ML16342E083
| ML16342E083 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/01/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML16342E082 | List: |
| References | |
| NUDOCS 9805080201 | |
| Download: ML16342E083 (34) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&0001 SAFETY EVAL ATION BYTHE OFFICE OF NUCLEAR REACTOR REGULATION SECOND TEN-YEAR INTERVALINSERVICE INSPECTION PROGRAM PLAN AND RE UESTS FOR RELIEF NOS. PRS-1 REVISION 1 PRS-1D PRS-1E AND PRS-1F PACIFIC GAS AND ELE TRIC COMPANY DIABL ANYON POWER PLANT NIT NOS.
1 AND 2 D
KET NOS.
0-27 AND 0- 23
1.0 INTRODUCTION
The Technical Specifications (TS) for Diablo Canyon Power Plant, Units 1 and 2, state that the inservice inspection of the American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel (B8PV) Code and applicable addenda as required by 10 CFR 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 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 difficultywithout 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 pre-service 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 ten-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) twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the Diablo Canyon Power Plant, Units 1 and 2 second ten-year inservice inspection (ISI) interval is the 1989 Edition.
Pursuant to 10 CFR 50.55a(g)(5), ifthe licensee 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 from the ASME Code requirement.
After evaluation of the 980508020i 980501 PDR ADQCK 05000275 P
determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, willnot endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result ifthe requirements were imposed.
By letter dated December 24, 1997, Pacific Gas and Electric Company, (licensee) submitted alternatives to the ASME,Section XI Code (Code) regarding its second 10-year interval ISI program plan Requests for Relief Nos. PRS-1 C, Revision 1, PRS-1D, PRS-1E, and PRS-1F, for Diablo Canyon Power Plant, Unit Nos.
1 and 2. The licensee provided additional information in its letter dated January 30, 1998. The licensee requested, that the staff review the alternatives required for its upcoming Unit 2 outage contained in Requests for Relief Nos.
PRS-1C, Revision 1, PRS-1D, PRS-1E, and PRS-1F.
2.0 EVALUATION The 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 inservice inspection (ISI) program plan Requests for Relief Nos. PRS-1C, Revision 1, PRS-1D, PRS-1E, and PRS-1F for Diablo Canyon Power Plant, Unit Nos.
1 and 2. Based on the results of the review, the staff adopts the contractor's conclusions and recommendations presented in the attached Technical Letter Report (TLR).
Re ue t f r Relief PRS-1C Rev1: The licensee has proposed in accordance with 10 CFR 50.55a(a)(3)(i), an alternative to the Code requirements to use Code Case N-533. Code Case N-533 allows for Class 1 pressure-retaining bolted connections to have a VT-2 visual examination during system pressure tests with the insulation in place.
The Code Case also allows for a direct visual examination with the insulation removed from the bolted connections during the subsequent refueling outage with the insulation removed and without pressurizing the system.
Both examinations are required once each refueling outage.
The Code requires the removal of all insulation from pressure-retaining bolted connnections in systems borated for the purpose of controlling reactivity when performing VT-2 visual examinations during system pressure tests.
The staff concluded that the use of Code Case N-533 provides an acceptable level of quality and safety for Class 1 Systems with bolted connections, borated for the purpose of controlling reactivity. Furthermore, the staff determined that significant leakage will be detected by the system leakage test with the insulation in place.
In addition, the staff concluded that by removing the insulation each refueling outage, the licensee willbe able to detect minor leakage by the presence of boric acid crystals or residue.
This two-phased approach provides an
'cceptable level of quality and safety for bolted connections in borated systems.
Therefore, the licensee's proposed alternative to use Code Case N-533 is authorized for bolted connections in ASME Class 1 components pursuant to 10 CFR 50.55a(a)(3)(i).
The use of Code Case N-533 is authorized for the second 10-year interval at Diablo Canyon, Unit Nos.
1 and 2, or until the Code Case is approved for general use by reference in Regulatory Guide 1.147. Afterthat time, the licensee may continue to use Code Case N-.533 with the limitations, ifany, listed in Regulatory Guide 1.147.
