ML20198R477
| ML20198R477 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/13/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20198R465 | List: |
| References | |
| NUDOCS 9801230328 | |
| Download: ML20198R477 (13) | |
Text
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- umisOsTATas g NUCLEAR REGULATORY COMMISSION
- WADMINGTON. D.C. ESASHOM SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN REQUESTS FOR RELIEF TOLEDO EDISON COMPANY l CENTERIOR SERVICE COMPANY j AND THE CLEVELAND ELECTRIC ILLUMINATING COMPANY DAVIS-BESSE NUCLEAR POWER STATION. UNIT I 1
DOCKET NO. 50-346 l
1.0 B.it. M 1QN The. Technical Specifications for the Davis-Besse Nuclear Power Station state that the inservice inspection (ISI) of the Ainerican Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components shall be parfoimd in accordance with Section XI of the ASME Boiler and Pressure Vessel Coo's and applicable addenda as-required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Ccamission.
Section 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if i) the proposed alternatives would provide an acceptable level of quality and(safety, 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(p)(4), ASME Code Class 1, 2, and 3 components $
(including supports) shall meet the requirements, except the design and access l provisions and the preservice-examination requirements, set forth in the ASME ;
Code,Section XI, ."F.ules for Inservice . Inspection of Nuclear Pvwer Plant :
Components," to the extent practical within the limitations of design,
- geometry, and materials of constrt.ction 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 ASME Code,Section XI, for the - -
Davis-Besse Nuclear Power Station second 10-year (ISI) interval is the 1986 i
- edition. The components (including supports) may meet the requirements set h
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- forth in subsequent editions and addenda _of the ASME Code incorporated by !
reference in 10 CFR 50.55a(b) subject to the limitations and modifications !
i lhted therein and_ subject to Commission approval. !
)
. Pursuant to 10.CFR 50.55a(g)(5), if the licensees determine that conformance with an examination requirement of Section XI of the ASME Code is not i practical for its facility, information shall be submitted to the Commission ,
'in support of that determination and a request made for relief from the ASME- ;
Code requirement. 'After eyaluation of the determination, pursuant to i 10 CFR 50.55a(g)(6)(1), the Commission may grant relief and may impose: l alternative requ'rements that are determined to be-authorized by law, will not i endanger life, property, or the common defense and security, and are otherwise !
in the public interest, giving due consideration to the burden upon the l licencess that could result if the requirements were imposed. ;
By letter dated March 7,_1997, .as supplemented November 18, 1997, the Toledo :
Edison Company, Centerior Service Company,._and The Cleveland r'--tric Illuminating Company, the licensees for the Davis-Besse Nuc14..r ower Station, :l submitted to the NRC requests for relief from the examination requirement of '
the applicable ASME Code,Section XI, for-the second ISI interval -
examinations. The NRC staff has reviewed and evaluated Re19f Request Nos.
RR-A13. RR-A14, RR-A15, and RR-88 for the second 10-year ISI interval at ,
' Davis-Besse. !
2.0 RELIEF REQUEST NO. RR-A13 :
2.1 Comnonent Descrintion Longitudinal Welds'in Class 1 and 2 Piping - Request for Approval to use Code Case N-524: l 88 Class 1 Longitudinal Welds -
77 Class 2 Longitudinal Welds ;
1 2.2 ASME Code Class ASME Section XI, Class 1 and 2
-2.3 LASME Examination Raoui, .. ts. ASME Section XI. 1986 Edition
~
' Code:lten B9.12, Table IWB-2500, requires.a surface.and volumetric ,
examination of at least a pipe diameter length,-but.nct more than 12-inches; t Lof each longitudinal weld intersecting the circusferential welds required to be examined by Examination Categories B-F and B-J.- -
j
- Code Item' C5.52,L Table IWC-2500, requires 'a surface and volumetric - -
- examination of the longitudinal weld for- a. length of 2.5t at the intersecting - *
. circumferential: weld.- ,
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Code Case N-524 provides altern&tive requirements for the surface and vo5 metric examination of longitudinal piping welds specified in Examination Categories B-J, C-F6 and C-F-2. This code case recognizes that the.
longitudinal piping welds are not made in the field, but are made and examined by the piping manufacturer under controlled conditions and procedures. This code case further recognizes that the most likely area where defects may occur--
is at the intersection of the longitudinal and circumferential welds. As this area is examined as part of the circumferential weld examination, additional examination of the longitudinal weld outside this area is unnecessary to ensure weld quality is maintained.
