ML20204E672
| ML20204E672 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 03/11/1999 |
| From: | Geoffrey Edwards PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9903250098 | |
| Download: ML20204E672 (16) | |
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' ~v PECO NUCLEAR nc~ov c-v Nidear Group Headquarters A UNfr Of PECO ENfrcy 965 Chesterbrook Boukivard Wayne, PA 19087-5691 March 11,1999 Docket Nos. 50-352 50-353 License Nos. NFP j NFP-85 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Subject:
Limerick Generating Station, Units 1 and 2 Respoilse to Request for Additional information Inservice Inspection Program First and Second 10-Year Interval Relief Requests
Dear Sir / Madam:
By letter dated January 30,1998, PECO Energy Company submitted various relief requests in support of the implementation of the Inservice inspection (ISI) Program at Limerick Generating Station (LGS), Units 1 and 2. PECO Energy submitted these relief requests in accordance with the requirements of 10CFR50.55a(3) requesting relief from certain American Society of j
Mechanical Engineers (ASME),Section XI, Code requirements.
By letter dated September 25,1998, PECO Energy responded to a request for additional information regarding ISI Program Relief Request RR-01, Revision 2, which pertained to 1
6xamination requirements for Class 1 pressure retaining circumferential and longitudinal shell J
welds in the reactor pressure vessel.
j Subsequently, by letter dated February 9,1999, the NRC requested that PECO Energy provide supplementalinformation on several other relief requests submitted in our January 30,1998, letter. Specifically, the NRC requested additionalinformation regarding the following Relief Requests:
Relief Request RR-05, Revision 2 Relief Request RR-11, Revision 1 g
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i Relief Request RR-121 Relief Request RR-12-2
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l Relief Request RR-12-5' Relief Request RR-23, Revision 1 i
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March 11,1999 Page 2 s
. Accordingly, the attachment to this letter provides PECO Energy's response to the specific issues / questions identified by the NRC in its February 9,1999, letter. The attachment contains a restatement of each issue identified by the NRC followed by our response. Timely resolution of these issues will support the upcoming refueling outage at LGS, Unit 2, scheduled to begin on April 16,1999.
If you have any questions or require additionalinformation, please do not hesitate to contact us.
Very truly yours,
. D. Edwards Director-Licensing Attachment cc:
H. J. Miller, Administrator, Region I, USNRC (w/ attachment)
A. L. Burritt, USNRC Senior Resident inspector, LGS (w/ attachment) l 1
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t ATTACHMENT Limerick Generating Station, Units 1 and 2 Response to Request for Additional Information inservice Inspection (ISI) Program Relief Requests RR-05, Revision 2, RR-11, Revision 1 RR-12-1, RR-12-2, RR-12-5, and RR-23, Revision 1 f
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l Docket Nos. 50-352,50-353 Attachment March 11,1999 Page 1 of 13 a
Limerick Generating Station, Units 1 and 2 Response to Request for Additional Information Inservice inspection (ISI) Program Relief Requests RR-05, Revision 2, RR-11, Revision 1, RR 12-1, RR 12 2, RR 12 5, and RR 23, Revisioni Relief Reauest No. RR-05 Revision 1 1.
Request for Relief No. RR-05, Revision 2: ASME Code,Section XI. Examination Category C-C requires a surface examination of 100% of selected areas of each welded attachment to vessels, piping, pumps, and valves ea:h inspection interval. In the case of multiple vessels, only the integrally welded attachments of one vesselin a group of vessels of similar design and service (or the equivalent of one vessel) need be examined.
Pursuant to 10CFR50.55a(a)(3)(i), the licensee proposed to perform tha required surface examinations of Class 2 integral attachment welds in accordance with ASME Section XI,1995 Edition with the 1996 Addenda, Table IWC-2500-1, Examination Category C-C as an attemative to the 1986 Edition currentlyin use at LGS, Units 1 and 2.
However, it appears to the staff that the licensee has interpreted the later Code to require surface examinations only when deformation has been identified. The 1995 Edition,1996 Addenda doeu not limit examination of Class 2 welded attachments to "only when deformation Is identified." The surface examination nt each interval requirement still exists. It is the opinion of the staff that the later Code has imposed an additional examination requirement when deformation is identified.
If the staffs understanding that the licensee's proposaiis to require surface examinations only when deformation has been identified, please clarify. Moreover, describe how the proposed alternative provides an acceptable level of quality and safety at LGS, Units 1 and 2.
Response
PECO Energy is requesting relief to perform the required examinations of Class 2 integral attachment welds to vessels, piping, pumps and valves in accordance with the American Sociecy of Mechanical Engineers (ASME)Section XI Code,1995 Edition with the 1996 Addenda, Table IWC-2500-1, Examination Category C-C. As required by Table IWC-2500-1, Examination Category C-C, Note (6),
additional examinations of the integral attachment welds shall be performed when component support member deformation is identified.
Access for examination equipment is limited by component configuration or installed support members.