Re uest for Relief No PRS-1 D: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-533, Alternatj've Requirements for VT-2 Visual Examination of Class 1 Insulated Pressure-Retaining Bolted Connections, Section X/, Division 1, as an alternative to the Code requirement to remove insulation from Class 2 systems borated for the purpose of controlling reactivity for the performance of the system leakage test each period.
Code Case N-533 is only for Class 1 systems; however, the licensee proposed the use of Code Case N-533 for Class 2 systems with the frequencies of performance of the system leakage test each period versus each refueling outage for Class 1 systems.
The staff concluded that the licensee's proposed alternative for Class 2 systems is not an acceptable alternative, because insulation removal from Class 2 systems can take place seven years and cross over to the next period after the initial VT-2 examination was performed in the current period. Therefore, the licensee's proposed alternative to use Code Case N-533 for Class 2 systems is denied.
Re uest for Relief PRS-1E:
In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed an alternative to the requirements of IWA-5250(a)(2) for ASME Class 1, 2, and 3 systems and components.
The 1989 Edition of Section XI, IWA-5250(a)(2) requires that ifleakage occurs at a bolted connection, the bolting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.
In accordance with the Code, ifleakage occurs at a bolted connection, all bolting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.
In lieu of this requirement, the licensee has proposed to evaluate the bolting to determine its susceptibility to corrosion using a proposed evaluation process.
The licensee's proposed evaluation considers a number of parameters, including bolting materials, the potential for corrosion, and visual evidence of corrosion with the bolting in place.
Ifthe evaluation cannot confirm the integrity of the joint, the licensee has proposed to remove one'bolt nearest the leakage for VT-3 visual examination.
As a result, significant patterns of degradation willbe detected and an acceptable level of quality and safety is provided by the licensee's proposed alternative.
The staff has reviewed the licensee's submittal and concludes that the evaluation process proposed by the licensee provides a sound engineering approach.
Therefore, the licensee's proposed alternative contained in Request for Relief No. PRS-1E for Code Class 1, 2, and 3, systems and components is authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Re uest for Relief ¹PRS-1F:
In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-498-1, "Alternative Rules for 10-Year System Hydrostatic Testing for Class 1, 2, and 3 Systems" for Class 3 Systems,Section XI, Division 1, in lieu of Code requirements Table IWB-2500-1, Examination Category B-P, Table IWC-2500-1, Examination Category C-H, Table IWD-2500-1, Examination Category D-A, D-B, and D-C that requires a system hydrostatic test be. performed in accordance with IWA-5000 once each 10-year interval.
0 J
I The staff concluded that Code Case N-498-1 is an acceptable alternative for Class 3 systems and components for the Code required 10-year system hydrostatic testing.
Furthermore the staff concluded that the licensee's proposed alternative, to use Code Case N-498-1, for Class 3 systems and components provides an acceptable level of quality and safety. Therefore the licensee's proposed alternative to use Code Case N-498-1 contained in Request for Relief No. PRS-1 for Code Class 3 system and components is authorized pursuant to 10 CFR 50.55a(a)(3)(i).
The use of Code Case N498-1 is authorized for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, ifthe licensee intends to continue to implement this Code Case, the licensee should followall provisions in Code Case NP98-1 with limitations issued in Regulatory Guide 1.147, ifany.
3.0 CONCLUSION
The staff has reviewed the licensee's submittal and concludes that for Requests for Relief PRS-1 C, Revision 1, PRS-1E and PRS-1F, the licensee's proposed alternatives provide an acceptable level of quality and safety.
Therefore, the licensee's proposed alternatives contained in Requests for Relief PRS-1C, Revision 1, PRS-1E and PRS-1F are authorized pursuant to 10 CFR 50.55a(a)(3)(i).
For Request for Relief PRS-1D, the use of Code Case N-533 for Class 2 systems is not acceptable, because insulation removal from Class 2 systems can take place seven years and cross over to the next period after the initial VT-2 examination was performed in the current period. Therefore, the proposed alternative to use Code Case N-533 for Class 2 systems is denied.
The use of the above Code Cases are authorized for the current interval or until such time as the Code Cases are published in a future revision of Regulatory Guide 1.147. At that time, if the licensee intends to continue to implement this Code Case, the licensee should follow all provisions in the above Code Cases with limitations issued in Regulatory Guide 1.147, ifany.