Implementation of the Code Case N-524 will also reduce the labor-hours and personnel exposures necessary to perform the examinations by eliminating unnecessary examinations.
Code Case N 524 has been approved by the ASME Soffer and Pressure vessel Code Committee and the Board on Nuclear Codes and Standards as an acceptable alternative to the rules of the ASME Soller and Frenure Vessel Code,Section XI.
2.5 Alternative Examination fas stated)
Examination of longitudinal welds will be performed in accordance with Code Case N-524. When Code Case N-524 is ap> roved in Regulatory Guide 1.147, any additional. limitations recommended by t1e NRC staff will also be incorporated.
2.6 Evkidation The ASME Section XI Code (1986 Edition) requires one pipe diameter in length, but no more than 12 inches, be examined for Class I longitudinal piping welds.
Class 2 longitudinal piping welds are required to be examined for a length of 2.5t, where t is the thickness of the weld. These lengths of-weld are usured from the. intersection of the circumferential weld and longitudinal en d. The licensees' proposed alternative, Code Case N-524, limits the
%,1umetric and surface examination requirements of the longitudinal weld to the volume or area contained within the examination requirements of the intersecting circumferential weld.
' Longitudinal welds are produced during the manufacturing process of the
_ piping, not in the field as is the case for circumferential welds. The Code
.contains requirements =on characteristics and performance of materials and products, and specifies the examination requinoments during the manufacturing of. the . subject longitudinal piping welds.
In addition, there are material, chemical, and tensile strength requirements in the Code. .The manufacturing process that is specified by the Code provides 1
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l assurance of the structural integrity of the longitudinal welds at the time the piping is manufactured. l The preservice examination &nd initial inservice examinations have )rovided assurance of the structural integrity of the longitudinal welds. T ie :
I experience in the United States has been that pipes with shop-welded longitudinal seams have not ex>erienced degradation that would warrant continued enmination beyond tie boundaries required to meet the circumferential weld examination requirements. No significant loading conditions or known material degrM ation mechanisms have become evident to date which specifically relate to iongitudinal seam welds in nuclear plant !
piping, if any degradation associated with a longitudinal weld were to occur, it is expected that it would be located at the intersection with a circumferential weld. 'This intersection is inspected in accordance with the provisions of Code Case N-524. Furthermore, the 1986 ASME Code,Section XI Appendix III,
" Ultrasonic Examination of Piping Systems," which is applicable to the suWect plant, requires scanning fnr reflectors parallel and transverse to the weld seam in the case of ferritic piping, contrary to the requirement in some older Code editions to only scan for reflectors oriented parallel to the weld seam.
The transverse scan of a circumferential weld will further detect reflectors oriented parallel to a longitudinal weld at the root of an intersection of a longitudinal seam.
2.7 Conclusion Based on the above discussions, the staff concludes that the licensees' proposed use of Code Case N-524 as an alternative to the Code requirements provides an acceptable level of quality and safety while climinating personnel radiation ex)osure associated with the examination of longitudinal welds.
Therefore, tie licensees' proposed alternative to use Code Case N-524 is authorized for Davis-Besse pursuant to 10 CFR 50.55a(a)(3)(1). The licensees are authorized to use Codo Case N-524 until such time as the code case is included in a future revision of Regulatory Guide 1.141. At that time the licensees are to follow all provisiuns in Code Case N-524, with limitations issued in Regulatory Guide 1.147, if any, should the licensees continue to implement this relief request.
3.0 RElfEF RE0 VEST NO. RR-A14 3.1 [gmoonent Description Class 1, 2, and 3 Integrelly Welded Attachments - Request for approval to use Code Case N-509.