During the First inspe: tion Interval, attempts to perform alternate Non-Destructive Examination (NDE) methods, e.g., Liquid Penetrant (PT) or Ultrasonic Testing (UT) on Class 2 integral attachment welds proved urisuccessful. Neither NDE method resulted in an increase in examination coverage (in fact UT resulted in less coverage). In addition, there was a significant increase in radiation exposure to both examination and support personnel due to the weld surface preparation requirements and increased examination times associated with these methods. Also, installed support members caused the sanie access limitations regardless of the NDE method used.
c Docket Nos. 50-352,50-353 Attachment March 11,1999 Page 2 of 13 All welds were examined to the maximum extent practical. Increased examination coverage is not possible without undue hardship, such as disassembly of the supports, the installation of temporary supports, increased radiation exposure to examination and support personnel, and/or plant modifications.
1 The 1995 Edition with the 1995 Addendum of ASME Section XI Code has recognized these generic access limitations and has appropriately modified the Examination Requirements. The ASME Code required examination coverage for Class 2 integral attachment welds has been redefined as 100% of the accessible surfaces of each weld to the extent practical within the limitations of design, geometry and materials of construction of the components. This change precludes the need for disassembly of the supports, the installation of temporary supports, unwarranted radiation exposure, and/or plant modifications solely for the purpose of ochieving ASME Code coverage in recognition of this change Table IWC-2500-1, Examination Category C-C, includes Note (6) which requires additional examinations of the integral attachment welds when component support member deformation is identified.
Adoption of PECO Energy's proposed alternative will result in a reduction in radiation exposure to examination and support personnel and will reduce the number of welds requiring relief requests due to incomplete examination coverage based solely on the requirements of the 1986 and 1989 Editions of the ASME Section XI Code. Approval of this generic request for relief will ensure compliance with the Limerick Generating Station (LGS), Units 1 and 2, ASME Section XI Programs throughout the Inspection Interval. This alternative proposal is being pursued to address issues such as; changes in the total population of Examination Category C-C welds as a result of plant repairs, replacements and modifications; component reselections due to ALARA; alignment with other examination requirements and updates to the ASME Section XI Program Code Edition of Record; and fractional differences in the actual examination coverage recorded by the NDE Technician on the Examination Record from those estimated in a relief request prior to performing the examination.
These alternative rules are based on the 1995 Edition with the 1995 Addendum of the Code. Additional examination requirements have been incorporated into the ASME Code rules to address changes in examination coverage requirements and as such, provide an acceptable level of quality and safety which does not compromise the adequacy of the LGS, Units 1 and 2, ASME Section XI Programs in meeting the intent of the ASME Code.
Relief Reauest No. RR 11, Revision 1 2.
Request for Relief No. RR-11, Revision 1: ASME Code,Section XI, Examination Categories B-H and B-K-1 require 100% volumetric or surface examination, as applicable, for each attachment weld subject to examination. Examinations shall be performed during the first and second inspection intervals forliccnsees using Inspection Program B.
Pursuant to 10CFR50.55a(a)(3)(i), the licensee proposed to perform the required examinations in accordance with ASME Section XI,1995 Edition with the 1996 Addenda, Table IWB-2500-1, Examination Category B-K as supplemented by Code Case N-323-1, Altemative Examination For Weld Attachments to Pressure Vessels, for Figurs Nos. IWB-2500-13 and IWB-2500-14 as an atremative to the 1986 Edition currently in use at LGS, Units 1 and 2.
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Docket Nos. 50-352,50-353
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[However, it appears to the staff: hat licensee has interpreted the later Code to require surface
- examinations only when deformation has been identified. The 1995 Edition,1996 Addenda does not limit examination of Class 1 welded attachments to 'only when deformation is identified." The surface examination requirement within an inspection interval still exists. It is the staff's opinion that the later ICode has imposed an additional examination requirement when deformation is identified.
If the staff's understanding that the licensee's proposalis to require surface examinations only when
' eformation has been identified, please clarify. Moreover, describe how the proposed attemative d
provides an acceptable level of quality and safety at LGS, Units 1 and 2.
Response
. PECO Energy is requesting relief to perform the required examinations of Class 1, integrally welded attachrnents to the reactor pressure vessel, Examination Category B-H, and integrally welded attachments
. to piping, pumps and valves, Examination Category B-K 1 in accordance with ASME Section XI,1995 Editim with the 1996 Addenda, Table IWB-2500-1, Examination Category B-K as supplemented by Code Case N 323-1, Altemative Examination for Welded Attachments to Pressure Vessels, for Figure Nos.
IWB-2500-13 and IWB-2500-14. As required by Table IWB-2500-1, Examination Category B-K, Note (6),
additional examinations of the integral attachment welds shall be performed when component support
- member deformation is identified.
