recirculation inlet Nonle-To-Vessel Welds - For this nonle configuration, the weld is located such that ultrasonic scanning could be performed on the

. RPV vessel and on the weld. A composite coverage of approximately 60% of the required examination volume was obtained. (See Figure g ). (Note: The welded insulation ring is not present on Unit 2).

)

l t "2N3A-D - Main Steam Nonle-To-Vessel Welds - For this nozzle configuration, the weld is located such that ultrasonic scanning could be performed on the RPV vessel and on the weld. A composite coverage of approximately 60% of the required examination j volume was obtained. (See Figure 10).

"2N4A-D - Feedwater Nonie-To-Vessel Welds - For this nozzle configuration, the weld {

l is located such that u!trasonic scanning could be performed on the RPV vessel and on

{

l the weld. A composite coverage of approximately 60% of the required examination I volume was obtained. (See Figure 11). {

I "2N5A, B - Core Spray Nozzle-To-Vessel Wolds - For this nozzle configuration, the  !

weld is located such that ultrasonic scanning could be performed on the RPV vessel and I the weld. A composite coverage of approximately 65% of the required examination vohame was obtained. (See Figure 12). <

l "2N6A, B and 2N7 - RPV Head Nonles - An evaluation of the nozzle configuration shows that these small nozzles located on the RPV head have a very short radius. With the 2N6A, B configuration, scanning could only be performed on the head and for the 2N7 nozzle configuration, scanning could only be performed on the head and a portion of the weld. A composite coverage of approximately 45% was obtained foi the 2N6A, B )

nozzles and 50% for the 2N7 nozzle. (See Figures 17 and 18).

l l

"2N8A, B - Jet Pump instrument Nozzles - An evaluation of the configuration shows that the nozzle weld is adjacent to a sharply curved radius. Wdh this configuration, scanning could only be performed on the shell and the weld. A composite coverage of approximately 55% of the required examination volume was obtained. (See Figure ig).

"2N9 - CRD Nozzle-To-Vessel - For this nozzle configuration, the weld is located in the curved blend radius, such that ultrasonic scanning could only be performed on the RPV up to the point where the curvature begins. A composite coverage of approximately 50%

of the required examination volume was obtained. (See Figure 20).

" Cracking that initiates from the ID (thermally induced cracking, stress-corrosion cracking, etc.) is the primary concem for these welds. While coverage was limited due to the design of the nozzles, : overage (from at least one angle) was obtainable for the lower portion of the examination volume. Therefore, there is a reasonable degree of confident.e that loss of structural integrity in these welds could have been detected.

"Various techniques were evaluated such as using additional angles and bouncing the ultrasound off of the clad surface; however, none were proven to be of practical use.

SNC has performed the ultrasonic to the extent practical, given the complex geometry of these nozzles. To meet the Code coverage requirements would require extensive prefabrication of the RPV, which is considered by SNC to be completely impractical.

Denial of this relief request would cause an excessive burden upon Southern Nuclear Operating Company, since i+ is impractical to meet the Code coverage requirements with f

i presently-developed techniques, j l  ! 1 1

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ a

t "The volumetric examination of the lower portion of the examination volume provides reasonable assurance that inservice flaws exceeding acceptance standards have not j developed in the subject weld or that they would have been detected and dispositioned prior to the return of the reactor vessel to service. Therefore, an acceptable level of quality and safety will be maintained and public health and safety will not be endangered by approving this relief request. The request for relief is being sought pursuant to the requirements of 10CFR50.55a(g)(6)(i)."

Evaluation' The Code requires 100% ultrasonic examination of nonie-to-vessel welds l during each inspection interval. However, as explained in the licensee's submittal, the l ' nonles' geometric configurations limit the cumulative ultrasonic coverage for the subject i nonle-to-vessel welds to between 35% and 80% of the Code-required volume, as shown

in Table 1. Additionally, the Code-required two-directional coverage of the examination voluma could not be obtained due to the complex curvature of the nonle and only one directional coverage from the vessel (or head) side was feasible. Therefore, the 100%

l volumetric examination coverage is impractical for the subject RPV nonle-to-vessel welds. To gain access for the Code-required examination, the RPV would have to be redesigned and modified. Imposition of this requirement would cause a considerable i burden on the licensee.

