ML20204G383

Safety Evaluation Accepting Second 10-yr Interval ISI Request for Relief 12R-11

ML20204G383
Person / Time
Site:	Byron
Issue date:	03/19/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20204G367	List: ML20204G364 ML20204G383
References
NUDOCS 9903260137
Download: ML20204G383 (9)

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2 NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. enmaa nang .

r SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION RELIEF REQUEST COMMONWEALTH EDISON COMPANY -

BYRON STATION. UNITS 1 AND 2 DOCKET NOS. STN 50-454 AND STN 50-455

1.0 INTRODUCTION

Inservice inspection of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME 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(g)(6)(i).10 CFR 50.55a(a)(3) states that attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed attematives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. .

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the 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 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of the Section XI of the ASME Code incorporated by reference in the 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 appScable edition of Section XI of th* ASME Code for Byron Station, Units 1 and 2, is the 1989 Edition of Section XI of the ASME Cxle.

By letter dated July 29,1998, Commonwealth Edison Company (Comed, the licensee),

submitted to the NRC its attemative to the Code requirements in Relief Request 12R-11, 9903260137 990319 PDR ADOCK 05000454 Enclosure G PDR

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4 Revision 2, for the pressure testing of Class 1,2, and 3 insulated bolted connections specified in Section IWA-5242(a) for Byron Station, Units 1 and 2. The licensee's proposed attemative to conduct VT-2 examination without removing insulation at normal operating pressure and VT-2 examination with insulation removed and system depressurized, would provide an acceptable level of quality and safety. The NRC staff has reviewed and evaluated the licensee's proposed alternative and the supporting information, pursuant to 10 CFR 50.55a(a)(3)(i) for Byron Station, Units 1 and 2.

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 request for attemative to the Code-requirements during the second 10-year inservice inspection interval. Based on the results of the review, the staff adopts the contractor's conclusions and recommendations presented in the attached Technical Letter Report (TLR).

Request for Relief 12R-11 (Revision 2): This request for relief involves the use of Attemative Requirements to Visual Examination, VT-2, of Class 1,2, and 3 Insulated Pressure Retaining Bolted Connections,Section XI, Division 1, under Paragraph IWA-5242(a).

Section IWA-5242(a), insulated Components, requires removal of all insulation from pressure retaining bolted connections in systems borated for the purpose of controliing reactivity.when performing VT-2 visual examinations during system pressure tests. In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to conduct the Ccde-required VT-2 examination without removal of the insulation, augmented by a minimum 4-hour hold time prior to examination to allow for leakage propagation, if any. In addition, the licensee proposes to remove the insulation and perform a VT-2 examination while the system is depressurized to determine if leakage had occurred at bolted connections by noting evidence of residues at the connection.

The examination frequencies for class 2 and 3 bolted connections will also be increased to 36 months, which coincides with refueling outages, that exceeds the current Code-required .

examination frequencies. If there is leakage at the connection or evidence of leakage at the connection, the connection shall be evaluated in accordance with IWA-5250, as modified for Byron Station in the staff safety evaluation for Relief Request IR-12, dated July 22,1996.

The proposed attemative by the licensee is similar to Code Case N-533, which has been previously authonzed by the staff on an individual basis and is currently under consideration for incorporation into Regulatory Guide 1.147, " Inservice inspection Code Case Acceptability."

Code Case N-533 has been determined previously to provide a reasonable approach for ensuring the leak tight integrity of insulated bolted connections in Class 1 systems borated for the purpose of controlling reactivity. The licensee's proposed attemative to conduct the VT-E examination with the insulation in place, after a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> hold time at normal system operating pressure, should provide a means of detecting significant leakage. In addition, the removal of insulation for a visual exam each refueling outage for Class i bolted connections, and at approximately 36 month intervals for Class 2 and 3 bolted connections, should provide for detection of minor leakage by noting the presence of residues.

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This approach meets the intent of IWA-5242(a) to assure that structural integrity of bolted connections in borated systems will be maintained. Therefore, the staff concludes that the proposed attemative provides an acceptable level of quality and safety.

3.0 CONCLUSION

The staff has completed its review of the information provided by the licensee and concludes that for request for relief 12R-11, Revision 2, the proposed altemative will provide an acceptable level of quality and safety. Therefore, the licensee's proposed alternative in request for relief 12R-11, Revision 2, is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the current interval.

Attachment:

Technical Letter Report Principal Contributor: G. Hatchett Dated: March 19,1999

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TECHNICAL LETTER REPORT l

ON SECOND 10-YEAR INTERVAL INSERVICE INSPECTION RELIEF REQUEST 12R-11. REVISION 2 EDB l COMMONWEALTH EDISON COMPANY l

BYRON NUCLEAR POWER STATION. UNITS 1 AND 2 DOCKET NUMBERS: 50 454 and 50-455

1. INTRODUCTION By letter dated July 29,1998, the licensee, Commonwealth Edison Company, submitted Relief Request 12R-11, Revision 2, seeking relief from the requirements of the ASME Code,Section XI, for the Byron Nuclear Power Station, Units 1 and 2, second 10-year inservice inspection (ISI) interval. The Idaho National Engineering and Environmental Laboratory (INEEL) staff's evaluation of the subject request for relief is in the following section.