- Access to the reactor pressure vessel stabilizer bracket attachment welds is limited due to mirror insulation support members affixed to the stabilizer bracket lugs and the stabilizer assembly support members. These support members preclude equipment access necessary for complete magnetic particle examination of the weld and required area. Access for examination equipment is also limited in the area of skirt attachment weld build-up. The configuration of the Reactor Pressure Vessel (RPV) skirt knuckle to the bottom head limits access for complete examins' ion of the underside of the weld. Access for examination'of Class 1 piping integral attachment welds is limited due to installed support members.
During the First inspection Interval, attempts to perform both PT and UT of the reactor pressure vessel integral attachment welds proved unsuccessful. Neither NDE method resulted in an increate in
' examination coverage (in fact UT resulted in less coverage). Also, there was a significant increase in
' radiation exposure to both examination and support personnel due to the weld surface preparation requirements and increased examination times associated with these methods. In the case of the piping j
integral attachment welds, the installed support members caused the same access limitations regardless j
of the NDE method used.
All welds were examined to the maximum extent practical, increased examination coverage is not possible without undue hardship, such as disassembly uf the supports, the installation of temporary supports, increased radiation exposure to examination and support personnel, and/or plant modifications.
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Docket Nos. 50-352,50-353 Attachment j
March 11,1999 Page 4 of 13 j
1 The 1995 Edition with the 1995 Addendum of ASME Section XI (and Code Case N-323-1) has recognized these generic access limitations ano has appropriately modified the Examination Requirements. The ASME Code required examination coverage for Class 1 Integral attachment welds has been redefined as 100% of the accessible portions of each weld to the extent practical within the limitations of design, f
geometry and materials of construction of the components. This change precludes the need for
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disassembly of the supports, the installation of temporary supports, unwarranted radiation exposure, and/or plant modifications solely for the purpose of achieving ASME Code coverage. In recognition of this j
change Table IWB-2500-1, Examination Category B-K, includes Note (6) which requires additional
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examinations of the integral attachment welds when component support member deformation is identified.
i Adoption of PECO Energy's proposed alternative will result in a reductio 7 in radiation exposure to examination and support personnel and will reduce the number of welds requiring relief requests due to incomplete examination coverage based solely on the requirements of the 1986 and 1989 Editions of the ASME Section XI Code. Approval of this generic request for relief will ensure compliance with the LGS, i
Units 1 and 2, ASME Section XI Programs throughout the Inspection Interval. This alternative proposs' 'a being pursued to address issues such as; changes in the total population of Examination Category P-K-1 welds as a result of plant repairs, replacements and modifications; ALARA ; and fractional differv.ces in j
the actual examination coverage recorded by the NDE Technician on the Examination Rrvro from ihose estimated in a relief request prior to performing the examination.
These alternative rules are based on the 1995 Edition with the 1995 Addendum of the Code. Additional examination requirements have been incorporated into the ASME Code rules to address changes in examination coverage requirements and as such, provide an acceptable level of quality and safety which does not compromise the adequacy of the LGS, Units 1 and 2, ASME Section XI Programs in meeting the intent of the ASME Code.
Relief Reouest No, RR-12-1 3.
Request for Relief No. RR-12-1: ASME Code,Section XI, Paragraph IWA-4400, Pressure Test, requires a system hydrostatic test in accordance with IWA-5000 after repairs by welding on the pressure-retaining boundary.
Pursuan: to 10CFR50.55a(a)(3)(ii), the licensee proposed to use Code Case N-416-1, Alternative Pressure Test Requirements for Weided Repairs or Installation of Replacement items by Welding, Class 1, 2 and 3,Section XI, Division 1.
i The licensee appears to be requesting authorization to use Code Case N-416-1 without implementing all ofits provisions. If the staff's interpretation of the licensee's proposalis incorrect, please clarify.
Moreover, describe how the proposed attemative provides an acceptable level of quality and safety at LGS, Units 1 and 2.
a Docket Nos 50-352,50-353 Attachment March 11,1999 Page 5 of 13
Response
The use of ASME Code Case N-416-1, Altemative Pressure Test Requirement for Welded Repairs or Installation of Replacement items by Welding, Class 1,2 and 3 was previously authorized per NRC Safety Evaluation Report (SER) for Docket Nos. 50-352 and 50-353, Relief Request RR-12 (Revision 1), RR-22 (Revision 1), and RR-16 (Revision 1), Limerick Generating Station, Units 1 and 2 (TAC Nos. M91712 and M91713), dated June 29,1995. Table RR-12-1, was included in our January 30,1998, submittal solely for.
the purpose of completeness of Relief Request No. RR-12.
The alternate provisions of ASME Section XI Code Case N-416-1, Altemative Pressure Test Requirement for Welded Repairs or Installation of Replacement items by Welding, Class 1,2 and 3 were authorized for LGS, Units 1 and 2, pursuant to 10CFR50.55a(a)(3)(ii) provided:
NDE shall be performed in accordance with the methods and acceptance criteria of the applicable Subsection of the 1992 Edition of ASME Section Ill.