3.2 ASME Code Class ASME Section XI, Class 1, 2, and 3 Component Supports
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. 3.3 ASME Examination Renuirements. ASME Section XI. 1986 Edition Examination Category B-H, Integral Attachments for Vessels I
Examination Category B-K-1, Integral Attachments for Piping,- Pumps, and Valves l Examination Category C-C, Integral Attachments for Vessels, Piping, Pumps, and- :
Valves- !
Examination Category D-A, Systems in Support of Reactor Shutdown Function l
Examination Category D-8,. Systems in support of Emergency Core Cooling, !
Containment Heat Removal, Atmospheric Cleanup, and Reactor Residual Heat- ;
Removal !
Examination Category D-C, Systems in Support of Residual Heat Removal from .
Spent Fuel Storage Pool 3 l
3.4 Basis-for Relief (as stated) ;
1&ble IW8-2500-1 Examination Category B-K-1, and Table IWC-2500-1, .
Exhaination Category C-C limit the examination of integrally welded r attachments to only those attachments with a base material design thickness of 5/8 inch or greater. Thirty-three (33%) percent of the Class 1 and 37% of the -
Class 2 integrally welded _ attachments installed at Davis-Besse have ,
attachments which meet these thickness requirements. On the Class 2 Main :
Feedwater System, 100% of the supports require examination, while 65% require :
examination on.the Class 2 Main Steam System.
l The examination percentages for the examination of integral attachment welds !
exceed those percentages required for both piping and the supports associated- i with these attachment welds. Statistical principles recognize.that 100%
inspection is not necessary to ensure overall system integrity. These :
statistical principles are already implemented through sampling plans ,
permitted in Subsections IWB and IWC in which 25% of the Class 1_ piping welds ;
and 7.5% of the Class-2 piping welds require examination. Similarly, ASME has-
- recognized:through Code Case N-491 and the'1990 addendum to the 1989 edition s'
- " - of Section XI that component and piping support integrity could be verified by
- ensining 25% of Class 1,15% of Class 2, and 10% of Class 3 of piping supports.
Implementation of the Code Case N-509 Sampling Plan will significantly reduce -
the labor necessary to. support scaffold erection and insulation removal,.as well- as actual . performance of_ the, examinations. In many cases, scaffold
- erection:end insulation removal is only for the. attachment weld examination, as the hanger associated with:the attachment weld.does not' require examination.- -Based on the sampling percentages permitted by Code Case N-509 - I tit-is expected that occupational. radiation exposure involving Class 1, 2, .
- and-3 piping systems could be reduced by as much as 23%, 27%, and 2%,
respectively, over that expected. if the present Code-required inspections were {
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i i < ~6-l perfomed. Furthemore, the Code-required examinations are only required on !
- those integral attachments with a base material thickness 5/8 inch or greater. j i This pcpulation represents only 22% of the total number of integral attachment i welds. Application of Code Case N-509 will allow the population available for i 1
examination to include all types of integral attachments, not just those which .
.have a base material thickness 5/8 inch or greater.
l' I Code Case N-509 requires that the Class 1, 2 and 3 component supports be '
- selected for examination in accordance with IWF of the 1989 edition with the
. 1990-adoenda. Toledo Edison Relief Request RR-A9 permits the use of Code Case '
L N-491 for the selection and examination of Class 1, 2, and 3 component -
supports. As Code Cate N-491 was incorporated into the-1990 addenda, the use '
of Code Case N-491 will meet the 1989 edition,-1990 addenda.
! Code Case N-509 has been approved by the ASME Aaller and Pressure Vessel Code ,
j Committee and the Board on Nuclear Codes and Standards as an acceptable-alternative to the ru1es of the ASME Boiler and Pressure Vessel Code, .
Section XI. l 3.5 Alternative Examination las stated)
L Examination of integral attachment welds will be performed in accordance with ,
! Code Case N-509 with the exception that Code Case N-491 will be used for component support selection rather than the 1989 edition with the 1990 !
addende. When Code Case N-509 is approved in Regulatory Guide 1.147, any j: additional limitations recommended by the NRC staff will also be incorporated.