Attachment:
Technical Letter Report Principle Contributor: T. McLellan Date:
IIay 1, 1998
TECHNICALLETTER REPORT SECOND 10-YEAR INTERYALINSERYICE INSPECTION RE UESTS FOR RELIEF PACIFIC GAS AND ELECTRIC COMPANY DIABLOCANYON POWER PLANT UNITS 1 AND 2 DOCKET NUMBERS 50-50-275 AND 50-323
1.0 INTRODUCTION
By letter dated December. 24, 1997, the licensee, Pacific Gas and Electric Company, requested expedited review of four requests for relief for use in the Unit 2 eighth refueling outage.
These requests were originally submitted as part of the second 10-year interval inservice inspection (ISI) program for Diablo Canyon, Units 1 and 2. The December 24, 1997, letter was a partial response to a Nuclear Regulatory Commission (NRC) request for additional information regarding the second 10-year interval ISI Program, submitted November 19, 1996. As a result of a January 28, 1998, conference call, the licensee submitted additional information by letter dated January 30, 1998. The Idaho National Engineering and Environmental Laboratory (INEEL) staff has evaluated the information provided by the licensee in support of these requests for relief in the following section.
2.0 EVALUATION The Code of record for the Diablo Canyon, Units 1 and 2, second 10-year ISI interval, which began January 1, 1996, for Unit 1 and June 1, 1996, for Unit 2, is the 1989 Edition of ASME,Section XI.
A)
Request for Relief OPRS-1C, R1, Use of Code Case ALTERNATIVERequirements for VT-2 Visual Examination ofClass 1 Insulated Pressure-Retaining Bolted Connections ATTACHMENT
0
Code Requirement:
For systems borated for the purpose of controlling reactivity, Subparagraph IWA-5242(a) requires removal of insulation from pressure-retaining bolted connections for VT-2 visual examination during system pressure testing.
Licensee's Proposed Alternative: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-533, Alternative Requirements for VT-2 Visual Examination of Class 1 Insulated Pressure-Retaining Bolted Connections,Section XI, Division 1. The licensee stated:
"PG8 E will implement Code Case N-533 in its entirety for the Class 1 systems.
PG8 E interprets the insulation removal requirement to require removal in the subsequent refueling outage following the examination."
Licensee's Basis for Proposed Alternative (as stated):
"Class 1 system pressure tests are performed in Mode 3 (Hot Standby) at full system pressure and temperature.
Removal of insulation under these conditions poses a significant hazard to plant personnel.
The additional handling of insulation ance support equipment during Mode 3 may also increase the potential for introducing loose material that could be transported to the containment sump during operation.
"Code Case N-533 allows Visual Examination VT-2 to be performed as follows for Class 1 systems:
1.
A system pressure test and VT-2 visual examination shall be performed each refueling outage without removal of insulation.
Each refueling outage the insulation shall be removed from the bolted connection, and a VT-2 visual examination shall be performed.
The connection is not required to be pressurized.
Any evidence of leakage shall be evaluated in accordance with IWA-5250.
~
"Pressure tests are conducted at nominal operating pressure in accordance with Code Cases N-498-1 and N-416-1. The mechanical joints in systems are not subjected to excessively high pressures formerly associated with hydrostatic tests, and thus, are not susceptible to leakage initiated from stress to the joint caused by the abnormally high hydrostatic test p.essures.
"Use of Code Case N-533 eliminates the hazard to personnel associated with removing insulation on systems at 550 degrees F. The proposed use of Code Case N-533 provides an equivalent level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i)."
Evaluation: The Code requires the removal of all insulation from pressure-retaining bolted connections in systems borated for the purpose of controlling reactivity when performing VT-2 visual examinations during system pressure tests.
As an alternative, the licensee has proposed to use Code Case N-533 which includes performance of a VT-2 visual examination with the insulation in place, and a direct visual examination with the insulation removed during the subsequent refueling outage.
The direct visual examination is performed without pressurizing the system, and both examinations are required once each refueling outage.
For Class 1 systems, the use of Code Case N-533 provides a reasonable approach for ensuring the teak-tight integrity of systems borated for the purpose of controlling reactivity. Any significant leakage willbe detected by the system leakage test with the insulation in place.