When performing repairs by welding, or the installation of replacement items by welding, on the pressure retaining boundary of Class 3 components, an additional surface examination (Magnetic Particle (MT) or PT) shall be performed on the root pass layer of butt and socket welded joints when surface examination is required for the final weld by the 1992 Edition of ASME Section Ill.
For those Class 3 welds receiving radiography in lieu of a surface examination in accordance with ASME Section lit, no additional surface examination of the root layer needs to be performed. This provision does not apply to Class 1 and 2 components, since these components have an ongoing requirement for surface and volumetric examinations as part of the ASME Section XI Inservice 4
Inspection Program.
.. Prior to or immediately upon return to service, a visual examination (VT-2) shall be performed in conjunction with a system leakage test, using the 1992 Edition of ASME Section XI, in accordance with paragraph IWA-5000, at normal operating pressure and temperature.
Use of ASME Code Case N-416-1 shall be documented on a Form NIS-2, Owner's Report for Repairs or Replacements or approved altemative, when required.
In lieu of hydrostatic pressure testing for welded repairs or installation of replacement items b; welding, Code Case N-416-1 requires a visual examination (VT-2) be performed in conjunction with a system leakage test using the 1992 Edition of Secticn XI, in accordance with paragraph IWA-5000, at nominal operating pressure and temperature. This Code Case also specifies that NDE of the welds be performed
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in accordance with the applicable Subsection of the 1992 Edition of Section Ill.
The 1989 Edition of Sections XI and lil is the latest edition referenced in 10CFR50.55a. A comparison of I
the system pressure test requirements of the 1992 Edition of Section XI to the requirements of IWA-5000 l
of the 1989 Edition of Sectior XI finds that the 1992 Edition imposes a more uniform set of system i
pressure test requirements fo, Code Class 1,2, and 3 systems. The terminology associated with the system pressure test requirements for all three Code Classes has been clarified and streamlined. The
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Docket Nos. 50-352,50-353 Attachment March 11,1999 Page 6 of 13 test frequency anc.est pressure conditions associated with these tests have not been changed. The hold times for these tests have either remained unchanged or increased. The corrective actions with respect to removal of bolts from leaking bolted connections have been relaxed in the 1992 Edition, and this relaxation has been accepted by the USNRC in previous, safety evaluations. The post welded repair NDE requirements of the 1992 Edition of Section lli remain the same as the requirements of the 1989 Edition of Section 111.
Hardships are generally encountered with the performance of hydrostatic testing performed in accordance with the Code. Since hydrostatic test pressures are higher than nominal operating pressures, hydrostatic pressure testing frequently requires significant effort to set up and perform. The need to use special equipment, such as temporary attachment of test pumps and gauges, and the need for individual valve lineups can cause the testing to be time consuming and on critical path.
Piping components are designed for a number of loading cases that would be postulated to occur under the various modes of plant operation. Hydrostatic testing only subjects the piping components to a small increase in pressure over the design pressure and, therefore, does not present a significant challenge to pressure boundary integrity. Accordingly, hydrostatic pressure testing is primarily regarded as a means to enhance leakage detection during the examination of components under pressure, rather than solely as a measure to determine the structural integrity of the components.
Industry experience has demonstrated that leaks are not being discovered as a result of hydrostatic test pressures propagating a preexisting flaw through-wall. This experience indicates that leaks in most cases are being found when the system is at normal operating pressure. This is largely due to the fact that hydrostatic pressure testing is required only upon installation and then once every 10-year inspection interval, while system leakage tests at nominal operating pressures are conducted a minimum of once each refueling outage for Class i systems and each 40-month inspection period for Class 2 and 3 systems. In addition, leaks may be identified by plant operators during system walkdowns which may be conducted as often as once a shift.
Following the performance of weiding, the Code requires volumetric examination of repairs or replacements in Cocie Class 1 and 2, but would also allow only a surface examination of the final weld pass in Code Class 3 piping components it is recognized that there are no ongoing NDE requirements for Code Class 3 components except for visual examination for leaks in conjunction with the 10-year hydrosta'ic tests and the periodic pressure tests.
Considering the NDE performed on Code Class 1 end % systems and considering that the hydrostatic pressure tests rarely result in pressure boundary leans that would not occur during system leakage tests, PECO Energy believes that increased assurance of the integrity of Class 1 and 2 welds is not commensurate with tha burden of performing hydrostatic testing. However, considering the nature of NDE requirements fc,r Code Class 3 components, PECO Energy concurs that climination of the hydrostatic pressure testing while only performing system pressure testing is ar' acceptable attemative to hydrostatic testing unless additional surface examinations are perfonned on the root pass layer of butt and socket welds on the pressure retaining boundary of Class 3 components when the surface examination method is used in accordance with Section Ill.