, 3.6 Evaluation ;
^
The licensees have proposed, as an alternative to the Code requirements, to apply the requirements of Code Case N-509 for the examination of integrally L welded attachments Ln Class 1, 2, and 3 piping and com>onents. Code Case .
N-509 provides alternative sampling requirements for t1e examination of Class 1, 2, and 3 integral attachments by specifying examination of 10% of the 4 g integral attachments in each of the nonexempt Code Class 1, 2, and 3 systems ;
-in accordance with Code Case N-509 requirsments. Based or, industry experience ;
- in the United States, no significant loading conditions or knowr, material -
L degradation mechanisms relating to integral attachment welds in~ nuclear power plant' piping have become evident. The staff finds that a sampling process, if
. extended to welded attachments, would provide assurance that service-related
-depradation is not occurring and a minimum sample of 10% of all integral we ded attachments in Code Class 1, 2, and 3 components-in each system, is sufficient to assure that degradation, if-occurring, will be detected.
Further, should a. service-induced defact be detected-in these welds,-ASME Code i Case N-509 specifies examination expansion-criteria to ensure degradation in other-attachment welds would be detected. . Therefore, the staff concludes that-the use of the alternative contained-in Code Case N-509, with a minimum 10%
1 selection of all integrally welded attachments in each Code class, will i~ provide _an acceptable level of quality and safety. .
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3.7 Conclusion Based on the above discussions, the staff concludes that the licensces' proposed use of Code Case N-509 as an alternative to the Code requirements is acceptable with the condition that a minimum 10% sample for each system of all nonexempt integrally welded attachments to piping, pumps, and valves in Class 1, 2, and 3 systems is examined. The licensees' proposed alternativi to use Code Case N-509 provides an acceptable level of quality and safety and is, therefore, authorized pursuant to 10 CFR 50.55a(a)(3)(1). The licensees are authorized to use Code Case N-509 until such time as the code case is included in a future revision of_ Regulatory Guide 1.147. At that time, the licensees should follow all provisions and any limitations that may be described in d
Regulatory Guide 1.147 concerning the use of Code Case N-509.
4.0 RELIEF LOVEST NO. RB-M!i
,- i.1 Comocnent Descriotion Hydrostatic Testing of Class 1, 2, and 3 Systems - Request for Approval to use Code Case N-498-1.
4.2 ASME Code Class ASME Section XI, Class 1, 2, ad 3 4.3 ASME Examination Reauirements. ASME Section XI. 1986 Edition Table IWB-2500-1 Examination Category B-P requires hydrostatic testing of pressure retaining components each inspection interval.
Table IWC-2500-1 Examination Category C-H requires hydrostatic testing of pressure retaining components each inspection interval.
Table IWD-2500-1 Examination Categories D-A, D-B, and C-C require hydrostatic testing of pressure retaining components each inspection interval.
4.4 BAsjs for Relief f as stated)
Code Case N-498-1 provides alternative requirements for hydrotesting Class 1, 2, and 3 Systems. Hydtostatic testing is performed to verify the pressure boundary integrity of the system.
Hydrostatic tests require that systems be taken out of service. This requires that tests be performed under outage conditions. Additional pumps are often required to obtain the necessary test pressures. As the hydrostatic test pressure is above the normal operating pressures, relief valves which are installed to protect the system from overpressurization must be removed or gagged. The hydrostatic test also stresses nonpressure-retaining components.
- such as gaskets, pump seals, and valve packing, increasing their likelihood to leak during'or-following the hydrosthtic test.
Extensive outage scheduling is required for the hydrostatic test arogram as the systems art: not available during testing. Although many of tie systems are not required to be o>erable in outage conditions, they are maintained functional to minimize slutd un risks during varied outage conditions. A typical hydrostatic test takes approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to perform with a crew of two to three people. Typical radiation levels in test areas are approximately 5 mrem. This results in a total personnel dose of approximately 150 arem per test. Performing 60 lydrostatic tests would result in an accumulated dose of 9 Res.