Secondly, by removing the insulation each refueling outage, the licensee will be able to detect minor leakage by the presence of boric acid crystals or residue.
This two-phased approach provides an acceptable level of quality and safety for bolted connections in borated systems.
Therefore, it is recommended that the licensee's proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
The use of Code Case N-533 should be authorized for the second 10-year interval at Diablo Canyon, Units 1 and 2, or until the Code Case is approved for general use by reference in Regulatory Guide 1.147. Afterthat time, the licensee may continue to use the Code Case with the limitations, ifany, listed in Regulatory Guide 1.147.
B.
Request for Relief ¹PRS-1D, Use of Code Case ALTERNATIVERequirements for
VT-2 Visual Examination of Class 1 Insulated Pressure-Retaining Bolted Connections, for Class 2 Systems Code Requirement:
For systems borated for the purpose of controlling reactivity, Subparagraph IWA.-5242(a) requires removal of insulation from pressure-retaining bolted connections for VT-2 visual examination during system pressure testing.
Licensee's Proposed Alternative: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-533, Alternative Requirements for VT-2 Visual Examination of Class 1 Insulated Pressure-Retaining Bolted Connections,Section XI, Division 1, as an alternative to the Code requirement to remove insulation from Class 2 systems borated for the purpose of controlling reactivity for the performance of the system leakage test each period. The licensee stated:
"For the identified portions of systems in containment:
1.
A system pressure test and VT-2 visual examination shall be performed at the normal Class 2 examination frequency without removal of insulation.
During the refueling outage immediately following the examination at pressure, the insulation shall be removed from the bolted connection, and a VT-2 visual examination shall be performed.
The connection is not required to be pressurized.
Any evidence of leakage shall be evaluated in accordance with IWA-5250.
"For the identified portions of,RHR and boric acid supply systems outside containment:
1.
A system pressure test and VT-2 visual examination shall be performed at the normal Class 2 examination frequency without removal of insulation.
For the RHR system, within '1 month after isolation and cooldown of the system after the pressure test, the insulation shall be removed from the bolted connection and a VT-2 visual examination shall be performed.
The connection is not required to be pressurized.
Any evidence of leakage shall
be evaluated in accordance with IWA-5250.
3.
For insulated bolted connections on the boric acid supply system from the boric acid tanks to the charging pumps suction, the test at pressure will be conducted at the beginning of a refueling outage.
During the same refueling outage of the test at pressure, when the system is removed from service, the insulation shall be removed from those bolted connections and a VT-2 visual examination conducted.
The'system is not required to be pressurized.
Any evidence of leakage shall be evaluated in accordance with IWA.-5250.
Licensee's Basis for Proposed Alternative (as stated):
"Certain Class 2 system pressure tests are performed in Mode 3 (Hot Standby) at full system pressure and temperature.
Removal of insulation under test conditions poses a significant thermal hazard to plant personnel.
"Inside the containment, the following portions of the systems are affected:
1.
- Normal and Alternate Charging Injection from the Regenerative Heat Exchanger to the Class 1 boundary.
2.
Pressurizer AuxiliarySpray from the Regenerative Heat Exchanger to the Class 1 boundary.
3.
Residual Heat Removal (RHR) Discharge to cold legs fro the containment penetration to the Class 1 boundary.
4.
Excess Letdown from valve 8167 to the containment penetration.
"Inside containment, the additional handling of insulation and support equipment during Mode 3 may also increase the potential for introducing loose material that could be transported to the containment sump during operation.
"Outside containment, the following portions of systems are affected:
1.
RHR suction and discharge piping.
2.
Boric acid supply system from the boric acid tanks to the charging pumps suction.
3.
Reactor coolant systems letdown from the containment penetration to valve 8152.
"RHR suction and discharge piping operates at elevated temperatures (approximately 350 degrees F. at the highest normal operating pressure) that pose a hazard to personnel who would be required to remove and install insulation during system operation including the pressure test. Also during this operation, the radiation levels associated with the piping are generally somewhat higher than with the system secured.
However, this piping remains in operation only fo'r a relatively short duration in Mode 3. Soon after the test at pressure is completed, the system is isolated and cooled down which would allow insulation to be removed for a VT-2 visual examination with the system depressurized.