As authorized, the use of ASME Code Case N-416-1 including the additional provisions as noted in the NRC SER, is planned until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, continued implementation of the Code Case will follow all the provisions in ASME Code Case N-416-1, subject to any limitations listed in Regulatory Guide 1.147.
l Docket Nos. 50-352,50-353 Attachment March 11,1999 Page 7 of 13 i
Relief Recuest No. RR 12-2 4.
Request for Relief No. RR-12-2: ASME Code,Section XI, Table IWB-2500-1. Examination Category B-P, Table IWC-2500-1, Examination Category C-H, and Table IWD-2500-1, Examination Categories
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D-A, D-B and D-C, require system hydrostatic testing of pressure-retaining components in accordance with IWA-5000 once each 10-yearinterval.
Pursuant to 10CFR50.55a(a)(3)(if, the licensee has requested authorization to use Code Case N-498-1, Alternate Rules for 10-Year Hydrostatic Pressure Testing for Class 1, 2, and 3 Systems,Section XI, Division 1.
The licensee appears to be requesting authorization to use Code Case N-498-1 without implementing all ofits provisions. For instance, the licensee has not committed to perform the required hold times for VT-2 examination.
If the staft's Interpretation of the licensee's proposalis incorrect, please clarify. Moreover, describe j
how the proposed alternative provides an acceptable level of quality and safety at LGS, Units 1 and 2.
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Response
The use of ASME Code Case N-498-1, Altemative Rules for 10-Year System Hydrostatic Testing for Class 1,2, and 3 Systems, was previously authorized for LGS, Unit 1, per NRC SER for Docket Nos.
50-352 and 50-353, Relief Request RR-12 (Revision 1), RR-22 (Revision 1), and RR-16 (Revision 1),
Limerick Generating Station, Units 1 and 2 (TAC Nos. M91712 and M91713), dated June 29,1995. Table RR-12-2, was included in our January 30,1998, submittal to obtain authorization for the use of the Code Case for LGS, Unit 2.
The altemate provisions of ASME Section XI Code Case N-498-1, Alternative Rules for 10-Year System Hydrostatic Testing for Class 1,2, and 3 Systems, were authorized for LGS, Unit 1, pursuant to 10CFR50.55a(a)(3)(ii) provided; A system leakage test (lWB-5221) shall be conducted at or near the end of each inspection e
interval, prior to reactor startup as an alternative to the 10-year system hydrostatic test required for Class 1 systems by Table IWB-2500-1, Category B-P. The boundary subject to test pressurization during the system leakage test shall extend to all Class 1 pressure retaining components within the system boundary.
A system pressure test shall be conducted at or near the end of each inspection interval or during the same inspection period of each inspectior ' erval of inspection Program B as an alternative to the 10-year system hydrostatic test requireu for Class 2 systems by Table IWC-2500-1, Category C-H, and for Class 3 systcms required by Table IWD-2500-1, Categories D-A, D-B, or D-C (D-B for the 1989 Edition with the 1991 and subsequent Addenda), as applicable. The boundaries subject to test pressurization during the system pressure test shall extend to all Class 2 and 3 components included in those portions of systems required to operate or support the safety system function up to and including the first normally closed valve, including a safety or relief valve, or valve capable of automatic closure when the safety function is required.
For Class i systems the test temperatures and pressures shall not exceed limiting conditions for the hydrostatic test curve as contained in the plant Technical Specifications.
Docket Nos. 50-352, 50-353 Attachment March 11,1999 Page 8 of 13 Prior to performing the VT-2 visual examination, the system shall be pressurized to nominal op-j e
erating pressure for at least four (4) hours for insulated systems and ten (10) minutes for non-insulated systems. The system shall be maintained at nominal operating pressure during j
performance of the VT-2 visual examination.
The VT-2 visual cxamination shall include all components within the boundaries identified above.
e Test instrumentation requirements of IWA-5260 are not applicable.
Relief Request No. RR-23 shall be used to address on a case-by case basis those portions of insulated Class 2 and 3 systems where it is impractical to pressurize the system to nominal operating pressure for at least four (4) hours prior to performing the VT-2 visual examination.
Information prepared in conjunction with ASME Code Case N-498-1, notes that the system hydrostatic test is not a test of the structural integrity of the system, but rather an enhanced leakage test, and that this
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was the original intent as indicated in a paper by S.H. Bush and R. R. Maccary, " Development of In-Service inspection Safety Philosophy for U.S.A. Nuclear Power Plants," ASME,1971. Piping components are designed for a number of loadings that would be postulated to occur under the various modes of plant operation. Hydrostatic testing only subjects the piping components to a small increase in pressure over the design pressure and, therefore, does not present a significant challenge to pressure boundary integrity since piping dead weight, themial expansion, and seismic loads, which may present far greater challenge to the structural integrity of a system than fluid pressure, are not part of the loading imposed during a hydrostatic test. Accordingly, hydrostatic pressure testing is primarily regarded as a means to enhance leakage detection during the examination of components under pressure, rather than as a measure to determine the structural integrity of the components.