System pressure tests provide an acceptable alternative to hydrostatic tests, lhese system pressure tests are performed at normal operating pressures and temperatures. System pressure test pressures are not significantly lower than hydrostatic test prestures. These tests are performed on systems which are in their normal lineups, reducing test preparation, performance time, and personnel exposures, while increasing svstem availability. Although testing is performed at a lower test pressure, any pressure boundary leakage will be readily apparent, thereby ensuring that the level of quality and safety of the system is maintained.
Code Case N-498-1 has been approved by the ASME Boller and Pressure Vessei Code Committee and the Board on Nuclear Codes and Standards as an acceptable siternative to the ru1es of the ASME Butler and Pressure Vessel Code, Eection XI.
4.5 &l.ternative Examination (as stugd).
Code Case N-498-1 will be used in lieu of Table IWB-2500-1, Table IWC-2500-1, and Table IWD-2500-1 hydrostatic test requirements. When Code Case N-498-1 is a) proved in Regulatory Guide 1.147, any additional limitations recomended by tie NRC staff will also be incorporated.
4.6 Evaluation The licensees have requested approval for the implementation of the alternative rules of ASME Section XI, Code Case N-4! 91, " Alternative Rules for 10-yeer System Hydrc,.tatic Testing for Class 1, ., and 3 Systems," dated May ll,1194, in lieu of 10-year hydrostatic testing of Class 1, 2, and 3 systems. Use of Code t,ase N-498 for Class 1 and 2 systems was previously approved by the NRC in Regulatory Guide 1.147, Rev.11. The rules for Class 1 and 2 in N-498-1 are unchanged from N-498. The staff found the use of N-498 to be acceptable since the alternative previc!ed reasonable assurance of operational readiness, and compliance with the specified Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Code Case N-498-1, however, encompasses Class 3 components and specifies requirements for Class 3 that are identical to those for Class 2 components.
In lieu of the 10-year hydrostatic pressure testing at or near the end of the
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10-year interval, Code Case N-498-1 requires that a visual examination (VT-2) :
be performed in conjunction with system leakage testing in accordance with I paragraph IWA-5000. Class 3 systems do not normally receive-the amount and/or i type of nondestructive examinations that Class 1 and 2 systems receive. While ,
Class 1 and 2 system failures are relatively uncommon, Class 3 leaks occur !
- more frequently and the failure mode typically differs. The most common !
failure causes in Class 3 systems are erosion-corrosion,-microbiologically 1 induced corrosion, and general corrosion. The licensees generally have
. programs in place for prevention, detection, and evaluation of these i degradation mechanisms. The industry experience further demonstrates that !
leaks.are seldom disco $.4 red as a result of hydrostatic test pressure driving a !
preexisting. flaw through-wall. Rather, they are found in most cases at normal operating conditions. !
Licensees incur considerable time, radiation dose and resources to conduct a
- hydrostatic test in comparison to a system leakage test for a minimal amount of increased assurance provided by a slightly highsr pressure associated with !
hydrostatic test of Class 3 systems. . Therefore, the staff finds that ,
compliance with the ASNE Section XI hydrostatic testing requirements as ;
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opposed to system leakage test of Class 3 systems, results in hardship and/or unusual difficulty to licensees without a compensating int.rease in the level of quality and safety. ,
4.7 conclusion j The staff has evaluated the information providd by the licensees in support of the request fnr relief to implement Code Case N-498-1 as an alternative to the 10-year system hydrostatic test required by the applicable ASME Code. i Section XI. The staff has determined that the proposed testing in accordance i with the rules.of Code Case N-498-1 provides reasonable assurance of i operational readiness, and compliance with the Code requirement would result ;
in hardship without a compensating-increase in the level of quality-and -
safety. Therefore, Relief Request No. RR-AIS is authorized, pursuant to 10
?