The most probable failure mechanism for the subject RPV nonie-to-vessel welds  !

involves a radial flaw propagating from the vessel ID surface. The limited one-directional examinations performed have provided coverage of the portion of the weld volume l

nearest the vessel ID, therefore existing flaws would have been detected.

The licensee has ultrasonically examined a cumulative volume of approximately 35% to 80% of respective RPV nonle-to-vessel welds. These examinations, in addition to the visual examination of the vessel ID, provides reasonable assurance that any pattems of dyradation would have been detected.

Based on the impracticality of meeting the Code requirements for the subject welds and the reasonable assurance provided by the examinations completed on the ID of the RPV, it is recommended that relief be granted pursuant to 10 CFR 55.55a(g)(6)(i).

2.2 Reauest for Relief No. RR-2.1.11. Examination Cateoorv B-G-1. Item B6.40. RPV Threaded Flance Licaments. (Unit 1 only) l Code Requirement Section XI, Examination Category B-G-1, item B6.40 requires volumetric examination of the threads in the reactor pressure vessel flange during each inspection interval as defined by Figure IWB-2500-12.

Licensee's Request for Relief. Pursuant to 10 CFR 55.55a(g)(6)(i), the licensee requested relief from the volumetric examination coverage requirements defined in ASME l l Section XI, Figure IWB-2500-12, for the RPV flange ligaments for Hatch Unit 1. j

Licensee's Prooosed Alternative Examination:

None. The ultrasonic examination was performed to the extent practical.

Licensee's Basis for Reauestina Relief (as stated):

" Figure IWB-2500-12 shows that the radius of the required examination volume is defined as one inch from the inside surface of the stud hole, or if threaded bushings are used, one inch from the bushing. Hatch Unit i has threaded bushings while Unit 2 does not; therefore, the examination volume extends radially farther out into the flange for Unit 1.

This increase in the radial dimension for Unit 1 created an interference with the )-Ring grooves that are located on the face of the flange, both inside and outside the bolting ring. These grooves prevented the examination of the outer portion of the examination volume. Approximately 75% of the volume can be examined, including all of the volume adjacent to the threads.

"This ultrasonic examination was performed, to the maximum extent practical, in order to detect cracking initiating from the threaded area of the flange. While coverage of the outer 25% portion of the examination volume could not be obtained, complete examination of the area in which cracking would initiate was obtained. Meeting the Code coverage requirements would require extensive prefabrication of the RPV, which is  ;

considered by SNC to be completely impractical. Denial of this relief request would, l therefore, cause an excessive burden upon Southem Nuclear Operating Company.

"The volumetric examination of 75% of the examination volume will provide reasonable assurance that inservice flaws exceeding acceptance standards have not developed in the subject weld or that they would have been detected and dispositioned prior to the retum of the reactor vessel to service. Therefore, an acceptable level of quality and safety will continue to be maintained and public health and safety will not be endangered by approving this relief request. The request for relief is being sought pursuant to the requirements of 10 CFR 50.55a(g)(6)(i)."

Evaluation The Code requires that the ultrasonic examination of the RPV flange threads

! includes the volume one inch from the threaded bushings. However, for the RPV flange ligaments for Hatch Unit 1 the ultrasonic examination is limited by o-ring grooves located both inside and outside of the bolting ring. Therefore, examination of the Code-required volume is impractical for the Hatch Unit 1 RPV flange threads. To achieve the Code-j required examination coverage, the RPV would have to be redesigned and modified.

! Imposition of this requirement would cause a cor,siderable burden on the licensee.