PECO Energy is requesting approval to extend the implementation of the alternative rules of ASME,Section XI, Code Case N-498-1 to include LGS, Unit 2. The USNRC has previously approved (in Regulatory Guide 1.147, Rev.11) the use of Code Case N-498 for Class 1 and 2 systems. The NRC found N-498 acceptable because the altemative provided adequate assurance and because compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The rules for Code Class 1 and 2 in N-498-1 are unchanged from N-498.
Code Case N-498-1 encompasses Class 3 components and specifies requirements for Class 3 components that a,e identical to those for Class 2 components. In lieu of 10-year hydrostatic pressure testing at or near the end of the 10-year interval, Code Case N-498-1 requires a visual examination (VT-2) be performed in conjunction with system leakage testing in accordance with r aragraph IWA-5000.
Currently, PECO Energy incurs considerable time, radiation exposure, and cost expenditures implementing hydrostatic test requirements. A significant amount of effort may be necessary (depending on system, plant configuration, C ode class, etc.) to temporarily remove or disable code safety and/or relief valves to meet test pressure requirements. The safety assurance provided by the enhanced leakage gained from a slight increase in system pressure during a hydrostatic test is offset or negated by the following factors: having to gag or remove code safety and/or relief valves, placing the system in an off-normal state, erecting temporary supports in steam lines, possible extension of refueling outages, and resource requirements to set up testing with special equipment and gages.
m Docket Nos. 50-352,50-353 Attachment March 11,1999 Page 9 of 13 It is recognized that Class 3 systems do not normally receive the amount and/or 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. Based on a review of Class 3 system failures requirinq repair for the last 5 years in Licensee Event Reports and the Nuclear Plant Reliability Data System databases, the most common causes of failures are erosion-corrosion (EC),
microbiologically induced corrosion (MIC), and general corrosion. PECO Energy has programs in place for prevention, detection, and evaluation of EC and MIC. Leakage from general corrosion is readily apparent to NDE Technicians when performing a VT-2 examination during system pressure tests. The industry indicates that experience has demonstrated that, in general, leaks are not being discovered as a result of hydrostatic test pressures propagating a preexisting flaw through-wall. They indicate that leaks in most cases are being found when the system is at normal operating pressure.
Giving consideration to the minimal amount of increased assurance provided by the increased pressure
- associated with a hydrostatic test versus the pressure fer the system leakage test and the hardship associated with performing the ASME Code required hydrostatic test, PECO Energy finds that compliance with the Section XI hydrostatic testing requirements results in hardship and/or unusual difficulty for LGS Units 1 and 2 without a compensating increase in the level of quality and safety.
When approved, the use of ASME Code Case N-498-1 for LGS, Unit 2, shall be as authorized for LGS, Unit 1, in the NRC SER. It is also planned to use the Code Care for both LGS, Units 1 and 2, until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, continued implementation of the Code Case will follow all the provisions in ASME Code Case N-498-1, subject to any limitations listed in Regulatory Guide 1.147.
Relief Reauest No. RR-12 5 l
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Request for Relief No. RR-12-5: ASME Code,Section XI, IWA-5250(a)(2), requires that ifleakage l
Occurs at a bolted connection, the botting shall be removed, VT-3 visually examined for corrosion, and 1
evaluatedin accordancs with IWA-3100.
l Pursuant to 10CFR 50.55a(a)(3)(i), the licensee proposed the following allemative to the requirements ofIWA-5250(a)(2). The licensee stated:
l When leakage is identified at Class 1, 2, or 3 batted connections by VT-2 visual examination during system pressure testing, an evaluation willbe performed to determine the susceptibility of the botting to corrosion and assess the potential for failure. The evaluation will, at a minimum, consider the following factors:
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- 1. Boltingmaterials
- 2. Corrosiveness ofprocess fluidleaking
- 3. Leakagelocation
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- 4. Leakage history at connection or other system components 5.
Visual evidence of corrosion at connection (while connection is assembled)
- 6. Service age of botting materials I
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l Docket Nos. 50-352,50-353 Attachment March 11,1999 Page 10 of 13 When the pressure test is performed on a system that is in service or that Technical Specifications require to be operable, and the botting is susceptible to corrosion, the evaluation shall address the connection's structuralintegrity until the next component / system outage of sufficient duration. If the evaluation concludes the system can perform its safety related function, removal of the bolt closest to the source of the leakage and a W-3 visual examination of the bolt will be performed when the
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system or component is taken out of service for a sufficient duration (to accomplish other system maintenance activities).
IWA-3100 invokes the use of Articles IWB-3000, IWC-3000, and IWD-3000 for Class 1, 2, and 3 pressure-retaining components, respectively. None of the subparagraphs in these articles provide acceptance criteria for the W-3 visual examinations. In order for this relief request to be considered acceptable, the acceptance criteria must be specified by the licensee. The staff determined that it is technicallyprudent to implement a W-1 visual examination using the acceptance criteria definedin 1
IWB-3000 for botting removed for visual examination. Altematively, a W-3 visual examination using the IWB-3000, W-1 acceptance criteria, is also considered acceptable. Moreover, describe how the proposed alternative provides an acceptable level of quality and safety at LGS, Units 1 and 2.