CFR 50.55a(a)(3)(ii), for Davis-Besse during the second inspection interval. ;
5.0 RELIEF REQUEST N0. RR-B8 ;
- 5.1 Component Description ,
Pressure Testing of Containmett Penetration Piping - Request for Approval to !
use Code Case N-522 The penetrations that will be tested using Code Case N-522 are listed in i
.. Table 1.. :
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5.2 ASME Code Class >
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' ASML Section XI, Class:2-B P
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i YABLE 1 CODE CASE N-522 PENETRATIONS Penetration Line Number Description P1 1"-CCB-17 Pressurizer Sample Line P8A thru 8J 8"-HBB-19 Eight Containment Vacuum Relief Lines '
P12 3"-HCB-40 Component Co'.siing Water Supply to the Control Rod Drives P13 4"-HBB-2 Containrent Vessel Normal Sump Drain P14 24"-CCB-21 Letdown Line to Purification Domineralizers P16 3"-HCB-33 Containment Vessel Equipment Vent Header Pl7 8"-HCB-49 Containment Vessel Leak Test Line P21 4"-HCB-23 Demineralized Water Supply Line P23 29" ID Fuel Transfer Tube P24 29" ID Fuel Transfer Tube P32 3"-HCB-32 Reactor Coolant System Drain Line to Reactor Coolant Drain Tank P33 48"-HBB-17 Containment Vessel Purge Inlet Line P34 48"-HBB-18 Containment Vessel Purge Outlet Line P41 2"-HCB-7 Pressurizer Quench Tank Circulating Inlet Line P42A 14"-HBB-9 Service Air Supply Line ,
P43A 1"-hBB-10 Instrument Air Su) ply Line Core Flooding Tanc Fill and Nitrogen Supply Line P44A 1"-FCB-1 P44B 1"-HBB-14 Containment Nitrogen Supply Header P47A 1"-FCB-3 Coie Flooding Tank Sample Line P478 1"-FCB-1 Core Flooding Tank Vent Line P48 3"-HCB-22 Pressurizer Quench Tank Circulating Outlet Line P49 8"-HCB-11 Refueling Canal Fill Line PS2- 1%"-FCB-3 Reactor Coolant Pump Seal Water Supply P53 1%"-FCB-3 Reactor Coolant Pump Seal Water Supply P54 1%"-FCB-3 Reactor Coolant Pump Seal Water Supply P55 1%"-FCB-3 Reactor Coolant Pur Seal Water Supply P56 1"-CCB-20 Reactor Coolant Pu r, Seal Water Return P59 8"-HCB-43 Secondary Side Chemical Cleaning Line P68A 1"-HCB-26 Pressurizer Quench Tank Sample Line P71C 1"-FCB-1 Core Flooding Tank Fill and Nitrogen Supply Line
.5.3 ASME Examination Reauirements. ASME Section XI. 1986 Edition
. Code Item C7.30. Table IWB-2500, requires a system pressure test of piping each inspection period.
Code Item C7.40 Table IWB-2500, requires a system hydrostatic test of piping each-inspection interval.
Code Item C7.70, Table 'IWB-2$00, requires a system pressure test of valves each inspection period.
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Code Item C7.80, Table IWB-2500, requires a system hydrostatic test of valves- _
each inspection interval.
l 5.4 Basis for Relief fas stated) !
l Code Case N-522 permits the use of 10 CFR Part 50, Appendix J testing as an r alternative to the rules in Table IWC-2500-1, Category C-H, for pressure - i testing piping that penetrates'a containment vessel when ths piping and !
isolation valves that are part of the containment system are Class 2, but the balance of the piping system is outside the scope of Section XI. {
i
- With the exception of pene' rations P1, P44A, P47A, and P478, the penetration
siping is Class 2 solely because it forms part of the containment. pressure
>oundary. The balance-of the penetration's piping system is outside the scope ;
of Section XI.- [
I For penetration P1 (Pressurizer Sample Line), the piping through the containment .is Class 2 solely because.it forms part of the containment pressure boundary. The piping outside the containment vessel is outside the ,
, scope of Section XI. The containment isolation valve inside containment
-serves as a boundary valve between the Class 1 Reactor Coolant System and the Class 2 containment penetration piping.
Similarly, the piping for penetrations P44A (Core Flooding Tank Fill and .
Nitrogen Sup)1y Line), P47A (Core Flooding Tank Sample Line), P47B (Core Flooding Tant Vent Line), and P71C (Core Flooding Tank Fill and Nitrogen .