This could be performed within 1 month of isolation and cooldown, rather than waiting until next refueling outage.
"The boric acid supply system from the boric acid tanks to the charging pumps suction is insulated and portions of the system are heat traced.
Removal of insulation of this portion of the system requires a clearance and the removal of the system from service.
This makes it impractical to test in service with the insulation removed.
"Pressure tests are conducted at nominal operating pressure in accordance with Code Cases N-498-1 and N-416-1. The mechanical joints in systems are not subjected to excessively high pressures formerly associated with hydrostatic tests, and thus, are not susceptible to leakage initiated from stress to the joint caused by the abnormally high hydrostatic test pressures.
"PG8E's proposed alternative uses Code Case N-533 for guidance in examination of these portions of the Class 2 systems with the following benefit:
B.
Eliminate the hazard to personnel associated with removing insulation from systems at high temperatures during pressurization.
Allowthe pressure test to be done with the system in service as required for the boric acid supply system from the boric acid tanks to the charging pumps suction.
"For the identified portions of systems inside containment, examination with insulation removed would be performed at the immediately subsequent refueling outage similarly to the treatment of Class 1 systems.
For the identified portions of systems outside containment, examination with insulation removed would be done reasonably soon (within 1 month) after the test at pressure was completed, without having to'wait through an operating cycle.
"The proposed use of Code Case N-533 provides an equivalent level of quality and
safety in accordance with 10 CFR 50.55a(a)(3)(i)."
Evaluation: The Code requires the removal of all insulation from pressure-retaining, bolted connections in systems borated for the purpose of controlling reactivity when performing VT-2 visual examinations during system pressure tests.
As an alternative to the Code requirements for Class 2 systems, the licensee has proposed Code Case N-533, which is currently under review by the NRC staff and has not yet been approved for use by incorporation into Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability.
The use of this Code Case for Class 2 systems with the frequencies proposed by the licensee is currently being considered by the NRC staff and has not yet been found to be an acceptable alternative.
Therefore, the licensee's proposed alternative to use Code Case N-533 for Class 2 systems should not be authorized at this time."
C.
Request for Relief CPRS-1E, Paragraph IWA-5250(a)(2), Corrective Measures for Bolted Connections Code Requirement: In the 1989 Edition of Section XI, IWA-5250(a)(2) requires that if leakage occurs at a bolted connection, the bolting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.
Licensee's Proposed Alternative: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed an alternative to the requirements of IWA-5250(a)(2), to remove at leaking bolted connections.
The licensee stated:
"When leakage is identified at bolted connections by Visual Examination VT-2, during system pressure testing, an evaluation will be performed to determine the
susceptibility of the bolting to corrosion and assess the potential for failure.
As a minimum, the following six factors will be considered when evaluating the acceptability of the bolting:
1.
2.
3.
5.
6.
Bolting materials Corrosiveness of process fluid Leakage location Leakage history at connection or other system components Visual evidence of corrosion at connection (connection assembled)
Service age of bolting materials "When the pressure test is performed on a system in service or required by the Technical Specifications to be operable, and the bolting is susceptible to corrosion, the evaluation shall address the connection's structural integrity until the next component/system outage of sufficient duration.
If the evaluation concludes that the system can perform its safety-related function, removal of the bolt closest to the leakage and a Visual, VT-3 examination of the bolt will be performed when the system or component is taken out-of-service for a sufficient duration for accomplishment of other system maintenance activities.
"For bolting that is susceptible to corrosion, and when the initial evaluation indicates that the connection cannot conclusively perform its safety function until the next component/system outage of sufficient duration, the bolt closest to the source of the leakage will be removed, receive a Visual, VT-3 examination, and be evaluated in accordance with IWA-3100(a)."
Licensee's Basis for Proposed Alternative (as stated):
"Removal of pressure retaining bolting at mechanical connections for Visual Examination VT-3 to detect
. orrosion in locations where leakage has been identified is not always the most discerning course of action to determine the acceptability of the bolting. The requirement to remove the bolting and look for corrosion does not allow the Owner to consider other factors which may indicate the acceptability of mechanical joint bolting "Other factors which should be considered when evaluating bolting acceptability, when leakage has been identified at a mechanical joint include but should not be limited to: joint bolting material, service age of joint bolting materials, location of leakage, history of leakage at the joint, evidence of corrosion with the joint assembled, and corrosiveness of process fluid.