1 The licensee has completed a significant portion (75%) of the Code-required volumetric examination of the RPV flange threaded ligaments, including all of the volume adjacent to the threaded bushings. Therefore, any existing pattems of degradation would have been detected and reasonable assurance of structural integrity has been provided.

Based on the impracticality of meeting the Code coverage requirements for the subject examination, and the reasonable assurance provided by the examination that was performed, it is recommended that relief be granted pursuant to 10 CFR 55.55a(g)(6)(i).

2.3 Raouest for Relief No. RR-2.1.12. Examination Cateaorv B-H. Item B8.10. RPV Intearally Welded Attachments Code Requirement: Section XI, Examination Category B-H, item B8.10 requires a volumetric or suiface examination, as applicable, of 100% of the length of RPV integral attachment welds during each inspection interval as defined by Figures IWB-2500-13, -

14, and -15.

Licensee's Reauest for Relief: Pursuant to 10 CFR 55.55a(g)(6)(i), the licensee requested relief from the surface examination requirements defined in ASME Section XI, Figure IWB-2500-15, for four RPV Stabilizer Brackets for Hatch Unit 1 and six RPV Stabilizer Brackets for Hatch Unit 2.

Licensee's Proposed Altemative Framination:

None. The examinations were performed to the extent practical. I Licensee's Basis for Reauestina Relief (as stated):

"As described in the FSAR, ' vessel stabilizers connect the reactor vessel to the top of the shield wall surrounding the vessel. Each vessel stabilizer assembly consists of a l stabilizer rod, threaded at the ends; springs, washers, nuts, plates and a bumper l

bracket'. The brackets for Hatch Units 1 and 2 were installed on the reactor vessel at the time of vessel fabrication. The vessel was set into place and the shield wall constructed such that the bottom of the brackets were only about 2 to 6 inches above the top of the shield wall.

" Hatch Unit 1 has a ' Tee' shaped bracket stabilizer bracket welded to the RPV as shown in Figure 18. This design prevents examination of the weld located on the ends of the bracket between the ' ears' of the tee and the RPV wall. Additionally, the bottom of the bracket cannot be examined due to the limited distance between the bracket and the l

shield wall. With such a small opening, especially considering the additional interference from other components of the stabilizer assembly and vessel insulation, insufficient space i exists to perform the required examinations. Approximately 30 to 35% of the weld can be examined on each Unit 1 bracket.

l " Hatch Unit 2 has a more conventbnal ' lug type' design, as shown in Figure 22, that ,

j extends approximately 15" from the RPV surface. With this extension and the above

! described interference, the bottom portion of the weld cannot be accessed for l

l l l

Figures furnished with the licensee's submittal are not included in this report.

.g.

examination. The top of the weld and both sides of the weld can be examined, resulting in a coverage of approximately 65 to 70%.

"The Hatch FSARs describes the RPV stabilizers as bein0 designed to :(1) permit radial and axial vessel expansion, (2) limit horizontal vibration, and (3) resist seismic and jet reaction forces. There are minimal forces acting on these brackets during normal operation; therefore, there is low probability that these welds would ever experience cracking during normal operation and therefore, would be fully capable of handling LOCA (jet force reaction and seismic) loads.

"SNC has performed the surface examinations to the extent practical, given the geometry of the component. To meet the Code requirements would require extensive prefabrication of these supports, which is considered by SNC to be completely impractical. Denial of this relief request would, therefore, cause: ;n excessive burden upon Southem Nuclear Operating Company since it is impractical to meet the Code requirements.

"The complete examination of the top of the bracket combined with the low probability of cracking, should prov!de reasonabic assurance that inservice flaws of such size that they would challenge the structuralintegrity of the bracket welds are not present. Therefore, an acceptable level of quality and safety will be maintained and public health and safety will not be endangered by approving this relief request. The request for relief is being sought pursuant to the requirements of 10CFR50.55a(g)(6)(i).

Evaluation The Code requires 100% ultrasonic or surface examination of the RPV integrally welded attachments during each inspection interval. However, the examination is limited by RPV design and restricted access between the bracket and the shield wall.