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Resnonse 1
Pursuant to 10CFR50.55a(a)(3)(ii) PECO Energy proposes to implement the provisions of ASME Section XI Code Case N-566, Corrective Action for Leakage identified at Bolted Conmetions, which allows the conduct of an engine 9 ring evaluation of allleaking connections to determinc whether any bolting requires removal and inspection, as an alternative to the corrective measure requirements of IWA-5250(a)(2).
Further, PECO Energy proposes to apply the Class 1 requirements of IWB-3142.4, including th6 requirement for subsequent examinations on an increased frequency per IWB-2420(b) and (c) to holting in Class 1,2, and 3 components when acceptance of a relevant condition for continued service is based on analytical evaluation. When the engineering evaluation determines that bolting in Class 1,2, and 3 components is to be removed to determine if the condition is relevant then PECO Energy shall perform a VT-1 visual examination using the acceptance criteria defined in ASME Section XI, IWB-3517, Standards for Examination Category B-G-1, Pressure Retaining Bolting Greater Than 2 Inch in Diameter, and Examination Category B-G-2, Pressure Retaining Bolting 2 inch and Less in Diameter for the bolting removed for visual examination.
Removal of pressure retaining bolting at mechanical connections for visual, VT-3 examination and subsequent evaluation, in locations where leakage has been identified, is not always the most discerning j
course of action to determine the acceptability of the bolting. The Code requirement to remove, examine, and evaluate bolting in this situation does not allow PECO Energy to consider other factors which may indicate the acceptability of mechanicaljoint bolting.
Other factors which should be considered when evaluating botting acceptability when leakage has been identified at a mechanical joint include, but are not limited to: joint botting material, service age of joint bolting materials, location of the leakage, history of leakage at the joint, evidence of corrosion with the joint assembled, and corrosiveness of process fluid.
If any of the factors used for the evaluation indicates a potential for denradation of the bolting due to corrosion, then the most susceptible bolting will be removed and VT ',not VT-3) examined for corrosion, and evaluated in accordance with IWB-3517. When the removed bolt has evidence of degradation, additional botting in the connection will be removed in accordance with IWB-2430, receive a VT-1 examination, and an evaluation in accordance with IWB-3517. If the results of the engineering evaluation indicate that bolting degradation is not expected, bolting need not be removed.
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Docket Nos. 50-352, 50-353 Attachment l
March 11,1999 Page 11 of 13 Performance of the pressure test while the system is in service may identify leakage at a bolted connection that, upon evaluation, may conclude that the integrity and pressure retaining ability of the joint 4
is not challenged. It would not be prudent to negatively impact the availability of a safety system by removing the system from service to address a leak that does not challenge the system's ability to perform its safety function.
l Further, if evidence exists which indicates that the leakage found is not a preexisting condition and the leakage is stopped, the concem for cortasion of the bolting material is reduced. The cost and added radiation exposure associated with the requirement to disassemble and examine the bolting, along with tha inherent need to repeat all or portions of the associated pressure test and the potential impact on plant i
operations, far outweigh the increase in safety resulting from performance of this examination.
The objective of the ASME Code requirement is to detect degradation of the fastener that has resulted in leakage of the joint. The ASME Code is not attempting to address alignment and gasket problems associated with a leaking flange connection. The required examination method is VT-3, which is conducted to determine the general mechanical and structural condition of components and their supports by verifying parameters such as clearances, settings, and physical displacements; and to detect discontinuities and imperfections, such as loss of integrity at bolted or welded connections, loose or missing parts, debris, corrosion, wear, or erosion.
The ASME Code (1990 Addenda and later Editions) accepts a sample of bolts, with a provision for sample expansion, instead of a visual examination of all bolts after the detection of leakage. The current revision of the Code was published after due consideration of he acceptance standards for the number of degraded bolts that could be present before a significant safety problem would exist.
PECO Energy's proposal to perform a VT-1 examination instead of a VT-3 examination when bolting is removed and to apply Class 1 requirements for acceptance criteria, subsequent examinations, and additional examinations when evaluating leakage at bolted connections in Class 1,2, and 3 components meets or exceeds the requirements of Code Case N-566 and exceeds the requirements of the ASME Section XI Code. The examination method is superior to the ASME Section XI Code requirement.
Code Case NE., Corrective Action for Leakage identified at Bolted Connections, represents technically acceptab!e altemative rules to ASME Section XI Code requirements. The fact that this Code Case has not been endorsed in the Regulatory Guide in no way detracts from its technical adequacy since the major reason for its omission is the timing of its publication with respect to the most recent revision of the Regulatory Guide. That is, the subject Code Case is relatively recent and it is expected that it will be accepted in a subsequent revision of the Regulatory Guide.