2. EVALUATION The information provided by Commonwealth Edison Company in support of the request for relief from Code requirements has been evaluated and the basis for disposition is documented below. The Code of record for the Byron Nuclear Power Station, Units 1 and 2, second 10-year ISI interval, which began September 1,1996, for Unit 1, and August 16,1998, for Unit 2, is the 1989 Edition of Section XI of the ASME Boiler and Pressure Vessel Code.

Reauest for Relief No.12R-11 (Revision 2). Paraaraoh IWA-5242(al VT-2 Visual Examination of Insulated Bolted Comoonents Code Reauirement: IWA-5242(a) requires that insulation be removed from pressure-retaining bolted connections for VT-2 visual examination in systems borated for the purpose of controlling reactivity.

ATTACHMENT

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Licensee's Prooosed Altemative: Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee has 1 l proposed the following attemative to the Code requirement to remove insulation at l bolted connections for W-2 examination during system pressure testing.

The licensee stated:

"For ASME Class 1 systems borated for the purpose of controlling reactivity, a system inservice leakage test shall be performed in accordance with the frequency required in Table IWB-2500 without the removal of insulation from the bolted connections. The requirements for inservice leak tests shall be l

augmented with a minimum 4-hour hold time at system normal operating i pressure prior to the VT-2 visual examination to allow for leakage propagation from the insulation. Additionally, the insulation shall be removed f om insulated Class 1 bolted connections and a VT-2 examination shall be conducted, with the system depressurized. The frequency for these depressurized VT-2 inspections  !

shall be in accordance with the system examination frequencies specified in Tables IWB-2500, Category B-P (each refueling outage). The proposed altemative is consistent with the requirements of Code Case N-533. These inspections shall be implemented through the application of the Byron Station predefined surveillance program to assure they are performed within the prescribed time periods.

"For ASME Class 2 and 3 systems borated for me purpose of controlling reactivity, a system pressure test shall be performed in accordance with the frequency required in Tables IWC-2500 or IWD-2500, as applicable, without the removal of insulation from the bolted connections. The requirements for system pressure tests shall be augmented with a minimum 4-hour hold time at system normal operating pressure prior to the W-2 visual examination to allow for leakage propagation from the insulation. Additionally, the insulation shall be removed from individual insulated Class 2 and 3 bolted connections and a W-2 examination shall be conducted, with the system depressurized at an increased frequency. W-2 examinations on each component will be performed on approximately 36-month frequency, which coincides with plant refueling outages, not allowing the period between inspections on individual components to exceed 45 months. This increased frequency for individual components is more l restrictive than the ' Periodic Frequency' prescribed by ASME Section XI for Class 2 and 3 systems described in Tables IWC-2500 or IWD-2500. These inspections shall be implemented through the application of the Byron Station predefined surveillance program (EWCS) to assure they are performed within the prescribed time periods.

"Regardless of whether a component is scheduled for examination or not, any evidence of leakage, either while insulated or while deinsulated, will result in evaluations for corrective measures in accordance with IWA-5250 g modified for Byron Station by approved Relief Request 12R-12')."

i 1 Evaluated in NRC Safety Evaluation Report dated July 22,1996.

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Licensee's Basis for Prooosed Attemative (as stated):

l " Pursuant to 10 CFR 50.55a(a)(3)(i), relief is requested on the basis that the l proposed altemative would provide an acceptable level of quality and safety.

Specifically, relief is requested from the requirement to remove insulation at bolted connections for VT-2 examination coincident with system pressure testing l at normal operating pressure.

"The following Byron Station material control and procedure control programa, in conjunction with the Proposed Altemate Provisions, provide an acceptable level of quality and safety for bolted connections in systems borated for the purpose of controlling reactivity.

- In response to NRC Generic Letter 88-05, Byron Station has established a program for Engineering to inspect all botic' acid leaks discovered in the containment building and to evaluate the impact of those leaks on carbon steel or low alloy steel components. Any evidence of leakage, including dry boric acid crystals or residue, is inspected and evaluated regardless of ASME Class, location or whether the leak was discovered at power or during an outage, lasues such as the following are considered in the inspection and evaluation:

1) " Evidence of corrosion or motal degradation,

2) Effect the leak may have or the pressure boundary,

3) Possibility of boric acid traveling along the inside of insulation on piping, and

4) Possibility of dripping or spraying on other components. Based on this evaluation, Byron Engineering initiates appropriate cormctive actions to prevent recurrence of the leak and to repair, if necessary, any degraded materials or components.

"These evaluations ensure issues related to leakage on borated systems are addressed, including corrective actions necessary to eliminate the source of leakage.