8
"Performance of the pressure test while the system is in service may identify leakage at a bolted connectio'n that, upon evaluation, may conclude the integrity and pressure retaining ability is not challenged.
It would not be prudent to negatively impact a safety system's availability by removing the system from service to address a leak that does not impact the system's ability to perform its safety function.
"As an example, bolting is frequently replaced with new material in mechanical joints during plant outages.
When associated system precess piping is pressurized during plant startup, leakage may be identified at these joints. The root cause of this leakage is most often due to thermal expansion of the joint and subsequent seepage at the joint gasket.
Proper retorquing of the joint bolting, in most
- cases, stops the leakage.
Removal of the joint bolting to evaluate for corrosion would be unwarranted in this situation due to the new condition of the bolting.
ASME Code Interpretation XI-1-92-01 recognizes this situation as one in which the requirements of IWA-5250(a)(2) are not intended to apply.
"PGSE believes the following alternative provides an equivalent level of quality and safety in accordance with'10 CFR 50.55a(a)(3)(i)."
"The relief allows a systematic approach and sound engineering judgement for evaluation of bolting in joints exhibiting minor leakage.
The use of the outlined evaluation points will provide a thorough basis for the determination of continued use without bolting removal and inspection.
Additionally, if the initial evaluation indicates a need for a more in-depth examination, the bolt nearest the source of leakage will be removed, VT-3 examined and evaluated in accordance with IWA-3100(a). This will assure an equivalent level of quality and safety, and the integrity of the joint will be maintained."
gvValu ion: in accordance with the Code, if leakage occurs at a bolted connection, all bolting shall be removed, VT-3 visually examined for corrosion, and evaluated in accordance with IWA-3100.
In lieu of this requirement, the licensee has proposed to evaluate the bolting to determine its susceptibility to corrosion.
The INEEL staff has reviewed the licensee's submittal and believes that the evaluation process proposed by the licensee provides a sound engineering approach.
This evaluation considers a number of parameters, including bolting materials, the potential for corrosion, and visual evidence of corrosion with the bolting in
0 lp
place.
If the evaluation cannot confirm the integrity of the joint, the licensee has proposed to remove one bolt nearest the leakage for VT-3 visual examination.
As a result, significant patterns of degradation will be detected and an acceptable level of quality and safety will be provided.
Therefore, it is recommended that the licensee's proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
D.
R Year for R li f ¹PRS-1F U
f od C
N-498-1 Alernaiv Rule f r 0-H stai T
tin f rCI s1 2 and3S msf r lass3S ms Examination Category C-H, Table IWD-2500-1, Examination Category D-A, D-B, and D-C require a system hydrostatic test be performed in accordance with IWA-5000 once each 10-year interval.
Licen 'r ed Al em iv: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to use Code Case N-498-1, Alternative Rules for 10-Year System Hydrostatic Testing for Class 1, 2, and 3 Systems for Class 3 Systems,Section XI, Division 1, in lieu of the hydrostatic testing requirements of the Code.
The licensee stated:
"In lieu of the Code-required hydrostatic pressure inspection, PGRE proposes to perform the required visual examination (VT-2) at the same frequency currently required, except that the test would be performed at nominal system pressure in accordance with Code Case N-498-1."
icen
's B i f r Pro o ed Al ma iv (as stated):
"Code Case N-498 is generically approved and modifies the requirement for hydrostatic testing (reference Regulatory Guide 1.147, Revision 11, October 1994) for Code Class 1 and 2 systems.
10
E
"Code Case N-498-1 extends the application of pressure tests at nominal operating pressure to Code Class 3 systems, as well as Class 1 and 2 systems.
The elimination'of the elevated pressure test requirement is based on the potential to damage system components during hydrostatic tests, the increased safety risk to personnel performing the tests, and the fact that Code hydrostatic tests, are no more conducive to detection of leaks than tests at nominal operating pressure.
"The system hydrostatic test, as stipulated in the 1989 edition of Section XI, is not a test of structural integrity of the system.