Therefore, the Code-required examination is impractical for the Hatch Unit 1 and 2 RPV stabilizer brackets. To achieve the Code-required examination coverage, the RPVs would have to be redesigned and modified. Imposition of this requirement would cause a considerable burden on the licensee.

The licensee has completed a significant portion (30-35% for Unit 1; 65-70% for Unit 2) of the Code-required surface examination. Therefore, any exisiing pattems of degradation would have been detected and reasonable assurance of structural integrity has been provided.

Based on the impracticality of meeting the Code coverage requirements for the subject examination, and the reasonable assurance provided by the examination that was performed, it is recommended that relief be granted pursuant to 10 CFR 55.55a(g)(6)(i).

l I

b , - - . . . . , _ _ . _ . - - - - - . -

2.4 Reauest for Relief No. RR-2.1.13. Framination Cateoorv B-A. Item B1.40. RPV Head-To-Flange Welds Code Requirement Section XI, Examination Category B-A, item B1.40 requires volumetric and surface examinations of the reactor pressure vessel head-to-flange welds during each inspection interval as defined by Figure IWB 2500-5.

Licensee's Reauest for Rehef. Pursuant to 10 CFR 55.55a(g)(6)(i), the licensee requested relief from meeting the volumetric examination coverage requirements for the RPV head-to-flange welds.

Licensee's Pronosed Alternative Examination-None. The ultrasonic examination was performed to the extent prcatical.

Licensee's Basis for Reauestino Relief (as stated):

"As shown in Figure 18, head-to-flange welds 1HC-2 and 2HC-2 are located such that utrasonic scanning could only be performed for about six inches on either side of the respective weld. Past the six inches, on the dome side, there is a taper that joins two different thicknesses together, while on the flange side there is a strong curvature.

Outside the six-inch scanning area, on each side of these welds, meaningful examination was not possible due to the configuration. For this configuration, a composite coverage of approximately 84% of the required volume was obtained.

'SNC has performed the ultrasonic examination to the extent practical, given the 1 geometry of the weld configuration. To meet the Code requirements would require extensive prefabrication of the RPV head, which is considered by SNC to be completely impractical. Denial of this relief request would, therefore, cause an excessive burden upon Southem Nuclear Operating Company because it is impractical to meet the Code required volume for all of the angles. ,

I "The ultrasonic examination of the volume with the 0-degree,45-degree, and partial 60- ]

degree scans will provide reasonable assurance that inservice flaws exceeding j acceptance standards have not developed or that they would have been detected and dispositioned prior to the retum of the reactor vessel to service. An acceptable level of quality and safety will continue to be maintained and public health and safety will not be endangered; therefore, SNC requests approval of this request for relief pursuant to the requirements of 10 CFR 50.55a(g)(6)(i)."

Evaluation The Code requires ultrasonic and surface examination of the RPV head-to-flange welds. However, the ultrasonic examination volume is limned by reactor vessel geometry and weld configuration. Therefore, examination of the Code-required volume is impractical for the Hatch, Units 1 and 2, RPV head-to-flange welds. To achieve the Figures supplied in the licensee's submittal are not included in this report.

Code-required examination coverage, the RPV head would have to be redesigned and modified. Imposition of this requirement would cause a considerable burden on the licensee.

The licensee has comp;eted a composite coverage of approximately 84% of the Code-required volume for RPV head-to-flange welds. Therefore, any existing pattoms of degradation would have been detected and reasonable assurance of structural integrity has been provided. 4 Based on the impracticality of meeting the Code coverage requirements and the reasonable assurance provided by the examination that was performed, it is recommended that relief be granted pursuant to 10 CFR 55.55a(g)(6)(i).

