ML20211J932

Safety Evaluation Concluding That Licensee Proposed Alternatives Provide Acceptable Level of Quality & Safety. Proposed Alternatives Authorized for Remainder of Third ten- Yr ISI Interval for Fort Calhoun Station,Unit 1

ML20211J932
Person / Time
Site:	Fort Calhoun
Issue date:	09/02/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20211J928	List: ML20211J923 ML20211J932
References
NUDOCS 9909070067
Download: ML20211J932 (4)

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, *4 UNITED STATES g- ]~ NUCLEAR REGULATORY COMMISSION g WASHINGTON D.C. 3000H001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUESTS FOR RELIEF ASSOCIATED WITH THIRD TEN-YEAR INSERVICE INSPECTION INTERVAL i OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION. UNIT NO.1 DOCKET NO, 50-285

1.0 INTRODUCTION

The Technical Specifications (TS) for Fort Calhoun Station, Unit 1, 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 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).

Section 50.55a(a)(3) of Title 10 of the Code of Federal Regulations states that attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed altematives 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- 1 service examination requirements, set forth in ASME Code,Section XI, " Rules for Inservice 1 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 Fort Calhoun Station, Unit 1, for the third ten-year inservice inspection (ISI) interval is the 1989 Edition.

Pursuant to 10 CFR 50.55a(g)(5), if the 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 determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose altemative requirements that are determined to be authorized by law, will not endanger life,  !

J 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 if the requirements were i imposed. j 9909070067 990902 PDR ADOCK 05000285 G PDR 1

2.0 EVALUATION OF RELIEF REQUESTS By letter dated March 1,1999, Omaha Public Power District (OPPD) submitted requests for relief related to the third inservice inspection (ISI) interval for Fort Calhoun Station Unit 1.

2.1 Reauest for Relief - ASME Class 1. 2. and 3 Bolted Connections in Systems Borated for the Purpose of CoiAvl lina Reactivity ASME Code,Section XI, IWA-5242(a) requires that insulation shall be removed from pressure-retaining bolted connections for VT-2 visual examination in systems borated for the purpose of controlling reactivity. 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. The licensee stated:

"For ASME Class 1 systems that are 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 augmented with a minimum 4-hour hold time at normal system operating pressure prior to the VT-2 visual examination to allow for leakage propagation from the insulation. Additionally, the insulation shall be removed from 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 Table IWB-2500, Category B-P (each refueling outage). The proposed attemative is consistent with the requirements of Code Case N-533 (Reference 7), which was approved for use at Fort Calhoun Station on September 18,1996 (Reference 8). These inspections shall be implemented through the application of the surveillance test program to assure they are performed within the prescribed time periods.

"For ASME Class 2 and 3 systems inside/outside of containment that are borated for the purpose of controlling reactivity, a system pressure test shall be performed in accordance with the frequency required in Table IWC-2500 or IWD-2500 as applicable, without the removal of insulation from the bolted connections. The requirements of system pressure tests shall be augmented with a 4-hour hold time at system normal operating pressure prior to the VT-2 examination to allow for leakage propagation from the insulation.

Additionally, the insulation shall be removed from insulated Class 2 and 3 bolted connections and a VT-2 examination shall be conducted at an increased frequency, with the system depressurized. VT-2 examinations on each component will be performed at a frequency of approximately 36-months to coincide 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 restrictive than the " periodic frequency" presctibed by ASME Section XI for Class 2 and 3 systems described in Table IWC-2500 or IWD-2500.

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"These inspections shall be implemented through the application of the surveillance test program to assure they are performed within the prescribed time period. Regardless of whether a component is scheduled for examination or not, any evidence of leakage from insulated or uninsulated components will result in evaluations for corrective measures in

, accordance with IWA-5250 (as modified for Fort Calhoun Station Unit No.1 by this submittal)."

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 the VT-2 visual examination with the insulation in place after a minimum 4-hour hold time. In addition, the insulation will be removed for direct visual examination according to the frequency requirements (each refueling outage prior to start-up) specified in IWB-2500-1, Category B-P for Class 1, and at approximately 36 month intervals (which coincide with plant refueling outages) not allowing the period between inspections on individual components to exceed 45 months for Class 2 and 3 components.

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

For Class 1 systems, the licensee's proposed attemative provides a thorough approach to ensuring the leak-tight integrity of systems borated for the purpose of controlling reactivity.

First, the 4-hour hold time allows any leakage to penetrate the insulation, thus provides a means of detecting any significant leakage with the insulation in place. Second, by removing the insulation each refueling outage for Class 1 components and at 36 month intervals for Class 2 and 3 components, the licensee will be 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 attemative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for use on Class 1,2 and 3 systems for the remainder of the third 10-year ISI interval.

2.2 Reouest for Relief - Class 1. 2. and 3 Pressure Retainino Bolted Connections 1 ASME Code,Section XI, IWA-5250(a)(2) requires that if leakage 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 attemative requirements regarding corrective actions for leakage at bolted connections in lieu of the examination requirements defined in IWA-5250(a)(2). The licensee stated:

"When leakage is identified at bolted connections by visual VT-2 examination, an evaluation will be performed to determine the susceptibility of the bolting to corrosion and assess the potential for failure. The evaluation will, at a minimum, consider the following factors:

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1. bolting materials,

2. corrosiveness of process fluid leaking,

3. leakage location,

4. leakage history at connection,

5. visual evidence of corrosion at connection (connection assembled),

6. industry studies and history of similar bolting in similar environment, and

7. condition and leakage history of adjacent components.

"If any of the above parameters indicates the need for further evaluation, the bolt closest to the source of leakage will be removed, receive a VT-1 examination, and be evaluated in accordance with IWA-3100(a). If the leakage is identified when the bolted connection is in service, removal of the bolt for VT-1 examination may be deferred to the next refueling outage if the evaluation determines this is acceptable. When the removed bolt shows evidence of degradation, all remaining bolting shall be removed, VT-1 examined, and evaluated in accordance with IWA-3100(a). The additional examinations of IWB-2430 and IWC-2430 will not be performed unless the need is established by the above evaluation."

In accordance with IWA-5250(a)(2), if leakage occurs at a bolted connection, the botting 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 will consider, as a minimum, botting materials, the corrosive nature of the process fluid, the leakage location and history, the service age of the botting materials, visual evidence of corrosion at the assembled connection 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, if the initial evaluation indicates the need for a more detailed analysis, the bolt nearest to the source of leakage will be removed, visually examined, and evaluated in accordance with IWA-3100(a). Therefore, the licensee's proposed attemative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the remainder of the third 10-year ISI interval.

3.0 CONCLUSION

The staff has reviewed the licensee's submittal and concludes that the licensee's proposed alternatives will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i) the proposed attematives are authorized for the remainder of the third 10-year ISI interval.

Principal Contributor: S. Bailey Date: September 2,1999 l