Adoption of this altemative rule provides an acceptable level of quality and safety and does not compromise the adequacy of the LGS ASME Section XI Programs in meeting the intent of the ASME Code.
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Docket Nos. 50-352,50-353 Attachment March 11,1999 Page 12 of 13 Relief Reauest No. RR 23, Revision 1 6.
Request for Relief No. RR-23, Revision 1: ASME Code,Section XI, Examination Category C-H requires a VT-2 visual examination during hydrostatic tests of Class 2 systems performedin accordance with IWC-5222 near the end of the interval. IWA-5213 states that, for system hydrostatic tests ofinsulated systems, a 4-hour hold time is required after attaining the test pressure and
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temperature; a 10-minute hold time is required for non-insulated systems or components.
k Pursuant to 10CFR50.55(a)(a)(3), the licenses proposed an altemative to the hold time requirement of the Code and Code Case N-498-1 for the HPCIpump turbine and associated lines. The licensee stated:
The system pressure test describedin Code Case N-498-1 will be conducted as required, except that a 10 minute hold time will be used in lieu of the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hold time requirement. This 10 minute hold time i
willmatch the hold time which has been required for the previous Section XIISI Program pressure k
testing of this system.
The licensee's proposed 10-in, ute hold time before VT-2 visual examination i? an acceptable waiting
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period for non-insulated systems because examiners have direct view of the piping and components.
Forinsulated systems, an increased hold time is required to allow potential teaks to migrate through the insulation. A hold time of 10 minutes may not ensure the detection ofleakage in insulated components.
The staff determined that a hold time greater than 10 minutes should occurprior to the VT-2 visual examination ofinsulated portions of the subject system. The licensee stated that periodic functional tests, at operating pressure, are performed on the HPCI pump. During these tests, the operating pressure is maintained for approximately 90-minutes of pump run time. The VT-2 visual examination, with the system at operating pressure, could be performed in conjunction with the component functional test. This would increase the probability of detecting leakage, ifit is occurring, and provide reasonable assurance of operationalreadiness. This condition was stipulatedin the previous 10-year ISIinterval authorization of this request for relief for Unit 1. However, the licensee has not included the extended hold time (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> minimum) into its proposed attemative for the current ISIinterval for Units 1 and 2. Please respond to the staff's concerns described above.
Response
ASME Section XI Code Case, N-498-1 was approved for use at LGS, Unit 1, by NRC SER, dated June 29, 1995. Approval to include this Code Case in the LGS, Unit 2, ASME Code Bases is pending per this correspondence. Code Case 498-1 allows a system pressure test to be conducted on safety class 2 components as an altemative to the ten-year system hydrostatic test, required by the ASME Section XI Code, Examination Category C-H. The system pressure test altemative provided by the Code Case, however, requires a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hold time at test pressure, before performing the required visual examination, for components which are insulated. Since the Class 2, High Pressure Coolant injection (HPCI) Pump Turbine -
steam supply / exhaust lines, and associated drains, vents, and tube oil cooler suppfyloutlet lines components, identified previously in Figures RR-23-1, RR-23-2, RR-23-3 and RR-23-4, are lnsulated, a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hold time would be required for this test. Therefore, a reduction in the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hold time, for both LGS Units 1 and 2, is the requirement from which relief is being requested.
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- Docket Nos. 50-352,50-353 Attachment March 11,1909 Page 13 of 13 s.
As a part of the Emergency Core Cooling System (ECCS), the High Pressure Coolant injection (HPCI)
System is not required to operate during normal plant operation. This system is, however, periodically tested in accordance with other applicable requirements. These periodic tests are conducted to verify the operability of the applicable components. The functional test conducted for the HPCI Pump and associated turbine steam supply and exhaust system normally includes approximately 90 minutes of pump run time. In order to satisfy the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hold time requirement of Code Case N 498-1, the test would require a HPCI Pump run in excess of 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> (hold time plus examination time). Running the HPCI System functional test for this length of time is not practical, and represents an undue hardship on the facility, without a compensating increase in the level of quality and safety.
Operating the HPCI Pump for the period of time required to satisfy the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> time, would subject the facility to unnecessarily excessive heat loads. Control of these heat loads, would require the operation of additional i
safety related equipment, and challenge the Technical Specification limitations placed on the maximum j
allowable Suppression Pool water temperature.
Removal of the insulation from the subject components, in order to qualify for the 10 minute hold time allowed by the Code Case, would be aqually burdensome. The cost associated with insulation removal and reinstallation, including resource diversion, radiation exposure, and additional radwaste v'ould not be j
warranted.
PECO Energy proposes to perform the system pressure test described in Code Case N-498-1 as required, except that a minimum i hour hold time will be used in lieu of the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hold time requirement. This minimum i hour hold time will match the hold time for the pressure testing of this system which has been approved by the NRC for the current ISI Interval for LGS, Unit 1.
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