2.5 Reauest for Relief No. RR-2.1.14. Fvamination Cateoorv C-G. Item C6.10. 0l=== 2 Pumo inlet Nozzle-To-Casina Welds (Unit 2 only)

Code Requirement Section XI, Examination Category C-G, item C6.10 requires a 100%

surface examination of Class 2 pump casing welds during each inspection interval as defined by Figure IWC-2500-8.

Licensee's Reauest for Relief: Pursuant to 10 CFR 55.55a(g)(6)(i), the !icensee requested relief from meeting the surface examination coverage requirements for the Residual Heat Removal (RHR) pump inlet nozzle-to-casing weld and Core Spray (CS) pump inlet nozzle-to-vessel weld for Hatch Unit 2.

Licensee's Prooosed Altemative ExaminatiQD:

None. The surface examination was performed to the extent practical.

Licensee's Basis for Reauestina Relief (as stated):

" Details listed below are for the RHR pumps, however, the limitations are essentially the same for the CS pumps, since the design is very similar.

"These pumps are vertical pumps that are mounted in concrete with most of the pump exterior surface being completely inaccessible. The outlet nozzle is located near the top of the pump, so there is no access problem for this nozzle: however, the 24" diameter inlet nozzle is mounted on the side of the pump. Access was provided to the inlet nozzle and the incoming suction line by construction of an opening in the concrete at the side of l the pump. This opening allows full access above and below the nozzle; however, the sides of the opening are close to the nozzle, resulting in limited access to the sides of the l

weld.

l "Approximately 60% (23" on the top and 23" on the bottom) of the total required examination area was completely examined using the surface examination technique.

Due to the above described access restrictions, the remaining 40% at the sides of the weld could not be examined with surface examination method.

f

" Denial of this relief request would cause an excessive burden upon Southem Nuclear Operating Company because it has been demonstrated that it is impractical to meet the Code requirements. SNC has performed surface examinations on these welds to the extent practical, given the configuration in which these pumps were installed. To meet

)

the Code requirements would require extensive prefabrication of the RHR pumps and/or '

mountings, which is considered by SNC to be completely impractical.

t

" Surface examination of 60% of the required area should provide a reasonable assurance I that inservice flaws, of such size that they would challenge the structural integrity of the ,

l weld, were not present. Therefore, an acceptable level of quality and safety will be j l meintained and public health and safety will not be endangered by approving this relief l l request. This request for relief is being sought pursuant to the requirements of 10 CFR l 50.55a(g)(6)(i)."

I Evaluation: The Code requires surface examination of Class 2 pump casing welds.

However, access to the Hatch Unit 2 RHR and CS pump inlet nozzle-to-casing welds is restricted by the surrt 1 ding concrete support structure. Therefore, the Code-required surface examination is impractical to perform to the extent required by the Code. To achieve the Code-required examination coverage, the pumps and their surrounding support structure would have to be redesigned and modified. Imposition of this requirement would cause a considerable burden on the licensee.

The licensee has completed a significant portion (60%) of the Code-required surface examination for the subject Class 2 pump inlet nozzle-to-casing welds. In addition,100%

of the outlet nozzle-to-vessel welds have been completed. Therefore, any existing pattems of degradation would have been detected and reasonable assurance of structural integrity has been provided.

Based on the impracticality of meeting the Code coverage requirements and the reasonable assurance provided by the examinations that were performed, it is recommended that relief be granted pursuant to 10 CFR 55.55a(g)(6)(i).

3.0 CONCLUSION

The INEEL staff has evaluated the licensee's submittal and concludes that certain inservice examinations cannot be performed to the extent required by the Code at Hatch Nuclear Plant, Units 1 and 2. In Requests for Relief Nos. RR-2.1.3 (Rev.1), RR-2.1.11, RR-2.1.12, RR-2.1.13, and RR-2.1.14, the licensee has provided information to support the determination that the Code examination coverage requ;roments are impractical. It is also concluded that reasonable assurance of component structural integrity has been provided by the examinations that have been performed. Therefore, it is recommended that relief be granted pursuant to 10 CFR 55.55a(g)(6)(i).

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