Supply Line) through the containment are Class 2 solely bec use they form part ;
of the containment pressure boundary. The piping outside the containment !
vessel is outside the scope of Section XI. The containment isolation valve <
- inside containment-serves as a_ boundary valve between the Class 2 Core Flood System and the Class 2 containment penetration piping.
t Each containment penetration blank flange or isolation valve which is closed
- i. or capable of automatic closure isolates the Class 2 piping from the noncode piping. Containment integrity is the only safety-related function associated ;
with this piping.
l The Davis-Besse Technical Specifications require that containment penetrations be tested ~1n accordance with 10 CFR Part 50, Appendix J. Performing a system pressure test or hydrostatic test on the same components tested by the
+
Appendix J test imposes a burden of duplicate testing. Duplicate testing ,
results in an increase in outage labor-hours and personnel exposures without an-increase in the level-of quality or safety. The Appendix J testing, which is periomed at maximum containment accident pressures, assures that the
- containment-pressure boundary is being maintained at an acceptable level.
Code Case'N-522Lhas been approved by the.ASt'E Soffer and Pressure Vesse? Code ;
Committee'and the Board on Nuclear Codes and Standards as an acceptable
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. a1ternative to the rules of the ASME Boller and Pressure Vessel Code,Section XI.
5.5 '*ernative Examination (as stated)
Pressw Testing of Containment Penetration will be performed in accordance with Code Case N-522. When Code Case N-522 is approved in Regulatory Guide 1.147, any additional limitations recommended by the NRC staff will also be incorporated.
5.6 Eyaluation The system leakage test required by the Code in Examination Category C-H provides periodic verification of the leak-tight integrity of Class 2 piping systems or segments once every 40 months. The pipe segments fro'n noncode class systems that penetrate containment are designed and examined as Class 2 piping for the sole purpose of maintaining the integrity of containment. The Appendix J pressure testing proposed by the licensees as an alternative to the VT-2 method of testing, provides periodic verification by tests of the leak-tight integrity of the primary reactor containment, and of systems and components that penetrate containment. The test provides assurance that the containment pressure boundary is being maintained at an acceptable level while monitoring for deterioration of seals, valves, and piping.
The containment penetration piping and the containment isolation valves (CIVs) are part of the containment pressure boundary and are classified as Class 2.
Hence, the containment isolation valves along with the connecting pipe segments must withstand the calculated peak containment internal pressure related to the design basis loss-of-coolant accident as specified in the Technical Specifications. Since Code Case N-522 has not specified the test pressure for containment penetration piping, the staff has determined that the pressure testing be conducted at the peak calculated containment pressure for a design basis accident. In the acceptance criteria for the A)pendix J test, the combined leakage from all penetrations and valves must be 3elow a permissible limit, whereas the ASME Section XI Code does not allow any pressure boundary leakage during pressure testing and requires in paragraph IWC-5210(b) that when air is used as a testing medium, the test procedure must include methods for detection and location of through-wall leaks in system components. Since most Appendix J tests are conducted using air as a test medium, the staff has determined that the licensees' proposed alternative of conducting the Appendix J test at peak calculated containment pressure with the provision to detect and locate pressure boundary leakage would provide an acceptable level of quality and safety as that of the ASME Code,Section XI, 1986 edition for pressure testing of containment penetration piping.
5.7 [onclusion The staff has evaluated the information provided by the licensees in support of a relief request to use Code Case N-522 as an alternative to pressure
, testing of Class 2 components at containment penetrations in Relief Request RR-B8 for the second 10-year ISI interval at Davis-Besse. The staff concludes that implementation of Code Case N-522, subject to requirements that the test-be conducted at peak calculated containment pressure, and that the test procedure include methods for detection and location of through-wall leakage in CIVs and pipe segments between the CIVs, would provide an acceptable level of quality and safety. Therefore, the proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(1). The usc of Code Case N-522 is authorized for Davis-Besse during the second inspection interval until such time as the Code Case is approved by reference in Regulatory Guide 1.147. At that time, if the licensees intend to continue to implement this Code Case, the licensees are to follow all provisions in Code Case N-522 with limitations issued in Regulatory Guide 1.147, if any.
Principal Contributor: P. Patnaik Date: January 13, 1998 o ,,
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