ML17313A900

SER Accepting Licensee Proposed Relief Requests 11 & 12 for Second 10-year Inservice Insp Interval for Palo Verde Nuclear Generating Station,Units 1,2 & 3

ML17313A900
Person / Time
Site:	Palo Verde
Issue date:	04/26/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML17313A899	List: ML17313A900
References
NUDOCS 9904280206
Download: ML17313A900 (7)

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&4001 SAFETY EVALUATIONBYTHE OFFICE OF NUCLEAR REACTOR REGULATION RELATEDTO INSERVICE INSPECTION RELIEF RE UESTS NOS. 11 AND 12 ARIZONAPUBLIC SERVICE COMPANY ET AL.

PALO VERDE NUCLEAR GENERATING STATION UNIT NOS.

1 2 AND3 DOCKET NOS. STN 50-528 STN 50-529 AND STN 50-530

1.0 INTRODUCTION

Title 10 of the Code of Federal Re ulations (10 CFR), Section 50:55a, requires that inservice inspection (ISI) of certain 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 Code (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).

In 10 CFR 50.55a(a)(3), it states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if(1) the proposed alternatives would provide an acceptable level of quality and safety or (2) 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 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for Palo Verde Nuclear Generating Station (PVNGS), Units 1, 2, and 3, for the second 10-year ISI interval is the 1989 Edition.

By letters dated April20 and 21, 1999, Arizona Public Service Company (the licensee) requested approval to use two alternatives to the requirements of Section XI to the ASME Code, pursuant to 10 CFR 50.55a(a)(3)(i).

Relief Request No. 11 requests approval to use an alternative to IWA-5242(a) of Section XI to the ASME Code, which requires that insulation be removed from pressure-retaining bolted connections during the pressure test of systems borated for reactivity control. The proposed alternative would-allow insulation removal and visual examination of the bolted connections to be done earlier in the refueling outage while the system is depressurized.

Relief Request No. 12 requests approval to use an altem'ative to IWA-5250(a) which requires that bolting be removed and visually inspected when leakage is detected at a bolted connection during

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I the conduct of the system pressure test. The proposed alternative would allow an evaluation of other factors concerning the leakage joint as a possible alternative to disassembly and visual examination of the bolting.

2.0

. EVALUATIONOF RELIEF RE UESTS 2.1 Relief Re uest No. 11 - Examination of Bolted Connections on Class 1 Borated S stems Used for Reactivi Control ASME Code,Section XI, IWA-5242(a), requires that insulation shall be removed from pressure-retaining bolted c'onnections for VT-2 visual examination in systems borated for the purpose of controlling reactivity. This examination is to be performed once every refueling outage at a test pressure not less than the nominal operation pressure associated with 100 percent rated reactor power.

Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee has proposed the following alternative to the Code requirement to remove insulation at bolted connections for VT-2 examination during system pressure testing (as stated):

PVNGS will perform a system pressure test and VT-2 examination each refueling outage without removal of insulation.

In addition PVNGS willremove insulation from the bolted connections, and perform a VT-2 visual examination each refueling outage but the connections willnot be required to be pressurized for this examination.

This alternative is consistent with Code Case N-533.

C The licensee's proposed alternative is equivalent to Code Case N-533, Alternative Requirements for VT-2 Visual Examinafj'on of Class 1 Insulated Pressure-Retaining Bolted Connections,Section XI, Division 1. The licensee's proposed alternative provides a thorough approach to ensuring the leak-tight integrity of systems borated for the purpose of controlling reactivity. First, the visual examination during the pressure test provides a means of detecting any significant leakage with the insulation in place.

Second, by removing the insulation each refueling outage, the licensee willbe able to detect minor leakage indicated by the presence of boric acid crystals or residue.

This two-phase approach provides an acceptable level of quality and safety for bolted connections in borated systems.

Therefore, the licensee's proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for use on Class 1 systems for the remainder of the second 10-year ISI interval.

2.2 Relief Re uest No. 12 - Examination of Code Class 1 2 and 3 Pressure-Retainin Bolted Connections ASME Code,Section XI, IWA-5250(a)(2), requires that ifleakage occurs at a bolted connection in ASME Section XI components, the bolting shall be removed, VT-3 examined for corrosion, and evaluated in accordance with IWA-3100. Pursuant to 10 CFR 50.55a(a)(3)(i),

the licensee proposed to use alternative requirements regarding corrective actions for leakage at bolted connections in lieu of the examination requirements defined in IWA-5250(a)(2). The licensee stated:

e PVNGS proposes the following alternative methodology to the requirements of IWA-5250(a), either the requirements of (a) or (b) below willbe met for leakage at bolted connections:

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It (a) The leakage shall be stopped, and the bolting and component material shall be evaluated forjoint integrity as described in (c) below.

(b) Ifthe leakage is not stopped, the joint shall be evaluated in accordance with IWB-3142.4 forjoint integrity. This evaluation shall include the considerations listed in (c) below.

(c) The evaluation for (a) and (b) above, is to determine the susceptibility of the bolting to corrosion and failure. This evaluation will, at a minimum, consider the following factors:

(1)

The number and service age of bolts, (2)

Bolt and component material, (3)

Corrosiveness of the process fluid, (4)

Leakage location and system function, (5)

Leakage history at connection or other system components, and (6)

Visual evidence of corrosion at connection (while the connection is assembled).

Ifthe evaluation of the variables above indicates the need for further,evaluation, then a bolt closest to the source of leakage shall be removed.

The bolt will receive a VT-1 examination and be evaluated and dispositioned in accordance with IWB-3517 of the ASME Code,Section XI. Ifthe removed bolting shows evidence of rejectable degradation, all remaining bolts shall be removed and receive a VT-1 examination in accordance with IWB-3140. Ifthe leakage is identified when the bolted connection is in service and the information in the engineering evaluation is supportive, the removal of the bolt for the VT-1 examination may be deferred until the next refueling outage..

In accordance with IWA-5250(a)(2), ifleakage occurs at a bolted connection, the bolting must 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 proposed evaluation willconsider, as a minimum, bolting materials, the corrosive nature of the process fluid, the leakage location and history, the service age of the bolting materials, visual evidence of corrosion at the assembled conhection and plant/industry studies of similar bolting materials in similar environments.

Based on the items included in the evaluation process, the staff determined that the evaluation proposed. by the licensee presents a sound engineering approach and provides an acceptable level of quality and safety.

In addition, ifthe initial evaluation indicates the need for a more detailed analysis, the bolt nearest to the source of leakage willbe removed, visually examined, and evaluated in accordance with IWB-3517. Therefore, the licensee's proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the remainder of the second 10-year ISI interval.

~ 3.0 CONCLUSION The staff has reviewed the licensee's submittal and concludes that the licensee's proposed alternatives willprovide an acceptable level of quality and safety.

Pursuant to 10 CFR 50.55a(a)(3)(i), both relief requests are authorized for the remainder of the second 10-year ISI interval.

Principal Contributor: Mel B. Fields Date: April26, 1999

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