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"The ASME Section XI Code,1989 Edition, Tables IWC 2500-1 and IWD 2500-1, presently prescribe the performance of ASME Class 2 and 3 pressure tests (visual, VT-2) on a frequency of once per ISI inspection period. Byron Station maintains a work control program (Electronic Work

. Control System-EWCS) that controls the implementation of examinations to prescribed time limits. Using the EWCS system, predefines will be assigned to examinations of borated system bolted connections at a 36 month frequency. The EWCS predefines provide a level of quality and safety that exceeds that of the ASME Section Code for ASME Class 2 and 3 bolted connections interval since the examinations will be completed on a more consistent frequency.

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4 "The ASME Section XI Code,1989 Edition, Table IWB 2500-1, presently prescribes the performance of ASME Class 1 pressure tests (visual, VT-2) on a frequency of once per ISI refuel cycle. Byron Station will perform the examination of borated system bolted connections at this frequency, thereby maintaining a consistent level of quality and safety as that prescribed by the l ASME Section XI Code.

l "The following information is not directly related to the basis for relief, however it represents hardship with performing the VT-2 examinations of borated system bolted connections coincident the systems at normal operating pressure. The issues are provided with this relief request as additional supporting information.

" Code Class 1,2 and 3 systems borated for the purpose of controlling i reactivity are extensive and large systems covering many areas and elevations. Scaffolding is required to access many of the bolted connections.

In addition, many of the bolted connections are located in difficult to access j areas and in medium to high-level radiation areas. Insulation removal '

l combined with scaffolding requirements will increase refuel outage duration, l financial costs, personnel exposure, and generation of radwaste associated

! with performance of VT-2 examinations. i "The VT-2 examinations of Class 1 systems, primarily the Reactor Coolant System (RCS) piping and component that are located inside containment, are performed at plant Mode 3. As required by IWB-5221, the RCS is at a normal operating pressure of 2235 psig. At Mode 3, the RCS temperature is approximately 557 'F. A significant portion of the Class 2 and 3 piping systems is also located in the containment and is VT-2 examined coincident with the Class 1 piping systems at plant Mode 3. Removal / reinstallation of insulation for Class 1,2, and 3 systems poses significant radiological considerations.

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" Performance of VT-2 examination, removal / reinstallation of insulation, and assembly / disassembly of scaffolding at bolted connectior.s under these operating conditions also present significant personnel safety considerations.

At Byron Station, the Class 1 VT-2 examination, coincident with Class 2 and 3 examinations, is a refuel outage critical path activity with duration in the Byron refuel outage schedule of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The activities associated with erecting scaffold to all of the bolted connection components and inspecting at operating pressure can add 4 to 5 days to this critical path activity.

l Therefore, in addition to the personnel safety and radiological considerations, insulation removal / installation and scaffolding assembly / disassembly will have considerable impact on the refuel outage duration and subsequent return to service of the unit."

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5 Evaluation: The Code requires the removal of allinsulation 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 attemative, the licensee has proposed to perform a system pressure test and associated VT-2 visual examination without removal of insulation from bolted connections on Class 1, 2, and 3 systems. The system pressure tests will be augmented with a minimum 4-hour hold time prior to the VT-2 visual examination. The frequency of examinations will be in accordance with the requirements in Table IWB-2500-1 for Class 1 systems (each refueling outage) and Tables IWC-2500-1 and IWD-2500-2 for Class 2 and 3 systems (each period). In addition, with the systems depressurized, insulation will be removed from the bolted connections for direct visual examination each refueling outage for Class 1 systems, and at approximately 36 month intervals (which coincide with plant refueling outages), but not exceeding 45 months for any component, for Class 2 and 3 systems.

The licensee's proposed attemative is essentially equivalent to Code Case N-533, Attemative Requirements for VT-2 Visual Examination of Class 1 Insulated Pressure-Retaining Bolted Connections,Section XI, DMsion 1, except the proposed altemative was extended to address Code Class 2 and 3 bolted connections. Code Case N-533 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.

For Class 1,2, and 3 systems, the licensee's proposed attemative provides a thorough 1

approach to ensuring the leak-tight integrity of systems borated for the purpose of  !

controlling reactivity. First, the 4-hour hold time should allow potential leakage to penetrate the insulation, thus providing a means of detecting significant leakage with the l insulation in place. Further, by subsequently removing the insulation each refueling outage for Class 1 bolted connections, and at approximately 36 month intervals (but not greater than 45 months) for Class 2 and 3 bolted connections, the licensee will be able to

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detect minor leakage indicated by the presence of boric acid residue. Therefore, it is j concluded that this two-phased approach will provide an acceptable level of qestity and safety for bolted connections in borated systems.

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3. CONCLU.31QN The INEEL staff has reviewed the licensee's submittal and concludes that for Request for Relief No.12R-11, Revision 2, the licensee's proposed alternative will provide an acceptable level of quality and safety. Therefore, it is recommended that this proposed alternative be authorized for the second interval pursuant to 10 CFR 50.55a(a)(3)(i). l l

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