Industry experience indicates that leaks are not being discovered as a result of hydrostatic test pressures causing a preexisting flaw to propagate through the wall; in most cases leaks are found when the system is at normal operating pressure.
Pressure tests for Code Class 3 systems are scheduled once each inspection period.
In addition, leaks may be identified during routine system walkdowns by plant operators.
"Although Section XI hydrostatic testing would not impair the structural integrity of the pressure boundary, it has the potential to initiate leak sites at mechanical connections (valve packing glands, flange joints), which are acceptable during the test but could continue to leak after return to service.
Such leaks may have minimal safety significance but may result in additional effort for containment, cleanup and disposal of the leakage.
Also the potential for spills, contamination, and longer personnel exposure time in radiation areas are not justified when compared to testing performed at nominal operating conditions."
~vl idio: The Code requires a system hydrostatic test once per interval in accordance with the requirements of IWA-5000 for Class 3 pressure-retaining systems.
In lieu of the Code-required hydrostatic testing, the licensee has requested authorization to use Code Case N-498-1, Alternative Rules for 10-Year
.System Hydrostatic Testing for Class 1, 2, and 3 Systems, dated May 11, 1994.
The system hydrostatic test, as stipulated in Section XI, is not a test of the structural integrity of the system but rather an enhanced leakage test.'ydrostatic testing only subjects the piping components to a small increase in S.H. Bush and R. R. Maccary, "Development ofIn-Service Inspection Safety Philosophy for U.S.A. Nuclear Power Plants, "AS ME, 1971 11
t
pressure over the design pressure; therefore, piping dead weight, thermal expansion, and seismic loads present far greater challenges to the structural integrity of'a system.
Consequently, the Section XI hydrostatic pressure test is primarily regarded as a means to enhance leak detection during the examination of components under pressure, rather than as a method to determine the structural integrity of the components.
In addition, the industry experience indicates that leaks are not being discovered as a result of hydrostatic test pressures causing a
preexisting flaw to propagate through the wall. In most cases leaks are being found when the system is at normal operating pressure.
Code Case N-498, Alternative Rules for 10-Year System Hydrostatic Testing for Class 1 and 2 Systems, was previously approved for general use on Class 1 and 2 systems in Regulatory Guide 1.147, Rev. 9.
For Class 3 systems, Revision N-498-1 specifies requirements identical to those for Class 2 components (for Class 1 and 2 systems, the alternative requirements in N-498-1 are unchanged from N-498).
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 VT-2 visual examination at nominal operating pressure and temperature in conjunction with a system leakage test performed in accordance with paragraph IWA-5000 of the 1992 Edition of Section XI.
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 are
'aused by different failure mechanisms.
Based on a review of Class 3 system failures requiring repair during the last 5 years,'he most common causes of Documented in Licensee Event Reports and the Nuclear Plant Reliability Data System databases.
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failure are erosion-corrosion (EC), microbiologically-induced corrosion (MIC),
and general corrosion.
In general, licensees have implemented programs for the prevention, detection, and evaluation of EC and MIC; therefore, Class 3 systems receive inspection commensurate with their functions and expected failure mechanisms.
Considering that Code Case N-498 was found to be an acceptable alternative for Class 1 and 2 systems, and that Class 3 systems receive inspections commensurate with their function and expected failure mechanisms, the licensee's proposed alternative, to use Code Case N-498-1, should provide an acceptable level of quality and safety.
Therefore it is recommended that the licensee's proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
The use of the Code Case should be authorized for the current interval or until such time as the Code Case is published in a future revision of Regulatory Guide 1.147. At that time, if the licensee intends to continue to implement this Code Case, the licensee should follow all provisions in Code Case N-498-1 with limitations issued in Regulatory Guide 1.147, if any.
The INEEL staff has reviewed the licensee's submittal and concludes that for Requests for Relief ¹PRS-1C, Revision 1, ¹PRS-1E and ¹PRS-1F, the licensee's proposed alternatives will provide an acceptable level of quality and safety.
Therefore, it is recommended that these proposed alternatives be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
For Request for Relief ¹PRS-1D, the use of Code Case N-533 for Class 2 systems is still being considered by the NRC staff and has not yet been found acceptable.
Therefore, the proposed alternative to use Code Case N-533 for Class 2 systems should not be authorized at this time.
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